Abstract
A new leaking valve-pump parallel control (LVPC) oil hydraulic system is proposed to improve the performance of dynamic response of present variable speed pump control (VSPC) system, which is an oil hydraulic control system with saving energy. In the LVPC, a control valve is operating at leaking status, together with a variable speed pump, to regulate the system flow of hydraulic oil simultaneously. Therefore, the degree of valve control and pump control can be adjusted by regulating the valve-pump weight ratio. The LVPC system design, mathematical model development, system parameter and control performance analysis are carried out systematically followed by an experimental for validation process. Results have shown that after introducing the valve control, the total leakage coefficient increases significantly over a wide range with the operating point and this further increases damping ratios and reduces the velocity stiffness. As the valve-pump weight ratio determines the flow distribution between the valve and the pump and the weight factors of the valve and/or the pump controls determines the response speed of the LVPC system, thus if the weight factors are constrained properly, the LVPC system will eventually have a large synthetic open-loop gain and it will respond faster than the VSPC system. The LVPC will enrich the control schemes of oil hydraulic system and has potential value in application requiring of fast response.
Highlights
Traditional hydraulic control systems are of two basic types: pump control and valve control [1].Valve control systems respond quickly to valve and load inputs but are less efficient due to throttling and overflow losses [2,3]
To improve the response of variable speed pump control (VSPC) systems, this paper develops a leaking valve-pump parallel control (LVPC) system, in which a leaking control valve is placed in parallel to a variable speed pump to collectively regulate system flow
Under the same weight ratio, the response speed of the LVPC system is proportional to the weight factors the valve the control and the pump characteristics control
Summary
Traditional hydraulic control systems are of two basic types: pump control and valve control [1].Valve control systems respond quickly to valve and load inputs but are less efficient due to throttling and overflow losses [2,3]. Traditional hydraulic control systems are of two basic types: pump control and valve control [1]. Pump control systems work efficiently since both system pressure and flow are closely matched with load requirements [4,5] but have a critical drawback: slow response. The variable speed pump control (VSPC) system is a new class of pump control system, using a variable speed motor to drive a fixed displacement pump, which is applicable to hydraulic elevators [6], shield tunneling machine [7] and water distribution systems [8,9]. Compared with traditional pump control systems, the VSPC system has advantages of lower cost, higher reliability and higher energy-efficiency. Response time is poor, due to the high inertia of the electric motor and the low overload capacity of the inverter driving it, preventing their use in applications requiring rapid response
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