Disturbance observer based trajectory tracking control for a riveting robot

In order to solve the problem of higher chatter and lower trajectory tracking accuracy caused by external disturbances during the operation of a riveting robot, an adaptive control method consisting of a disturbance observer and a fractional-order sliding mode controller was designed. Firstly, the local dynamics model of the riveting robot was established by introducing the time delay estimation strategy, and the visible disturbances to the system model were observed in real time by using the disturbance observer. Then, a fractional-order sliding mode surface was designed to replace the traditional sliding mode control for the chatter, and a new convergence law was used to make the system move continuously and smoothly on the switching surface, and the adaptive strategy was designed to fully compensate for the external disturbances. Finally, the effectiveness of the designed controller was demonstrated by the Lyapunov function. The results show that the peak tracking errors at each joint of the robot are reduced by 50%, 59% and 63% respectively, compared with the conventional fractional-order sliding mode control. The controller can not only effectively eliminate the chattering problem caused by the large interference of the system, but also improve the robustness and trajectory tracking accuracy of the riveting robot. © 2023 Chinese Vibration Engineering Society. All rights reserved.