This paper deals with feedback control of a hydraulic unit for direct yaw moment control, which actively maintains the dynamic stability of an automobile. The uncertain parameters and complex structure naturally call for empirical modeling of the hydraulic unit, which lead to a high-fidelity input/output model. The identified model is cross-validated against experimental data under various conditions, which helps to establish a stringent model uncertainty. Then, the H/sub /spl infin// optimization technique is employed to synthesize a controller with guaranteed robust stability and performance against the model uncertainty. The superb performance of the synthesized controller is experimentally verified, which shows the viability of the proposed approach in a real-world vehicle safety application.