Abstract:

In view of the nonlinear problem of backlash caused by the gear transmission structure in the automatic pipe pile welding machine, an improved sliding mode controller design method based on the extended state observer is proposed. Firstly, the nonlinear and time-varying backlash model is equivalent to a global linearization model, and it is proved that the upper limit of the modeling error is bounded. For the situation with nonlinear input backlash and unknown external disturbance, a sliding mode controller and an improved sliding mode controller based on extended state observer are designed, respectively. The former can track the input signal asymptotically and stably, and has strong anti-interference ability, but it has large chattering. The latter uses the extended state observer to detect the unknown disturbance and directly compensates to the controller, which not only ensures the tracking error within the expected accuracy range, but also reduces chattering. The simulation results show that compared with the traditional sliding mode controller, the improved sliding mode controller system based on the extended state observer reaches the sliding mode surface faster and chatters less.

Key words: automatic control technology, welding robot, input backlash, backlash linearization, nonlinear system, robust control, sliding mode control, extended state observer