Trajectory Tracking Control of a 6-DOF Manipulator

A trajectory tracking controller is designed for a six-degree-of-freedom manipulator with high nonlinear and strong coupling based on a high-order fully-actuated system model. Firstly, the kinematic model and dynamic model of the six-degree-of-freedom manipulator are established by using the Modified D-H method and Lagrange dynamic equation, and the joint motor model is introduced into the system to generate a third-order dynamic model with voltage input, so as to avoid the negative impact of control for the motor itself on the tracking accuracy of the system. Then, the trajectory tracking controller is designed by direct parameterization method under the framework of high order fully-actuated system model, so that the nominal manipulator system can track the trajectory of the upper target in a finite time. Considering the internal and external uncertainty (IEU) in the practical manipulator system, a nonlinear disturbance observer (NDO) is designed to improve the anti-jamming ability of the system. In addition, a track-differentiator (T-D) is adopted in this paper to obtain the second stage status of the system, so as to avoid using acceleration sensors in the construction of trajectory tracking controller and nonlinear disturbance observer, which reduces the system implementation cost. Finally, a switching control strategy (SCS) is designed to improve the realization of the system due to the large output of the controller in the transient process. The effectiveness of the above theory is verified by simulation.