Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
1998-11-19
2001-09-18
Grimley, Arthur T. (Department: 2852)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
C701S036000, C701S035000, C701S038000, C701S045000, C701S110000, C340S440000
Reexamination Certificate
active
06292759
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to vehicle attitude angle sensing, and more particularly, to low-cost roll and pitch angle estimation for a vehicle.
Future generation automotive vehicles may increasingly employ safety-related devices that deploy in the event that the vehicle rolls over to provide added protection to the occupants of the vehicle. For example, upon detecting a vehicle rollover condition, a pop-up roll bar can be deployed such that, when activated, the roll bar further extends vertically outward to increase the height of support provided by the roll bar. Other controllable features may include actuating deployment of one or more air bags, such as front or side deployment air bags, or actuating a pretensioner to pretension a restraining device, such as a seat belt or safety harness, to prevent occupants of the vehicle from ejecting from the vehicle or colliding with the roof of the vehicle.
In the past, basic rollover sensors have been employed in automotive vehicles to measure the angular position of the vehicle from which a rollover condition can be determined. The basic rollover sensors have included the use of a pendulum normally hanging vertically downward due to the earth's gravitational force. Many basic automotive sensing devices are employed simply to monitor the angular position of the vehicle relative to a level ground horizontal position. As a consequence, the basic automotive vehicle rollover sensors have generally been susceptible to error when the vehicle travels around a turn or becomes airborne, in which case the earth's gravitational force, which the sensor relies on, may be overcome by other forces.
More recently, sophisticated rollover sensing approaches have been considered. One such approach considered requires the use of six sensors including three accelerometers and three angular rate sensors, also referred to as gyros, all of which are employed together for use in an inertial navigation system which tracks position and attitude of the vehicle. The three accelerometers generally provide lateral, longitudinal, and vertical acceleration measurements of the vehicle, while the three gyros measure pitch rate, roll rate, and yaw rate. In sensing a rollover condition, the system determines a vehicle roll angle. However, the more sophisticated conventional rollover sensing approaches generally require a large number of high-precision and expensive sensors. In addition, known sophisticated systems are susceptible to cumulative drift errors, and therefore must be reset occasionally.
It should be appreciated that various other applications may require knowledge of the roll and pitch attitude angles of a vehicle as the vehicle maneuvers on the ground. In addition to rollover detection, attitude angle estimators may be employed to provide a roll and pitch angle indications to the driver or other occupants of the vehicle. In the past, attitude angle estimators have employed one or more accelerometers and an angular rate sensor for each axis of rotation of the vehicle. However, there exists the problem of how to combine angle-related information contained in the accelerometer and angular rate sensor in order to obtain an overall attitude angle measurement. This is because each type of sensor generally has characteristic failings in the conventional applications. For example, the accelerometer-based attitude angle estimate is generally relatively noisy when the vehicle is traveling on a rough road surface, and may sustain large errors whenever the vehicle's trajectory involves an inertial acceleration having a component perpendicular to the rotational axis under consideration. In addition, the angular rate sensor estimate, which is typically obtained by integrating the angular rate sensor's output signal, generally has a tendency to drift with an ever-increasing error due to unknown bias or offset in the sensed angular rate signal.
It is, therefore, one object of the present invention to provide for an attitude angle estimator that provides an estimation of the attitude angle of a vehicle and minimizes errors that may be present in automotive-grade sensors. It is another object of the present invention to provide for an attitude angle estimator that combines vehicle sensed signals to obtain an overall more accurate attitude angle estimation. It is a further object of the present invention to provide for a vehicle roll angle estimator and/or vehicle pitch angle estimator that minimizes the effects of noise present in an accelerometer based angle estimate, and minimizes error present in an angular rate sensed signal.
SUMMARY OF THE INVENTION
In accordance with the teachings of the present invention, an attitude angle estimator and method of estimating attitude angle of a vehicle are provided for estimating the roll and/or pitch angle. The attitude angle estimator employs an angular attitude rate sensor for sensing angular attitude rate of a vehicle and producing an output signal, and an accelerometer for detecting lateral or longitudinal acceleration of the vehicle and producing an output signal. A controller determines an acceleration-based attitude angle as a function of the sensed acceleration. The controller determines an attitude angle estimate and updates the attitude angle estimate as a function of the angular attitude rate. The controller further provides a blending coefficient and further updates the attitude angle estimate so as to generate a current vehicle attitude angle estimate as a function of the acceleration-based attitude angle and the blending coefficient, and produces a vehicle angle estimate signal, such as a roll angle estimate and/or a pitch angle estimate.
The method for estimating an attitude angle of a vehicle according to the present invention includes sensing angular attitude rate of a vehicle and producing an output signal, and sensing a lateral or longitudinal acceleration of the vehicle and producing an output signal. The method also includes determining an acceleration-based attitude angle as a function of the sensed acceleration. An attitude angle estimate is provided and is updated as a function of the angular attitude rate. A blending coefficient is also provided. The method further updates the attitude angle estimate to generate a current vehicle attitude angle estimate as a function of the acceleration-based attitude angle and the blending coefficient. The vehicle attitude angle estimate may include a roll angle estimate and/or a pitch angle estimate.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.
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Delphi Technologies Inc.
Funke Jimmy L.
Grimley Arthur T.
Le John
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