Vehicle rollover crashes, particularly with the increasing popularity of sport
utility vehicles (SUVs), continue to be a serious safety and liability problem for auto manufacturers. Various rollover and yaw control strategies have
been attempted including, active steering control, differential braking
control, and integrated control (using both of the previous strategies) but
have only provided limited success in addressing this problem. For
instance active steering systems, which have been only implemented in
high end luxury cars, are based on the application of a DC motor and a
sophisticated linear control method for adjusting the driver steering input to improve vehicle stability. However the control strategy fails to account for the nonlinearity of real-world driving conditions and thus isn’t robust
enough to handle all speeds, road conditions, and mass variations.
Simulations performed by the University of Waterloo using a complex
nonlinear 4 DOF vehicle yaw/roll model, as well as a complex nonlinear tire
model, show that all three conventional control strategies have limited
abilities to prevent rollover maneuvers.
Description and application of the invention
To address the aforesaid nonlinearity challenge, the University of Waterloo
developed a pulsed active steering control strategy which shows better
simulation results than the conventional control strategies and is able to
prevent rollover manoeuvres for all designated test tracks under all vehicle
models considered. The University’s invention uses a pulse generator to
generate special steering pulsation by measuring the rollover coefficient
and the actual vehicle yaw rate and comparing the measurement with the
rollover threshold number and expected yaw rate based on the steering
wheel angle. In general, the amplitude, frequency, and duty cycle of the
pulses affect the level of stability improvement. The most important factor
is the duty cycle of pulses which can be controlled easily and modulated to the driver steering input.
The new pulsed active steering controller has proven its efficiency for
vehicle stability control under nonlinear vehicle model in many simulations.
It has also been shown that the method is easy to implement with a much
lower cost compared to current techniques and can achieve vehicle
stability control under any vehicle condition. This new method can provide
affordable active stability control for all cars.