Actuator Position Estimation for Electro-Hydraulic Ride Height Control System using EKF and a Reduced-Order Model Obtained via Singular Perturbation

Ride height control systems adjust the distance between a vehicle's chassis and the road surface to improve ride comfort, aerodynamics, and underbody protection. Among various types, electro-hydraulic systems use hydraulic actuators to lift or lower the vehicle body. In such systems, ride height is usually measured by sensors mounted on the vehicle body. However, these sensors do not directly measure the actuator's internal position. As a result, the controller may continue commanding motion even after the actuator reaches its stroke limit. This can lead to noise generation, mechanical wear, and reduced ride quality. To solve this problem, we propose a model-based method to estimate the internal position of a single-acting actuator using only measurable signals. First, a full-order model of the system is developed, including the motor, pump, valves, and actuator dynamics. Then, a reduced-order model is derived using singular perturbation to simplify the computation. An extended Kalman filter is designed based on this reduced model. Simulation results are validated against experimental data obtained from vehicle-level tests. The proposed method shows accurate and robust performance under various operating conditions and sensor noise, making it suitable for practical ride height control systems.