Development of parallel-connected pump-valve-coordinated control unit with improved performance and efficiency

Recently, there has been a growing demand for electro-hydraulic systems that can offer both high control performance and high energy efficiency. Traditionally, high performance is achieved using expensive high-bandwidth servo valve-controlled units. However, the inevitable throttling losses that occur in such systems severely decrease their energy efficiency. For a higher energy efficiency, pump-controlled systems have become the standard choice in this field. Nevertheless, their dynamic performance is inferior to that of valve-controlled systems. Considering the individual advantages of the valve- and pump-controlled units, our previous work proposed the idea of a parallel-connected pump-valve-coordinated system. In this study, a generic form of the coordinated control unit is discussed, and further improvements are made to the control design. In addition, comprehensive experimental studies are conducted with a variable-displacement pump and a servo motor-driven pump equipped with a direct pump-control component. Favorable results are obtained, demonstrating that the proposed system can achieve better tracking performance than a typical valve-controlled system, while simultaneously improving the energy efficiency.