Position Tracking Control for Valve Positioner System: Disturbance Rejection With an Adaptive Bandwidths-Tuned NESO

This article proposes a backstepping integral sliding mode control (SMC) scheme augmented with an adaptive bandwidth-tuned NESO for valve positioners with time-varying dynamics and disturbances. First, cascaded tracking differentiators filters based on the Fhan function generate smooth reference trajectories and PD-spectrum required by the observer with low phase lag. Next, an improved time-varying multiplier, driven by the observer’s tracking error and desired velocity, schedules the observer gains and bandwidth online, balancing high-precision state estimation and noise suppression during composite motion. The resulting adaptive bandwidth-tuned NESO supports the backstepping integral SMC, in which an integral sliding surface and a smoothed fal* nonlinearity is embedded to shape cascaded error dynamics, suppress overshoot, and improve steady-state accuracy. Experimental comparisons have demonstrated the efficacy of the proposed nonlinear control strategy, which has been shown to enhance control speed and accuracy while effectively resisting perturbations and reducing the overshoot phenomenon.