Phase locked loop and a motor control servo
US4564794A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 23, 1985 |
| Grant date | Jan 14, 1986 |
| Priority date | — |
| Expiry date | May 23, 2005 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S388/912
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The speed of a DC motor (10) is controlled by a servo which includes a digital phase lock loop. The motor drives a tachometer whose pulse (22) frequency is low relative to the frequency of a clock (21). The clock continuously drives a counter (200) whose ever increasing number content is gated to a data latch (26) upon the occurrence of each successive tachometer pulse, thus this data latch contains a first time-number of ever increasing magnitude. A second data latch (24) contains a second number. The difference in magnitude of two consecutive time-numbers is indicative of motor speed. Initially, this second number is set to contain a reference number (REF) which is equal in magnitude to the number of clock pulses which will occur between adjacent tachometer pulses when the motor is running at desired speed. A pair of limit numbers (RANGEL and RANGEH) are provided to define the upper and lower limits of servo saturation. The difference between the first number and the second number is detected upon the occurrence of each tachometer pulse to generate a third or difference number (ERRA). This difference number is compared to the two limit numbers to determine if the servo is in satu…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.