Robotic Servo Motor

What is a Servo Motor?

The servo motor is the motor that moves each axis of the robot. Robots require a wide range of motor-driven movements. A servomotor is a closed-loop servomechanism that uses position feedback to control its motion and final position. The motor has 3 phase power command from the KSD Servo Drive.

(*)  servomechanism 

Error Signal

The motor is paired with a resolver mounted on the driveshaft to provide position and speed feedback. In addition, the measured position of the shaft is compared to the command position.

On the other hand, if the output position differs from that required, an error signal is generated which then causes the motor to rotate in either direction, as needed to bring the output shaft to the appropriate position. As the positions approach, the error signal reduces to zero, and the motor stops.

Kuka Servo Motor

In the case of the KUKA Servo Motor, each axis motor has its own Servo Drive called a KSD which stands for KUKA Servo Drive. Each KSD is rated according to the motor that it is driving. For example, the Axis 2 motor will require more current than the wrist axes 4, 5, and 6 as the load is a lot greater on that axis.


The resolver feedback is fed back to the robot as a data signal after passing via the Resolver to the Digital converter card at the base of the robot. Therefore, on this card, the six resolver values are combined into a single data signal back to the robot PC.

See below for a table of the common drives and the robot types:

The Kuka KRC2 KSDs are rated depending on their power output in Amps

Below is a diagram showing the location of these diagnostic LEDs. For diagnostics, the Kuka spare KRC2 KSD has several LEDs

For removal of the Kuka KRC2 KSD see the guide below:

Kuka Servo Drive Part 5

Robotic Integration Solutions

We provide robots for sale that best suits your application. Likewise, we provide robot spares for all robot brands. See more Fanuc robots, Kuka Robots, ABB robots.  Please contact us for further information.