A New Approach in Design of Model-free Fuzzy Sliding Mode Controller for Multivariable Chemical Processes

Mohammad Khodadadi^1, , Mahdi Shahbazian¹ and Masoud Aghajani²

¹Department of Instrumentation and Automation Engineering, Ahwaz Faculty of Petroleum, PUT, Ahwaz, Iran

²Department of Chemical Engineering, Ahwaz Faculty of Petroleum, PUT, Ahwaz, Iran

Cite this paper:
Mohammad Khodadadi, Mahdi Shahbazian and Masoud Aghajani. A New Approach in Design of Model-free Fuzzy Sliding Mode Controller for Multivariable Chemical Processes. Journal of Automation and Control. 2015; 3(1):29-35. doi: 10.12691/automation-3-1-5

Abstract

Sliding Mode Control (SMC) as a mode of the Variable Structure Control (VSC) is known as an excellent robust control strategy in the field of uncertain and nonlinear control with high performance. However, chattering and process model dependency as main problems of the original SMC constrain its application. Also, in multivariable nonlinear process control, the interaction among the manipulated and controlled variables can degrade the performance of the controller. The objective of this paper is to design a new model-free Fuzzy Sliding Mode Control (FSMC) to solve these problems in MIMO process control. In this strategy, the equivalent –like term of the SMC’s control law is estimated using a self-tuned MIMO fuzzy logic inference system in order to overcome the dependency of the SMC to the process model and to reject undesirable effect of interaction toward improvement of robustness. Moreover, in design of linear sliding variables for switching term of the SMC, all states error are associated to lessen the interaction effect. Finally, the proposed strategy has been evaluated through implementation on a warm water tank system equipped with two manipulated servo valve to control temperature and water level. This system is nonlinear and affected by unknown disturbances. The results reveal that the purposed scheme is superior in servo tracking and unknown disturbance rejection performances in comparison with the classical PI control.

Keywords:
model-free fuzzy sliding mode control robust control multivariable process control interaction chattering model dependency unknown disturbance

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