Patent Description:
Various types of wheeled mobility devices may provide mobility to a user whose mobility may be limited due to a temporary or permanent physical condition. Temporary conditions may include injury, trauma, illness, unconsciousness, or other conditions. Permanent or long term conditions may include from paraplegia, quadriplegia, multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and similar conditions.

Various types of wheelchairs and wheeled mobility devices may enable person to be moved about while sitting or reclining. Where the user is conscious and is capable of exerting the arms and hands, the user may propel the wheels of the wheelchair or wheeled mobility devices without the assistance of another person. Various motorized wheelchairs and carts may enable a user to move the device by simply manipulating a control, with minimal exertion. Some such motorized wheelchairs and carts, as well as non-motorized wheelchairs, have been designed to shift the user from a seated to a standing position, and vice versa. Some have been designed to transport the user while either standing (only indoors) or seated, generally on level surfaces.

<CIT> discloses a wheelchair having a seat mounted to a base via a universal joint to provide for selective orientation of the seat. A pair of actuators are interposed between the seat and the base so that selective extension and retraction of the actuators orients the seat as desired. A level sensing device provides output signals to control the extension and retraction of the actuators, and thus the final orientation of the seat. This allows a wheelchair occupant to remain level while the chair traverses uneven ground or to selectively reposition the seat to relieve pressure points without the assistance of an attendant.

<CIT> discloses a wheelchair including a base assembly, a seat assembly having a seat and a backrest and an actuator assembly having a plurality of actuators supporting the seat on the base assembly. Each actuator can expand and retract individually. The actuator assembly allows for at least four degrees of movement of the seat assembly with respect to the base assembly. The wheelchair further includes a computer that is connected to the actuators and that controls the movement of the actuators. The computer moves the actuators to vary the position of the seat assembly with respect to the base assembly.

The object of the present invention is to provide an alternative wheeled mobility device having a simple and convenient self-leveling function and a corresponding method of controlling a tilt of a user support of a mobility device.

This technical problem is solved by a wheeled mobility device comprising the features of claim <NUM> and further by a method of claim <NUM>.

In order for the present invention, to be better understood and for its practical applications to be appreciated, the following Figures are provided and referenced hereafter. It should be noted that the Figures are given as examples only and in no way limit the scope of the invention. Like components are denoted by like reference numerals.

However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, modules, units and/or circuits have not been described in detail so as not to obscure the invention.

Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, "processing," "computing," "calculating," "determining," "establishing", "analyzing", "checking", or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and/or transforms data represented as physical (e.g., electronic) quantities within the computer's registers and/or memories into other data similarly represented as physical quantities within the computer's registers and/or memories or other information non-transitory storage medium (e.g., a memory) that may store instructions to perform operations and/or processes. Although embodiments of the invention are not limited in this regard, the terms "plurality" and "a plurality" as used herein may include, for example, "multiple" or "two or more". The terms "plurality" or "a plurality" may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently. Unless otherwise indicated, the conjunction "or" as used herein is to be understood as inclusive (any or all of the stated options).

Some embodiments of the invention may include an article such as a computer or processor readable medium, or a computer or processor non-transitory storage medium, such as for example a memory, a disk drive, or a USB flash memory, encoding, including or storing instructions, e.g., computer-executable instructions, which when executed by a processor or controller, carry out methods disclosed herein.

In accordance with an embodiment of the present invention, a wheeled mobility device includes a self-leveling mechanism that includes a tiltable leveling structure. The self-leveling mechanism may be operated to maintain the user of the wheeled mobility device at a substantially constant orientation relative to an external axis or plane, e.g., to the vertical or to the horizontal. As used herein, leveling or self-leveling refers to maintaining an orientation relative to a specified plane, whether or not the specified plane is horizontal.

A user support for supporting a user of the wheeled mobility device may be attached to the tiltable leveling structure. The orientation of the user support may be fixed with respect to the orientation of the tiltable leveling structure. For example, the user support may include a seat or bed, a harness structure that is configured to support the user in a standing position, or user support structure that is configured to support the user in a range of positions. For example, the user support may include a seat with restraints with a conversion mechanism that is operable to raise the user from a sitting position to a standing position, and vice versa. One or more extendible columns or rods may straighten or bend various hinges to convert a seat to a standing harness.

The tiltable leveling structure is connected to, or otherwise supported by, a chassis of the wheeled mobility device (e.g., via actuators and a rod end bearing, the rod end bearing also known as a heim joint or rose joint). The chassis may include or support a motorized propulsion mechanism for propelling the wheeled mobility device along a surface. For example, the chassis may include wheels or tracks that may be rotated or moved by the motorized propulsion mechanism. For example, the motorized propulsion mechanism may include an electric motor (e.g., powered by a storage battery or otherwise), an internal combustion engine, or another suitable motor.

A part of the tiltable leveling structure may be connected to the chassis via a swivel connection, e.g., at or near an edge or end of the tiltable leveling structure, e.g., along an arm of the tiltable stabilizing structure. For example, the swivel connection may be located near an end of an arm that extends forward approximately along a longitudinal midline (e.g., that is approximately midway between right and left sides of the tiltable leveling structure) of the tiltable leveling structure. The swivel connection to the chassis enables at least limited rotation about at least two orthogonal axes (e.g., defining pitch and roll of the tiltable stabilizing structure). For example, the joint may include a ball joint, a rod end bearing, or another passive joint that enables rotation about at least two axes.

As used herein, forward and backward longitudinal directions of the wheeled mobility device or its components are defined with reference to the orientation of a user that is being carried by the wheeled mobility device in a manner for which the wheeled mobility device is designed. In particular, the user is being supported by the user support such that the user's back is supported by, or is adjacent to, a back support panel of the user support. Right and left lateral directions, as well as pitch and roll of the tiltable leveling structure of the user support, are similarly defined.

For example, the swivel connection may be located on an arm of the tiltable leveling structure. For example, the arm may extend forward from the remainder of the tiltable leveling structure. The arm may include structure (e.g., bar or rod) that may pass through the opening of a rod end bearing whose shaft is fixed to chassis to form the swivel connection. For example, the shaft of the rod end bearing may rise approximately vertically from a floor (or other part) of the chassis such that the swivel connection is located at a nonzero fixed distance above the floor of the chassis. Alternatively, the arm, or other structure of the tiltable leveling structure, may otherwise connect to the chassis to form the swivel connection.

Two actuator assemblies are each configured to substantially linearly vertically displace one of two displaceable connections of the tiltable leveling structure. The two displaceable connections are laterally displaced (by the actuator) from one another and from the swivel connection. In some cases, the two displaceable connections may be vertically displaced relative to one another or relative to the swivel connection when the wheeled mobility device is resting on a level horizontal surface and the tiltable leveling structure is also oriented parallel to the surface. For example, each linear actuator may be operable to substantially linearly displace the displaceable connection of the tiltable leveling structure in the vertical direction. Thus, operation of each actuator may adjust a distance between its corresponding displaceable connection and a floor of the chassis. For example, the actuator may include a screw mechanism, a scissors mechanism, or eccentric disk mechanism, a hydraulic or pneumatic piston, or another suitable mechanism for effecting a substantially vertical displacement. The operation of the two linear actuators may cause the tiltable leveling structure to rotate relative to the swivel connection around one or more axes. Typically, operation of the two actuators may change a pitch angle, roll angle, or both or another angle, of the tiltable leveling structure.

The positions of the swivel connection and the displaceable connections may be selected to provide a predetermined degree of control or mechanical advantage. For example, mutual separation distances among the swivel connection and the displaceable connections may be selected to be as large as possible (e.g., within constraints that may be imposed by structure of the chassis, of the tiltable leveling structure, or of structure that is attached to the chassis or the tiltable leveling structure). For example, if the swivel connection is located on a forward extending arm near a lateral midline of the tiltable stabilizing structure, then the displaceable connections may be located near opposite corners at the rear edge of the tiltable leveling structure. The mutual lateral separations among the swivel connection and the displaceable connections may be selected such that the separation distance is large enough so as not to require excessive thrust by the actuator, while being small enough so as to enable sufficiently rapid tilting of the self-leveling structure.

One or more sensors may be configured to sense a tilt of the tiltable leveling structure with respect to the horizontal or another predetermined plane. The sensors may be fixed to structure that is fixed to the tiltable leveling structure so as to tilt together with the tiltable leveling structure.

For example, the sensors may be configured to measure roll and pitch angles of the tiltable leveling structure relative to a target plane. The sensors may include one or more inertial measurement units, tilt sensors, or other sensors that may be configured to measure a tilt of the tiltable leveling structure with respect to a predetermined plane. For example, an inertial measurement unit may include one or more gyroscopes, accelerometers, fused gyro-accelerometers, inclinometers or tilt sensors, or other sensors capable of measuring or sensing an orientation, a change in orientation, a rate of change in orientation, or other quantities that may be interpreted to yield a current roll or pitch angle or other indicators of a tilt.

One or more surface tilt sensors may be mounted on the chassis to measure the tilt of a surface upon which the device is moving or standing. The measured surface tilt may be utilized to limit the dynamic range of the self-leveling mechanism. , For example, when the wheeled mobility device is balanced and stable, the balance sensors output the target pitch and roll angles; by comparing to the measured surface-slope angles, the amount of tilt correction, done by the balancing mechanism, can be computed and hence alerting when the dynamic angles-correction range exceeds its permitted limits. Second, warn the system (and user) for hazardous slopes.

A controller of the wheeled mobility device may be configured to operate the actuators to maintain the tilt of the tiltable leveling structure substantially parallel to a predetermined target plane. For example, the target plane may be horizontal (characterized by zero pitch and roll angles). In some cases, another target plane may be selected. For example, a particular user of the wheeled mobility device may feel more comfortable when, or otherwise prefer, leaning slightly backward, forward, or sideways when being carried by the wheeled mobility device.

The controller may apply an iterative algorithm to operate the actuators in accordance with measured tilts. For example, in each iteration of the algorithm, a current tilt (e.g., roll and pitch) of the tiltable leveling structure may be measured. A deviation of the measured tilt from the orientation of the target plane may be calculated.

A function of the deviation in each angle (e.g., roll and pitch) may be applied to yield a correction step that includes a displacement along a straight line that is to be applied to correct the measured deviation. The function may be configured such that step size is proportionally larger (e.g., as expressed as a ratio of step size to angular deviation) for large deviations than it is for smaller deviations. For example, the function may include raising the deviation to a nonzero power. Parameters of the function may be determined by a technician and may depend on such factors as geometry of the tiltable stabilizing structure, properties of the actuators, or other factors.

The calculated displacement correction steps may be used to calculate a (e.g., vertical) displacement of each of the displaceable connections. A speed of operation of each of the actuators may be calculated such that the calculated displacement is achieved during the iteration. Each actuator may then be operated at the calculated speed of operation (e.g., controlled by controlling the voltage that is applied to the actuator, or by controlling the duty-cycle of pulse-width-modulation (PWM) that is applied to the actuator) in order to achieve the calculated displacement.

An iteration control method as described herein may be advantageous over other types of control methods (e.g., proportional-integral-derivative, or PID, control). For example, the control method described herein may result in less overshoot, and less sensitivity to motor backlash or other mechanical inaccuracies than other control methods. Thus, the control method described herein may enable sufficiently fast convergence of the tilt of the tiltable leveling structure to the target plane to ensure the comfort and safety of the user. Furthermore, an iterative control method as described herein is independent of dynamic parameters of the system, and thus does not require a priori knowledge of these dynamic parameters. For example, the iterative control method is independent of such dynamic parameters as mass of components, moments of inertia, and applied forces (within ranges derived from systems specifications).

<FIG> schematically illustrates a wheeled mobility device configured to support a user in a sitting position, in accordance with an embodiment of the present invention. <FIG> schematically illustrates the wheeled mobility device of <FIG>, configured to support a user in a standing position.

Wheeled mobility device <NUM> includes chassis <NUM>. Chassis <NUM> includes a chassis floor <NUM> and one or more wheels (or tracks or other structure) for enabling self-propelled travel by wheeled mobility device <NUM> over a surface (e.g., a floor, road, sidewalk, driveway, ramp, or other surface suitable for self-propelled travel). For example, chassis <NUM> may include one or more drive wheels <NUM>. Each drive wheel <NUM> may be connected to a wheel drive <NUM>. For example, wheel drive <NUM> may include a drive motor, a transmission, or both. A drive motor may include an electric motor, an internal combustion engine, or another suitable type of motor or engine. Chassis <NUM> may include one or more support wheels <NUM>. Support wheels <NUM> may include non-driven wheels that provide stable support for wheeled mobility device <NUM> (e.g., such that the total number of wheels, including drive wheels <NUM> and supports wheels <NUM>, is at least three, e.g., at least four with two drive wheels <NUM> and two support wheels <NUM>). For example, swivel wheels <NUM> may be connected to chassis <NUM> by bearings that enable support wheels <NUM> to swivel freely so as to provide support without impeding movement of wheeled mobility device <NUM>.

In wheeled mobility device <NUM> as shown in <FIG>, swivel wheels <NUM> are located at the rear of the device. Alternatively, swivel wheels <NUM> may be located at the front of the device while drive wheels <NUM> may be located at the rear. As another example, drive wheels <NUM> may be located near the center chassis <NUM> with two sets of swivel wheels <NUM>, e.g., one set being located at the front of wheeled mobility device <NUM>, and the other at the rear.

In some cases, steering of wheeled mobility device <NUM> may be achieved by separate control of speeds of rotation of two different support wheels <NUM>. In some cases, the speed of rotation may be controlled by controlling a voltage that is applied to a motor of wheel drive <NUM> (e.g., via electrical unit <NUM>). For example, rotating one of drive wheels <NUM> more rapidly about its axis (e.g., axle) than the other drive wheel <NUM> may turn wheeled mobility device <NUM> toward the more slowly rotating drive wheel <NUM>. In other cases, wheel drive <NUM> of may be configured to rotate one or more drive wheels <NUM> about a vertical axis in order to steer wheeled mobility device <NUM>.

Operation of drive wheels <NUM> may be controlled by a user that is riding wheeled mobility device <NUM>, or another user, by operating user controls <NUM> (e.g., via electrical unit <NUM>). For example, user controls <NUM> may include one or more joysticks, pushbuttons, switches, levers, keyboards, keypads, pointing devices, touch screens, head movement sensors, or other controls. Some or all of user controls <NUM> may be mounted on wheeled mobility device <NUM> (e.g., on an armrest or elsewhere) so as to be conveniently accessible by a user of wheeled mobility device <NUM>. In some cases, some or all of user controls <NUM> may be located on a remote device, e.g., so as to enable operation of user controls <NUM> by a user who is not currently riding wheeled mobility device <NUM>.

User support <NUM> may include one or more components for supporting a user in one or more of a sitting, standing, or other position. For example, a back panel <NUM> of user support <NUM> may be configured to support a user's back. Back panel <NUM> may serve as a backrest of a seat <NUM> when wheeled mobility device <NUM> is configured to support a user in a seated position (<FIG>). When wheeled mobility device <NUM> is configured to support a user in a standing position, back panel <NUM> may be harnessed to the user's back in order to hold the upper body of the user in an upright orientation (<FIG>). Similarly, when configured to support the user in an upright position, seat <NUM> may be turned vertically and may be harnessed to the user's midsection in order to support the midsection in a standing position. A foot panel <NUM> may be configured to support the user's feet when wheeled mobility device <NUM> is configured to support the user in both seated and standing positions.

Support conversion mechanism <NUM> may be operated (e.g., a motor of support conversion mechanism <NUM> operated in response to operation of user controls <NUM> and operation of electrical unit <NUM>) to change a configuration of user support <NUM>. Support conversion mechanism <NUM> may include one or more motors, actuators, hinges, or other components that may be operated to convert user support <NUM> from a seated configuration to a standing configuration, and vice versa.

During operation of support conversion mechanism <NUM>, one or more panels of user support <NUM> may rotate or bend relative to another. For example, seat <NUM>, which is substantially horizontal when user support <NUM> is in a seated configuration, may be rotated to a substantially vertical orientation during conversion to a standing configuration, and vice versa. A connector between panels of user support <NUM>, such as panel connection <NUM> between back panel <NUM> and seat <NUM>, may be configured to enable one or both of the connected panels to rotate. For example, panel connection <NUM> may be made of a flexible material or may be hinged (or may be absent), so as to enable seat <NUM> to rotate back-and-forth between a vertical and a horizontal orientation during operation of support conversion mechanism <NUM>.

For example, support conversion mechanism <NUM> may include a column or similar structure that may be extended (e.g., telescoped outward) or retracted (e.g., telescoped inward), rotated, or both, to raise or lower a support connection <NUM>. For example, with user support <NUM> in a seated configuration, raising support connection <NUM> may fold seat <NUM> inward from a horizontal to a vertical orientation, may raise back panel <NUM>, and may draw leg braces <NUM> and foot panel <NUM> proximally inward. Thus, support conversion mechanism <NUM> may convert user support <NUM> to a standing position. Similarly, with user support <NUM> in a standing configuration, lowering support connection <NUM> may fold seat <NUM> outward from a vertical to a horizontal orientation, may lower back panel <NUM>, and may extend leg braces <NUM> and foot panel <NUM> distally inward. Thus, support conversion mechanism <NUM> may convert user support <NUM> to a seated position.

Support conversion mechanism <NUM> and user support <NUM> may be configured to maintain a center of gravity of wheeled mobility device <NUM> in an approximately constant lateral and longitudinal position relative to chassis <NUM>. For example, the position of the center of gravity may be maintained approximately above a position of a geometric center of chassis <NUM> or a geographic center of the wheels (e.g., drive wheels <NUM> and support wheels <NUM>) of chassis <NUM>.

User support <NUM> is mounted on tiltable leveling structure <NUM>. Tiltable leveling structure <NUM> is configured to control an orientation of user support <NUM>. For example, tiltable leveling structure <NUM> may be configured to maintain an orientation at an orientation that is defined, e.g., with respect to the vertical or horizontal. Tiltable leveling structure <NUM> may include one or more displaceable connections <NUM> that are movable by actuators (e.g., as controlled by electrical unit <NUM>) to maintain the orientation of user support <NUM>.

Electrical unit <NUM> may include one or more components that enable operation of electrical or electronic components of wheeled mobility device <NUM>. Components of electrical unit <NUM> may be located in a single housing (as shown in <FIG>, or may be located in two or more separate housings at various locations).

<FIG> is a schematic block diagram of an electrical unit of the wheeled mobility device shown in <FIG>.

Electrical unit <NUM> may include a controller <NUM> and a power source <NUM>.

For example, power source <NUM> may include a storage battery, another type of battery, a solar panel, a generator, a connection to an external electrical power source (e.g., an electrical mains), or another source of electrical power.

Controller <NUM> may include a processor <NUM>. Processor <NUM> may include one or more processing units or computers. Processor <NUM> may be configured to operate in accordance with programmed instructions.

Processor <NUM> may communicate with data storage <NUM>. For example, data storage <NUM> may include one or more fixed or removable, volatile or non-volatile, remote or local, data storage units, memories, or computer-readable media. For example, data storage <NUM> may be utilized to store one or more of programmed instructions for operation of processor <NUM>, parameters or data that are utilized in executing programmed instructions, or results of execution of programmed instructions.

Processor <NUM> may be configured to operate in accordance with one or more signals that are received from sensors <NUM>. For example, sensors <NUM> may include one or more sensors that are configured to detect a tilt of a component of tiltable leveling structure <NUM> or of user support <NUM>. Sensors <NUM> may include one or more inertial measurement units, tilt sensors, accelerometers, gyroscopes, compasses, or other sensors that may be utilized to determine an orientation (e.g., yaw, pitch, roll) of tiltable leveling structure <NUM>, of user support <NUM>, or of chassis <NUM>. Sensors <NUM> may include sensors for measuring the tilt or slope of a surface that supports wheeled mobility device <NUM>. Sensors <NUM> may include a magnetometer or compass for measuring the orientation of mobility device <NUM> relative to the magnetic field of the Earth. Sensors <NUM> may include sensors for measuring a speed of rotation of one or more wheels (e.g., drive wheels <NUM> or support wheels <NUM>). Sensors <NUM> may include one or more navigation sensors for determining a geographic position of wheeled mobility device <NUM>. Sensors <NUM> may include force sensors for measuring a current load (e.g., weight) supported by wheeled mobility device <NUM>, a charge level of a battery of power source <NUM>, an impact, detecting an obstacle, or other types of sensors for detecting a potentially hazardous situation or other information.

Processor <NUM> may be configured to operate in accordance with control input that is received from one or more user controls <NUM>. For example, user controls <NUM> may be operated to indicate a desired orientation or direction of travel of wheeled mobility device <NUM>, a desired speed of travel of wheeled mobility device <NUM>, a desired configuration of user support <NUM> (e.g., seated or standing), or another indication of a command or preference by the user or another user or operator of wheeled mobility device <NUM>.

Controller <NUM> may include motor control <NUM>. Processor <NUM> may be configured to communicate with motor control <NUM> to control one or more motors. Motor control <NUM> may include one or more controllers that are each configured to control operation of one or more motors. For example, a motor that is controlled by motor control <NUM> may include a motor of a wheel drive <NUM>, a motor of support conversion mechanism <NUM>, or an actuator <NUM> of tiltable leveling structure <NUM>. Processor <NUM> may be configured to apply one or more algorithms to calculate an operation of the motors on the basis of operation of user controls <NUM> and on the basis of one or more quantities sensed by sensors <NUM>.

<FIG> schematically illustrates a self-leveling mechanism of a wheeled mobility device, in accordance with an embodiment of the present invention. <FIG> is a schematic oblique view from below of the self-leveling mechanism shown in <FIG> is a schematic enlarged view of a swivel connection of a tiltable leveling structure of the self-leveling mechanism shown in <FIG> is a schematic top view of the self-leveling mechanism shown in <FIG>.

Self-leveling mechanism <NUM> includes tiltable leveling structure <NUM> and linear actuator assemblies <NUM>. Linear actuator assemblies <NUM> are operable by controller <NUM> to adjust a tilt of tiltable leveling structure <NUM> in accordance with a tilt measured by inertial measurement unit <NUM>, or by another sensor of sensors <NUM>.

Shaft <NUM> of rod-end bearing <NUM> may be fixed to chassis floor <NUM> of chassis <NUM>. Swivel bar <NUM> is located near a distal end of arm <NUM> of tiltable leveling structure <NUM>. Swivel bar <NUM> may connect to (e.g., pass through a swivel opening <NUM> of) rod end bearing <NUM>. Shaft <NUM> holds the opening of rod-end bearing <NUM>, and thus swivel bar <NUM>, at a fixed nonzero distance (e.g., with value H<NUM>) above chassis floor <NUM>. The connection to rod-end bearing <NUM> forms swivel connection <NUM>. Swivel connection <NUM> may thus enable at least limited rotation of arm <NUM> and tiltable leveling structure <NUM> relative to shaft <NUM> and chassis <NUM>. The fixed distance H<NUM> may be sufficient such that neither chassis floor <NUM> nor another structure of chassis <NUM> interferes with tilting of tiltable leveling structure <NUM> (within a predetermined range of tilt angles, e.g., selected to be sufficient to enable self-leveling of user support <NUM> when wheeled mobility device <NUM> travels over a surface whose maximum slope is within a predetermined range of slope angles). User support <NUM>, including foot panel <NUM>, is fixed to tiltable leveling structure <NUM>. Thus, swivel connection <NUM> may enable sufficient tilting of user support <NUM> so as to maintain user support <NUM> in an approximately constant orientation with respect to the horizontal (typically constant roll and pitch angles with respect to the horizontal).

Linear actuator assemblies <NUM> are each configured to linearly displace one of displaceable connections 16a and 16b. Actuator base <NUM> of each linear actuator assembly <NUM> may be fixed to chassis floor <NUM>. For example, each actuator <NUM> may be configured to rotate an actuator shaft <NUM> with exterior threading. Each of displaceable connections 16a and 16b may include connection structure <NUM> that includes an opening, sleeve, or ring with corresponding interior threading. For example, the internal threading may be located in bore of ball swivel <NUM> of connection structure <NUM>. Ball swivel <NUM> may enable at least a limited change in orientation of actuator shaft <NUM> relative to tilt plate <NUM> or other structure of tiltable leveling structure <NUM>. Thus, rotation of actuator shaft <NUM> may displace displaceable connection 16a or 16b along actuator shaft <NUM> to increase or decrease a distance between the displaceable connection 16a or 16b and chassis floor <NUM>. In addition, actuator base <NUM> may be configured to enable actuator shaft <NUM> and actuator <NUM> rotate or tilt relative to chassis floor <NUM>, to enable tiltable leveling structure <NUM> to tilt relative to chassis floor <NUM>.

Alternatively to linear actuator assembly <NUM>, other structures or mechanisms may be used, e.g., scissor-jack motors, eccentric drives, a hydraulic mechanism, an electromagnetic mechanism, or another mechanism. In some such alternatives, displaceable connection 16a or 16b may be fixed to actuator shaft <NUM>. For example, actuator shaft <NUM> may be extendible to increase a distance between the corresponding displaceable connection 16a or 16b and chassis floor <NUM>. Actuator shaft <NUM> may be retractable to decrease the distance between the corresponding displaceable connection 16a or 16b and chassis floor <NUM>.

Each displaceable connection 16a or 16b is connected to an end of tilt plate <NUM>. Tilt plate <NUM> is fixed to arm <NUM> at junction <NUM>. Thus, raising or lowering displaceable connections 16a and 16b in tandem may raise or lower tilt plate <NUM> relative to swivel connection <NUM>. In the arrangement shown, with arm <NUM> extending forward and displaceable connections 16a or 16b located at lateral (right-left) ends of tilt plate <NUM>, the raising or lowering may change a pitch angle of arm <NUM>, and thus of user support <NUM>. Raising or lowering one of displaceable connections 16a and 16b relative to the other may change a lateral tilt of tilt plate <NUM>. In the arrangement shown, the raising or lowering of one of displaceable connections 16a and 16b relative to the other may change a roll angle of arm <NUM>, and thus of user support <NUM>. Alternative orientations of arm <NUM> and of displaceable connections 16a and 16b relative to a direction of forward motion of wheeled mobility device <NUM> (e.g., arm <NUM> extending backward or to one side, with moveable points 16a and 16b being correspondingly located) may be provided.

Tiltable leveling structure <NUM> is provided with inertial measurement unit <NUM>, or another sensor of sensors <NUM>, for measuring a tilt of tiltable leveling structure <NUM>. For example, inertial measurement unit <NUM> may be mounted on arm <NUM> (as shown), on tilt plate <NUM>, on foot panel <NUM>, or elsewhere on tiltable leveling structure <NUM> or user support <NUM>.

Processor <NUM> may be configured to control operation of actuators <NUM> in accordance with tilt angles that are sensed by inertial measurement unit <NUM> or by another type of sensor <NUM>, or that are calculated from quantities that are measured by inertial measurement unit <NUM> or another sensor <NUM>.

<FIG> schematically illustrates operation of a tiltable leveling structure of a wheeled mobility device, in accordance with an embodiment of the present invention. <FIG> schematically illustrates a cross sectional view along a lateral axis of the tiltable leveling structure shown in <FIG>, illustrating roll angle control. <FIG> schematically illustrates a cross sectional view along a longitudinal axis of the tiltable stabilizing structure shown in <FIG>, illustrating pitch angle control.

For the sake of simplicity, tiltable stabilizing structure <NUM> is represented in <FIG> by a representative plane <NUM>. When tiltable stabilizing structure <NUM> is in a quiescent state, e.g., when wheeled mobility device <NUM> is standing on a level horizontal surface or tiltable stabilizing structure <NUM> or user support <NUM> otherwise have a target orientation, the representative plane <NUM> is parallel to a target plane <NUM>. For example, target plane <NUM> may be horizontal, or have another orientation that is preferred by a user of wheeled mobility device <NUM>. (For example, a particular user may feel comfortable leaning slightly backward or forward, to the right or left, or at another target orientation.

Representative plane <NUM> may be understood to represent a plane that is defined by swivel connection <NUM> and by displaceable connections 16a and 16b. In this case, projected displaceable connections 58a and 58b are identical with displaceable connections 16a and 16b, respectively, with the tilt of target plane <NUM> adjusted accordingly (e.g., target plane <NUM> may not be horizontal when a component of wheeled mobility device <NUM>, such as seat <NUM>, is to be maintained horizontal).

Alternatively, representative plane <NUM> may be defined such that the tilt of target plane <NUM> is identical to the tilt at which a component of wheeled mobility device <NUM>, such as seat <NUM>) is to be maintained (e.g., as defined with respect to the local horizontal and vertical). In this case, representative plane <NUM> of tiltable leveling structure <NUM> may be determined by initially defining a plane that is parallel to particular longitudinal axis <NUM> (e.g., an axis that is parallel to a projection of direction of forward motion <NUM> into target plane <NUM>) and that includes displaceable connections 16a and 16b. Representative plane <NUM> then is a plane parallel to this defined plane that includes swivel connection <NUM>. Projected displaceable connections 58a and 58b represent projections of displaceable connections 16a and 16b, respectively, into representative plane <NUM> along a line of translation of each displaceable connection 16a or 16b. For example, the line of translation of displaceable connection 16a or 16b may be the axis of its corresponding actuator shaft <NUM>. Thus, a displacement of projected displaceable connection 58a or 58b is equal to a displacement of the corresponding displaceable connection 16a or 16b.

In the configuration shown, swivel connection <NUM> is located at or near a lateral midpoint of a front end of representative plane <NUM>, the front end being determined by direction of forward motion <NUM>. Projected displaceable connections 58a and 58b are located near left and right corners, respectively, of a rear end of representative plane <NUM>. Other placements of swivel connection <NUM> and of projected displaceable connections 58a and 58b (corresponding to other configurations of tiltable stabilizing structure <NUM>) may be provided.

A tilt of tiltable stabilizing structure <NUM> may be characterized with reference to a target plane <NUM>.

Representative plane <NUM> is characterized by longitudinal axis <NUM> (substantially parallel to direction of forward motion <NUM>), and by lateral axis <NUM> (substantially perpendicular to longitudinal axis <NUM>). A tilt resulting from a rotation of tiltable stabilizing structure <NUM> about lateral axis <NUM> with respect to target plane <NUM> may be quantified as pitch angle <NUM> (with value θP). Similarly, a tilt resulting from a rotation of tiltable stabilizing structure <NUM> about longitudinal axis <NUM> with respect to target plane <NUM> may be quantified as roll angle <NUM> (with value θR). Values θP of pitch angle <NUM> and θR of roll angle <NUM> may be measured by inertial measurement unit <NUM>, or by a similar sensor.

Swivel connection <NUM> is located a constant distance <NUM> (with constant value H<NUM>) from chassis floor <NUM>. Distance <NUM> is sufficient such that when chassis <NUM> or wheeled mobility device <NUM> standing or travelling over a surface that is sloped within a predetermined range of slopes, projected displaceable connections 58a and 58b (and displaceable connections 16a and 16b) may be moved toward chassis floor <NUM> so as to maintain representative plane <NUM> in an orientation that is parallel to target plane <NUM>. For example, a maximum slope that is to be accommodated by motion of displaceable connections 16a and 16b may be a maximum slope upon which wheeled mobility device <NUM> may safely travel.

Each of projected displaceable connections 58a and 58b is at a variable distance 56a or 56b, respectively (with changeable values H<NUM> and H<NUM>, respectively, e.g., within the range zero to <NUM><NUM>), from chassis floor <NUM>. Variable distance 56a, 56b, or both, may be changed by operating one or more actuators <NUM>. In <FIG>, projected displaceable connection <NUM> represents a point where a line through projected displaceable connections 58a and 58b intersects the plane of the section shown in <FIG>. Projected displaceable connection <NUM> is at a distance <NUM> from chassis floor <NUM>.

An iterative control algorithm may be applied by processor <NUM> to control operation of actuators <NUM> via motor control <NUM>.

<FIG> is a flowchart depicting a method for controlling a tiltable leveling structure of a wheeled mobility device, in accordance with an embodiment of the present invention. <FIG> is a block diagram of a control algorithm of the method depicted in <FIG>.

It should be understood, with respect to any flowchart or block diagram referenced herein, that the division of the illustrated method into discrete operations represented by blocks of the flowchart or block diagram has been selected for convenience and clarity only. Alternative division of the illustrated method into discrete operations is possible with equivalent results. Such alternative division of the illustrated method into discrete operations should be understood as representing other embodiments of the illustrated method.

Similarly, it should be understood that, unless indicated otherwise, the illustrated order of execution of the operations represented by blocks of any flowchart referenced herein has been selected for convenience and clarity only. Operations of the illustrated method may be executed in an alternative order, or concurrently, with equivalent results. Such reordering of operations of the illustrated method should be understood as representing other embodiments of the illustrated method.

Tilt control method <NUM> may be executed by processor <NUM> of wheeled mobility device <NUM>. For example, tilt control method <NUM> may be executed continually while power source <NUM> is switched on, while wheel drive <NUM> is operating, upon operation of a user control <NUM> to move or change a configuration of wheeled mobility device <NUM>, or in response to another predetermined event or condition.

One or more algorithm parameters <NUM> used in application of a control algorithm <NUM> may be predetermined or predefined (block <NUM>). Such algorithm parameters <NUM> may include one or more gain factors, one or more factors related to operation of actuators <NUM>, or other parameters used in application of control algorithm <NUM>. For example, the parameters may include gain adjustment factors KP and KR, exponents p and r, length conversion factor Δ, or other parameters that are utilized during application of control algorithm <NUM> as described below. Algorithm parameters <NUM> may be defined, for example, during development of a model of a wheeled mobility device <NUM>, during production, adjustment, maintenance or calibration of a particular wheeled mobility device <NUM>, or otherwise. Algorithm parameters <NUM> may be adjusted in accordance with preferences of a user of a particular wheeled mobility device <NUM>. For example, algorithm parameters <NUM> may affect smoothness or jerkiness of motions, preferred speed of motion, another user preference, or another characteristic of operation of wheeled mobility device <NUM>.

One or more target plane parameters <NUM> may be predetermined or predefined for characterizing target plane <NUM> (block <NUM>). Target plane parameters <NUM> may include roll and pitch angles, or other parameters that define target plane <NUM>. For example, target plane parameters <NUM> may be defined during calibration, adjustment, or maintenance of a particular wheeled mobility device <NUM>, during adaption of a particular wheeled mobility device <NUM> to a particular user, or at another time.

Target plane parameters <NUM> may include, for example, a target pitch angle ΘP and a target roll angle ΘR. For example, ΘP = <NUM> and ΘR = <NUM> may indicate that tiltable leveling structure <NUM> and representative plane <NUM> are to be maintained horizontal. Values of ΘP > <NUM> may indicate a preference for a backward tilt, while ΘP < <NUM> may indicate a preference for a forward tilt. Tilt control method <NUM> is configured to adjust a tilt of tiltable stabilizing structure <NUM> with the goal of maintaining representative plane <NUM> parallel to target plane <NUM>.

Execution of tilt control method <NUM> includes a series of iterations. During each iteration, operation of actuators <NUM> is controlled in accordance with measurements and calculations that are made during that iteration. In the following, each iteration is numbered with an index i.

Measured values of tilt angles of tiltable leveling structure <NUM> at the current iteration i may be obtained (blocks <NUM> and <NUM>). For example, the measured tilt angles may include pitch angle θP(i) and roll angle θR(i), or another set of angles that defines a tilt of tiltable stabilizing structure <NUM>. The tilt angle measurements may be received from inertial measurement unit <NUM>, or from another sensor. Alternatively or in addition, the tilt angle measurements may be obtained by analysis of received signals that indicate one or more measured quantities that are related to the tilt angles.

A displacement of each of displaceable connections 16a and 16b to be applied during the current iteration may be calculated based on a deviation of the measured (block <NUM>). In some cases, the calculation may be considered to include the following steps:
A deviation εP = θP(i) - ΘP of measured pitch angle θP(i) from target pitch angle ΘP may be calculated. A pitch gain factor GP(i) may be calculated as <MAT> where KP is a multiplicative factor and p is an exponent (block 230a).

The gain may be converted to pitch deviation distance DP(i) by multiplying pitch gain factor GP(i) by length conversion factor Δ: <MAT>.

Similarly, a deviation εR = θR(i) - ΘR of measured roll angle θR(i) from target roll angle ΘR may be calculated. A roll gain factor GR(i) may be calculated as <MAT> where KR is a multiplicative factor and r is an exponent (block 230b).

The gain may be converted to roll deviation distance DR(i) by multiplying roll gain factor GR(i) by length conversion factor Δ: <MAT>.

A displacement of each of displaceable connections 16a and 16b in order to correct the deviations εP(i) and εR(i) may be calculated on the basis of the deviation distances DP(i) and DR(i) (block <NUM>). The calculated displacements are configured to reduce the values of εP(i) and εR(i) at the start of the next iteration (e.g., in the absence of any further change in the tilt of chassis <NUM> such as would be caused, e.g., by a change in slope of terrain or another surface that supports wheeled mobility device <NUM>) to a value that is close to zero.

The displacements may be calculated as linear combinations of the deviation distances DP(i) and DR(i). For example, displaceable connection 16a (and, equivalently, projected displaceable connection 58a), at current distance H<NUM>(i) from chassis floor <NUM>, may be displaced such that: <MAT>.

Similarly, displaceable connection 16b (and, equivalently, projected displaceable connection 58b), at current distance H<NUM>(i) from chassis floor <NUM>, may be displaced such that: <MAT>.

The displacements of H<NUM> and H<NUM> may be expressed in units of length (e.g., millimeters or centimeters), a rotation angle or number of rotations of actuator <NUM> (e.g., turning a screw of a screw mechanism, as shown, a screw of a scissor jack mechanism, an eccentric disk, or another mechanism for converting rotation of a motor to linear motion), or otherwise.

The actuator <NUM> associated with each of displaceable connections 16a and 16b be operated to achieve the calculated displaced distances from chassis floor <NUM>, H<NUM>(i + <NUM>) and H<NUM>(i + <NUM>), respectively, during the current iteration (block <NUM>).

For example, a speed and direction of operation of each actuator <NUM> may be controlled (e.g., via operation of motor control <NUM>) to achieve the calculated displaced distance by the start of the following iteration (returning to blocks <NUM> and <NUM>). In some cases, the speed of operation of each actuator <NUM> may be limited such that a rate of tilting of tiltable leveling structure <NUM> is in the range <NUM> degree per second to <NUM> degrees per second, e.g., about <NUM> degrees per second.

When one or both of exponents p and r are greater than zero (e.g., p = r = <NUM>, or p or r being equal to another positive number), such that the absolute value of εP and εR is raised to a positive power, the calculated deviation distances DP and DR are proportionally greater for greater measured deviations εP and εR than for smaller deviations. In this case, the changes in distances H<NUM> and H<NUM> during a single iteration are larger for large deviations than for small deviations. Thus, in the case of a large deviation, the orientation of tiltable leveling structure <NUM> is rapidly returned to that of target plane <NUM>. Such rapid return to the target orientation may enable wheeled mobility device <NUM> to travel safely over surfaces of varying slope. One the other hand, when the deviations are small, the tilt of tiltable stabilizing structure <NUM> is varied slowly, enabling a smooth ride for the user of wheeled mobility device <NUM>. In this case, the control loop may be described as having an adaptive bandwidth: wider for larger errors and narrower for smaller errors.

On the other hand, when the values of the exponents are zero, p = r = <NUM>, the calculated deviation distances DP and DR, and thus the changes in distances H<NUM> and H<NUM>, are independent of deviations εP and εR.

Values of exponents p and r, as well as those of factors KP, KR, and Δ, may be selected in accordance with one or more of properties or characteristics of a particular or representative wheeled mobility device <NUM>, of a preference of a particular or representative user of wheeled mobility device <NUM>, or otherwise.

A user self-leveling apparatus for wheeled mobility device <NUM> and a tilt control method <NUM>, in accordance with an embodiment of the present invention, may be advantageous over other types of self-leveling systems. In particular, the mechanism for tilting tiltable stabilizing structure <NUM>, using linear actuators and a fixed swivel connection <NUM>, may be advantageous over double-gimbal mechanism with angular actuators for producing two mutually orthogonal rotations.

For example, the mechanism for tilting tiltable leveling structure <NUM> may occupy less space, require less maintenance, and may be less expensive than a typical double-gimbal mechanism. Actuators <NUM> produce linear translation only and are not orthogonal to each other (such that movement of each of displaceable connections 16a and 16b affects both roll and pitch), For example, control algorithm <NUM> may be robust, simpler, and more easily configured than an algorithm for controlling a double-gimbal mechanism. The control algorithm <NUM> is configured to always converge to the orientation of representative plane <NUM> that of target plane <NUM>, even in the presence of small mechanical inaccuracies such as backlash.

Claim 1:
A mobility device (<NUM>) for supporting a user in a sitting, a standing, or other position comprising:
a chassis (<NUM>) configured to propel the mobility device on a surface; and
a self-leveling mechanism (<NUM>) comprising:
a leveling structure (<NUM>) on which a user support (<NUM>) for supporting a user of the mobility device is mounted, wherein the leveling structure is connected to the chassis (<NUM>) by a swivel connection (<NUM>) that enables pitch and roll motion of the leveling structure and by two linearly displaceable connections (16a, 16b) that are laterally displaced from one another;
two linear actuators (<NUM>), each of which is configured to displace a displaceable connection of the two displaceable connections (16a, 16b) to adjust a distance between the user support and the chassis (<NUM>);
a sensor (<NUM>) for sensing a tilt of the leveling structure (<NUM>) with respect to a predetermined plane that is configured to measure a pitch angle and a roll angle of the user support (<NUM>); and
a controller (<NUM>) configured to to operate the linear actuators (<NUM>) in accordance with a tilt that is sensed by the sensor (<NUM>) for maintaining the orientation of the user support (<NUM>),
characterised by the controller (<NUM>) being configured to apply an iterative adaptive control algorithm to calculate a displacement of one or both of the displaceable connections in accordance with a deviation of the measured pitch angle from a pitch angle of a target plane or a deviation of the measured roll angle from a roll angle of the target plane, and
wherein the size of the calculated displacement during a single iteration of the control algorithm increases when the deviation increases and decreases when the deviation decreases,
a support conversion mechanism (<NUM>) to convert the user support (<NUM>) from a seated configuration to a standing configuration, and vice versa,
wherein the user support (<NUM>) of the leveling structure (<NUM>) is configured to support the user during sitting, standing, or other positions.