Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication
Reexamination Certificate
1999-12-09
2001-12-18
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
C701S033000, C701S038000, C701S060000, C701S063000, C180S007100, C037S348000, C172S009000
Reexamination Certificate
active
06332103
ABSTRACT:
TECHNICAL FIELD
The present invention pertains to a device and methods for estimating the pitch state of a personal vehicle for purposes of control of the vehicle.
BACKGROUND
Various methods and devices exist for measuring pitch of a vehicle. Pitch is defined as the angle, denoted as &THgr;, between a specified vehicle-fixed substantially vertical axis, denoted as R and the true vertical axis as defined by gravity. R may be defined, for example, by a seat back or other vehicle-fixed structure. The term pitch is synonymous with inclination within the following disclosure and appended claims. Pitch sensing devices include accelerometers, inclinometers, pendulous reference sensors, also known as tilt sensors, and distance probes.
Single axis state estimators (SASEs), can provide an estimate of the pitch of a vehicle over regular surfaces under most expected conditions. The pitch state becomes inaccurate where the vehicle makes certain changes in direction, such as, turning the vehicle around on a sloped surface. In such a situation, a SASE may indicate that the vehicle still has a positive pitch even though the vehicle is facing downward where the inclinometer should indicate a negative pitch. The sensors saturate if the pitch suddenly changes so that the pitch rate is above the temporal threshold at which the device may measure change.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the invention, 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.
In another embodiment, 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. In other embodiments the at least one inertial reference sensor is a gyroscope.
The pitch state estimator may further include a virtual gyro construction module for receiving the inertial orientation signals of the gyroscopes and outputting to the state estimator module three rotation rate signals. Each rotation rate signal represents a rotation rate about one axis of three perpendicular axes having an origin at the center of gravity of the vehicle.
The state estimator module may further include a rotation correction module which transforms the three rotation rate signals producing three corrected rotation rates so that the three rotation rate signals correspond to the coordinate system of the pitch signal. The state estimator module also may include an integrator module for producing orientation angles based on the three corrected rotation rate signals and a summer which receives the inertial orientation signals. The state estimator module further includes a gyro-bias integrator which calculates a bias signal based at least on the pitch signal and the orientation angles, the bias signal being output to the summer. In this embodiment, the output signal of the summer is fed back into the rotation correction module.
In another related embodiment, a fault detection module is included for detecting erroneous inertial orientation signals produced by an inertial reference sensor. Once an erroneous inertial orientation signal is detected, the fault detection module determines that a gyroscope has failed.
In another embodiment, the state estimator module performs a single axis estimate of the pitch state if a gyroscope has failed.
A pitch state signal may be generated in one embodiment by first measuring an estimated pitch of the vehicle with respect to gravity using an inclination sensor. The estimated pitch measurement is converted into a digital estimated pitch signal and then the inertial orientation rates of the vehicle are measured using at least three inertial sensors positioned in three or more distinct orientations on the vehicle. The inertial orientation rate measurements of the three or more inertial orientation sensors are converted into three or more digital inertial orientation signals. Finally, a pitch state signal is calculated in a state estimator module based in part on the digital inertial orientation signals and the digital pitch signal.
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Amsbury Burl
Steenson, Jr. James Henry
Arthur Gertrude
Bromberg & Sunstein LLP
Cuchlinski Jr. William A.
DEKA Products Limited Partnership
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