Relay ladder control system for simulation and monitoring
US5777869A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 9, 1994 |
| Grant date | Jul 7, 1998 |
| Priority date | — |
| Expiry date | Dec 9, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05B19/056
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
An improved method of implementing and solving relay ladder logic, such as in programmable logic controllers, more efficiently to allow greater flexibility is provided. Solving relay ladder logic is performed with scan times dependent only upon the number of input and state changes on a scan, and the resulting number of flow changes at ladder connectors. The scan time will therefore be independent of the size of the ladder. The method comprises the steps of recording the structure of a relay ladder and the current flow on the ladder via a ladder coding convention which specifies adjacent relay ladder connections for a particular diagram. Based upon input or state variable changes or events, the process of the invention will act to toggle all of the ladder contacts associated with these events between open and closed positions. This procedure is accomplished by following precomputed lists of such contacts which will be affected by a particular event or change in system model variables. Once the scan events have been posted in the ladder, the scan continues with a processing sweep which computes flow change across one column of the ladder at a time. In each column during a scan, each…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.