Adaptive Control Frequency Digital Pump

Hydraulic servo system use liquid to transmit energy as working medium. As the present, hydraulic servo system can be used in lots of aspects as usual, because of its advantages, such as simple structure, large outputting power, quick responding, smooth movement etc. But the liquid can leak easily that would hang down the efficiency of whole system. And that would set a limit to be used in some application. Pump, as the source of power of the system, play a key role in increasing of efficiency.Pressure-limited variable pump, the pump which delivery capacity is alterable is a common power equipment in hydraulic speed regulation. The variable pump is drove by electrical motor, running in the rating speed. It controls the system pressure through changing the delivery capacity automatically, adjust to the load. Also the variable pump has weak points, such as complex structure, leaking heavily, low efficiency, and driving motor is running in the rating mode all the working time, energy is wasted too much.As the developing of the AC frequency conversion technique, frequency conversion hydraulic speed regulation is becoming a brand new hydraulic speed style. It uses frequency converters, AC asynchronous motor, and constant rate pump. We change the rotating speed of the motor to adjust the pump's outputting rate, Frequency of the power which is used by the AC motor, can be changed by frequency converter. Then smooth infinite speed variation of the motor can be easily carried out. Constant rate pump can not change its delivery capacity. But the flow rate of the system can be changed according to the rotating speed of the motor .Then system pressure is under control.According to the practical requirement of the hydraulic speed regulation system which is basing on the frequency conversion technique. This paper introduces the fundamental principle of the hydraulic speed regulation. Build the system block diagram with the self-adapting control principle. According to the PWM frequency conversion speed regulation, we analyze the AC motor's mechanical characteristic as the frequency changing. Divide the frequency conversion device of the system into several modules. Control system is built with 8098SMC and HEF4752 which is used as SPWM special generate chip. Then it control the main circuit to output the AC that frequency is changing to run the motor. We use double closed loop control in this system, include speed feed-back and pressure feed-back. And then, we build the math model for the whole system, and use the Simulink of the MATLAB to do some simulation and analysis. Then we get the responding graph of the system changing with load. From the result of the simulation, the system we built is, high energy operating factor, simple institution. So the plan we set is feasible.