Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1999-08-16
2001-08-28
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S048000, C701S072000, C303S140000, C303S146000
Reexamination Certificate
active
06282479
ABSTRACT:
TECHNICAL FIELD
This invention pertains to microprocessor-based brake control systems for vehicles. More specifically, it relates to a method of estimating the yaw rate of a vehicle having a relatively high center of gravity and significant body roll during turning maneuvers.
BACKGROUND OF THE INVENTION
Automotive vehicles have been produced with computer-controlled brake systems that modulate brake force during stops to provide anti-lock brake (ABS) control and/or that modulate brake force during vehicle acceleration to provide positive acceleration traction control (TCS). Recently, more comprehensive computer-based vehicle control systems have been developed that provide additional chassis control under braking or positive acceleration conditions. Such systems are described, e.g., in U.S. Pat. Nos. 5,720,533 and 5,746,486, both entitled “Brake Control System” and assigned to the assignee of this invention. These systems seek to control, among other parameters, the yaw rate of the vehicle.
The computer in the chassis control systems described in these patents uses signals from a variety of sensors such as wheel speed sensors, steering wheel angle sensors, brake switch sensor, master brake cylinder pressure sensor, yaw rate sensor, lateral accelerometer and the like. For further development of such control systems, it is desirable and/or necessary to provide algorithms or computer-controlled processes for eliminating some of such sensors or for detecting faults in their operation.
For example, a process has been developed that permits vehicle control based on an estimated yaw rate rather than the output of a yaw rate sensor or lateral accelerometer. This practice is described in U.S. Ser. No. 09/080,372, filed May 18, 1998, titled “Vehicle Yaw Control Based on Yaw Rate Estimate” and assigned to the assignee of this invention.
The vehicle yaw rate can be computed as a function of the measured speeds of the non-driven wheels of the vehicle and the distance between the center of the wheel treads (i.e., the track). However, the estimate may fail to equal the actual vehicle yaw in a vehicle with a relatively high center of gravity due to the relatively high body roll of the vehicle. When a vehicle with large body roll and high center of gravity is driven under high lateral acceleration, the outside tire is compressed and the radius of the inside tire is increased. Therefore, the estimated yaw rate is higher than the actual yaw rate of the vehicle. It is desired to compensate for the yaw rate estimation, without a yaw sensor or lateral acceleration sensor, and control vehicle yaw rate even during conditions that have previously degraded the yaw rate estimation such as in vehicles with large body roll and high center of gravity.
SUMMARY OF THE INVENTION
This invention is typically applicable for estimating the yaw rate in automotive vehicles incorporating a computer-based antilock brake system (ABS), a traction control system (TCS), or the like, in combination with vehicle yaw control. It is applicable in such systems in which at least two of the vehicle wheels, i.e., the front wheels or the rear wheels, are not driven. In vehicle control systems of this type, the microprocessor-based controller receives data from wheel speed sensors, a brake actuator sensor and a steering angle sensor, among other possible data sources, in the course of its control of brake actuators for each wheel. A yaw rate sensor and/or a lateral acceleration sensor may also be employed. However, as stated above, methods have been developed that permit vehicle yaw control based on an estimated yaw rate rather than the output of an accelerometer.
A good estimation of yaw rate can be obtained by determining the difference in the sensed velocities of the non-driven wheels and dividing that difference by the known track of the wheels. The subject invention provides an improvement to such an estimation that is particularly useful in vehicles that have a relatively high center of gravity and experience a significant vehicle roll during yaw.
In accordance with the invention, a table of correction factors, also called gain factors, is determined for the vehicle. These gain factors are correlated with vehicle speed. The gain factors are a function of the sprung mass of the vehicle, the height of the vehicle center of gravity, the height of the roll center of the wheels, the track of the vehicle wheels and the radii of the wheels. There is also a dependence on tire stiffness. Preferably, the gain factor data is determined experimentally on a prototype to correlate vehicle velocities with actual yaw rates. Such data may, for example, be stored for reference in a look-up table in the permanent memory of the microprocessor-based controller. Thus, an instantaneous initial value for yaw rate, based solely on wheel speed and track, may be modified by use of a referenced, velocity-based gain factor in a manner described fully in the description of a preferred embodiment.
An advantage of the invention is that yaw rates for trucks and other relatively high center-of-gravity vehicles may be more accurately estimated for use in automotive computer-based brake and traction control systems. Other objects and advantages of this invention will become apparent from a detailed description of a specific embodiment.
REFERENCES:
patent: 5720533 (1998-02-01), Pastor et al.
patent: 5746486 (1998-05-01), Paul et al.
Ghoneim Youssef Ahmed
Sidlosky David Michael
Cuchlinski Jr. William A.
Donnelly Arthur D.
General Motors Corporation
Grove George A.
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