Abstract:
A method and apparatus for the integrated display of process events and trend data. The method and apparatus provide for a unified display of trend data and process events related to the control and/or monitoring of a manufacturing process. A workstation generates and displays a trend chart that represents values of one or more selected process parameters during a selected time window. The workstation also generates and displays an event table containing information describing process events that are related to the selected process parameters and that occurred during the selected time window.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit under 35 U.S.C. §119(e) of prior filed provisional application No. 60/100,286, filed Sep. 14, 1998 and entitled Methods and Apparatus for Integrated Display of Process Events and Trend Data which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates to computerized systems for controlling and/or monitoring manufacturing processes and, more particularly, to methods and apparatus for generating an integrated display of process events and trend data. 
   BACKGROUND OF THE INVENTION 
   Computerized systems for controlling and/or monitoring manufacturing processes, such as, for example, chemical processes, oil refining, production of pulp and paper, food processing and the like, are well-known in the art. Such systems typically include a network of computer workstations, process controllers and I/O subsystems. The I/O subsystems acquire process information from various sensors and other devices in the processing plant. The workstations organize the process information and present it to a user in a way that permits efficient control and monitoring of the manufacturing process. These systems may perform control functions, monitoring functions, or both. For simplicity, such systems are referred to herein as “process control” systems, despite the fact that they may perform control functions, both control and monitoring functions or only monitoring functions. 
   Process control systems typically manage both “current” process values (very recent measurements of temperatures, flow rates, pressures, tank levels, desired control set points, valve positions, motor states, etc.) and “historical” process values (measurements or control variable values associated with a specific time in the past). Typically, process data measurements and control variables may be represented by numerical values (e.g., 500 psi, 14.4 gallons per minute). However, some process measurements are more easily understood by process control system operators as words (e.g., OFF, OPEN, PV-HELLO) or strings of words (e.g., “sequence active”, “failed to open”). Process control systems typically include one or more applications that provide displays of numerical historical process values. Typically, these displays include a “numeric value vs. time” graph, often referred to as a “trend chart,” because the multi-segment line connecting the numeric values plotted as a function of time indicates the general direction of the measurement over the period of time represented on the display. 
   Process control systems also typically manage significant “process event” occurrence information. These process event occurrences record the fact that an event of interest occurred in the control system (e.g., an alarm state was detected, an operator changed the value of a control variable, a hardware fault was detected in the process control system, etc.) at a specific point in time. Process control systems typically include one or more applications that provide a display of process event information. Typically, this kind of information is printed on a logging printer soon after the event is detected. The process event information may be stored and can be displayed by applications that allow viewing of event records in various ways (e.g., ordered by time of occurrence and/or data filtering to display only those records that have certain properties or fields with certain values). 
   In prior art systems, separate process control applications must be used to display historical process values and process event records. This is a significant disadvantage to users trying to understand the operation of the system through examination of these two types of historical data. Even if the user has developed skills in the use of the individual applications, significant additional skill is typically required to manually coordinate and combine the information from the multiple applications to accurately answer questions about the behavior of the process control system. Typically, combining historical process values and event record information in a single view that can be printed and stored or used in correspondence with other process control personnel has required extensive computer skills with many applications. This has meant that this capability is beyond the ability of many process operators, and only highly trained process engineers can perform these tasks. Thus, the cause/effect relationship to process control is typically beyond the reach of process operators, and opportunities for making improvements in the process control system or in the standard operating procedures for a process plant are overlooked, or are too time-consuming to pursue. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the present invention, methods and apparatus are provided for displaying process information in a process control and/or monitoring system comprising a workstation having a display screen and a process history view application, a controller and an I/O subsystem. The workstation generates and displays on the display screen a trend chart that represents values of one or more selected process parameters during a selected time window, in response to user configuration of the trend chart. The workstation also generates and displays on the display screen an event table containing information describing process events that are related to the selected process parameters and that occurred during the selected time window. 
   The trend chart may be a graph of the selected process parameters as a function of time. The event table may be automatically generated and displayed upon configuration of the trend chart by the user. The trend chart and the event table may be displayed simultaneously on the same display screen to form an integrated process history chart. 
   Preferably, event markers of the process events in the event table are displayed on the trend chart. The event markers may comprise event names at points on the trend chart corresponding to the time of each event. 
   The user may configure the trend chart to display different time windows, different process parameters and different numbers of parameters. In each case, the process history application in the workstation automatically retrieves the process data from the appropriate data source, determines the data type for the trend chart and automatically retrieves event records to be displayed in the event table. 
   Trend chart configurations may be stored for later use. When the stored trend chart configuration is selected by the user, the process history view application automatically retrieves the required process data and process event records in order to generate the trend chart and the corresponding event table. 
   The process history view application provides the ability to establish filter criteria for events to be displayed in the event table. The user may select event types and categories for display. In addition, the user may select events from certain areas, nodes and modules of the process control system. In each case, the selected events, according to the filter criteria established by the operator or in accordance with default filter criteria, for the selected time window are displayed in the event table. The user may change the filter criteria in order to add process events of possible interest or to remove process events that are not of interest. 
   As indicated above, the trend chart preferably includes event markers that indicate the occurrence of events at specific times during the selected time window. The user may select one of the events on the trend chart, such as by positioning a cursor on the event marker of interest and clicking a pointing device. In response, the process history view application scrolls the event table to the selected event, if necessary, and highlights the selected event. This permits the user, for example, to determine the details of an event that occurred at a particular time in the trend chart, such as when a change occurred in one of the process parameters. Alternatively, the user may select an event in the event table. In response, the process history view application highlights the selected event marker in the trend chart. This function permits the user to easily correlate changes in process parameters with process events. 
   The process history view application therefore provides a high degree of integration and interaction between the trend chart and the event table. The user can easily determine relationships between trend data and process events. 
   In another embodiment, a graphical user interface for displaying trend and event data related to the operation of a process is disclosed. The interface includes first and second portions. The first portion is configured to display at least one trend graph that displays trend lines representative of at least one parameter associated with the process. The second portion configured to display information about at least one process event. The interface also includes event markers related to the at least one process event and displayed on the first portion. 
   In another embodiment, a system for monitoring a process is disclosed. The system includes an event database containing event records related to the process, a trend database containing historical trend data related to the process, and means for simultaneously displaying a trend graph representing at least a portion of the historical trend data and a table representing at least a portion of the event records. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is made to the accompanying drawings, which are incorporated herein by reference and in which: 
       FIG. 1  is a block diagram of the hardware components of an example of a process control system; 
       FIG. 2  shows an example of a process history chart that may be displayed on a display screen of the workstation in the process control system; 
       FIG. 3  shows another example of a trend chart that may be displayed in the process history chart of  FIG. 2 ; 
       FIGS. 4A–4D  show dialog boxes for configuring the trend chart in accordance with the invention; 
       FIGS. 5A–5F  show dialog boxes that may be used for selecting process event filter settings; 
       FIG. 5G  shows a dialog box that may be used for establishing the order of events in the event table; 
       FIG. 6  is a pictorial representation of the interaction between the process history view application and other modules in the workstation; 
       FIG. 7  is a flow chart that illustrates opening of an existing process history chart; 
       FIG. 8  is a flow chart that illustrates configuration of a new process history chart; and 
       FIG. 9  is an example of a trend chart wherein ASCII data is displayed. 
   

   DETAILED DESCRIPTION 
   A block diagram of an example of a process control system suitable for implementation of the present invention is shown in  FIG. 1 . A workstation  10  is coupled to a primary control network  12 . The primary control network  12  is coupled by a primary hub  14  to a process controller  16  which controls an I/O subsystem  20 . The I/O subsystem  20  is connected to and acquires process information from process sensors and other devices in the processing plant. The workstation  10  may have the capability to access controller  16  through a secondary control network  24  and a secondary hub  26 . It will be understood that a typical process control system includes a plurality of workstations, control networks, hubs, controllers and I/O subsystems connected together in a network configuration. 
   A typical workstation  10  may comprise a PC running Windows NT and having a 3 gigabyte hard drive, 128 megabytes of main memory and a printer. It will be understood by those skilled in the art that a variety of different workstation configurations may be utilized within the scope of the invention. 
   The present invention relates to application software that is implemented in one or more of the workstations in the process control system. The application software coordinates and processes trend data and process events acquired by the control system to produce a unique and advantageous display on the workstation display screen. The application software, known as the process history view application, is preferably implemented in the C++ programming language, but may be implemented in other programming languages within the scope of the invention. 
   An example of a process history chart  50  in accordance with the invention is shown in  FIG. 2 . The process history chart may occupy all or a part of the video display screen of workstation  10 . The major components of process history chart  50  include a trend chart  52  and an event table  54 . A legend  56  is associated with trend chart  52 . The legend  56  provides information concerning each parameter that appears in trend chart  52 . A menu bar  58  permits user selection of various functions associated with process history chart  50 . As described below, trend chart  52  and event table  54  are integrated together, and changes in one display element are automatically reflected in the other element of the display. 
   Trend chart  52  is a representation of the values of one or more process parameters over a selected time window. Trend chart  52  may comprise a graph of the values of one or more selected process parameters as a function of time over the selected time window. In the example of  FIG. 2 , trend lines  60 ,  62  and  64  represent the values of three process parameters over a period of several hours. Three Y-axis scales correspond to trend lines  60 ,  62 , and  64 , respectively. The Y-axis scales may be correlated to the respective trend lines, for example, by color. In one embodiment of the process history view application, up to eight process parameters may be displayed on the trend chart  52 . The time window of the trend chart may be selected by the user. The time window may be a selected historical time span or may extend from a selected time to the present. When the trend chart extends to the present, the operator may observe the trend lines as corresponding process parameter values are acquired by the process control system. Legend  56  provides information as to each of the process parameters that appear in trend chart  52 . 
   Event table  54  includes a listing of process events that occurred during the time window of trend chart  52  and which are retrieved for display in accordance with operator selected filter settings or default filter settings. Event records may include different information in different processing plants. In one embodiment, event records include a date and time  70 , an event type  72 , a category  74 , an area  76 , a node  78  and a module  80 . The categories may, for example, include “instrument”, “process”, “system”, and “user”. The area may indicate the area in the plant where the event occurred. The node may indicate the name of the network node where the event was detected. The module may indicate a software module. Additional information may be included in the event records. Examples of such information include parameter, state, level and descriptive fields. The event table is typically organized as a spreadsheet and is typically sorted in chronological order. Other sorting criteria may be selected, if desired. 
   Referring again to  FIG. 2 , the trend chart  52  preferably includes event markers  90 ,  92 , etc. Each event marker may comprise a word indicating the event type and a line that points to the time on the X-axis time scale when the event occurred. Only those events which appear in event table  54  are indicated on trend chart  52 . The event markers  90 ,  92 , etc. enable the user to easily correlate a change in one of the trend lines  60 ,  62 ,  64  to an event, or vice versa. 
   The process history chart may include menu bar  58  for selecting a variety of functions relating to the chart. The menu bar may, for example, include buttons for opening a new process history chart, opening an existing process history chart, saving a process history chart, printing the current process history chart, opening the edit filters dialog box, and the like. 
   A second example of a trend chart which may be incorporated in the process history chart of  FIG. 2  is shown in  FIG. 3 . A trend chart  100  comprises graphs of two process parameters as a function of time. Trend lines  102  and  104  are plotted over a selected time window of approximately ½ hour (X-axis time scale from 8:30 to 8:55). The Y-axis is divided into two separate scales so that trend lines  102  and  104  are vertically separate from each other. In one embodiment, the trend chart may have up to six separate Y-axes. Event markers  110 ,  112 , etc. correspond to events in the event table  54 , as described above in connection with  FIG. 2 . Each event marker includes a word  114  that indicates the event type and a line  116  that points to the time of occurrence of the event on the X-axis time scale. 
     FIGS. 4A–4D  show “configure chart” dialog windows for user configuration of the trend chart in the process history chart in accordance with the invention. A configure chart window  150  shown in  FIG. 4A . permits the user to add process parameters to the trend chart and to delete process parameters from the trend chart. In the example of  FIG. 4A , process parameters  152 ,  154  and  156  are selected. For each selected process parameter, the user may specify whether a new Y-axis is desired (see  FIG. 3  which shows two Y-axes). A time scale selection window  160  is shown in  FIG. 4B . The user may select a time window by specifying the “time start”, the span and the “time end”. In addition, the user may specify the update rate of the process parameter values. A window  170 , shown in  FIG. 4C , permits the user to specify multiple Y-axes. The percentage of the total Y-axis occupied by each parameter value is specified. In the example of  FIG. 2 , a single Y-axis occupies 100% of the available space. In the example of  FIG. 3 , two Y-axes each occupy approximately 50% of the available space. A window  180 , shown in  FIG. 4D , permits the user to individually configure the trend line corresponding to each selected process parameter. The user can, for example, specify whether the Y scale is shown, whether events corresponding to the process parameter are shown and can define Y scale limits. It will be understood that a variety of different trend chart configuration options may be specified in accordance with the present invention. The characteristics shown in  FIGS. 4A–4D  and described above, as well as additional trend chart characteristics, may be selected by the user. 
   When the trend chart has been configured by the user, the process history view application automatically locates and retrieves the data values needed to generate and display the trend chart. In addition, the process history view application automatically locates and retrieves the process event records to be displayed in the event table. The process event records to be displayed in the event table are retrieved in accordance with selected filter settings. Preferably, process events that occurred during the time window specified for the trend chart and which are related to the process parameters in the trend chart are displayed. The process events to be displayed in the event table of the process history chart may be defined by default filter settings or by user-selected filter settings. Default filter settings may, for example, include the time window of the trend chart and those events that occurred in the same process control system module as the process parameters displayed in the trend chart. 
   Examples of dialog boxes which permit the user to select filter settings are shown in  FIGS. 5A–5F . In each case, the user selects process events for display in the event table. Typically the events are selected as providing information that may be useful in connection with the trend chart. Referring to  FIG. 5A , a dialog window  200  permits the user to select one or more event types for display in the event table. Dialog window  200  includes a menu bar  202  for selection of the process event characteristic of interest. In the illustrated example, process event characteristics include event type, category, area, node, module and other columns. Dialog window  200  further includes a browse list  208  and a filter list  210 . Browse list  208  contains a list of items for selection by the user. Filter list  210  contains the items that have been selected by the user. In the example of  FIG. 5A , event types include alarm, change, download, event and status. The user selects one or more event types and places them in filter list  210 . The selected event types will then be displayed in the event table of the corresponding process history chart. A dialog box  220  for selection of event category is shown in  FIG. 5B . Categories in the browse list include instrument, process, system and user. A dialog box  230  for selection of event area is shown in  FIG. 5C . The event area may be a physical area of the manufacturing plant. A dialog box  240  for selection of one or more nodes is shown in  FIG. 5D . Each node is a network node connected to a workstation or a process controller. A dialog box  250  for selection of modules is shown in  FIG. 5E . Each module represents a software module in a workstation or a controller. A dialog box  260  for selection of other event characteristics in the event record is shown in  FIG. 5F . The user may specify that events having selected characteristics be displayed in the event table. 
   A dialog box  270  shown in  FIG. 5G  permits the user to specify the arrangement of the event records in the event table. Thus, for example, events may be sorted by event type or node. Typically, events are listed chronologically by date and time, according to a default setting. 
   A schematic diagram showing the relationship between the process history view application  300  and other components of workstation  10  is shown in  FIG. 6 . As indicated above, the process history view application  300  automatically retrieves event records from an event database  302  and retrieves historical trend data from a trend database  304  in accordance with the user-specified configuration of the process history chart. Real-time trend data, that is current trend data, is retrieved from a runtime database  306 . A registry  310  contains application settings and user preferences. For example, the user may specify font type and font size to be used in the process history view and may specify the way that time is indicated on the trend chart. User-created process history charts may be saved in chart file  316  for later use. The file contains information concerning the trend chart configuration and the filter settings. When the saved chart is later opened, the required trend data and process event records are automatically retrieved and inserted into the chart, so as to generate the required display. In addition, module trend charts may be stored in a chart file  318 . 
   A flow chart illustrating opening of a previously-configured process history chart is shown in  FIG. 7 . The process history view application is indicated to be running in step  350 . In step  352 , the user selects a chart file, and the file is opened. For each process parameter specified by the trend chart configuration, the trend data is automatically retrieved from the appropriate source, such as the trend database  304  or the runtime database  306 , and the data type, integer, floating point or ASCII, is automatically determined. In addition, the process event records are automatically retrieved from the event database  302 . The requested process history chart is then generated without further action by the user. A flow chart of a process for configuring a new process history chart is shown in  FIG. 8 . With the process history view application running, as indicated in step  350 , the user selects a process history chart in step  360 . The configure chart dialog box, shown in  FIGS. 4A–4D  and described above, is displayed. The user configures the trend chart in accordance with required parameters. For each selected process parameter in the trend chart configuration, the application automatically retrieves the required trend data from the trend database  304  or the runtime database  306  and determines the data type. The user may establish filter settings or may utilize the default filter settings for event records. The event records according to the selected filter settings or the default filter settings are automatically retrieved from the event database  302 . The process history chart is then displayed in accordance with the selected configuration and filter settings. 
   An example of a trend chart wherein ASCII strings represent process parameter values is shown in  FIG. 9 . Trend lines  400  and  402  indicate process parameter numerical values as described above. A trend line  410  indicates process parameter values in ASCII format. In particular, trend line  410  represents a process parameter as MAN (manual) or AUTO (automatic). Initially, trend line  410  indicates a parameter value of MAN. At a time indicated by a marker  412 , the parameter value changes to AUTO. Then at a time indicated by a marker  414 , the parameter value changes to MAN. In general, the ASCII trend line format uses two or more ASCII strings to indicate parameter values and uses markers to indicate the times when the parameter values change. 
   While there have been shown and described what are at present considered the preferred embodiments of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.