Abstract
In this paper, a nonlinear tracking control strategy with extended state observer (ESO) is presented for vehicle active suspensions to improve the ride comfort, where suspension spaces, dynamic tire loads are considered as time-domain constraints to be guaranteed. The unique characteristic of the proposed approach lies in the independence on accurate mathematical model. More exactly, the unknown dynamics and external disturbances of the vehicle suspension are regarded as an augmented state of the system and are estimated using the designed ESO. The stability analysis shows that both the estimation error and the tracking error of the control output are bounded and that the upper bounds of the errors monotonously decrease with the increase of the observer bandwidth. Finally, a competitive experiment on a quarter-car suspension prototype is given to demonstrate the effectiveness of the proposed control schemes. (C) 2014 Elsevier Ltd. All rights reserved.