Control design for thrust generators with application to wind turbine wave-tank testing: A sliding-mode control approach with Euler backward time-discretization

Abstract

The control design for a propeller-based thrust generator used in a wind turbine testing platform is studied in this work. A mathematical model has been developed for the system including the motors and propeller. Subsequently, a continuous-time sliding-mode controller is designed based on the developed model and its stability and robustness have been addressed. An Euler backward time discretization method has been developed for the continuous-time sliding-mode controller to achieve a chattering-free implementation. The properties of the sliding-mode controller under the developed time discretization method e.g., finite-time convergence, and gain insensitivity have been studied analytically. In order to evaluate the developed sliding-mode control law under the discretization method, three known control strategies, i.e., gain-scheduling proportional-integral control, fuzzy control, and feedforward compensator strategies have been designed for the system. Some remarks are also given for the differentiator selection used to estimate the velocity. The experiments under different scenarios are then conducted and the results corresponding to all four controllers are provided along with a comparative analysis to identify the properties of each control configuration.