Servo control apparatus that performs dual-position feedback control

A servo control apparatus that performs dual-position feedback control, comprising:

• a first position detector for detecting position of a servo motor;
• a second position detector for detecting position of a load being driven by said servo motor;
• a first position error calculator for calculating a first position error based on a position command for said driven load and on position feedback from said first position detector;
• a second position error calculator for calculating a second position error based on said position command for said driven load and on position feedback from said second position detector;
• a third position error calculator for calculating a third position error to be used for position control, by adding to said first position error a difference taken between said first position error and said second position error and passed through a time constant circuit;
• a selector for selecting either said second position error or said third position error for output;
• and
• a learning controller for learning an amount of compensation necessary to bring said second position error or said third position error, whichever is output from said selector, close to zero, and for outputting said learned amount of compensation as an amount of compensation to be applied to said third position error.