Method of and apparatus for generating a unique index mark from the commutation signal of a D.C. brushless motor
US4392095A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 23, 1982 |
| Grant date | Jul 5, 1983 |
| Priority date | — |
| Expiry date | Jun 23, 2002 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B27/32
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A unique index mark is provided to avoid errors in addressing a memory location on a disk surface by correlating the commutation signal from a d.c. motor with a synchronizing signal present on one or more discrete tracks of the disk. The proportion of the synchronizing signals on one track depends on the number of phases of the d.c. motor although typically with a 2-phase motor one-half of the track contains the synchronizing signal, the other half of the track being erased. The commutation signals and the synchronizing signals are correlated using a microprocessor and a flip-flop. A sensing head looks for a synchronizing signal which is typically 10 individual data blocks of short duration. The detected blocks are counted in each half revolution of the disk, timed from the index edge and comparing the counts in successive half-revolutions in a comparator over several disk revolutions. The microprocesser then identifies from the comparator output the half-revolution of the disk in which the synchronizing signal was recorded. The microprocessor receives the output of the comparator and forces the output of the flip-flop hi setting an initial condition. Thereafter the microprocessor …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.