Research On The Manipulator Of Assisted Eating Based On Pneumatic Compliance Control

According to the latest national sample survey of disabled people,there are a large of people with arm disabilities in our society.At the same time,with the gradual deepening of the degree of aging,more and more old people need to be taken care of.For these people,our country invests a lot of manpower and resources in daily care every year.A device that can help the disabled and the elderly to finish their daily meals will help alleviate this problem.At present,most of the assisted eating robots in the domestic market are imported products.Designing an assisted eating robot can fill the gap in this field for our country.Based on this background,this paper studies an assisted eating robot based on pneumatic compliance control.Due to the compressibility of gas,the output force of pneumatic equipment is "soft".When pneumatic actuators contact with the environment,the compressible gas can be used as a buffer.So pneumatic actuators are friendly to people and very suitable for the occasions where people interact with machines.On this basis,compliance control is added to the control system of the assisted eating robot to ensure that the end-effector of the assisted eating robot has enough compliance when contacting with the user,so as to avoid excessive contact force.In this paper,starting from the actual needs of people with arm dysfunction for the assisted eating robot,the design indexes of the feeding manipulator are specified,and the structure of the feeding manipulator based on pneumatic compliance control is designed.Through kinematic analysis,the working space of the assisted eating robot is determined,and the typical working path is planned.The characteristics of switch valve and PWM modulation principle are discussed.Through reasonable simplification,the nonlinear mathematical model of pneumatic system based on switch valve is established by using mass flow equation,pressure differential equation and force balance equation,and the corresponding simulation model is built.The main components are selected in combination with the structure of the assisted eating robot.The typical working conditions of the assisted eating robot are analyzed and the mechanical properties of the typical load are discussed.The position based impedance control is added to the control system to realize the active compliance of the assisted eating robot.This paper discusses the basic principle of impedance control,analyzes the influence of expected stiffness,expected damping and expected quality on impedance control,and then clarifies the selection principle of impedance control parameters.The simulation of single degree of freedom aerodynamic execution contact environment load is carried out.A virtual prototype of the manipulator is built according to the 3D model of the manipulator,and the virtual prototype and control system are used for joint simulation.The movement of single joint,the trajectory of the end actuator and the typical working condition of the end actuator contacting with the user are simulated and analyzed.The joints' motions of the assisted eating robot are coordinated,and the steady-state position error of the end-effector is within 1mm.Under the action of impedance control,the contact force between the end actuator and the user is in a safe range.When user applies force to the end actuator,the assisted eating robot can move in compliance with the force.