Takagi-Sugeno fuzzy control scheme for electrohydraulic active suspensions

The paper presents a new control strategy for active vehicle suspensions using electrohydraulic actuators based on Takagi-Sugeno (T-S) fuzzy modelling technique. As the electrohydraulic actuator dynamics is highly nonlinear, the T-S fuzzy modelling technique using the idea of "sector nonlinearity" is applied to exactly represent the nonlinear dynamics of electrohydraulic actuator in a denned region at first. Then, by means of parallel distributed compensation (PDC) scheme and Lyapunov method, a fuzzy HOO controller is designed for the T-S fuzzy model to optimise the suspension ride comfort performance, considering actuator input voltage saturation problem. The sufficient conditions for the existence of such a controller are derived in terms of linear matrix inequalities (LMIs). The advantage of this new control strategy for electro-hydraulic active suspensions is that it directly aims at optimising suspension performance with guaranteeing the closed-loop system stability. Thus, two-loop control strategy, where the inner loop is used to make the electrohydraulic actuator tracking a desired force (pressure, or displacement, etc.), is not necessary. In addition, the controller is simple in structure compared to the adaptive control algorithms. A numerical example is used to validate the effectiveness of the proposed approach. It is confirmed by the simulations that the designed controller can achieve better performance than the active suspension with optimal skyhook damper