System identification method, system identification device, and program

A system identification method that identifies, by a computer, values of a plurality of model parameters included in a model that reproduces input-output characteristics from input to output in a dynamometer system that includes a test piece and a dynamometer coupled to the test piece, the method comprising the steps of:

• measuring a frequency response from input to output in the dynamometer system under n sets of disturbances of different magnitudes (n is an integer of 2 or more);
• calculating a frequency response from input to output in n sets of models including i sets of common parameters (i is an integer of 1 or more) that do not vary by way of a disturbance and j sets of disturbance variable parameters (j is an integer of 1 or more) that vary by way of a disturbance;
• calculating values of a total of n sets of evaluation functions and a sum of the n sets of evaluation functions based on a frequency response measured under a k-th disturbance (k is an integer between 1 and n) and a frequency response of a k-th model;
• and
• identifying values of i sets of common parameters and j×n sets of disturbance variable parameters such that the sum satisfies a predetermined condition by repeatedly calculating the frequency response and the sum while changing the values of the i sets of common parameters and j×n sets of disturbance variable parameters, wherein
• the model is a multiple inertia system mechanical model including two or more inertial bodies and one or more shaft bodies coupling each of the inertial bodies,
• the common parameters include moments of inertia of the inertial bodies, and
• the disturbance variable parameters include at least any of a spring stiffness of the shaft body and a spring loss of the shaft body.