PURPOSE: To make the most of the holding capacity of a servo motor by providing a control means for comparing the temperature of the servo motor detected by a temperature sensor, with the reference value and automatically increasing/ decreasing the acting speed of a robot according to the compared result.

CONSTITUTION: The temperature of a servo motor 3 during the action of a robot is detected by a temperature sensor 4, and the detected temperature is converted into a digital signal by an analog-to-digital converter 5 and inputted to a CPU 1. In the CPU 1, the detected temperature is compared with the temperature reference value previously stored in a memory, by a comparing means 6. In the case of the temperature of the servo motor 3 being lower than the reference value, a servo driver 2 increases the acting speed command of the robot at a fixed rate, and in the case of the temperature being higher than the reference value, the servo driver 2 decreases the acting speed command at a fixed rate. The acting speed of the robot is increased/decreased by theservo driver 2 to the full holding capacity of the servo motor 3.