Patent Publication Number: US-2023157914-A1

Title: Patient Transport Apparatus With Throttle Assembly Damping

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The subject patent application claims priority to, and all the benefits of, U.S. Provisional Patent Application No. 63/282,256, filed on Nov. 23, 2021, the entire contents of which are incorporated by reference herein. 
    
    
     BACKGROUND 
     Patient transport systems facilitate care of patients in a health care setting. Patient transport systems comprise patient transport apparatuses such as, for example, hospital beds, stretchers, cots, tables, wheelchairs, and chairs, to move patients between locations. A conventional patient transport apparatus comprises a base, a patient support surface, and several support wheels, such as four swiveling caster wheels. Often, the patient transport apparatus has one or more non-swiveling auxiliary wheels, in addition to the four caster wheels. The auxiliary wheel, by virtue of its non-swiveling nature, is employed to help control movement of the patient transport apparatus over a floor surface in certain situations. 
     When a caregiver wishes to use the auxiliary wheel to help control movement of the patient transport apparatus, such as down long hallways or around corners, the auxiliary wheel may be driven by a wheel drive system such that the auxiliary wheel rotates and the patient transport apparatus moves without the caregiver exerting an external force on the patient transport apparatus in a desired direction. In many cases, it is desirable for the auxiliary wheel to be driven at slower speeds in congested areas. 
     In order to operate the auxiliary wheel or similar drive systems utilized in connection with patient transport apparatuses, one or more user interfaces, controls, and the like are generally positioned for caregiver engagement to modulate the velocity of the patient transport apparatus. Certain types of user interfaces or controls for modulating velocity may be operated based on changes in positioning of one or more of the caregiver&#39;s hands, such with a finger or thumb-actuated rotatable throttle. In some instances, the range of motion of the user interface or control may be relatively small and can be made quickly, while corresponding changes in velocity of the patient transport apparatus generally take longer to realized. This lack of an immediate response can result in difficulty for the caregiver while attempting to achieve a preferred velocity, and may lead to the caregiver experiencing disruptive acceleration and/or deceleration. 
     A patient transport apparatus designed to overcome one or more of the aforementioned challenges is desired. 
     SUMMARY 
     The present disclosure provides a patient transport apparatus including support structure, a wheel coupled to the support structure to influence motion of the patient transport apparatus over a floor surface, and a wheel drive system coupled to the wheel to rotate the wheel relative to the support structure. A throttle assembly is arranged for engagement by a user and is operably coupled to the wheel drive system to enable the user to modulate propulsion of the patient transport apparatus between a forward direction and a rearward direction. The throttle assembly includes a handle configured to be gripped by the user, and a throttle arranged for user-selected rotation relative to the handle about a central axis between a maximum forward throttle position and a maximum backward throttle position. A throttle biasing element is provided to urge the throttle toward a neutral throttle position defined between the maximum forward throttle position and the maximum backward throttle position. A damper assembly is interposed between the throttle and the handle, and is arranged to provide torque resisting rotation of the throttle as the throttle rotates relative to the handle. 
     The present disclosure also provides a patient transport apparatus including a support structure, a wheel coupled to the support structure to influence motion of the patient transport apparatus over a floor surface, and a wheel drive system coupled to the wheel to rotate the wheel relative to the support structure. A throttle assembly is arranged for engagement by a user and is operably coupled to the wheel drive system to enable the user to modulate propulsion of the patient transport apparatus between a forward direction and a rearward direction. The throttle assembly includes a handle configured to be gripped by the user, and a throttle arranged for user-selected rotation relative to the handle about a central axis between a maximum forward throttle position and a maximum backward throttle position. A throttle biasing element is provided to urge the throttle toward a neutral throttle position defined between the maximum forward throttle position and the maximum backward throttle position. A throttle sensor is arranged for sensing movement the throttle as the throttle rotates relative to the handle. A damper assembly is interposed between the throttle and the handle, and includes a damper body defining a damper chamber at least partially filled with a working fluid, a damper divider supported for movement relative to the damper body and arranged to displace the working fluid, and a damper adjuster to adjust a viscosity of the working fluid. A controller in communication with the wheel drive system, the throttle sensor, and the damper assembly is configured to determine a resistance parameter based on sensed movement of the throttle relative to the handle, and to drive the damper adjuster based on the resistance parameter to provide torque resisting rotation of the throttle relative to the handle based on corresponding changes in the viscosity of the working fluid. 
     The present disclosure also provides a patient transport apparatus including a support structure, a wheel coupled to the support structure to influence motion of the patient transport apparatus over a floor surface, and a wheel drive system coupled to the wheel to rotate the wheel relative to the support structure. A throttle assembly is arranged for engagement by a user and is operably coupled to the wheel drive system to enable the user to modulate propulsion of the patient transport apparatus between a forward direction and a rearward direction. The throttle assembly includes a handle configured to be gripped by the user, and a throttle arranged for user-selected rotation relative to the handle about a central axis between a maximum forward throttle position and a maximum backward throttle position. A throttle biasing element is provided to urge the throttle toward a neutral throttle position defined between the maximum forward throttle position and the maximum backward throttle position. A throttle sensor is arranged for sensing movement the throttle as the throttle rotates relative to the handle. A damper assembly is interposed between the throttle and the handle, and includes a damper body, a damper divider supported for movement relative to the damper body, and a damper adjuster to adjust rotational resistance between the damper body and the damper divider. A controller in communication with the wheel drive system, the throttle sensor, and the damper assembly is configured to determine a resistance parameter based on sensed movement of the throttle relative to the handle, and to drive the damper adjuster based on the resistance parameter to provide torque resisting rotation of the throttle relative to the handle based on corresponding changes in rotational resistance between the damper body and the damper divider. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a patient transport apparatus according to one version of the present disclosure. 
         FIG.  2    is a perspective view of an auxiliary wheel assembly of the patient transport apparatus coupled to a base of the patient transport apparatus. 
         FIG.  3    is a perspective view of the auxiliary wheel assembly comprising an auxiliary wheel and a lift actuator. 
         FIG.  4    is a plan view of the auxiliary wheel assembly comprising the auxiliary wheel and the lift actuator. 
         FIG.  5 A  is an elevational view of the auxiliary wheel in a retracted position. 
         FIG.  5 B  is an elevational view of the auxiliary wheel in an intermediate position. 
         FIG.  5 C  is an elevational view of the auxiliary wheel in a deployed position. 
         FIG.  6 A  is a perspective view of a handle and a throttle assembly of the patient transport apparatus. 
         FIG.  6 B  is another perspective view of the handle and the throttle assembly of the patient transport apparatus. 
         FIG.  7    is a plan view of the handle and the throttle assembly of the patient transport apparatus. 
         FIG.  8 A  is an elevational view of a first position of a throttle of the throttle assembly relative to the handle. 
         FIG.  8 B  is an elevational view of a second position of the throttle relative to the handle. 
         FIG.  8 C  is an elevational view of a third position of the throttle relative to the handle. 
         FIG.  8 D  is another elevational view of the first position of the throttle relative to the handle. 
         FIG.  8 E  is an elevational view of a fourth position of the throttle relative to the handle. 
         FIG.  8 F  is an elevational view of a fifth position of the throttle relative to the handle. 
         FIG.  9 A  is a graph of a first speed mode. 
         FIG.  9 B  is a graph of a second speed mode. 
         FIG.  10    is a schematic view of a control system of the patient support apparatus. 
         FIG.  11    is an elevational view of an electrical cable coupled to the base of the patient transport apparatus. 
         FIG.  12    is a partial perspective view of another version of the handle and the throttle assembly of the patient transport apparatus, shown comprising a status indicator operating in a first output state. 
         FIG.  13    is a partially-exploded perspective view of portions of the handle and the throttle assembly of  FIG.  12   . 
         FIG.  14    is another partially-exploded perspective view of the portions of the handle and the throttle assembly of  FIG.  12   . 
         FIG.  15    is a broken, longitudinal sectional view of the portions of the handle and the throttle assembly of  FIGS.  12 - 14   . 
         FIG.  16 A  is a transverse sectional view of the throttle assembly and the handle taken as indicated by line  16 - 16  in  FIG.  15   , depicting the throttle in the first position relative to the handle. 
         FIG.  16 B  is another transverse sectional view of the throttle assembly and the handle taken as indicated by line  16 - 16  in  FIG.  15   , depicting the throttle in the third position relative to the handle. 
         FIG.  16 C  is another transverse sectional view of the throttle assembly and the handle taken as indicated by line  16 - 16  in  FIG.  15   , depicting the throttle in the fifth position relative to the handle. 
         FIG.  17    is a partially sectioned perspective view of a damper assembly of the throttle assembly of  FIG.  12   . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG.  1   , a patient transport system comprising a patient transport apparatus  20  is shown for supporting a patient in a health care setting. The patient transport apparatus  20  illustrated in  FIG.  1    comprises a hospital bed. In other versions, however, the patient transport apparatus  20  may comprise a stretcher, a cot, a table, a wheelchair, and a chair, or similar apparatus, utilized in the care of a patient to transport the patient between locations. 
     A support structure  22  provides support for the patient. The support structure  22  illustrated in  FIG.  1    comprises a base  24  and an intermediate frame  26 . The base  24  defines a longitudinal axis  28  from a head end to a foot end. The intermediate frame  26  is spaced above the base  24 . The support structure  22  also comprises a patient support deck  30  disposed on the intermediate frame  26 . The patient support deck  30  comprises several sections, some of which articulate (e.g., pivot) relative to the intermediate frame  26 , such as a fowler section, a seat section, a thigh section, and a foot section. The patient support deck  30  provides a patient support surface  32  upon which the patient is supported. 
     In certain versions, such as is depicted in  FIG.  1   , the patient transport apparatus  20  further comprises a lift assembly, generally indicated at  37 , which operates to lift and lower a support frame  36  relative to the base  24 . The lift assembly  37  is configured to move the support frame  36  between a plurality of vertical configurations relative to the base  24  (e.g., between a minimum height and a maximum height, or to any desired position in between). To this end, the lift assembly  37  comprises one or more bed lift actuators  37   a  which are arranged to facilitate movement of the support frame  36  with respect to the base  24 . The bed lift actuators  37   a  may be realized as linear actuators, rotary actuators, or other types of actuators, and may be electrically operated, hydraulic, electro-hydraulic, or the like. It is contemplated that, in some versions, separate lift actuators could be disposed to facilitate independently lifting the head and foot ends of the support frame  36  and, in other versions, only one lift actuator may be employed, (e.g., to raise only one end of the support frame  36 ). The construction of the lift assembly  37  and/or the bed lift actuators  37   a  may take on any known or conventional design, and is not limited to that specifically illustrated. One exemplary lift assembly that can be utilized on the patient transport apparatus  20  is described in U.S. Patent Application Publication No. 2016/0302985, entitled “Patient Support Lift Assembly”, which is hereby incorporated herein by reference in its entirety. 
     A mattress, although not shown, may be disposed on the patient support deck  30 . The mattress comprises a secondary patient support surface upon which the patient is supported. The base  24 , intermediate frame  26 , patient support deck  30 , and patient support surface  32  each have a head end and a foot end corresponding to designated placement of the patient&#39;s head and feet on the patient transport apparatus  20 . The construction of the support structure  22  may take on any known or conventional design, and is not limited to that specifically set forth above. In addition, the mattress may be omitted in certain versions, such that the patient rests directly on the patient support surface  32 . 
     Side rails  38 ,  40 ,  42 ,  44  are supported by the base  24 . A first side rail  38  is positioned at a right head end of the intermediate frame  26 . A second side rail  40  is positioned at a right foot end of the intermediate frame  26 . A third side rail  42  is positioned at a left head end of the intermediate frame  26 . A fourth side rail  44  is positioned at a left foot end of the intermediate frame  26 . If the patient transport apparatus  20  is a stretcher, there may be fewer side rails. The side rails  38 ,  40 ,  42 ,  44  are movable between a raised position in which they block ingress and egress into and out of the patient transport apparatus  20  and a lowered position in which they are not an obstacle to such ingress and egress. The side rails  38 ,  40 ,  42 ,  44  may also be movable to one or more intermediate positions between the raised position and the lowered position. In still other configurations, the patient transport apparatus  20  may not comprise any side rails. 
     A headboard  46  and a footboard  48  are coupled to the intermediate frame  26 . In other versions, when the headboard  46  and footboard  48  are provided, the headboard  46  and footboard  48  may be coupled to other locations on the patient transport apparatus  20 , such as the base  24 . In still other versions, the patient transport apparatus  20  does not comprise the headboard  46  and/or the footboard  48 . 
     User interfaces  50 , such as handles, are shown integrated into the footboard  48  and side rails  38 ,  40 ,  42 ,  44  to facilitate movement of the patient transport apparatus  20  over floor surfaces. Additional user interfaces  50  may be integrated into the headboard  46  and/or other components of the patient transport apparatus  20 . The user interfaces  50  are graspable by the user to manipulate the patient transport apparatus  20  for movement. 
     Other forms of the user interface  50  are also contemplated. The user interface may simply be a surface on the patient transport apparatus  20  upon which the user logically applies force to cause movement of the patient transport apparatus  20  in one or more directions, also referred to as a push location. This may comprise one or more surfaces on the intermediate frame  26  or base  24 . This could also comprise one or more surfaces on or adjacent to the headboard  46 , footboard  48 , and/or side rails  38 ,  40 ,  42 ,  44 . 
     In the version shown in  FIG.  1   , one set of user interfaces  50  comprises a first handle  52  and a second handle  54 . The first and second handles  52 ,  54  are coupled to the intermediate frame  26  proximal to the head end of the intermediate frame  26  and on opposite sides of the intermediate frame  26  so that the user may grasp the first handle  52  with one hand and the second handle  54  with the other. As is described in greater detail below in connection with  FIGS.  12 - 16 C , in some versions the first handle  52  comprises an inner support  53  defining a central axis C, and handle body  55  configured to be gripped by the user. In other versions, the first and second handles  52 ,  54  are coupled to the headboard  46 . In still other versions the first and second handles  52 ,  54  are coupled to another location permitting the user to grasp the first and second handle  52 ,  54 . As shown in  FIG.  1   , one or more of the user interfaces (e.g., the first and second handles  52 ,  54 ) may be arranged for movement relative to the intermediate frame  26 , or another part of the patient transport apparatus  20 , between a use position PU arranged for engagement by the user, and a stow position PS (depicted in phantom), with movement between the use position PU and the stow position PS being facilitated such as by a hinged or pivoting connection to the intermediate frame  26  (not shown in detail). Other configurations are contemplated. 
     Support wheels  56  are coupled to the base  24  to support the base  24  on a floor surface such as a hospital floor. The support wheels  56  allow the patient transport apparatus  20  to move in any direction along the floor surface by swiveling to assume a trailing orientation relative to a desired direction of movement. In the version shown, the support wheels  56  comprise four support wheels each arranged in corners of the base  24 . The support wheels  56  shown are caster wheels able to rotate and swivel about swivel axes  58  during transport. Each of the support wheels  56  forms part of a caster assembly  60 . Each caster assembly  60  is mounted to the base  24 . It should be understood that various configurations of the caster assemblies  60  are contemplated. In addition, in some versions, the support wheels  56  are not caster wheels and may be non-steerable, steerable, non-powered, powered, or combinations thereof. Additional support wheels  56  are also contemplated. 
     Referring to  FIG.  2   , an auxiliary wheel assembly  62  is coupled to the base  24 . The auxiliary wheel assembly  62  influences motion of the patient transport apparatus  20  during transportation over the floor surface. The auxiliary wheel assembly  62  comprises an auxiliary wheel  64  and a lift actuator  66  operatively coupled to the auxiliary wheel  64 . The lift actuator  66  is operable to move the auxiliary wheel  64  between a deployed position  68  (see  FIG.  5 C ) engaging the floor surface and a retracted position  70  (see  FIG.  5 A ) spaced away from and out of contact with the floor surface. The retracted position  70  may alternatively be referred to as the “fully retracted position.” The auxiliary wheel  64  may also be positioned in one or more intermediate positions  71  (see  FIG.  5 B ) between the deployed position  68  (see  FIG.  5 C ) and the retracted position  70  ( FIG.  5 A ). The intermediate position  71  may alternatively be referred to as a “partially retracted position,” or may also refer to another “retracted position” (e.g., compared to the “fully” retracted position  70  depicted in  FIG.  5 A ). The auxiliary wheel  64  influences motion of the patient transport apparatus  20  during transportation over the floor surface when the auxiliary wheel  64  is in the deployed position  68 . In some versions, the auxiliary wheel assembly  62  comprises an additional auxiliary wheel movable with the auxiliary wheel  64  between the deployed position  68  and the position  70  via the lift actuator  66 . 
     By deploying the auxiliary wheel  64  on the floor surface, the patient transport apparatus  20  can be easily moved down long, straight hallways or around corners, owing to a non-swiveling nature of the auxiliary wheel  64 . When the auxiliary wheel  64  is in the retracted position  70  (see  FIG.  5 A ) or in one of the intermediate positions  71 , the patient transport apparatus  20  is subject to moving in an undesired direction due to uncontrollable swiveling of the support wheels  56 . For instance, during movement down long, straight hallways, the patient transport apparatus  20  may be susceptible to “dog tracking,” which refers to undesirable sideways movement of the patient transport apparatus  20 . Additionally, when cornering, without the auxiliary wheel  64  deployed, and with all of the support wheels  56  able to swivel, there is no wheel assisting with steering through the corner, unless one or more of the support wheels  56  are provided with steer lock capability and the steer lock is activated. 
     The auxiliary wheel  64  may be arranged parallel to the longitudinal axis  28  of the base  24 . Said differently, the auxiliary wheel  64  rotates about a rotational axis R (see  FIG.  3   ) oriented perpendicularly to the longitudinal axis  28  of the base  24  (albeit offset in some cases from the longitudinal axis  28 ). In the version shown, the auxiliary wheel  64  is incapable of swiveling about a swivel axis. In other versions, the auxiliary wheel  64  may be capable of swiveling, but can be locked in a steer lock position in which the auxiliary wheel  64  is locked to solely rotate about the rotational axis R oriented perpendicularly to the longitudinal axis  28 . In still other versions, the auxiliary wheel  64  may be able to freely swivel without any steer lock functionality. 
     The auxiliary wheel  64  may be located to be deployed inside a perimeter of the base  24  and/or within a support wheel perimeter defined by the swivel axes  58  of the support wheels  56 . In some versions, such as those employing a single auxiliary wheel  64 , the auxiliary wheel  64  may be located near a center of the support wheel perimeter, or offset from the center. In this case, the auxiliary wheel  64  may also be referred to as a fifth wheel. In other versions, the auxiliary wheel  64  may be disposed along the support wheel perimeter or outside of the support wheel perimeter. In the version shown, the auxiliary wheel  64  has a diameter larger than a diameter of the support wheels  56 . In other versions, the auxiliary wheel  64  may have the same or a smaller diameter than the support wheels  56 . 
     In one version shown in  FIGS.  2 - 4   , the base  24  comprises a first cross-member  72   a  and a second cross-member  72   b . The auxiliary wheel assembly  62  is disposed between and coupled to the cross-members  72   a ,  72   b . The auxiliary wheel assembly  62  comprises a first auxiliary wheel frame  74   a  coupled to and arrange to articulate (e.g., pivot) relative to the first cross-member  72   a . The auxiliary wheel assembly  62  further comprises a second auxiliary wheel frame  74   b  pivotably coupled to the first auxiliary wheel frame  74   a  and the second cross-member  72   b . The second auxiliary wheel frame  74   b  is arranged to articulate and translate relative to the second cross-member  72   b . The second cross-member  72   b  defines a slot  78  for receiving a pin  80  (see  FIGS.  5 A and  5 C ) connected to the second auxiliary wheel frame  74   b  to permit the second auxiliary wheel frame  74   b  to translate and pivot relative to the second cross-member  72   b.    
     In the version shown in  FIGS.  3  and  4   , the auxiliary wheel assembly  62  comprises an auxiliary wheel drive system  90  (described in more detail below) operatively coupled to the auxiliary wheel  64 . The auxiliary wheel drive system  90  is configured to drive (e.g., rotate) the auxiliary wheel  64 . In the version shown, the auxiliary wheel drive system  90  comprises a motor  102  coupled to a power source  104  (shown schematically in  FIG.  10   ) and the second auxiliary wheel frame  74   b . The auxiliary wheel drive system  90  further comprises a gear train  106  coupled to the motor  102  and an axle  76  of the auxiliary wheel  64 . In the version shown, the auxiliary wheel  64 , the gear train  106 , and the motor  102  are arranged and supported by the second auxiliary wheel frame  74   b  to articulate and translate with the second auxiliary wheel frame  74   b  relative to the second cross-member  72   b . In other versions, the axle  76  of the auxiliary wheel  64  is coupled directly to the second auxiliary wheel frame  74   b  and the auxiliary wheel drive system  90  drives the auxiliary wheel  64  in another manner. Electrical power is provided from the power source  104  to energize the motor  102 . The motor  102  converts electrical power from the power source  104  to torque supplied to the gear train  106 . The gear train  106  transfers torque to the auxiliary wheel  64  to rotate the auxiliary wheel  64 . 
     In the version shown, the lift actuator  66  is a linear actuator comprising a housing  66   a  and a drive rod  66   b  extending from the housing  66   a . The drive rod  66   b  has a proximal end received in the housing  66   a  and a distal end spaced from the housing  66   a . The distal end of the drive rod  66   b  is configured to be movable relative to the housing  66   a  to extend and retract an overall length of the lift actuator  66 . The housing  66   a  is pivotally coupled to the second cross-member  72   b  and the distal end of the drive rod  66   b  is coupled to the first auxiliary wheel frame  74   a . More specifically, the first auxiliary wheel frame  74   a  defines a slot  82  to receive a pin  84  connected to the distal end of the drive rod  66   b  to permit the drive rod  66   b  to translate and pivot relative to the first auxiliary wheel frame  74   a.    
     In the version shown, the auxiliary wheel assembly  62  comprises a biasing device such as a torsion spring  86  to apply a biasing force to bias the first and second auxiliary wheel frames  74   a ,  74   b  toward the floor surface and thus move the auxiliary wheel  64  toward the deployed position  68  (see  FIG.  5 C ). The pin  84  at the distal end of the drive rod  66   b  abuts a first end of the slot  82  to limit the distance the torsion spring  86  would otherwise rotate the first auxiliary wheel frame  74   a  toward the floor surface. Thus, even though the torsion spring  86  applies the force that ultimately causes the auxiliary wheel  64  to move to the floor surface in the deployed position  68 , the lift actuator  66  is operable to move the auxiliary wheel  64  to the deployed position  68  and the retracted position  70  or any other position, such as one or more intermediate positions  71  between the deployed position  68  and the retracted position  70 . 
     In the version shown, in the deployed position  68  of  FIG.  5 C , the lift actuator  66  is controlled so that the pin  84  is located centrally in the slot  82  to permit the auxiliary wheel  64  to move away from the floor surface when encountering an obstacle and to dip lower when encountering a low spot in the floor surface. For instance, when the auxiliary wheel  64  encounters an obstacle, the auxiliary wheel  64  moves up to avoid the obstacle and the pin  84  moves toward a second end of the slot  82  against the biasing force from the torsion spring  86  without changing the overall length of the lift actuator  66 . Conversely, when the auxiliary wheel  64  encounters a low spot in the floor surface, the auxiliary wheel  64  is able to travel lower to maintain traction with the floor surface and the pin  84  moves toward the first end of the slot  82  via the biasing force from the torsion spring  86  without changing the overall length of the lift actuator  66 . 
     Referring to  FIG.  4   , the first and second auxiliary wheel frames  74   a ,  74   b  each comprise first arms pivotably coupled to each other on one side of the auxiliary wheel  64  (as shown in  FIG.  3   ) and second arms pivotably coupled to each other on the other side of the auxiliary wheel  64 . The first and second arms are pivotably connected by pivot pins. The first and second arms of the first auxiliary wheel frame  74   a  are rigidly connected to each other such that the first and second arms of the first auxiliary wheel frame  74   a  articulate together relative to the first cross-member  72   a . The first and second arms of the second auxiliary wheel frame  74   b  are rigidly connected to each other such that the first and second arms of the second auxiliary wheel frame  74   b  articulate and translate together relative to the second cross-member  72   b . The second cross-member  72   b  defines another slot  78  for receiving another pin  80  connected to the second auxiliary wheel frame  74   b  (one for each arm). The respective first and second arms of the first and second auxiliary wheel frames  74   a ,  74   b  cooperate to balance the force applied by the auxiliary wheel  64  against the floor surface. 
     Referring to  FIG.  5 A , the auxiliary wheel  64  is in the retracted position  70  spaced from the floor surface.  FIG.  5 A  illustrates one version of the auxiliary wheel  64  being in a “fully retracted” position  70 , and  FIG.  5 B  illustrates one version of the auxiliary wheel  64  being in one of the intermediate positions  71  (which may also referred to as a “partially-retracted” position or a “partially deployed” position). In the retracted position  70 , the lift actuator  66  applies a force against the biasing force of the torsion spring  86  to retain a spaced relationship of the auxiliary wheel  64  with the floor surface. To move the auxiliary wheel  64  to the deployed position  68  (see  FIG.  5 C ), the distal end of the drive rod  66   b  is configured to retract into the housing  66   a , which permits the biasing force of the torsion spring  86  to rotate the first auxiliary wheel frame  74   a , the second auxiliary wheel frame  74   b , and the auxiliary wheel  64  toward the floor surface. The second auxiliary wheel frame  74   b  is configured to rotate relative to the first auxiliary wheel frame  74   a  by virtue of the second auxiliary wheel frame  74   b  being pivotably coupled to the first auxiliary wheel frame  74   a  (via a pinned connection therebetween) and pivotably and slidably coupled to the second cross-member  72   b . In other words, the slot  78  of the second cross-member  72   b  permits the pin  80 , and thus the second auxiliary wheel frame  74   b  to move toward the first cross-member  72   a . To return the auxiliary wheel  64  to the retracted position  70 , the lift actuator  66  is configured to apply a force greater than the biasing force of the torsion spring  86  to move the auxiliary wheel  64  away from the floor surface. While a single intermediate position  71  is illustrated in  FIG.  5 B , one skilled in the art would recognize that there are more than one intermediate positions  71  possible between the deployed position  68  and the retracted position  70 . 
     Referring to  FIG.  5 C , the auxiliary wheel  64  is in the deployed position  68  engaging the floor surface. In this version, the overall length of the lift actuator  66  is shorter when the auxiliary wheel  64  is in the deployed position  68  than when the auxiliary wheel  64  is in the retracted position  70 . 
     Although an exemplary version of an auxiliary wheel assembly  62  is described above and shown in the drawings, it should be appreciated that other configurations employing a lift actuator  66  to move the auxiliary wheel  64  between the retracted position  70  and deployed position  68  are contemplated. 
     In some versions, the lift actuator  66  is configured to cease application of force against the biasing force of the torsion spring  86  instantly to permit the torsion spring  86  to move the auxiliary wheel  64  to the deployed position  68  expeditiously. In some versions, the auxiliary wheel  64  moves from the retracted position  70  to the deployed position  68  in less than three seconds. In another version, the auxiliary wheel  64  moves from the retracted position  70  to the deployed position  68  in less than two seconds. In still other versions, the auxiliary wheel  64  moves from the retracted position  70  to the deployed position  68  in less than one second. 
     In some versions, such as those shown in  FIGS.  6 A- 7   , one or more user interface sensors  88  are coupled to the first handle  52  to determine engagement by the user and generate a signal responsive to touch (e.g., hand placement/contact) of the user. The one or more user interface sensors  88  are operatively coupled to the lift actuator  66  to control movement of the auxiliary wheel  64  between the deployed position  68  and the retracted position  70 . Operation of the lift actuator  66  in response to the user interface sensor  88  is described in more detail below. In other versions, the user interface sensor  88  is coupled to another portion of the patient transport apparatus  20 , such as another user interface  50 . 
     In some versions, such as those depicted in  FIGS.  6 A- 7   , engagement features or indicia  89  are located on the first handle  52  to indicate to the user where the user&#39;s hands may be placed on a particular portion of the first handle  52  for the user interface sensor  88  to generate the signal indicating engagement by the user. For instance, the first handle  52  may comprise embossed or indented features to indicate where the user&#39;s hand should be placed. In other versions, the indicia  89  comprises a film, cover, or ink disposed at least partially over the first handle  52  and shaped like a handprint to suggest the user&#39;s hand should match up with the handprint for the user interface sensor  88  to generate the signal. In still other versions, the shape of the user interface sensor  88  acts as the indicia  89  to indicate where the user&#39;s hand should be placed for the user interface sensor  88  to generate the signal. In some versions (not shown), the patient transport apparatus  20  does not comprise a user interface sensor  88  operatively coupled to the lift actuator  66  for moving the auxiliary wheel  64  between the deployed position  68  and the retracted position  70 . Instead, a user input device is operatively coupled to the lift actuator  66  for the user to selectively move the auxiliary wheel  64  between the deployed position  68  and the retracted position  70 . 
     In the versions shown in  FIGS.  6 A- 7   , the auxiliary wheel drive system  90  is configured to drive (e.g., rotate) the auxiliary wheel  64  in response to a throttle  92  operable by the user. As is described in greater detail below in connection with  FIGS.  12 - 16 C , the throttle  92  is operatively attached to the first handle  52  in the illustrated version to define a throttle assembly  93 . In  FIGS.  6 A- 7    the throttle  92  is illustrated in a neutral throttle position N. The throttle  92  is movable in a first direction  94  (also referred to as a “forward direction”) relative to the neutral throttle position N and a second direction  96  (also referred to as a “backward direction”) relative to the neutral throttle position N opposite the first direction  94 . As will be appreciated from the subsequent description below, the auxiliary wheel drive system  90  drives the auxiliary wheel  64  in a forward direction FW (see  FIG.  5 C ) when the throttle  92  is moved in the first direction  94 , and in a rearward direction RW (see  FIG.  5 C ) when the throttle  92  is moved in the second direction  96 . When the throttle  92  is disposed in the neutral throttle position N, as shown in  FIG.  6 A  (see also  FIGS.  8 A and  8 D ), the auxiliary wheel drive system  90  does not drive the auxiliary wheel  64  in either direction. In many versions, the throttle  92  is spring-biased to the neutral throttle position N. In some versions, when the throttle  92  is in the neutral throttle position N, the auxiliary wheel drive system  90  permits the auxiliary wheel  64  to be manually rotated as a result of a user pushing on the first handle  52  or another user interface  50  to push the patient transport apparatus  20  in a desired direction. In other words, the motor  102  may be unbraked and capable of being driven manually. In some versions, a throttle biasing element  91  such as a torsion spring (shown schematically in  FIGS.  8 A- 8 F ) is used to bias or otherwise urge the throttle  92  to the neutral throttle position N such that when a user releases the throttle  92  after rotating the throttle  92  relative to the first handle  52  in either direction, the throttle biasing element  91  returns the throttle  92  to the neutral throttle position N. 
     It should be appreciated that the terms forward and backward are used to describe opposite directions that the auxiliary wheel  64  rotates to move the base  24  along the floor surface. For instance, forward refers to movement of the patient transport apparatus  20  with the foot end leading and backward refers to the head end leading. In other versions, backward rotation moves the patient transport apparatus  20  in the direction with the foot end leading and forward rotation moves the patient transport apparatus  20  in the direction with the head end leading. In this version, the handles  52 ,  54  may be located at the foot end. 
     Referring to  FIGS.  6 A- 7   , the location of the throttle  92  relative to the first handle  52  permits the user to simultaneously grasp the handle body  55  of the first handle  52  and rotate the throttle  92  about the central axis C defined by the inner support  53 . This allows the user interface sensor  88 , which is operatively attached to the handle body  55  in the illustrated version, to generate the signal responsive to touch by the user while the user moves the throttle  92 . In some versions, the throttle  92  comprises one or more throttle interfaces for assisting the user with rotating the throttle  92 ; more specifically, a thumb throttle interface  98   a  arranged so as to be engaged or otherwise operated by a user&#39;s thumb, and a finger throttle interface  98   b  arranged so as to be engaged or otherwise operated by one or more fingers of the user (e.g., forefinger). In some versions, the throttle  92  comprises only one of the throttle interfaces  98   a ,  98   b . The user may place their thumb on either side of the thumb throttle and finger throttle interfaces  98   a ,  98   b  to assist in rotating the throttle  92  relative to the first handle  52 . In some versions, the user may rotate the throttle  92  in the first direction  94  using the thumb throttle interface  98   a  and in the second direction  96  using the finger throttle interface  98   b , or vice-versa. 
     In some versions, the throttle assembly  93  may comprise one or more auxiliary user interface sensors  88 A, in addition to the user interface sensor  88 , to determine engagement by the user. In the version illustrated in  FIGS.  6 A- 7   , the auxiliary user interface sensors  88 A are realized as throttle interface sensors  100  respectively coupled to each of the throttle interface  98   a ,  98   b  and operatively coupled to the auxiliary wheel drive system  90  (e.g., via electrical communication). The throttle interface sensors  100  are likewise configured to determine engagement by the user and generate a signal responsive to touch of the user&#39;s thumb and/or fingers. When the user is touching one or more of the throttle interfaces  98   a ,  98   b , the throttle interface sensors  100  generate a signal indicating the user is currently touching one or more of the throttle interfaces  98   a ,  98   b  and movement of the throttle  92  is permitted to cause rotation of the auxiliary wheel  64 . When the user is not touching any of the throttle interfaces  98   a ,  98   b , the throttle interface sensors  100  generate a signal indicating an absence of the user&#39;s thumb and/or fingers on the throttle interfaces  98   a ,  98   b , and movement of the throttle  92  is restricted from causing rotation of the auxiliary wheel  64 . The throttle interface sensors  100  mitigate the chances for inadvertent contact with the throttle  92  to unintentionally cause rotation of the auxiliary wheel  64 . The throttle interface sensors  100  may be absent in some versions. As is described in greater detail below in connection with  FIGS.  12 - 16 C , other types of auxiliary user interface sensors  88 A are contemplated by the present disclosure besides the throttle interface sensors  100  described above. Furthermore, it will be appreciated that certain versions may comprise both the user interface sensor  88  and the auxiliary user interface sensor  88   a  (e.g., one or more throttle interface sensors  100 ), whereas other versions may comprise only one of either the user interface sensor  88  and the auxiliary user interface sensor  88 a. Other configurations are contemplated. 
     Referring to  FIGS.  8 A- 8 F , various positions of the throttle  92  are shown. The throttle  92  is movable relative to the first handle  52  in a first throttle position, a second throttle position, and intermediate throttle positions therebetween. The throttle  92  is operable between the first throttle position and the second throttle position to adjust the rotational speed of the auxiliary wheel. 
     In some versions, the first throttle position corresponds with the neutral throttle position N (shown in  FIGS.  8 A and  8 D ; see also  FIGS.  16 A,  22 A, and  23 A ) and the auxiliary wheel  64  is at rest. The second throttle position is defined as an operating throttle position  107  (see  FIG.  8 A ) and, more specifically, corresponds with a maximum forward position  108  (shown in  FIG.  8 C ; see also  FIGS.  16 B,  22 B, and  23 B ) of the throttle  92  moved in the first direction  94 . Here, the intermediate throttle position is also defined as an operating throttle position  107  and, more specifically, corresponds with an intermediate forward throttle position  110  (shown  FIG.  8 B ) of the throttle  92  between the neutral throttle position N and the maximum forward throttle position  108 . Here, both the maximum forward position  108  and the intermediate forward throttle position  110  may also be referred to as forward throttle positions  111  (see  FIG.  8 A ). 
     In other cases, the second throttle position corresponds with a maximum backward throttle position  112  (shown in  FIG.  8 E ; see also  FIGS.  16 C,  22 C, and  23 C ) of the throttle  92  moved in the second direction  96 . Here, the intermediate throttle position corresponds with an intermediate backward throttle position  114  (shown in  FIG.  8 F ) of the throttle  92  between the neutral throttle position N and the maximum backward throttle position  112 . Here, both the maximum backward throttle position  112  and the intermediate backward throttle position  114  may also be referred to as backward throttle positions  115  (see  FIG.  8 F ). In the versions shown, the throttle  92  is movable from the neutral throttle position N to one or more operating throttle positions  107  (see  FIGS.  8 A and  8 F ) between the maximum backward throttle position  112  and the maximum forward throttle position  108 , including a plurality of forward throttle positions  111  (e.g., the intermediate forward throttle position  110 ) between the neutral throttle position N and the maximum forward throttle position  108  as well as a plurality of backward throttle positions  115  (e.g., the intermediate backward throttle position  114 ) between the neutral throttle position N and the maximum backward throttle position  112 . The configuration of the throttle  92  and the throttle assembly  93  will be described in greater detail below. 
     In some versions, as shown schematically in  FIG.  10   , the patient transport apparatus  20  comprises a support wheel brake actuator  116  operably coupled to one or more of the support wheels  56  for braking one or more support wheels  56 . In some versions, the support wheel brake actuator  116  comprises a brake member  118  coupled to the base  24  and movable between a braked position engaging one or more of the support wheels  56  to brake the support wheel  56  and a released position permitting one or more of the support wheels  56  to rotate freely. 
     In some versions, as shown schematically in  FIG.  10   , the patient transport apparatus  20  comprises an auxiliary wheel brake actuator  120  operably coupled to the auxiliary wheel  64  for braking the auxiliary wheel  64 . In some versions, the auxiliary wheel brake actuator  120  comprises a brake member  122  coupled to the base  24  and movable between a braked position engaging the auxiliary wheel  64  to brake the auxiliary wheel  64  and a released position permitting the auxiliary wheel  64  to rotate freely. 
     As noted above, the user may place their thumb on either side of the thumb throttle and finger throttle interfaces  98   a ,  98   b  to assist in rotating the throttle  92  relative to the first handle  52 . In some versions, the user may rotate the throttle  92  in either the first direction  94  or the second direction  96  using the thumb throttle interfaced  98   a ,  98   b , or vice-versa, to cause rotation of the auxiliary wheel  64  and thereby modulate propulsion of the patient transport apparatus  20  between the forward direction and the rearward direction. As is described in greater detail below in connection with  FIGS.  12 - 17   , the representative version of the throttle assembly  93  includes a damper assembly  95  interposed between the throttle  92  and the first handle  52  and arranged to provide torque resisting rotation of the throttle  92  as the throttle  92  rotates relative to the handle  52 . In this way, movement of the throttle  92  relative to the first handle  52  can be proportional to, can be associated with, and/or can otherwise correspond to the propulsion of the patient transport apparatus  20 . 
       FIG.  10    illustrates a control system  124  of the patient transport apparatus  20 . The control system  124  comprises a controller  126  coupled to, among other components, the user interface sensors  88 ,  88 A, the throttle assembly  93 , the lift actuator  66 , the auxiliary wheel drive system  90 , the throttle interface sensors  100 , the support wheel brake actuator  116 , the bed lift actuator  37   a , and the auxiliary wheel brake actuator  120 . The controller  126  is configured to operate the lift actuator  66 , the auxiliary wheel drive system  90 , the support wheel brake actuator  116 , the bed lift actuator  37   a  to operate the lift assembly  37 , and the auxiliary wheel brake actuator  120 . The controller  126  is configured to detect the signals from the sensors  88 ,  88   a ,  100 . The controller  126  is further configured to operate the lift actuator  66  responsive to the user interface sensor  88  generating signals responsive to touch. 
     The controller  126  includes a memory  127 . Memory  127  may be any memory suitable for storage of data and computer-readable instructions. For example, the memory  127  may be a local memory, an external memory, or a cloud-based memory embodied as random access memory (RAM), non-volatile RAM (NVRAM), flash memory, or any other suitable form of memory. 
     The controller  126  generally comprises one or more microprocessors for processing instructions or for processing algorithms stored in memory to control operation of the lift actuator. Additionally or alternatively, the controller  126  may comprise one or more microcontrollers, field programmable gate arrays, systems on a chip, discrete circuitry, and/or other suitable hardware, software, or firmware that is capable of carrying out the functions described herein. The controller  126  may be carried on-board the patient transport apparatus  20 , or may be remotely located. In some versions, the controller  126  is mounted to the base  24 . 
     In some versions, the controller  126  comprises an internal clock to keep track of time. In some versions, the internal clock is a microcontroller clock. The microcontroller clock may comprise a crystal resonator; a ceramic resonator; a resistor, capacitor (RC) oscillator; or a silicon oscillator. Examples of other internal clocks other than those disclosed herein are fully contemplated. The internal clock may be implemented in hardware, software, or both. 
     In some versions, the memory  127 , microprocessors, and microcontroller clock cooperate to send signals to and operate the actuators  66 ,  116 ,  120  and the auxiliary wheel drive system  90  to meet predetermined timing parameters. These predetermined timing parameters are discussed in more detail below and are referred to as predetermined durations. 
     The controller  126  may comprise one or more subcontrollers configured to control the actuators  66 ,  116 ,  120  or the auxiliary wheel drive system  90 , or one or more subcontrollers for each of the actuators  66 ,  116 ,  120  or the auxiliary wheel drive system  90 . In some cases, one of the subcontrollers may be attached to the intermediate frame  26  with another attached to the base  24 . Power to the actuators  66 ,  116 ,  120 , the auxiliary wheel drive system  90 , and/or the controller  126  may be provided by a battery power supply  128 . 
     The controller  126  may communicate with the actuators  66 ,  116 ,  120  and the auxiliary wheel drive system  90  via wired or wireless connections. The controller  126  generates and transmits control signals to the actuators  66 ,  116 ,  120  and the auxiliary wheel drive system  90 , or components thereof, to operate the actuators  66 ,  116 ,  120  and the auxiliary wheel drive system  90  to perform one or more desired functions. 
     In some versions, and as is shown in  FIGS.  6 A- 7   , the control system  124  comprises an auxiliary wheel position indicator  130  to display a current position of the auxiliary wheel  64  between or at the deployed position  68  and the retracted position  70 , and the one or more intermediate positions  71 . In some versions, the auxiliary wheel position indicator  130  comprises a light bar that lights up completely when the auxiliary wheel  64  is in the deployed position  68  to indicate to the user that the auxiliary wheel  64  is ready to be driven. Likewise, the light bar may be partially lit up when the auxiliary wheel  64  is in a partially retracted position and the light bar may be devoid of light when the auxiliary wheel  64  is in the fully retracted position  70 . Other visualization schemes are possible to indicate the current position of the auxiliary wheel  64  to the user, such as other graphical displays, text displays, and the like. Such light indicators or displays are coupled to the controller  126  to be controlled by the controller  126  based on the detected position of the auxiliary wheel  64  as described below. 
     In one version schematically shown in  FIG.  10   , the control system  124  comprises a user feedback device  132  coupled to the controller  126  to indicate to the user one of a current speed, a current range of speeds, a current throttle position, and a current range of throttle positions. In some versions, the user feedback device  132  comprises one of a visual indicator, an audible indicator, and a tactile indicator. 
     In one exemplary version shown in  FIGS.  6 A and  8   , when the user operates the throttle  92  to move the throttle  92  between the neutral throttle position N and the intermediate forward throttle position  110 , a first LED  132   a  lights up to indicate to a user that the current throttle position is between the neutral throttle position N and the intermediate forward throttle position  110 . When the user operates the throttle  92  to move the throttle  92  to a position between the intermediate forward throttle position  110  and the maximum forward throttle position  108 , the first LED  132   a  may turn off and a second LED  132   b  lights up to indicate to the user that a new range of throttle positions or a new range of speeds has been selected. 
     In other versions LED&#39;s may illuminate different colors to indicate different settings, positions, speeds, etc. In still other versions, at least a portion of the throttle  92  is translucent to permit different colors and or color intensities to shine through and indicate different settings, positions, speeds, etc. 
     In another exemplary version, the first handle  52  comprises a plurality of detents  133   a  (shown in  FIG.  8 A ) for providing tactile feedback to the user to indicate one of a change in throttle position and a change in a range of throttle positions when the user moves the throttle  92  relative to the first handle  52  to effect a change in throttle position. A detent spring  133   b  is coupled to the throttle  92  to rotate with the throttle  92  relative to the first handle  52 . The detent spring  133   b  biases a detent ball  133   c  into engagement with the plurality of detents  133   a . When the user rotates the throttle  92 , the plurality of detents  133   a  and detent ball  133   c  assist the user in retaining a throttle position. The detent spring  133   b  biases the detent ball  133   c  with a force less than the biasing force of the throttle biasing element  91 . In this manner, the force of the detent spring  133   b  does not restrict the throttle biasing element  91  from returning the throttle  92  to the neutral throttle position N when the user releases the throttle  92 . In other versions, the detent spring  133   b  may be coupled to the first handle  52  and the plurality of detents  133   a  may be coupled to the throttle  92  to rotate with the throttle  92  relative to the first handle  52 . 
     Other visualization schemes are possible to indicate one or more of the current speed, the current range of speeds, the current throttle position, and the current range of throttle positions to the user or other settings of the throttle  92 , such as other graphical displays, text displays, and the like. Such light indicators or displays are coupled to the controller  126  to be controlled by the controller  126  based on the detected one or more current speed, current range of speeds, current throttle position, and current range of throttle positions or other current settings as described below. 
     The actuators  66 ,  116 ,  120  and the auxiliary wheel drive system  90  described above may comprise one or more of an electric actuator, a hydraulic actuator, a pneumatic actuator, combinations thereof, or any other suitable types of actuators, and each actuator may comprise more than one actuation mechanism. The actuators  66 ,  116 ,  120  and the auxiliary wheel drive system  90  may comprise one or more of a rotary actuator, a linear actuator, or any other suitable actuators. The actuators  66 ,  116 ,  120  and the auxiliary wheel drive system  90  may comprise reversible, DC motors, or other types of motors. 
     A suitable actuator for the lift actuator  66  comprises a linear actuator supplied by LINAK A/S located at Smedevænget 8, Guderup, DK-6430, Nordborg, Denmark. It is contemplated that any suitable actuator capable of deploying the auxiliary wheel  64  may be utilized. 
     The controller  126  is generally configured to operate the lift actuator  66  to move the auxiliary wheel  64  to the deployed position  68  responsive to detection of the signal from the user interface sensor  88 . When the user touches the first handle  52 , the user interface sensor  88  generates a signal indicating the user is touching the first handle  52  and the controller operates the lift actuator  66  to move the auxiliary wheel  64  to the deployed position  68 . In some versions, the controller  126  is further configured to operate the lift actuator  66  to move the auxiliary wheel  64  to the retracted position  70  responsive to the user interface sensor  88  generating a signal indicating the absence of the user touching the first handle  52 . 
     In some versions, the controller  126  is configured to operate the lift actuator  66  to move the auxiliary wheel  64  to the deployed position  68  responsive to detection of the signal from the user interface sensor  88  indicating the user is touching the first handle  52  for a first predetermined duration greater than zero seconds. Delaying operation of lift actuator  66  for the first predetermined duration after the controller  126  detects the signal from the sensor  88  indicating the user is touching the first handle  52  mitigates chances for inadvertent contact to result in operation of the lift actuator  66 . In some versions, the controller  126  is configured to initiate operation of the lift actuator  66  to move the auxiliary wheel  64  to the deployed position  68  immediately after (e.g., less than 1 second after) the user interface sensor  88  generates the signal indicating the user is touching the first handle  52 . 
     In some versions, the controller  126  is further configured to operate the lift actuator  66  to move the auxiliary wheel  64  to the retracted position  70 , or to the one or more intermediate positions  71 , responsive to the user interface sensor  88  generating a signal indicating the absence of the user touching the first handle  52 . In some versions, the controller  126  is configured to operate the lift actuator  66  to move the auxiliary wheel  64  to the retracted position  70 , or to the one or more intermediate positions  71 , responsive to the user interface sensor  88  generating the signal indicating the absence of the user touching the first handle  52  for a predetermined duration greater than zero seconds. In some versions, the controller  126  is configured to initiate operation of the lift actuator  66  to move the auxiliary wheel  64  to the retracted position  70 , or to the one or more intermediate positions  71 , immediately after (e.g., less than 1 second after) the user interface sensor  88  generates the signal indicating the absence of the user touching the first handle  52 . 
     In versions including the support wheel brake actuator  116  and/or the auxiliary wheel brake actuator  120 , the controller  126  may also be configured to operate one or both brake actuators  116 ,  120  to move their respective brake members  118 ,  122  between the braked position and the released position. In some versions, the controller  126  is configured to operate one or both brake actuators  116 ,  120  to move their respective brake members  118 ,  122  to the braked position responsive to the user interface sensor  88  generating the signal indicating the absence of the user touching the first handle  52  for a predetermined duration. In some versions, the predetermined duration for moving brake members  118 ,  122  to the braked position is greater than zero seconds. In some versions, the controller  126  is configured to initiate operation of one or both brake actuators  116 ,  120  to move their respective brake members  118 ,  122  to the braked position immediately after (e.g., less than 1 second after) the user interface sensor  88  generates the signal indicating the absence of the user touching the first handle  52 . 
     In some versions, the controller  126  is configured to operate one or both brake actuators  116 ,  120  to move their respective brake members  118 ,  122  to the released position responsive to the user interface sensor  88  generating the signal indicating the user is touching the first handle  52  for a predetermined duration. In some versions, the predetermined duration for moving brake members  118 ,  122  to the released position is greater than zero seconds. In some versions, the controller  126  is configured to initiate operation of one or both brake actuators  116 ,  120  to move their respective brake members  118 ,  122  to the released position immediately after (e.g., less than 1 second after) the user interface sensor  88  generates the signal indicating the user is touching the first handle  52 . 
     In some versions, an auxiliary wheel position sensor  146  (also referred to as a “position sensor”) is coupled to the controller  126  and generates signals detected by the controller  126 . The auxiliary wheel position sensor  146  is coupled to the controller  126  and the controller  126  is configured to detect the signals from the auxiliary wheel position sensor  146  to detect positions of the auxiliary wheel  64  as the auxiliary wheel  64  moves between the deployed position  68 , the one or more intermediate positions  71 , and the retracted position  70 . 
     In some versions, the auxiliary wheel position sensor  146  is disposed at a first sensor location S 1  (see  FIGS.  5 A- 5 C ) at a pivot point of the first auxiliary wheel frame  74   a . The auxiliary wheel position sensor  146  (e.g., realized with a potentiometer, an encoder, etc.) generates one or more signals responsive to the position of the first auxiliary wheel frame  74   a  and the controller  126  determines the position of the auxiliary wheel  64  from changes in position of the first auxiliary wheel frame  74   a  (e.g., via angular changes in position of the first auxiliary wheel frame  74   a  detected by the controller  126  through signals from the sensor  146 ). 
     In another version, the auxiliary wheel position sensor  146  is disposed at a second sensor location S 2  (see  FIGS.  5 A- 5 C ), coupled to the lift actuator  66 . The auxiliary wheel position sensor  146  (e.g., hall effect sensor, a linear potentiometer, a linear variable differential transformer, and the like) generates a signal responsive to the change in position of the drive rod  66   b  relative to the housing  66   a  and the controller  126  determines the position of the auxiliary wheel  64  from operation of the lift actuator  66 . 
     In other versions, the auxiliary wheel position sensor  146  is disposed on the base  24  or another component of the patient transport apparatus  20  to directly monitor the position of the auxiliary wheel  64  and generate signals responsive to the position of the auxiliary wheel  64 . In still other versions, the auxiliary wheel position sensor  146  detects the position of the auxiliary wheel  64  in another manner. 
     In some versions, the controller  126  is configured to operate one or both brake actuators  116 ,  120  to move their respective brake members  118 ,  122  to the released position responsive to detection of the auxiliary wheel  64  being in the deployed position  68 . In other versions, the controller  126  is configured to operate one or both brake actuators  116 ,  120  to move their respective brake members  118 ,  122  to the released position responsive to detection of the auxiliary wheel  64  being in a position between the deployed position  68  and the retracted position  70  (e.g., the one or more intermediate positions  71 ). 
     In some versions, the controller  126  is configured to operate the lift actuator  66  to move the auxiliary wheel  64  to the retracted position  70  (See  FIG.  5 A ) and the partially retracted (intermediate) position  71  (See  FIG.  5 B ) between the deployed position  68  (See  FIG.  5 C ) and the retracted position  70  (see  FIG.  5 A ). More specifically, the controller  126  generates control signals to command the lift actuator  66  to move the auxiliary wheel  64  based on feedback to the controller  126  from the auxiliary wheel position sensor  146  as to the current position of the auxiliary wheel  64 . In the partially retracted (intermediate) position  71 , the auxiliary wheel  64  is still spaced from the floor surface, but is closer to the floor surface than when in the retracted position  70 . 
     In some versions, the controller  126  is configured to operate the lift actuator  66  to temporarily hold the auxiliary wheel  64  at the partially retracted (intermediate) position  71  for a duration greater than zero seconds as the auxiliary wheel  64  moves from the deployed position  68  toward the retracted position  70 . This configuration prevents the auxiliary wheel  64  from traveling a greater distance to the retracted position  70  when the user interface sensor  88  detects a brief absence of the user. For instance, when a user momentarily releases their hand from the first handle  52  to move the patient transport apparatus  20  via the support wheels  56  in a direction transverse to a direction of travel of the auxiliary wheel  64 , the lift actuator  66  moves the auxiliary wheel  64  to the partially retracted (intermediate) position  71 . When the user returns their hand into engagement with the first handle  52  before the duration expires, the lift actuator  66  will not have to move the auxiliary wheel  64  as far to return the auxiliary wheel  64  to the deployed position  68 . If the duration of time expires, then the controller  126  operates the lift actuator  66  to move the auxiliary wheel  64  to the retracted position  70 . The duration of time for which the user may be absent before the auxiliary wheel  64  is moved to the retracted position  70  may be 15 seconds or less, 30 seconds or less, 1 minute or less, 3 minutes or less, or other suitable durations. 
     In some versions, the control system  124  comprises a transverse force sensor  148  coupled to the controller  126  and the axle  76  of the auxiliary wheel  64 . The transverse force sensor  148  is configured to generate a signal responsive to a force being applied to the patient transport apparatus  20  in a direction transverse to the direction of travel of the auxiliary wheel  64 . The controller  126  is configured to detect the signal. For instance, when the user applies force to the user interface  50  of one of the side rails  38 ,  40 ,  42 ,  44  to move the base  24  in a direction transverse to the direction of travel of the auxiliary wheel  64 , the force from the user is transferred through the support structure  22  to the auxiliary wheel  64 . When the controller  126  detects a transverse force above a predetermined threshold, the controller  126  is configured to operate the lift actuator  66  to move the auxiliary wheel  64  to the partially retracted (intermediate) position  71  for a predetermined duration of time greater than zero seconds. In some versions, the controller  126  is configured to also operate the support wheel brake actuator  116  to move the brake member  118  to the released position when the controller  126  detects the transverse force above the predetermined threshold. 
     In some versions, the controller  126  is configured to operate the lift actuator  66  to move the auxiliary wheel  64  to the partially retracted (intermediate) position  71  when the controller detects the transverse force above the predetermined threshold even if the user interface sensor  88  detects the presence of the user. For example, while the user has their hand on the first handle  52 , a second user exerts a transverse force on one or more side rails  38 ,  40 ,  42 ,  44  to move the base  24  in a direction transverse to the direction of travel of the auxiliary wheel  64 . The controller  126  is configured to operate the lift actuator  66  to retract the auxiliary wheel  64  despite the user interface sensor  88  generating signals indicating the user is touching the first handle  52 . 
     In some versions, the lift actuator  66  is operable to move the auxiliary wheel  64  to a fully deployed position  68  and a partially deployed position (not shown) defined as an intermediate position  71  where the auxiliary wheel  64  engages the floor surface with less force than when in the fully deployed position  68 . More specifically, the lift actuator  66  is operable to permit the torsion spring  86  to bias the auxiliary wheel  64  to a partially deployed position before the fully deployed position  68 . 
     In some versions, an auxiliary wheel load sensor  150  is coupled to the auxiliary wheel  64  and the controller  126 , with the auxiliary wheel load sensor  150  configured to generate a signal responsive to a force of the auxiliary wheel  64  being applied to the floor surface. In some versions, the auxiliary wheel load sensor  150  is coupled to the axle  76  of the auxiliary wheel  64 . The controller  126  is configured to detect the signal from the auxiliary wheel load sensor  150  and, in some versions, is configured to operate the auxiliary wheel drive system  90  to drive the auxiliary wheel  64  and move the base  24  relative to the floor surface responsive to the controller  126  detecting signals from the auxiliary wheel load sensor  150  indicating the auxiliary wheel  64  is in the partially deployed position engaging the floor surface when a force of the auxiliary wheel  64  on the floor surface exceeds an auxiliary wheel load threshold. This allows the user to drive the auxiliary wheel  64  before the auxiliary wheel  64  reaches the fully deployed position without the auxiliary wheel  64  slipping against the floor surface. 
     As is described in greater detail below, in some versions, a patient load sensor  152  is coupled to the controller  126  and to one of the base  24  and the intermediate frame  26 . The patient load sensor  152  generates a signal responsive to weight, such as a patient being disposed on the base  24  and/or the intermediate frame  26 . The controller  126  is configured to detect the signal from the patient load sensor  152 . Here, the auxiliary wheel load threshold may change based on detection of the signal generated by the patient load sensor  152  to compensate for changes in weight disposed on the intermediate frame  26  and/or the base  24  to mitigate probability of the auxiliary wheel  64  slipping when the controller  126  operates the auxiliary wheel drive system  90 . 
     In the illustrated versions, where the auxiliary wheel drive system  90  comprises the motor  102  and the gear train  106 , the controller  126  is configured to operate the motor  102  to drive the auxiliary wheel  64  and move the base  24  relative to the floor surface responsive to detection of the auxiliary wheel  64  being in the partially deployed position as detected by virtue of the controller  126  detecting the motor  102  drawing electrical power from the power source  104  above an auxiliary wheel power threshold, such as by detecting a change in current draw of the motor  102  associated with the auxiliary wheel  64  being in contact with the floor surface. In this case, detection of the current drawn by the motor  102  being above a threshold operates as a form of auxiliary wheel load sensor  150 . 
     In some versions, when power is not supplied to the motor  102  from the power source  104 , the motor  102  acts as a brake to decelerate the auxiliary wheel  64  through the gear train  106 . In other versions, the auxiliary wheel  64  is permitted to rotate freely when power is not supplied to the motor  102 . 
     In some versions, the controller  126  is configured to operate the motor  102  to brake the motor  102 , and thus the auxiliary wheel  64 , responsive to detection of the signal from the user interface sensor  88  indicating the user is not touching the first handle  52  for a predetermined duration. In some versions, the predetermined duration is greater than zero seconds. In other versions, the controller  126  is configured to initiate operation of the motor  102  to brake the motor  102 , and thus the auxiliary wheel  64 , immediately after (e.g., less than 1 second after) the controller  126  detects the signal from the user interface sensor  88  indicating the user is not touching the first handle  52 . 
     In some versions, when the throttle  92  is in the neutral throttle position N, the auxiliary wheel drive system  90  permits the auxiliary wheel  64  to be manually rotated as a result of a user pushing on the first handle  52  or another user interface  50  to push the patient transport apparatus  20  in a desired direction. In other words, the motor  102  may be unbraked and capable of being driven manually. 
     In some versions, one or more of the base  24 , the intermediate frame  26 , the patient support deck  30 , and the side rails  38 ,  40 ,  42 ,  44  are configured to be coupled to an ancillary device (not shown) such as a table or a nurse module. In other versions, the ancillary device is another device configured to be coupled to the patient transport apparatus  20 . An ancillary device sensor  154  is coupled to the controller  126  and configured to generate a signal responsive to whether the ancillary device is coupled to one or more of the base  24 , the intermediate frame  26 , the patient support deck  30 , and the side rails  38 ,  40 ,  42 ,  44 . The controller  126  is configured to detect the signal from the ancillary device sensor  154 . When the controller  126  detects the ancillary device being coupled to one or more of the base  24 , the intermediate frame  26 , the patient support deck  30 , and the side rails  38 ,  40 ,  42 ,  44 , the controller  126  is configured to operate the support wheel brake actuator  116  to move the brake member  118  to the braked position and to operate the lift actuator  66  to move the auxiliary wheel  64  to the retracted position  70  (or, in some versions, to an intermediate position  71 ). The controller  126  may be configured to operate the support wheel brake actuator  116  and the lift actuator  66  in this manner even when the user interface sensor  88  detects the presence of the user. 
     In some versions, the user interface sensor  88  comprises a first sensor coupled to the first handle  52 , and a second sensor coupled to the second handle  54 . In some versions, the controller  126  requires the first and second sensors of the user interface sensor  88  to generate signals indicating the user is touching both the first and second handles  52 ,  54  to operate the actuators  66 ,  116 ,  120  or the auxiliary wheel drive system  90  as described above where the controller  126  facilitates operation based on detection of the user touching the first handle  52 . Likewise, in such versions, the controller  126  may require the first and second sensors of the user interface sensor to generate signals indicating the user is not touching either of the first and second handles  52 ,  54  to operate the actuators  66 ,  116 ,  120  or the auxiliary wheel drive system  90  as described above where the controller  126  facilitates operation based on detection of the user not touching the first handle  52 . In other versions, the controller  126  may require one or both of the first and second sensors of the user interface sensor  88  to generate a signal indicating the user is touching at least one of the first and second handles  52 ,  54  to operate actuators  66 ,  116 ,  120  or the auxiliary wheel drive system  90  as described above where the controller  126  facilitates operation based on detection of the user touching the first handle  52 . In another version, the controller  126  may require one or both of the first and second sensors of the user interface sensor  88  to generate a signal indicating the user is not touching at least one of first and second handles  52 ,  54  to operate the actuators  66 ,  116 ,  120  or the auxiliary wheel drive system  90  as described above where the controller  126  facilitates operation based on detection of the user not touching the first handle  52 . 
     As noted above, the controller  126  is configured to operate the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  in response to operation of the throttle  92  such that moving the throttle  92  from the neutral throttle position N toward one of the maximum forward and maximum backward throttle positions  108 ,  112  increases the rotational speed of the auxiliary wheel  64  (e.g., increases the rotational velocity of the auxiliary wheel  64  in the desired direction). 
     Referring to  FIGS.  9 A and  9 B , graphs illustrating two versions of the relationship between throttle position and auxiliary wheel rotational speed are shown. The rotational speed of the auxiliary wheel  64  is shown on the Y-axis and changes in a non-linear manner with respect to movement of the throttle  92 . The rotational speed of the auxiliary wheel  64  in each graph are not expressed in units, but denoted as a percentage of maximum speed in either direction. In other cases, rotation speed or velocity could be shown on the Y-axis. Throttle position is shown on the X-axis. The throttle position at  0 % corresponds to the neutral throttle position N. The throttle position at 100% corresponds to maximum forward throttle position  108 . The throttle position at −100% corresponds to maximum backward throttle position  112 . 
       FIG.  9 A  illustrates one version of a first speed mode  134  of throttle position relative to rotational speed of the auxiliary wheel  64 .  FIG.  9 B  illustrates one version of a second speed mode  136  of throttle position relative to rotational speed of the auxiliary wheel  64 . In some versions, the controller  126  operates the auxiliary wheel drive system  90  using the first speed mode  134  illustrated in  FIG.  9 A . In another version, the controller  126  operates the auxiliary wheel drive system  90  using the second speed mode  136  illustrated in  10 B. In another version described further below, the controller  126  is configured to switch between the first and second speed modes 
     When the throttle  92  is in the maximum forward throttle position  108  and the controller  126  operates the auxiliary wheel drive system  90  using the first speed mode  134 , the controller  126  is configured to operate the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  at a maximum forward rotational speed. When the throttle  92  is in the maximum backward throttle position  112  and the controller  126  operates the auxiliary wheel drive system  90  using the first speed mode  134 , the controller  126  is configured to operate the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  at a maximum backward rotational speed. 
     When the throttle  92  is in the maximum forward throttle position  108  and the controller  126  operates the auxiliary wheel drive system  90  using the second speed mode  136 , the controller  126  is configured to operate the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  at an intermediate forward rotational speed less than the maximum forward rotational speed. When the throttle  92  is in the maximum backward throttle position  112  and the controller  126  operates the auxiliary wheel drive system  90  using the second speed mode  136 , the controller  126  is configured to operate the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  at an intermediate backward rotational speed less than the maximum backward rotational speed. 
     Switching between the two speed modes  134 ,  136  allows the patient transport apparatus  20  to operate at relatively fast speeds, preferred for moving the patient transport apparatus  20  through open areas and for long distances such as down hallways, and relatively slow speeds, preferred for moving the patient transport apparatus  20  in congested areas, such as a patient room, elevator, etc., where the user seeks to avoid collisions with external objects and people. 
     In some versions, the control system  124  comprises a condition sensor  138  (schematically shown in  FIG.  10   ) coupled to the controller  126 . The condition sensor  138  is configured to generate a signal responsive to a condition of the patient transport apparatus  20  indicating a presence or absence of the condition and the controller  126  is configured to detect the signal from the condition sensor  138 . The condition of the patient transport apparatus  20  comprises one of power being received from an external power source  140 , an obstacle in close proximity to the base  24 , a connection between the patient transport apparatus  20  and an external device, and at least part of the support structure  22  entering a predetermined location. 
     In some versions, the controller  126  is configured to automatically operate the auxiliary wheel drive system  90  using the second speed mode  136  to limit the forward rotational speed of the auxiliary wheel  64  to the intermediate forward rotational speed responsive to the throttle  92  being in the maximum forward throttle position  108  and the condition sensor  138  generating a signal indicating the presence of the condition of the patient transport apparatus  20 . The controller  126  is further configured to operate the auxiliary wheel drive system  90  using the second speed mode  136  to limit the backward rotational speed of the auxiliary wheel  64  to the intermediate backward rotational speed responsive to the throttle  92  being in the maximum backward throttle position  112  and the condition sensor  138  generating the signal indicating the presence of the condition of the patient transport apparatus  20 . 
     The controller  126  is configured to operate the auxiliary wheel drive system  90  using the first speed mode  134  to permit the forward rotational speed of the auxiliary wheel  64  to reach the maximum forward rotational speed responsive to the throttle  92  being in the maximum forward throttle position  108  and the condition sensor  138  generating a signal indicating the absence of the condition of the patient transport apparatus  20 . The controller  126  is further configured to operate the auxiliary wheel drive system  90  using the first speed mode  134  to permit the backward rotational speed of the auxiliary wheel  64  to reach the maximum backward rotational speed responsive to the throttle  92  being in the maximum backward throttle position  112  and the condition sensor  138  generating the signal indicating the absence of the condition of the patient transport apparatus  20 . 
     In one exemplary version, the condition sensor  138  comprises an obstacle detection sensor coupled to the controller  126  and the base  24 . The obstacle detection sensor is configured to generate a signal indicating the presence or absence of obstacles in close proximity to the base  24 . 
     When the obstacle detection sensor generates a signal indicating the absence of an obstacle, the controller  126  is configured to operate the auxiliary wheel drive system  90  using the first speed mode  134  and when the user moves the throttle  92  from the neutral throttle position N to the maximum forward throttle position  108 , the controller  126  operates the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  at the maximum forward rotational speed. 
     When the obstacle detection sensor generates a signal indicating the presence of an obstacle, the controller  126  is configured to operate the auxiliary wheel drive system  90  using the second speed mode  136  and when the user moves the throttle  92  from the neutral throttle position N to the maximum forward throttle position  108 , the controller  126  operates the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  at the intermediate forward rotational speed. 
     In another exemplary version, the condition sensor  138  comprises a proximity sensor configured to generate a signal indicating the presence or absence of an external device such as a patient warning system, an IV pole, a temperature management system, etc. When the proximity sensor generates a signal indicating the presence of the external device, the controller  126  is configured to operate the auxiliary wheel drive system  90  using the second speed mode  136 . When the proximity sensor generates a signal indicating the absence of the external device, the controller  126  is configured to operate the auxiliary wheel drive system  90  using the first speed mode  134 . 
     In some versions, the proximity sensor may be configured to generate the signal responsive to the external device being coupled to the patient transport apparatus  20  to indicate a presence. For example, the proximity sensor may be coupled to the patient support deck  30 . When an IV pole is coupled to the patient support deck  30 , the proximity sensor generates a signal indicating the IV pole is coupled to the patient support deck  30  and the controller  126  is configured to operate the auxiliary wheel drive system  90  using the second speed mode  136 . When the IV pole is removed from the patient support deck  30 , the proximity sensor generates a signal indicating the IV pole has been removed from the patient support deck  30  and the controller  126  is configured to operate the auxiliary wheel drive system  90  using the first speed mode  134 . 
     In the illustrated version, the power source  104  comprises the battery power supply  128  (shown schematically in  FIG.  10   ) to permit the patient transport apparatus  20  to be supplied with power during transport. In many versions, the patient transport apparatus  20  comprises an electrical cable  156  (shown in  FIG.  11   ) coupled to the controller  126  and configured to be coupled to the external power source  140  (e.g., plugged in) to charge the battery power supply  128  and provide power for other functions of the patient transport apparatus  20 . 
     In another exemplary version, the condition sensor  138  is configured to generate a signal indicating the presence or absence of the controller  126  receiving power from the external power source  140 . When the condition sensor  138  generates a signal indicating the controller  126  is receiving power from the external power source  140 , the controller  126  is configured to operate the auxiliary wheel drive system  90  using the second speed mode  136 . When the condition sensor  138  generates a signal indicating the absence of the controller  126  receiving power from the external power source  140 , the controller  126  is configured to operate the auxiliary wheel drive system  90  using the first speed mode  134 . 
     In another version shown in  FIGS.  6 A and  7   , a speed input device  142  (shown schematically in  FIG.  10   ) is coupled to the controller  126  and configured to be operable between a first setting and a second setting. The speed input device  142  may comprise a switch (see  FIG.  6 A ), piezoelectric element, a touch sensor, or any other suitable input device to switch between the first and second settings. The speed input device  142  may be used in place of the condition sensor  138 . In the first setting, the controller  126  operates the auxiliary wheel drive system  90  using the first speed mode  134 , permitting the auxiliary wheel  64  to rotate at the maximum forward and backward rotational speeds when the throttle  92  is in the maximum forward and backward throttle positions  108 ,  112 , respectively. In the second setting, the controller  126  operates the auxiliary wheel drive system  90  using the second speed mode  136 , limiting the auxiliary wheel  64  to rotate at the intermediate forward and backward rotational speeds when the throttle  92  is in the maximum forward and backward throttle positions  108 ,  112 , respectively. 
     In another version, the controller  126  may be configured to operate the auxiliary wheel drive system  90  using three or more speed modes. The controller  126  may be configured to switch between the speed modes using any combination and number of sensors and/or speed input device settings. 
     In some versions, a speed sensor  144  (shown schematically in  FIG.  10   ) is coupled to the controller  126  to generate a signal responsive to a current speed parameter. The current speed parameter may be obtained by the speed sensor  144  generating a signal responsive to one or more of a current speed of the base  24  moving relative to the floor surface and a current rotational speed of the auxiliary wheel  64 . In another version, the current speed parameter is obtained by the speed sensor  144  generating a signal responsive to movement of a component of the auxiliary wheel drive system  90 . 
     The controller  126  is configured to set a desired speed parameter and adjust the electrical power supplied to the motor  102  to control rotational speed of the auxiliary wheel  64  such that the current speed parameter approximates the desired speed parameter. The motor  102  is operable in response to command signals from the controller  126  to rotate the auxiliary wheel  64 . The controller  126  receives various input signals and has a drive circuit or other drive controller portion that controls voltage and/or current to the motor  102  based on the input signals. 
     In some versions, the controller  126  is configured to determine if the electrical cable  156  is coupled to the external power source  140 . When the controller  126  determines the electrical cable  156  is coupled to the external power source  140 , the controller  126  is configured to operate the auxiliary wheel drive system  90  to limit the number of rotations of the auxiliary wheel  64  to limit the distance the base  24  moves relative to the floor surface. 
     As is depicted schematically in  FIG.  10   , In some versions, the control system  124  comprises the load sensor  152  (also referred to as a “patient load sensor”) coupled to the controller  126 . The load sensor  152  is configured to generate a signal indicating a current weight disposed on the patient support deck  30 . In the examples shown, the load sensor  152  comprises load cells coupled to the controller  126  and arranged to detect and/or measure the weight disposed on the patient support deck  30 . The load cells may be arranged in the base  24 , the intermediate frame  26 , patient support deck  30  or any other suitable location to measure the weight disposed on the patient support deck  30 . 
     The controller  126  is configured to control electrical power supplied to the motor  102  responsive to a signal detected by the controller  126  from the load sensor  152  indicating a current weight such that, for each of the throttle positions, the electrical power supplied to the motor  102  is greater when a first patient of a first weight is being transported on the patient transport apparatus  20  as compared to when a second patient of a second weight, less than the first weight, is being transported. In other words, to maintain a desired speed at any given throttle position, electrical power supplied to the motor  102  increases as weight disposed on the patient support deck  30  increases. Thus, the controller  126  may control voltage and/or current supplied to the motor  102  based on patient weight. 
     When the electrical cable  156  is coupled to the external power source  140 , the range of movement of the base  24  relative to the floor surface is limited by a length of the electrical cable  156 . Moving the base  24  past the range of movement will apply tension to the electrical cable  156  and ultimately decouple the electrical cable  156  from the external power source  140  (e.g., become unplugged). In some instances, the user may seek to move the base  24  relative to the floor surface while keeping the electrical cable  156  coupled to the external power source  140 . 
     In some versions, the control system  124  comprises a tension sensor  158  (shown schematically in  FIG.  10   ) coupled to the electrical cable  156  and the controller  126 . The tension sensor  158  is configured to generate a signal indicating tension is being applied to the electrical cable  156  as a result of the controller  126  operating the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  and move the base  24  relative to the floor surface. The controller  126  is configured to operate the auxiliary wheel drive system  90  to stop rotating the auxiliary wheel  64  responsive to the tension sensor  158  generating the signal indicating the tension of the electrical cable  156  exceeds a tension threshold. 
     In some versions, the electrical cable  156  is coupled to one of the base  24  and the intermediate frame  26 . The tension sensor  158  is disposed at a first sensor location S 1  (see FIG.  11 ) at a point on an exterior of the electrical cable  156 . The tension sensor  158  (e.g., strain gauge) generates a signal indicating the amount of tension on the electrical cable  156  and the controller  126  determines whether the tension is above the threshold to determine whether to operate the auxiliary wheel drive system  90  to stop rotating the auxiliary wheel  64 . 
     In another version, the tension sensor  158  is disposed at a second sensor location S 2  (see  FIG.  11   ) at a point between a plate  160  that is fixed to the electrical cable  156  and a surface  162  of the base  24 . The tension sensor  158  (e.g., pressure sensor) generates a signal indicating an amount of pressure between the plate  160  and the surface  162  resulting from tension on the electrical cable  156  and the controller  126  relates the pressure with a tension to determine whether the tension is above the threshold to determine whether to operate the auxiliary wheel drive system  90  to stop rotating the auxiliary wheel  64 . Each of the sensors  88 ,  100 ,  138 ,  144 ,  152 ,  158  described above may comprise one or more of a force sensor, a load cell, a speed radar, an optical sensor, an electromagnetic sensor, an accelerometer, a potentiometer, an infrared sensor, a capacitive sensor, an ultrasonic sensor, a limit switch, or any other suitable sensor for performing the functions recited herein. Other configurations are contemplated. 
     In some versions, the controller  126  is configured to operate one or both the brake actuators  116 ,  120  to brake the auxiliary wheel  64  or one or more support wheels  56  when the controller  126  determines the base  24  has moved a predetermined distance or when the tension sensor  158  generates a signal indicating the tension of the electrical cable  156  approaches the tension threshold. 
     In some versions, the user feedback device  132  is further configured to indicate to the user whether the electrical cable  156  is coupled to the external power source  140  or whether the electrical cable  156  is about to be decoupled from the external power source  140 . In an exemplary version, an (visual, audible, and/or tactile) alarm may trigger if the base  24  has moved the predetermined distance while the electrical cable  156  is plugged in or tension of the electrical cable  156  approaches the tension threshold. 
     Referring now to  FIGS.  12 - 16 C , another version of the first handle  52  (hereinafter referred to as “the handle  52 ”) and the throttle assembly  93  is generally depicted. As is best depicted in  FIGS.  13 - 15   , the handle body  55  has a shell-like configuration defined by first and second handle body members  55   a ,  55   b  which interlock, clamp, or otherwise operatively attach to the inner support  53  via one or more fasteners  164 . Here, the inner support  53  comprises a tubular member  166  has a generally hollow, cylindrical profile which defines the central axis C and generally facilitates connection of the handle  52  and the throttle assembly  93  to the intermediate frame  26  or another portion of the patient transport apparatus  20  (connection not shown in detail). In the illustrated version, an interface sensor board  168  is supported within the tubular member  166 . The interface sensor board  168  is disposed in communication with the controller  126  of the control system  124  via a harness  170  and, as is described in greater detail below, generally supports the user interface sensors  88 ,  88 A. Here, the interface sensor board  168  is secured to the first handle body member  55   a  of the handle body  55  via fasteners  164  which extend through clearance apertures  172  formed in the tubular member  166  of the inner support  53 . 
     With continued reference to  FIGS.  13 - 15   , in the illustrated version, the throttle assembly  93  also comprises a bearing subassembly  174  to facilitate rotation of the throttle  92  about the central axis C to move from the neutral throttle position N (see  FIGS.  8 A and  16 A ) to the various operating throttle positions  107  such as: the maximum forward throttle position  108  (see  FIGS.  8 C and  16 B ) or another forward throttle position  111  defined by rotation from the neutral throttle position N in the first direction  94 ; or the maximum backward throttle position  112  (see  FIGS.  8 F and  16 C ) or another backward throttle position  115  defined by rotation from the neutral throttle position N in the second direction  96 . To this end, the bearing subassembly  174  generally comprises a coupling body  176  and a bearing  178 . Here, the coupling body  176  forms part of the inner support  53  and is operatively attached to the tubular member  166  of the inner support  53  via one or more fasteners  164 . The coupling body  176  supports the bearing  178  which, in turn, rotatably supports the throttle  92  for rotation about the central axis C so as to facilitate rotational movement of the throttle  92  relative to the handle body  55  from the neutral throttle position N to the one or more operating throttle positions  107 . As is described in greater detail below, the coupling body  176  of the inner support  53  also supports the throttle biasing element  91  via a keeper plate  180 . 
     In order to facilitate axial retention of the throttle  92 , a retainer  182  comprising a retainer plate  184  and one or more retainer braces  186  secures to the coupling body  176  via one or more fasteners  164  such that at least a portion of the throttle  92  arranged along the central axis C is secured between the retainer plate  184  and the coupling body  176  (see also  FIG.  15   ). In the illustrated version, a light guide  188  is provided, and includes a guide plate  190  and a guide extension  192  interposed in engagement between the retainer plate  184  and the throttle  92 . To this end, the guide plate  190  comprises one or more guide apertures  194  through which the retainer braces  186  extend. Similarly, the throttle  92  in this version comprises one or more arc slots  196  (see  FIG.  13   ; see also  FIGS.  16 A- 16 C ) through which the retainer braces  186  extend. Here, the arc slots  196  are shaped and arranged to limit rotation of the throttle  92  about the central axis C between the maximum forward throttle position  108  (see  FIG.  16 B ) and the maximum backward throttle position  112  (see  FIG.  16 C ). 
     The retainer plate  184  also comprises a retainer aperture  198  and one or more retainer indexing features  200  (see  FIG.  13   ) which facilitate attachment of an end cap  202  to the retainer  182 . More specifically, and as is best depicted in  FIG.  14   , the end cap  202  comprises one or more cantilevered fingers  204  that extend into the retainer aperture  198  and secure against the retainer plate  184 , and one or more end cap indexing features  206  that are shaped and arranged to engage in the retainer indexing features  200  so as to “clock” or otherwise align the end cap  202  with the retainer  182  about the central axis C. 
     Referring now to  FIGS.  13 - 16 C , the throttle assembly  93  comprises a throttle position sensor, generally indicated at  208 , which is interposed between the throttle  92  and the handle body  55  and is disposed in communication with the controller  126  (e.g., via electrical communication as depicted schematically in  FIG.  10   ) to determine movement of the throttle  92  about the central axis C between the neutral throttle position N (see  FIG.  16 A ) and the one or more operating throttle positions  107  (see  FIGS.  16 B- 16 C ). Here, the throttle position sensor  208  (also referred to herein as “throttle sensor”) detects the current position of the throttle  92  and generates a position signal used by the controller  126  to facilitate operation of the auxiliary wheel drive system  90 . To this end, in the illustrated version, the throttle position sensor  208  comprises an emitter  210  coupled to the throttle  92  for concurrent movement therewith, and a detector  212  operatively attached to the inner support  53  for determining the position of the emitter  210  relative to the detector  212  as the throttle  92  moves between the neutral throttle position N (see  FIG.  16 A ) and the one or more operating throttle positions  107  (see  FIGS.  16 B- 16 C ). 
     In some versions, based on the position of the throttle  92 , the controller  126  may be configured to determine a rotational speed of the throttle  92  via signals generated by the throttle position sensor  208 . Once the controller  126  detects the signal, the controller  126  may be configured to determine one or more resistance parameters RP 1 , RP 2  based on sensed movement of the throttle  92  relative to the handle  52 . As will be appreciated from the subsequent description below, depending on the specific configuration of the damper assembly  95 , the controller  126  may be configured to adjust torque generated by the damper assembly  95  in various ways. Other configurations are contemplated. 
     The controller  126  is coupled to both the auxiliary wheel drive system  90  and the detector  212  of the throttle position sensor  208  (see  FIG.  10   ), and is configured to operate the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  in the forward direction FW (see  FIG.  5 C ) when the throttle  92  is moved in the first direction  94  based on the detector  212  determining movement of the emitter  210  with the throttle  92  from the neutral throttle position N (see  FIG.  16 A ) to the one or more forward throttle positions  111  (see  FIG.  16 B ). The controller  126  is also configured to operate the auxiliary wheel drive system  90  to rotate the auxiliary wheel  64  in the rearward direction RW (see  FIG.  5 C ) when the throttle  92  is moved in the second direction  96  based on the detector  212  determining movement of the emitter  210  with the throttle  92  from the neutral throttle position N (see  FIG.  16 A ) to the one or more backward throttle positions  115  (see  FIG.  16 C ). 
     With continued reference to  FIGS.  13 - 16 C , in the illustrated version, the emitter  210  is configured to generate a predetermined magnetic field, and the detector  212  is responsive to predetermined changes in magnetic fields to determine a relative position of the emitter  210  as the throttle  92  moves from the neutral throttle position N to the one or more operating throttle positions  107 . To this end, the detector  212  is realized as a Hall-effect sensor in the illustrated version and is supported on a throttle circuit board  214  disposed in communication with the interface sensor board  168  via a connector  216 . As described in greater detail below, the interface sensor board  168  is coupled to or otherwise disposed in electrical communication with the controller  126  (e.g., via wired electrical communication across the harness  170 ). 
     The throttle circuit board  214  is operatively attached to the coupling body  176  via one or more fasteners  164  (see  FIG.  13   ), and also supports one or more light modules  218  (e.g., single and/or multi-color light emitting diodes LEDs). The light modules  218  and the light guide  188  cooperate to define a status indicator  220  driven by the controller  126  in the illustrated version to communicate various changes in status of the auxiliary wheel drive system  90  to the user. The controller  126  is generally configured to selectively drive the one or more light modules  218  to emit light through the light guide  188  which, as noted above, is operatively attached to the inner support  53  adjacent to the throttle  92 . Here, the light guide  188  is configured to direct light emitted by the one or more light modules  218  of the status indicator  220  in a direction facing away from the central axis C. To this end, the one or more light modules  218  are arranged so as to selectively emit light in a direction generally parallel to or otherwise along the central axis C. In the illustrated version, the emitter  210  has a substantially annular profile defining an emitter void  222  shaped to permit light emitted by the one or more light modules  218  to pass through the emitter void  222 . 
     As is best depicted in  FIG.  15   , at least a portion of the light guide  188  (e.g., the guide extension  192 ) extends into or otherwise through the emitter void  222  of the emitter  210 . Here, it will be appreciated that the emitter  210  is not disposed in contact with the light guide  188  and moves concurrently with the throttle  92  about the central axis C relative to the light guide  188  which, as noted above, is operatively attached to the inner support  53  of the handle  52  and is therefore fixed relative to the central axis C. With this arrangement, the throttle  92  similarly comprises a throttle void  224  in which the emitter  210  is supported such that at least a portion of the light guide  188  (e.g., the guide extension  192 ) also extends into or otherwise through the throttle void  224 . While the emitter  210  has a substantially annular profile as noted above, this annular profile also comprises a transverse notch  226  that abuts a corresponding flat  228  formed in the throttle void  224  of the throttle  92 . This arrangement “clocks” the emitter  210  relative to the throttle  92  and helps facilitate concurrent movement between the emitter  210  and the throttle  92  about the central axis C. It will be appreciated that other configurations are contemplated for the emitter  210  besides those illustrated throughout the drawings. By way of non-limiting example, while the illustrated emitter  210  is realized as a magnet with an annular profile, in other versions the emitter  210  could be an insert with a cylindrical or other profile, manufactured from magnetic materials or other materials (e.g., steel), that is coupled directly to the throttle  92  or is coupled to a carrier (e.g., an annular ring made from plastic that is shaped similarly to the illustrated annular emitter  210 ) that is, in turn, coupled to the throttle  92 . Other configurations are contemplated. Furthermore, it will be appreciated that certain versions described in the present disclosure could employ differently-configured throttle position sensors  208 , realized with similar emitter/detector arrangements or with other sensor types, styles, and configurations (e.g., one or more potentiometers, encoders, and the like). Other configurations are contemplated. 
     Referring again to  FIGS.  13 - 15   , in the illustrated version, the inner support  53  of the handle  52  defines a distal support end  230  and an opposing proximal support end  232 . Here, the distal support end  230  is defined by a portion of the coupling body  176 , and the proximal support end  232  is defined by a portion of the tubular member  166 . Moreover, the handle body  55  defines a distal handle body end  234  and an opposing proximal handle body end  236 . As noted above, the handle body  55  is defined by the first and second handle body members  55   a ,  55   b  in the illustrated version, either or both of which define the distal and proximal handle body ends  234 ,  236 . Furthermore, the throttle  92  defines a distal throttle end  238  and an opposing proximal throttle end  240  with a throttle chamber  242  (see  FIG.  14   ) formed extending from the proximal throttle end  240  toward the distal throttle end  238 . It will be appreciated that the throttle void  224  and the arc slots  196  of the throttle  92  are arranged adjacent to the distal throttle end  238  (see  FIG.  13   ) such that the emitter  210  is coupled to the throttle  92  adjacent to the distal throttle end  238  and the detector  212  is arranged at least partially within the throttle chamber  242 . In addition, and as is best depicted in  FIG.  15   , the bearing  178  is disposed in the throttle chamber  242  between the distal and proximal throttle ends  238 ,  240 , and is arranged along the central axis C between the distal support end  230  (defined by the coupling body  176  of the inner support  53  as noted above) and the distal handle body end  234 . As such, the inner support  53  extends at least partially into the throttle chamber  242  such that the proximal throttle end  240  is arranged between the distal and proximal support ends  230 ,  232 . Here, it will be appreciated that the bearing  178  is completely disposed within the throttle chamber  242 . This configuration helps ensure long life of the bearing  178  in that foreign contaminants such as dirt, liquids, and the like cannot readily enter into the throttle chamber  242  and travel toward the bearing  178  to otherwise cause inconsistent or degraded performance of the throttle assembly  93 . In the illustrated version, the bearing  178  is realized with a single, elongated needle bearing that is shaped and arranged to both facilitate rotation of the throttle  92  about the central axis C and also to ensure that force applied in directions generally transverse to the central axis C (e.g., via force applied to the throttle  92 ) do not result in deteriorated performance over time (e.g., bearing “slop” or “play”). 
     As shown in  FIG.  15   , the distal handle body end  234  of the handle body  55  is arranged between the distal and proximal throttle ends  238 ,  240  of the throttle  92  such that at least a portion of the handle body  55  is also disposed within the throttle chamber  242  adjacent to the bearing  178 . Here, the throttle chamber  242  defines a proximal chamber region  244  having a proximal chamber diameter  246  (see  FIG.  14   ), and the handle body  55  defines a distal pilot region  248  formed adjacent to the distal handle body end  234  and having a distal pilot diameter  250  (see  FIG.  14   ) smaller than the proximal chamber diameter  246 . This configuration defines a gap region, generally indicated at  252  in  FIG.  15   . Here, the throttle  92  further comprises a drip channel, generally indicated at  254 , formed extending from the proximal throttle end  240  into communication with the gap region  252  and arranged to promote egress of contaminants entering into the gap region  252 . As shown in  FIG.  14   , the drip channel  254  is “recessed” and has a larger diameter than the proximal chamber diameter  246  (not shown in detail). This configuration helps direct any contaminants out of the throttle chamber  242  that might enter into the gap region  252  during use. In some versions, the drip channel  254  is shaped and/or arranged such that movement of the handle  52  between the use position PU and the stow position PS (see  FIG.  1   ) promotes egress of contaminants from the gap region  252 . In some versions, one or more gaskets, seals, O-rings, and the like (not shown) may be provided in the throttle chamber  242 , or in other portions of the throttle assembly  93  and/or handle  52 , to further inhibit egress of contaminants toward the bearing  178 , the interface sensor board  168 , the throttle circuit board  214 , and/or other components or structural features. Other configurations are contemplated. 
     Referring now to  FIGS.  14 - 15   , as noted above, the throttle biasing element  91  is interposed between the throttle  92  and the inner support  53  to urge the throttle toward the neutral throttle position N. To this end, and in the illustrated version, the throttle biasing element  91  is realized as a torsion spring with first and second tangs  256 ,  258  that are each arranged to engage against a keeper stop element  260  formed on the keeper plate  180 , and also against respective first and second throttle stop elements  262 ,  264  formed in the drip channel  254  of the throttle  92 . Thus, the throttle biasing element  91  permits the throttle  92  to rotate about the central axis C in either of the first and second directions  94 ,  96  (see  FIG.  12   ) as the user rotates the throttle  92  to the operating throttle positions  107  (see  FIGS.  16 B- 16 C ), and biases, urges, or otherwise promotes movement of the throttle  92  back toward the neutral throttle position N (see  FIG.  16 A ) in an absence of applied force to the throttle  92  by the user. 
     Referring now to  FIGS.  12 - 15   , the illustrated version similarly employs one or more user interface sensors  88 ,  88 A in communication with the controller  126  to determine engagement by the user with the throttle assembly  93  in order to, among other things, enable or disable rotation of the auxiliary wheel  64  via the auxiliary wheel drive system  90  and/or raise or lower the auxiliary wheel  64  relative to the support structure  22  via the lift actuator  66  based on determining engagement with the user as described in greater detail above in connection with  FIGS.  1 - 10   . However, in this version, and as is best depicted in  FIG.  15   , the handle body  55  of the handle  52  defines an outer housing surface  266  configured to be gripped by the user and an inner housing surface  268  disposed adjacent to the inner support  53 , and the user interface sensor  88  comprises a first conductive element  270  and a first sensor controller  272 . The first conductive element  270  is coupled to the inner housing surface  268  of the first handle body member  55   a , and is disposed in electrical communication with the first sensor controller  272  as described in greater detail below. 
     In the illustrated version, the first sensor controller  272  is supported on the interface sensor board  168 , is coupled to the controller  126  (e.g., via wired electrical communication across the harness  170 ), and is configured to generate a first electrostatic field  274  with the first conductive element  270  to determine engagement of the throttle assembly  93  by the user in response to contact with the outer housing surface  266  adjacent to (but spaced from) the first conductive element  270  that nevertheless interacts with the first electrostatic field  274 . Here, the outer housing surface  266  acts as an insulator (manufactured such as from plastic or another material configured for electrical insulation), and the user&#39;s hand acts as a conductor such that engagement therebetween results in a measurable capacitance that can be distinguished from an absence of user engagement with the first electrostatic field  274 . Those having ordinary skill in the art will appreciate that this arrangement provides the user interface sensor  88  with a “solid state” capacitive-touch type configuration, which helps promote consistent determination of user engagement without requiring physical contact with electrical components. Here too, it will be appreciated that this configuration allows the various components of the user interface sensor  88  to remain out of physical contact with the user and generally unexposed to the environment. 
     Here too in this version, the auxiliary user interface sensor  88   a  is similarly provided to determine engagement by the user separate from the determination by the user interface sensor  88 . More specifically, in this version, the user interface sensor  88  is arranged to determine user engagement with the handle body  55 , whereas the auxiliary user interface sensor  88   a  is arranged to determine user engagement with the throttle  92 . While similar in arrangement to the previously-described versions depicted in  FIGS.  6 A- 7    in that the auxiliary user interface sensor  88   a  can be utilized to determine engagement adjacent to the thumb throttle interface  98   a  and/or the finger throttle interface  98   b , in this version the auxiliary user interface sensor  88   a , similar to the user interface sensor  88 , comprises a second conductive element  276  coupled to the inner housing surface  268  of the first handle body member  55   a  adjacent to the distal handle body end  234 . 
     The second conductive element  276  is disposed in electrical communication with a second sensor controller  278 , which is likewise supported on the interface sensor board  168  and is coupled to the controller  126  (e.g., via wired electrical communication across the harness  170 ). Here, the second sensor controller  278  is configured to generate a second electrostatic field  280  with the second conductive element  276  to determine engagement of the throttle assembly  93  by the user in response to contact with the outer housing surface  266  adjacent to (but spaced from) the second conductive element  276  that nevertheless interacts with the second electrostatic field  280 . 
     As shown in  FIG.  15   , the first and second conductive elements  270 ,  276  are each realized by respective areas of conductive coating applied to the inner housing surface  268  of the first handle body member  55   a  of the handle body  55 . As noted above, the tubular member  166  of the inner support  53  is provided with clearance apertures  172  through which fasteners  164  extend in order to secure the interface sensor board  168  to the first handle body member  55   a . More specifically, in the illustrated version, the first handle body member  55   a  comprises first and second bosses  282 ,  284  which depend from the inner housing surface  268  and into which the fasteners  164  extend (e.g., in threaded engagement). Here, the conductive coatings that respectively define the first and second conductive elements  270 ,  276  are applied both to the inner housing surface  268  as well as to the first and second bosses  282 ,  284  used to secure the interface sensor board  168 . Here, the interface sensor board  168  is provided with first and second pads  286 ,  288  which respectively contact the conductive coatings applied to the first and second bosses  282 ,  284 . The first and second pads  286 ,  288  are respectively coupled (e.g., disposed in electrical communication via a soldered connection) to the first and second sensor controllers  272 ,  278 , thereby facilitating electrical communication with the first and second conductive elements  270 ,  276  via attachment of the interface sensor board  168  to the first handle body member  55   a . Because the first and second bosses  282 ,  284  have the conductive coating applied to facilitate electrical communication, the clearance apertures  172  of the tubular member  166  are sized larger than the first and second bosses  282 ,  284  to prevent electrical contact therebetween (e.g., which might otherwise occur with metallic tubular members  166  manufactured such as from steel). 
     As noted above, the controller  126  is disposed in electrical communication with the interface sensor board  168  and also with the throttle circuit board  214  via the harness  170  such that the controller  126  is not necessarily disposed within the handle  52  and may be coupled to other portions of the patient transport apparatus  20  (see also  FIG.  10   ). Similar to the controller  126 , the first and second sensor controllers  272 ,  278  may be of a number of different types, styles, and/or configurations, defined by one or more electrical components such as processors, integrated circuits, and the like. In some versions, the first and second sensor controllers  272 ,  278  may be realized with a common electrical component (e.g., via separate I/O connections of the same processor, integrated circuit, and the like). In some versions, the first and second sensor controllers  272 ,  278  may not necessarily be supported on the interface sensor board  168 . Similarly, in some versions, the first and second sensor controllers  272 ,  278  may be realized directly by the controller  126  (e.g., via separate I/O connections of the controller  126 ) rather than being coupled in communication with the controller  126 . Other configurations are contemplated. 
     Furthermore, it will be appreciated that the controller  126  can directly or indirectly use the first and second sensor controllers  272 ,  278  to facilitate detecting, sensing, or otherwise determining user engagement with the handle body  55  and the throttle  92 , respectively, of the throttle assembly  93  in a number of different ways, and can control operation of a number of different aspects of the patient transport apparatus  20  based on engagement with one or both of the user interface sensors  88 ,  88 A based on communication with the first and second sensor controllers  272 ,  278  (e.g., electrical signals of various types). In some versions, the controller  126  is configured to operate the auxiliary wheel drive system  90  (see  FIGS.  5 A- 5 C ) in response to movement of the throttle  92  from the neutral throttle position N (see  FIGS.  8 A and  16 A ) to the one or more operating throttle positions  107  (see  FIGS.  8 C,  8 F, and  16 B- 16 C ) determined by the detector  212  of the throttle position sensor  208  during engagement simultaneously with the handle body  55  determined by the user interface sensor  88  and with the throttle  92  determined by the auxiliary user interface sensor  88   a . Put differently, the controller  126  may be configured to “ignore” movement of the throttle  92  or otherwise inhibit operation of the auxiliary wheel drive system  90  during an absence of engagement by the user with the throttle assembly  93  simultaneously determined by the user interface sensor  88  and the auxiliary user interface sensor  88   a . Thus, in some versions, the controller  126  will not drive the auxiliary wheel  64  via the motor  102  unless the user engages both the handle body  55  and the throttle  92  (e.g., at one of the thumb and throttle interfaces  98   a ,  98   b ). Other configurations are contemplated. 
     In the representative version depicted herein, and as is best depicted in  FIGS.  16 A- 16 C , the throttle assembly  93  is configured such that rotation of the throttle  92  in the first (forward) direction  94  from the neutral throttle position N to the maximum forward throttle position  108  moves the throttle  92  about the central axis C in an angular amount that is substantially the same as occurs during rotation of the throttle  92  in the second (backward) direction  96  from the neutral throttle position N to the maximum backward throttle position  112 . However, in some versions, the throttle assembly  93  may be configured to facilitate a larger angular amount of rotation of the throttle  92  from the neutral throttle position N to the maximum forward throttle position  108  than from the neutral throttle position N to the maximum backward throttle position  112 . In some versions, the throttle assembly  93  or other portions of the patient transport apparatus  20  may be similar to as is disclosed in International Patent Application No. PCT/US2021/034631 filed on May 27, 2021, entitled “Patient Transport Apparatus with Asymmetric Throttle Assembly,” the disclosure of which is hereby incorporated by reference in its entirety. Other configurations are contemplated. 
     In some versions, the controller  126  is configured to operate the lift actuator  66  (see  FIGS.  5 A- 5 C ) in order to move the auxiliary wheel  64  from the retracted position  70  (see  FIG.  5 A ) to the deployed position  68  (see  FIG.  5 C ) in response to engagement by the user with at least one of the handle body  55  determined by the user interface sensor  88  and the throttle  92  determined by the auxiliary user interface sensor  88   a . Put differently, the controller  126  may be configured to drive the lift actuator  66  so as to move the auxiliary wheel  64  toward the deployed position  68  when the user engages either the throttle  92  and/or the handle body  55 . However, in some versions, even though the controller  126  may move the auxiliary wheel  64  to the deployed position  68  when the user engages only one of the throttle  92  and the handle body  55 , rotation of the auxiliary wheel  64  via the motor  102  may remain interrupted, disabled, or otherwise prevented in response to rotation of the throttle  92  determined via the throttle position sensor  208  until the controller  126  has determined that the user is engaging both the throttle  92  and the handle body  55 . Other configurations are contemplated. 
     In some versions, the controller  126  is configured to maintain the auxiliary wheel  64  in the deployed position  68  (see  FIG.  5 C ) in response to continued engagement by the user with the throttle assembly  93  determined by the user interface sensor  88  and/or by the auxiliary user interface sensor  88   a . Conversely, in some versions, the controller  126  is configured to operate the lift actuator  66  to move the auxiliary wheel  64  from the deployed position  68  toward the retracted position  70  during an absence of engagement by the user with either the handle body  55  determined by the user interface sensor  88  and/or with the throttle  92  determined by the auxiliary user interface sensor  88   a . Put differently, if the controller  126  moves the auxiliary wheel  64  to the deployed position  68  in response to determining user engagement with the throttle assembly  93 , and if the user subsequently disengages the throttle assembly  93  altogether, then the controller  126  may be configured to return the auxiliary wheel  64  to the retracted position  70  in response to sensing complete disengagement of the throttle assembly  93 . However, in some versions, the controller  126  may also move the auxiliary wheel  64  to the retracted position  70  (or to one of the intermediate positions  71 ) in response to detecting partial user disengagement of the throttle assembly  93  (e.g., determining disengagement with the throttle  92  but not the handle body  55 , or vice-versa). Here too, other configurations are contemplated. 
     As noted above, the controller  126  utilizes the auxiliary wheel position sensor  146  to determine the relative position of the auxiliary wheel  64  between the deployed position  68  (see  FIG.  5 C ), the retracted position  70  (see  FIG.  5 A ) and the intermediate positions  71  therebetween (see  FIG.  5 B ). Accordingly, the controller  126  is also able to determine movement of the auxiliary wheel  64  via the auxiliary wheel position sensor  146  (e.g., while driving the lift actuator  66 ). 
     Referring now to  FIGS.  13 - 17   , as noted above, the throttle assembly  93  of the present disclosure employs the damper assembly  95  interposed between the throttle  92  and the handle  52  to provide torque resisting rotation of the throttle  92  as the throttle  92  rotates relative to the handle  52 . In the representative version illustrated herein, and as is best depicted in  FIGS.  13 - 15   , the damper assembly  95  is at least partially disposed within the throttle chamber  242  and generally includes a damper body  290  and a damper divider  292  arranged for rotational movement relative to the damper body  290 . In the illustrated versions, the damper body  290  includes a plurality of damper tangs  294  supporting respective fasteners  164  (e.g., rivets; not shown in detail) which engage respective damper mounts  296  formed in the throttle  92  adjacent to (and spaced radially between) the arc slots  196  to operatively attach the damper assembly  95  to the throttle  92 . Here too in the illustrated version, the damper divider  292  includes a damper interface  298  shaped to engage a correspondingly-shaped handle interface  300  of the handle  52  to operatively attach the damper assembly  95  to the handle  52 . To this end, the damper interface  298  is realized as a “socket” with a square-shaped profile which engages a similarly-shaped handle interface  300  which is realized as a “peg” that can be inserted into the damper interface  298  along the central axis C. However, it will be appreciated that other configurations are contemplated, and the various shapes and arrangements of the damper interface  298  and/or the handle interface  300  may be employed. 
     In the illustrated version, the handle interface  300  is defined by the guide extension  192  of the light guide  188  which, as noted above, is operatively attached to the handle  52  via the fasteners  164  and the retainer braces  186  supported by the retainer  182  which are disposed in threaded engagement with the coupling body  176 . Here too, it will be appreciated that other configurations are contemplated. In some versions, the arrangement described above could be interchanged (e.g., with the damper body  290  operatively attached to the handle  52  rather than to the throttle  92 , and with the damper divider  292  operatively attached to the throttle  92  rather than to the handle  52 ). Furthermore, while the damper assembly  95  is illustrated as being arranged along the central axis C between the light guide  188  and the portion of the throttle  92  supporting the emitter  210  in the illustrated version, other configurations are contemplated, and it will be appreciated that the damper assembly  95  could be arranged, disposed, or otherwise supported in other ways sufficient to facilitate providing torque used to resist rotation of the throttle  92  relative to the handle  52 . By way of non-limiting example, the damper assembly  95  could be supported on the coupling body  176  (e.g., adjacent to the bearing  178 ). Moreover, the damper assembly  95  could be supported offset from the central axis C (e.g., via a geartrain or similar rotational interface; not shown). In addition, while a single damper assembly  95  is depicted throughout the drawings, it will be appreciated that more than one damper assembly  95  could be employed. Other configurations are contemplated. 
     In some versions, the damper assembly  95  may be configured to facilitate adjustment of one or more resistance parameters RP by the controller  126 , as is described in greater detail below. In some versions, the damper assembly  95  may be configured to facilitate manual adjustment of one or more resistance parameters RP, and/or may be “pre-set” to provide torque according to predetermined resistance parameters RP. In some versions, the damper assembly  95  may not be adjustable. It will be appreciated that various styles, types, and configurations of damper assemblies  95  are contemplated by the present disclosure, which may be configured to provide torque to resist rotation according to one or more resistance parameters RP based on hydraulic, pneumatic, frictional, electrorheological, magnetorheological, electrically controlled, and/or magnetic particle damping/clutching strategies, or any combinations thereof. Other configurations are contemplated. 
     With continued reference to  FIGS.  13 - 17   , in the illustrated version, the damper body  290  extends between a distal damper end  302  and a proximal damper end  304  with a damper chamber  306  formed extending from the proximal damper end  304  towards the distal damper end  302 . The damper divider  292  is at least partially disposed within the damper chamber  306 . In some versions, the damper chamber  306  is at least partially filled with a working fluid  308  (see  FIG.  17   ), and the damper divider  292  is configured to displace working fluid  308  to facilitate providing the torque resisting rotation of the throttle  92  or to otherwise change damping characteristics of the damper assembly  95 . In some versions, the working fluid  308  may be realized as a hydraulic fluid. However, as will be appreciated from the subsequent description below, other types of working fluids  308  are contemplated. Furthermore, it will be appreciated that the damper assembly  95  may be configured to operate in other ways, such as without working fluid  308  (e.g., based on non-fluidic frictional engagement, magnetic resistance, and the like). 
     As shown in  FIG.  15   , in some versions, the damper body  290  may define one or more separators  310  arranged extending into the damper chamber  306 , and the damper divider  292  may include one or more vanes  312  likewise disposed in the damper chamber  306  and arranged relative to the separators  310  to, among other things, partition the damper chamber  306  into a plurality of chamber regions  314   a ,  314   b ,  314   c ,  314   d . Here, it will be appreciated that various arrangements and quantities of chamber regions  314   a ,  314   b ,  314   c ,  314   d  may be employed, and may be filled with different types of working fluids  308  (e.g., with different viscosities), or may be left empty (e.g., without working fluid  308 ) to facilitate adjusting, setting, or otherwise defining the resistance parameter RP and/or other damping characteristics of the damper assembly  95 . In some versions, the separators  310  and/or the vanes  312  may be configured to permit working fluid  308  to pass between adjacent chamber regions  314   a ,  314   b ,  314   c ,  314   d  at predetermined rates. Here, beyond adjusting the geometry and arrangement of the damper chamber  306 , the damper divider  292 , the separators  310 , and/or the vanes  312  to facilitate the flow of working fluid  308  between adjacent chamber regions  314   a ,  314   b ,  314   c ,  314   d , in some versions, the damper assembly  95  may employ orifices, valves, ports, seals, and the like (not shown). Other configurations are contemplated. In in the illustrated versions, a damper cover  316  is employed to retain the working fluid  308  within the damper chamber  306 . However, the use of external reservoirs, accumulators, and the like is contemplated by the present disclosure. 
     In some versions, the working fluid  308  may be realized as a “smart fluid” with properties (e.g., viscosity) which can be varied based on interactions an electric field and/or a magnetic field in order to control damping characteristics of the damper assembly  95 . The damper assembly  95  or another component of the throttle assembly  93  may include a damper adjuster  318  to adjust a viscosity of the working fluid  308 , such as where the working fluid  308  is realized as a magnetorheological fluid with a viscosity that can be varied based on changes in a magnetic field generated via an electromagnet, coil, or similar device forming part of the damper adjuster  318 . Here, the controller  126  may be configured to drive the damper adjuster  318  based on one or more determined resistance parameters RP to provide torque resisting rotation of the throttle  92  relative to the handle  52 . 
     In some versions, the damper adjuster  318  or another part of the damping assembly  95  may include various quantities of electromagnetic coils located within or relative to the damper chamber  306  to generate one or more magnetic fields along flow passage(s) within the damper chamber  306 . In some versions, the working fluid  308  may metallic particles, distributed randomly. Here, with the application of electrical current to electromagnetic coil(s) of the damper adjuster  318 , generated magnetic field(s) arrange the particles into or otherwise according to a predetermined pattern which makes the working fluid  308  more (or less) resistant to flow. 
     In some versions, a relationship between the rotational speed of the throttle  92  relative to the handle  52  could be utilized to define target resistance parameters RP used to control the damper adjuster  318  as described in greater detail below. Here, data associated with damping characteristics, acceleration curves, speed profiles, throttle movement ranges, fluid properties, and the like, and/or other relationships or desired correlations described in greater detail below, may be stored in memory  127  and may be predetermined and/or determined (or updated) dynamically. Other configurations are contemplated. 
     In some versions, the controller  126  determines one or more resistance parameters RP based on the sensed movement of the throttle  92  relative to the handle  52  (e.g., rotation at a predetermined speed threshold, rotation between predetermined positions, rotation at predetermined rates, rotation in predetermined directions, and the like). In some versions, the controller  126  is configured to adjust the resistance parameter RP (e.g., to effect corresponding adjustment of the viscosity of the working fluid  308 ) based on a rotational speed of the throttle  92  (e.g., determined via the throttle sensor  208 ) as the throttle  92  rotates about the central axis C relative to the handle  52 . 
     In some versions, the controller  126  is configured to adjust one or more resistance parameters RP as the throttle moves away from the neutral throttle position N. In some versions, the controller  126  is configured to drive the damper adjuster  318  to provide torque resisting rotation of the throttle  92  relative to the handle  52  that is proportional to operation of the wheel  64  of the drive system  90 . Put differently, when operating in the forward direction FW, the range of motion between the neutral throttle position N and the maximum forward throttle position  108  may correspond (e.g., be scaled, offset, and the like) relative to the range of operating velocities of the patient transport apparatus  20  between stopped motion and a maximum forward operating velocity. In some versions, the controller  126  may be configured to define or otherwise determine a plurality of different resistance parameters RP that are associated with particular velocities of the patient transport apparatus  20 , such as to generate different amounts of resistive torque when the patient transport apparatus  20  is stopped (and/or operating at relatively slow speeds) compared to when the patient transport apparatus  20  is moving at relatively high speeds. Other configurations are contemplated. 
     In some versions, the controller  126  may be configured to define or otherwise determine a plurality of different resistance parameters RP that are associated with particular rotational positions of the throttle  92 , such as to generate different amounts of resistive torque when the throttle is at or near the neutral throttle position N (and/or operating at relatively slow speeds) compared to when the throttle  92  is at or near the maximum forward throttle position  108  (and/or the maximum backward throttle position  112 ). In some versions, the controller  126  may be configured to drive the damper adjuster  318  to provide torque according to a forward resistance parameter RP_F to resist rotation of the throttle  92  as the throttle  92  rotates relative to the handle  52  from the neutral throttle position N towards the maximum forward throttle position  108 , and according to a backward resistance parameter RP_B to resist rotation of the throttle  92  as the throttle  92  rotates relative to the handle  52  from the neutral throttle position N towards the maximum backward throttle position  112 . In some versions, the forward resistance parameter RP_F is substantially equal to the backward resistance parameter RP_B. However, other configurations are contemplated, and the forward resistance parameter RP_F could be different from the backward resistance parameter RP_B such that different amounts of resistive torque are applied when operating int he forward direction FW than when operating int he rearward direction RW. 
     It is contemplated that the damper assembly  95  may include any number of damper adjusters  318 , and may provide any type of damping including, but not limited to, viscous damping, dry friction damping, material damping, and/or magnetic damping. Put differently, the damper adjuster  318  may be configured to adjust damping properties of the damper assembly  95  even without the use of working fluids  308 . Other configurations are contemplated. 
     In this way, the versions described herein afford significant advantages in a number of different applications where patient transport apparatuses  20  are utilized. 
     It will be further appreciated that the terms “include,” “includes,” and “including” have the same meaning as the terms “comprise,” “comprises,” and “comprising.” Moreover, it will be appreciated that terms such as “first,” “second,” “third,” and the like are used herein to differentiate certain structural features and components for the non-limiting, illustrative purposes of clarity and consistency. 
     Several versions and configurations have been discussed in the foregoing description. However, the configurations discussed herein are not intended to be exhaustive or limit the invention to any particular form. The terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations are possible in light of the above teachings and the invention may be practiced otherwise than as specifically described.