Research On Robot Manipulators Trajectory Tracking Control Based On Adaptive Sliding Mode Control

With the rapid development of modern science and technology,intelligent equipment such as industrial robots had become the focus of development in China.The promotion of the performance of industrial manipulator is also conducive to improving production efficiency and product quality.Since the manipulator is a nonlinear,strongly coupled,time-varying system,with various uncertainties,such as unmodeled dynamics,parameter change,external disturbances,friction,and so on.The tracking accuracy of each joint of the manipulator can be affected easily because of these uncertainties,which can lead to the instability of the whole manipulator system.Therefore,it is of great significance to improve the trajectory tracking accuracy of the manipulator and make the manipulator in a good dynamic performance.In this thesis,the trajectory tracking control of double joint manipulator with uncertainties such as friction and external disturbances was studied.The main research work of this thesis is as follows:Firstly,the position and posture of the manipulator were described,then the kinetic energy and potential energy of the manipulator system were computed.The mathematical model of the double joint manipulator was established by using Lagrange function,and the characteristics of the manipulator were analyzed.Secondly,a PD controller based on time delay estimation was proposed to suppress the influence of uncertainties effectively such as friction and external disturbances on the trajectory tracking control performance of the double joint manipulator system.The PD controller was used to enable the manipulator to track the given trajectory.On this basis,the delay estimation was designed to compensate the uncertainties in the dynamic model of the manipulator to make the tracking performance of the manipulator better and reduces the tracking error.The effectiveness of the proposed PD controller based on time delay estimation was verified by simulation experiments.Finally,the delay estimation can generate the delay estimation error because of the inherent measurement noise,nonlinearity and limited sampling period which makes the double joint manipulator can not track the desired trajectory well.Therefore,an adaptive sliding mode controller based on time delay estimation was used to suppress the delay estimation error.The principle and property of the sliding mode control strategy and the chattering problem generated by the sliding mode were analyzed.The sliding mode controller was designed to ensure the global robustness.In order to reduce the delay estimation error and the chattering which caused by the sliding mode,and improving the robustness further,the adaptive law was designed to adjust the switching gain of sliding mode control,and the influence of uncertainty on the system was reduced.The effectiveness of the proposed adaptive sliding mode controller based on time delay estimation was verified by simulation experiments.