A force detector provided between a robot arm and a robot hand detects forces Fx, Fy, and Fz. A robot controller performs a filtering process for the forces Fx and Fy by a first low-pass filter of a cutoff frequency F.sub.c1, moves the robot hand so that the forces Fx and Fy become smaller, corrects a trajectory of the robot arm, performs a filtering process for the force Fz by a second low-pass filter of a cutoff frequency F.sub.c2 having a frequency higher than the cutoff frequency F.sub.c1, performs a threshold value determination for the force Fz, and stops the movement of the robot hand when the force Fz exceeds a threshold value during a fitting operation.

A motor controller according to the present invention includes a position command unit for commanding the position of a driven unit, a compensation filter unit for compensating a position command, and a servo control unit for controlling the operation of a servomotor based on a compensated position command. The compensation filter unit includes an inverse characteristic filter for approximating an inverse characteristic of a transfer characteristic from a motor position to a mechanical position, and a high frequency cutoff filter for reducing a high frequency component of the position command. The inverse characteristic filter is a filter for reducing a gain at a mechanical resonance frequency ω.sub.0. The high frequency cutoff filter has a constant “a” times high frequency cutoff frequency aω.sub.0 using a constant “a” of 1 or more, with respect to the mechanical resonance frequency ω.sub.0 determined in the inverse characteristic filter.

An abnormality detection method for detecting an abnormality of an encoder provided for a robot includes: obtaining corrected position information according to commanded position information output from a controller that designates the rotational position of a motor and an output signal output from the encoder; and, determining, after comparing the corrected position information with the detected position information according to the output signal output from the encoder, the abnormality of the encoder, if there is a difference greater than or equal to a predetermined value between the corrected position information and the detected position information. The controller removes a vibration component of the robot corresponding to the weight of an attachment load from the commanded position information and compensates for a time delay to obtain the corrected position information.

An abnormality detection method for detecting an abnormality of an encoder provided for a robot includes: obtaining corrected position information according to commanded position information output from a controller that designates the rotational position of a motor and an output signal output from the encoder; and, determining, after comparing the corrected position information with the detected position information according to the output signal output from the encoder, the abnormality of the encoder, if there is a difference greater than or equal to a predetermined value between the corrected position information and the detected position information. The controller removes a vibration component of the robot corresponding to the weight of an attachment load from the commanded position information and compensates for a time delay to obtain the corrected position information.

A control device calculates a position deviation between a position of a movable member designated by a position command and a measured position of the movable member by a position detector at each sampling period, adds a disturbance signal generated from a phase signal having a predetermined period to a drive signal generated from the position deviation to which an amount of correction is added, causes a motor for driving the movable member to operate based on the drive signal to which the disturbance signal is added, calculates the amount of correction by using a dynamic characteristic compensation filter in such a way as to reduce the position deviation, and changes a configuration of the dynamic characteristic compensation filter in such a way that an evaluation value related to magnitude of the position deviation satisfies a predetermined condition.

A force detector provided between a robot arm and a robot hand detects forces Fx, Fy, and Fz. A robot controller performs a filtering process for the forces Fx and Fy by a first low-pass filter of a cutoff frequency F.sub.c1, moves the robot hand so that the forces Fx and Fy become smaller, corrects a trajectory of the robot arm, performs a filtering process for the force Fz by a second low-pass filter of a cutoff frequency F.sub.c2 having a frequency higher than the cutoff frequency F.sub.c1, performs a threshold value determination for the force Fz, and stops the movement of the robot hand when the force Fz exceeds a threshold value during a fitting operation.

A servo control system includes a position command generator, a position detector for a feed axis, a positional deviation obtainer for calculating a positional deviation, a position control loop, a band limiting filter for attenuating a high frequency component of the positional deviation, a dynamic characteristic compensation element for advancing a phase, a learning controller including the band limiting filter and the dynamic characteristic compensation element, a sine wave sweep input unit for applying a sine wave sweep to the position control loop, a frequency characteristic calculator for estimating the gain and phase of position control loop input and output signals, and a learning control characteristic evaluation function calculator for calculating an evaluation function, which indicates a position control characteristic with the learning controller based on a frequency characteristic by actual measurement and a frequency characteristic of the learning controller.

A force detector provided between a robot arm and a robot hand detects forces Fx, Fy, and Fz. A robot controller performs a filtering process for the forces Fx and Fy by a first low-pass filter of a cutoff frequency F.sub.c1, moves the robot hand so that the forces Fx and Fy become smaller, corrects a trajectory of the robot arm, performs a filtering process for the force Fz by a second low-pass filter of a cutoff frequency F.sub.c2 having a frequency higher than the cutoff frequency F.sub.c1, performs a threshold value determination for the force Fz, and stops the movement of the robot hand when the force Fz exceeds a threshold value during a fitting operation.

A control device calculates a position deviation between a position of a movable member designated by a position command and a measured position of the movable member by a position detector at each sampling period, adds a disturbance signal generated from a phase signal having a predetermined period to a drive signal generated from the position deviation to which an amount of correction is added, causes a motor for driving the movable member to operate based on the drive signal to which the disturbance signal is added, calculates the amount of correction by using a dynamic characteristic compensation filter in such a way as to reduce the position deviation, and changes a configuration of the dynamic characteristic compensation filter in such a way that an evaluation value related to magnitude of the position deviation satisfies a predetermined condition.

A servo control system includes a position command generator, a position detector for a feed axis, a positional deviation obtainer for calculating a positional deviation, a position control loop, a band limiting filter for attenuating a high frequency component of the positional deviation, a dynamic characteristic compensation element for advancing a phase, a learning controller including the band limiting filter and the dynamic characteristic compensation element, a sine wave sweep input unit for applying a sine wave sweep to the position control loop, a frequency characteristic calculator for estimating the gain and phase of position control loop input and output signals, and a learning control characteristic evaluation function calculator for calculating an evaluation function, which indicates a position control characteristic with the learning controller based on a frequency characteristic by actual measurement and a frequency characteristic of the learning controller.