CA2064624A1 - Control system with diagnostic logic - Google Patents
Control system with diagnostic logicInfo
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- CA2064624A1 CA2064624A1 CA 2064624 CA2064624A CA2064624A1 CA 2064624 A1 CA2064624 A1 CA 2064624A1 CA 2064624 CA2064624 CA 2064624 CA 2064624 A CA2064624 A CA 2064624A CA 2064624 A1 CA2064624 A1 CA 2064624A1
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Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides an apparatus for con-trolling a machine having an error means for indicating an error condition in said machine, said error means comprising a first table containing a list of zone names and input/output image names; and a second table containing a plurality of error desig-nations wherein said error means formulates an error message indicative of said error condition. The present invention also provides a method for indicating an error condition of an appara-tus comprising the steps of looking up a zone name and an input/output image name; determining an error designation from a plurality of error designations indicative of said error condi-tion; combining said zone name, said input/output name, and said error designation into an error message; and displaying said error message.
The present invention provides an apparatus for con-trolling a machine having an error means for indicating an error condition in said machine, said error means comprising a first table containing a list of zone names and input/output image names; and a second table containing a plurality of error desig-nations wherein said error means formulates an error message indicative of said error condition. The present invention also provides a method for indicating an error condition of an appara-tus comprising the steps of looking up a zone name and an input/output image name; determining an error designation from a plurality of error designations indicative of said error condi-tion; combining said zone name, said input/output name, and said error designation into an error message; and displaying said error message.
Description
2 ~ 2 ~
The present invention relates to a control system and method utilizing logic devices to control apparatus and to diag-nose errors in the operation of the apparatus.
~his application is a divisional application of copend-ing application No. 512,905 filed July 21, 1986.
Machine control systems generally include an automatic mode of operation whereby the machine is automatically cycled through a work sequence. Relay ladder logic commonly has been used to define the machine sequences~ whether the logic is effected by relays or programmable controllers. The typical relay ladder logic diagram is a massive listing of relay, switch and solenoid conditions without an indication of logic flow which, while easy to read, is difficult to translate into the logic conditions intended to be represented. In addition, a large number of implied conditions exist that are not depicted.
For example, a relay ladder with twenty elements (switches~
relays, solenoids, etc.3 ~mbraces well over one million possible combinations of conditions. As a practical matter only a small fraction of these conditions, those necessary to make the system work, are considered by the machine designer and encoded into the logic scheme. Potential problems abound. Some planned condi-tions may be omikt0d, and unplanned conditions may be present with serious consequences.
The programmable controller (PC) was introduced with the hope that the massive racks of relays wired together in a permanent logic network could be replaced by a more reliable, smaller and readily reprogrammable electronic package. Although the PC was designed to replace relay controls, its design 3s 6 2 ~
explicitly set out to replicatev in the design media, the relay ladder logic used by technicians. Reprogrammability has proven to be a mixed blessing. Initial reprogramming is always needed as the system is set up and to meet product design change~.
Any change made to the program logic requires a corresponding modification to associated diagnostic programming so the latter can properly reflect errors in the altered logic. The ease of making changes can allow modification~ to be made by any semi-qualified person. Unfortunately, there is often no automatic record of changes made, and there is therefore the possibility that the documentation may not reflect the actual program. This is a sufficiently serious problem for many production facilities that they are investing heavily in add-on equipment to monitor program changes. Furthermore, the increase in number of Input/Output (I/O) points desired by users and consequent greater complexity of controls have driven PC manufacturers to push tbe PC design to larger and larger unit~. These very large units are well designed to meet the needs of central chemical plant control rooms, for example, but are too slow for the fast-cycle automation, such as transfer lines.
A significant cost of automated production lies in system "down-timen - i.e. time in which the automated system is non-productive_- which may range between 50~ and 60~ during productive shi~ts. Analyses show that there are many causes of down time including: many potential sources of unintended stoppage, variable delay~ in bringing the appropriate skills to bear on the problem, repair times that vary from minutes to hours, and a significant time needed to return the machine to a ~Iready for automatic cycle" condition after all repairs have been made. Downtime is a direct consequence of the high degree of complexity required to perform a large number of machining and part handling operations with the minimum of operator intervention. While lower equipment failure rates are a high priority objective~ it is widely believed that reducing time 2~
to return to production is the major area of opportunity for improvement.
The present invention is directed to a system and method for controllin~ operation of a plurality of elements in an automated process, such as a production process, and indicating error conditions as they occur. In accordance with the inven~
tion, each unique ~et of input and output conditions of the vari-ous system elements defines a unique logic state or zone. Thus, there are defined a multiplicity of valid system logic states or zones, each having a unique inputJoutput image. A predetermined sequence of zones, productive zones representing designed machine operations, is stored in a zone table. All zones not explicitly defined in the zone table are automatically treated as error zones. An MPU automatically cycles to observe any change in input/output image. Any change in inputs from the various system elements automatically transfer action to the unique zone associ-ated with such inputs, resulting in corresponding changes in con-trol outputs to the system elements and/or display of an error message as appropriate.
A preferred embodiment of the present invention includes a control system with a logic device such as a micropro-cessing unit for scanning inputs from system sensing elements, such as limit switches or digitally coded signals, and generating outputs to system elements such as electric motors or indicator lamps. Control action is taken according to the input conditions that define a logic zone. A predetermined sequence of logic zones representing machine operating steps is created and stored in a zone table in the microprocessing unit. Any zone that is not defined explicitly in the table is automatically defined as a fault, and operation is logically vectored to a specific error zone in the zone table. Each new set of input and output condi-tions is compared with the zone 2~6~2~
table in the microprocessing unit, and if a mismatch is detected, or if a time in a specific zone is outslde the predetermined time limits for that zone, predetermined action is effected (usually stop the machine).
. In accordance with another feature of the inventlon for automatic generation of error messages, each logic zone and each input/output image has associated therewith a verbal description according to its function. Motion or action zones have associ-ated verbs pha~es, such as "drill sllde moving forward" and inputand output (I/O~ elements are named with nouns such as n forward limit switch", etc. The system continually examines the actions taking place or the lack of actlon, and the conditions of the system elements. When a fault occurs, i.e. when the combination of action and e:Lement conditions does not represent a productlve situation, the names of the zones and inputs and outputs are com-bined to automatically compose a unique readily understood error message complete with verbs, nouns and ob~ects in accordance with standard language construction. If the system is changed by the designer, the diagnostics and error message compositlon automati-cally follow with no additional programming. The system will automatically compose its own unique error messag~ in accordancP
with the changes.
According to one aspert of the present invention thPre-fore there is provided a machine control system which comprises, in combination, a machine lncluding means for producing motion at said machine and means for sensing machine condition, and control means responsive to a predeflned input from said condition-sens-ing means for providing a predefined output to said motion-pro-ducing means, said control means comprising: means for tabulating said predefined input and output ln a combination representative of a preselected set of operations of said machine, ~ach sa~d combination representing an input~output image indicativ~ of a corresponding zone having associated therewith an allowed next zone with at least one of said corresponding zones having associ-, 2~6~6~
ated therewith a plurality of allowed next zones; means for monitoring said predetermined input and output responslve to a change in said predetermined input and output to formulate a new input/output image; means for comparing said new input~output image to an lnputJoutput image in said tabulating means indica-tiv~ of the allowed next zone; and means for lndicating an error condition in the event that said new input~output image does not match that of said next zone in said preselected set. Suitably said tabulating means includes means for establishing operating lo times in each zone in said preselected set; wherein said compris-lng means includes means for measuring time of operatlon withln a zone in said preselected set aad means for comparlng said time of operation to said established tlmes; and said error-indicating means lncludes means for indicating sald error condition in response to a change in said predetermined input and output when said time of operation in said zone is outslde of said estab-lished times.
In one embodiment of the present invention said error-condition indicatlng means includes means for providing an error signal indicative of an input and output condition at said machine upon detection of an error condltion, and means respon-sive to said error signal for formulating and displaying an error message indicative of said error condition. Suitably message-formulating means includes a table of predefined error messagesegments corresponding to an error condition at said machine, and means responsive to said error signal for gather~ng error message segm~nts from said table as a function of sald error signal and thereby formulating said error message. Desirably sald error signal-providing means includes means for providlng said error signal as a series of binary signals ln predetermined sequence corresponding to input and output conditions at said machine, and wherein said message-formulating means includes means responsive to each binary signal ln said error slgnal to obtain a corre-sponding error mPssage segment from said error message table,sequence of said error message segments in said error message - 4a -2~6~6~'~
corresponding to sequence of sald binary signals in said error signal. Suitably said error message-displaying means comprises a visual displayO
In another aspect thereof the present invention pro-vides a method of operating a machine capable of performing a plurality of physical operations whereln said machine is con-trolled through input and output devires, said method comprlslng the steps of: establishing a set of machine operations defined by a set of operating zones, each zone of said operatlng zones hav-ing a corresponding lnput/output image of lnput and output from said input and output devices and each zone having a correspond-ing allowed next zone with at least one of said operating zones havl~g a plurality of allowed next zones monitoring inputs and outputs from sald input and output devices durlng a step in said plurallty of physical operations and comparing input/output image associated with said step; advancing machlne operation to a next step in said set of machine operations ~hen a change in said inputs and outputs produces a zone lmage corresponding to said allowed next zone; and indicating an error condition when a change in said inputs and outputs procluces a~ input/output image other than that corresponding to said allowed next zone. Suit-ably the method comprises the additional steps of: monitor~ng a time of operation in each zone of saicl operating zo~es; comparing said time of operation in a particular zone to a predetermined time associated with said operating zone; and indicating said error condition when said time of operation i~ greater than said predetermlned time. Deslrably the method comprlses the addi-tional steps of: storing a plurallty of predetermined message segments ln plan text corresponding to actions to be taken ln said operating æones and input and output conditions at said machins; establishing an error slgnal ~n response to an indica-tion of said error condition, said error slgnal including seg-ments reflecting input and output conditions at said machine in predetermined sequence upon detection of said error condltion;
composing an error message as a sequence of said predetermined ..
- 4b -2 ~
message segments corresponding to and in the order of said error signal segments; and displayiny said error message.
In a still further aspect of the present invention there is provided an apparatus for controlling a machine compris-ing:, memory means for storing at least two inputJoutput images, each lnput/output image having assoclated therewith a present zone and an allowed next zone with at least one input/output image havlng associated therewith a plurality of allowed ne~t zones; monitorln~ means for receiving an input re~uiring a change in a present input/output image to a new input/output image;
means for compar~ng an input/output image of said allowed next zone with said new input~output image; means for executing sald input and for replacing said present input/output imag~ with said lnput/output lmage of said allowed next zone if said new ~nputJoutput image matches said allowed next zone; and means for indicating an error condition when said new input/output image ~oes not match said input/output image of said allowed next zone.
Suitably the apparatus comprises timing means for measuring a duration of time in said present æone wherein said apparatus moves to a specified allowed next zone when said duration exceeds a predetermined duration for said present ~one. Desirably the apparatus further compr~ses interference inhibit means for lnhibiting said execution means when execution could interfere with a current zone of a second apparatus. Suitably the appara-tus further comprises part process means for lnhibiting said ~xe-cution means when a part process record of a workpiece to be worked on by said apparatus indicates said workpiece is not pre-pared for an operation to be performed. Pr ferably said error means comprises: a flrst table containing an identification of said apparatus; a second table containing a zone name of said present zone; a third table containin~ an input/output name of said input/output image; a fourth table containing a current sta-tus of said present zone; and a flfth table containlng a plural-ity of error designations wherein said error indicating meansformulates an error message indicative of said error condition.
2~$~6~4 In another aspect thereof the present invention pro-vldes a method for controlling a machine having a present zone, an input/output image of said present zone, and at least two allowed next zones, wherein said method comprlses the steps of:
receiving an input representative of a new in~ut~output image of said machine; comparing an input/output image of a flrst allowed next zone of sa1d at least two allowed next zones with said new input~output image; changing said present zone to said first allowed next zone if said input/output image of said first allowed next zone matches said new input/output image; and com-paring an 1nput/output image of a second allowed next zone of said at least two allowed next zones with said new input/output image if said new input/output image did not match said input/output image of said first allowed next zone.
In a further aspect thereof the present invention pro-vld~s a method for controlling a machlne havlng a present zone, an input/output image of said present zone, and a plurality of allowed next zones, wherein said method comprises the steps of:
(a) receiving an input representative of a new input/output image of said image; (b) comparing an input/output image of a particu-lar allowed next zone of said plurality of allowed next zones with said new input/output lmage; ~c) changlng said present zone of said machine to said particular allowed next zone if said input/output image of said particular allow~d next zone matches said new input/output image; and (d) repeating steps (b) and (c7 if sald input/output image of sa~d particular allowed next zone does not match said new input/output image until all of said plurality of allowed next zones have been compared to said new input/output image.
In another aspect thereof the present invention pro-vides an apparatus for controlllng a machina comprising: a flrst memory means for storing a present ~one of sald machlne; a second memory means for storlng an input/output image associated with said present zone of said machine; and a thlrd memory means for - 4d -2 ~
storing a plurality of allowed next zones associated with sald present zone of said machine. Suitably the apparat~s ~urther comprises a fourth memory means for storing a part processing tnhibit table. Desirably the apparatus further comprises a flfth memory means for storing an interface inhibit table.
In another aspect thereof the present invention pro-vides an apparatus for controlling a machine having an error means for indicating an error condition in said machine, said error means comprising: a first table containing a list of zone names and input/output image names; and a second table containing a plurality of error designations wherein said error means formu-lates an error messa~e indicative of said error condition.
The present invention further provides a method for indlcating an error condition of an apparatus comprising the steps of: looking up a zone name and an input/output image name;
determining an error designatlon from a plurality of error desig-nations indicative of said error condition; combining said zone name, said input/output name, and said error designation into an error message; and displaying said error message.
The present inventlon again provides a distributed logic control system comprising: a plurality of statlons each having means for controlling the operation of sald station, said controlllng means comprising station memory havlng a zone table of present zones, input/output images, and allowed next zones;
orchestrator means for monitoring and controlling the operation o~ said plurality of stations; and communication means for cou-pling said plurality of stations to said orchestrator means.Suitably said controlling means comprises: station memory means for storing station information; input/output link means for cou-pllng said station memory means to said communication means; and means for controlling the operation of a mechanism of said sta-tion, said mechanism control means coupling said mechanism tosaid station memory means. Preferably said controlling means - 4e -2 ~ 2 ~
further comprises: output means for providing output signals from said station memory means to an ex~ernal device; input means for providing input signals from a station device and to said station memory means; and logic means for controlling the operation of said station, said logic means being coupled to said station mem-ory means. Suitably said lnput/output link means, mechanism con-trol means, output means, inp~t means, and logic means are micro-processor units, and said system further comprises memory con-tention means coupled between said station memory means and said microprocessor units for controlling access to said station mem-ory means. Desirably said station memory comprises: a machine memory having an lnterference table and a part processing record;
and a statlon memory havlng a time-in-zone memory, and a station ~ournal.
The present invention also provides a method for con-trolling a machlne comprising the steps of: identifying a first mechanism of said machine; storing a plurality of valid zones of said first mechanism in a controller of sald machlne; and storing an allowed next zone for each said va~id zone in said controller of said machine, wherein at least one said valid zone has a plu-rallty of allowed next zones. Suitably the method comprises the steps of: storin~ a zone of a second mechanism wherein said zone of said second mechanism could interfere with at least one of said plurality of valid zones of said first mechanism; and stor-ing a part process descriptlon of work re~uired to be performed at a previous machine.
The present invention will be further illustrated by way of the accompanying drawings, ln which:-Flgure 1 is a schematic view showing a drllling machineoperated with the control system of the present invention, Figure 2 is a schematic diagram which deplcts possible zones in operation of the machine slide of Fig. 1 and illustrates - 4~ -2 ~
operation of the invention;
Figure 3 is a diagram depicting exemplary devices which : produce inputs to the system control lsgic;
Figure 4 is a diagram depicting outputs from the con-trol logic to actuate various machine mechanisms;
The present invention relates to a control system and method utilizing logic devices to control apparatus and to diag-nose errors in the operation of the apparatus.
~his application is a divisional application of copend-ing application No. 512,905 filed July 21, 1986.
Machine control systems generally include an automatic mode of operation whereby the machine is automatically cycled through a work sequence. Relay ladder logic commonly has been used to define the machine sequences~ whether the logic is effected by relays or programmable controllers. The typical relay ladder logic diagram is a massive listing of relay, switch and solenoid conditions without an indication of logic flow which, while easy to read, is difficult to translate into the logic conditions intended to be represented. In addition, a large number of implied conditions exist that are not depicted.
For example, a relay ladder with twenty elements (switches~
relays, solenoids, etc.3 ~mbraces well over one million possible combinations of conditions. As a practical matter only a small fraction of these conditions, those necessary to make the system work, are considered by the machine designer and encoded into the logic scheme. Potential problems abound. Some planned condi-tions may be omikt0d, and unplanned conditions may be present with serious consequences.
The programmable controller (PC) was introduced with the hope that the massive racks of relays wired together in a permanent logic network could be replaced by a more reliable, smaller and readily reprogrammable electronic package. Although the PC was designed to replace relay controls, its design 3s 6 2 ~
explicitly set out to replicatev in the design media, the relay ladder logic used by technicians. Reprogrammability has proven to be a mixed blessing. Initial reprogramming is always needed as the system is set up and to meet product design change~.
Any change made to the program logic requires a corresponding modification to associated diagnostic programming so the latter can properly reflect errors in the altered logic. The ease of making changes can allow modification~ to be made by any semi-qualified person. Unfortunately, there is often no automatic record of changes made, and there is therefore the possibility that the documentation may not reflect the actual program. This is a sufficiently serious problem for many production facilities that they are investing heavily in add-on equipment to monitor program changes. Furthermore, the increase in number of Input/Output (I/O) points desired by users and consequent greater complexity of controls have driven PC manufacturers to push tbe PC design to larger and larger unit~. These very large units are well designed to meet the needs of central chemical plant control rooms, for example, but are too slow for the fast-cycle automation, such as transfer lines.
A significant cost of automated production lies in system "down-timen - i.e. time in which the automated system is non-productive_- which may range between 50~ and 60~ during productive shi~ts. Analyses show that there are many causes of down time including: many potential sources of unintended stoppage, variable delay~ in bringing the appropriate skills to bear on the problem, repair times that vary from minutes to hours, and a significant time needed to return the machine to a ~Iready for automatic cycle" condition after all repairs have been made. Downtime is a direct consequence of the high degree of complexity required to perform a large number of machining and part handling operations with the minimum of operator intervention. While lower equipment failure rates are a high priority objective~ it is widely believed that reducing time 2~
to return to production is the major area of opportunity for improvement.
The present invention is directed to a system and method for controllin~ operation of a plurality of elements in an automated process, such as a production process, and indicating error conditions as they occur. In accordance with the inven~
tion, each unique ~et of input and output conditions of the vari-ous system elements defines a unique logic state or zone. Thus, there are defined a multiplicity of valid system logic states or zones, each having a unique inputJoutput image. A predetermined sequence of zones, productive zones representing designed machine operations, is stored in a zone table. All zones not explicitly defined in the zone table are automatically treated as error zones. An MPU automatically cycles to observe any change in input/output image. Any change in inputs from the various system elements automatically transfer action to the unique zone associ-ated with such inputs, resulting in corresponding changes in con-trol outputs to the system elements and/or display of an error message as appropriate.
A preferred embodiment of the present invention includes a control system with a logic device such as a micropro-cessing unit for scanning inputs from system sensing elements, such as limit switches or digitally coded signals, and generating outputs to system elements such as electric motors or indicator lamps. Control action is taken according to the input conditions that define a logic zone. A predetermined sequence of logic zones representing machine operating steps is created and stored in a zone table in the microprocessing unit. Any zone that is not defined explicitly in the table is automatically defined as a fault, and operation is logically vectored to a specific error zone in the zone table. Each new set of input and output condi-tions is compared with the zone 2~6~2~
table in the microprocessing unit, and if a mismatch is detected, or if a time in a specific zone is outslde the predetermined time limits for that zone, predetermined action is effected (usually stop the machine).
. In accordance with another feature of the inventlon for automatic generation of error messages, each logic zone and each input/output image has associated therewith a verbal description according to its function. Motion or action zones have associ-ated verbs pha~es, such as "drill sllde moving forward" and inputand output (I/O~ elements are named with nouns such as n forward limit switch", etc. The system continually examines the actions taking place or the lack of actlon, and the conditions of the system elements. When a fault occurs, i.e. when the combination of action and e:Lement conditions does not represent a productlve situation, the names of the zones and inputs and outputs are com-bined to automatically compose a unique readily understood error message complete with verbs, nouns and ob~ects in accordance with standard language construction. If the system is changed by the designer, the diagnostics and error message compositlon automati-cally follow with no additional programming. The system will automatically compose its own unique error messag~ in accordancP
with the changes.
According to one aspert of the present invention thPre-fore there is provided a machine control system which comprises, in combination, a machine lncluding means for producing motion at said machine and means for sensing machine condition, and control means responsive to a predeflned input from said condition-sens-ing means for providing a predefined output to said motion-pro-ducing means, said control means comprising: means for tabulating said predefined input and output ln a combination representative of a preselected set of operations of said machine, ~ach sa~d combination representing an input~output image indicativ~ of a corresponding zone having associated therewith an allowed next zone with at least one of said corresponding zones having associ-, 2~6~6~
ated therewith a plurality of allowed next zones; means for monitoring said predetermined input and output responslve to a change in said predetermined input and output to formulate a new input/output image; means for comparing said new input~output image to an lnputJoutput image in said tabulating means indica-tiv~ of the allowed next zone; and means for lndicating an error condition in the event that said new input~output image does not match that of said next zone in said preselected set. Suitably said tabulating means includes means for establishing operating lo times in each zone in said preselected set; wherein said compris-lng means includes means for measuring time of operatlon withln a zone in said preselected set aad means for comparlng said time of operation to said established tlmes; and said error-indicating means lncludes means for indicating sald error condition in response to a change in said predetermined input and output when said time of operation in said zone is outslde of said estab-lished times.
In one embodiment of the present invention said error-condition indicatlng means includes means for providing an error signal indicative of an input and output condition at said machine upon detection of an error condltion, and means respon-sive to said error signal for formulating and displaying an error message indicative of said error condition. Suitably message-formulating means includes a table of predefined error messagesegments corresponding to an error condition at said machine, and means responsive to said error signal for gather~ng error message segm~nts from said table as a function of sald error signal and thereby formulating said error message. Desirably sald error signal-providing means includes means for providlng said error signal as a series of binary signals ln predetermined sequence corresponding to input and output conditions at said machine, and wherein said message-formulating means includes means responsive to each binary signal ln said error slgnal to obtain a corre-sponding error mPssage segment from said error message table,sequence of said error message segments in said error message - 4a -2~6~6~'~
corresponding to sequence of sald binary signals in said error signal. Suitably said error message-displaying means comprises a visual displayO
In another aspect thereof the present invention pro-vides a method of operating a machine capable of performing a plurality of physical operations whereln said machine is con-trolled through input and output devires, said method comprlslng the steps of: establishing a set of machine operations defined by a set of operating zones, each zone of said operatlng zones hav-ing a corresponding lnput/output image of lnput and output from said input and output devices and each zone having a correspond-ing allowed next zone with at least one of said operating zones havl~g a plurality of allowed next zones monitoring inputs and outputs from sald input and output devices durlng a step in said plurallty of physical operations and comparing input/output image associated with said step; advancing machlne operation to a next step in said set of machine operations ~hen a change in said inputs and outputs produces a zone lmage corresponding to said allowed next zone; and indicating an error condition when a change in said inputs and outputs procluces a~ input/output image other than that corresponding to said allowed next zone. Suit-ably the method comprises the additional steps of: monitor~ng a time of operation in each zone of saicl operating zo~es; comparing said time of operation in a particular zone to a predetermined time associated with said operating zone; and indicating said error condition when said time of operation i~ greater than said predetermlned time. Deslrably the method comprlses the addi-tional steps of: storing a plurallty of predetermined message segments ln plan text corresponding to actions to be taken ln said operating æones and input and output conditions at said machins; establishing an error slgnal ~n response to an indica-tion of said error condition, said error slgnal including seg-ments reflecting input and output conditions at said machine in predetermined sequence upon detection of said error condltion;
composing an error message as a sequence of said predetermined ..
- 4b -2 ~
message segments corresponding to and in the order of said error signal segments; and displayiny said error message.
In a still further aspect of the present invention there is provided an apparatus for controlling a machine compris-ing:, memory means for storing at least two inputJoutput images, each lnput/output image having assoclated therewith a present zone and an allowed next zone with at least one input/output image havlng associated therewith a plurality of allowed ne~t zones; monitorln~ means for receiving an input re~uiring a change in a present input/output image to a new input/output image;
means for compar~ng an input/output image of said allowed next zone with said new input~output image; means for executing sald input and for replacing said present input/output imag~ with said lnput/output lmage of said allowed next zone if said new ~nputJoutput image matches said allowed next zone; and means for indicating an error condition when said new input/output image ~oes not match said input/output image of said allowed next zone.
Suitably the apparatus comprises timing means for measuring a duration of time in said present æone wherein said apparatus moves to a specified allowed next zone when said duration exceeds a predetermined duration for said present ~one. Desirably the apparatus further compr~ses interference inhibit means for lnhibiting said execution means when execution could interfere with a current zone of a second apparatus. Suitably the appara-tus further comprises part process means for lnhibiting said ~xe-cution means when a part process record of a workpiece to be worked on by said apparatus indicates said workpiece is not pre-pared for an operation to be performed. Pr ferably said error means comprises: a flrst table containing an identification of said apparatus; a second table containing a zone name of said present zone; a third table containin~ an input/output name of said input/output image; a fourth table containing a current sta-tus of said present zone; and a flfth table containlng a plural-ity of error designations wherein said error indicating meansformulates an error message indicative of said error condition.
2~$~6~4 In another aspect thereof the present invention pro-vldes a method for controlling a machine having a present zone, an input/output image of said present zone, and at least two allowed next zones, wherein said method comprlses the steps of:
receiving an input representative of a new in~ut~output image of said machine; comparing an input/output image of a flrst allowed next zone of sa1d at least two allowed next zones with said new input~output image; changing said present zone to said first allowed next zone if said input/output image of said first allowed next zone matches said new input/output image; and com-paring an 1nput/output image of a second allowed next zone of said at least two allowed next zones with said new input/output image if said new input/output image did not match said input/output image of said first allowed next zone.
In a further aspect thereof the present invention pro-vld~s a method for controlling a machlne havlng a present zone, an input/output image of said present zone, and a plurality of allowed next zones, wherein said method comprises the steps of:
(a) receiving an input representative of a new input/output image of said image; (b) comparing an input/output image of a particu-lar allowed next zone of said plurality of allowed next zones with said new input/output lmage; ~c) changlng said present zone of said machine to said particular allowed next zone if said input/output image of said particular allow~d next zone matches said new input/output image; and (d) repeating steps (b) and (c7 if sald input/output image of sa~d particular allowed next zone does not match said new input/output image until all of said plurality of allowed next zones have been compared to said new input/output image.
In another aspect thereof the present invention pro-vides an apparatus for controlllng a machina comprising: a flrst memory means for storing a present ~one of sald machlne; a second memory means for storlng an input/output image associated with said present zone of said machine; and a thlrd memory means for - 4d -2 ~
storing a plurality of allowed next zones associated with sald present zone of said machine. Suitably the apparat~s ~urther comprises a fourth memory means for storing a part processing tnhibit table. Desirably the apparatus further comprises a flfth memory means for storing an interface inhibit table.
In another aspect thereof the present invention pro-vides an apparatus for controlling a machine having an error means for indicating an error condition in said machine, said error means comprising: a first table containing a list of zone names and input/output image names; and a second table containing a plurality of error designations wherein said error means formu-lates an error messa~e indicative of said error condition.
The present invention further provides a method for indlcating an error condition of an apparatus comprising the steps of: looking up a zone name and an input/output image name;
determining an error designatlon from a plurality of error desig-nations indicative of said error condition; combining said zone name, said input/output name, and said error designation into an error message; and displaying said error message.
The present inventlon again provides a distributed logic control system comprising: a plurality of statlons each having means for controlling the operation of sald station, said controlllng means comprising station memory havlng a zone table of present zones, input/output images, and allowed next zones;
orchestrator means for monitoring and controlling the operation o~ said plurality of stations; and communication means for cou-pling said plurality of stations to said orchestrator means.Suitably said controlling means comprises: station memory means for storing station information; input/output link means for cou-pllng said station memory means to said communication means; and means for controlling the operation of a mechanism of said sta-tion, said mechanism control means coupling said mechanism tosaid station memory means. Preferably said controlling means - 4e -2 ~ 2 ~
further comprises: output means for providing output signals from said station memory means to an ex~ernal device; input means for providing input signals from a station device and to said station memory means; and logic means for controlling the operation of said station, said logic means being coupled to said station mem-ory means. Suitably said lnput/output link means, mechanism con-trol means, output means, inp~t means, and logic means are micro-processor units, and said system further comprises memory con-tention means coupled between said station memory means and said microprocessor units for controlling access to said station mem-ory means. Desirably said station memory comprises: a machine memory having an lnterference table and a part processing record;
and a statlon memory havlng a time-in-zone memory, and a station ~ournal.
The present invention also provides a method for con-trolling a machlne comprising the steps of: identifying a first mechanism of said machine; storing a plurality of valid zones of said first mechanism in a controller of sald machlne; and storing an allowed next zone for each said va~id zone in said controller of said machine, wherein at least one said valid zone has a plu-rallty of allowed next zones. Suitably the method comprises the steps of: storin~ a zone of a second mechanism wherein said zone of said second mechanism could interfere with at least one of said plurality of valid zones of said first mechanism; and stor-ing a part process descriptlon of work re~uired to be performed at a previous machine.
The present invention will be further illustrated by way of the accompanying drawings, ln which:-Flgure 1 is a schematic view showing a drllling machineoperated with the control system of the present invention, Figure 2 is a schematic diagram which deplcts possible zones in operation of the machine slide of Fig. 1 and illustrates - 4~ -2 ~
operation of the invention;
Figure 3 is a diagram depicting exemplary devices which : produce inputs to the system control lsgic;
Figure 4 is a diagram depicting outputs from the con-trol logic to actuate various machine mechanisms;
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Figure 5 is a pictorial ~iew showing the sequence of zones in FIGo 2 with the positions of the limit switches and the conditions of the motion power indicated. Each zone image is read as a vertical slice in the viewO
Figure 6 is a diagrammatic view of Zone 1 in FIG5. 2 and 5 showing upcoming zone possibilities when the machine completes its function in the current zone.
Figure 7 is a diagrammatic view showing sixteen possible zone images with four system elements (two switches and two motor conditions). The zone images are read as vertical slices in the view~
Figure 8 is a fragmentary block diagram of the station computer.
Figure 9 is a schematic diagram and flow chart demonstrating the operation of the system.
Figure 10 is a schematic diagxam of an orchestrater computer and a station computer connlected in a communication loop with the orchestrater computer presenting error messages on a computer terminal CRT.
Figures 11-16 are pictorial illustrations of zone logic tables for a more complex machine system.
Figure 17 shows the algoritbm used to produce diagnostic messages in the system of the present invention.
Brackets indicate variables and a block indicates a fixed word.
Figure 18 shows a portion of a CRT screen presenting an errormessage generated by the system of the present invention.
Figure 19 shows a portion of an Input/Output table present in the command interpreter of the systemO
petailed Descri~tion The term "mechanism" as used herein is defined to mean a device that produces motion, such as a slide drive motor, a spindle motor or a clamp solenoid valve and cylinder as shown in Figure 4. "Inputs" sense mechanism conditions and send --S~
electrical signals to a logic control device. Examples are limit switches, digital coded signals and sensing devices such as shown in Figure 3. "Outputs" are generat~d by a control logic device and actuate mechanisms as illustrated in Figure 4. The control logic device drives outputs in accordance with the condition~ specified in the zone tables as described hereinafter. The following explanation involves a simple drilling machine that automatically moves a rotating drill against a workpiece to drill a hole, withdraws the drill, and returns back to the starting position. The cycle is automatically repeated. It will be appreciated that this relatively simple application of the invention is by way of example only.
Referring to Figure 1, the drillingmachine 10 includes a base 12 with a reversible electric motor 16 mounted thereon.
Motor 16 has an output shaft 18 coupled through a geared transmission 22 to drive a worm shaft 24. A machine slide 26 is slidably mounted on base 12 in engagement with worm shaft 24.
A drill head 28 rotates a drill bit 30 for drilling a hole in a workpiece (not shown). Limit switches 32 and 34 are positioned on machine base 12, and fingers 36 and 38 on slide 26 engage limit switches 32, 34 at the extreme limits of travel of the machine slide. Limit switches 32, 34 are connected to a station computer 40. Motor 16 is powered by a motor controller 54 which provides a feedback signal indicative of motor operation.
Controller 54 is coupled to station computer 400 Computer 40 is also connected to a communication loop 41 that contains an orchestrater computer 72.
The general operation of machine 10 requires slide 26 to move off returned limit switch 32 by energizing motor 16 to rotate lead screw 24 and move slide 26 forward until finger 38 engages advanced limit switch 34. At this point motor 16 must be stopped and energized to rotate lead screw 24 in the opposite direction for reversing the direction of travel of machine slide 26 until finger 36 engages limit switch 32. Again _. ~
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motor 16 is energized to move the slide in the advance direction, and so on in continuous cycling. Th~ current in the motor starter coil from line 48 to is sensed in conventional fashion and is fed back to microprocessor 40 to reflect the condition of the motor 16~ The condition of the motor starter coil is continually sensed so that the output is confirmed while the current is present.
A control panel 45 is connected to station computer 40 and includes push buttons 47 that indicate functions such as nstart drill motor~ r "advance slide", "single step", nstop drill motor", "return slide~, "automatic" and "manual". Push button logic 51 couples control panel 45 to stator computer 40.
A xelay 52 is connected to station computer 40 to shut down machine 10 if an error is detected.
Referring to Figure 2, the "zones" of operation o~
drilling machine 10 are represented . In Zone No. 1, machine slide 26 is ADVANCING OFF returned limit switch 3~. Zone No.
2 represents the drilling machine slide 26 ADVANCING BETWEEN
the limit switches~ Zone No. 3 represents drilling machine slide 26 ADVANCED FROM returned limit switch 32 and engaging advanced limit switch 34. Zone No. 4 represents machine slide 26 in ADVANCED position and with slide motor 16 stopped. Zone No. 5 represents machine slide 26 R~TURNING OFF advanced limit switch 34. Zone No. 6 represents machine slide 26 RETURNING
BETWEEN the limit switches. Zone No. 7 represents machine slide 26 RET~RNING FROM advanced limit switch 34 and engaging the returned limit switch 32. Zone 8 represents machine slide 26 RETURNED and motor 16 stopped. Zone No. 0 represents machine ~lide 26 stopped between limits. As will become apparent from the following discussion, zone description in upper case letters in the preceeding discussion is important in com~osing error messages. ~
Figure 5 is a pictorial view showing the zone patterns.
The eight possible inputs and eight possible outputs are - : -.
~. , 2 ~
illustrated7 Theblack or filled blocks represent power ~output~or switch (input) "on" and a blank block represent power or switch "off". For example, in Zone 1, input to the station computer 40 is limit switch 32 "on" and limit switch 34 "off".
The outpu~ from the station computer causes motor controller 54 and motor 16 to move the machine slide in either the advance or return direction. Again, in Zone 1, motor 16 is ~on" in the advance direction and "of" in the return airection. Vertical slices through the diagram in Figure 5 represent "images" of each of the nine productive zones.
Figure 6 is a pictorial view s~owing the mechanism operating in Zone 1. Any change in input or output causes a zone change. Figure 6 demonstrates that the only productive operating zone to follow Zone 1 is Zone 2. Any other zone is undefined in the zone table of FIG. 7, and therefore is interrupted as in error zone. All the possible combinations of conditions do not have to be anticipated because the system operating zones have been constrained during programming to those planned~ For purposes of explanation, those zones relative to the planned operation steps o~ the machine during error free operation, have been defined as "productive zones". Only the productive zones need to be considered. For example, if the _inputs 5hoW both limit switches 32 and 34 "on", this i~
automatically an error zone because such conditions are not present in the programmed zones ~FIG. 5)~ The various combinations can be quickly entered into a zone logic table by defining all productive zones plus at least one error zone.
The error zone may issue a shut down signal to-the system. With two limit switches and two motor directions r there are only sixteen possible physical combinations, as shown in Figure 7.
The number of possible combinations is two (on/off) mathematically taken to the power of the number of on-of~ devices present.
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~igure 8 is a block diagram of station computer 40. A
block of RAM 58 includes I/O memory, timer memory 64, zone data table memory 6~, and ~recorder~ and journal memories 68.70. Sta-tion computer 40 includes an MPU 42 which communicates with mem-ory 58 via the address bus 59 and the data bus 60. The program for executlng station operation is stored in command interpreter EPROM 61. An oscillator 62 supplies the clock function. MPU 42 executes the program in EPROM 61 and carries out the system func-tions shown in Figure 5 Upon entry into a new zone, MPU 42 takes the following action: write the new zone number and related information to recorder memory 68, set an internal zone timer to zero, and set the physical outputs as indicated by the zone table. For exam-ple, upon entry into Zone 1 (Fig. 5), MPU 42 energizes in the advance direction. MPU then continues to motor the I~O image from and to limit switches 32,3~, monitor controller 54 and motor 60, and to compare this information to the zone image in Zone 1.
I~ the event of a change of I/O indicia, MPU 42 automatically steps to the appropriate zone reflecting the new I~O image, l.e.
; zone 2 in the event of proper operation (Fig. 6), or an error zone if the latter is appropriate. In the event of proper opera-tion, the entire cycle repeats continuously.
Timer memory 64 checks the time in zone against minimum and maximum times for that zone stored in zone data table 66.
Recorder memory Ç8 records the history of zones over a number of zone changes, such as one thousand zone changes for example, and continually overwrites this data to reflect the last one thousand zone changes. This data is use~ul in analysis of an error, e.g.
to determine that the machine has been slowly deteriorating.
Journal memory 709 records error information continually from start-up of the system. A user can examine error history in pre-vious months or years. A copy of the journal or recorder can be sent to the screen of terminal 69, or .
a hard copy can be produced at printer 71 in accordance with the program in EPROM ~1.
~ igure 9 demonstrates operation of the system for drill station 10, including the zone timer as logic "inputs", for Zones 1-4 and 99~ ~he outputs SLID~ MOTOR ADVANCE and SLIDE
MOTOR RETURN, and the inputs SLIDE RETURNE~ LIMIT SWITCH and SLIDE ADVANCED LIMIT SWITCH are listed along the top, along with MINIMUM TIME IN ZONE and MAXIMUM TIME IN ZONE. The zone .~unctions are listed along the left side, with the zone n~mbers beside the function names~ One zone function is identified as ERROR Zone 99. The zon~ image for each of the operating zones is presented.in a horizontal slice of the chart next to the zone name and number. The hatched lines indicate which inputs and which outputs are turned "on" (hatched) and "off" ~unhatched~
in each zone. For example, in Zone 1, the SLIDE MOTOR ADVANCE
output and the RETURNED LIMIT S~ITCH input are "on". Output S~IDE MOTOR RETURN and input SLIDE ADVANCED LIMIT SWITC~ are "vffn. For demonstration purposes, i:he table of FIG. 9 also shows all operations having two seconds minimum time and four seconds maximum time in zone.
Figure 9 also illustrates zone transfer in the event of a change in input or output state. For.example,..in Zone lr it is expected that 5LIDE ADVA~CED LIMIT SWITCH..input will change from "on" to ~off", whereby zone logic will transer to Zone 2. Any other I/O change is an error, and logic transfers to error Zone 99. Likewise, in Zone 2, it is expected that the next I~O change will be activation of SLIDE ADVANCED LIMIT
SWITCH, whereby logic transfers to Zone 3. Note that only one I/O signal changes between Zones. MINIMUM TIMÆ and MAXIMUM
TIME blocks are checking the times in zone. The numbers "2l' and "4" represent the acceptable times. The blocks also show the number l99" to indicate that, if less than minimum or more than maximum time in the zone is experienced,the system transfers to Zone 99 and shuts down the machine.
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A flow diagram is interposed between zone 1 and zone 2 to show the flow of events (the flow between other zones being similar)~ The number "2" is a circle (circle meaning from "on"
to ''off~) in the SLIDE RETURNED LI~IT SWITCH block of Zone 1 indicates that, when this input changes due to the SLIDE RETURNED
LIMIT SWITCH turning off, the logic attempts to transfer the machine into Zone 2. First, the tim~ in zone is compared with the minimum time in zone to make certain that the machine has been in Zone 1 for at least the minimum required time. Then, the 1~ time in zone is compared with the maximum permitted time in zone to make certain that the maximum time has not been exceeded.
These two zone timer values effectively form a window in which the function of a zone must take place.
Next the MPU writes the Zone 1 image into the recorder along with the I/O image that caused the exit from Zone 1. Tak-ing SLIDE MOTOR ADVANCE as the leftmost bit of the six bits (inputs and outputs listed at the top of the chart) in the zone and MAXIMUM TIME as them rightmost bit, the æone image is written into the recorder as "101000" with Nl~ representing "on" and "0"
representing "off". The recorder now has a record that the machine has been in Zone 1, and the conditions that existed in Zone 2. Next, the machine slide will move off the returned limit switch and this bit will change from ~on~ to off" establishing zone 2 conditions. At this point, if a change in output was required, it would occur. It so happens that transfer from zone 1 to Zone 2 does not require a change in output, only the inputs changed requir1ng a new zone to be defined. The push bottom lights for Zone 2 are turned on and latched. Next, the MPU con-tinually checks Zone 2 conditions until there is change in input,or a change in output if something in the output system has failed. When a change occurs, the process is repeated, and the process proceeds as planned on through the cycle of the zones and starts again with Zone 1.
Looking at Zone 2, it will be apparent that the SLIDE
MOTOR ADVANCE output block shown l~on" and all other blocks show loffl', and that SLID~ ADVANCED LIMIT SWITCH must change from "off" to ~'on~ for the system to advance to zone 3. When feedback from slide motor 10 turns off, transition to Zone ~ occurs~
The recorder memory maintains a record or history of all zones through which the mechanism has travelled. If an error zone has occurred, the bit pattern "000000" will be written into the recorder, and the input and output conditions leading up to the error are retained for diagnostic purposes. This is an important diagnostic tool. Upon occurrence of an error zone, any action that has been determined in advance can be taken. Several ; error zones can be used with different actions, or no action, taking place in some error zones. All combinations of input and output are mathematically guaranteed to be handled. Only the programmed zone images will be allowed to proceed, with estab-lished minimum and maximum times in zone. Any other combinations of input and output will result in transition to an error zone that may or may not cause the mechanism to stop. Only inputs and outputs for carrying out the machine operation need to be consid-ered in creating the æone tableO All other combinations are mis fits resultin~ in transition to an error zone.
As previously stated, the logi~ is organized into func-tional blocks or zones that are named according to th2 physicalmachine action t~king place. These names are used by the diag-nostic process to identify the action taking place in the machine when a fault occurs. The input and output devices are also given descriptive names by the programmer, which facilitates the diag-nostic names by the programmer, which facilitates the diagnosticprocess of creat1ng meaningful messages such as "WHILE DRILL
SLIDE ADVANCING RETURNED LIMIT SWITCH CAME ON UNEXPECTEDLY " .
Eigure 10 is a schematic diagr~m which illustrates this diagnostic feature of the present invention. Station ~, IJ
computer 40 communicates with orchestrater computer 72 on loop 41. When an error occurs at the station, orchestrater computer 72 interrogates the memory of station computer 40 and receives bi~ patterns indicating the error. These bit patterns are f~d into a command interpreter 74, which translates the bit pattern into words and phrases according to a preprogrammed table 75 in its memory, and combines these words and phrases into an understandable message. The message is then displayed on the CRT screen of the terminal 760 Assume, for example, that returned limit switch 32 closes while the machine slide is advancing ~ i.e. while operating in Zone 2. Since this is not defined as a regular condition to be expected in Zone 2, an error is indicateda Orchestrater computer 72 interrogates station computer 40, and the latter sends a bit pattern such as 00010100 that translates in the command interpreter into "while" and "slide advancing" and into "returned limit switch turned on" and "unexpectedly"~ The message that appears on the terminal screen is "WHILE DRI~L SLIDE ADVANCING RETURN~D LIMIT
SWITCH CLOSED UNEXPECTEDLY". Thus, command interpreter 74 and preprogrammed tables 75 together comprise an error message composer which automatically associates predefined text with the error message received from the station computer. It will -~e noted in particular that this feature of the inven~ion ~coordinates with the use of predefined zone logic às hereinabove described since examination of the zone image and unexpected event effectively defines the error message. The system thus presents the diagnosis of the problem in a standard language readilyunderstood by humans. An operator immediately identifies the fault without Eurther thought or interpretation of logic consequences of relay contacts. It will be appreciated that the error messages themselves are not preprogrammed, only individual message segments associated with specific conditions.
Thus, the designer need not consider all possible combination of errors.
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An algorithm for composing an error message is shown in Figure 17. Variables are shown in brackets and fixed information - i.e. "WHILEn - is shown in blocks~ Zone name~
are selected from the zone logic table. The name of the offending bit is taken from the I/O listings of the tables~ The zone engine extracts these names by identifying the zone and proceeding across the I/O element image to locate the erroneou~
condition. An I/O table contained in the command interpreter is illustrated in Figure 19. An example of an error message is shown in Figure 18. The I/O table shown in Figure 19 has a few entries for demonstration purposes. This table shows the name of the I/O device~ the station where it is located~ the slot number in the panel where the I/O device is located, and the wire number connected to that I/O device. Each of the I/O
slots and wires i5 labeled. The physical arrangement oE these I/O devices and wires is shown in co-pending patent application "Control Station including a conductively Isolated Depluggable . .
Controllern--R. T. Lovrenich. If a machine transfers from Zone 1 to Zone 3 for example when it should transfer to Zone 2, it will first transfer to Zone 3 as instructed, but seeing the wrong set of input and output conditions it will exit to the error ~one. In the meantime it will have exited Zone 16 too quickly and violated the minimum time in zone. This stops the progxam and generates a message "unexpected zonen.
Figures 11-16 of the drawings illustrate the use of a zone logic table when designing a more complex production line~ The tables has been completed to operate a system having an orchestrater computer, a drill station with a slide and a rotating spindle, a transfer station, and a clamp station. In practice more work stations~ such as milling machines, gages, etc. may be involved. However, the demonstration is limited to one work station for sake of simplicity. Zones are listed by their names along the left side of the tables and I/O functions are listed along the top of the tables. This represents the , . . , ~ ~ . ..
2 ~ 2 ~
entire design of the system. It is done in plain lanquage. A
complete production line is classified as a "machine"; a station is classified as a "station"; and a mechanical device is cla~sified as a "mechanism~. Mechanisms are combined to form a station and stations are combined to form a machine. Use of the "standard" zone logic table form as shown in the drawings to design individual station logic will be self-evident from FIGS. 11-16 in view of the preceeding discussion.
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Figure 5 is a pictorial ~iew showing the sequence of zones in FIGo 2 with the positions of the limit switches and the conditions of the motion power indicated. Each zone image is read as a vertical slice in the viewO
Figure 6 is a diagrammatic view of Zone 1 in FIG5. 2 and 5 showing upcoming zone possibilities when the machine completes its function in the current zone.
Figure 7 is a diagrammatic view showing sixteen possible zone images with four system elements (two switches and two motor conditions). The zone images are read as vertical slices in the view~
Figure 8 is a fragmentary block diagram of the station computer.
Figure 9 is a schematic diagram and flow chart demonstrating the operation of the system.
Figure 10 is a schematic diagxam of an orchestrater computer and a station computer connlected in a communication loop with the orchestrater computer presenting error messages on a computer terminal CRT.
Figures 11-16 are pictorial illustrations of zone logic tables for a more complex machine system.
Figure 17 shows the algoritbm used to produce diagnostic messages in the system of the present invention.
Brackets indicate variables and a block indicates a fixed word.
Figure 18 shows a portion of a CRT screen presenting an errormessage generated by the system of the present invention.
Figure 19 shows a portion of an Input/Output table present in the command interpreter of the systemO
petailed Descri~tion The term "mechanism" as used herein is defined to mean a device that produces motion, such as a slide drive motor, a spindle motor or a clamp solenoid valve and cylinder as shown in Figure 4. "Inputs" sense mechanism conditions and send --S~
electrical signals to a logic control device. Examples are limit switches, digital coded signals and sensing devices such as shown in Figure 3. "Outputs" are generat~d by a control logic device and actuate mechanisms as illustrated in Figure 4. The control logic device drives outputs in accordance with the condition~ specified in the zone tables as described hereinafter. The following explanation involves a simple drilling machine that automatically moves a rotating drill against a workpiece to drill a hole, withdraws the drill, and returns back to the starting position. The cycle is automatically repeated. It will be appreciated that this relatively simple application of the invention is by way of example only.
Referring to Figure 1, the drillingmachine 10 includes a base 12 with a reversible electric motor 16 mounted thereon.
Motor 16 has an output shaft 18 coupled through a geared transmission 22 to drive a worm shaft 24. A machine slide 26 is slidably mounted on base 12 in engagement with worm shaft 24.
A drill head 28 rotates a drill bit 30 for drilling a hole in a workpiece (not shown). Limit switches 32 and 34 are positioned on machine base 12, and fingers 36 and 38 on slide 26 engage limit switches 32, 34 at the extreme limits of travel of the machine slide. Limit switches 32, 34 are connected to a station computer 40. Motor 16 is powered by a motor controller 54 which provides a feedback signal indicative of motor operation.
Controller 54 is coupled to station computer 400 Computer 40 is also connected to a communication loop 41 that contains an orchestrater computer 72.
The general operation of machine 10 requires slide 26 to move off returned limit switch 32 by energizing motor 16 to rotate lead screw 24 and move slide 26 forward until finger 38 engages advanced limit switch 34. At this point motor 16 must be stopped and energized to rotate lead screw 24 in the opposite direction for reversing the direction of travel of machine slide 26 until finger 36 engages limit switch 32. Again _. ~
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motor 16 is energized to move the slide in the advance direction, and so on in continuous cycling. Th~ current in the motor starter coil from line 48 to is sensed in conventional fashion and is fed back to microprocessor 40 to reflect the condition of the motor 16~ The condition of the motor starter coil is continually sensed so that the output is confirmed while the current is present.
A control panel 45 is connected to station computer 40 and includes push buttons 47 that indicate functions such as nstart drill motor~ r "advance slide", "single step", nstop drill motor", "return slide~, "automatic" and "manual". Push button logic 51 couples control panel 45 to stator computer 40.
A xelay 52 is connected to station computer 40 to shut down machine 10 if an error is detected.
Referring to Figure 2, the "zones" of operation o~
drilling machine 10 are represented . In Zone No. 1, machine slide 26 is ADVANCING OFF returned limit switch 3~. Zone No.
2 represents the drilling machine slide 26 ADVANCING BETWEEN
the limit switches~ Zone No. 3 represents drilling machine slide 26 ADVANCED FROM returned limit switch 32 and engaging advanced limit switch 34. Zone No. 4 represents machine slide 26 in ADVANCED position and with slide motor 16 stopped. Zone No. 5 represents machine slide 26 R~TURNING OFF advanced limit switch 34. Zone No. 6 represents machine slide 26 RETURNING
BETWEEN the limit switches. Zone No. 7 represents machine slide 26 RET~RNING FROM advanced limit switch 34 and engaging the returned limit switch 32. Zone 8 represents machine slide 26 RETURNED and motor 16 stopped. Zone No. 0 represents machine ~lide 26 stopped between limits. As will become apparent from the following discussion, zone description in upper case letters in the preceeding discussion is important in com~osing error messages. ~
Figure 5 is a pictorial view showing the zone patterns.
The eight possible inputs and eight possible outputs are - : -.
~. , 2 ~
illustrated7 Theblack or filled blocks represent power ~output~or switch (input) "on" and a blank block represent power or switch "off". For example, in Zone 1, input to the station computer 40 is limit switch 32 "on" and limit switch 34 "off".
The outpu~ from the station computer causes motor controller 54 and motor 16 to move the machine slide in either the advance or return direction. Again, in Zone 1, motor 16 is ~on" in the advance direction and "of" in the return airection. Vertical slices through the diagram in Figure 5 represent "images" of each of the nine productive zones.
Figure 6 is a pictorial view s~owing the mechanism operating in Zone 1. Any change in input or output causes a zone change. Figure 6 demonstrates that the only productive operating zone to follow Zone 1 is Zone 2. Any other zone is undefined in the zone table of FIG. 7, and therefore is interrupted as in error zone. All the possible combinations of conditions do not have to be anticipated because the system operating zones have been constrained during programming to those planned~ For purposes of explanation, those zones relative to the planned operation steps o~ the machine during error free operation, have been defined as "productive zones". Only the productive zones need to be considered. For example, if the _inputs 5hoW both limit switches 32 and 34 "on", this i~
automatically an error zone because such conditions are not present in the programmed zones ~FIG. 5)~ The various combinations can be quickly entered into a zone logic table by defining all productive zones plus at least one error zone.
The error zone may issue a shut down signal to-the system. With two limit switches and two motor directions r there are only sixteen possible physical combinations, as shown in Figure 7.
The number of possible combinations is two (on/off) mathematically taken to the power of the number of on-of~ devices present.
2 ~
~igure 8 is a block diagram of station computer 40. A
block of RAM 58 includes I/O memory, timer memory 64, zone data table memory 6~, and ~recorder~ and journal memories 68.70. Sta-tion computer 40 includes an MPU 42 which communicates with mem-ory 58 via the address bus 59 and the data bus 60. The program for executlng station operation is stored in command interpreter EPROM 61. An oscillator 62 supplies the clock function. MPU 42 executes the program in EPROM 61 and carries out the system func-tions shown in Figure 5 Upon entry into a new zone, MPU 42 takes the following action: write the new zone number and related information to recorder memory 68, set an internal zone timer to zero, and set the physical outputs as indicated by the zone table. For exam-ple, upon entry into Zone 1 (Fig. 5), MPU 42 energizes in the advance direction. MPU then continues to motor the I~O image from and to limit switches 32,3~, monitor controller 54 and motor 60, and to compare this information to the zone image in Zone 1.
I~ the event of a change of I/O indicia, MPU 42 automatically steps to the appropriate zone reflecting the new I~O image, l.e.
; zone 2 in the event of proper operation (Fig. 6), or an error zone if the latter is appropriate. In the event of proper opera-tion, the entire cycle repeats continuously.
Timer memory 64 checks the time in zone against minimum and maximum times for that zone stored in zone data table 66.
Recorder memory Ç8 records the history of zones over a number of zone changes, such as one thousand zone changes for example, and continually overwrites this data to reflect the last one thousand zone changes. This data is use~ul in analysis of an error, e.g.
to determine that the machine has been slowly deteriorating.
Journal memory 709 records error information continually from start-up of the system. A user can examine error history in pre-vious months or years. A copy of the journal or recorder can be sent to the screen of terminal 69, or .
a hard copy can be produced at printer 71 in accordance with the program in EPROM ~1.
~ igure 9 demonstrates operation of the system for drill station 10, including the zone timer as logic "inputs", for Zones 1-4 and 99~ ~he outputs SLID~ MOTOR ADVANCE and SLIDE
MOTOR RETURN, and the inputs SLIDE RETURNE~ LIMIT SWITCH and SLIDE ADVANCED LIMIT SWITCH are listed along the top, along with MINIMUM TIME IN ZONE and MAXIMUM TIME IN ZONE. The zone .~unctions are listed along the left side, with the zone n~mbers beside the function names~ One zone function is identified as ERROR Zone 99. The zon~ image for each of the operating zones is presented.in a horizontal slice of the chart next to the zone name and number. The hatched lines indicate which inputs and which outputs are turned "on" (hatched) and "off" ~unhatched~
in each zone. For example, in Zone 1, the SLIDE MOTOR ADVANCE
output and the RETURNED LIMIT S~ITCH input are "on". Output S~IDE MOTOR RETURN and input SLIDE ADVANCED LIMIT SWITC~ are "vffn. For demonstration purposes, i:he table of FIG. 9 also shows all operations having two seconds minimum time and four seconds maximum time in zone.
Figure 9 also illustrates zone transfer in the event of a change in input or output state. For.example,..in Zone lr it is expected that 5LIDE ADVA~CED LIMIT SWITCH..input will change from "on" to ~off", whereby zone logic will transer to Zone 2. Any other I/O change is an error, and logic transfers to error Zone 99. Likewise, in Zone 2, it is expected that the next I~O change will be activation of SLIDE ADVANCED LIMIT
SWITCH, whereby logic transfers to Zone 3. Note that only one I/O signal changes between Zones. MINIMUM TIMÆ and MAXIMUM
TIME blocks are checking the times in zone. The numbers "2l' and "4" represent the acceptable times. The blocks also show the number l99" to indicate that, if less than minimum or more than maximum time in the zone is experienced,the system transfers to Zone 99 and shuts down the machine.
_/D ~
2 ~
A flow diagram is interposed between zone 1 and zone 2 to show the flow of events (the flow between other zones being similar)~ The number "2" is a circle (circle meaning from "on"
to ''off~) in the SLIDE RETURNED LI~IT SWITCH block of Zone 1 indicates that, when this input changes due to the SLIDE RETURNED
LIMIT SWITCH turning off, the logic attempts to transfer the machine into Zone 2. First, the tim~ in zone is compared with the minimum time in zone to make certain that the machine has been in Zone 1 for at least the minimum required time. Then, the 1~ time in zone is compared with the maximum permitted time in zone to make certain that the maximum time has not been exceeded.
These two zone timer values effectively form a window in which the function of a zone must take place.
Next the MPU writes the Zone 1 image into the recorder along with the I/O image that caused the exit from Zone 1. Tak-ing SLIDE MOTOR ADVANCE as the leftmost bit of the six bits (inputs and outputs listed at the top of the chart) in the zone and MAXIMUM TIME as them rightmost bit, the æone image is written into the recorder as "101000" with Nl~ representing "on" and "0"
representing "off". The recorder now has a record that the machine has been in Zone 1, and the conditions that existed in Zone 2. Next, the machine slide will move off the returned limit switch and this bit will change from ~on~ to off" establishing zone 2 conditions. At this point, if a change in output was required, it would occur. It so happens that transfer from zone 1 to Zone 2 does not require a change in output, only the inputs changed requir1ng a new zone to be defined. The push bottom lights for Zone 2 are turned on and latched. Next, the MPU con-tinually checks Zone 2 conditions until there is change in input,or a change in output if something in the output system has failed. When a change occurs, the process is repeated, and the process proceeds as planned on through the cycle of the zones and starts again with Zone 1.
Looking at Zone 2, it will be apparent that the SLIDE
MOTOR ADVANCE output block shown l~on" and all other blocks show loffl', and that SLID~ ADVANCED LIMIT SWITCH must change from "off" to ~'on~ for the system to advance to zone 3. When feedback from slide motor 10 turns off, transition to Zone ~ occurs~
The recorder memory maintains a record or history of all zones through which the mechanism has travelled. If an error zone has occurred, the bit pattern "000000" will be written into the recorder, and the input and output conditions leading up to the error are retained for diagnostic purposes. This is an important diagnostic tool. Upon occurrence of an error zone, any action that has been determined in advance can be taken. Several ; error zones can be used with different actions, or no action, taking place in some error zones. All combinations of input and output are mathematically guaranteed to be handled. Only the programmed zone images will be allowed to proceed, with estab-lished minimum and maximum times in zone. Any other combinations of input and output will result in transition to an error zone that may or may not cause the mechanism to stop. Only inputs and outputs for carrying out the machine operation need to be consid-ered in creating the æone tableO All other combinations are mis fits resultin~ in transition to an error zone.
As previously stated, the logi~ is organized into func-tional blocks or zones that are named according to th2 physicalmachine action t~king place. These names are used by the diag-nostic process to identify the action taking place in the machine when a fault occurs. The input and output devices are also given descriptive names by the programmer, which facilitates the diag-nostic names by the programmer, which facilitates the diagnosticprocess of creat1ng meaningful messages such as "WHILE DRILL
SLIDE ADVANCING RETURNED LIMIT SWITCH CAME ON UNEXPECTEDLY " .
Eigure 10 is a schematic diagr~m which illustrates this diagnostic feature of the present invention. Station ~, IJ
computer 40 communicates with orchestrater computer 72 on loop 41. When an error occurs at the station, orchestrater computer 72 interrogates the memory of station computer 40 and receives bi~ patterns indicating the error. These bit patterns are f~d into a command interpreter 74, which translates the bit pattern into words and phrases according to a preprogrammed table 75 in its memory, and combines these words and phrases into an understandable message. The message is then displayed on the CRT screen of the terminal 760 Assume, for example, that returned limit switch 32 closes while the machine slide is advancing ~ i.e. while operating in Zone 2. Since this is not defined as a regular condition to be expected in Zone 2, an error is indicateda Orchestrater computer 72 interrogates station computer 40, and the latter sends a bit pattern such as 00010100 that translates in the command interpreter into "while" and "slide advancing" and into "returned limit switch turned on" and "unexpectedly"~ The message that appears on the terminal screen is "WHILE DRI~L SLIDE ADVANCING RETURN~D LIMIT
SWITCH CLOSED UNEXPECTEDLY". Thus, command interpreter 74 and preprogrammed tables 75 together comprise an error message composer which automatically associates predefined text with the error message received from the station computer. It will -~e noted in particular that this feature of the inven~ion ~coordinates with the use of predefined zone logic às hereinabove described since examination of the zone image and unexpected event effectively defines the error message. The system thus presents the diagnosis of the problem in a standard language readilyunderstood by humans. An operator immediately identifies the fault without Eurther thought or interpretation of logic consequences of relay contacts. It will be appreciated that the error messages themselves are not preprogrammed, only individual message segments associated with specific conditions.
Thus, the designer need not consider all possible combination of errors.
2 ~
An algorithm for composing an error message is shown in Figure 17. Variables are shown in brackets and fixed information - i.e. "WHILEn - is shown in blocks~ Zone name~
are selected from the zone logic table. The name of the offending bit is taken from the I/O listings of the tables~ The zone engine extracts these names by identifying the zone and proceeding across the I/O element image to locate the erroneou~
condition. An I/O table contained in the command interpreter is illustrated in Figure 19. An example of an error message is shown in Figure 18. The I/O table shown in Figure 19 has a few entries for demonstration purposes. This table shows the name of the I/O device~ the station where it is located~ the slot number in the panel where the I/O device is located, and the wire number connected to that I/O device. Each of the I/O
slots and wires i5 labeled. The physical arrangement oE these I/O devices and wires is shown in co-pending patent application "Control Station including a conductively Isolated Depluggable . .
Controllern--R. T. Lovrenich. If a machine transfers from Zone 1 to Zone 3 for example when it should transfer to Zone 2, it will first transfer to Zone 3 as instructed, but seeing the wrong set of input and output conditions it will exit to the error ~one. In the meantime it will have exited Zone 16 too quickly and violated the minimum time in zone. This stops the progxam and generates a message "unexpected zonen.
Figures 11-16 of the drawings illustrate the use of a zone logic table when designing a more complex production line~ The tables has been completed to operate a system having an orchestrater computer, a drill station with a slide and a rotating spindle, a transfer station, and a clamp station. In practice more work stations~ such as milling machines, gages, etc. may be involved. However, the demonstration is limited to one work station for sake of simplicity. Zones are listed by their names along the left side of the tables and I/O functions are listed along the top of the tables. This represents the , . . , ~ ~ . ..
2 ~ 2 ~
entire design of the system. It is done in plain lanquage. A
complete production line is classified as a "machine"; a station is classified as a "station"; and a mechanical device is cla~sified as a "mechanism~. Mechanisms are combined to form a station and stations are combined to form a machine. Use of the "standard" zone logic table form as shown in the drawings to design individual station logic will be self-evident from FIGS. 11-16 in view of the preceeding discussion.
.
' - :
Claims (18)
1. An apparatus for controlling a machine having an error means for indicating an error condition in said machine, said error means comprising a first table containing a list of zone names and input/output image names; and a second table con-taining a plurality of error designations wherein said error means formulates an error message indicative of said error condi-tion.
2. A method for indicating an error condition of an apparatus comprising the steps of looking up a zone name and an input/output image name; determining an error designation from a plurality of error designations indicative of said error condi-tion; combining said zone name, said input/output name, and said error designation into an error message; and displaying said error message.
3. A method of indicating an error condition of an apparatus having at least one mechanism, one input, one output and a plurality of states of operation characterized by:
storing a unique zone name for each zone of said mechanism, storing a unique input/output name for each input/output, providing at least one template containing fixed words and blank spaces, and upon detecting an error, selecting zone and input/output names for insertion into the blanks of the appropriate template to generate a message using data stored upon detection of the error.
storing a unique zone name for each zone of said mechanism, storing a unique input/output name for each input/output, providing at least one template containing fixed words and blank spaces, and upon detecting an error, selecting zone and input/output names for insertion into the blanks of the appropriate template to generate a message using data stored upon detection of the error.
4. The method as set forth in claim 3 further characterized by:
saving the actual input/output image when leaving a zone, and using said image for selecting a next zone and, if an error is detected, for generating the error message.
saving the actual input/output image when leaving a zone, and using said image for selecting a next zone and, if an error is detected, for generating the error message.
5. The method as set forth in claim 3 further characterized by:
generating a plain language text error message.
generating a plain language text error message.
6. The method as set forth in claim 3 further characterized by:
the step of storing a unique zone name includes storing at east one error zone name, indicating an error condition when, after determining to depart a present zone, no next zone can be selected, and entering the error zone.
the step of storing a unique zone name includes storing at east one error zone name, indicating an error condition when, after determining to depart a present zone, no next zone can be selected, and entering the error zone.
7. The method as set forth in claim 3 further characterized by:
displaying an error message indicative of an error condition.
displaying an error message indicative of an error condition.
8. The method as set forth in claim 3 further characterized by:
recording an identifier of each zone that is departed and the actual time spent in that zone.
recording an identifier of each zone that is departed and the actual time spent in that zone.
9. The method as set forth in claim 3 further characterized by:
recording the occurrence of each error in a journal.
recording the occurrence of each error in a journal.
10. The method of claim 3 further comprising the steps of:
storing a table containing a list of zone names, input/output names, input/output images for each zone and allowed zones for each said zone, storing in a memory of plurality of error designations, formulating an error message from said table and memory indicative of said error condition, and generating the error message from the names of the last alid zone and the input/output names that caused the input/output image to not match the last valid zone or any of the allowed next zones.
storing a table containing a list of zone names, input/output names, input/output images for each zone and allowed zones for each said zone, storing in a memory of plurality of error designations, formulating an error message from said table and memory indicative of said error condition, and generating the error message from the names of the last alid zone and the input/output names that caused the input/output image to not match the last valid zone or any of the allowed next zones.
11. An apparatus for indicating an error condition in a machine having at least one mechanism, one input, one output and a plurality of states of operation characterized by:
means for storing a unique zone name for each zone of said mechanism, means for storing a unique input/output name for each input/output, means for providing at least one template containing fixed words and blank spaces, and means, upon detecting an error, for selecting zone and input/output names for insertion into the blanks of the appropriate template to generate the message using data stored upon detection of the error.
means for storing a unique zone name for each zone of said mechanism, means for storing a unique input/output name for each input/output, means for providing at least one template containing fixed words and blank spaces, and means, upon detecting an error, for selecting zone and input/output names for insertion into the blanks of the appropriate template to generate the message using data stored upon detection of the error.
12. The apparatus of claim 11 further characterized by:
means for saving the actual input/output image when leaving a zone, and means for using said image for selecting a next zone and, if an error is detected, for generating the error message.
means for saving the actual input/output image when leaving a zone, and means for using said image for selecting a next zone and, if an error is detected, for generating the error message.
13. The apparatus of claim 11 further characterized by:
means for generating a plain language text error message.
means for generating a plain language text error message.
14. The apparatus as set forth in claim 11 further characterized by:
the means for storing a unique zone name includes storing at least one error zone name, means for indicating an error condition when, after determining to depart a present zone, no next zone can be selected, and means for entering the error zone.
the means for storing a unique zone name includes storing at least one error zone name, means for indicating an error condition when, after determining to depart a present zone, no next zone can be selected, and means for entering the error zone.
15. The apparatus of claim 11 further characterized by:
means for displaying an error message indicative of an error condition.
means for displaying an error message indicative of an error condition.
16, The apparatus of claim 11 further characterized by:
means for recording an identifier of each zone that is departed and the actual time spent in that zone.
means for recording an identifier of each zone that is departed and the actual time spent in that zone.
17. The apparatus of claim 11 further characterized by:
means for recording the occurrence of each error in a journal.
means for recording the occurrence of each error in a journal.
18. The apparatus of claim 11 further characterized by:
means having a table containing a list of zone names, input/output names, input/output images for each zone and allowed zones for each said zone, a memory containing a plurality of error designations, means for formulating an error message from said table and memory indicative of said error condition, and means for generating the error message from the names of the last valid zone and the input/output names that caused the nput/output image to not match the last valid zone or any of the allowed next zones.
means having a table containing a list of zone names, input/output names, input/output images for each zone and allowed zones for each said zone, a memory containing a plurality of error designations, means for formulating an error message from said table and memory indicative of said error condition, and means for generating the error message from the names of the last valid zone and the input/output names that caused the nput/output image to not match the last valid zone or any of the allowed next zones.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2064624 CA2064624A1 (en) | 1992-04-01 | 1992-04-01 | Control system with diagnostic logic |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2064624 CA2064624A1 (en) | 1992-04-01 | 1992-04-01 | Control system with diagnostic logic |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2064624A1 true CA2064624A1 (en) | 1993-10-02 |
Family
ID=4149546
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2064624 Abandoned CA2064624A1 (en) | 1992-04-01 | 1992-04-01 | Control system with diagnostic logic |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2064624A1 (en) |
-
1992
- 1992-04-01 CA CA 2064624 patent/CA2064624A1/en not_active Abandoned
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