Sliding Mode Control of a Piezo-Hydraulic Actuator Considering Hysteresis

Piezo-hydraulic actuators are characterized by high load capacity, high resonant frequency, and large stroke, rendering them ideal for precision actuation applications. However, their control is complicated by inherent piezoelectric hysteresis nonlinearity. This study develops an enhanced Bouc-Wen model that incorporates a polynomial function of the input voltage to accurately characterize asymmetric hysteresis, while simultaneously reducing parameter redundancy. A comprehensive electro-mechanicalhydraulic coupled model is established via rigorous analysis of the component dynamics and fluid behavior within the sealed chamber. Displacement is measured using a compact Wheatstone bridge with strain gauges, and model parameters are identified via an adaptive differential evolution algorithm. An inverse multiplicative feedforward controller, based on the enhanced hysteresis model reduces the tracking root mean square error (RMSE) from 1.7025 to 0.9508 μm. Subsequently, a sliding mode control incorporated with the feedforward compensation achieves a significantly improved RMSE of 0.1046 μmunder sinusoidal reference signals, demonstrating high-precision trajectory tracking capability. The proposed modeling and control framework provides a solid foundation for deploying these actuators in high-performance precision motion systems.