Trajectory Tracking Of Robotic Manipulators Based On Sliding Mode Variable Structure Control

In this paper,the trajectory tracking control strategy of manipulator is studied,the high precision and high speed tracking trajectory of manipulator end effector is realized by designing controller.Firstly,the Denso VP6242 G 6-DOF series manipulator coordinate system and its forward kinematics model are established according to the standard D-H parameter method.The inverse kinematics closed solution of any joint angle is obtained by analytic method.The simulation results show that the inverse kinematics of joint space can reproduce the desired trajectory of work space.The n-DOF serial manipulator general dynamics formula is derived according to the Lagrange equation method.According to the kinematic model of manipulator and the parameters of mechanical structure,the dynamic model of Denso manipulator is established,which is used for the simulation and verification of trajectory tracking control method of manipulator.Secondly,a nonsingular fast terminal sliding mode(NFTSMC)adaptive trajectory tracking control method based on radial basis function neural network(RBFNN)is proposed in this paper.The nonsingular fast terminal sliding mode hypersurface is adopted in the control scheme and the continuous terminal attractor is introduced into the switch control,which makes the system converge to the equilibrium point in a finite time.The adaptive RBF neural network is used to approximate the unknown nonlinear dynamics of the system,the adaptive compensation mechanism of approximation error and adaptive law of weights of neural networks are designed to realize the model free control.The simulation results show that the proposed control method can improve the steady-state accuracy,convergence speed,disturbance rejection performance and suppress the chattering of the system effectively.However,in practical engineering applications,the measurement error and transmission noise of the joint angle measurement signal are difficult to extract high quality filtering signal and differential signal.To solve the above problems,the improved method of nonsingular terminal sliding mode control based on tracking differentiator is proposed,the tracking differentiator module is used for filtering and differential of feedback signal,improved nonsingular terminal sliding mode is used to reduce the tuning difficulty of system parameter.The stability and finite time convergence of the manipulators system is analyzed on this basis.Finally,the improved nonsingular terminal sliding mode control strategy is applied to the Denso VP6242 G 6-DOF manipulator experimental platform,the effect of transmission delay on the control performance is analyzed and the solution is proposed.The experimental results show that the proposed control strategy can effectively improve the system convergence speed and steady-state tracking accuracy.