Identification And Application Of Control Model In Real-time System Based On FFT

Self-tuning PID controller has been widely used in industrial proceeding control,research result shows that more than 90 percent control circuits make use of self-tuning PID controller. The PID controller parameters self-tuning technique is a new technique in high—tech engineering for gathering from orientation controlling, intelligence control, automating process control, is one of the current very popular research problems. However, because of parameter changes of controlled object,the parameter of PID controller also changes immediately, then it can better control the controlled object, therefore recognition of controlled object become a key problem.Aim at the problem of getting vibrating period and amplitude in methods of Z-N method and relay-tuning method, referring a algorithm of PID controllers parameters self-tuning based on frequency characteristic. The benefits to this algorithm is based on the identification of continuous spectrum, time-frequency conversion and modeling using FFT.Although the algorithm has been in the MATLAB simulation,but it has some shortcomings,such as energy leakage,which is the major factors leading to distortion of the spectrum; poor repeatability and poor real time.In this paper we refer a R(refine)-SF algorithm,it use a high-pass filter to filt lower frequency before of FFT.High-pass filter can make the low frequency part of signal equal zero,then the algorithm avoid energy leakage.Meanwhile use skilfully the nature of devide in the expression of frequency charactistic to eliminate the errors of frequency of filter in the denominator and nominator. On the poor repeatability found that differential controller cause input signal sharp amplitude, which cause the error when sampled.This paper communicate data between the smart meters and LabVIEW through OPC server as a bridge, and the whole process is controlled real-timely by LabVIEW and the smart meters to meet the requirment of real-time.The experimental results in the real-time system show that the frequency of object in this algorithm close to the real value,this method can applicate in other PID parameters tuning method. Therefore,this method has some promotional value.