Induction motor speed estimation using high frequency signal injection

For a final year university project i am trying to estimate the speed of an induction motor using high frequency signal injection. So far I have ran the motor through a three phase voltage source inverter using IGBTs controlled by PWM. I compared 3 sin waves (each 120 degrees out of phase with each other) with a triangular carrier wave and was successfully able to control the motor. I am now trying to superimpose a high frequency voltage with the fundamental voltage which should induce a current in the rotor, from which the speed can be calculated. I'm confused as to how to superimpose this high frequency signal (I have compared it with the 3 sin waves going into the IGBTs but this affects the speed of the motor) and also once i get the resulting stator and rotor currents i'm not sure how to extract the rotor position information from the. I am using the software PLECs to do this. Can anyone help or give an good links to papers etc. Thanks

Go to Google scholar and type in the heading of your forum query, you should turn up quite a few papers,cheers,Richard

Hi Colin-Frank Nola used to work at NASA, and he was granted several patents for devices that involved sensing the speed of induction motors.  Take a look here:Frank Nola's patentsI hope this is helpful.-Rick