Parameter update method, parameter update apparatus, and non-transitory recording medium storing program for parameter update

A parameter update apparatus configured to update a setting value of a variable parameter ρ in a controller configured to control a control target based on a control input u, which is calculated according to a predetermined transfer function C(ρ) with the variable parameter ρ based on a deviation (y−r) between a control output y and a target value r of the control output y (u=C(ρ)·(y−r)), the apparatus comprising:

• an obtaining unit configured to obtain time-series data of the control input u and time-series data of the control output y observed in control with the controller;
• a calculation unit configured to calculate a value of the variable parameter ρ which minimizes an output value of an evaluation function based on the time-series data of the control input u and the control output y obtained by the obtaining unit;
• and
• an update unit configured to update the setting value of the variable parameter ρ to the calculated value by the calculation unit,
• wherein the evaluation function is a function J1 or a function J2 including a vectorial representation U of the time-series data of the control input u and a vectorial representation Y of the time-series data of the control output y,
• J1=∥Y−Y*∥2+∥F(ρ)·W∥2
• Y*=T·(C(ρ)−1·U+Y)
• J2=∥U−U*∥2+∥F(ρ)·W∥2
• U*=C(ρ)·(T−1·Y−Y)
• T included in the evaluation function is a model function indicating a reference value of the control output y corresponding to the target value r, F(ρ) includes an initial transfer function Cn obtained by assigning an initial value of the variable parameter ρ to the predetermined transfer function C(ρ) and the predetermined transfer function C(ρ) with the variable parameter ρ, and in the function F(ρ), the norm increases as a ratio or difference between the predetermined transfer function C(ρ) and the initial transfer function Cn is greater, and
• a weighing vector w included in the evaluation function is a vectorial representation of time-series data of a signal with frequency components most of which are in a frequency band in which a change in frequency characteristics of the predetermined transfer function C(ρ) from the initial transfer function Cn caused by a change in the value of the variable parameter ρ is reduced.