this invention is a method and apparatus for automatically adjusting the command signal of a servomechanism , to improve the accuracy of control over the motion of an object . in one embodiment , the command signal is advanced in time , to compensate for the delayed response of the servo . the time advance is repeatedly and automatically adjusted so as to minimize the magnitude of the tracking error . each adjustment of the time advance is based on the value of a sampled error signal , taken at selected points in time . other parameters of the command signal , such as the amplitude and average level , can also be adjusted , and the adjustments for all parameters can be done simultaneously . for a given parameter , the error signal is sampled at those points at which misadjustment of that parameter is most likely to contribute to the error of the system . thus , in general , different parameters of the command signal are adjusted based on different sets of sampled points of the signal . the adjustment of one parameter can therefore be done without interfering with the adjustment of the others .