Comparison of linear and nonlinear feedback control for a half-car model with MR dampers

The paper deals with linear and nonlinear feedback control for a half-car model including Spencer model of the magnetorheological damper. The vehicle model was subjected to sinusoidal road excitation corresponding to a rough road of class F and selected according to the ISO 8608. All control schemes were assessed using a quality index closely related to the ride comfort and evaluated based on an averaged vehicle body acceleration. For the linear state-feedback control, the LQ problem was solved for different variants of weights in a cost function dedicated to mitigation of vehicle body velocities or accelerations. Resultant control gains were obtained by selecting the best case for each variant. Furthermore, control quality was enhanced by analysing the neighbourhood of each solution within the space of control gains. Also, nonlinear separate suspension control schemes based on squared and cubic front and rear vehicle body velocities or accelerations were validated. Simulation results of the presented algorithms were compared with those obtained for the well-known separate Skyhook and ADD (acceleration-driven damping). It was shown that the LQ-based state-feedback control offers better control quality in comparison to the classical Skyhook and ADD, but the additional tuning of resultant control gains is recommended. Besides, it was stated that the acceleration-based LQ gives better performance comparing to velocity-based LQ. It was also stated that nonlinear algorithms exhibit similar performance as classical Skyhook, but in this case, better results were obtained for velocity-based control.