PID-Based Sliding Mode Controller for Nonlinear Processes

Abstract

Sliding mode control (SMC) has excellent robustness to model uncertainties and disturbances. This would make SMC an ideal scheme for process control applications where model uncertainties and disturbances are common. The existing SMC, however, has the major drawback of control chattering; i.e., the controller output is a discontinuous high-frequency switching signal. This makes SMC not suitable for most chemical processes where the manipulated variables are continuous and where high-frequency changes are not permitted. To eliminate chattering, a new proportional-integral-derivative (PID)-based sliding mode control (PIDSMC) suitable for the chemical process is proposed here. The proposed control system consists of three components: a compensation of process nonlinearity, a linear feedback of state tracking errors, and a PID control of the sliding surface function. The chattering is eliminated via the replacement of the discontinuous switching in the SMC by a continuous input determined by a PID scheme. An adaptive strategy is proposed to tune the PID parameters online to control the process states onto a sliding surface that characterizes the closed-loop performance. The proposed algorithm has been shown to be effective in controlling an inverted pendulum system and a typical pH neutralization process.

PID sliding mode control for steering of lateral moving strip in hot strip rolling

“…In this paper, to eliminate chattering, PID-based sliding mode control is proposed. The chattering of conventional sliding mode, which consists of discontinuous switching, is eliminated by the PID scheme, which has continuous control input [15][16][17]. The estimated sliding surfaces of the sliding mode can be written as When state trajectory stays on the sliding surface, sliding mode has occurred; i.e., ˆ0.…”

Gain adaptation for continuous sliding mode control

“…The most common way to circumvent this problem is to use a boundary layer approach or a quasi-sliding mode approach [1,2]. However, these approaches sometimes do not completely remove chattering as noted in [3] and are not adequate for the stability proof of the controlled system. A more elegant method that alleviate chattering is to introduce high-order sliding mode control (HOSMC) [4][5][6].…”

Simple adaptive methodology for chattering-free sliding mode control

“…However, as noted by in [7] this approach sometimes does not completely remove chattering so a proportional, integral, derivative (PID) control of sliding surface function is proposed [7]. Some problems can be handled using this approach, but the existence of the PID control gains satisfying the reachability condition is not always guaranteed.…”