In an articulation system for a robot according to the present invention,
an eccentric rocking type planetary gear speed reducing mechanism is
used, but a two-stage speed reducing structure is not employed. Output of
an acceleration sensor (11) attached to an output shaft (7) of a speed
reducer (10) is passed through a band pass filter (12) to obtain a
vibration component. Based on the obtained vibration component and the
rotational phase of the motor detected by a pulse coder (13), a vibration
suppression correction torque corresponding to the rotational phase of
the motor is determined. The vibration suppression correction torque is
added to the torque command Tc to correct the torque command and causes
the motor (1) to operate in accordance with the corrected torque command.
The vibration suppression correction torque is determined by learning
processing and is updated until the vibration component is sufficiently
reduced. When the vibration component has been sufficiently reduced, this
updating operation is stopped, the vibration suppression correction
torque is fixed. Further, the torque command is corrected, and operation
of the motor (1) is controlled in accordance with the corrected torque
command.
