A novel method for fuzzy scale factors scheduling in fuzzy PD+I with anti-windup system controllers

Abstract

ABSTRACT:The adjustment of scale factors in fuzzy controllers is a key factor in their correct functioning. In two-inputs fuzzy PID controllers, such as fuzzy PI+D (FPI+D) and fuzzy PD+I (FPD+I), the adjustment of scale factors is directly related to the adjustment of the gains of a PID controller using some of the traditional methods of adjustment. In systems that have control signal saturation, fuzzy PID controllers require anti-windup systems (AW) that limit the controller's integral action. In these situations, the adjustments of scale factors are not directly related to the adjustment of gains of a PID controller. Its use increases the overall gain system and creates an unbounded controller, which causes a faster response in the transient state but an oscillatory behavior and even critical stability in the steady state of the response. A solution to this problem is to reduce the output scale factor, to create a bounded controller, in which the tracking time constant is augmented. Consequently, the system presents more bounded oscillations in the steady state, but the transient response is slower. The main motivation of this research was to develop an approach for adjusting fuzzy PD+I controllers with an anti-windup system (FPD+I AW) with faster response in the transient state and without oscillatory behavior in the steady state. This approach uses a second fuzzy controller, which adjusts the output scale factor and the tracking time constant according to the actual system error. To verify the effectiveness of the proposed approach, a fuzzy PD+I controller with an AW system based on tracking back calculation and fuzzy scale factor scheduling (FPD+I AW-FSFS) was implemented and used to control the speed in a direct current motor with control signal saturation and was compared with the responses of FPD+I unbounded and FPD+I bounded controllers with AWs based on tracking back calculation, thereby proving the effectiveness of the proposed method. RESUMEN:El ajuste de los factores de escala en los controladores difusos es un factor clave para su correcto funcionamiento. En controladores difusos PID con dos entradas, como los controladores difusos PI+D (FPI+D) y PD+I (FPD+I), el ajuste de los factores de escala está directamente relacionado con el ajuste de las ganancias de un controlador PID, utilizando alguno de los métodos tradicionales de ajuste. En sistemas que presentan saturación en la señal de control, los controladores difusos PID requieren un sistema de anti-windup (AW) que limite la acción integral del controlador. En estos casos, el ajuste de los factores de escala no está relacionado directamente al ajuste de las ganancias de un controlador PID. Utilizar este ajuste de ganancias, incrementa la ganancia general del sistema, creando un controlador sin acotar, el cual presenta una rápida respuesta en el estado transitorio, pero un comportamiento oscilatorio, e incluso críticamente inestable en la respuesta en estado estable. Una solución a este problema es reducir el factor de escala de salida, creando u...

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Improvement DTC for Induction Motor Drives Using Modern Speed Controllers Tuning by PSO Algorithm

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