l1 state feedback control of active suspension

A controller is designed for automotive active suspension whose purpose is to improve the ride comfort against road disturbances. This disturbance rejection problem is formulated as an l₁ control problem, i.e., minimization of the effects of disturbances in terms of the l_∞-induced norm. Since l₁ control theory minimizes the maximum possible amplification of signal magnitude, the l ₁ controller can specify the maximum magnitude of outputs in the time domain, regardless of the frequency of road disturbances. To design a static full state feedback controller, Shamma´s l₁ near-optimal control theory is applied. Although l₁ control with full state feedback usually can be dynamic and of arbitrarily high order, this theory with a certain approximation is able to construct a simple static state feedback with nonlinearity. Therefore, for a linear quarter vehicle model, a nonlinear controller is designed. Finally, satisfactory performances of the controller are confirmed by numerical analysis