Control of permanent magnet motor drives using a new position estimation technique

Permanent magnet motor drives require absolute position information so that winding currents can be modulated in synchronism with the rotor. In recent years the eradication of such sensors has been the subject of many publications. This paper describes the principles and implementation of a new algorithm for combined flux-linkage and position estimation in permanent magnet motors. The algorithm uses the machine's flux-linkage versus current versus position characteristic and is thus able to take account of machine nonlinearities. The position estimator utilizes the characteristic in a generalized nonintrusive estimation scheme, which is effective over the whole range of operating conditions. The paper shows implementation of the estimator as embedded code in a digital signal processor-based drive system. Experimental results demonstrate the performance of the algorithm under steady-state and transient conditions, when the drive is operating closed loop sensorless, i.e., with the rotor position being provided by the position estimator.