Development of an Internal Model Sliding Mode Controller

Abstract

This paper shows the synthesis of a robust predictive controller from a process model that represents a good approximation for nonlinear chemical processes. The controller is designed using the internal model and sliding mode control concepts. This approach results in a fixed controller structure that depends on the characteristic parameters of the model. The controller performance is compared with internal model control and sliding mode control for different linear examples. All linear models present a controllability relationship (t 0/τ) of greater than 1. Simulation results indicate that the proposed controller can work for processes with elevated deadtime, despite modeling errors.

Sliding Mode Control with Predictive PID Sliding Surface for Improved Performance

“…The first step of the SMC design requires the design of a custommade surface. On the sliding surface, the plants dynamics is restricted to the equations of the surface and is robust to match plant uncertainties and external disturbances [15]. At the second step, a feedback control law is required to be designed to provide convergence of a systems trajectory to the sliding surface; thus, the sliding surface should be reached in a finite time.…”

Some long time delay sliding mode control approaches

“…A first order plus time delay (FOPTD) model, Eq. (1), is able to adequately represent the dynamics of many chemical processes over a range of frequencies [11]:…”

“…The design of a sliding mode controller (SMCr) from an FOPTD model was described by Camacho and Smith [11] but their approach requires some assumptions and approximations to deal with the time delay term. The internal model based sliding mode controller (IM-SMCr) approach takes advantage of choosing the invertible part of the model process to design the controller.…”

Discrete sliding mode control for robust tracking of time-delay systems

“…In this work, the input delay was compensated but the chattering reduction was not considered. Camacho and Smith developed sliding mode controllers for chemical processes with time-delay described by first order plus delay time dynamics (Camacho, Rojas, & Gabin, 2007;Camacho & Smith, 2000;Camacho, Smith, & Moreno, 2003). The chattering was removed by using smoother saturation function instead of signum function; however, the resulting responses contain larger overshoots.…”