Servo control apparatus

A servo control apparatus comprising:

• a servo motor for driving a predetermined machine system;
• detection means for detecting both a position of said servo motor and a speed of said servo motor;
• position control means for producing a speed command signal based upon a difference between an externally entered position command signal and a position detection signal outputted from said detection means;
• speed control means connected to said position control means, for producing a first current command signal indicative of a value of a current to be supplied to said servo motor;
• mechanical resonance suppressing filter means for converting said first current command signal into a second current command signal used to suppress resonance and vibrations, which are caused by a characteristic frequency of said machine system;
• current control means for controlling a current to be supplied to said servo motor based upon said second current command signal;
• phase compensating means for calculating based on said first current command signal, a speed component corresponding to a phase delay occurring in a speed loop defined from said speed command signal up to said speed detection signal, which is caused by providing said mechanical resonance suppressing filter means;
• and for outputting said speed component obtained by said calculation as a phase delay compensation signal;
• and
• speed feedback signal producing means for producing a speed feedback signal by adding said phase delay compensation signal to said speed detection signal, wherein
• said speed control means produces said first current command signal based upon a difference between said speed command signal outputted form said position control means and said speed feedback signal.