Nonfragile H_∞ Control of Delayed Active Suspension Systems in Finite Frequency Under Nonstationary Running

The vehicle active suspension has drawn considerable attention due to its superiority in improving the vehicle dynamic performance. This paper investigates the nonfragile H_∞ control of delayed vehicle active suspension in a finite frequency range under nonstationary running. The control objective is to improve ride quality in a finite frequency band and ensure suspension constraints, and a quarter car model of the active suspension is established for a controller design. Then, the input delay, actuator uncertainty, and external disturbances are considered in the controller design. Moreover, a further generalization of the strict S-procedure is utilized to derive a sufficient condition in terms of linear matrix inequality (LMI) to capture performance in the concerned frequency range. Furthermore, a multi-objective controller is designed based on projection lemma in the framework of the solution of LMIs. A nonstationary road profile is established, and numerical simulations are also conducted to show the effectiveness and robustness of the proposed controller. Finally, experimental tests on a quarter-car test rig are implemented to examine the performance of the proposed controller for real applications.