Abstract: A method and apparatus for determining likelihood of rollover of a vehicle and/or mitigating rollover of the vehicle is responsive to measured vehicle lateral acceleration and a measured one of vehicle roll rate and vehicle suspension displacements to derive estimates of roll angle and roll rate. First, preliminary, estimates of roll angle and roll rate are derived and used as pseudo-measurements in a dynamic, closed loop observer equation which represents a model of the vehicle in a first roll mode for roll angles small compared to a reference value indicating two wheel lift-off and a second roll mode for roll angles at least near a reference value indicating two wheel lift-off. The observer equation has parameters and gains with values for each mode stored as a function of roll angle index derived from measurements and pseudo-measured values. The observer equation produces second, improved values or roll angle and roll rate together indicating the likelihood of vehicle rollover.

Abstract: A method and apparatus for determining likelihood of rollover of a vehicle and/or mitigating rollover of the vehicle is responsive to measured vehicle lateral acceleration and a measured one of vehicle roll rate and vehicle suspension displacements to derive estimates of roll angle and roll rate. First, preliminary, estimates of roll angle and roll rate are derived and used as pseudo-measurements in a dynamic, closed loop observer equation which represents a model of the vehicle in a first roll mode for roll angles small compared to a reference value indicating two wheel lift-off and a second roll mode for roll angles at least near a reference value indicating two wheel lift-off. The observer equation has parameters and gains with values for each mode stored as a function of roll angle index derived from measurements and pseudo-measured values. The observer equation produces second, improved values or roll angle and roll rate together indicating the likelihood of vehicle rollover.

Abstract: A vehicle chassis control stores first and second calibrated values of a predetermined braking parameter and a steering correction parameter. The control includes apparatus for detecting a split coefficient condition with respect to the road surface; and, when it does and a braking signal is present, the control actuates braking apparatus for a wheel on the side of the vehicle having the higher coefficient of friction with the first calibrated value of the predetermined braking parameter and simultaneously actuates the steering apparatus with a steering correction to compensate for yaw induced by braking on the split coefficient road surface. If the steering correction is not available, however, the braking apparatus is actuated for the wheel having the higher coefficient of friction with the second calibrated value of the predetermined braking parameter without simultaneously actuating the steering apparatus with the steering correction.

Abstract: A brake system control method, comprising the steps of: measuring a set of vehicle parameters including steering wheel angle, vehicle speed, lateral acceleration and vehicle yaw rate; responsive to the measured parameters using an observer to estimate lateral velocity of the vehicle, wherein the observer contains (a) an open loop dynamic model of the vehicle responsive to the measured vehicle speed and the measured yaw rate, (b) a closed loop term responsive to a first error between the measured yaw rate and a predicted yaw rate, a second error between a previously estimated lateral velocity and a predicted lateral velocity and a third error between the measured lateral acceleration and a predicted lateral acceleration; estimating a vehicle slip angle responsive to the estimate of lateral velocity; determining a control command responsive to the vehicle slip angle; and controlling an actuator responsive to the control command.

Abstract: The present invention provides a method of estimating a coefficient of adhesion between a road surface and a plurality of tires disposed on a vehicle. An estimated coefficient of adhesion for each of the plurality of tires is provided. First values of longitudinal and lateral forces on the tires are determined from a first set of vehicle dynamic parameters requiring no explicit knowledge of the coefficient of adhesion; and second values of the same forces are determined from a second set of vehicle parameters in an analytic tire model including the estimated value of the coefficient of adhesion. Differences between the first and the second values of the forces on the tires are determined in the longitudinal and lateral directions. Longitudinal and lateral adaptation speeds are determined for each of the plurality of tires; and a coefficient of adhesion adjustment for each of the plurality of tires is estimated from the differences and the adaptation speeds.

Abstract: A method and apparatus for determining likelihood of rollover of a vehicle and/or mitigating rollover of the vehicle is responsive to measured vehicle lateral acceleration and a measured one of vehicle roll rate and vehicle suspension displacements to derive estimates of roll angle and roll rate. First, preliminary, estimates of roll angle and roll rate are derived and used as pseudo-measurements in a dynamic, closed loop observer equation which represents a model of the vehicle in a first roll mode for roll angles small compared to a reference value indicating two wheel lift-off and a second roll mode for roll angles at least near a reference value indicating two wheel lift-off. The observer equation has parameters and gains with values for each mode stored as a function of roll angle index derived from measurements and pseudo-measured values. The observer equation produces second, improved values or roll angle and roll rate together indicating the likelihood of vehicle rollover.

Abstract: Controllable dampers are used to improve vehicle responses and stability during severe vehicle handling maneuvers. A total handling damping value for the vehicle is derived, preferably from the greatest of a yaw rate error value, a lateral acceleration value and a time derivative of lateral acceleration value. In addition, a control ratio of front axle roll damping to total roll damping is derived, preferably from the yaw rate error value, an oversteer/understeer indication and possibly vehicle speed. From these values, handling damping values are derived for each wheel of the vehicle and blended with damping values for the same wheels derived from suspension component movement to determine a corner damping command for each controllable damper. Preferably, the damping values derived from suspension component movement are shifted away from damping control of the vehicle body toward handling damping control when yaw rate error is large in magnitude.

Abstract: A vehicle chassis control stores first and second calibrated values of a predetermined braking parameter and a steering correction parameter. The control includes apparatus for detecting a split coefficient condition with respect to the road surface; and, when it does and a braking signal is present, the control actuates braking apparatus for a wheel on the side of the vehicle having the higher coefficient of friction with the first calibrated value of the predetermined braking parameter and simultaneously actuates the steering apparatus with a steering correction to compensate for yaw induced by braking on the split coefficient road surface. If the steering correction is not available, however, the braking apparatus is actuated for the wheel having the higher coefficient of friction with the second calibrated value of the predetermined braking parameter without simultaneously actuating the steering apparatus with the steering correction.

Abstract: Controllable dampers are used to improve vehicle responses and stability during severe vehicle handling maneuvers. A total handling damping value for the vehicle is derived, preferably from the greatest of a yaw rate error value, a lateral acceleration value and a time derivative of lateral acceleration value. In addition, a control ratio of front axle roll damping to total roll damping is derived, preferably from the yaw rate error value, an oversteer/understeer indication and possibly vehicle speed. From these values, handling damping values are derived for each wheel of the vehicle and blended with damping values for the same wheels derived from suspension component movement to determine a corner damping command for each controllable damper. Preferably, the damping values derived from suspension component movement are shifted away from damping control of the vehicle body toward handling damping control when yaw rate error is large in magnitude.

Abstract: An improved active brake control method which compensates for the effects of a banked road surface under both steady state and transient operating conditions of the vehicle. The control includes an observer for estimating the lateral velocity of the vehicle as a means of determining vehicle slip angle, and a time derivative of the estimated lateral velocity is used along with measured values of lateral acceleration, vehicle speed and yaw rate to compute the lateral acceleration component due to the banked road surface, referred to as the bank acceleration. The bank acceleration, in turn, is then used to correct the values of measured steering angle and the measured lateral acceleration used (1) to develop the desired yaw rate, slip angle and lateral acceleration, and (2) to estimate the surface coefficient of adhesion and slip angle. Partial compensation can be achieved by applying suitable gain factors to the computed bank acceleration, if desired.

Abstract: An improved vehicle active brake control based on an estimate of vehicle yaw rate and slip angle, wherein the estimate is based on a weighted average of two yaw rate values developed with two different estimation techniques. In general, the first estimate of yaw rate is based on the relative velocity of the un-driven wheels, and the second estimate is based on a measure of lateral acceleration. Confidence levels in each estimate are determined and used to form a third or preliminary yaw rate estimate based on a weighted average of the first and second estimates, and the third estimate is supplied to a closed-loop nonlinear dynamic observer which develops the final estimate of yaw rate, along with estimates of lateral velocity and side-slip angle.

Abstract: A brake system control method, comprising the steps of: determining a maximum acceleration of a vehicle on a high coefficient of adhesion road surface; measuring an acceleration of the vehicle; determining a ratio between the measured acceleration of the vehicle and the maximum acceleration of the vehicle on the high coefficient of adhesion road surface; responsive to the ratio, determining a signal indicative of present coefficient of adhesion; determining a brake actuator command responsive to the signal; and providing the brake actuator command to a brake actuator, wherein an accurate estimation of coefficient of friction between the vehicle wheels and the road surface is used in the brake system control.

Abstract: A brake system control for use in a vehicle with wheels, wheel brakes and a body, comprising the steps of: measuring a plurality of vehicle parameters; responsive to the measured parameters, determining at least a vehicle yaw rate, a vehicle slip angle, a desired yaw rate and a desired slip angle; responsive to the measured parameters, estimating a coefficient of adhesion between the vehicle wheels and a road surface; implementing a control responsive to the vehicle yaw rate and the desired yaw rate with a first authority and responsive to the vehicle slip angle and the desired slip angle with a second authority, wherein the first authority increases as the estimated coefficient of adhesion increases and decreases as the estimated coefficient of adhesion decreases; and controlling the wheel brakes responsive to the control to reduce a first difference between the vehicle yaw rate and the desired yaw rate and to reduce a second difference between the vehicle slip angle and the desired slip angle.

Abstract: An active brake control method including an improved method of developing the desired state variables, enabling the system designer to specify the damping ratio and the un-damped natural frequency of desired vehicle performance. The desired state variables are determined by converting a linear time domain model into a transfer function model and solving for the lateral velocity and yaw rate as a function of the driver steering angle, the damping ratio, the un-damped natural frequency of the vehicle, and the transfer function zeros. The damping ratio, the un-damped natural frequency of the vehicle, and the transfer function zeros may either be computed or specified in a look-up table as a function of vehicle speed. This allows the system designer to provide increased damping at high vehicle speeds, for example.