Spin-Coater Machine Control Via Passivity With Sliding Modes

In this paper, a novel control scheme for a spin-coater machine is presented, based on Passivity and Sliding Modes. The machine is used to make semiconductor thin films with a centrifugation force. A brushless direct current motor was selected as an actuator, its mathematical model is presented, including the mechanical and electrical dynamics. The control objective is the rotor speed regulation, with maximum acceleration. Taking advantage of the energy properties of the system, a sliding manifold is selected and, in order to reject the matched perturbations, the Integral Sliding Modes technique is applied. Then, with the unperturbed system, a passivity feedback is applied, to guarantee the stability around the desired equilibrium point. To complete the control scheme, an observer is included to estimate the unmeasurable estates. To prove the effectiveness of the proposed control scheme, it was implemented in a spin-coater machine and compared with a gain scheduled PID. The experimental results show a good performance of the closed-loop system, in spite of perturbations.