Research On Control Method Of Miniature Volumetric Servo Actuator And Experiment

Electrohydraulic actuator is a popular actuating device with small size,light weight,fast response and high precision in the field of aerospace.With the development of electrical,computer and control technology,sometimes electrohydraulic actuator is challenged from electric or electro-mechanical counterparts.In terms of power density and extreme environment,electrohydraulic actuator is more competitive.For example,actuation in extremely narrow space such as wind tunnel,typical electric or electromechanical actuators bring about some problems including sensitive volume and heat radiation,as well as hard installation,measurement and carryover.Therefore,study on miniature electrohydraulic actuation and its control for applications with narrow space has important significance in both theory and engineering.In this thesis,a miniature volume-controlled electrohydraulic servo actuation system with two hydraulic cylinders used is proposed.Deformation and the control method for long and thin hoses connecting these two cylinders are studied.Firstly,working principle of the miniature electrohydraulic actuating system are analyzed.The main system structure and technical characteristics in operations are described for two parts: the hydraulic and the electric.Secondly,the mathematical model of the system is established.The lumped parameter method is adopted to model the hoses connecting these cylinders and is verified its validity.Aiming at considerable non-response zone in the non-pressurized oil station,a pre-pressurization scheme via an accumulator and solenoid valves is designed to eliminate or reduce the undesirable zone,which is affirmed by simulation on AMESim platform.Because of load sensitivity in pressurized volume and no adequate space for the sensor required,a disturbance observer(DOB)is proposed to improve the adverse influence of the hose deformation on the target cylinder.Solution of the mathematical model is implemented using Matlab/Simulink platform,and the difference from PID and sliding mode control methods is examined.The results show that the DOB control strategy is obviously better than PID in response speed,accuracy and robustness against external load.Compared with sliding mode control,DOB strategy has comparative robustness,but has superiority in output signal quality and engineering realization.In summary,the DOB control strategy is most suitable for the position control of the system proposed in this paper.Finally,component type selection and the electric motor testing,the typical work in development of the test bench is introduced.The test bench is completely established and preliminary Operated.