Friction compensation device, and robot control device

A friction compensation device comprising:

• drive torque calculation circuitry to calculate an output torque of a transmission mechanism from a motor's position, velocity, and acceleration, using an inertial force, a centrifugal force and a Coriolis force, and gravity on a shaft, the transmission mechanism being connected to a motor via the shaft to transmit a driving force of the motor;
• friction estimate value calculation circuitry including friction correction value calculation circuitry to calculate a friction correction value to correct a friction force on the shaft, by inputting, to a correction function, an absolute value of:
• each of the inertial force, the centrifugal force and the Coriolis force, and the gravity on the shaft output by the drive torque calculation circuitry as the output torque of the transmission mechanism;
• or a sum of the inertial force, the centrifugal force and the Coriolis force, and the gravity on the shaft output by the drive torque calculation circuitry as the output torque of the transmission mechanism, the friction estimate value calculation circuitry calculating a friction estimate value, using the friction correction value, the friction estimate value being an estimated value of the friction force on the shaft;
• and
• correction function determination circuitry to determine the correction function, wherein
• the correction function determination circuitry learns the correction function having an input of the absolute value of each of the inertial force, the centrifugal force and the Coriolis force, and the gravity on the shaft, and having an output agreeing with a drive torque estimate error that is a difference between a practical measured value of drive torque calculated from a motor current that is a current in the motor and a sum of the output torque of the transmission mechanism, a motor inertial force that is torque required to accelerate or decelerate the motor, and Coulomb friction and viscous friction calculated using the motor's position.

A robot control device comprising:

• program read circuitry to output a motion start point and a motion end point of a movement command in a robot program, and a maximum velocity specified in the robot program;
• acceleration and deceleration time determination circuitry to calculate, from data on the motion start point, the motion end point, and the maximum velocity, an acceleration time and a deceleration time among representative points of a motion based on the data on the motion start point, the motion end point, and the maximum velocity, as acceleration and deceleration times;
• position command generation circuitry to generate a position command in each predetermined cycle, on the basis of the data on the motion start point, the motion end point, and the maximum velocity, and the acceleration and deceleration times;
• and
• each-shaft motor control circuitry to control a robot on the basis of the position command, wherein
• the acceleration and deceleration time determination circuitry includes a friction compensation device including:
• drive torque calculation circuitry to calculate an output torque of a transmission mechanism from a motor's position, velocity, and acceleration, using an inertial force, a centrifugal force and a Coriolis force, and gravity on a shaft, the transmission mechanism being connected to a motor via the shaft to transmit a driving force of the motor;
• friction estimate value calculation circuitry including friction correction value calculation circuitry to calculate a friction correction value to correct a friction force on the shaft, using a value obtained by multiplying a correction parameter by:
• an absolute value of each of the inertial force, the centrifugal force and the Coriolis force, and the gravity on the shaft output by the drive torque calculation circuitry as the output torque of the transmission mechanism or an absolute value of a sum of the inertial force, the centrifugal force and the Coriolis force, and the gravity on the shaft output by the drive torque calculation circuitry as the output torque of the transmission mechanism, the correction parameter being a correction coefficient of friction that varies depending on an inertial force, a centrifugal force and a Coriolis force, and gravity on the transmission mechanism, the friction estimate value calculation circuitry calculating a friction estimate value, using the friction correction value, the friction estimate value being an estimated value of a friction force on the shaft, the acceleration and deceleration time determination circuitry calculating the friction estimate value required in calculation of the acceleration and deceleration times.