Electronic tachometer and combined brushless motor commutation and tachometer system
US4228396A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 26, 1978 |
| Grant date | Oct 14, 1980 |
| Priority date | — |
| Expiry date | May 26, 1998 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P6/06
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An electronic tachometer utilizes a transducer, typically an optical encoder disc, connected to a movable mechanical element. The transducer produces a pair of triangular waves of fixed relative phase, each having slopes proportional to the velocity of the mechanical element. The triangular waves are differentiated and the resultant signals are sampled by gating pulses derived from the triangular waves themselves. The samples are combined to produce an output signal having a magnitude proportional to element speed and a polarity indicative of direction. In a combined system in which the transducer is attached to the shaft of a brushless motor, another output of the same transducer is used for commutation control of the motor stator windings. This arrangement is particularly useful in a velocity servo system, in which the tachometer output is compared with a signal indicating desired motor velocity. The comparator output is used to modify the commutation control so as to produce the desired motor velocity. Position encoding also may be accomplished using the same transducer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.