Experimental results on sliding mode control of hoisting crane subject to state constraints

In this paper sliding mode control (SMC) of a hoisting crane is considered. The proposed control method employs a time-varying switching line which moves with a constant velocity and a constant angle of inclination to the origin of the error state space. Then, it stops moving and remains fixed. Since at the initial time the line consists of these points in the error state space which represent initial conditions of the system, the reaching phase is eliminated. As a consequence, the considered system is insensitive with respect to external disturbance and model uncertainty from the very beginning of the control action. Furthermore, the proposed method ensures the monotonic error convergence to zero and it guarantees the minimization of the integral of the time multiplied by the absolute error (ITAE) with acceleration and velocity constraints. The proposed control method is verified with two experimental tests for the laboratory model of industrial crane. The experimental results presented in the paper confirm that practical application of the proposed SMC strategy gives favourable dynamic performance of the system and ensures its good robustness.