Generalized PI Control of Active Vehicle Suspension Systems with MATLAB

Abstract

The main objective on the active vibration control problem of vehicles suspension systems is to get security and comfort for the passengers by reducing to zero the vertical acceleration of the body of the vehicle. An actuator incorporated to the suspension system applies the control forces to the vehicle body of the automobile for reducing its vertical acceleration in active or semi-active way. The topic of active vehicle suspension control system has been quite challenging over the years. Some research works in this area propose control strategies like LQR in combination with nonlinear backstepping control techniques (Liu et al., 2006) which require information of the state vector (vertical positions and speeds of the tire and car body). A reduced order controller is proposed in (Yousefi et al., 2006) to decrease the implementation costs without sacrificing the security and the comfort by using accelerometers for measurements of the vertical movement of the tire and car body. In (Tahboub, 2005), a controller of variable gain that considers the nonlinear dynamics of the suspension system is proposed. It requires measurements of the vertical position of the car body and the tire, and the estimation of other states and of the profile of the ride. This chapter proposes a control design approach for active vehicle suspension systems using electromagnetic or hydraulic actuators based on the Generalized Proportional Integral (GPI) control design methodology, sliding modes and differential flatness, which only requires vertical displacement measurements of the vehicle body and the tire. The profile of the ride is considered as an unknown disturbance that cannot be measured. The main idea is the use of integral reconstruction of the non-measurable state variables instead of state observers. This approach is quite robust against parameter uncertainties and exogenous perturbations. Simulation results obtained from Matlab are included to show the dynamic performance and robustness of the proposed active control schemes for vehicles suspension systems. GPI control for the regulation and trajectory tracking tasks on time invariant linear systems was introduced by Fliess and co-workers in (Fliess et al., 2002). The main objective is to avoid the explicit use of state observers. The integral reconstruction of the state variables is carried out by means of elementary algebraic manipulations of the system model along with suitable