US Patent 10408151 Control device

A control device for a rotating element rotated by a four-stroke engine has a high degree of freedom in the choice of an apparatus to which the control device is applicable. The control device includes a rotation speed acquisition unit configured to obtain a rotation speed of the rotating element rotated by the four-stroke engine, and an undulation detection unit configured to, based on the rotation speed obtained by the rotation speed acquisition unit, detect a periodic undulation contained in a rotation fluctuation of the four-stroke engine, the periodic undulation having an angular period longer than a crank angle corresponding to four strokes.