Development Of Electric-pneumatic Composite Actuator And Application In Feeding Aid Manipulator

Electric actuators have the advantages of high positioning accuracy and fast response speed,but the output capability of electric actuators is generally weak and the output characteristics are "hard".The cylinder has the advantages of relatively simple structure,strong output capacity and "soft" output characteristics,but its positioning accuracy has a big gap compared with the electric actuator.The electro pneumatic actuator combines the electric actuator and cylinder in structure and control system,so that it has both the positioning accuracy of the electric actuator and the output characteristics of the cylinder.In addition,with the continuous development of society and the continuous improvement of people’s living standards,China has gradually entered an aging society,followed by the need for a certain amount of labor to complete the nursing work of the elderly,therefore,the feeding aid manipulator came into being.In order to solve this problem,the electro pneumatic composite actuator is applied to the catering manipulator.The advantages of the positioning accuracy and the "soft" output characteristics of the composite actuator can be well reflected in the feeding aid manipulator.First of all,this paper introduces the advantages and disadvantages of the electric actuator and the cylinder,as well as the application and research status of the two.In addition,it also reviews the research status of the pneumatic compliance control and the feeding aid manipulator,and makes a preliminary understanding and grasp of the current relevant situation.Then,the determination of the basic principle and the design of the mechanical structure of the electro pneumatic composite actuator are completed.The mathematical models and simulation models of the electric actuator and the pneumatic system based on the on-off valve are established respectively.Moreover,the closed-loop control system of the electric actuator and the pneumatic follow-up system are simulated respectively to verify the positioning accuracy and force follow-up performance.Based on the above,the overall simulation model of the electro pneumatic actuator is established and the simulation analysis is completed.Then,the position control experiment of the electro pneumatic composite actuator is completed to verify the positioning accuracy and force follow-up ability of the feeding aid manipulator.After confirming that the electro pneumatic actuator can meet the target requirements through simulation and experiment,a series of technical indicators are set according to the actual user’s requirements for the feeding aid manipulator in order to apply it to the feeding aid manipulator.On this basis,the mechanical structure and driving structure of the manipulator are designed,and the forward and inverse kinematics are analyzed.According to the practical application environment of the manipulator,two typical cases of contact with users are selected for experiments.Besides,the mechanical characteristics of the two typical loads are measured,and the load model is established.In addition,in order to avoid hurting the users in the actual work,the compliance control strategy is studied,and the position based impedance control is finally determined.The influence of impedance control parameters is discussed at the same time.Then,based on the load model determined by the experiment,the single degree of freedom compliance control simulation of the feeding aid manipulator is carried out.By adjusting the impedance control parameters to control the single degree of freedom,the terminal contact force is within the index requirement.Finally,according to the mechanical structure and control system of the electrical composite actuator and the feeding aid manipulator,the trajectory planning of the dining manipulator is carried out.Moreover,the trajectory simulation of the end effector is carried out in the case of impedance control and non-impedance control.By adjusting the impedance control parameters to control the multi degree of freedom,the terminal contact force is within the index requirement.