This paper proposes the use of a torsional angle control loop as an effective method to cancel torsional oscillations in two-mass (2M) high speed servo drives. First, an ideal evaluation assuming known the shaft angle and load torque shows the effectiveness of the proposed control. Then, a fullorder observer of the unavailable states is developed. Final evaluations using the full-order observer and including the effect of digital implementation and error in the estimated states, show the robustness of the proposed shaft angle control. NOMENCLATUREinertia K c Converter gain K E BEMF constant K dd Derivative gain of torsional angle loop K rd Feedback gain from torsional angle loop K ri Current loop feedback gain K rv Speed loop feedback gain K sh Shaft stiffness coefficient K T Torque constant R Resonant ratio coefficient t rcv Delay due to speed calculation t ri Delay due to current loop t rc Delay due to compensation scheme t rv Delay due to velocity loop T L Load torque T m Motor torque ω ar Anti-resonant frequency ω m Motor speed ω L Load speed ω r Resonant frequency

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