Observer-based control of permanent-magnet synchronous motors

The so-called sensorless control problem for permanent magnet synchronous motors is studied. Specifically, discrete time observer algorithms are designed to estimate the angular position and velocity of the rotor using measurements of only the stator currents. These motion estimates are subsequently used for either velocity or position trajectory tracking discrete-time controller algorithms. The method for observer design is based on inversion of certain algebraic mappings that relate unknown state variables to measured outputs. The derivations of these mappings are facilitated by a time-scale decomposition that takes advantage of separated mechanical and electrical time constants. Rank assumptions related to these mappings clarify the underlying observability requirements and, in fact, lead to a method for maintaining observability at zero velocity. Detailed numerical simulations demonstrate successful sensorless motion control