<p><P>PROBLEM TO BE SOLVED: To provide a periodic disturbance suppression device capable of correcting a system identification model error. <P>SOLUTION: The periodic disturbance suppression device includes: a periodic disturbance observer PDO which has a controller for generating a control command value r<SB POS="POST">n</SB>in a higher order, estimates periodic disturbance by multiplying an inverse system expressed by an inverse number of a system identification model, at an output yn of a control target plant P<SB POS="POST">n</SB>generated by the periodic disturbance, with a frequency component of the periodic disturbance as a suppression control target, and subtracting it from the r<SB POS="POST">n</SB>to suppress a periodic disturbance dn; phase calculation means (10, 11) for calculating a phase errorθ<SP POS="POST">ref</SP>by the system identification model error on the basis of a vector track drawn on a complex vector plane by respective frequency components of the periodic disturbance during periodic disturbance suppression control; and gain calculation means (20, 21, 22) for calculating a gain error G<SP POS="POST">ref</SP>by the system identification model error. A rotation vector P<SP POS="POST">ref</SP><SB POS="POST">n</SB>obtained by integrating theθ<SP POS="POST">ref</SP>and the G<SP POS="POST">ref</SP>is defined as a correction command value, and the system identification model is corrected. <P>COPYRIGHT: (C)2013,JPO&INPIT</p>
