Impact of Spool Position Feedback on the Tracking Performance of Hydraulic Actuator Systems

This paper investigates the influence of spool position feedback on the tracking behavior of an electrohydraulic actuator system. Two servo valve configurations, with and without spool position feedback, are modeled and evaluated under identical operating conditions using a nonlinear backstepping position controller. The reference trajectory is generated from an ISO 8608-based random road profile to represent realistic excitation conditions. In the spool-feedback configuration, the valve spool dynamics are explicitly included in the control loop, whereas the configuration without spool feedback is modeled using a simplified valve representation. The performance of both configurations is assessed through time-domain responses and quantitative error metrics, including RMS tracking error, maximum absolute error, ISE, ITAE, and RMS control effort. The results show that incorporating spool dynamics reduces tracking deviations and improves transient behavior while maintaining a comparable level of control effort. These findings indicate that valve-level dynamics should be considered in the design of electro-hydraulic control systems, particularly in applications requiring accurate reference tracking.