Model identification of an automotive hydraulic active suspension system

The advantages of an automotive active suspension system have been promised for many years. A fully active suspension based on hydraulic actuators seemed to be a good candidate for fulfilling such expectations. However the high frequency characteristics of such systems have been proved to be problematic for practical implementations. A high fidelity mathematical model capturing realistic dynamic behaviors of the hydraulic active suspension is required for the development of such systems. In this paper, a quarter vehicle model of an hydraulic active suspension system suitable for developing wheel control is developed. The model accounts for the necessary component dynamics contributing to the higher frequency characteristics of the system. They include suspension bushing, actuator friction, hydraulic servo valve and actuator, as well as tire model. Identification of the model parameters with respect to a test vehicle driven through a standard impact bump is presented. The model results and the test data are virtually identical. The model has been shown to be a very effective tool for active suspension wheel mode control design and analysis