Programmable logic controller for safety systems with reduced cross-wiring
AssigneeRockwell Automation Technologies, Inc.
InventorsArthur Paul Pietrzyk, Thomas Sugimoto
Life of this patent
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Abstract
A safety system programmable logic controller provides for cross connection of inputs and outputs of separate independent control modules through the use of virtual wire connections passing as messages on a single logical backplane. The backplane executes a high level protocol that provides wire-like indications of communication failures mimicking those of separate physical wires.
Claims34
A programmable logic controller for safety applications comprising:
- a backplane;
- at least two I/O modules electrically connectable to the backplane;
- first and second control modules electrically connectable to the backplane;
- wherein the backplane, I/O modules and control modules include circuitry supporting a connected communications protocol in which failure of a connection between modules may be detected by the modules;
- wherein each of a given first and second control modules redundantly execute a control program to:
- (i) open connections over the backplane with the at least two I/O modules;
- (ii) receive over connections, redundant input signals from the I/O modules;
- (iii) generate a redundant output signal based on the received input signals;
- and
- (iv) transmit over a connection the redundant output signal to at least one I/O module.
A method of implementing a safety system on a programmable logic controller having a backplane, at least one two I/O modules electrically connectable to the backplane, and a first and second control modules electrically connectable to the backplane, wherein the backplane, I/O modules and control modules include circuitry supporting a connected communications protocol in which failure of a connection between modules may be detected by the modules, the method comprising, for each given control module, the steps of:
- (i) opening connections over the backplane with the at least two I/O modules;
- (ii) receiving over connections, redundant input signals from the I/O modules;
- (iii) generating a redundant output signal based on the received input signals;
- and
- (iv) transmitting over a connection the redundant output signal to at least one I/O module.
Dependencies are inferred from the claim text.