Sliding Mode Control for Pipe Pile Welding Robot's Trajectory Tracking with Time Delay

Pipe pile welding robot is a specialized machine designed for the automatic welding of Pre-stressed High-strength Concrete (PHC) pipe piles. In the application of the pipe pile welding robot, there is a problem that the motor response has an obvious time delay behind input. Considering this problem, this paper introduces time delay of motor speed into the motor model and proposes a fixed time delay sliding mode control combined with PI controller method for the system to achieve trajectory tracking. The existence condition of sliding mode surface and the controller's expression are proposed by Lyapunov-Krasovskii method. In simulation experiments, taking trajectory tracking control of the welding robot as an example, motor's trajectory tracking model with time delay is established. The constant velocity reaching law is selected to resist load interference in the design of sliding mode controller. The feasibility of the fixed delay sliding mode controller controlling the time-delay motor system for trajectory tracking is verified. Compared to the state feedback controller with Smith predictor, the simulation result shows that the proposed method has better capability on resisting the load interference.