Beyond the second order system in track following servos

Voice coil linear actuators are typically characterized as a basic second order system. However, component mechanical resonant frequencies often result in design degradations in the basic second order system. These conditions manifest themselves as possible servo loop instabilities in the frequency domain. This leads to poor static positioning, stiffness and dynamic positioning inaccuracies. This paper details the procedure used in the CDC Storage Module Drive family which, by the use of electronic compensation networks, provide track following improvement as well as minimizing the effect of mechanical resonant frequencies.