Research On Trajectory Planning And Tracking Control Strategy Of Motion Constrained Manipulator

The gas insulated switchgear(GIS)widely used in high-voltage substations has the characteristics of being closed,intermittent and difficult to observe faults.Once the inspection personnel neglect the inspection and maintenance process,it may cause serious consequences,which has been a great challenge to the automated detection of high-voltage power systems.The seven-degree-of-freedom manipulator can move flexibly,and can complete the contact detection of the substation GIS through the end effector carrying the detection device.However,the substation environment is complex and each GIS gas room is closely arranged.The trajectory of the manipulator is restricted by many constraints,if the rotation of any joint is slightly deviated,it will be prone to collisions,resulting in property damage and even safety accidents.Based on this background,in order to better complete the autonomous detection of the substation GIS gas room,this paper conducts related research on the trajectory planning and tracking control of the manipulator.Through the mathematical foundation of kinematic modeling of the manipulator,this paper expounds the concept of the position and posture of the rigid body,and the homogeneous transformation matrix for transformation between different coordinate systems.The D-H parameter modeling method of the manipulator is explained.The coordinate system modeling of each joint of the multi-degree-of-freedom manipulator used in this paper is established to obtain the corresponding parameters,the forward kinematics model is solved,and the dynamic equation is derived.Aiming at the problem of contact detection of GIS gas room by constrained manipulator in complex substation environment,this paper analyzes the various constraints that need to be satisfied in the trajectory planning.To improve the success rate of trajectory generation and shorten the planning calculation time,a multi-stage optimization trajectory planning method based on successive refinement constraints is adopted,which transforms the trajectory planning problem into a discrete parameter optimization problem.Through two main steps of generating an estimated initial trajectory and optimizing for different constraints in stages,a path that satisfies the conditions is planned.The method of generating initial trajectories and the principle of multi-stage optimization is described.The effectiveness of the trajectory generation method is verified by simulation.Aiming at the trajectory tracking problem of manipulator motion,in order to realize the tracking control of joint angles,this paper proposes a nonsingular fast terminal sliding mode control(NFTSMC)method combined with the time delay estimation technique.The time delay can effectively estimate the uncertainty of the system,and the designed nonsingular fast terminal sliding mode surface can improve the dynamic response ability of the system.Furthermore,the stability of the designed controller is demonstrated using the Lyapunov function.The NFTSMC method is simulated in MATLAB to verify the effectiveness of the tracking method.Considering the complex environment of the substation and the high coupling of the applied seven-degree-of-freedom manipulator,in order to further improve the joint tracking accuracy of the seven-free manipulator under the condition of time-varying disturbance,this paper uses an adaptive control method based on the NFTSMC method.The new controller combines two adaptive gains,the steady-state error of the system can be reduced to a smaller range and the chattering problem can be suppressed.The stability of the designed controller is proved by using Lyapunov function.Finally,a comparative simulation is carried out under different control methods in MATLAB.The simulation results prove that the nonsingular fast terminal sliding mode control method based on the two adaptive gains proposed in this paper can make the system have smaller steady-state errors and faster response speed,it can also effectively avoid the high-frequency fluctuation of the system control torque,enhance the robustness of the system.The proposed method could meet the needs of the constrained manipulator for the contact detection of GIS gas room in the complex environment of the substation.