Robust and smooth adaptive Variable Structure Control for induction motor drives

This paper presents the experimental validation for industrial applications of the new smooth VSC (variable structure control) algorithm with an adaptive gain for the indirect vector control of the induction motor. This control algorithm is used in the speed control loop, while in the current loops incorporates the SVPWM (space vector pulse width modulation) with the PI (proportional integral) controllers, maintaining the main characteristics of the VSC algorithm: fast response and good rejection to uncertainties and measurement noises. The presented algorithm has an adaptive sliding gain with a smoothed control law based on saturation function that reduces the chattering phenomenon that usually appears in the traditional VSC schemes. Thus, this regulator is compared with the adaptive SVPWM-VSC controller based on sign function, in order to prove the enhanced performance of the new proposed controller. The controllers have been tested using various simulation and real experiments, and in the proposed case, with and without load, taking into account the parameter uncertainties and measurement noise in the loop signal, in the rotor speed and in the stator current. Moreover, this new speed VSC controller incorporates a programmable limiter of the adaptive sliding gain that lets to fix the maximum speed error in a defined time interval. This work shows that the robust adaptive VSC regulator is a good and usable controller for the industrial applications, in both adverse conditions and suitable conditions.