| As a compact,effcient,intelligent and reliable mechatronic product,electro-hydrostatic actuator(EHA)is becoming more and more widely used in production and life.The system controls the motor through external instructions,the motor drives the hydraulic pump,and then drives the actuator to achieve the load action.When the rated pressure of the system is16 MPa,the external gear pump is more suitable for acting as EHA’s hydraulic pump because of its simple structure,light weight,strong pollutant-resistance and easy integration.However the radial imbalance force of the gear pump is serious,which will cause the wear and tear of the shaft and bearing and noise problem,this paper solves the radial imbalance force problem of the gear pump by adding pressure balance grooves.The motor of EHA usually chooses efficient,spark-free,powerful and servocontrolled brushless DC motor(BLDCM),in order to stabilize the speed and resist the load disturbance,This paper uses simple and effective PID control in the motor’s speed control loop,the parameters tuning of PID directly determines the performance of the system.The main work of this paper is optimizing the location of the gear pump’s pressure balance grooves and the PID parameters of the BLDCM,The main contents of this paper are the following 4 points:1 According to the given working condition,some important parameters of EHA’s hydraulic cylinder were designed,and the pump and motor were selected.2 Using 5 standard functions to test the bionic algorithms which are commonly used particle swarm optimization(PSO)algorithm and the latest proposed chicken swarm optimization(CSO)algorithm,the test results show that the CSO algorithm has higher accuracy and better ability to jump out of the local optimum under the same number of iterations,therefore,the CSO algorithm is chosen as the optimization method in this paper.3 The radial force of the external gear pump is divided into the meshing force and the hydraulic radial force,then according to the difference radial force of the gear,the gear is divided into 4 regions in the circumference direction: high pressure area,low pressure area,transition area and trapping area,in order to reduce the pressure of trapping area,the unloding grooves are opened on the end cover,and analyzed the location of the unloding grooves in detail.To solve the imbalance radial force problem of the gear pump,two pressure balance grooves were opened on the transition area,the CSO algorithm was used to optimize the starting location and end location of the pressure balance grooves,taking the minimum average radial force that the gear pump rotate a week as the optimization goal,getting the specific position of the pressure balance grooves,and used CFD software Pumplinx to analyze the flow field of the gear pump with pressure balance grooves andwithout pressure balance grooves.4 The mathematical model of BLDCM was analyzed in detail,and used Matlab/Simulink to establish the speed PID closed-loop control model of the BLDCM,then taking the integrated time absolute error(ITAE)of the system’s step response as the optimization goal,using the CSO algorithm tune the PID parameters.The simulation results show that the average radial force of the gear rotate one week is greatly reduced after adding the pressure balance grooves optimized by CSO algorithm,and the system performance of BLDCM closed-loop control system that the PID parameters tuned by CSO is much better than that tuned by traditional Z-N critical scaling method. |
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