Dynamic Analysis And Control Research Of 3-PSS Parallel Robot Based On Linear Motor

Linear motor has direct drive characteristics and "Zero drive" mode,which can overcome the shortcomings of servo rotary motor in accuracy and hysteresis.In this paper,based on the traditional structure of 3-PSS parallel robot,a new parallel robot is designed.Due to the direct drive characteristics of linear motor and the change of parallel robot structure,this paper needs to solve the kinematics and dynamics model again.In order to eliminate the disturbance and nonlinear brought by linear motor,a new control strategy is designed based on dynamic differential equation,and then the simulation experiment of 3-PSS linear motor parallel robot is carried out.The research contents of this paper include:1)A new 3-PSS parallel robot is designed based on linear motor,then establish the 3D model with Solid Works Software.The kinematics is solved based on screw theory.The velocity model is obtained and Jacobian matrix is derived.The reachable workspace is solved by MATLAB software combined with analytical method and Monte Carlo method.Then,based on the kinematic model,the dynamics of the robot is analyzed,and the generalized active force and generalized inertial force of each joint are solved.Finally,the Kane equation of the linear motor parallel robot is obtained.2)Aiming at the weak anti-jamming ability and poor stability of 3-PSS linear motor parallel robot,a nonlinear nonsingular fast terminal sliding mode controller based on deep deterministic policy gradient(DDPG)is designed with dynamic differential equation.The depth deterministic strategy gradient is used to approximate the nonlinear uncertainty in the nonlinear nonsingular fast terminal sliding mode controller to improve the tracking control accuracy and anti-interference ability.Lyapunov function is used to verify the stability and convergence of the control system,and DDPG algorithm is used to adaptively adjust the parameters of the controller to ensure the stability and robustness in various environments such as mass change,friction factor,external disturbance and modeling uncertainty.The feasibility of the proposed controller is verified by Simulink simulation,and compared with traditional terminal sliding mode control,nonsingular terminal sliding mode control and sliding mode control based on RBF(Radial Basis Function)neural network.The results show that the control strategy designed in this paper has the advantages of nonsingularity,finite time convergence,fast transient response,low steady-state error and high position tracking,and can effectively suppress the chattering problem in the process of uncertain system motion,and improve the motion accuracy and anti-interference ability.3)Establish the co-simulation model of MATLAB,ADAMS and ANSYS.The correctness of kinematics and dynamics models and the effectiveness of nonlinear nonsingular fast terminal sliding mode controller based on DDPG algorithm are verified.On the basis of the above theory,the static simulation of parallel robot and the feasibility of load and precision verification are done.Through the real machine verification test,the prototype can meet the requirements of the design parameters,and the work of this paper is summarized,and the future is prospected.