Abstract:

This paper proposes a self-tuning PID model to overcome the time variation of transfer functions of painting robot joints. In the investigation, first, a dynamic analysis of the painting robot is performed. Then, the dynamic functions of the joints are simplified via a numerical method, and the transfer functions of each joint are established. Based on the transfer functions, the PID controllers at different positions are designed by experiments and the corresponding controller parameters are determined. Moreover, mathematical models describing the relationship between the PID parameters and the joint angle positions are set up by means of the least square method. According to the proposed models, the PID controllers at the next sampling time are finally designed and simulated. The results show that the designed PID controllers with a rapid response and a position accuracy of less than ± 0. 1 mm basically meets the requirements of spraying.

Key words: robot, PID control, self-tuning, modeling, self-adaptive model