Prescribed Performance Output Feedback Control of the Independent Metering Electro-Hydraulic System

The independent metering system (IMS) realizes the independent adjustments of oil inlet and oil return by decoupling the control of the inlet and outlet orifices of the valve, which can significantly improve the energy utilization efficiency while ensuring the tracking accuracy of the system. In this paper, a predetermined performance control (PPC) strategy based on adaptive output feedback is proposed. Firstly, the K-filter observer is introduced into the IMS framework for the purpose of obtaining accurate estimates of the internal state variables that are not directly measurable. Secondly, the fuzzy logic system (FLS) is used to effectively compensate for the unmodeled error and external disturbance in system dynamics. Furthermore, by incorporating PPC, the control objective is to guarantee that all state errors converge to and remain within the prescribed performance function boundaries within a given time frame. At the same time, the dynamic surface control (DSC) method is used to alleviate the common ‘computational explosion’ problem in the backstepping design. In addition, the oil return pressure controller is designed to maintain the oil return back pressure at a low level, thereby reducing the pressure loss in the oil return path and improving the overall energy efficiency of the system. The theoretical analysis results show that the proposed controller can effectively improve the energy efficiency of the system while ensuring the tracking accuracy. Finally, the effectiveness and superiority of the control strategy are verified by comparative experiments.