A controller includes: an acquisition unit that acquires a deviation between an estimated amount and a target amount of a working fluid in the labyrinth chamber, and a fluid amount parameter corresponding to the estimated amount; and a control unit that executes feedback control including at least integral control of the deviation so as to control a regulation mechanism. When the fluid amount parameter is equal to or greater than a threshold, the control unit executes the feedback control in a state where the integral control is stopped.