Theoretical And Application Researches On Hydraulic Servo Control With Generalized Pulse Code Modulation

As the computer technology is widely used and developed, the digitization of electro-hydraulic control system and their components is a direction for progress. Electro-hydraulic servo control with on/off valves is a simple and efficient means, and a new development direction in fluid power transmission and control. The generalized pulse code modulation (GPCM) control hydraulic servo control, with the common on/off valves used as control components, is a cheap and practical new type of electro-hydraulic switch control system. It is applicalbe for the hydraulic control system, which has high flow rate, wide speed control range and foul work conditions. Theoretical and experimental studies of GPCM control are carried out in the thesis.The mechanism of pulse code modulation (PCM) control is described and several typical circuits of PCM control are established. The generalization pulse code modulation (GPCM) is proposed for the first time to solve the contradictions between the control precision and range, and between the stability and speed of PCM control system. Through the theoretical analysis, the mathematics model of GPCM hydraulic control is constructed, and it provides the base for study of GPCM control system. By means of the nonlinear analysis tools, the GPCM control system is studied profoundly, and the results verify that the GPCM control can realize the stable operation for electro-hydraulic control system. Moreover, the method to determind minimum orifice areas of GPCM is inferred, and the coding rule also is studied. All these studies make sure that the GPCM control system can obtain good performance of control precision and large speed regulation range.To take advantage of computational fluid dynamics (CFD), the theoretical analysis for the relation between the pressure distribution and flow rate following the flow direction in the GPCM valve is performed, and the results can be used to design the GPCM valve structure. A position servo control system is set up with a GPCM valve and hydraulic cylinder. The control strategy for the system is proposed by theoretical and simulation research. It is a hybrid control strategy, which include Bang-Bang control, PID control and fuzzy control. It does not depend on the system model precision and having the good performance verified by experiments.Finally, the GPCM position servo system is served as a driven unit for a multi-joints manipulator, and the manipulator positioning and tracking control are studied. The parameters of each controller of the manipulator is tuned to maintain that all joints move in harmony, and the positioning and tracking experimental results satisfy the requirements.