Patent ID: 7489096
Filing Date: 2009-02-10
Classification: H02P

Abstract:
1. A method of determining an angular position of a rotor of a brushless direct current motor having a stator with multi-phase windings, control circuitry providing excitations switched one after another to motor phases such that the excitations produce stator flux vectors lying in different directions in a full 360 electrical degree range, and a measurement circuit that delivers responses for the phase excitations, the method comprising the acts of: selecting a main excitation stator flux vector resulting in a minimal inductivity shown by a measured response; selecting two other stator flux vectors, one of which is in a previous and another of which is in a subsequent direction with respect to a direction of the main excitation stator flux vector; and computing a ratio between differences of measured responses for the selected stator flux vectors in order to estimate an angular position of the rotor of the brushless direct current motor, wherein the selection of the main excitation stator flux vector is done by selecting a vector that corresponds to a maximal value among {i wherein the estimated position is obtained as m times π over p plus the calculated ratio between differences of measured responses for the selected stator flux vectors times π over 2p.