Controller of fan coupling device

A controller of a fan coupling device, the fan coupling device including a drive shaft that is rotationally driven, a rotor coupled to the drive shaft, a housing configured to house the rotor, the housing being supported so as to be rotatable relative to the rotor, a fan fixed to the housing, a labyrinth chamber formed between the housing and the rotor in the housing and configured to transmit rotational motive power of the rotor to the housing through working fluid, and a regulation mechanism configured to regulate an amount of the working fluid in the labyrinth chamber, the controller comprising:

• an acquisition unit configured to acquire an acceleration parameter corresponding to an actual rotation acceleration of the fan and a deviation parameter corresponding to a deviation that is a value obtained by subtracting a target rotation speed of the fan from an actual rotation speed of the fan;
• a control unit configured to control the regulation mechanism by feedback control based on the deviation parameter;
• a prediction unit configured to predict that hunting occurs in the rotation speed of the fan, when an operating point of the fan expressed with the deviation parameter and the acceleration parameter belongs to a predicted region, out of the predicted region and a non-predicted region other than the predicted region defined by a coordinate system having the deviation parameter as a horizontal axis and the acceleration parameter as a vertical axis;
• and
• a restraining unit configured to execute, when the hunting is predicted to occur, a hunting restraining process of executing at least one of lowering an integral gain of the feedback control to be lower than when the hunting is not predicted to occur and increasing a derivative gain of the feedback control to be higher than when the hunting is not predicted to occur.