Servo control system having function of automatically adjusting learning controller

A servo control system for a machine tool having a feed axis driven by a servomotor, comprising:

• a position command generator for generating a position command to drive the feed axis in a specific same operation pattern;
• a position detector for detecting the position of the feed axis;
• a positional deviation obtainer for obtaining a position command value generated by the position command generator and a position detection value detected by the position detector, and calculating a positional deviation that is the difference between the position command value and the position detection value;
• a position control loop including the position command generator, the position detector, and the positional deviation obtainer;
• a band limiting filter for attenuating a high frequency component of the positional deviation outputted from the positional deviation obtainer;
• a dynamic characteristic compensation element for advancing the phase of the positional deviation outputted from the band limiting filter;
• a learning controller including the band limiting filter and the dynamic characteristic compensation element;
• a sine wave sweep input unit for applying a sine wave sweep to the position control loop;
• a frequency characteristic calculator for estimating the gain and phase of position control loop input and output signals from the output of the position control loop at the time when sine waves are inputted to the position control loop;
• and
• a learning control characteristic evaluation function calculator for calculating an evaluation function that indicates a position control characteristic with the learning controller, based on a frequency characteristic by actual measurement calculated by the frequency characteristic calculator and a frequency characteristic of the learning controller, wherein
• the learning control characteristic evaluation function calculator modifies the configuration of at least one of the band limiting filter and the dynamic characteristic compensation element that constitute the learning controller, based on the value of the evaluation function.