Research On Direct Drive Position And Pressure Control Electro-hydraulic Servo System

Direct Drive Volume Control Servo System (DDVC) which combines AC servo motor technology and frequency conversion technology is a successful application in hydraulic. This new type of servo system is both easy to control, combines the characteristics of large hydraulic output, but also because there is no overflow throttling losses, the higher their energy efficiency, in certain situations, can replace the conventional valve control servo system, reaches high efficiency energy-saving purposes.A large number of relevant literature shows that: United States and Japan study on the direct-drive system is relatively mature, and the system has been applied to a number of related areas, made great economic benefits. However, the dynamic characteristics of the system is not very good so that applications are very well constrained, also, the current direct-drive system and its application more focused on the position control system, pressure control system is relatively less, it is also directly limited its application in related fields, thus carrying out the research on direct-drive system, improving its performance, is significant for its practical value and expanding its scope of application.Through the comparative analysis of Conventional electro-hydraulic servo system and direct drive servo system, this paper described the working principle of the direct-drive system, composition,strengths and weaknesses. Various parts of the system were established after detailed analysis of the direct drive position control and pressure control system model, and both open-loop frequency characteristics and stability were analyzed.For Direct Drive Volume Control System there is a big start and the steering phase delay, the operation process of positive and negative asymmetry and the long run to the hydraulic oil when the nonlinear characteristics, this paper designed the fuzzy PID controller based on the analysis between the traditional PID control and fuzzy control , and conducted the related simulation. Simulation results showed that the controller had good control performance.In the mathematical model based on the pressure control system simulation analysis show the output power with good control performance. Furthermore, in order to analyze system-related components of the system performance, this paper carried out the simulation about element matching aspects of the system ,which provides a theoretical basis for direct-drive system design and improve.This paper developed a research program, built position control and pressure control test-bed, designed the control systems, and carried on the experiment of direct drive position control and pressure control, the experimental results showed that the theoretical analysis is correct. Based on the analysis of the influence which caused by the pump to the system, and combined with the speed of the pump when DDVC system works, the principle to choose the pump in design of DDVC was derived.