Speed control of servo drives with a flexible couplings using fractional order state feedback

Using elastic couplings in servo motor drives may lead to torsional oscillations which are usually extinguished by reducing the bandwidth of the control system as a countermeasure. A high performance servo drive however needs fast dynamic characteristics. The conventional controllers, such as PI controllers, may not be able to improve the dynamic response while keeping the system stable. Fractional order modeling offers a good framework for flexible structures such as two mass servo drives. In this paper, the dynamic response and stability of two-mass servo drive is improved using a fractional order controller. The fractional order controller allows increasing the phase margin of the system while maintaining the bandwidth, hence damping the oscillations together with fast response is obtained. The proposed control system is verified by simulation results.