US 6,411,857 B1Granted

Redundant, multitasking industrial controllers with synchronized data tables

AssigneeRockwell Automation Technologies, Inc.

InventorMark A. Flood

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Abstract

An industrial control system employs a primary and secondary controller each having a processor and at least one I/O data table. Updating of the secondary processor's I/O data table is performed prior to the same data being transmitted to the controlled process. This eliminates possible retrogressive control at the time of switch-over of control from the primary industrial controller to the secondary industrial controller. Additional I/O data tables may be provided in each of the primary and secondary industrial controllers. In the case of the secondary industrial controller, this duplicate I/O data table temporarily holds data until the transmission is complete preventing the partial update of the working I/O data table of the secondary industrial controller. The duplicate I/O data table in the primary industrial controller allows simultaneous outputting of the I/O data transmitted to the controlled process without corruption while the user program of the primary industrial controller resumes execution.

Claims5

Dependent claims

A secondary industrial controller providing redundancy with a primary industrial controller executing a user program to control an industrial process, the secondary industrial controller comprising:

(a) an electronic memory holding:
(i) a copy of the user program describing the control of the process;
(ii) a secondary I/O data table holding output values changed by the user program;
(iii) a quarantine I/O data table;
(b) a processor communicating with the electronic memory and operating to:
(i) receive transmission of output values from a primary industrial controller;
at the end of execution of the user program by the primary industrial controller to the quarantine I/O data table;
of the secondary industrial controller
(ii) only after completion of the transmission of the output values into the quarantine I/O data table, transferring the output values from the quarantine I/O data table to the secondary I/O data table;
and
(iii) at a switch-over time, executing the copy of the user program to modify the output values in the secondary I/O data table and to transmit the output values from the secondary I/O data table to the industrial process wherein the electronic memory holds at least two user programs and wherein the secondary industrial controller receives identification of one current user program of the two programs from the primary industrial controller, and wherein,
at switch-over time, the processor executes the one user current program.

9 more elements

A method of providing back up of a primary industrial controller by a secondary industrial controller, each industrial controller having an electronic memory holding a user program describing the control of a controlled process and an I/O data table holding the output values provided to the controlled process, and having a processor communicating with the electronic memory, the method including the steps of:

(i) executing the user program in the primary industrial controller to write output values to the I/O data table of the primary industrial controller according to the user program;
(ii) transmitting at the end of the user program in the primary industrial controller, the output values from the primary industrial controller to the I/O data table of the secondary industrial controller without yet transmitting the output values to the process;
and
(iii) only upon completion of the transmission of the output values to the I/O data table of the secondary industrial controller, transmitting the output values from the primary industrial controller to the controlled process.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 09/303,940Filed 3 May 1999 · continuation
Priority: 7 May 1997
Granted: 25 Jun 2002
Term ends: Not estimatedThe source records don’t support an estimate.

Classification11 codes

G06F 11/2038
Where processing functionality is redundant: with a single idle spare processing component
G05B 19/0428
Using digital processors: safety, monitoring
G05B 19/058
Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts: safety, monitoring
G05B 2219/1159
Plc I-O input output: image table, memory