Pressure And Flow Control And Application Of Constant Displacement Electro-hydraulic Power Source

Electro-hydraulic power source is a device that provides power for the hydraulic system.It is made up of motors and pumps.Hydraulic pumps are classified into plunger pumps,gear pumps and vane pumps.Compared with the other two pumps,the plunger pump is more efficient,longer service life,and easy to control.Hence,it is diffusely used in electro-hydraulic power source.The functions of the power source universally include: flow,pressure,and power control.After its basic functions come true,improving its energy efficiency is a valid way to decrease energy consumption.This can also realize green and efficient operation.The role of the motor is to drive the pump to rotate.Variable speed drive can immensely promote the energy efficiency of the power source.A variable speed motor can be used to actuate a fixed displacement pump.Nevertheless,if the speed is controlled in this way to achieve pressure control,it is untoward to accommodate to the circumstance of frequent and bulky-scale flow variation.Furthermore,in motor control,the speed of the motor is still controlled by the means of the outer ring of the speed and the inner ring of the torque.This way has a lengthy control process.In view of the above issues,this paper propound to use the motor torque to control the pump output pressure in the process of pressure control.Thus the power supply and flow standalone pressure control is fulfilled.In comparison with variable speed control,the motor torque pertains to the inner control ring,and the response speed is swift.Furthermore,when the power source is running,the product of the output pressure and displacement of the pump is primarily equal to the output torque of the motor.Hence the control is more immediate.This means does not need to think about the imparity between pump output flow and load flow.In consideration of the interrelating relationship between the output pressure of the pump and the output torque of the motor is impacted by the efficiency of the two.On the basis of feedforward control,pressure bias feedback is brought in.This allows for high accuracy pressure control.In flow control,the motor speed is used to control the output flow of the pump.In the meantime,the introduction of flow feedback elevates the definition of flow control.The specific research work is as follows:Chapter 1 analyzes the application domain of electro-hydraulic power source and energy consumption at work.Illustrates the significance of saving energy and boosting its control accuracy.The research current situation and means of motor speed control in power sources at home and abroad are summed.Summing its application in some engineering outfit.Four combinations of variable speed power sources are analyzed.And summarized their research status.Chapter 2 analyzes the working theory of the injection machine and the influence of key parameters in the course of work.Analyzing several driving methods of injection machine,it is determined that the machine uses a servo motor to drive a quantitative pump system that can greatly reduce energy consumption.Analyzing the needs of injection machine at different stages when completing the injection molding process.The system control tactics of the working process of the power source and the flow pressure control method are settled.Make a good theoretical reserve for follow-up research.In the third chapter,different control methods of AC servo motor are studied.At the same time,the direct torque control method has demonstrated to be the plainest and most effective means.The mathematical model of the servo motor stator shaft system is researched.The model was built in Simulink and the speed control performance was analyzed.Moreover,in the motor torque control mode,the external input signal is used to control its torque.Then the torque control performance is analyzed.In the fourth chapter,the servo motor quantitative pump system is researched.It analyzes which factors impact its pressure and flow.The relationship between pump output flow and motor speed is analyzed.The relationship between pump output pressure and motor torque is analyzed.If the efficiency of the two is not take into account,the control of the pump flow can be achieved by controlling the motor speed.In like manner,the control of the pump pressure can be realized by controlling the motor torque.But in practical applications,the efficiency of the two cannot be neglected.Hence,feedback control is introduced and closed-ring control is used to improve control accuracy.The flow control and pressure control system of the servo motor quantitative pump is set up in the simulation software Simulink.Analyze the dynamic and static characteristics of pressure and flow control through simulation.Verify the viability of the proposed control means.On the basis of simulation and academic analysis,an experiment terrace was built according to the proposed working principle.Verify the feasibility of the proposed means through experiments.In chapter 5,the pressure and flow control methods in chapter 4 are applied to the injection molding machine system.The simulation model is established in Simulink.By analyzing the requirements of the demand in different phases of the working process,the control characteristics of each stage are analyzed.Finally,a complete working cycle is analyzed.After switching flow and pressure,the system responds quickly and can quickly reach a steady state.The sixth chapter summarizes the work of the paper.