CONTROLLER FOR ROBOT

PURPOSE:To improve positioning accuracy by performing backlash correction relating to the positioning of a target position from the relation of gravity torques and the rotation directions of respective axes. CONSTITUTION:In a step 300, the world coordinates of a present position and the target position are transformed to joint coordinates and an axis variable (i) for specifying a robot axis is initialized to '1'. Then, in the step 304, the gravity torques Tci and Toi around an (i) axis of the respective present and target positions are computed. Then, the absolute value of the gravity torque Toi of the target position is compared with a prescribed threshold value Th, whether or not the values of the gravity torque Tci of the present position and the gravity torque Toi of the target position are below '0' is judged in the step 308 when it is equal to or more than the threshold value Th and a backlash correction amount DELTAtheta1 per interpolation cycle is obtained in the step 310 when it is equal to or more than '0'. Then, the arithmetic operation of the gravity torque is repeatedly performed until the axis variable (i) becomes the maximum value of '6' and a program is ended when it becomes the maximum value.