抄録
This paper describes a method to measure the dynamic characteristics of nonlinear systems with 2-level inputs whose topological structures are unknown. For this purpose a functional model is proposed and expanded into a series of orthogonal functions, in order to simplify the process of measurement. The dynamic characteristics of a nonlinear system is represented in terms of the coefficients of the expansion series. A special test signal m(t) is proposed so that the terms of the expansion series become orthogonal to one another. The signal m(t) is generated by slightly modifying the well-known m sequences. An error function is defined which is an integral squared error between the response of the system and that of the model when the, signal m(t) is applied.
Assuming the order of the model-the number of the terms of the expansion series-to be known, the coefficients are determined so as to minimize this error function. Whether or not the assumed order of the model is adequate is tested by the normalized minimum value of the error function. Making use of the properties of the signal m(t), the coefficients are obtained from a certain correlation function between then input and output. It is not necessary to modify the onceobtained coefficients even if the order of the model is increased. The minimum value of the error function is also obtainable by using these coefficients without computing the response of the model. Several application results are presented.
.It is also shown that this method is theoretically applicable to nonlinear systems with multilevel inputs.
