Graphical interfaces for monitoring ladder logic programs

• US 5,321,829 A
• Filed: 07/20/1990
• Issued: 06/14/1994
• Est. Priority Date: 07/20/1990
• Status: Expired due to Term

• Current Assignee: ICOM Incorporated
• Original Assignee: ICOM Incorporated
• Inventors: Zifferer, Scott C.
• Primary Examiner(s): Kulik, Paul V.
• Assistant Examiner(s): ORZECH, JENNIFER
• Application Number:
  US07/556,958
• Time in Patent Office: 1,425 Days
• Field of Search: 395/575, 395/600, 395/650, 395/191-192, 395/147, 395/159, 364/147, 364/188, 371/29.1
• US Class Current: 714/46
• CPC Class Codes: G05B 19/056 Programming the PLC
• CPC Class Codes: G05B 2219/13142 Debugging, tracing
• CPC Class Codes: G05B 2219/14073 Real time modeling of plc behaviour, display pictogram of system
• CPC Class Codes: G05B 2219/14093 Display matrix of relay, contact symbols, select and show time
• CPC Class Codes: Y10S 715/97 Instrumentation and component modelling, e.g. interactive control panel

Abstract

A menu-driven system for developing Man-Machine Interfaces (MMI) for use in the graphical monitoring of ladder logic programs executing in programmable logic controllers PLCs. The Man-Machine Interfaces graphically depict plant processes controlled by the PLC. Data from the PLC representing plant process events (flows, state changes, tank levels, etc.) are communicated to the Man-Machine Interfaces. A Development System provides a programmer'"'"'s "tool box" for constructing the Man-Machine Interfaces. Ladder logic programs and databases associated therewith are imported and accessed by the Development System for use in the development of the Man-Machine Interfaces. A Runtime System provides an execution environment for the Man-Machine Interfaces. The Runtime System has the ability to access ladder logic programs during monitoring operations. A user can "hot-key" to the ladder logic program for trouble-shooting purposes.

Claims

1. A computer-based method of monitoring a ladder logic program executing in a programmable logic controller, comprising the steps of:

(a) drawing a graphical object on a monitor attached to a computer to depict a plant process controlled by the programmable logic controller, wherein the graphical object is selected from a group comprising Bargraph objects, Numeric objects, Trend objects, and State Change objects;

(b) electronically associating the graphical object to an element of the ladder logic program;

(c) setting a polling interval on the computer to indicate how often a value for the associated element is to be retrieved from the ladder logic program executing in the programmable logic controller;

(d) specifying action parameters on the computer to indicate changes in the display of the graphical object that are to occur in response to changes in the value of the associated element;

(e) responding to a triggering of the polling interval by transmitting a query message from the computer to the programmable logic controller requesting a value for the associated element and by resetting the polling interval; and

(f) responding to the value for the associated element being input from the programmable logic controller to the computer by changing the display of the graphical object in accordance with a change in the value of the associated element.

2. The method of claim 1, wherein the electronically associating step comprises the step of accepting an address entered by an operator at an entry field displayed on the monitor, the address identifying a memory location in the programmable logic controller associated with the element.

3. The method of claim 1, wherein the electronically associating step comprises the step of:

(1) accepting a designated key entered by an operator into the computer, and displaying a list of symbols used in the ladder logic program on the monitor in response thereto;

(2) searching the list for a symbol representing a specific element in the ladder logic program; and

(3) electronically associating the graphical object to the specific element.

4. The method of claim 1, wherein the electronically associating step comprises the steps of:

(1) accepting a designated key entered by the operator into the computer, and displaying the ladder logic program on the monitor in response thereto;

(2) searching through the ladder logic program for a specific element; and

(3) electronically associating the graphical object to the specific element.

5. A method of monitoring a ladder logic program executing in a programmable logic controller, comprising the steps of:

(a) displaying the graphical object on a monitor attached to the computer to depict a plant process controlled by the programmable logic controller, the graphical object being electronically associated with an element of the ladder logic program, wherein the graphical object is one selected from a group comprising Bargraph objects, Numeric objects, Trend objects, and State Change objects;

(b) initializing a polling interval on the computer for the graphical object, the polling interval indicating a waiting period before a value for the associated element is to be retrieved from the programmable logic controller;

(c) responding to a triggering of the polling interval by transmitting a query message from the computer to the programmable logic controller requesting a value for the associated element and by resetting the polling interval;

(d) responding to the value being input from the programmable logic controller to the computer by changing the display of the graphical object in accordance with a change in the value of the associated element; and

(e) responding to an entry of a hot-key command by an operator of the computer by accessing a "hot-key" data structure in the computer and extracting therefrom an electronically stored filename which identifies a location on the computer where a copy of the ladder logic program is stored, and displaying the copy of the ladder logic program on the monitor at a specific rung thereof.

6. The method of claim 5, further comprising the step of preventing unauthorized access to the copy of the ladder logic program.

7. A computer-based apparatus for monitoring a ladder logic program executing in a programmable logic controller, comprising:

(a) a computer, coupled to the programmable logic controller, having a monitor attached thereto, the computer further comprising;

(1) means for drawing a graphical object on the monitor to depict a plant process controlled by the programmable logic controller, wherein the graphical object is selected from a group comprising Bargraph objects, Numeric objects, Trend objects, and State Change objects;

(2) means for electronically associating the graphical object to an element of the ladder logic program;

(3) means for setting a polling interval on the computer to indicate how often a value for the associated element is to be retrieved from the ladder logic program executing in the programmable logic controller;

(4) means for specifying action parameters on the computer to indicate changes in the display of the graphical object that are to occur in response to changes in the value of the associated element;

(5) means for responding to a triggering of the polling interval by transmitting a query message from the computer to the programmable logic controller requesting a value for the associated element and by resetting the polling interval; and

(6) means for responding to the value for the associated element being input from the programmable logic controller to the computer by changing the display of the graphical object in accordance with a change in the value of the associated element.

8. The apparatus of claim 7, wherein the means for electronically associating comprises means for accepting an address entered by an operator at an entry field displayed on the monitor, the address identifying a memory location in the programmable logic controller associated with the element.

9. The apparatus of claim 7, wherein the means for electronically associating comprises:

(i) means for accepting a designated key entered by an operator into the computer, and displaying a list of symbols used in the ladder logic program on the monitor in response thereto;

(ii) means for searching the list for a symbol representing a specific element in the ladder logic program; and

(iii) means for electronically associating the graphical object to the specific element.

10. The apparatus of claim 7, wherein the means for electronically associating comprises:

(i) means for accepting a designated key entered by the operator into the computer, and displaying the ladder logic program on the monitor in response thereto;

(ii) means for searching through the ladder logic program for a specific element; and

(iii) means for electronically associating the graphical object to the specific element.

11. An apparatus for monitoring a ladder logic program executing in a programmable logic controller, comprising:

(a) a computer, coupled to the programmable logic controller, having a monitor attached thereto, the computer further comprising;

(1) means for displaying a graphical object on the monitor to depict a plant process controlled by the programmable logic controller, the graphical object being electronically associated with an element of the ladder logic program, wherein the graphical object is selected from a group comprising Bargraph objects, Numeric objects, Trend objects, and State Change objects;

(2) means for initializing a polling interval on the computer for the graphical object, the polling interval indicating a waiting period before a value for the associated element is to be retrieved from the programmable logic controller;

(3) means for responding to a triggering of the polling interval by transmitting a query message from the computer to the programmable logic controller requesting a value for the associated element and by resetting the polling interval;

(4) means for responding to the value being input from the programmable logic controller to the computer by changing the display of the graphical object in accordance with a change in the value for the associated element; and

(5) means for responding to an entry of a hot-key command by an operator of the computer by accessing a "hot-key" data structure in the computer and extracting therefrom an electronically stored filename which identifies a location on the computer where a copy of the ladder logic program is stored, and displaying the copy of the ladder logic program on the monitor at a specific rung thereof.

12. The apparatus of claim 11, wherein the computer further comprises means for preventing unauthorized access to the copy of the ladder logic program.