Research On EHA Control Performance Based On HSV Flow Distribution

As a highly integrated pump-controlled drive unit,EHA is one of the latest products in the development of hydraulic systems in aerospace,industrial machinery and engineering machinery.Compared with traditional hydraulic systems,EHA has the characteristics of high power-to-weight ratio,high integration,high mobility and high efficiency,which accords with the latest development trend in the field of fluid transmission and control.However,most of the problems such as low frequency response and accuracy,high energy consumption and short life of EHA hinder its further development,so the new configuration and control methods of EHA are still being explored.As a typical component in digital hydraulic field,HSV can control the flow and pressure of hydraulic system with simple structure and low energy consumption,and has strong environmental adaptability.Therefore,this paper proposes an EHA system based on HSV distribution,which complements the advantages of EHA and HSV,and studies the design method of system principle,the characteristics of key components and the control method of flow distribution.The main research work of this paper is as follows:(1)Based on the analysis method of bypass throttling speed regulation loop,the key indexes of speed stiffness and speed amplification coefficient of the system are analyzed comprehensively from the flow output characteristics of HSV distribution unit and load output characteristics of the system.A design method of matching system parameters for load output characteristics and low-speed control process of hydraulic cylinder piston rod is put forward,which provides theoretical support for the design of EHA system based on HSV distribution.(2)The working principle and actual control characteristics of servo motors,hydraulic pumps and HSV are modeled and analyzed by combining experimental testing with system identification.By means of mechanism modeling and theoretical calculation,the selection and application requirements of accumulator in the system are pointed out,and the mathematical expressions of pressure distribution and flow direction at key points of the system under four quadrants are established,which lays a theoretical foundation for the system control method.(3)By compensating the flow deviation of hydraulic pump and solving the duty cycle of HSV control signal,the flow control of hydraulic pump and HSV based on flow control target and system pressure state is realized,and its feasibility is verified by experiments.On this basis,the flow distribution methods of piston rod velocity slope change and sine-cosine change under low-speed mode are further obtained,which can provide theoretical reference for flow control process of this kind of system.(4)The speed and displacement control characteristics of the EHA system based on HSV distribution are experimentally studied by building a prototype and a load simulation test bench.The results show that the system flow control method proposed in this paper is feasible for the process of hydraulic cylinder piston rod slope deceleration and acceleration,sine-cosine deceleration and acceleration,and the flow distribution method in low speed mode is feasible for its displacement control process.