It is necessary to identify the parameters of a controlled system for tuning control parameters. There are many studies on system identification for solving this problem. But, there are not many practical methods. Special test signals have often to be given to a controlled system for a long time in order to identify enough precizely to design the control system. This is not suitable for many actual systems.
In this paper, a simple method of system identification and tuning control parameters using ultimate oscillation like Zigler-Nichols method is mentioned. This is called α Parameter Method, and is based on the property of α parameter and λ parameter of a polynomial.
The relation between the frequency of ultimate oscillation and the coefficients of the partial term of the characteristic equation is formulated. The higher order coefficients of a polynomial are estimated from the lower order coefficients of it and the frequency of ultimate oscillation. In addition, the tuning method of I-PD control system using α parameter is mentioned.
α Parameter Method is compared with Zigler-Nichols method, and the usefulness for various controlled systems are showed by simulations.
