It is constructed so as to detect a joint movement position of a robot arm by
a position detector and a joint movement speed is calculated from change amounts
of the joint movement position and elapsed time and is compared with an allowable
movement speed and unlocking and locking of a brake are controlled so that the
joint movement speed of an arm at the time of brake unlocking becomes within a
constant value even when a shape, an attitude and a load condition of the robot
arm vary. Therefore, movement work of the arm by the brake unlocking can be performed
alone and a robot with high safety can be obtained.
