Life evaluating device and robot system

A device for estimating a temperature of a lubricant in a transmission that transmits power from a motor to a robot joint, the device comprising:

• a thermometer to generate a room temperature for the motor;
• and
• a processor, connected to the motor, the transmission, and the thermometer, comprising hardware,
• wherein the processor is configured to:
• receive, as input from the motor, a current value of the motor and calculate, as output, a motor heat value based thereon;
• receive, as input from the motor and the transmission, a rotating speed of the motor and a frictional torque of the transmission, and calculate, as output, a frictional heat value in the transmission based on the rotating speed of the motor and at least one of the frictional torque of the transmission and at least one coefficient of friction of the transmission;
• and
• receive, as input from the thermometer, the room temperature, the frictional heat value, and the motor heat value and estimate, as output, the estimated temperature of the lubricant based thereon.