Observer based stress reducing control of elastically coupled multi-mass systems

Elastically coupled multi-mass systems are a part of many industrial applications, like wind energy plants or drive trains in general. Dynamic load changes often cause peaks in the shaft torsion torque and jerk, resulting in damages to the system. A control strategy to reduce and / or limit this stress was presented, but needed difficult to implement and expensive measurements of the shaft torque. This paper presents an improved, observer based control strategy, eliminating the need for these expensive measurements, using only measurements usually already available. It also presents an easy to understand equivalent PID-cascade-structure for the control strategy, greatly improving the practical usability of the control presented.