System for measuring the position of an electric motor
US6703805B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Apr 12, 2002 |
| Grant date | Mar 9, 2004 |
| Priority date | — |
| Expiry date | Apr 20, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P6/18
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An electric system utilizes dynamic impedance changes in windings of an electric motor to measure/monitor mechanical position. The method employs a bridge amplifier to measure voltage at a center node or windings against a voltage derived from a reference network. When a winding of the motor is driven, the winding forms a voltage divider across the center node. Impedance changes in windings occur as rotor poles pass by stator poles. The center node voltage varies with these impedance changes in legs on either side; this variation with respect to the reference network corresponds to measurement of rotational position. These measurements provide position/velocity feedback to a servo controller as long as current runs through a winding. This position sensing also applies to controlling commutation for brushless DC motor. Impedance measurement use normal motor-drive current for excitation without additional sensing signals, extra “sense” windings, or external sensors.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.