Servo robot

Servo robots were a type of robot, possibly powered by servos, used by humans in the 21st century. One servo robot was in control of and piloted the Silver Carrier, where it attacked the Second Doctor and Jamie while in orbit of Space Station W3. (TV: The Wheel in Space)

When humanity colonised Krosi-Aspai-Core, the Krotons mimicked the servo robots. This allowed them to obtain semi-setience. (PROSE: Alien Bodies)

Nyssa had a servo robot from Terminus named Loki who had a self-preservation function. (AUDIO: Cobwebs)