# A globally exponentially stable position observer for interior permanent magnet synchronous motors

## TL;DR

This paper introduces the first globally exponentially stable position observer for interior permanent magnet synchronous motors, capable of operating effectively at standstill and high speeds under certain excitation conditions.

## Contribution

It presents a novel, globally exponentially convergent observer design for IPMSMs, including conditions for operation and a method to ensure observability at standstill.

## Key findings

- Observer achieves global exponential stability
- Effective at standstill with probing signals
- Validated by extensive experimental tests

## Abstract

The design of a position observer for the interior permanent magnet synchronous motor is a challenging problem that, in spite of many research efforts, remained open for a long time. In this paper we present the first globally exponentially convergent solution to it, assuming that the saliency is not too large. As expected in all observer tasks, a persistency of excitation condition is imposed. Conditions on the operation of the motor, under which it is verified, are given. In particular, it is shown that at rotor standstill---when the system is not observable---it is possible to inject a probing signal to enforce the persistent excitation condition. {The high performance of the proposed observer, in standstill and high speed regions, is verified by extensive series of test-runs on an experimental setup.