Research On Control Strategies Of Flexible Manipulator Driven By Pneumatic Muscle Actuators

Pneumatic muscle actuator(PMA)is a new type of the pneumatic actuators,which is similar to the biological muscle.It has the characteristics of the simple structure,light weight,large output force/self-weight ratio and good flexibility.It is widely used in the medical,rehabilitation and biomimetic robots.In this paper,the control strategy of the flexible manipulator driven by PMAs is the main research content,and the following specific work is carried out:Firstly,the human shoulder joint is used as a prototype,and the physiological mechanism of the human upper arm is analyzed.Ten PMAs are used to construct a new flexible manipulator that simulates the actual movement of the human upper arm.In addition to kinematics analysis of the series-parallel mechanism,the dynamics model of the flexible manipulator is applied by the Lagrangian method.Due to the position space of the execution end performs the strong coupling,the multi-objective genetic algorithm based on Pareto sorting is used to plan the joint space trajectory,which lays a foundation for the trajectory tracking control experiment of the execution end.Secondly,according to the characteristic analysis of PMA,the static test platform is built to obtain the related test data of PMA,and the static mathematical model is fitted and established.In addition,in order to compensate the model fitting error and overcome the external load changes,the dynamic test platform is built,and the PID controller based on the radical basis function(RBF)network is designed to achieve its precise position control.Then,considering factors such as many uncertainties of the dynamic model,system parameter changes and external disturbances,the PI robust sliding mode control based on the nominal model is proposed.The sliding mode control law is designed and the stability analysis is carried out.In order to improve the response speed of the control system and weaken the high frequency chattering of the sliding mode control,the robust term of the PI robust sliding mode control is improved.The fuzzy sliding mode control strategy based on the saturation function is proposed.The feasibility of two sliding mode control strategies is analyzed by the co-simulation.Finally,the test platform of the flexible manipulator driven by PMAs is built to complete its software and hardware design.The PI robust sliding mode control strategy and the fuzzy sliding mode control strategy are respectively used to perform the circular trajectory tracking control experiments of the execution end.The test results show that,based on the fuzzy sliding mode control strategy,the test curves of joint angles are closer to its expected curves,which can better guarantee the control precision of the trajectory tracking.At the same time,the fuzzy sliding mode control can make the system input be more continuous and smooth,effectively weaken the high-frequency chattering of the sliding mode control,and ensure the response speed and robustness of the control system.