The central control feature of Harmonic Drive ® Servo Systems is the closed loop position feedback. Only a targeted control of manipulated variables such as rotational speed, angular position and acceleration enables precise movements and adaptation to different requirements. Here, the unique strain wave principle of the gear used has a high rigidity, a positioning accuracy of a few arc seconds and an extremely long life without backlash. The central hollow shaft can be used for hosting the supply lines or drive shafts through the centre of the servo actuator. This property simplifies the construction in many applications, thus saving design and assembly time.