Robot control method and robot control device

A robot control method for controlling a motion of a robot arm having a plurality of joint portions,

• at least one of the plurality of joint portions which is targeted for correction having a pivot on which the robot arm is pivoted, the method comprising:
• calculating an angular velocity of the pivot based on a position command for the pivot;
• calculating an acceleration of the pivot based on the angular velocity of the pivot;
• calculating a reversal timing at which a direction of rotation of the pivot is reversed, based on the angular velocity of the pivot;
• calculating an acceleration at reversal of the pivot based on the acceleration of the pivot and the reversal timing;
• calculating a torsion correction amount and correction time for correcting torsion that occurs at the pivot at the reversal of the pivot, based on the acceleration at reversal and the reversal timing;
• and
• if the acceleration at reversal is smaller than a predetermined threshold value, correcting the position command for the pivot, based on a backlash correction amount for correcting backlash that occurs at the pivot, and if the acceleration at reversal is larger than the predetermined threshold value, correcting the position command for the pivot, based on the backlash correction amount, the torsion correction amount, and the correction time.

A robot control device for controlling a motion of a robot arm having a plurality of joint portions, the robot control device comprising:

• an angular velocity calculator that calculates an angular velocity of at least one of joint portions which is targeted for correction;
• a kinetic calculator that calculates a torque applied to the at least one joint portion targeted for correction, based on position commands for the plurality of joint portions;
• a reversal timing calculator that calculates a reversal timing at which a direction of rotation of the at least one joint portion targeted for correction is reversed, based on the angular velocity of the at least one joint portion targeted for correction;
• a reverse torque calculator that calculates a reverse torque applied to the at least one joint portion targeted for correction, based on the torque and the reversal timing;
• and
• a correction amount calculator that calculates, based on the reverse torque and the reversal timing, a torsion correction amount and correction time for correcting torsion that occurs, due to the reverse torque, at the at least one joint portion targeted for correction,
• the correction amount calculator outputs, if the reverse torque is smaller than a predetermined threshold value, a correction amount for correcting a corresponding one of the position commands for the at least one joint portion targeted for correction, based on a backlash correction amount for correcting backlash that occurs at the at least one joint portion targeted for correction, and outputs, if the reverse torque is larger than the predetermined threshold value, the correction amount for correcting the position command for the at least one joint portion targeted for correction, based on the backlash correction amount, the torsion correction amount, and the correction time.

A robot control device for controlling a motion of a robot arm having a plurality of joint portions,

• at least one of the plurality of joint portions which is targeted for correction having a pivot on which the robot arm is pivoted, the robot control device comprising:
• an angular velocity calculator that calculates an angular velocity of the pivot based on a position command for the pivot;
• an acceleration calculator that calculates an acceleration of the pivot based on the angular velocity of the pivot;
• a reversal timing calculator that calculates a reversal timing at which a direction of rotation of the pivot is reversed, based on the angular velocity of the pivot;
• a reversal acceleration calculator that calculates an acceleration at reversal of the pivot based on the acceleration of the pivot and the reversal timing;
• and
• a correction amount calculator that calculates a torsion correction amount and correction time for correcting torsion that occurs at the pivot at the reversal of the pivot, based on the acceleration at reversal and the reversal timing,
• the correction amount calculator outputs, if the acceleration at reversal is smaller than a predetermined threshold value, a correction amount for correcting the position command for the pivot, based on a backlash correction amount for correcting backlash that occurs at the pivot, and outputs, if the acceleration at reversal is larger than the predetermined threshold value, the correction amount for correcting the position command for the pivot, based on the backlash correction amount, the torsion correction amount, and the correction time.