Robust PI Controller Design for Commercial Vehicles' Electro-Hydraulic Power Steering System

A robust PI controller design has been created and used in electro-hydraulic power steering (EHPS) systems for commercial vehicles. The PI controller was tuned based on the standard characteristics of the second-order system by adjusting two parameters, the damped ratio and the un-damped natural frequency, resulting in proportional and integral gains in four cases. The robustness problem in the system can be investigated for load disturbance rejection, set-point regulation, sensitivity and complementary function, and system performance response. The PI controller is applied to an electric motor model; this model was designed to regulate the motor speed of EHPS depending on the driver steering torque input changes, as demonstrated by modifying the input motor voltage of EHPS. Meanwhile, variations in hydraulic pressure in the piston cylinder are treated as a system load. Based on the experimental results, case 4 of the PI controller is a robust controller with good tracking, disturbance attenuation, and noise rejection while also ensuring system stability and improving system performance.