On the Preview Control of Limited Bandwidth Vehicle Suspensions

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On the Preview Control of Limited Bandwidth Vehicle Suspensions

Pilbeam, C / Sharp, R S

Using methods established in earlier work, calculations are carried out to determine the performance possibilities of a slow-active automobile suspension. The suspension consists of a limited bandwidth actuator in series with a passive spring, the combination being in parallel with a passive damper. Use of the correlation between the front and rear wheel inputs is made to determine near-optimal state feedback laws which improve on the uncorrelated (non-preview) laws found using standard linear quadratic regulator (LQR) theory. Various control laws are calculated for different vehicle speeds and the effects of placing the emphasis on either ride comfort or vehicle handling in the control law are studied. It is found that there is significant advantage to be gained in making use of the preview information available when the emphasis is placed on ride comfort in the cost function. Increasing the amount of preview (by reducing the vehicle speed) increases the amount of improvement made available by the use of preview information down to a speed of 10 m/s, below which there is nothing to be gained from having more preview. Due to the practical advantages associated with the use of limited bandwidth active control in comparison with full bandwidth systems and the small additional costs implied by adding to the signal processing required as specified, the results are considered important to the future development of active vehicle suspensions.