Research On Electro-Hydraulic Proportional Valve Controller With Motion Control Function

In recent years, with the development of the electro-hydraulic proportional control technique, the electro-hydraulic proportional valve gradually replaced the servo valve in lots of industrial equipment because of its low cost and good anti-contamination capacity. With a digital proportional amplifier, motion control can be achieved conveniently in electro-hydraulic proportional position control system, which has abroad application in engineering fields due to its simple structure, excellent reliability, easy to maintain, adapt to the high-power control and has some control accuracy. In this paper, a kind of digital proportional amplifier with better performance, high reliability and stability is proposed and implemented according to the performance requirement of the system. It is applied to the position control system of electro-hydraulic proportional valve controlled cylinder and has good control performance. In the paper, the major research work involves:(1) The overall design planning is proposed, and the hardware system of the slave computer is built with a ARM controller as the core, then software system is designed to achieve the main control function. Human machine interface of the host computer is designed to improve human-computer interaction of the whole system, which can make system debugging more convenient.(2) In order to reduce product debugging workload and time of the field engineers, a kind of PID auto-tunning method based on relay feedback approach and three-dimensional golden section search is developed, then PID auto-tunning is conducted in spool position control of electro-hydraulic proportional valve, and the final result has perfect control performance.(3) Hydraulic test bench of the position control system of electro-hydraulic proportional valve controlled cylinder is built, then nonlinear model of the system is established, and it can make the simulation result closer to the actual system, which shows strong nonlinearity.(4) The parameters of the three close loops in the system are tuned from the inside out, then static and dynamic characteristics are measured, respectively. Differential control method is applied to the control of the proportional solenoids in order to avoid the effect of their dead zone. In the PID controller of piston position close loop, the derivative item is processed in advance by a 4-order digital Chebyshev lowpass filter in order to give full play to its control function. Dead zone compensation is adopted to improve the control performance of the proportional valve, whose dead zone of the spool is quite large.At last, the main work of the paper is summarized, and for the shortages and disadvantages still existing in this study, some suggestions and expectations are put forward for further research.