Design of Active Suspension System for Quarter-Car Model using Linear Quadratic Regulator (LQR)

This paper presents designing of an optimal state feedback controller, Linear Quadratic Regulator (LQR), for a quarter-car suspension system. The suspension system dictates the dynamic behaviour of the vehicle arising from the road interactions and body forces. The performance of a suspension system is indicated by the occupant's comfort, suspension deflection, and vehicle handling on the road. Conventional passive suspensions system compromise comfort and road handling. Thus, using external force actuation, active suspensions are proven to be superior in retaining suspension performance for a wider range of operating conditions. Control strategy determines the performance of active suspensions. In this study, an LQR controller is designed that minimizes the suspension deflections with the application of optimal control effort. The system response can be tuned by varying the values of weighting factors. A method to determine these weights is demonstrated to yield feasible results while reducing the number of trials required. A simulation study of the system response to different weighting factors is conducted and changes in the suspension characteristics are illustrated graphically. The simulation results demonstrate that a finely tuned LQR controller retains excellent comfort and handling characteristics compared to the passive counterpart.