The servo system is a complex system comprising several different interacting units and system parts – both hardware and software. The servo function comprises:

• Digital regulation of the poses, velocity and motor current of the robot axes.

• Synchronous AC operation of the robot motors.

During execution, new data on the poses of the robot axes is continuously received from the serial measurement board. This data is input into the position regulator and then compared with previous position data. After it has been compared and amplified, new references are given for the pose and velocity of the robot. The system also contains a model of the robot which continuously calculates the optimal regulator parameters for the gravitation, the moment of inertia and the interaction

An digital current reference for two phases is calculated on the basis of the resolver signal and a known relationship between the resolver angle and rotor angle. The third phase is created from the other two. The current of the phases is regulated in the drive unit in separate current regulators. In this way, three voltage references are returned which, by pulse-modulating the rectifier voltage, are amplified to the working voltage of the motors. The serial measurement board receives resolver data from a maximum of six resolvers and generates information on the position of the resolvers.