Patent Publication Number: US-2022227614-A1

Title: Lift device with user contact sensor

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of and priority to U.S. Provisional Application No. 63/140,044, filed on Jan. 21, 2021, the entire disclosure of which is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     The present disclosure relates generally to the field of lift devices. More specifically, the present disclosure relates to sensor systems for lift devices. 
     Some lift devices include platforms that support a user. Such platforms are often supported by boom assemblies that facilitate vertical and/or horizontal movement of the platform as controlled by the user through a user interface. During operation, the user is typically positioned in front of the user interface when the platform is moving. As the boom assembly moves the platform, the platform may approach an obstacle (e.g., a wall, a tree branch, etc.). If the user is positioned between the user interface and the obstacle while the platform moves, the user&#39;s freedom of movement may be restricted. 
     SUMMARY 
     At least one embodiment relates to a lift device including a chassis, a platform configured to support a user, a lift assembly coupling the platform to the chassis, an actuator configured to at least one of (a) move the platform relative to the chassis or (b) propel the chassis, a sensor assembly, and a controller. The sensor assembly includes a rod including a first end portion coupled to the platform and a second end portion opposite the first end portion, a housing defining an aperture sized to receive the second end portion of the rod, and a sensor coupled to the housing and configured to provide a signal in response to the second end portion of the rod exiting the aperture. The controller is operatively coupled to the sensor and the actuator and configured to control the actuator in response to receiving the signal from the sensor. 
     Another embodiment relates to a sensor assembly for a lift device. The sensor assembly includes a bar including a first end portion, a second end portion opposite the first end portion, and a resilient member extending between the first end portion and the second end portion. The sensor assembly further includes a plate configured to be coupled to a platform of the lift device, the plate defining an aperture sized to receive the second end portion of the bar. The sensor assembly further includes a sensor coupled to the plate and configured to provide a signal in response to the second end portion of the bar exiting the aperture. The resilient member is configured to apply a biasing force to resist the second end portion exiting the aperture. 
     Another embodiment relates to a lift device including a chassis, a platform configured to support a user, the platform including a first rail and a second rail, a user interface coupled to the platform and positioned between the first rail and the second rail, a lift assembly coupling the platform to the chassis, an actuator configured to at least one of (a) move the platform relative to the chassis or (b) propel the chassis, a sensor assembly, and a controller. The sensor assembly includes a bar including (a) a first end portion coupled to the first rail, (b) a second end portion opposite the first end portion, and (c) a resilient member extending between the first end portion and the second end portion. The sensor assembly further includes a proximity sensor coupled to the second rail and configured to provide a signal indicative of a distance between the second end portion and the proximity sensor. The proximity sensor is configured to detect the second end portion while the second end portion is separated from the proximity sensor. The controller is operatively coupled to the proximity sensor and the actuator and configured to control the actuator in response to receiving the signal from the proximity sensor. 
     This summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices or processes described herein will become apparent in the detailed description set forth herein, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a front perspective view of a boom lift, according to an exemplary embodiment; 
         FIG. 2  is a top perspective view of a base assembly of the boom lift of  FIG. 1 , with a turntable removed; 
         FIG. 3  is a top perspective view of a portion of the base assembly of  FIG. 2 ; 
         FIG. 4  is a front perspective view of a platform of the boom lift of  FIG. 1 ; 
         FIG. 5  is a block diagram of a control system of the boom lift of  FIG. 1 ; 
         FIG. 6  is rear perspective view of a user interface and a railing of the platform of  FIG. 4  with the user interface in a maintenance position; 
         FIG. 7  is a front, top perspective view of the user interface and the railing of  FIG. 6  with the user interface in a maintenance position; 
         FIG. 8  is a top perspective view of a user contact sensor coupled to the platform of  FIG. 4 ; 
         FIG. 9  is a left perspective view of the user contact sensor of  FIG. 8  and the platform of  FIG. 4 ; 
         FIG. 10  is a top section view of the user contact sensor of  FIG. 8 ; 
         FIGS. 11 and 12  are exploded views of the user contact sensor of  FIG. 8 ; 
         FIGS. 13 and 14  are section views of the user contact sensor of  FIG. 8 ; 
         FIGS. 15, 16, and 17  are various views of a bar assembly of the user contact sensor of  FIG. 8 ; 
         FIGS. 18, 19, 20, and 21  are rear perspective views illustrating a first operating sequence of the platform of  FIG. 4  and the user contact sensor of  FIG. 8 ; and 
         FIGS. 22, 23, and 24  are rear perspective views illustrating a second operating sequence of the platform of  FIG. 4  and the user contact sensor of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     Before turning to the figures, which illustrate certain exemplary embodiments in detail, it should be understood that the present disclosure is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology used herein is for the purpose of description only and should not be regarded as limiting. 
     Referring generally to the figures, a lift device includes a platform configured to support a user, a chassis, and a lift assembly coupling the platform to the chassis. The user may control the lift assembly to raise, lower, or otherwise move the platform through a user interface coupled to the platform. In some situations, it may be possible for an obstacle in the environment to push the user toward the user interface while the lift assembly moves the platform. To limit or prevent this, the platform includes a user contact sensor positioned adjacent the user interface. The user contact sensor includes a bar assembly having a first end that is pivotally coupled to a rail. A second end of the bar assembly is received within a bar aperture of a sensing portion that is coupled to another rail. The bar assembly is positioned such that the upper body of the user will push against the bar assembly if the user is forced toward the user interface. This forces the second end of the bar assembly out of the bar aperture. The sensing portion includes a sensor that detects when the second end of the bar assembly is present within the bar aperture. In response to the sensor detecting that the bar has exited the bar aperture, a controller stops or reverses movement of the lift device. 
     Lift Device 
     Referring to  FIG. 1 , a lifting apparatus, lift device, or mobile elevating work platform (MEWP) (e.g., a telehandler, an electric boom lift, a towable boom lift, a lift device, a fully electric boom lift, etc.), shown as lift device  10  includes a base assembly  12  (e.g., a base, a support assembly, a drivable support assembly, a support structure, a chassis, etc.), a the platform assembly  16  (e.g., a platform, a terrace, etc.), and a lift assembly  14  (e.g., a boom, a boom lift assembly, a lifting apparatus, an articulated arm, a scissors lift, etc.). The lift device  10  includes a front end (e.g., a forward facing end, a front portion, a front, etc.), shown as front  62 , and a rear end (e.g., a rearward facing end, a back portion, a back, a rear, etc.,) shown as rear  60 . The lift assembly  14  is configured to elevate the platform assembly  16  in an upwards direction  46  (e.g., an upward vertical direction) relative to the base assembly  12 . The lift assembly  14  is also configured to translate the platform assembly  16  in a downwards direction  48  (e.g., a downward vertical direction). The lift assembly  14  is also configured to translate the platform assembly  16  in either a forwards direction  50  (e.g., a forward longitudinal direction) or a rearwards direction  51  (e.g., a rearward longitudinal direction). The lift assembly  14  generally facilitates performing a lifting function to raise and lower the platform assembly  16 , as well as movement of the platform assembly  16  in various directions. 
     The base assembly  12  defines a longitudinal axis  78  and a lateral axis  80 . The longitudinal axis  78  defines the forward direction  50  of lift device  10  and the rearward direction  51 . The lift device  10  is configured to translate in the forward direction  50  and to translate backwards in the rearward direction  51 . The base assembly  12  includes one or more wheels, tires, wheel assemblies, tractive elements, rotary elements, treads, etc., shown as tractive elements  82 . The tractive elements  82  are configured to rotate to drive (e.g., propel, translate, steer, move, etc.) the lift device  10 . The tractive elements  82  can each include an electric motor  52  (e.g., electric wheel motors) configured to drive the tractive elements  82  (e.g., to rotate tractive elements  82  to facilitation motion of the lift device  10 ). In other embodiments, the tractive elements  82  are configured to receive power (e.g., rotational mechanical energy) from electric motors  52  or through a drive train (e.g., a combination of any number and configuration of a shaft, an axle, a gear reduction, a gear train, a transmission, etc.). In some embodiments, one or more tractive elements  82  are driven by a prime mover  41  (e.g., electric motor, internal combustion engine, etc.) through a transmission. In some embodiments, a hydraulic system (e.g., one or more pumps, hydraulic motors, conduits, valves, etc.) transfer power (e.g., mechanical energy) from one or more electric motors  52  and/or the prime mover  41  to the tractive elements  82 . The tractive elements  82  and electric motors  52  (or prime mover  41 ) can facilitate a driving and/or steering function of the lift device  10 . 
     With additional reference to  FIG. 4 , the platform assembly  16  is shown in further detail. The platform assembly  16  is configured to provide a work area for an operator of the lift device  10  to stand/rest upon. The platform assembly  16  can be pivotally coupled to an upper end of the lift assembly  14 . The lift device  10  is configured to facilitate the operator accessing various elevated areas (e.g., lights, platforms, the sides of buildings, building scaffolding, trees, power lines, etc.). The lift device  10  may use various electrically-powered motors and electrically-powered linear actuators or hydraulic cylinders to facilitate elevation and/or horizontal movement (e.g., lateral movement, longitudinal movement) of the platform assembly  16  (e.g., relative to the base assembly  12 , or to a ground surface that the base assembly  12  rests upon). 
     The platform assembly  16  includes a base member, a base portion, a platform, a standing surface, a shelf, a work platform, a floor, a deck, etc., shown as a deck  18 . The deck  18  provides a space (e.g., a floor surface) for a worker to stand upon as the platform assembly  16  is raised and lowered. 
     The platform assembly  16  includes a railing assembly including various members, beams, bars, guard rails, rails, railings, etc., shown as rails  22 . The rails  22  extend along substantially an entire perimeter of the deck  18 . The rails  22  provide one or more members for the operator of the lift device  10  to grasp while using the lift device  10  (e.g., to grasp while operating the lift device  10  to elevate the platform assembly  16 ). The rails  22  can include members that are substantially horizontal to the deck  18 . The rails  22  can also include vertical structural members that couple with the substantially horizontal members. The vertical structural members can extend upwards from the deck  18 . 
     The platform assembly  16  can include a human machine interface (HMI) (e.g., a user interface, an operator interface, etc.), shown as the user interface  20 . The user interface  20  is configured to receive user inputs from the operator at or upon the platform assembly  16  to facilitate operation of the lift device  10 . The user interface  20  can include any number of buttons, levers, switches, keys, etc., or any other user input device configured to receive a user input to operate the lift device  10 . The user interface  20  may also provide information to the user (e.g., through one or more displays, lights, speakers, haptic feedback devices, etc.). The user interface  20  can be supported by one or more of the rails  22 . 
     Referring to  FIG. 1 , the platform assembly  16  includes a frame  24  (e.g., structural members, support beams, a body, a structure, etc.) that extends at least partially below the deck  18 . The frame  24  can be integrally formed with the deck  18 . The frame  24  is configured to provide structural support for the deck  18  of the platform assembly  16 . The frame  24  can include any number of structural members (e.g., beams, bars, I-beams, etc.) to support the deck  18 . The frame  24  couples the platform assembly  16  with the lift assembly  14 . The frame  24  may be rotatably or pivotally coupled with the lift assembly  14  to facilitate rotation of the platform assembly  16  about an axis  28  (e.g., a vertical axis). The frame  24  can also rotatably/pivotally couple with the lift assembly  14  such that the frame  24  and the platform assembly  16  can pivot about an axis  25  (e.g., a horizontal axis). 
     The lift assembly  14  includes one or more beams, articulated arms, bars, booms, arms, support members, boom sections, cantilever beams, etc., shown as lift arms  32   a,    32   b,  and  32   c.  The lift arms are hingedly or rotatably coupled with each other at their ends. The lift arms can be hingedly or rotatably coupled to facilitate articulation of the lift assembly  14  and raising/lowering and/or horizontal movement of the platform assembly  16 . The lift device  10  includes a lower lift arm  32   a,  a central or medial lift arm  32   b,  and an upper lift arm  32   c.  The lower lift arm  32   a  is configured to hingedly or rotatably couple at one end with the base assembly  12  to facilitate lifting (e.g., elevation) of the platform assembly  16 . The lower lift arm  32   a  is configured to hingedly or rotatably couple at an opposite end with the medial lift arm  32   b.  Likewise, the medial lift arm  32   b  is configured to hingedly or rotatably couple with the upper lift arm  32   c.  The upper lift arm  32   c  can be configured to hingedly interface/couple and/or telescope with an intermediate lift arm  32   d.  The upper lift arm  32   c  can be referred to as “the jib” of the lift device  10 . The intermediate lift arm  32   d  may extend into an inner volume of the upper lift arm  32   c  and extend and/or retract. The lower lift arm  32   a  and the medial lift arm  32   b  may be referred to as “the boom” of the overall lift device  10  assembly. The intermediate lift arm  32   d  can be configured to couple (e.g., rotatably, hingedly, etc.), with the platform assembly  16  to facilitate levelling of the platform assembly  16 . 
     The lift arms  32  are driven to hinge or rotate relative to each other by actuators  34   a,    34   b,    34   c,  and  34   d  (e.g., electric linear actuators, linear electric arm actuators, hydraulic cylinders, etc.). The actuators  34   a,    34   b,    34   c,  and  34   d  can be mounted between adjacent lift arms to drive adjacent lift arms to hinge or pivot (e.g., rotate some angular amount) relative to each other about pivot points  84 . The actuators  34   a,    34   b,    34   c,  and  34   d  can be mounted between adjacent lift arms using any of a foot bracket, a flange bracket, a clevis bracket, a trunnion bracket, etc. The actuators  34   a,    34   b,    34   c,  and  34   d  may be configured to extend or retract (e.g., increase in overall length, or decrease in overall length) to facilitate pivoting adjacent lift arms to pivot/hinge relative to each other, thereby articulating the lift arms and raising or lowering the platform assembly  16 . 
     The actuators  34   a,    34   b,    34   c,  and  34   d  can be configured to extend (e.g., increase in length) to increase a value of an angle formed between adjacent lift arms  32 . The angle can be defined between centerlines of adjacent lift arms  32  (e.g., centerlines that extend substantially through a center of the lift arms  32 ). For example, the actuator  34   a  is configured to extend/retract to increase/decrease the angle  74   a  defined between a centerline of the lower lift arm  32   a  and the longitudinal axis  78  (angle  74   a  can also be defined between the centerline of the lower lift arm  32   a  and a plane defined by the longitudinal axis  78  and lateral axis  80 ) and facilitate lifting of the platform assembly  16  (e.g., moving the platform assembly  16  at least partially along the upward direction  46 ). Likewise, the actuator  34   b  can be configured to retract to decrease the angle  74   a  to facilitate lowering of the platform assembly  16  (e.g., moving the platform assembly  16  at least partially along the downward direction  48 ). Similarly, the actuator  34   b  is configured to extend to increase the angle  74   b  defined between centerlines of the lower lift arm  32   a  and the medial lift arm  32   b  and facilitate elevating of the platform assembly  16 . Similarly, the actuator  34   b  is configured to retract to decrease the angle  74   b  to facilitate lowering of the platform assembly  16 . The electric actuator  34   c  is similarly configured to extend/retract to increase/decrease the angle  74   c,  respectively, to raise/lower the platform assembly  16 . 
     The actuators  34   a,    34   b,    34   c,  and  34   d  can be mounted (e.g., rotatably coupled, pivotally coupled, etc.) to adjacent lift arms at mounts  40  (e.g., mounting members, mounting portions, attachment members, attachment portions, etc.). The mounts  40  can be positioned at any position along a length of each lift arm. For example, the mounts  40  can be positioned at a midpoint of each lift arm, and a lower end of each lift arm. 
     The intermediate lift arm  32   d  and the frame  24  are configured to pivotally interface/couple at a platform rotator  30  (e.g., a rotary actuator, a rotational electric actuator, a gear box, etc.). The platform rotator  30  facilitates rotation of the platform assembly  16  about the axis  28  relative to the intermediate lift arm  32   d.  In some embodiments, the platform rotator  30  is positioned between the frame  24  and the upper lift arm  32   c  and facilitates pivoting of the platform assembly  16  relative to the upper lift arm  32   c.  The axis  28  extends through a central pivot point of the platform rotator  30 . The intermediate lift arm  32   d  can also be configured to articulate or bend such that a distal portion of the intermediate lift arm  32   d  pivots/rotates about the axis  25 . The intermediate lift arm  32   d  can be driven to rotate/pivot about axis  25  by extension and retraction of the actuator  34   d.    
     The intermediate lift arm  32   d  is also configured to extend/retract (e.g., telescope) along the upper lift arm  32   c.  In some embodiments, the lift assembly  14  includes a linear actuator (e.g., a hydraulic cylinder, an electric linear actuator, etc.), shown as extension actuator  35 , that controls extension and retraction of the intermediate lift arm  32   d  relative to the upper lift arm  32   c.  In other embodiments, one more of the other arms of the lift assembly  14  include multiple telescoping sections that are configured to extend/retract relative to one another. 
     The platform assembly  16  is configured to be driven to pivot about the axis  28  (e.g., rotate about axis  28  in either a clockwise or a counter-clockwise direction) by an electric or hydraulic motor  26  (e.g., a rotary electric actuator, a stepper motor, a platform rotator, a platform electric motor, an electric platform rotator motor, etc.). The motor  26  can be configured to drive the frame  24  to pivot about the axis  28  relative to the upper lift arm  32   c  (or relative to the intermediate lift arm  32   d ). The motor  26  can be configured to drive a gear train to pivot the platform assembly  16  about the axis  28 . 
     Referring to  FIGS. 1 and 2 , the lift assembly  14  is configured to pivotally or rotatably couple with the base assembly  12 . The base assembly  12  includes a rotatable base member, a rotatable platform member, a fully electric turntable, etc., shown as a turntable  70 . The lift assembly  14  is configured to rotatably/pivotally couple with the base assembly  12 . The turntable  70  is rotatably coupled with a base, frame, structural support member, carriage, etc., of base assembly  12 , shown as base  36 . The turntable  70  is configured to rotate or pivot relative to the base  36 . The turntable  70  can pivot/rotate about the central axis  42  relative to base  36 , about a slew bearing  71  (e.g., the slew bearing  71  pivotally couples the turntable  70  to the base  36 ). The turntable  70  facilitates accessing various elevated and angularly offset locations at the platform assembly  16 . The turntable  70  is configured to be driven to rotate or pivot relative to base  36  and about the slew bearing  71  by an electric motor, an electric turntable motor, an electric rotary actuator, a hydraulic motor, etc., shown as the turntable motor  44 . The turntable motor  44  can be configured to drive a geared outer surface  73  of the slew bearing  71  that is rotatably coupled to the base  36  about the slew bearing  71  to rotate the turntable  70  relative to the base  36 . The lower lift arm  32   a  is pivotally coupled with the turntable  70  (or with a turntable member  72  of the turntable  70 ) such that the lift assembly  14  and the platform assembly  16  rotate as the turntable  70  rotates about the central axis  42 . In some embodiments, the turntable  70  is configured to rotate a complete 360 degrees about the central axis  42  relative to the base  36 . In other embodiments, the turntable  70  is configured to rotate an angular amount less than 360 degrees about the central axis  42  relative to the base  36  (e.g., 270 degrees, 120 degrees, etc.). 
     The base assembly  12  includes one or more energy storage devices or power sources (e.g., capacitors, batteries, Lithium-Ion batteries, Nickel Cadmium batteries, fuel tanks, etc.), shown as batteries  64 . The batteries  64  are configured to store energy in a form (e.g., in the form of chemical energy) that can be converted into electrical energy for the various electric motors and actuators of the lift device  10 . The batteries  64  can be stored within the base  36 . The lift device  10  includes a controller  38  that is configured to operate any of the motors, actuators, etc., of the lift device  10 . The controller  38  can be configured to receive sensory input information from various sensors of the lift device  10 , user inputs from the user interface  20  (or any other user input device such as a key-start or a push-button start), etc. The controller  38  can be configured to generate control signals for the various motors, actuators, etc., of the lift device  10  to operate any of the motors, actuators, electrically powered movers, etc., of the lift device  10 . The batteries  64  are configured to power any of the motors, sensors, actuators, electric linear actuators, electrical devices, electrical movers, stepper motors, etc., of the lift device  10 . The base assembly  12  can include a power circuit including any necessary transformers, resistors, transistors, thermistors, capacitors, etc., to provide appropriate power (e.g., electrical energy with appropriate current and/or appropriate voltage) to any of the motors, electric actuators, sensors, electrical devices, etc., of the lift device  10 . 
     The batteries  64  are configured to deliver power to the motors  52  to drive the tractive elements  82 . A rear set of tractive elements  82  can be configured to pivot to steer the lift device  10 . In other embodiments, a front set of tractive elements  82  are configured to pivot to steer the lift device  10 . In still other embodiments, both the front and the rear set of tractive elements  82  are configured to pivot (e.g., independently) to steer the lift device  10 . In some examples, the base assembly  12  includes a steering system  150 . The steering system  150  is configured to drive tractive elements  82  to pivot for a turn of the lift device  10 . The steering system  150  can be configured to pivot the tractive elements  82  in pairs (e.g., to pivot a front pair of tractive elements  82 ), or can be configured to pivot tractive elements  82  independently (e.g., four-wheel steering for tight-turns). 
     In some embodiments, the base assembly  12  also includes a user interface  21  (e.g., a HMI, a user interface, a user input device, a display screen, etc.). In some embodiments, the user interface  21  is coupled to the base  36 . In other embodiments, the user interface  21  is positioned on the turntable  70 . The user interface  21  can be positioned on any side or surface of the base assembly  12  (e.g., on the front  62  of the base  36 , on the rear  60  of the base  36 , etc.) 
     Referring now to  FIGS. 2 and 3 , the base assembly  12  includes a longitudinally extending frame member  54  (e.g., a rigid member, a structural support member, an axle, a base, a frame, a carriage, a chassis, etc.). The longitudinally extending frame member  54  provides structural support for the turntable  70  as well as the tractive elements  82 . The longitudinally extending frame member  54  is pivotally coupled with lateral frame members  110  (e.g., axles, frame members, beams, bars, etc.) at opposite longitudinal ends of the longitudinally extending frame member  54 . For example, the lateral frame members  110  may be pivotally coupled with the longitudinally extending frame member  54  at a front end and a rear end of the longitudinally extending frame member  54 . The lateral frame members  110  can each be configured to pivot about a pivot joint  58  (e.g., about a longitudinal axis). The pivot joint  58  can include a pin and a receiving portion (e.g., a bore, an aperture, etc.). The pin of the pivot joint  58  is coupled to one of the lateral frame members  110  (e.g., a front lateral frame member  110  or a rear lateral frame member  110 ) or the longitudinally extending frame member  54  and the receiving portion is coupled to the other of the longitudinally extending frame member  54  and the lateral frame member  110 . For example, the pin may be coupled with longitudinally extending frame member  54  and the receiving portion can be coupled with one of the lateral frame members  110  (e.g., integrally formed with the front lateral frame member  110 ). 
     In some embodiments, the longitudinally extending frame member  54  and the lateral frame members  110  are integrally formed or coupled (e.g., fastened, welded, riveted, etc.) to define the base  36 . In still other embodiments, the base  36  is integrally formed with the longitudinally extending frame member  54  and/or the lateral frame members  110 . In still other embodiments, the base  36  is coupled with the longitudinally extending frame member  54  and/or the lateral frame members  110 . 
     The base assembly  12  includes one or more axle actuators  56  (e.g., electric linear actuators, electric axle actuators, electric levelling actuators, hydraulic cylinders, etc.). The axle actuators  56  can be linear actuators configured to receive power from the batteries  64 , for example. The axle actuators  56  can be configured to extend or retract to contact a top surface of a corresponding one of the lateral frame members  110 . When the axle actuators  56  extend, an end of a rod of the levelling actuators can contact the surface of lateral frame member  110  and prevent relative rotation between lateral frame member  110  and longitudinally extending frame member  54 . In this way, the relative rotation/pivoting between the lateral frame member  110  and the longitudinally extending frame member  54  can be locked (e.g., to prevent rolling of the longitudinally extending frame member  54  relative to the lateral frame members  110  during operation of the lift assembly  14 ). The axle actuators  56  can receive power from the batteries  64 , which can allow the axle actuators  56  to extend or retract. The axle actuators  56  receive control signals from controller  38 . 
     Control System 
     Referring to  FIG. 5 , the lift device  10  includes a control system  200 . The control system  200  includes the controller  38 . The controller  38  includes a processor  202  and a memory device, shown as memory  204 . The memory  204  may contain one or more programs or instructions for execution by the processor  202 . 
     As shown in  FIG. 5 , the controller  38  is operatively coupled to (e.g., in communication with) the motor  26 , the platform rotator  30 , the turntable motor  44 , the actuators (e.g., the actuator  34   a,  the actuator  34   b,  etc.), the extension actuator  35 , and the motors  52 . The controller  38  is operatively coupled to the user interface  20  and the user interface  21 . The controller  38  is operatively coupled to an indicator, shown as alarm  210 . The alarm  210  may provide an indication, alert, or warning to a user when activated. The indication from the alarm  210  may be visual, auditory, or another type of indication (e.g., vibrational haptic feedback). By way of example, the alarm  210  may provide an auditory indication (e.g., a siren) or a visual indication (e.g., a flashing light) to a user. The controller  38  is operatively coupled to a sensor assembly (e.g., a barrier sensor, an operator position sensor, a user position sensor, a user contact sensor, an operator contact sensor, etc.), shown as user contact sensor  300 . As described herein, the user contact sensor  300  is configured to provide an indication (e.g., a signal) to the controller  38  in response to contact with a user. The user contact sensor  300  may be positioned such that a user positioned in front of the user contact sensor  300  engages the user contact sensor  300  when a portion of a user&#39;s upper body (e.g., a torso, a stomach, a shoulder, etc.) moves toward and/or above the user interface  20 . Although  FIG. 5  only illustrates operative coupling between the controller  38  and certain components of the lift device  10 , it should be understood that other components may be in communication with the controller  38  as well. By way of example, the batteries  64  may be operatively coupled to the controller  38 . 
     The controller  38  may be configured to receive information (e.g., user instructions, sensor signals, etc.) from one or more components of the lift device  10 . By way of example, the controller  38  may receive user inputs or commands from the user interface  20  and/or the user interface  21 . By way of another example, the controller  38  may receive an input from the user contact sensor  300  (e.g., a signal indicating that a user has applied a force on the user contact sensor  300 ). 
     The controller  38  may be configured to provide information (e.g., commands, indication, etc.) to one or more components of the lift device  10 . By way of example, the controller  38  may send commands (e.g., signals) that control the outputs (e.g., movement) of the motor  26 , the actuators  34 , the extension actuator  35 , the motors  52 , and/or any other actuators of the lift device  10 . By way of another example, the controller  38  may provide a command to the alarm  210  that causes the alarm  210  to activate. By way of another example, the controller  38  may provide commands that cause the user interface  20  and/or the user interface  21  to provide (e.g., display) information to a user. 
     User Contact Sensor 
     Referring to  FIGS. 4 and 6-9 , the user contact sensor  300  is coupled to the rails  22 . Specifically, the rails  22  include a pair of frame members, shown as vertical rails  302 , that extend vertically upward from the deck  18 . The vertical rails  302  are positioned on opposite sides of the user interface  20  such that the user interface  22  extends laterally between the vertical rails  302 . A rail, shown as cage  310 , is fixedly coupled to the vertical rails  302  and extends around the user interface  20 . Specifically, the cage  310  extends laterally between the vertical rails  302 , longitudinally forward of the vertical rails  302 , and longitudinally rearward of the vertical rails  302 . The cage  310  includes a pair of inclined portions  312 , each extending longitudinally forward and vertically upward from a middle portion of one of the vertical rails  302 . The cage  310  further includes a pair of curved portions  314 , each coupled to an upper end of one of the inclined portions  312 . The curved portions  314  each extend upward and longitudinally rearward from the corresponding inclined portion  312 . A u-shaped horizontal portion  316  is coupled to both of the curved portions  314 . The horizontal portion  316  extends longitudinally rearward from the curved portions  314  and laterally between the curved portions  314 . The horizontal portion  316  is coupled to the top end of each vertical rail  302 . The curved portions  314  and the horizontal portion  316  both extend above the user interface  20 . 
     The user contact sensor  300  is an assembly including a first end portion or hinge, shown as pivot portion  320 , a second end portion, shown as sensing portion  322 , and central portion or rod, shown as bar assembly  324 . The pivot portion  320  is directly coupled to the curved portion  314  of the cage  310  on the left side of the user interface  20 . The sensing portion  322  is directly coupled to the curved portion  314  of the cage  310  on the right side of the user interface  20 . The bar assembly  324  is coupled to the pivot portion  320  and extends laterally from the pivot portion  320  to the sensing portion  322 . Accordingly, the user contact sensor  300  is positioned above and longitudinally forward of the user interface  20 . In other embodiments, the user contact sensor  300  is mirrored such that the sensing portion  322  is positioned to the left of the user interface  20  and the pivot portion  320  is positioned to the right of the user interface. 
     Referring to  FIGS. 8, 10, 11, and 14 , the pivot portion  320  is shown according to an exemplary embodiment. The pivot portion  320  includes a first bracket, first hinge portion, or pivoting portion, shown as pivoting clevis  330 , and a second bracket, second hinge portion, or fixed portion, shown as fixed clevis  332 . The fixed clevis  332  is fixedly coupled to the curved portion  314  to the left of the user interface  20 . The pivoting clevis  330  is pivotally coupled to the fixed clevis  332  such that the pivoting clevis  330  pivots about an axis  334 . Specifically, a pair of fasteners, shown as bolts  336 , extend through corresponding pivot apertures defined by the pivoting clevis  330  and the fixed clevis  332  to pivotally couple the pivoting clevis  330  to the fixed clevis  332 . In some embodiments, the axis  334  is skewed in a longitudinal direction relative to a vertical axis such that the bar assembly  334  moves downward when moved in a longitudinally rearward direction. In other embodiments, the axis  334  is substantially vertical. The pivoting clevis  330  further defines an aperture or passage (e.g., a rod aperture), shown as bar aperture  338 , that extends perpendicular to the axis  334 . The bar aperture  338  receives the bar assembly  324  therethrough. 
     Referring to  FIGS. 9, 10, 12, and 13 , the sensing portion  322  is shown according to an exemplary embodiment. The sensing portion  322  includes a housing  340 . The housing  340  includes a first member or face plate portion, shown as outer plate  342 , and defines a surface of the housing  340  that faces the pivot portion  320 . The outer plate  342  defines a laterally-extending aperture or passage, shown as end aperture  344 . The end aperture  344  is sized to receive an end of the bar assembly  324 . The outer plate  342  is directly coupled to a second member or portion of the housing  340 , shown as inner plate  346 . The inner plate  346  and the outer plate  342  may extend substantially parallel to one another. The inner plate  346  defines a laterally-extending aperture or passage, shown as sensor aperture  348 . The sensor aperture  348  may be substantially aligned with the end aperture  344 . The housing  348  further includes a third member, shown as back shell  350 . The back shell  350  is coupled to the inner plate  346  and the outer plate  342 . An inner volume of the housing  350  is defined between the inner plate  346  and the back shell  350 . 
     The inner volume of the housing  350  receives a sensor  360  extending into the sensor aperture  348 . The sensor  360  may be substantially aligned with the end aperture  344  and the sensor aperture  348 . The sensor  360  is received within a laterally-extending passage or aperture defined by a boss, shown as sensor block  362 . The sensor block  362  is coupled to the inner plate  346 . In some embodiments, the lateral position of the sensor  360  relative to the sensor block  362  is adjustable (e.g., the sensor  360  is selectively slidably coupled to the block  360  of the housing  360 ). As shown in  FIG. 13 , the sensing portion  322  includes a pair of fasteners, shown as sensor bolts  364 , that are in threaded engagement with the sensor block  362 . The sensor bolts  364  may be loosened to permit free lateral movement of the sensor  360 . When tightened, the sensor bolts  364  engage the sensor  360 , limiting (e.g., preventing) lateral movement of the sensor  360 . 
     Referring to  FIGS. 8-11 and 13-17 , the bar assembly  324  is shown according to an exemplary embodiment. The bar assembly  324  includes a first portion, central portion, or resilient member, shown as bar  370 . The bar  370  is relatively long and thin and makes up the majority of the length of the bar assembly  324 . In some embodiments, the bar  370  is made from a resilient material that is flexible but returns to an original shape after an applied force on the bar  370  is released. In one embodiment, the bar  370  may be made from fiberglass. In other embodiments, the bar  370  is made from another resilient material, such as plastic. 
     Coupled to a first end of the bar  370  is a first end portion of the bar assembly  324 , shown as threaded end  372 . The threaded end  372  is fixedly coupled to the bar  370 . By way of example, the threaded end  372  may define a recess that receives an end of the bar  370 , and the bar  370  may be fixed in place using an adhesive (e.g., epoxy). The threaded end  372  includes exterior threads, shown as threaded portion  374 . The threaded portion  374  extends through the bar aperture  338  defined by the pivot portion  320 . A pair of fasteners, shown as nuts  376 , each engage the threaded portion  374 . Specifically, each nut  376  is positioned on and tightened against an opposing side of the pivoting clevis  330 , holding the threaded end  372  in place relative to the pivoting clevis  330 . The lateral position of the threaded end  372  relative to the pivoting clevis  330  may be adjusted (e.g., to adjust the position of the opposing end relative to the sensing portion  322 ) by loosening the nuts  376 , moving the nuts  376  to a different position along the threaded portion  374 , and retightening the nuts  376 . In other embodiments, the bar aperture  338  is in threaded engagement with the threaded portion  374 . In such embodiments, one or both of the nuts  376  may be omitted. 
     Coupled to a second end of the bar  370  opposite the first end is a second end portion of the bar assembly  324 , shown as sensor end  380 . The sensor end  380  is fixedly coupled to the bar  370 . By way of example, the sensor end  380  may define a recess that receives an end of the bar  370 , and the bar  370  may be fixed in place using an adhesive. The sensor end  380  is sized to be received within the end aperture  344 . The exterior surface of the sensor end  380  may be substantially cylindrical. In other embodiments, the sensor end  380  formed as part of the bar  370  (i.e., the bar  370  and the sensor end  380  are not separate pieces). 
     The sensor  360  is operatively coupled to the controller  38  and configured to provide a signal indicating at least one of (a) whether or not the sensor end  380  is present within the end aperture  344  or (b) that the sensor end  380  has entered or exited the end aperture  344 . By way of example, the sensor  360  may indicate that the sensor end  380  has exited the end aperture  344  when the sensor  360  detects the presence of the sensor end  380  at a first time and subsequently does not detect the presence of the sensor end  380 . The sensor  360  may be or include any type of sensor that is capable of providing this information. 
     In some embodiments, the sensor  360  is a proximity sensor that is configured to detect a proximity of an object within the end aperture  344 . In such an embodiment, the sensor  360  may determine that the sensor end  380  is present when the sensor  360  detects an object within a threshold distance of the sensor  360 . In such embodiments, the nuts  376  and/or the fasteners  364  may be adjusted to adjust the lateral positions of the sensor  360  and/or the bar assembly  324 , thereby varying the distance between the sensor end  380  and the sensor  360 . This adjustment may be performed such that the sensor end  380  is positioned within the threshold distance of the sensor  360  when the sensor end  380  is received within the end aperture  344 . In some embodiments that utilize a proximity sensor, the sensor  360  is spaced or separated from the sensor end  380  such that the sensor end  380  does not engage the sensor  360 . 
     In some embodiments, the sensor  360  is a proximity sensor that is configured to sense the presence of metals (e.g., an inductive proximity sensor). Such a proximity sensor may be configured to differentiate or distinguish between a metal or metallic material (e.g., steel, brass, aluminum, copper, etc.) and a non-metal or non-metallic material (e.g., plastic, fiberglass, wood, etc.). By way of example, the sensor  360  may provide a first signal in response to the presence of a metal within the threshold distance and provide a second, different signal in response to the presence of a non-metal within the threshold distance. In embodiments that utilize a proximity sensor that is configured to sense metals, the sensor end  380  may be made of a metal, and the portions of the housing  350  that are in close proximity to the sensor  360  (e.g., the outer plate  340  and the inner plate  346 ) may be made of a non-metal. Such a configuration may facilitate avoiding falsely detecting the presence of the sensor end  380 . 
     In other embodiments, the sensor  360  utilizes a different type of sensor. In some embodiments, the sensor  360  utilizes a different type of proximity sensor. By way of example, the sensor  360  may include an infrared proximity sensor, an ultrasonic proximity sensor, a capacitive proximity sensor, a laser rangefinder, or another type of proximity sensor. In some embodiments, a permanent magnet is coupled to the sensor end  380 , and a sensor  360  (e.g., a hall effect sensor) detects the magnetic field produced by the permanent magnet. In some embodiments, the sensor  360  includes a break beam sensor that detects when a beam of light is interrupted by the sensor end  380 . Such a sensor may be positioned such that the sensor end  380  interrupts the beam when the sensor end  380  is received within the end aperture  344 . In some embodiments, the sensor  360  includes two more contacts that engage the sensor end  380 , passing current through the sensor  380 . Such as sensor may be positioned such that the sensor end  380  engages the contacts to form a closed circuit within the sensor end  380  is received within the end aperture  344 , and the controller  348  whether or not the sensor end  380  is present based on a measured current passing through the contacts. 
     Operation of the user contact sensor  300  is shown from a first perspective in  FIGS. 18-21  and from a second perspective in  FIGS. 22-24 . In operation, the user contact sensor  300  is configured such that the sensor end  380  is normally positioned within the end aperture  344 . This configuration is shown in  FIGS. 18 and 22 . The rails  22  hold the pivot portion  320  and the sensing portion  322  at a fixed distance relative to one another, and the bar is sized such that the sensor end  380  engages the outer plate  342  to prevent the sensor end  380  from leaving the end aperture  344  due to minor forces (e.g., due to vibration of the lift device  10 , due to a user brushing against the bar  370 , etc.). While the sensor end  380  remains within the end aperture  344 , the sensor  360  provides a first signal to the controller  38 , and the controller  38  permits standard control of the lift device  10 . 
     As the user operates the lift device  10 , they generally stand in front of the user interface  20  and face toward the user interface  20 , as shown in  FIGS. 18 and 22 . In some situations, the lift assembly  14 , the turntable  70 , and/or the motors  52  move the platform  16  in proximity to an obstacle (e.g., a tree, a portion of a structure such as a support beam, etc.). In some such situations, the user is positioned between the user interface  20  and the obstacle. As the lift assembly  14  moves the platform  16 , the distance between the user interface  20  and the obstacle may decrease, limiting the freedom of movement of the operator. In some such cases, it may be difficult for the user to access the controls of the user interface  20  to move the platform  16  away from the obstacle. 
     If the obstacle pushes the user toward the user interface  20 , the user comes into contact with the bar  370  of the user contact sensor  300 . In some embodiments, the height of the bar  370  is selected such that the upper body (e.g., the stomach, the chest, the arms, the shoulders, etc.) of the user comes into contact with the bar  370 . As shown in  FIGS. 19 and 23 , the user presses against the bar  370 , applying a longitudinally-rearward force near the center of the bar  370 , and the resilient material of the bar  370  begins to bow. If the user were to release the force on the bar  370 , the resilient material of the bar  370  would return to the original, straight shape, and the sensor end  380  would remain in the end aperture  344  (e.g., the bar  370  elastically deforms in response to the force on the bar  370 ). Accordingly, the resilient nature of the bar  370  causes the bar  370  to apply a biasing force that resists (a) bending of the bar  370  and (b) removal of the sensor end  380  from the end aperture  344 . If the user&#39;s force on the bar  370  is released before the bow  370  is bent to a threshold position, the biasing force of the bar  370  returns the bar  370  and the sensor end  380  to the original position. 
     As shown in  FIGS. 20 and 24 , if the user continues to apply a force on the bar  370  (e.g., because they are being pushed rearward by the object as the lift assembly  14  extends), the bending of the bar  370  becomes significant enough (e.g., exceeds a threshold deflection, is bent beyond the threshold position, etc.) for the sensor end  380  to exit the end aperture  344 . After the sensor end  380  exits the end aperture  344 , the pivot portion  320  permits the bar  370  to rotate freely away from the user, longitudinally rearward and/or downward. 
     In response to the sensor end  380  exiting the end aperture  344 , the sensor  360  provides a second signal to the controller  38 . The second signal indicates that the sensor end  380  has exited the end aperture  344 . In response to receiving the second signal, the controller  38  may be configured to perform one or more actions to stop or reverse one or more recent movements of the lift device  10 . The controller  38  may additionally or alternatively activate the alarm  210  in response to receiving the second signal. By way of example, the controller  38  may stop movement of all of the actuators of the lift device  10  (e.g., the actuators  34 , the motors  32 , etc.). By taking this action, the controller  38  may ensure that the platform  16  does not move further relative to the obstacle. 
     In some embodiments, in response to receiving the second signal, the controller  38  is configured to reverse the movements of one or more systems of the lift device  10  that occurred immediately before the second signal was received. One such example of this is illustrated in  FIGS. 18-21 . In  FIGS. 18 and 19 , the platform  16  rises. After the user contact sensor  300  is activated in  FIG. 20 , the platform  16  is lowered in  FIG. 21 . By way of another example, if the lift assembly  14  raised the platform  16  and the motors  52  moved the base assembly  12  in a forward direction immediately prior to the receipt of the second signal, the controller  38  may control the lift assembly  14  to lower the platform  16  and/or control the motors  52  to move the base assembly  12  in a reverse direction. In order to identify the correct reverse movements to perform, the controller  38  may retain a history of all of the movements of the lift device  10  (e.g., as measured by sensors or as instructed by the controller  38 ) and the time at which they occurred. The controller  38  may determine what reverse movements to perform based on the history. 
     As utilized herein, the terms “approximately,” “about,” “substantially,” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims. 
     It should be noted that the term “exemplary” and variations thereof, as used herein to describe various embodiments, are intended to indicate that such embodiments are possible examples, representations, or illustrations of possible embodiments (and such terms are not intended to connote that such embodiments are necessarily extraordinary or superlative examples). 
     The term “coupled” and variations thereof, as used herein, means the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members coupled directly to each other, with the two members coupled to each other using a separate intervening member and any additional intermediate members coupled with one another, or with the two members coupled to each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, or fluidic. 
     References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below”) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure. 
     The hardware and data processing components used to implement the various processes, operations, illustrative logics, logical blocks, modules and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or, any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, particular processes and methods may be performed by circuitry that is specific to a given function. The memory (e.g., memory, memory unit, storage device) may include one or more devices (e.g., RAM, ROM, Flash memory, hard disk storage) for storing data and/or computer code for completing or facilitating the various processes, layers and modules described in the present disclosure. The memory may be or include volatile memory or non-volatile memory, and may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present disclosure. According to an exemplary embodiment, the memory is communicably connected to the processor via a processing circuit and includes computer code for executing (e.g., by the processing circuit or the processor) the one or more processes described herein. 
     The present disclosure contemplates methods, systems and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions. 
     Although the figures and description may illustrate a specific order of method steps, the order of such steps may differ from what is depicted and described, unless specified differently above. Also, two or more steps may be performed concurrently or with partial concurrence, unless specified differently above. Such variation may depend, for example, on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations of the described methods could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps, and decision steps. 
     It is important to note that the construction and arrangement of the lift device  10  as shown in the various exemplary embodiments is illustrative only. Additionally, any element disclosed in one embodiment may be incorporated or utilized with any other embodiment disclosed herein. Although only one example of an element from one embodiment that can be incorporated or utilized in another embodiment has been described above, it should be appreciated that other elements of the various embodiments may be incorporated or utilized with any of the other embodiments disclosed herein.