GB2330667A - Circuit card for a Personal Computer emulates a Programmable Logic Controller - Google Patents

Circuit card for a Personal Computer emulates a Programmable Logic Controller Download PDF

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Publication number
GB2330667A
GB2330667A GB9720418A GB9720418A GB2330667A GB 2330667 A GB2330667 A GB 2330667A GB 9720418 A GB9720418 A GB 9720418A GB 9720418 A GB9720418 A GB 9720418A GB 2330667 A GB2330667 A GB 2330667A
Authority
GB
United Kingdom
Prior art keywords
circuit card
machine
circuit
interface
card
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9720418A
Other versions
GB9720418D0 (en
Inventor
Nicholas John Nelson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MICROSS ELECTRONICS Ltd
Original Assignee
MICROSS ELECTRONICS Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by MICROSS ELECTRONICS Ltd filed Critical MICROSS ELECTRONICS Ltd
Priority to GB9720418A priority Critical patent/GB2330667A/en
Publication of GB9720418D0 publication Critical patent/GB9720418D0/en
Publication of GB2330667A publication Critical patent/GB2330667A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/05—Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/10—Plc systems
    • G05B2219/15—Plc structure of the system
    • G05B2219/15101—Personal computer pc and plc, slot plc, same kernel

Abstract

Circuit card 8 for a Personal Computer (PC) 1 has all the attributes of a conventional Programmable Logic Controller so that the PC is able to control a machine 2. The circuit card comprises a processor 9, non-volatile memory 10, interface 11 with CPU 3 of the PC 1, and interface 12 with the machine 2. Circuit card 8 and PC 1 have separate power supplies 17, 16, such that the circuit card can operate independently of the PC. The circuit card is also preferably provided with: an interface circuit that monitors the operation of the PC, and disables the interface between the circuit card and the PC when the PC has been switched off or ceases to operate correctly; a "brownout" detection circuit that monitors the power supply to the circuit card and causes the machine to stop operating when the voltage falls to a level at which the card cannot function correctly; and a "watchdog" circuit which resets the circuit card if its program sequence is disrupted.

Description

A Circuit Card The present invention relates to a circuit card for a computer A circuit card is an electronic circuit which can be added to a computer, in particular to a Personal Computer (PC), to increase the computing power of the computer. A circuit card is often a circuit made up on a piece of printed circuit board, which is installed inside a PC Alternatively, the circuit card can be disposed outside the computer A Programmable Logic Controller (PLC) is a particular type of a computer which is adapted to control one or more machines. A PLC controlling a machine is connected, via a suitable interface, to sensors and actuators provided on the machine. It controls the machine through the actuators, on the basis of information received from the sensors and on the basis of its internal program A PLC also has an interface through which an operator can influence the operation of the PLC and the machine it is controlling.
A R PLC does not normally have a sophisticated display Often, a Personal Computer (PC) is used to provide the display and the operator interface A PC is generally less reliable than a PLC, but this is not too disadxantageous as the PC is not directly controlling the instantaneous operation of the machine - it just provides the operator interface, and possibly gives some form of status report on the machine's operation One example of the use of a PLC is a computer controlled milling machine In its simplest conceptual form the milling machine will haxe acrJators for causing translational movement of the milling head and an actuator for causing the milling head to rotate so as to mill materials It will also hae sensors for monitoring movement of the milling head In use, an operator will input dimensions of a desired product into a PLC controlling the milling machine, via a PC The PLC will control the movement of the milling head through the actuators, on the basis of the input dimensions and on the basis of the instantaneous position of the milling head as determined by the sensors.
The present invention provides a circuit card for a PC, the circuit card being adapted to emulate a PLC. In a preferred embodiment the circuit card comprises a processor, a first interface for interfacing with the processor unit of the PC, and a second interface for interfacing with a machine to be controlled The present invention also provides an apparatus for controlling a machine, wherein the apparatus comprises a PC having a circuit card as defined above.
Preferred features of the invention are set out in the dependent claims A preferred embodiment of the present invention will now be described by way of an illustrative example with reference to the accompanying drawings in which: Figure 1 is a schematic block diagram of a PC having a circuit card of the present invention Figure 1 shows a PC 1 set up to control a machine 2 The PC 1 is a standard conventional PC, and has a Central Processor Unit (CPU) 3. a Visual Display Unit (VDU) 4. a keyboard 5, a computer mouse 6, and a memory unit 7 The PC 115 provided with a circuit card 8 according to the invention. This has a processor 9. a memos 10, an input interface 11 for interfacing with the CPU 3 of the PC 1, and an output interface 12 The output interface enables the circuit card 8 to control the machine 2 In the embodiment of Figure 1, the machine 2 is a milling machine. It has actuators 13 for moving the milling head, and sensors 14 for detecting movement of the milling head The machine 2 is provided with an interface 15, which is connected to the output interface Il of the circuit card The operator will input details of the desired product into the PC 1, by using the keyboard 4 and, ; or the mouse 5. The input data is passed to the processor 9 of the circuit board 8 The processor 9 will control the movement of the milling head of the machine 3 via the actuators 13, using a program stored in the memory 10, and using data provided by the sensors 14 Once the processor 9 determines that the job is complete it will advise the CPU 3 of the PC 1. and the CPU 3 will cause an appropriate message to be displayed on the NU 4.
The circuit card of Figure 1 has two interfaces The output interface 12 - to interface with the machine to be controlled - is a field bus interface such as a Profibus or Interbus-S interface The input interface 11 (to interface with the PC) is a serial interface The memory 10 of the circuit card memory is a non-volatile memory - that is, stored data is not lost when the circuit card is switched off It is possible for the circuit card to be powered from the PC's power supply However, this has the disadvantage that the circuit card would be switched off if the PC's power supply failed, or even if the PC were switched off In the embodiment of Figure 1, therefore. the circuit card is not powered from the power supply 16 for the PC. The circuit card is poxBered by the same power supply 17 as is used to power the sensors and actuators provided on the machine. This makes the circuit card independent from the PC power supply The following features are found in conventional PLCs, and are preferably incorporated into a circuit card of the present invention so that the circuit card has all the attributes of a conventional PLC.
The circuit card preferably uses a relatively restricted programming language such as, for example, one conforming to the EC It 31 standard. The program steps in such a language are simple and they are rapidly executed. These languages are designed so that it is impossible to mis-write a program in such a way that the circuit card can "crash" 2. The circuit card is preferably provided with monitoring means to ensure that the machine and circuit card are functioning correctly. For example, a "brownout" detection circuit is provided to monitor the power supply to the circuit card. If the voltage falls to a level at which the circuit card will not correctly function, or at which the circuit card cannot drive the actuators on the machine, the circuit card will cause the machine to stop operating to prevent the machine or the circuit card from being damaged 3.. "watchdog" circuit is preferably provided This is an independent hardware device which resets the circuit card if its program sequence is disrupted. It consists of a timer which the program running in the circuit card periodically resets. If the sequence of the program running in the circuit card is disrupted, for example if an electromagnetic field exceeding the circuit cards immunity is generated in the vicinity of the circuit card, the watchdog circuit would not be reset at the expected time In this case, after a short time period, the watchdog circuit'times out" and resets the circuit card 4 Once the circuit card has started to run a program it is not possible to stop the program, except by the operator's intervention The circuit card preferably has an Electromagnetic Capability that exceeds the applicable regulatory requirements, so that it can be safely used in an industrial electrical environment In order to improve the reliability of the circuit card in controlling a machine, the circuit card is preferably able to run independently from the PC, so that a failure of the PC would not interrupt a program running in the circuit card In addition to the card being independent from the PC power supply, it is preferable that the circuit card is not affected by any of the following happening to the PC: a) termination of the program that interfaces the PC and the circuit card, b) a general protection fault in the PC, and c) termination of the operating system of the PC The circuit card is therefore preferably provided with an interface circuit that monitors the operation of the PC. \N'hen the circuit detects that the PC has been switched off, or that the PC has ceased to operate correctly. it will disable the interface between the PLC circuit card and the PC.
It will be apparent that the present invention is not limited to the embodiment described in detail above For example, although the embodiment relates to a milling machine the present invention can be used with any computer controlled machine

Claims (1)

  1. CL. \IN1S : A A circuit card for a personal computer (PC), the circuit card being adapted to emulate a Programmable Logic Controller.
    2. A circuit card as claimed in Claim l, wherein the circuit card comprises, a processor; a memory; a first interface for interfacing with the processor unit of the PC, and a second interface for interfacing with a machine to be controlled A R circuit card as claimed in Claim 2, wherein the memory is a non-volatile memory 4. A circuit card as claimed in Claim 2 or 3 and further comprising means for monitoring the supply voltage applied to the circuit card 5 A circuit card as claimed in Claim 2, 3 or 4 and further comprising first monitor means for monitoring the first interface.
    6. A circuit card as claimed in any of Claims 2 to 5 and further comprising second monitor means for monitoring the machine to be controlled 7. A circuit card substantially as described herein 8. An apparatus for controlling a machine, wherein the apparatus comprises a PC, the PC having a circuit card as defined in any preceding claim 9 .NTi apparatus as claimed in Claim s and further comprising a first power supply for supplying electrical power to the PC, and a second power supply for supplying electrical power to the circuit card.
    10 An apparatus as claimed in Claim 9, wherein the second power supply supplies electrical power to the machine to be controlled 11 An apparatus substantially as described herein
GB9720418A 1997-09-26 1997-09-26 Circuit card for a Personal Computer emulates a Programmable Logic Controller Withdrawn GB2330667A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9720418A GB2330667A (en) 1997-09-26 1997-09-26 Circuit card for a Personal Computer emulates a Programmable Logic Controller

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9720418A GB2330667A (en) 1997-09-26 1997-09-26 Circuit card for a Personal Computer emulates a Programmable Logic Controller

Publications (2)

Publication Number Publication Date
GB9720418D0 GB9720418D0 (en) 1997-11-26
GB2330667A true GB2330667A (en) 1999-04-28

Family

ID=10819635

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9720418A Withdrawn GB2330667A (en) 1997-09-26 1997-09-26 Circuit card for a Personal Computer emulates a Programmable Logic Controller

Country Status (1)

Country Link
GB (1) GB2330667A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1151681A2 (en) 2000-05-05 2001-11-07 Focke & Co. (GmbH & Co.) Apparatus for manufacturing products and method for controlling such an apparatus
FR2879314A1 (en) * 2004-12-09 2006-06-16 Chaveriat Robotique Soc Par Ac Product manufacturing line controlling device for e.g. product plastification industry, has data programming unit presented under form of software environment, and user interface to integrate environment and automaton
JP2007312573A (en) * 2006-05-19 2007-11-29 Omron Corp Io unit in safety controller of building block type
EP2104012A1 (en) * 2008-03-19 2009-09-23 Siemens Aktiengesellschaft Automation device with diagnosis functionality

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4683550A (en) * 1984-07-30 1987-07-28 Burr-Brown Corporation Personal computer instrumentation system including carrier board having bus-oriented plug-in instrumentation modules
US5317501A (en) * 1987-10-13 1994-05-31 Bernhard Hilpert Control system for a numerically controlled machine
EP0620512A1 (en) * 1992-10-26 1994-10-19 Fanuc Ltd. Numeric controller
EP0777167A1 (en) * 1995-06-19 1997-06-04 Fanuc Ltd. Numerical controller

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4683550A (en) * 1984-07-30 1987-07-28 Burr-Brown Corporation Personal computer instrumentation system including carrier board having bus-oriented plug-in instrumentation modules
US5317501A (en) * 1987-10-13 1994-05-31 Bernhard Hilpert Control system for a numerically controlled machine
EP0620512A1 (en) * 1992-10-26 1994-10-19 Fanuc Ltd. Numeric controller
EP0777167A1 (en) * 1995-06-19 1997-06-04 Fanuc Ltd. Numerical controller

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1151681A2 (en) 2000-05-05 2001-11-07 Focke & Co. (GmbH & Co.) Apparatus for manufacturing products and method for controlling such an apparatus
EP1151681B1 (en) * 2000-05-05 2007-07-18 Focke & Co. (GmbH & Co. KG) Apparatus for manufacturing products and method for controlling such an apparatus
FR2879314A1 (en) * 2004-12-09 2006-06-16 Chaveriat Robotique Soc Par Ac Product manufacturing line controlling device for e.g. product plastification industry, has data programming unit presented under form of software environment, and user interface to integrate environment and automaton
JP2007312573A (en) * 2006-05-19 2007-11-29 Omron Corp Io unit in safety controller of building block type
EP1857900A3 (en) * 2006-05-19 2010-03-03 Omron Corporation Safety controller and input-output unit therefor
US7783902B2 (en) 2006-05-19 2010-08-24 Omron Corporation Safety controller and input-output unit therefor
EP2104012A1 (en) * 2008-03-19 2009-09-23 Siemens Aktiengesellschaft Automation device with diagnosis functionality

Also Published As

Publication number Publication date
GB9720418D0 (en) 1997-11-26

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)