Weight identification method and feedback control method

A feedback control method comprising:

• preparing a plurality of models, each of which includes at least a phase-delay model and a phase advancement model and is represented by combining the phase delay model and the phase advancement model;
• identifying a first weight that is assigned to one of the plurality of models;
• specifying a second weight that is assigned to at least one model that is other than the one of the plurality of models, based on the first weight;
• forming a control model of the plurality of models, the control model representing a control system;
• and
• feedback-controlling, based on a target value for controlling the control system, an amount of control of the control system controlled based on the targets value, the first and second weights, an instruction value for the control system that the amount of control becomes substantially equal to the target value,
• wherein the first weights assigned individually to the plurality of models are estimated based on a difference between the target value and the amount of control and a deviation between the instruction value and the value of equilibrium of the instruction value and parameters showing, phase delay models and parameters showing phase advancement models.