A robot system has first and second joint control units that respectively calculate first and second current values to be supplied to first and second motors based on deviations between first and second operation targets for the motors that are input from a higher device and actual operation of output shafts of the motor, and control operation of the output shafts by supplying current to the motors based on the current values, and an error estimation unit estimating an error in operation of a second joint due to bending and/or twisting of a robot arm based on the first current value and the actual operation of the output shaft of the first motor, in which the second joint control unit calculates the second current value to control the rotation angle of the output shaft of the second motor in a manner compensating for an angle error of the second joint.

A robot system has first and second joint control units that respectively calculate first and second current values to be supplied to first and second motors based on deviations between first and second operation targets for the motors that are input from a higher device and actual operation of output shafts of the motor, and control operation of the output shafts by supplying current to the motors based on the current values, and an error estimation unit estimating an error in operation of a second joint due to bending and/or twisting of a robot arm based on the first current value and the actual operation of the output shaft of the first motor, in which the second joint control unit calculates the second current value to control the rotation angle of the output shaft of the second motor in a manner compensating for an angle error of the second joint.

A method for controlling the motor of a tool magazine that rotates around a horizontal rotation axis is configured so that: at least two indexing positions for the tool magazine are determined; the load torque acting on the tool magazine when stopped at said indexing positions is measured; an unbalance torque, which is the load torque when stopped at the indexing position at which the load torque when stopped is maximal, is calculated from multiple load torques when stopped; and the servo motor for the tool magazine is controlled on the basis of the unbalance torque.

A method for controlling the motor of a tool magazine that rotates around a horizontal rotation axis is configured so that: at least two indexing positions for the tool magazine are determined; the load torque acting on the tool magazine when stopped at said indexing positions is measured; an unbalance torque, which is the load torque when stopped at the indexing position at which the load torque when stopped is maximal, is calculated from multiple load torques when stopped; and the servo motor for the tool magazine is controlled on the basis of the unbalance torque.