Servo control apparatus

A servo control apparatus comprising:

• a servo control unit that calculates, using a detection value of a machine end position, which is a position of a machine system, and a detection value of a motor end position, which is a position of a motor that drives the machine system as a position feedback, a torque command for the motor such that the machine end position follows a position command;
• a model-response calculating unit that calculates a calculated value of the machine end position on the basis of the position command;
• a motor-end-movement-amount-during-stopping measuring unit that determines a point in time when the calculated value of the machine end position indicates that a calculated velocity of the machine end position changes to a state of velocity zero and measures a motor end movement amount during stopping, which is a displacement amount of the detection value of the motor end position in a period from the point in time until an absolute value of the calculated velocity of the machine end position changes to a value larger than a threshold of velocity set in advance, wherein the state of velocity zero is defined as a state during which the absolute value of the calculated velocity of the machine end position is equal to or smaller than the threshold of velocity set in advance continues for time equal to or larger than a threshold of time;
• and
• an error-correction-amount calculating unit that calculates an error correction amount on the basis of
• a parameter that is set in advance as a maximum change amount of a deviation between the machine end position during reversal of a moving direction of a feed shaft and the motor end position,
• the calculated value of the machine end position, and
• the motor end movement amount during stopping, wherein
• the servo control unit includes:
• a position feedback filter that calculates a low-frequency component of a difference between the detection value of the machine end position and the detection value of the motor end position;
• a correction amount filter that calculates a high-frequency component of the error correction amount;
• a position control unit that applies a position control operation set in advance to a value obtained by subtracting a sum of an output of the position feedback filter and the detection value of the motor end position from a sum of the position command and an output of the correction amount filter;
• a motor end position differential operation unit that differentiates the detection value of the motor end position;
• and
• a velocity control unit
• that applies a velocity control operation set in advance to a difference between an output of the position control unit and an output of the motor end position differential operation unit and
• that calculates the torque command.