Improving the rotor position estimation in permanent-magnet synchronous machines with a low-resolution position sensor

In this paper, a rotor position estimation based on a low-resolution position sensor is proposed. As vector control of an ac permanent-magnet synchronous machine requires the rotor position with sufficiently high resolution, the low-resolution sensor signal is transformed into a spatially quantized rotating vector and based on this vector, a vector-tracking observer calculates the corresponding high-resolution rotor position. The implementation of a basic vector-tracking observer topology is discussed. To reduce the remaining position estimation errors, two improvements are introduced: speed dependent observer gains and a reduction of the harmonic content in the input vector of the vector-tracking observer. These result in a sufficiently low position estimation error. The performance of the vectortracking observer is studied in steady state and in transient state by simulation as well as experiments on a hardware setup.