Continuous adaptive integral recursive terminal sliding mode control for DC motors

Parametric uncertainties and unmodeled disturbances limit the tracking performance improvement of DC motor systems. In this paper, a third-order continuous adaptive integral recursive terminal sliding mode (3-AIRTSM) control scheme is formulated for high-performance motion control of DC motors. The residual parameter uncertainties and unmodeled disturbances are synthesised as the lumped uncertainties. Then, the derivative of the lumped uncertainties is analysed whose upper bound is denoted by system state and control signal dependent terms with unknown coefficients. Meanwhile, a novel third-order sliding mode structure including integral element is constructed to obtain the chattering-free control input. In the proposed controller, the equivalent control term functions as feedforward model compensation, and the reaching control input handles the lumped uncertainties with adaptive gain coefficients, which reduces the design conservation and avoids the high-gain feedback issue. The closed-loop system stability analysis indicates that both tracking error and gain estimation errors converge to zero in finite time under the proposed controller. Comparative experimental results verify the proposed 3-AIRTSM controller can realize the best tracking performance with the modest or the lowest control effort, compared with 3-IRTSM and 3-RTSM controllers.