GB1592906A - Industrial process control system - Google Patents

Description

(54) INDUSTRIAL PROCESS CONTROL SYSTEM (71) We, THE FOXBORO COMPANY, a Corporation organized and existing under the laws of the Commonwealth of Massachusetts, United States of America, of Neponset Avenue, Foxboro, Massachusetts 02035, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to industrial process control systems of the type employed with complex processes involving a large number of controlled process conditions such as temperature, flow-rate, and the like. More particularly, this invention relates to such systems having visual display means for presenting to the process operator or process engineer intelligible information to aid in exercising control over the process.

Industrial process control apparatus has evolved over the years from relatively simple individual controllers for respective process conditions to very large integrated systems including digital processing equipment. As the processes became more complex, there was greater need for acquiring process information in a more effective manner for better use by the process operators. Traditionally, complex control systems have included large control panels, thirty feet or so in length, with the process information and operator control devices located at various places along the panel.

It has been recognized that such a dispersed arrangement has serious drawbacks, and a number of propsals have been made for systems in which the information and controls are more effectively consolidated. One such prior system arrangement is disclosed in U.S. Patent 3,971,000, issued on July 20, 1976, to N. O.

Cromwell, and assigned to the assignee of this application. Although such systems have represented an important advance in the art, and have provided significant advantages, nonetheless it has been found that still further improvements are required to more fully meet the needs of the process industry, particularly the need for more effective man/process interface arrangements.

Further prior art disclosed in articles by R. Dallimanti published in Instrumentation Technology and respectively entitled "Future Operator Consoles for Improved Decision-making and Safety" (August 1972), "New Designs for Process Control Consoles (November 1973) and "Human Factors in Control Center Design" (May 1976) describe the use of a two-level display providing at one level an overview of the system and at the second level process loop details, in conjunction with either one or two CRT's. The displays presented are eleviationtype displays requiring the characterization of each loop in the process. In this manner, the system disclosed in these articles is limited, due to the physical limitation of the size of the display screen, to the presentation of a fixed number of process loops. One important object of the present invention is to overcome this disadvantage by providing a display scheme in which the overview display presents only group identifiers, rather than loop identifiers. By such means, theoretically, an infinite number of loops is provided for because the group is not fixed.

According to the present invention, an industrial process control system used with a complex process, comprises means which measure the values of a large number of conditions in the process, and means which receive the measurements and develop corresponding process control signals for elements such as valves and the like in the system, each combination of means which measure a condition and which develop a corresponding control signal defining a process control loop; said loops being organized in groups pertaining to respective process tasks, and said groups being clustered as distinct areas of the overall system; and the system further comprises: an operator's console including a display device and a data-entry keyboard; a display memory for said display device containing digital data for continuously controlling the display on said display device; a digital storage memory comprising a plurality of storage sections each with a set of digital display data defining a corresponding complete display for said display device and arranged to be selectively transferred to said display memory to control the display on said display device; a first set of said digital display data serving to present in separate display sectors of said display device summary information concerning the control status of respective process areas; said summary information in each such sector comprising a listing of multicharacter group identifiers each designating a corresponding one of said process groups forming the respective process area; said digital storage memory having further sets of digital display data each representing detailed information concerning a corresponding area summarized in a respective one of said sectors of the display device produced by the digital data from said first set of said digital data; and display transfer means jointly controlled by preselected keys of said keyboard and by the storage in said display memory of any one of said sets of stored digital display data, and being operable by said pre-selected keys, when one of said sets of stored digital display data has been placed in said display memory, to transfer to said display memory a corresponding one of said further sets of stored digital display data.

An advantage of the invention is that, it can, if required. provide a system that combines the following functional features: 1. Utilizes hierarchical displays each representing a particular level of plant information, such as plant, area and group displays; 2. Provides a plant overview display which is loop independent in that the lowest process level indicated on the display is the "group-level", rather than the "loop-level"; 3. Each of the displays is segmented, and the segments are utilized to indicate the residence of the loop in alarm 4. Segment selection keys are provided for allowing an operator to selectively choose a particular segment for a more detailed display; and, 5. Alarm indicators are always displayed in the segment identifying the loop in alarm independent of the display then being presented.

A preferred system embodying this invention comprises at least one operator's console having a CRT display device (or the like) driven by a stored-program digital processor under the control of an operator's keyboard. The processor is connected by a transmission line to interface equipment which transfers data between the processor and conventional process control equipment including analog controllers, condition sensors, process valves, and the like. Signals representing the states of the process control equipment, and the process condition valves, etc., are regularly relayed to the digital processor which thus contains in its memory a comprehensive summary of the pertinent data respective the process.

The operator at the console can, through the keyboard, bring to the CRT screen any of a large group of special displays to provide a summary of information respective the process, or more detailed information, at various levels, respecting different portions of the process. The operator also can, in conjunction with certain special CRT displays, manipulate process parameters through operation of the keyboard.

These functions moreover are carried out, by uniquely-controlled man/process interactions involving special relationships between the CRT displays and the functioning of the keyboard. The console keyboard includes a group of so-called variable-function keys which are unlabelled and perform functions determined by the particular display being presented on the CRT. The function to be performed by any such key is identified by symbols appearing at the lower edge of the CRT screen, with such symbols being physically correlated with the positions of the corresponding keys. The keyboard also includes fixed-function keys which perform dedicated functions not altered by the nature of the current CRT display. The keyboard provides quick access to a whole array of command, display, monitoring, trending, alarm acknowledge, and related functions.

The assignment of a variable-function key, as indicated by the CRT display, identifies an action available to the operator. Unassigned keys are automatically deactivated, by operation of the processor, so that "illegal" operator actions are prohibited. This is very important in preventing operator mistakes which can cause serious damage.

The available keyboard functions identified on the CRT screen also serve as sign-posts for the operator, giving him a quick understanding of the available options he has in (1) seeking additional or more detailed information, or (2) taking proper control actions such as by adjusting appropriate process parameters. The operator does not have to memorize the locations of a large number of "dedicated" keys; the display itself leads him along in a preplanned manner. Not only does this save critical time in dealing with plant emergencies, but in addition it encourages self-training for the operators in minimum time.

A specialized and comprehensive set of CRT displays has been incorporated in the processor memory, each available to be called up by the operator as needed.

These displays are developed in a hierachical fashion, with the highest level being overall plant information, the next level providing more specific information about separate areas of the plant, a third level presenting still more detailed information respecting respective groups of individual process control loops, and a fourth level providing specialized data about individual loops in any selected group.

Operator interaction with the process is accomplished by adjustment of process control loop parameters. These parameters (control variables) may be considered, somewhat arbitrarily, as falling into one of three categories: (1) primary control parameters which indirectly affect the output to the process from the controllers (e.g. setpoint, ratio, bias), (2) direct control of the outputs to process actuators (valves) which by-pass the controller (e.g. manual output, contacts), and (3) reference values used by the operator to indicate level of control performance or normalcy (alarm limits, output pointers).

The establishment or adjustment of process parameters is achieved by operation of the variable-function keyboard in combination with the CRT "loop" displays. Although data for a number of loops may be displayed simultaneously on the CRT, the keyboard at one time can only be associated with one loop for making parameter adjustments thereto. All values, both continuous and discrete, changed from this keyboard, are displayed on the CRT as actual readings derived from the respective controllers, not values sent to the controllers. A ramping technique is used to change all values incrementally, thereby avoiding large erroneous changes from operator entry errors or noise in the system.

As will be apparent, this apparatus provides a highly flexible display devoted solely to the efficient handling of process information. Using remarkably simple keyboard procedures, an operator is given the right information at the right time, and is assisted in assimilating that information and acting on it quickly.

Functionally, the disclosed apparatus does all of the same things, and more, as the panel display portion of a standard control system. It consolidates information from the process, displays everything the operator needs to see, and provides the means to manipulate process variables. Instead of using familiar panel-mounted faceplate instruments, the disclosed apparatus uses a video screen and a simple keyboard to allow the operator to communicate with the process. Thus he can control the operation efficiently without having to move from one panel location to another.

In many ways, the CRT display of the disclosed apparatus is an operator's "window" into the process, letting him keep track of what is happening and helping him take corrective action. The process itself, meanwhile, is being controlled by standard rack-mounted electronics. These units perform the system's input/output, control, and computing functions. Communications back and forth between the analog equipment and the CRT display are handled by a six-wire data highway, which permits the two to be located up to 5000 feet apart.

System functional capabilities include: display of measurements, set points, alarm limits, and related process parameters; performance of process monitoring and short-term historical recording; performance of alarming and alarm status logging; and access to full process control capabilities such as set-point adjustments and switching, manual output control, and other conventional operator functions.

The system also replaces such conventional operator-interactive devices as alarm lights, faceplates, special displays, pushbuttons, switches, thumbwheels, and other panel accessories.

In some of the pre-planned CRT displays, individual process loops are displayed in the form of faceplate-like graphic representations of conventional controllers to provide the operator a convenient reference to familiar values and symbols. Faceplate graphics, in turn, are supplemented by enriched information which includes engineering units, loop tags, set points, alarm points, and auto/manual loop status. In addition to promoting quick response, this supplementary information saves the operator time in filling out logs and shift reports.

Most plants are logically separated into general-to-specific levels of operation in pyramidal fashion. The apparatus of the present invention is organized in a similar fashion, with a display hierachy designed to lead the operator quickly from general alarm notification directly to the specific loop causing the alarm.

At the top of the display hierachy are plant level displays which summarize the total plants' operations or major section of a plant under control of a single operator. Typically, plant level displays are divided into eight sectors to help operators focus quickly on alarm conditions or access information on any one of the sixty-four possible groups listed on the plant display.

Area level displays provide the next level of operating details. These include both an area alarm summary (AAS) and a so-called area full value faceplate (AFF) display. There is one of each type for each of the eight sectors listed in the plant display. Alarm summaries intensify and flash the loop tag number for any of the eight loops listed within a group needing operator attention. Area full value faceplate displays offer graphic measurement and set-point presentations that correspond to loops listed on the area alarm summary.

The third level provides group displays which combine graphic and alphanumeric information, emulating an instrument faceplate, for each of up to eight loops. Digital data provides precise values for variables which appear in graphic form while graphic movements illustrate relative changes of variables being observed.

At the most detailed level, loop displays provide full value faceplate displays for all loops listed in any of the group level displays. As an operator changes operating parameters using variable function keys on the keyboard, the digital portion of that loop's display (called a "page") is intensified for the value being affected. The meaning affixed to the variable function keys is displayed at the bottom of the screen, enabling only those loop operations which may be peformed by the operator. While making adjustments to one loop, the operator can monitor the effects of those changes on other loops within the same group.

Groups of control loops can be logically grouped to match process requirements, and critical loops common to multiple process units can be included in as many different displays as desired. Thus there is no need for the operator to switch from one display to another to find out how a critical loop is being affected by adjustments being made to another loop. The supplementary digital data included on each loop display is inherently more accurate, allowing operators to read and set parameters to much closer tolerances. Also, fewer mechanical and electronic components in the loop measurement display mean better accuracy and reliability, less drift.

With an effective alarm management system as disclosed, operators can be given early warning of impending troublespots, assuring quick response and prevention of unnecessary shutdowns. The apparatus to be described has a built-in alarm management system designed to provide early recognition of process upsets, minimum operator time response and correct operator reaction. This permits advance planning of how operators will react to emergency situations.

Located above the operator's CRT screen is an alarm light panel which provides immediate indication of alarm conditions in any area of the plant. Once the operator directs his attention to the area in which the alarm exists, flashing intensified video indications lead him quickly to the specific loop in alarm.

Automatic alarm acknowledgement occurs as soon as he accesses the loop. Once accessed, appropriate keyboard actions can be taken to remedy the alarm condition. Critical plant alarms are given additional emphasis by way of an audible alert, assuring prompt operator response.

All plant alarms can be automatically logged on an optional alarm logging typer. This saves the operator time during emergency situations, allows change-ofshift summary reports to be generated, and provides a convenient listing of alarm data for future use. In addition, an optional direct-connected alarm light panel provides continuous alarm indication in the event of system shutdown.

A valid response to an alarm results in a change of displays on the display unit, a change in the status of alarm lights and silencing the horn. However, the system retains and indicates the alarm notification after acknowledgement until such time as the process condition has been corrected. At that time, the alarm system clears the notification of alarm and the alarm printer records (in black) clearance of the alarm. Each new alarm goes through this alarm procedure as it occurs.

Two types of trending are available: (1) real-time, and (2) historical. Trends are displayed either on the screen or on pen recorders. Real-time measurement data can be displayed in either quarter-screen or half-screen formats, with each variable displayed in 0100 percent range. Trends-are updated as often as every 6 seconds. Data can also be simultaneously recorded on optional pen type trend recorders which are easily accessed through fixed function keys. For historical trending and recording, the apparatus has a memory system which provides shortterm (up to 24 hours) retention of up to 200 process measurements. Data is stored on a disk and can be recalled at any time. Readout can be in quarter-screen or halfscreen format, or historical data can also be used to drive pen recorders.

For continuous plant monitoring functions, "Plant Overview Deviation Display" provides normalized bar graph indication of measurement deviation from set point in areas throughout the plant. This display gives the operator a readily available overview of plant status as well as early warning of impending alarm conditions.

It is possible to configure displays to achieve optimum process/operator interaction, and to reconfigure them at any time. Display structures and parameters can be modified in both form and emphasis, with no need to cut steel, perform rewiring, or insert new instruments. During startup, for example, when measurements and outputs are more important than alarm indications, display emphasis can be placed on those variables. Then, when the plant is on-stream and in smooth operation, emphasis can be redirected to alarm notification, quickly and easily. Also, additional process loops can be added at the desired locations simply and inexpensively.

Panel manufacturing and installation may be completely eliminated, along with the extensive wiring inherent in the conventional control panel approach.

Wiring errors are eliminated, and hookup is easier. The disclosed apparatus takes up only a fraction of the space required for conventional control panels, so control room structures can be made smaller. Also, panel and instrument servicing requirements are eliminated.

A separate engineer's keyboard ties in directly with the operator's console.

Using the ASCII data format, this keyboard is used primarily on-site for configuration and manipulating the process data base. A process system data base is generated using the engineer's keyboard in conjunction with operation keyboards. The data base is unique to each plant process and contains information that establishes set points, ratios, bias values and other monitored scan points.

Once set up, the data base can be modified as required during normal plant operation.

Other objects, aspects and advantages of the invention will in part be pointed out in, and in part be apparent from, the following description of examples of industrial process control systems considered together with the accompanying drawings, in which: Figure 1 is a pictorial view of a process control system in accordance with the invention; Figure 2 is a schematic diagram, in block format, showing details of the operator's console for the system of Figure 1 Figures 3A, 3B, and 3C present the operators keyboard in detail, and showing typical variable function keyboard labels; Figures 4, 4A, 4B, etc., illustrate the display hierarchy of Plant, Area and Group level displays; Figure 5 is a symbol key for use with the flow diagrams of a number of following drawing figures; Figure 6 is a three-dimensional diagrammatic presentation of the display access structure; Figure 7 is a flow diagram for the Area Full Value Faceplate selection and operation; Figure 8 is a flow diagram for the Group Full Value Faceplate selection and operation: Figure 9 is a diagrammatic representation of a typical process loop configuration, of the type referred to as an "Operator Set Loop"; Figure 10 shows an "Operator Set Loop" faceplate with different digital pages; Figure 11 is a diagram showing the selection and operations flow for an "Operator Set Loop" when displaying the digital page for the primary parameters; Figure 12 is a diagram showing the selection and operations flow for an "Operator Set Loop" when displaying the digital page for the alarm limits; Figure 13 is a diagram showing the selection and operations flow for an "Operator Set Loop" when displaying the digital page for the output memory pointers; Figure 14 is a table presenting the variable function keyboard symbols for the different conditions of operation with an "Operator Set Loop"; Figure 15 shows the CRT display and the corresponding keyboard status at a particular stage at the operational sequence.

Referring now to Figure 1, the system comprises an operator's console generally indicated at 100 including a CRT display device 102 and an associated operator's keyboard 104. Beneath the console is a data processing unit 106 which includes means operable in conjunction with the keyboard 104 to control the images displayed by the CRT screen, as will be explained. The console 100 is connected to remotely-located electronic control equipment 110 by a six-wire transmission "highway" 108 which transmits digital data in the form of serial pulses, in both directions.

The control equipment 110 and line 108 can be of known design, for example as shown in U.S. Patent 3,760,374 (S. A. Nabi). This equipment includes analog controllers for developing appropriate control signals for corresponding process valves 112, and interface equipment for translating between the analog signals for the process valves and the digital signals transmitted through the transmission line 108. Each interface equipment serves in effect as a slave unit for a group of controllers, providing thereto set-point signals, and receiving status signals such as condition measurements, etc. The interface unit sends back update signals for setpoint, controller output, and automatic/manual status. The process under control can be any of many different types having a large number of different process conditions, such as fluid flow, temperature and so on, to be maintained at predetermined values.

The console 100 also may include, at the right of the CRT 102, an alarm console having a set of system security alarms 114 and a more extensive set of process alarms 116. A set of area alarms 118 also is located above the CRT. There are eight alarm indicators in this set, corresponding to eight (maximum) plant areas. These alarm indicators signal an alarm condition (deviation, absolute, or bad input) in one or more loops in the corresponding plant area.

Referring now to Figure 2, the data processor unit 106 is shown to comprise a central processor 120 which at its left is connected to the transmission line 108 by a conventional communication port logic unit 122 and a driver/receiver 124. The processor 120 directs interrogating signals periodically to this line, and receives back signals representing the status of a very large number of different categories of equipment and measurements, such as the magnitudes of process conditions, the current values of control set-points, the status of on-off type control elements, and so forth. The processor also transmits control signals through the line 108, such as signals for altering the values of selected set-points, or altering the output signals from analog controllers when in "manual" state.

The central processor 120 also is coupled to a multi-bit data bus 130 which provides communication, under processor control, to a number of other parts of the system and the operator's console. Thus the data bus leads to a CRT driver 132, and an associated CRT graphics generator 134, which supply CRT drive signals to two CRT displays 102, 138. (The second CRT 138 is not shown in Figure 1, since it is not a necessary part of the system, but is shown in Figure 2 to illustrate the adaptability of the system to different application requirements; the system can readily be further augmented by additional displays). The data bus 130 also leads to a console interface 140 which in turn communicates with: (1) the operator keyboards 104, 142, at the respective display units (2) area alarms 118, 144 at those units, (3) system security indicators 114, 146 at those units, and (4) warning horns 146, 148 at the display units.

The data bus 130 also connects to three further interface units 150, 152, 154 for: (I) a pen recorder 156, (2) a printer 158, and (3) an ASCII engineer's keyboard 159. A floppy disk unit 160 and associated disk controller 162 also are tied to the data bus 130 to provide for several ancillary functions including memory reload, data base configuration, and storage and playback of historical trend data.

A principal function of the central processor 120 is to control the CRT displays at the operator's consoles. Associated with the processor is a random access memory 170 comprising a digital storage memory 172 dedicated to storage of data for the CRT displays. This memory is divided into separate sections 174 each containing a set of digital display data defining a corresponding complete display for the CRTs. The data in these sections is adapted to be selectively transferred to the CRT display driver 132 for controlling the CRTs. The display data is stored in a CRT refresh memory 176 in the CRT display driver, and controls the display image presented on the CRT.

One section 174 of the digital storage memory 172 contains display data serving to present in separate display regions of the CRT summary information concerning the control status of respective process areas, e.g. the display identified as Plant Alarm Summary Display in subsequent descriptive material herein. Other sections contain further sets of digital display data each representing detailed information concerning a corresponding area summarized in a respective region of the CRT display produced by the data from the one section containing summary information, e.g. displays referred to hereinafter as Area Alarm Summary Displays.

The sets of display data in the various memory sections also include display data for presenting along the lower edge of the screen, to identify the functions of certain variable-function keys on the keyboard 104, a variety of different symbols as will be explained hereinbelow.

When any set of display data from a selected memory section has been transferred to the refresh memory 176, the identity of that particular section is recorded in the central processor 120, e.g. in the portion thereof referred to as the display section identifier 178. This portion forms part of a display transfer means 180 which is jointly controlled by (1) certain display transfer keys of the variablefunction keys of the keyboard 104, and (2) the data stored in the section identifier 178. Thus, when any such key is pressed by the operat

TND-calls up the Quarter Screen TreND Display, with which the user can display real-time trends or playback historical trends, and from which the user can page to a Half Screen Trend Display.

TAG-calls up the Loop TAG Entry program, which allows a user, by keying in a 5 character Loop Tag, to randomly select a Loop Full Value Faceplate Display of any Loop in the system, without having to go through the hierarchical area-group-loop selection process.

SYS-calls up the SYStem Status Display, which allows a user to acknowledge system security alarms on the device level and provides the facility to connect/disconnect devices to/from the system.

LIA-Loop In Alarm.

GAK-Group non-critical Alarm AcKnowledge allows the user to acknowledge all non-critical alarms on a page at the Group Display Level simultaneously.

ACK-allows a user to silence horns in response to ACKnowledging process and/or system security alarms.

PEN-calls up Trend PEN Assignment Display, which allows the user to assign process variables to trend pens and to control the use of the pens from one of the consoles.

HTA-calls up Historical Trend Assignments Display, which allows the user to assign process variables to historical collection on disk.

LOG-calls up the LOGger program which provides the user with the option of printing one of the following summaries on the line printer: 1. Alarm Summary summary of important information about each loop currently in alarm; 2. Off-Alarm Summary summary of important information about each loop whose alarming is currently disabled; and 3. Off-Scan Summary summary of important information about each loop currently not being scanned.

DBC-calls up a Data Base Configurator program which allows a user the capability of configuring or modifying the configuration of the process data base for the system.

The layout of the variable function keys is, such that four dual-key positions are formed (second, fourth, seventh, and ninth key positions from the left). The dual-key sets provide a convenient means of selecting "sectors" of a CRT display.

Most displays appearing on the CRT screen are divided into eight sectors; the top half of the display comprises sectors one through four, and the bottom half comprises sectors five through eight. The four dual-key sets are used to select the corresponding sectors. For example, the left-most dual-key set is used to select sectors one and five, the next dual-key set selects two and six, and so on.

At the Loop Display Level (as will be explained more fully hereinafter), the dual-key sets are used for ramping selected values up or down. When a dual-key set is used for ramping, pressing the upper key increases the value, and pressing the lower key decreases it. Appropriate labels appear on the CRT display when variable function keys are used for ramping.

Display Hierarchy The operator's console presents several levels of information to the operator.

At the highest level displays are provided which present overview or summary information on a broad basis; whereas at the lowest level detailed information is provided on a much more limited section of the total operation. Figure 4 and subsequent figures related thereto illustrate examples of these displays in the categories of: 1. Plant Level Display 2. Area Level Displays 3. Group Level Displays 4. Loop Level Displays Using these four display levels, the operator may monitor major portions of the plant or, by simple keyboard manipulation, focus on a detailed fun'ction for review and/or adjustment. Adjustment of loop parameters takes place only at the Loop Level.

The four-level display hierarchy thus provides an orderly arrangement of information regarding the process under control of the operator. The following describes the overall features and general uses of the four levels of display.

Plant Level Display One display is available at the Plant Level: the Plant Alarm Summary. This display provides summary information on the total "plant" or largest section of a plant under control of a single operator. The display is divided into eight sectors on the CRT screen. (It may be noted that all of the process operations displays are organized in this manner). Each of the eight sectors represents one of eight plant "Areas", which is the next level of detail. Within an Area there may be up to eight "Groups" of control loops, listed by Group name. It is the purpose of the Plant Alarm Summary display to indicate the alarm status of each of these Groups within the Areas. A maximum of sixty-four groups may be listed (eight Areas eight Groups per Area). The alarm status of each group is indicated by intensification and flashing of the Group name. The flashing indicates an unacknowledged alarm; after acknowledgement, intensification signifies that an actual alarm condition still exists.

Area Level Displays Two displays are available at the Area Level to form the next level of operating detail: the Area Alarm Summary and the Area Full Value Faceplate. One of each of these displays is available for each of the Areas shown on the Plant Alarm Summary. The Area Alarm Summary displays up to eight Groups, one in each of the eight sectors on the CRT screen. Each Group may contain up to eight loops, which are identified by loop tag numbers. On this display alarms are related to loop level conditions by intensification and flashing of the loop tag number. In addition, the type of alarm is also listed alongside the loop tag in the form of a two-or-threeletter mnemonic code.

The second Area Display, the Area Full Value Faceplate, offers a graphic presentation of measurement and setpoint (or measurement only) for those loops for which this information is relevant. The organization of the Area Full Value Faceplate display is consistent with the arrangement of the associated Area Alarm Summary display (i.e., correspondence between Groups and their location on the screen). The loops listed top to bottom on the Area Alarm Summary are displayed left to right on the Area Full Value Faceplate display. For loops that are purely digital in nature, the analog bar is omitted.

Group Level Display One type of display is available at the Group Level: The Group Full Value Faceplate. This display combines both graphic and alphanumeric information to create a "faceplate" presentation for each of up to eight loops. The faceplate concept relates directly to the idea of emulating a controller faceplate on the CRT screen, but supplemented with digital data whuch provides precise values for the variables which appear in graphic form. Movement (change) and relativity of variables are observed on the graphics, while quantity and absoluteness are offered by the complementary digital presentation. Each of up to eight sectors on the display is occupied by one loop display. The loop display is divided, left and right, into two portions which are simultaneously visible. In general, the analog (graphic) information plus the loop tag are presented in the left (analog) portion, and digital information is presented in the right (digital) portion.

The vertical bar in the analog portion of the loop display graphically portrays measurement and setpoint information. The outer edges of the bar represent the setpoint value, and the inner portion or "fill-in" represents the measurement value.

The relative difference between the measurement and setpoint can thus be readily observed. The absolute values of the measurement and setpoint are portrayed in a relative manner by comparing inner and outer bar heights with the height of the display itself. A precise measurement value is provided by the digital portion of the loop display. The same general display format is maintained for all types of loops, whether analog or digital in nature, to maintain consistency of presentation.

Loop Level Displays Display at the Loop Level is attained when one of eight possible loops on the Group Full Value Faceplate display is selected. Once a particular loop has been selected, the digital portion (or "page") of that loop display may be replaced by a different digital page to obtain additional digital information about the loop. This replacement of the digital page is effected by the operator, using the variable function keys. The layout of each of these displays is similar to that of the Group Full Value Faceplate display (all eight loops are displayed simultaneously), allowing the operator to observe all loops in the Group while making adjustment to the selected loop.

The fact that a particular loop has been selected by the operator is indicated in three ways: 1. The digital page of the selected loop display is changed from the original Identification Page (this is the name applied to the digital page as it appeared on the Group Full Value Faceplate display) to one of the following pages: a. Primary Parameter Page; b. Secondary Parameter Page (not applicable to certain types of loops); c. Alarm Limits Page; and d. Output Memory Pointer Page.

2. Part of the digital page of the selected loop appears in reverse video format (black characters on white background), serving as a flag to the operator. The primary purpose of this reverse video is to indicate to the operator which loop variable is currently under direct keyboard control.

3. The variable function keyboard labeling (bottom row on CRT screen) has been changed from loop selection indicators (L/L) to labels pertaining to individual loop operations which may be performed by the operator.

The shared-display of this invention supports many types of loops. While loop information and format may vary with loop type, information of a similar type is presented in a consistent manner for all loops.

Three different techniques or methods are used to access the various displays.

This is a function of the display presently on the screen. The three can be categorized as ( I ) Vertical Selection, (2) Direct Access, and (3) Display Paging. The flow chart in Figure 6 shows the display access structure for the Process Operations Displays.

Vertical Selection This technique relates directly to the Area-Group-Loop structure of the displays and the physical orientation on the display. Variable Function Keys are provided which relate directly to these regions. The dual keys serve this purpose.

By pressing one of these keys the corresponding region is selected and the Area, Group or Loop currently displayed is thereby selected for the next level of detail.

This technique relies, then, on the physical orientation of information rather than some identifier such as loop tag. As each display is selected following a key depression, a new "keyboard" appears to provide the proper labeling for the next possible selection. At each level a key is provided to return to the previous level to avoid going all the way back to initializing the display from a Fixed Function Key.

These keys (the eight select and one return keys) allow for the continuous sequencing up or down through the display structure in a "vertical" manner. Each selection in a downward direction provides more detail on a chosen part of the process, whereas, in the upward direction the inverse is true-less information of a detailed nature but more of the process is made visible to the operator.

Direct Access An operator has the option of selecting a Loop directly by specifying a loop tag. Again, this procedure involves initialization from a Fixed Function Key (called "TAG") to provide the proper Variable Function Key labels. A five character tag (alpha or numeric for each character) is entered and the Group Full Value Faceplate containing that Loop is immediately accessed. Once at that level all functions available with the Vertical Selection technique are provided.

Display Paging At the Area, Group and Loop levels a form of "horizontal" selection is used to sequence through displays of the same type at each level. This feature is termed "paging" and involves the use of one or two Variable Function Keys to select consecutive displays-one display for each operation of a key. In all cases the displays are sequenced in a "wrap-around" fashion to provide continuous selection without the need to begin at any particular display.

Two paging schemes are employed at the Area level displays. One allows sequencing through all Area Alarm Summary Displays or Area Full Value Faceplate displays using the " < " or " > " key once either display type has been selected. At any point in the sequence the display type (Area Alarm Summary to Area Full Value Faceplate or vice versa) may be changed by operating the "AFF" or "AAS" keys. This second operation can be considered as a type of paging which accounts for the second scheme. Paging at the Area level is bi-directional for either scheme.

Paging at the Group level allows for sequencing through all Groups within the selected Area. Again, the " < " or " > " key is used to page in a forward or reverse sequence, respectively.

Once a Loop has been selected from a Group Full Value Faceplate display, paging is used to select one of up to four digital pages. Since each loop type has different amounts of data and parameters, the number of pages will vary from one to four. For example, the Secondary Parameter page applies to only the External Set Loop. Therefore, all others require three or less pages. Paging at the Loop level is uni-directional using the " > " key which is always the left most key on the Variable Function keyboard.

Figure 4 outlines the sequence of displays in the display hierarchy. Figures 4A, etc., present exemplary displays relating to an alarm condition in one loop, T225.

The Plant Alarm Summary of Figure 4A serves as an index to all Areas and Groups in the plant. The sole purpose of this display is to direct the operator to the Group in alarm. It does this by intensifying and flashing the appropriate Group name. This display also provides the following ancillary information: 1. Previous Area and Group Selected as indicated in the upper-left portion of the display. This serves as a memory device to the operator, allowing him to return to a previous Group or Area display to resume an operation which for instance he may have interrupted in order to examine an alarm condition.

2. Date: current month, day, year.

3. Time-of-day: In addition to being a convenient time indicator, this feature provides a visible Display Processor "heartbeat" indication. That is, if the Processor should stall or become "hung-up" for any reason, the seconds indication immediately ceases to increment, indicating to the operator that a Processor malfunction has occurred. Time is displayed in 24-hour format.

As shown in Figures 4B and 4C, Process Overview Deviation Displays consist of two separate displays each presenting information about one-half of the process.

The display presents the deviation between measurement and setpoint for all control loops. Each display contains four areas of eight groups. The deviation value for each control loop is normalized to the respective loop deviation limits. The deviation limits are represented by the upper and lower bounds of an inverted video block 190.

The condition of no deviation is represented by a dot in the center of the inverted video block. A positive deviation is represented by a vertical bar rising upward from the center of the block; a negative deviation by a vertical bar descending downward from the center. As the deviation limit is exceeded, the vertical bar is inverted to white on black.

The loop in alarm, T225, is in the BOILER Group. The Plant Alarm Summary alerts the operator to the existence of an alarm condition in the BOILER Group of the S02 Area by flashing the word BOILER on and off repeatedly. To obtain closer scrutiny of the alarm condition the operator selects, for display, the S02 Area. This is done by means of the variable function keys, which are labeled by the bottom row of characters on the screen. The A/A labels, positioned above the dual key positions of the variable function keyboard, indicate which keys are used to select the Areas. In this case, the S02 Area is selected by pressing the upper leftmost dual position key, which physically corresponds to the S02 Area on the screen. This action replaces the Plant Alarm Summary on the screen with the S02 Area Alarm Summary, Figure 4D.

The Area Alarm Summary Display lists all of the loops in each Group of the S02 Area. In the example given, only two Groups comprise the S02 Area, BOILER and COMPRESSOR. To the right of each loop tag number there appears an indication of any abnormal status associated with that loop. The following indicators may appear: 1. OFF -Off Scan, no values being scanned 2. NAL values scanned, not being alarmed (alarm inhibited) 3. IO -Hardware Device Error 4. LD -Low Deviation Alarm 5. HD -High Deviation Alarm On Scan, 6. LA -Low Absolute Alarm being alarmed 7. HA -High Absolute Alarm 8. BLANKS No Alarm 9. OOR -Out of Range In Figure 4D, if the S02 Area has an unacknowledged alarm condition, this is indicated by a flashing loop T225 tag number. Note that this tag number appears in the COMPRESSOR Group as well as the BOILER Group, indicating that this loop is related functionally to both groups. The presence of an acknowledged alarm condition can also be indicated by the intensified, steady ON state of the loop tag number, e.g. L118.

The Area Alarm Summary also contains a specific set of variable function key labels. The "caret" labels ( < and > ) denote an Area selection function implemented by pressing the associated variable function key to obtain sequential selection of all Area Alarm Summaries of the plant in a recycling sequence. A different Area display is presented for each momentary depression of the key. (In the display shown in Figure 4D, pressing the > key would bring up the FEED PREP Area and pressing the < key would bring up the LE UNIT Area.) The AFF label stands for Area Full Value Faceplate, it calls up the Area Full Value Faceplate display (Figure 4E). The key associated with the reverse video A/A label provides a convenient means of recalling the Plant Alarm Summary display.

To obtain a detailed view of the loop T225 parameters, the Group Full Value Faceplate for the BOILER Group is accessed. (Alternately, the COMPRESSOR Full Value Faceplate could be accessed as it, also contains loop T225). The BOILER Group Full Value Faceplate is accessed by pressing the upper left-hand dual-position variable function key, corresponding to the upper left-hand BOILER sector of the CRT display shown in the centre of Figure 4D.

Group Full Value Faceplate Display The Group Full Value Faceplate, showing detailed information on all loops in the BOILER Group, is shown in [the lower portion ofl Figure 4F. In the upper-left corner of the display the words S02 BOILER indicate that this is a display of the BOILER Group of the S02 Area. Note that several types of loops are represented in this particular Group: in the lower portion are a damper loop, a ratio loop, and a bias loop. The same general analog format is maintained for all loop types of consistency of display.

The variable function keyboard labeling has also changed from the previous display. The L/L labels indicate that a particular loop may now be selected for observation and/or manipulation. The paging keys ( < and > ) are used in the same manner as in the previous display, except in this case Groups rather than Areas are displayed in recycling sequence. The key associated with the reverse video G/G label provides a convenient means of recalling the Area Alarm Summary display.

In the analog portion of the T225 display a bar is used to graphically represent measurement and setpoint values. The outer edges of the bar represent the setpoint value, and the inner portion or "fill-in" represent the measurement value. The two small marks to the left of the bar are high and low absolute alarm limits. When the measurement value exceeds either of these limits (the fill-in of the bar rises above or falls below both marks) an absolute alarm condition exists. The horizontal line immediately to the right of the bar is an output indicator providing representation of the controller output value.

The two small marks to the right of the output indicator are termed "manual memory pointers" (see also Figure 10). These pointers serve no control or alarm function, but are provided to serve as a visual memory aid to the operator, who may adjust the pointers to represent a particular desired operating range. The letter "M" in the analog portion stands for Manual, indicating the current controller operating mode. (The letter "A" for Automatic appears when the controller is switched to the automatic mode.) The digital portion of the loop display provides a precise measurement value, an indication of the engineering units associated with that measurement value (DEGF), and the loop name. As discussed subsequently, additional digital information may be displayed for the selected loop, at the loop level. Selecting a loop is simply a matter of pressing the corresponding dual-position variable function key.

To summarize operations to this point, the variable function keyboard is used to progress from an overview of the entire plant (Plant Alarm Status Summary) to a detailed, functional display of the alarming loop. It took three steps: 1. From the Plant Alarm Summary, the alarming Area was selected.

2. From the Area Alarm Summary, the alarming Group was selected.

3. From the Group Full Value Faceplate Display, the alarming loop was n A t n n + n rt This brings us to the loop level, where we are ready to manipulate the required control parameters to correct the alarm condition. The following subsection describes the loop level displays.

Loop Level Displays Loop level displays for a typical loop (not loop T225) are shown in Figure 4G.

If the loop is in alarm condition, that fact is indicated by an intensified, nonflashing tag number. The variable function keys now relate to the selected loop, rather than to the Group in general. Key labeling (see also Figure 14) may include the following: 1. > (paging symbol) provides for the display of various digital pages. The digital pages are selected and presented in recycling sequence i.e., up to four pages are selected sequentially, one for each press of the > key.

2. OFF (Off Scan) allows the operator to remove the selected loop from the influence of the display, i.e. loop parameters will no longer be displayed and cannot, therefore, be manipulated from the console. This mode of operator/loop interface may be desirable, for example, during performance of loop repairs. When the loop is placed off scan, the word ON (for on scan) appears in this label position, indicating the action which can currently be taken by the operator.

3. AUT (Automatic) allows the operator to change the operating mode of the selected loop from manual to automatic. Once the loop mode is switched to automatic, the letters MAN (for manual) appear in this label position.

4. CLS (Close) allows the operator to fully close, with the press of the key, the final actuator associated with this control loop. (The output signal is instantly increased to full-scale value). Its counterpart, OPN, appearing several places to the right, provides for full opening of the final actuator.

5. +S- (Slow-Change Keys) provides a means of ramping the selected variable at a slow rate. The upper key of this dual-key set increases the value, and the lower key decreases it. The rate of change associated with this function provides for a full-scale variation in 25 seconds. A special "nudge" feature is included, which provides for a 0.1 percent change in the variable for each momentary depression of either key.

6. ASN (Assign) provides a means of selecting, for operator manipulation, a particular variable in the current digital page of the selected loop. The variables of the digital page are selected sequentially, in recycling sequence, and the selected variable appears in reverse video format on the CRT screen.

7. +F- (Fast-Change Keys) function similar to 5, above, but provide a faster rate of change: full-scale variation in 5 seconds. There is no "nudge" feature associated with the fast-change keys 8. OPN (Open) counterpart of CLS (See 4, above).

9. L/L provides a convenient means of recalling the Group Full Value Faceplate Display.

The variable function key labels are peculiar to the current digital page, as identified by the section identifier 178 and the functioning of the control means 181 will be jointly controlled by which display is identified, and which key has been pressed, so that the central processor will develop a uniquely corresponding function. When the Alarm Limits Page is accessed (by pressing " > "), a new display is presented, the key labeling will be changed to reflect operator actions which may be performed in conjunction with this new (Alarm Limits) digital page.

The DIS label signifies "Alarm Disable" and provides for disabling of the alarm function associated with this loop. When the alarm function has been disabled, ENA (signifying "Alarm Enable") appears in place of DIS. The +S- and +F- keys are used to adjust the high and low absolute alarm limits (HA and LA), the measurement/setpoint alarm deviation span (DV), and the alarm deadband (DB). These parameters are selected for adjustment by pressing the Assign (ASN) key.

When the Output Memory Pointer Page is accessed (by pressing > again) a new display is presented. The +S- and +F- keys are now used to adjust the High and Low Memory Pointers (HM and LM).

If loop T225 were of the External Setpoint (ESL) type, a fourth digital page would be available, termed the Secondary Parameter Page. The ESL loop provides a choice of setpoint sources, External Set or Operator Set; ESP and OSP keys associated with Secondary Parameter Page provide the means of switching from one setpoint source to the other.

An operator has the option of selecting a loop directly, by specifying a loop tag number. This is accomplished as follows (see also Figure 6): I. The "TAG" fixed function key is pressed, calling up the Loop Select Display; 2. Using the variable function, a five-character tag number is entered. At each character position, the operator has the choice of either entering the next character or canceling the entire entry using the "CAN" key; 3. Upon entering the fifth character, the loop and its associated Group appear on the screen.

Operator/Loop Interaction Operator/loop interaction involves the modification of loop parameters and operating modes. It is implemented through the loop level displays in conjunction with the variable function keys, through the control means 181 of the central processor 120, and the display section identifier 178. When a loop display is selected, only those functions associated with that particular loop type are made available to the operator. Also, only those functions that can logically be performed in that state of the loop are possible. For example if a loop has been switched to OFF SCAN, none of the functions which involve changing modes or parameters for that loop are provided.

To provide a specific illustration of the kinds of operator/loop interactions which are possible, examples are given below with respect to a specific type of loop referred to as an Operator Set Loop (OSL). Figure 9 outlines the basic elements of such a loop, from which it can be seen that the loop includes a conventional analog controller 200 receiving set and measurement signals (S, M), and producing an output signal (0) for an actuator 202 associated with the process. The measurement signal is developed in known fashion by a sensor 204, e.g. a differential-pressure instrument, or the like.

Interface equipment, generally indicated at 206, is

Primary Loop Control Primary loop control involves the adjustment of the primary loop parameters, e.g., setpoint and output for an Operator Set Loop. These parameters are adjusted using the Primary Parameter Page and the variable function keyboard ramp keys.

Figure 11 shows, in standard flow diagram format, the various actions which can be taken under specific conditions of an Operator Set Loop. When the controller is in automatic state, only the setpoint can be altered by the operator, through use of the ramp keys "S", or "F". When the controller is in manual state, either the setpoint or the output signal can be altered. In this case, the operator can select which is to be varied by actuation of the ASN key. For example, as shown in Figure 11, actuation of the ASN key, is indicated at 220, transfers the control states from "set point selected" to "output selected". A further actuation of the ASN key, as indicated at 222, will transfer the status back to "set point selected", the controller remaining in manual mode.

The particular variable which can be altered will be shown on the display page with a distinctive characterization, e.g., with a lighter video backgrund, relative to the other parameters displayed so that the operation will know at a glance which of the parameters is under control by the keyboard. When ever the controller is in manual mode, actuation of the AUT key (as labelled on the CRT) will switch the controller to automatic. The AUT key label will simultaneously change to MAN, so that the next actuation of that key will switch the controller back to manual.

Alarm Limits Adjustments The system alarm limit parameters for each loop (if applicable) are adjusted using the ramp keys along with the Alarm Limits display page. High absolute, low absolute, deviation, and deadband alarm limits are adjustable at any time independent of loop mode status. As described above, the ASN key is used to select one of the four variables to be ramped. An alarm enable/disable function is also provided to control alarming on a per loop basis. Figure 12 has been included to illustrate, in standard flow diagram format, the functions which can be performed in conjunction with the Alarm Limits Page.

Output Memory Point Adjustments The output memory pointers are displayed on the Output Memory Pointer Page for those loops for which these markers are applicable. They are adjusted in a manner equivalent to that described for alarm limit adjustments. The keyboard allows for these parameters to be varied at any time, independent of loop status or mode, as outlined in Figure 13. The ASN key is used to alternate selection between the high output pointer and the low output pointer.

Figure 14 sets forth for convenient reference the CRT keybarod labels for the variable function keyboard, for lack of the different controller words or conditions as indicated in the right-hand column.

Data Trending A Shared-Display system in accordance with this invention may include the capability of trending (i.e., sampling, collecting, and recording) analog data.

Analog measurement values held in the process data base can be trended using either real-time or historical trending modes.

In real-time trending, the data is sampled, conditioned and displayed to provide a continually updated chronology of data variances. In historical trending, up to 24 hours of data is sampled, conditioned, and stored in the disk memory for later retrieval and display. Up to 200 variables can be assigned to historical trending (continuous updating of up to 200 variables on the disk).

The process variable trends may be displayed either by CRT's or pen recorders. Using the CRT's, any six variables, whether real-time or historical, can be assigned for display, i.e., ready for instant display using the keyboard keys. Using the pen recorders, up to sixteen variables, real-time or historical, can be displayed concurrently.

Process Displays with Alarm Notification There are three types of process displays that include alarm notification: 1. Plant Alarm Summary display; 2. Area Alarm Summary display; 3. Group Full Value Faceplate display.

The occurrence of a new alarm affects each of these displays as follows: On the Plant Alarm Summary display the Group name associated with the alarming loop starts to flash. If, at this time, the Area associated with the flashing Group name is selected, an Area Alarm Summary will be displayed.

On the Area Alarm Summary display the loop tag of the alarming loop starts to flash on occurrence of an alarm. The specific alarm condition is also displayed, adjacent to the loop tag. The action of selecting the Area Alarm Summary stops the flashing of the Group name on the Plant Alarm Summary. The Group name is, however, intensified indicating that there is at least one alarm condition in the Group, but that the operator has addressed the alarming Area. If, at this time, the Group associated with the flashing loop tag is selected, a Group Full Value Faceplate display appears.

On the Group Full Value Faceplate display, the loop tag associated with the alarming loop flashes. If the alarm is the noncritical type, the flashing may be stopped by pressing the Group Noncritical Acknowledge (GAK) fixed function key. If, at this time, the loop is selected, the loop tag stops flashing and becomes intensified. The action of selecting the alarming loop also stops the flashing of the loop tag on the Area Alarm Summary.

Area Alarm Lights Up to eight Area Alarm Lights are located on the Console Control Panel above the CRT screen. These lights correspond to (up to) eight Areas displayed on the Plant Alarm Summary. Each light has a split-screen format, the upper half being red and the lower half orange. The red light flashes on occurrence of a new alarm condition associated with a particular plant Area. If, at this time, the Area Alarm Summary for this Area is selected for display, the red light stops flashing and remains lighted in a steady ON condition. When the loop which this alarm is associated with is selected, the orange light is lighted and remains in a steady ON condition. When the alarm condition no longer exists, both the red and orange lights are extinguished.

In Patent Application No. 8006932 (Serial No. 1,592,907) divided from the present application we claim an industrial process control system which performs a large number of process tasks distributed in respective areas of a process plant, each of said process tasks comprising a number of interrelated process loops arranged in groups according to respective process operations, said system including a digital display system for allowing an operator to examine the alarm status of each area, group or loop while continuously maintaining alarm integrity on all process loops, the system further comprising: an operator's console including a display device and a request-entry keyboard; format generation means which presents on said display device a hierarchical presentation of said process tasks by a succession of plant, area, and group level displays each in resonse to a specific keyboard request, each of said level displays being segmented such that respective portions of said display device identify particular operational sections forming the process level being displayed; said plant level display presenting to said operator summary information on each of said process area such that each segment of the display presents to said operator a listing of all groups forming a respective process area, each of said groups being further identified by a particular multi-character designator; each said area level display presenting summary information of a selected one of said process areas, said area level display further presenting in said segments identification of the groups comprising said selected area such that, within each of said display segments, there is presented information pertaining to all loops forming a respective process group of said selected area; each said group level display presenting summary information of a selected one of said area groups, said group level display identifying the loops comprising said selected group such that each display segment presents detailed status information pertaining to a particular loop of the selected group; means for compiling status information on each of said process loops independently of the particular display being presented; segment selection keys each spatially positioned relative to a respective one of said display segments, each of said selection keys presenting on said display device a more detailed representation of the selected segment as defined by the next succeeding level is the display hierarchy; means for comparing the status of each of said loops to respective preestablished conditions and, upon sensing a loop at variance with its respective conditions, for presenting on said display device an alarm condition designator; and wherein said alarm condition designator is presented in the display segment which corresponds to the loop in alarm regardless of the display level being presented and independently of changes in the position of said segment with changes in display level thereby allowing the operator to track an alarm indication from a higher order level display through more detailed displays of the loop in alarm by visually correlating the segment of interest and its respective segment selection keys.

Although several embodiments of the invention have been described herein in detail, it will be apparent to those skilled in the art that modifications of these embodiments can be made without departing from the scope of the invention as defined in the following claims.

WHAT WE CLAIM IS: 1. An industrial process control system used with a complex process, the system comprising means which measure the values of a large number of conditions in the process and means which receive the measurements and develop corresponding process control signals for elements such as valves and the like in the system, each combination of means which measure a condition and which develop a corresponding control signal defining a process control loop, said loops being organized in groups pertaining to respective process tasks; and said groups being clustered as distinct areas of the overall system; The system further comprising: an operator's console including a display device and a data-entry keyboard; a display memory for said display device containing digital data for continuously controlling the display on said display device; a digital storage memory comprising a plurality of storage sections each with a set of digital display data defining a corresponding complete display for said display device and arranged to be selectively transferred to said display memory to control the display on said display device; a first set of said digital display data serving to present in separate display sectors of said display device summary information concerning the control status of respective process areas; said summary information in each such sector comprising a listing of multicharacter group identifiers each designating a corresponding one of said process groups forming the respective process area; said digital storage memory having further sets of digital display data each representing detailed information concerning a corresponding area summarized in a respective one of said sectors of the display device produced by the digital data from said first set of said digital data; and display transfer means jointly controlled by preselected keys of said keyboard and by the storage in said display memory of any one of said sets of stored digital display data, and being operable by said presented keys, when one of said sets of stored digital display data has been placed in said display memory, to transfer to said display memory a corresponding one of said further sets of stored digital display data.

2. A system as in Claim 1, wherein said sets of digital display data each also includes display data for presenting symbols on said device in predetermined locations to identify the functions of preselected variable-function keys of said keyboard when the complete set of digital display data is presented on said device.

3. A system as in Claim 1, wherein each of said preselected keys is operable, when said first set of stored display data is in said display memory, to transfer to said display memory a corresponding one of said further sets of stored display data representing detailed information about a respective process area.

4. A system as in Claim 1, wherein one of said preselected keys serves a paging function such that when one of a correlated group of said further sets of display data is stored in said display memory, successive operations of said one preselected key will transfer, in predetermined sequential order, each of the other sets of said group of sets of data, including return to said one set of data, in a circular fashion.

5. A system as in Claim I, wherein said first set of digital display data comprises data presenting a summary of the alarm status of said process area.

6. A system as in Claim 4, wherein an alarm condition is indicated by a special characterization of the indicia identifying the process area in which an alarm condition has occurred.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (30)

**WARNING** start of CLMS field may overlap end of DESC **. conditions, for presenting on said display device an alarm condition designator; and wherein said alarm condition designator is presented in the display segment which corresponds to the loop in alarm regardless of the display level being presented and independently of changes in the position of said segment with changes in display level thereby allowing the operator to track an alarm indication from a higher order level display through more detailed displays of the loop in alarm by visually correlating the segment of interest and its respective segment selection keys. Although several embodiments of the invention have been described herein in detail, it will be apparent to those skilled in the art that modifications of these embodiments can be made without departing from the scope of the invention as defined in the following claims. WHAT WE CLAIM IS:

1. An industrial process control system used with a complex process, the system comprising means which measure the values of a large number of conditions in the process and means which receive the measurements and develop corresponding process control signals for elements such as valves and the like in the system, each combination of means which measure a condition and which develop a corresponding control signal defining a process control loop, said loops being organized in groups pertaining to respective process tasks; and said groups being clustered as distinct areas of the overall system; The system further comprising: an operator's console including a display device and a data-entry keyboard; a display memory for said display device containing digital data for continuously controlling the display on said display device; a digital storage memory comprising a plurality of storage sections each with a set of digital display data defining a corresponding complete display for said display device and arranged to be selectively transferred to said display memory to control the display on said display device; a first set of said digital display data serving to present in separate display sectors of said display device summary information concerning the control status of respective process areas; said summary information in each such sector comprising a listing of multicharacter group identifiers each designating a corresponding one of said process groups forming the respective process area; said digital storage memory having further sets of digital display data each representing detailed information concerning a corresponding area summarized in a respective one of said sectors of the display device produced by the digital data from said first set of said digital data; and display transfer means jointly controlled by preselected keys of said keyboard and by the storage in said display memory of any one of said sets of stored digital display data, and being operable by said presented keys, when one of said sets of stored digital display data has been placed in said display memory, to transfer to said display memory a corresponding one of said further sets of stored digital display data.

2. A system as in Claim 1, wherein said sets of digital display data each also includes display data for presenting symbols on said device in predetermined locations to identify the functions of preselected variable-function keys of said keyboard when the complete set of digital display data is presented on said device.

3. A system as in Claim 1, wherein each of said preselected keys is operable, when said first set of stored display data is in said display memory, to transfer to said display memory a corresponding one of said further sets of stored display data representing detailed information about a respective process area.

4. A system as in Claim 1, wherein one of said preselected keys serves a paging function such that when one of a correlated group of said further sets of display data is stored in said display memory, successive operations of said one preselected key will transfer, in predetermined sequential order, each of the other sets of said group of sets of data, including return to said one set of data, in a circular fashion.

5. A system as in Claim I, wherein said first set of digital display data comprises data presenting a summary of the alarm status of said process area.

6. A system as in Claim 4, wherein an alarm condition is indicated by a special characterization of the indicia identifying the process area in which an alarm condition has occurred.

7. A system as claimed in Claim 1, wherein said sets of display data are

arranged in multiple levels of information comprising at least first, second and third levels; said first level comprising a first set of display data representing summary information concerning the overall process control status; said second level comprising a plurality of second sets of display data each representing a more detailed exposition of a corresponding portion of the summary process information in said first level; said third level comprising a plurality of third sets of display data each representing a still more detailed exposition of a corresponding portion of the process information represented by one of said second sets of display data at said second level; said sets of display data further including symbol display data presenting indicia symbols on said device to identify the functions which will be performed by said variable-function keys if operated while the display is on the device.

8. A system as in Claim 1, wherein each of said further sets of digital data contains two subsets of data, one subset incorporating data for presenting in a first portion of the corresponding display sector graphic indicia reflecting the value of a process condition and the set point for that condition, the other subset incorporating data for presenting in a second portion of the corresponding display region, immediately adjacent said first portion, alphanumeric characters to provide precise numerical information concerning the control status of the corresponding loop; and display transfer means selectively controlled by said keyboard to transfer to said display memory any of said sets of stored digital data.

9. A system as in Claim 8, wherein said graphic insignia includes a vertical bar to show by its height the value of the measurement for the corresponding loop and wherein at least one vertical line adjacent said vertical bar indicates by its height the set point of the corresponding loop.

10. A system as in Claim 9, wherein said graphic insignia comprises, for indicating set point, two outer vertical lines contiguous with said vertical bar, whereby when the measurement is below set point, the two vertical lines are readily distinguishable by the open space therebetween, and when the measurement is above set point, the vertical measurement bar is readily distinguishable by its appearance of thinness relative to a supporting thicker base at a level representing the set point value.

I 1. A system as in Claim 9, wherein each of said sets of digital loop data incorporates information respecting a plurality of distinct loops which are presented in respective sectors of said display.

12. A system as in Claim 9, wherein said graphic insignia comprises, adjacent said vertical bar, two small marks indicating high and low absolute alarm limits.

13. A system as in Claim 9, wherein said graphic insignia comprises, adjacent said vertical bar, a horizontal line indicating the value of an output signal from a controller.

14. A system as in Claim 13, wherein said graphic insignia comprises, adjacent said horizontal line two small marks serving as manual memory pointers, to provide the operator with an adjustable representation of a desired operating range.

15. A system as in Claim 9, wherein said graphic insignia includes display of the letters A or M to indicate the automatic or manual states of the corresponding controller.

16. A system as in Claim 9, wherein said sets of digital data include data producing on said display, for each loop a portion alongside said graphic insignia.

17. A system as in Claim 2, wherein said variable-function keys are located along a generally horizontal line near the lower edge of said display device; each of said sets of digital display data including data for presenting on said display, adjacent the lower edge therof, symbols which are positionally correlated with at least certain of said variable-function keys and which provide information indicating the function to be performed by such positionally correlated key;

18. A system as in Claim 17, wherein said symbols presented on said display by certain of said sets of display data are correlated to only a selected number of said variable-function keys less than the total number thereof; said central processing unit being arranged to effect no function upon the actuation of any of the remaining keys identified by said symbols currently presented on said display device.

19. A system as in Claim 17, wherein said keys comprise a group of keys which individually are positionally related to respective regions of the display; said central processing unit being operable, upon actuation of any of said group of keys, to transfer to said display memory a new set of digital display data representing additional information pertaining to the information originally presented in the region of said display positionally related to the actuated key.

20. A system as in Claim 19, wherein said group of keys consists of four sets of dual keys spaced along said horizontal line, with the two keys of each set being located vertically adjacent one another, whereby the eight keys of the group correspond positionally to either regions of said display.

21. A system as in Claim 1, wherein said display transfer means selectively controlled by said keyboard to transfer to said display memory any of said sets of stored display data includes alarm status data associated therewith; and said keyboard includes means operable, when any of said sets of digital display data is in said display memory, to acknowledge said alarm status and thereby to effect changes in the indicia of at least certain of said displays.

22. A system as in Claim 21, wherein said storage memory includes sets of digital data serving to present on said display summary information concerning the control and alarm status of a plurality of said plant areas.

23. A system as in Claim 21, wherein each of said digital display data includes data operable when transferred to said display memory to product graphic presentations wherein an intermittent display of a portion of any of said graphic presentations indicate an alarm status in the process area, group, or loop corresponding to that portion.

24. A system as in Claim 21, wherein said sets of digital display data are arranged in a hierarchy of information wherein said loop data contains the most detailed exposition of process information; said acknowledgement means serving to change indications on said display of said alarm status only at the hierarchical level of information being presented and all those sets of digital display data exposing less detailed process information, preserving changed indications at lower levels of hierarchy for later retrieval upon returning to the lower level from higher levels in either the same area or group or different area or group without losing the location of lower level indications in higher level groups and areas or its status, acknowledged or unacknowledged, at the lower level.

25. A system as in Claim 24, including indicator light means adjacent said display and receiving said process loop data, said light means being positionally correlated with summary information when presented with respect to separate plant areas regardless of which of said sets of digital display data is in said display memory; said light means having two sections per light, one such section responding to any new unacknowledged loop alarm in said area by intermittently lighting in red, and the other indicating the existence of any acknowledged loop alarm for which alarm conditions remain, thereby resulting in constant indication of process alarm conditions and acknowledgement status for the entire process under the direction of the console, regardless of the level of display hierarchy on the display device at any time.

26. A system as in Claim 25, wherein said storage memory includes digital data for categorizing between critical and non-critical alarm status, said status being arbitrarily defined for any loop; said non-critical alarms being capable of being fully acknowledged at said group data hierarchical level; said critical alarms being fully acknowledged only at the loop hierarchical data level.

27. A system as in Claim 21, wherein said digital storage memory further comprises means for storing data indicating the time sequence of all alarm status conditions monitored; and means under the control of said keyboard, when any of said sets of digital display data is in said display memory, to selectively transfer to said display memory summary information in said storage sequence concerning each loop in said alarm status.

28. A system as in Claim 1, wherein said digital storage includes means for cumulatively storing data representing detailed measured information concerning a plurality of said loops; said display transfer means being operable by said keyboard to transfer to said display memory said cumulatively stored digital data to present a trend of past activity concerning at least one of said loops.

29. A system as in Claim 28, wherein said trend of past activity is presented on said display device.

30. An industrial process control system substantially as described with reference to the accompanying drawings.