Application of hybrid fuzzy logic proportional plus conventional integral-derivative controller to combustion control of stoker-fired boilers

Abstract

Combustion control of an industrial stoker-fired boiler is to provide a continuous supply of steam at the desired condition of pressure. Because no efficient mathematical model of the stoker-fired boiler is available, it would be very hard to design its controller by using any traditional model-based method. Therefore, the most widely used controller for the boiler system is a conventional PID-type controller due to its simple control structure and ease of design. However, control performance of the PID-type controller suffers greatly from high uncertainty and nonlinearity of the system, large disturbances and so on. This paper presents a hybrid fuzzy logic proportional plus conventional integral-derivative (FUZZY P+ID) controller to improve the control performance yielded by the PID-type controller. The proposed FUZZY P+ID controller is constructed by using an incremental fuzzy logic controller in place of the proportional term in the conventional PID controller. The basic idea of this study is to reduce the parameters of a fuzzy controller to be tuned so that, in comparison with the PID-type controller, only one additional parameter should be adjusted. The proposed hybrid FUZZY P+ID controller is applied to several stoker-fired boilers. In order to demonstrate the effectiveness of the hybrid controller, the real application results on control of the stoker-fired boilers are reported and analyzed.