Optimal active suspension design using constrained optimization

In a quarter-car vehicle model, optimal control schemes for an active suspension are designed using a constrained optimization procedure. The control laws obtained minimize the H-2-norm of vehicle acceleration subject to constraints on r.m.s. values of the suspension stroke, tire deformation and actuator force. Constraints imposed on feedback coefficients define quasi-optimal control laws that show increased robustness to system parameter variations and disturbances. To impact body acceleration at frequencies near the unsprung mass mode, tire damping is introduced in the model. The optimal and quasi-optimal control schemes were partially verified on a quarter-car simulator with a random road input and the preliminary results are encouraging. The tests showed significant improvement (3-5 dB) of body acceleration response in the frequency range up to 25 Hz and increased robustness of the quasi-optimal control laws, that use lower amounts of spring cancellation. (C) 1997 Academic Press Limited.