Extended relay ladder logic for programmable logic controllers

US5963446A · kind A · utility

Assignee

• Steeplechase Software, Inc. · US

Inventors

• Michael Klein · Schenefeld, DE
• William Perry Su · Huron Township, US
• Richard Leroy Mahn · Ann Arbor, US
• Per-Ola Gustav Forsgren · Solna, SE

Key dates

• Filing date: Aug 21, 1997
• Grant date: Oct 5, 1999
• Expiry date: Aug 21, 2017

Classification

• Technology area (CPC G): Physics
• CPC primary: G05B2219/13067
• WIPO field: Control
• WIPO sector: Instruments

Abstract

A digital computer implemented software system is provided for programming industrial logic controllers using a software package of the type utilizing relay ladder logic to represent control programs. The control program is executable by the controller to control the operation of one or more industrial devices. Using relay ladder logic, the control programmer is provided with a system to replace a coil with an ACTION block containing at least one complex expression. When the left side of the ACTION block is energized, the expression is evaluated. In a further embodiment, the programmer is able to replace a contact with a DECISION block containing a Boolean expression. When the left side of the DECISION block is energized, the Boolean expression is evaluated. If the expression evaluates as TRUE, the right side of the DECISION is energized.