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A dynamical sliding mode control approach for long deadtime systems

Abstract:

The purpose of this work is to combine the concepts of sliding mode control and internal model control to design a Dynamical Sliding Mode Control (DMSC). The Internal Model Control (IMC) structure is used to obtain a simple and easy way to design the controller. This new approach eliminates the major sliding mode control problem: chattering. The process is reduced to a first-order-plus-deadtime (FOPDT) model, and it is divided in two components an invertible one and other non-invertible. A lead term is added to the invertible term and a lead-lag model is obtained and used to get the desired controller. The approach is tested in a high order system with elevated deadtime. The performance of the controller is tested under tracking and regulation conditions: change in the set point, persistent disturbance applied at a determined time, and addition of noise. Finally, a robustness test is conducted to prove how well the controller works when the plant ages. In every of these cases, the performance of the controller is satisfactory, also neither chattering nor instabilities are presented.