Control of a transporter based on attitude

Abstract

A transporter for transporting a load over a surface. The transporter includes a support platform for supporting the load. The support platform is characterized by a fore-aft axis, a lateral axis, and an orientation with respect to the surface, the orientation referred to as an attitude. At least one ground-contacting element is flexibly coupled to the support platform in such a manner that the attitude of the support platform is capable of variation. One or more ground-contacting elements are driven by a motorized drive arrangement. A sensor module generates a signal characterizing the attitude of the support platform. Based on the attitude, a controller commands the motorized drive arrangement.

Claims

1. A method for steering a transporter, the transporter having a support platform flexibly coupled to at least two laterally-disposed wheels, each of the at least two laterally-disposed wheels being associated with a separate motor, a controller calculating torque for each of the separate motors individually, the controller commanding a motorized drive arrangement, the method comprising: calculating, by the controller, a first torque for one of the separate motors and a second torque for another of the separate motors, the first torque and the second torque based at least on a signal characterizing an attitude of the support platform; commanding, by the controller, the motorized drive arrangement to apply the first torque to one of the at least two laterally-disposed wheels through the one of the associated separate motors and the second torque to another of the at least two laterally-disposed wheels through the other of the associated separate motors; and tracking a first wheel motion of one of the at least two laterally-disposed wheels and a second wheel motion of another of the at least two laterally-disposed wheels to adjust the first torque and the second torque to adjust turning of the transporter.

2. The method as in claim 1 further comprising: sensing the attitude based on a distance sensor electronically coupled with the controller.

3. The method as in claim 2 further comprising: sensing, by the distance sensor, at least two distances; and adjusting the first torque and the second torque based on a comparison between the at least two distances.

4. The method as in claim 1 further comprising: determining the attitude based on user input; and adjusting the first torque and the second torque based on the determined attitude.

5. The method as in claim 4 wherein the user input comprises a position of a center of mass of a load on the support platform.

6. The method as in claim 4 further comprising: determining the attitude based on a power strut controlled by the user input.

7. The method as in claim 1 further comprising: determining the attitude based on a power strut controlled remotely.

8. A transporter comprising: at least two laterally-disposed wheels, each of the at least two laterally-disposed wheels being associated with a separate motor; a support platform flexibly coupled to the at least two laterally-disposed wheels; a motorized drive arrangement driving each of the at least two laterally-disposed wheels associated with the separate motors individually; and a controller commanding the motorized drive arrangement, the controller calculating a first torque for one of the separate motors and a second torque for another of the separate motors, the first torque and the second torque based at least on a signal characterizing an attitude of the support platform, the controller commanding the motorized drive arrangement to apply the first torque and the second torque to the at least two laterally-disposed wheels, the controller tracking a first wheel motion of one of the at least two laterally-disposed wheels and a second wheel motion of another of the at least two laterally-disposed wheels to adjust turning of the transporter, wherein the motorized drive arrangement provides the first torque to one of the at least two laterally-disposed wheels through the one of the associated separate motors and the second torque to another of the at least two laterally-disposed wheels through the other of the associated separate motors.

9. The transporter as in claim 8 further comprising: a pivot mechanism flexibly coupling the at least two laterally-disposed wheels to the support platform.

10. The transporter as in claim 8 further comprising: a compliant member flexibly coupling the at least two laterally-disposed wheels to the support platform.

11. The transporter as in claim 8 wherein the support platform comprises a fore-aft axis and a lateral axis.

12. The transporter as in claim 8 wherein the attitude comprises an orientation with respect to the ground.

13. The transporter as in claim 8 further comprising: a sensor module determining the attitude, the sensor module being coupled to the controller.

14. The transporter as in claim 13 wherein the sensor module comprises at least one distance sensor, the at least one distance sensor measuring a measured distance characteristic of the attitude of the support platform.

15. The transporter as in claim 14 wherein the measured distance characteristic comprises a distance between a fiducial point on the support platform and the ground.

16. The transporter as in claim 14 further comprising: a reflector reflecting a distance signal generated by the at least one distance sensor.

17. The transporter as in claim 16 wherein a distance from the at least one distance sensor to the ground is calculated based on a time or phase difference between when the distance signal was generated by the at least one distance sensor and when the reflected distance signal is received by a sensor receiver.

18. The transporter as in claim 14 wherein the at least one distance sensor comprises at least one contact sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing features of the invention will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

(2) FIG. 1 depicts one embodiment of a human transporter, lacking a distinct user input device, to which the present invention may advantageously be applied;

(3) FIG. 2 is a side view of a transporter, in accordance with one embodiment of the invention;

(4) FIG. 3 is an expanded side view of a transporter, in accordance with one embodiment of the invention;

(5) FIG. 4 is a side view of a transporter, in accordance with one embodiment of the invention; and

(6) FIG. 5 is a block diagram of a controller of a transporter, in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

(7) In accordance with one embodiment of the invention, FIG. 1 shows a transporter, 1 lacking a distinct input device, to which the present invention may advantageously be applied. Transporter 1 is described in detail in U.S. Pat. No. 6,302,230, which is incorporated herein by reference in its entirety. Transporter 1 includes a support platform 11 for supporting a load, which may be a living subject 9, over the ground or other surface, such as a floor, which may be referred to herein generally as ground. A subject, for example, may stand or sit on support platform 11. Attached to support platform 11 may be a handlebar 12 that can be gripped when riding transporter 1.

(8) One or more ground-contacting elements 2, 7 provide contact between support platform 11 and the ground. Ground-contacting elements 2, 7 may include, but are not limited to, arcuate members, tracks, treads, and wheels (hereinafter the term wheel will be used in the specification to refer to any such ground-contacting element without limitation). While the transporter 1 depicted in FIG. 1 lacks stability in its operating position unless subject to controlled balancing, the application of the present invention is specifically not limited to transporters of that sort and embodiments of the present invention may advantageously be applied to statically stable transporters as well.

(9) Support platform 11 may be flexibly coupled to the wheels 2, 7 by various means known in the art, for example, a pivot mechanism, springs, or pneumatic pistons. In other embodiments, the wheels 2, 7 may have some compliance and serve the function of a spring. For purposes of the present description, platform 11 may be characterized by a fore-aft axis, a lateral axis, and an orientation with respect to the surface, which is referred to herein as an attitude. The fore-aft axis, X-X, is perpendicular to the wheel axis, while the lateral axis, Y-Y, is parallel to the axis of the wheels. Directions parallel to the axes X-X and Y-Y are called the fore-aft and lateral directions respectively.

(10) Referring now to FIG. 2, which shows a transporter 10 in accordance with one embodiment of the invention, the attitude of support platform 11 may, for example, be capable of variation based on a position of a center of mass of the load relative to one or more wheels 13, 14. Alternatively, transporter 10 may include a power strut or other mechanism capable of altering the attitude of the support platform 11. The power strut may be controlled by a user interface located on transporter 10, such as a joystick or a rotatable potentiometer located on handlebar 12. In other embodiments, the power strut may also be controlled by a remote control device, such as, but not limited to, an infrared or radio controlled remote control device.

(11) The motion of transporter 10 is based, at least in part, on the attitude of the support platform 11. To determine the attitude of the support platform 11, transporter 10 includes a sensor module. Sensor module may include at least one distance sensor 17, 18 for measuring a distance characteristic of the attitude of the support platform 11. The distance measured may be, for example, the distance between a fiducial point on the support platform 11 and a surface 19, or alternatively, another component on transporter 10. A plurality of distances measured by the sensor module may be combined to generate at least one signal characteristic of the platform attitude.

(12) Attitude/distance sensor may be one of many sensor types, such as, for example, an ultrasonic, optical, acoustic or radar sensor wherein a signal generated by a source is reflected back by a surface to a sensor receiver. The distance from the sensor to the surface can then be calculated based on the time (or phase) difference between when the signal was generated and when the reflected signal was received. Triangulation may be performed. In other embodiments, distance sensor can be a contact sensor(s) such as, without limitation, a whisker(s). For example, a plurality of whiskers, each having a predetermined length may be utilized, with distance determined based on which whisker bends or is otherwise activated when making contact with the surface. A single whisker may be utilized with distance determined based, at least on part, on the bending angle of the whisker.

(13) Referring to FIG. 2, distance sensors 17, 18 sense the distance between a fiducial point on the platform and a position on the surface that is disposed at a specified angle 3, 4, with respect to the support platform. First distance sensor 17 is located at the front (fore) of platform 11 and senses a first distance 5 between platform 11 and surface 19.

(14) Second distance sensor 17 is located at the back (aft) of platform 11 and senses a second distance 6 between platform 11 and surface 19. By comparing distances 5 and 6, a signal indicative of an attitude of the platform 11, and more specifically, the inclination of the platform 11 in the fore-aft plane with respect to the surface 19, can be determined.

(15) In another embodiment, at least one distance sensor 22 may sense the distance between a fiducial point on the transporter platform 11 and a first component 23 that remains in a substantially fixed vertical position relative to the surface 19, as shown in the expanded view of a transporter in FIG. 3. First component 23 may be, for example, a wheel axle 23 or a frame used to support the at least one wheel 14. In various embodiments, first component 23 may include a reflector for reflecting the signal generated by distance sensor 22.

(16) FIG. 4 shows a transporter 60 that includes a first support platform 69 and a second support platform 61, in accordance with one embodiment of the invention. At least one wheel 63 and 64 provides contact between the first support platform 69 and the ground. Second support platform 61 is coupled to the first support platform 69 such that the second support platform 61 can tilt in the fore-aft plane based, for example, on a position of a center of mass of the loaded second support platform 61. Second support platform 61 may be tiltably attached to the first support platform 69 using, without limitation, springs 65 and 66 and/or a pivot mechanism 68. Similar to above-described embodiments, based on the tilting of the second support platform 61, at least one sensor 67 and 70 generates a signal indicative of the attitude of the second support platform 61. Attached to the first support platform 69 or second support platform 61 may be a handlebar 62 that can be gripped while operating the transporter 60.

(17) A controller receives the signal characteristic of the attitude from the sensor module. Based at least on this signal, the controller implements a control algorithm to command a motorized drive arrangement so as to drive the at least one wheel. The controller may also respond to commands from other operator interfaces, such as a joystick or dial attached, for example, to handlebar.

(18) FIG. 5 shows a controller 30 for controlling the motorized drive of the transporter, in accordance with one embodiment of the invention. Controller 30 receives an input characteristic of platform attitude from sensor module 34. Based at least on the input from the sensor module, controller 30 commands at least one motorized drive 35, 36. Controller 30 also interfaces with a user interface 31 and a wheel rotation sensor 33.

(19) User interface 31 may include, among other things, controls for turning the controller 30 on or off. When the controller 30 is turned off, the at least one wheel of the transporter may be free to move, such that the transporter acts as a typical push scooter. User interface 31 may also control a locking mechanism 32 for locking the at least one wheel.

(20) The controller 30 includes a control algorithm to determine the amount of torque to be applied to the at least one wheel based on the sensed attitude of the support platform. The control algorithm may be configured either in design of the system or in real time, on the basis of current operating mode and operating conditions as well as preferences of the user. Controller may implement the control algorithm by using a control loop. The operation of control loops is well known in the art of electromechanical engineering and is outlined, for example, in Fraser & Milne, Electro-Mechanical Engineering, IEEE Press (1994), particularly in Chapter 11, Principles of Continuous Control which is incorporated herein by reference.

(21) As an example, and not meant to be limiting, the control algorithm may take the form:
Torque Command to Wheel=K[+O] where K=gain =support platform attitude, and O=offset.

(22) The support platform attitude, , may be in the form of an error term defined as the desired support platform attitude minus the measured support platform attitude. The gain, K, may be a predetermined constant, or may be entered/adjusted by the operator through user interface 31. Responsiveness of the transporter to attitude changes can be governed by K. For example, if K is increased, a rider will perceive a stiffer response in that a small change in platform attitude will result in a large torque command. Offset, O, may be incorporated into the control algorithm to govern the torque applied to the motorized drive, either in addition to, or separate from, the direct effect of . Thus, for example, the user may provide an input by means of a user interface of any sort, the input being treated by the control system equivalently to a change, for example, in platform attitude.

(23) Thus, referring back to FIG. 2, motion of the transporter 10 maybe controlled by a subject changing the attitude of the platform 11. This change in attitude is reflected by distances 5, 6 sensed by the sensor module. Depending on the control algorithm, an initial change in attitude, such that first distance 5 is less than second distance 6, may result in positive torque being applied to one or more wheels 23, 24, causing the wheels 23, 24 to move forward. Likewise, an initial change in the attitude, such that first distance 5 is greater than second distance 6 may result in a negative torque applied to one or more wheels 23, 24, causing the wheels 23, 24 to move in the aft direction. If the subject then remains in his changed position on the platform such that the platform attitude remains the same, the motor will continue to torque at approximately the same rate.

(24) In various embodiments of the invention, the sensor module may sense changes in platform attitude in addition to, or instead of inclination of support platform in the fore-aft plane. For example, sensor module may provide an attitude signal indicative of inclination of the support platform in the lateral plane relative to the surface. This may be accomplished by the use of two laterally disposed distance sensors. Changes in the angle of inclination of the support platform in the lateral plane can then be used either separately or in combination with other attitude changes to control motion of the transporter. For example, changes in the angle of inclination in the fore-aft plane can be used to control fore-aft motion, while changes in the angle of inclination in the lateral plane can be used to control steering of the transporter.

(25) Steering may be accomplished in an embodiment having at least two laterally disposed wheels (i.e., a left and right wheel), by providing separate motors for left and right wheels. Torque desired for the left motor and the torque desired for the right motor can be calculated separately. Additionally, tracking both the left wheel motion and the right wheel motion permits adjustments to be made, as known to persons of ordinary skill in the control arts, to prevent unwanted turning of the vehicle and to account for performance variations between the two motors.

(26) The described embodiments of the invention are intended to be merely exemplary and numerous variations and modifications will be apparent to those skilled in the art. All such variations and modifications are intended to be within the scope of the present invention as defined in the appended claims.