Control of Quadratic Active Suspended System Using LQR and Sliding Mode Control and Comparison at Different Conditions

Abstract

Vehicle suspension system is considered one of the systems most exposed to unknown disturbances. Therefore, it requires the design of a control system capable of reducing the disturbances impact. Hence, we used the Linear Quadratic Regulator (LQR) as an optimal control algorithm and sliding mode control as a robust control algorithm to find the best algorithm. The simulation was carried out using MATLAB after  representing the system in the state space and then integrated each controller with it.

     We then compared the performance of the controllers under different disturbances by comparing the chair displacement, settling time, the amount of oscillation in the control signal, and its maximum value. The comparison showed the superiority of sliding control in terms of robustness against disturbances, while it exhibited significant oscillation in the control signal, whereas the linear quadratic regulator with a weighted performance matrix showed good performance with smoothness in the control signal.

     It was eventually concluded that the sliding control is necessary in heavy disturbances systems, while it is preferable to use and experiment with other reaching modes to reduce  the oscillations.