Performance enhancement of limited bandwidth active automotive suspensions by road preview

Investigations are made in order to predict the performance capabilities of preview controlled active vehicle suspensions using limited-bandwidth actuators. Mathematical tools for the implementation of preview control in discrete time, which were established in earlier work, are refined. This allows the use of multiple preview-inputs and reduces the system-order of a discrete-time preview system significantly with respect to former methods, while describing the dynamic system in an exact form and yielding an equivalent control law. This method is applied to a limited-bandwidth quarter-car system, which incorporates an actuator in series with a passive spring, the combination being in parallel with a passive damper. The control design is carried out using discrete-time linear quadratic regulator (LQR) theory. The optimal preview control law working in a physical sense, is worked out regarding the feedforward gain matrix. The performance indices and their component parts are considered when varying the actuator-bandwidth and preview time.