Apparatus and method for a pitch state estimator for a personal vehicle

• US 6,332,103 B1
• Filed: 12/09/1999
• Issued: 12/18/2001
• Est. Priority Date: 06/30/1999
• Status: Expired due to Term

• Current Assignee: Deka Products Limited Partnership
• Original Assignee: Deka Products Limited Partnership
• Inventors: Amsbury, Burl, Steenson, James Henry Jr.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): ARTHUR JEANGLAUDE, GERTRUDE
• Application Number:
  US09/458,148
• Time in Patent Office: 740 Days
• Field of Search: 701/1, 701/4, 701/29, 701/33, 701/38, 701/50, 701/58, 701/60, 701/63, 701/124, 180/7.1, 180/8.2, 180/907, 37/348, 172/3, 172/9, 345/158
• US Class Current: 701/1
• CPC Class Codes: A61G 2203/42 for inclination
• CPC Class Codes: A61G 5/04 motor-driven A61G5/06 takes precedence; motor-operated rests A61G5/12; for vehicles with handlebars, equipped with three or more wheels B62K5/003, B62K5/023
• CPC Class Codes: B60G 2400/0512 Pitch angle
• CPC Class Codes: B60G 2600/1875 Other parameter or state estimation methods not involving the mathematical modelling of the vehicle
• CPC Class Codes: G05D 1/0891 specially adapted for land vehicles

Abstract

An apparatus and method for a pitch state estimator is provided. The pitch state estimator generates a pitch state signal for establishing the orientation used in the control of a ground-traversing vehicle. The vehicle has a support for supporting a load which is preferably a human passenger. In one embodiment, the pitch state estimator includes a pitch sensor connected to the vehicle producing a pitch signal representing an estimate of a pitch angle of the vehicle. The pitch angle is associated with a coordinate system referenced to gravity. The pitch state estimator also includes at least one inertial reference sensor connected to the vehicle producing an inertial orientation signal with respect to the vehicle. Further included is a state estimator module for receiving the pitch signal and the inertial orientation signal and calculating a pitch state signal from the inertial orientation signal and the pitch signal sensor. The pitch state signal is provided to a control loop of the vehicle for dynamically maintaining stability of the vehicle.

Claims

1. A system for estimating a pitch state of a ground-traversing vehicle, the system comprising:

a tilt sensor connected to the vehicle producing a pitch signal representing an estimate of a pitch angle of the vehicle about an E-frame of reference;

at least one inertial reference sensor connected to the vehicle producing an inertial orientation signal about a V-Frame of reference; and

a state estimator module receiving the pitch signal and the inertial orientation signal and calculating a pitch state signal from the inertial orientation signal and the pitch signal;

wherein the pitch state signal is provided to a control loop of the vehicle for dynamically maintaining stability of the vehicle.

2. A system according to claim 1, wherein a pitch-angle error signal is calculated based on the pitch signal and the inertial orientation signal and is fed back to the state estimator module to adjust the inertial orientation signal.

3. The system according to claim 1, wherein the at least one inertial reference sensor is a gyroscope.

4. The system according to claim 1, wherein the at least one inertial reference sensor comprises at least three gyroscopes.

5. The system according to claim 4, further comprising a virtual-gyro construction module for receiving the inertial orientation signals of the at least three gyroscopes and outputting to the state estimator module three rotation rate signals, wherein each rotation rate signal represents a rotation rate about one axis of three perpendicular axes.

6. The system according to claim 5, wherein the state estimator module further comprises:

a rotation transformation module which transforms the three rotation rate signals producing three E-frame of reference rotation rate signals; and

an integrator module for producing orientation angles based on the three rotation rate signals.

7. The system according to claim 6, wherein the rotation transformation module performs a small angle Euler transformation.

8. The system according to claim 7, wherein the state estimator further comprises a summer which receives the orientation angles and a tilt sensor signal, the summer outputting an error signal.

9. The system according to claim 8 wherein the state estimator further includes an inverse small angel Euler transform module which receives the error signal and the producing a distributed error signal.

10. The system according to claim 9, wherein the state estimator module further includes a gyro-bias integrator which calculates a bias signal based at least on the distributed error signal and the orientation angles, the bias signal being output to the summer;

wherein the output signal of the summer is fed back into the rotation transformation module.

11. The system according to claim 1, wherein the vehicle has at least two wheels, the state estimator module receives a wheel velocity signal representative of relative wheel velocities, the state estimator using the wheel velocity signal to calculate the yaw of the vehicle.

12. The method according to claim 11, further comprising:

calculating an angle error signal based in part on the digital tilt signal and the digital inertial orientation signals in a state estimator module; and

feeding back to the state estimator module the angle error signal.

13. The method according to claim 12, further comprising:

providing to a control loop of the vehicle the pitch state signal for dynamically maintaining stability of the vehicle.

14. The system according to claim 1, further comprising:

a fault detection module for detecting erroneous inertial orientation signals produced by the at least one inertial reference sensor.

15. The system according to claim 14, wherein the fault detection module generates a fault signal in response to the detection of an erroneous inertial orientation signal.

16. The system according to claim 15, wherein the state estimator module automatically switches from a three-axis estimate to a single axis estimate of the pitch state if a fault signal is created by the fault detection module.

17. A method for generating a pitch state signal used in the control of a ground-traversing vehicle, the method comprising:

measuring tilt of the vehicle with respect to gravity using an inclination sensor;

converting the tilt measurement into a digital tilt signal;

measuring the inertial orientation rates of the vehicle using at least three inertial sensors positioned in three or more non-collinear orientations on the vehicle;

converting the inertial orientation rate measurements of the three or more inertial orientation sensors into three or more digital inertial orientation signals; and

calculating a pitch state signal in a state estimator module based in part on the digital inertial orientation signals and the digital tilt signal.

18. The method according to claim 17, wherein the step of calculating includes the sub-steps of:

transforming the inertial orientation signals into three axial inertial orientation signals so that each signal corresponds to the orientation of one axis of three perpendicular axes;

transforming the three axial inertial orientation signals into gravity based orientation signals so that each signal corresponds to a gravity based orientation system;

transforming the three gravity based orientation signals into three angular signals, one signal representative of the pitch; and

providing the pitch to a control loop of the vehicle for dynamically maintaining stability of the vehicle.

19. A state estimator for estimating a pitch state of a vehicle, the state estimator comprising:

a processor for receiving a relative reference signal from each of a plurality of relative reference sensors and an absolute reference signal from an absolute reference sensor and determining a three axis pitch state of the vehicle;

wherein the processor automatically transitions to a single axis state estimation if a fault is declared by the processor.

20. A state estimator according to claim 19, wherein the state estimator further comprises:

a plurality of relative reference sensors each producing a relative reference signal coupled to the processor; and

an absolute reference sensor for producing an absolute reference signal coupled to the processor.

21. A state estimator according to claim 20, wherein the processor further comprises:

a virtual gyro construction module for transforming the signals from the relative reference sensors to signals representative of the projected relative reference signals on each of three perpendicular axes.

22. The state estimator according to claim 21, wherein the virtual gyro construction module performs a matrix transformation by multiplying the relative reference sensor signals by a construction matrix;

wherein the construction matrix is composed of coefficients which are selected from a combination of coefficients from an inverse least squares fit solution and coefficients representative of the relative reference sensor signals.

23. A state estimator according to claim 19, wherein the relative reference signals which are representative of rotation rate about a vehicle frame of reference are transformed to an absolute frame of reference through a small angle Euler transformation in the processor.

24. A state estimator according to claim 19, wherein the processor determines if a relative reference sensor is producing an erroneous signal by comparing a signal comprising of a combination of relative reference sensor signals to a predetermined value stored in a memory location associated with the processor.

25. A state estimator according to claim 24, wherein the combination signal is integrated with respect to time and the predetermined value is representative of an angle.

26. A state estimator according to claim 24, wherein the predetermined value is representative of an angle.

27. A state estimator according to claim 24, wherein the predetermined value is representative of a maximum rate.

28. A state estimator for measuring pitch state of a ground traversing vehicle, the state estimator comprising:

a second order filter receiving a relative reference signal from each of a plurality of relative reference sensors and an absolute reference signal from an absolute reference sensor and outputting a pitch state estimate of the vehicle.

29. The state estimator according to claim 28, wherein the filter is part of a processor.

30. A state estimator according to claim 29, wherein the processor switches between a three axis pitch estimate and a single axis pitch estimate if at least one relative reference sensor is determined faulty.

31. A computer program product for use on a computer system for determining a pitch state of a ground traversing vehicle, the computer program product comprising a computer usable medium having computer readable program code thereon, the computer readable program code including:

computer code for receiving a pitch signal and an inertial orientation signal;

computer code for calculating a pitch state signal from the pitch signal and the inertial orientation signal; and

computer code for sending the pitch state signal to a control loop of the vehicle for dynamically maintaining stability of the vehicle.

32. A computer program product according to claim 31, further comprising:

computer code for determining if an inertial orientation sensor has failed based in part on the inertial orientation signal;

computer code for switching from a three axis pitch state estimation to a single axis pitch state estimation if an inertial orientation sensor has failed.

33. A computer program product according to claim 32, further comprising:

computer code for transforming the inertial orientation signals to signals representative of the projected inertial orientation signals on each of three perpendicular axes.

34. A computer program product according to claim 32, further comprising:

computer code for calculating a pitch-angle error signal based on the pitch signal and the inertial orientation signal and feeding back the pitch-angle error signal to the computer code for receiving a pitch signal and an inertial orientation signal to adjust the inertial orientation signal.

35. A computer program product according to claim 32, wherein the computer code for receiving an inertial orientation signal receives three inertial orientation signals, one inertial orientation signal each from three inertial orientation sensors;

the computer program product further comprising;

computer code for calculating three rotation rate signals based on the three inertial orientation signals, wherein each rotation rate signal represents a rotation rate about one axis of three perpendicular axes.

36. A computer program product according to claim 35, further comprising:

computer code for integrating the rotation rate signals to produce orientation angle signals.

37. A computer program product according to claim 36, further comprising:

computer code for detecting erroneous inertial orientation signals and creating a fault signal in response to the detection of an erroneous inertial orientation signal.

38. A computer program product according to claim 37, further comprising:

computer code for switching to a single axis estimate of the pitch state from a three axis estimate of the pitch state if a fault signal is created.

39. A computer program product according to claim 35, further comprising:

computer code for calculating a bias signal based at least on the pitch signal and the orientation angle signals, the bias signal being output to the computer code for receiving signals.