Microprocessor-based commutator for electronically commutated motors

Abstract

A commutator for an electronically commutated machine provides a microprocessor-based mechanism for translating discrete samples of machine angular rotor position information, either measured or determined indirectly, into commutation signals. Commutation control is achieved with shaft position information available only at discrete time instants, which are not, in general, the required commutation times. A filter and state observer provide estimates of the mechanical states of the rotating machine, i.e., angular position, velocity and acceleration. In one embodiment, a Kalman filter of variable gain is used for estimating the mechanical states. In another embodiment, a sliding mode observer is used for estimating the mechanical states. In the preferred embodiment, a combination of a sliding mode observer and a steady state Kalman filter is used to obtain the mechanical state estimates; the Kalman filter with small constant gains provides smooth tracking of a steadily rotating machine, while the sliding mode observer provides fast acquisition during transient conditions.