| Steam boiler combustion system is a multi-input-multiple-output (MIMO) complex controlled process with characteristics of nonlinear and large delay. The input and output parameters are interrelated and coupled on each other, leading to the combustion process can’t achieve effectively control by adopting a single input-single output (SISO) system. In addition, due to the impact of large delay characteristics make the boiler combustion system unable to be adjusted in time when in the external interference.In connection with the problems of boiler combustion system, this paper first establish mathematical model of the boiler combustion system. The direct identification method of least squares parameter is used to identify mathematical model of MIMO system, then seek out the model law between different operating point, and make analysis on the system characteristics, as a result, to optimize the controller parameters. Secondly, to design the adaptive decoupling link of MIMO combustion system model for each operating point, the aim to decouple is turning the multi-variable system into several independent single-variable system, while eliminating the coupling effects of the system, improving system controllability. Finally, due to the time lag characteristic of the decoupled system still exists, when the system is subject to external interference or load changes, the conventional PID control methods can’t follow effectively; therefore the paper uses fuzzy adaptive PID control algorithm which not only combines the advantages of PID control algorithm, but also covers the characteristics of the adaptive algorithm, which is a simple method for optimal control.MATLAB simulation and experiment based on SMPT-1000 platform show that control system has better dynamic characteristic after decoupling compare to non-decoupling under the reasonable premise of system model inspection, the fuzzy adaptive PID control is superior to conventional PID control for its control quality and robust performance. |
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