Vehicle yaw/roll stability control with semi-active suspension
View Patent ↗A rollover avoidance system for changing the damping characteristics of suspension dampers at each wheel of a vehicle so as to mitigate the potential for vehicle rollover. The system includes a plurality of vehicle parameter sensors for measuring vehicle parameters and providing vehicle parameter signals. The system also includes a controller for generating a damper suspension command signal for each damper using the vehicle parameter signals. The controller considers a roll control factor representing a rollover condition of the vehicle and a yaw stability control factor representing a yaw condition of the vehicle to set the damping of the dampers to mitigate the potential for vehicle rollover.
1. A rollover avoidance system for changing the damping characteristics of suspension dampers at each wheel of a vehicle to mitigate a potential rollover condition, said system comprising:
a speed sensor providing a vehicle parameter speed signal of the speed of the vehicle;
a roll rate sensor providing a vehicle parameter roll rate signal of the roll rate of the vehicle;
a lateral acceleration sensor for providing a vehicle parameter lateral acceleration signal of a lateral acceleration of the vehicle;
a yaw rate sensor for providing a vehicle parameter yaw rate signal of the yaw rate of the vehicle;
a hand-wheel angle sensor for providing a vehicle parameter hand-wheel angle signal of the angle of a vehicle hand-wheel;
a rollover indicator processor for calculating a roll stability indicator signal;
a dynamic command processor for generating a desired stability command signal based on the vehicle parameter signals for a desired stiffness of the dampers; and
a closed-loop controller responsive to vehicle parameter signals, the calculated roll stability indicator signal and the desired stability command signal, said closed-loop controller calculating an understeer or oversteer signal based on whether the vehicle is in an understeer or oversteer condition and a yaw stability control factor based on a yaw rate error signal and a side-slip error signal, said closed-loop controller further determining a roll error signal as the difference between the desired stability command signal and the calculated rollover stability indicator signal, said closed-loop controller also calculating a gain signal as a function of the vehicle speed signal, said closed-loop controller further calculating a closed-loop roll control factor based on the gain signal and the roll error signal, said closed-loop controller also determining a front to rear damper distribution of the damping characteristics of the suspension dampers based on the yaw rate error signal and the understeer or oversteer signal, said closed-loop controller generating a damper suspension command signal for each damper based on the front to rear distribution signal and the closed-loop roll control factor or the yaw stability control factor.
2. The system according to claim 1 wherein the closed-loop controller uses the yaw stability control factor or the roll control factor to generate the damper command signals depending on which is larger.
3. The system according to claim 1 wherein the closed-loop controller uses predetermined different gain signal depending on the magnitude of the roll stability indicator signal.
4. The system according to claim 1 further comprising an open-loop controller, said open-loop controller calculating an open-loop roll control factor based on the lateral acceleration signal, said system further comprising an adder that adds the open-loop roll control factor and the closed-loop roll control factor to generate a total roll control factor to determine the suspension command signals for each damper.
5. The system according to claim 4 wherein the closed-loop controller determines the suspension command signals as:
K LF =0.5 K T FR
K RF =K LF
K LR =0.5 K T (1− FR )
K RR =K LR
where K LF is the damping command signal for the damper at the left front wheel, K RF is the damping command signal for the damper at the right front wheel, K LR is the damping command signal for the damper at the left rear wheel, K RR is the damping command signal for the damper at the right rear wheel, K T is the added open-loop and closed-loop roll control factor or the yaw stability control factor, and FR is the front to rear damper distribution.
6. The system according to claim 1 wherein the dampers are semi-active magneto-rheological dampers.
7. The system according to claim 1 wherein the closed-loop controller determines the front to rear damper distribution of the damping characteristics of the suspension dampers using look-up tables.