Accurate Motion Control of an Independent Metering Actuator With Adaptive Robust Compensation of Uncertainties in Pressure Dynamics

Regarding the motion control of independent metering actuators, energy efficiency can be improved while achieving accurate motion control through dynamic back pressure regulation. However, it increases the requirements for compensating the pressure dynamics, which includes the fluid compressibility part and the valve model part. Since the fluid compressibility and the valve flow characteristics may vary with the temperature, oil state, or valve wear, adaptive compensation is necessary to further handle the uncertainties. In this article, an adaptive robust control approach is proposed to further compensate for the uncertainties in the pressure dynamics in the motion control of the independent metering actuator. Specifically, to reduce the deviation in the valve flow model, an adjusting coefficient and a lumped error term are introduced to modify the nonlinear nominal flow model. Then, the effective bulk modulus and the initial control volume are estimated online to enhance the transient control performance when the pressure changes rapidly. The least squares estimation law is employed to directly adapt the denominator parameter and the input parameter in the pressure dynamics. Comparative experiments demonstrate that the approach successfully reduces the uncertainties in the pressure dynamics, leading to an improved transient and steady-state tracking performance in motion and pressure control.