Smith predictor based sliding mode control for a class of unstable processes

Abstract

A strategy to regulate unstable processes using a modified Smith predictor based sliding mode controller (SP-SMC) is illustrated. The proposed scheme presents disturbance rejection and optimal control input usage with overall improved regulatory performances. The unstable process with time delay is first estimated using a simple measurement of limit cycle output obtained from a modified relay experiment. Then this paper extends a work on SP-SMC for unstable processes, which leads to significant improvements in its regulatory capacities of reference inputs and disturbances. A new control law is incorporated in the discontinuous part of sliding mode control such that the overall performance improves significantly. The metaheuristic search algorithm with some modifications has been implemented successfully to satisfy the new control performance index. The robustness of the controller is also tested under the process uncertainty. Illustrative examples show the simplicity and superiority of the presented design method over previously published approaches.

Smith predictor with sliding mode control for processes with large dead times

“…A similar switching function, which delivered a potential advantage for unstable processes with dead times, was presented in [22] as well.…”

“…The robustness to parameter variation and disturbance rejection was shown to be improved compared to the original structure of SP [18]. This structural technique was further improved for unstable processes [22] using power rate reaching law and the metaheuristic optimization algorithm.…”

PID Tuning Method Based on IMC for Inverse-Response Second-Order Plus Dead Time Processes

“…Increasing or decreasing γ allows one to modify the weight on the manipulated variable; for instance, when γ = 1, both, the IAE and IMV are of the same importance, and when γ = 0 only the IAE is considered. Several authors have used this type of objective function in order to measure the performance of different control strategies [50,51]; typical values of the suppression factor are 0 ≤ γ ≤ 8 [52,53].…”

Improved disturbance rejection with modified Smith predictor for integrating FOPTD processes

“…But, conventional Smith predictor [3] technique fails to perform satisfactorily for integrating processes with large dead time due to their inherent nonself-regulating nature. Over the last few decades, a decent amount of research findings are reported [4][5][6][7][8][9][10][11][12][13][18][19][20][21][22][23][24][25] towards modification and augmentation of the conventional Smith predictor [3]. Primarily Majhi and Atherton [11] proposed modified Smith predictor for integrating and unstable processes based on gain margin and phase margin criterion.…”

“…Although modified Smith predictor for second-order process with non-minimum phase using two controllers is proposed by Uma and Rao [23] signifies enhanced responses for unstable processes. Alternative approach towards modified Smith predictor with sliding mode control for processes with large time delay is provided by Mehta and Kaya [24], and the similar strategy for unstable processes is also proposed by Mehta and Rojas [25]. Among these reported schemes [8,9,11,19,[21][22][23][24][25] majority of the modified Smith predictor mechanism involves three controllers and their tuning policy is also not quite straight forward in nature.…”