The invention provides a control apparatus having error oversize detecting function. The control apparatus guiding in feed forward control can detect the abnormal position deviation rapidly. In a position deviation deducing processing part, the position deviation deducing value Err is calculated according to formula V/PG*(1-a)(in the formula, V represents 1-phase differential value of position command, PG represents position plug in a position controller, a represents the feed forward coefficient in a feed forward item calculating part). The abnormality of position deviation is horizontally detected according to error obtained by adding excess delta E.
Control device having excessive-error detection function