JP3412667B2 - Scheduling method of fieldbus system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used to support a field bus system engineering operation .
The present invention relates to a scheduling method for a fieldbus system. [0002] Conventionally, a distributed control system has often been used for controlling a plant. The distributed control system has a configuration in which an operation monitoring station and a control station are connected to a communication bus, the control station is arranged in a distributed manner in the plant, and the plant is controlled by the control station under the supervision of the operation monitoring station. Recently, plant control using a field bus has also been tested for practical use. In plant control using a field bus, a field bus is laid in a plant, field devices are connected to the field bus, and the field devices communicate with each other to control the plant. In plant control using a fieldbus, control functions confined in a distributed control system can be distributed to fields. FIG. 12 is a diagram showing a configuration example of a distributed control system and a field bus. The part G in FIG. 12 is a distributed control system, and the part H is a fieldbus system. In FIG. 12, ICS is an operation monitoring station,
FCS is a control station, and 1 and 2 are communication buses. Reference numeral 3 denotes an input / output card (hereinafter, referred to as an IO card). Signals are input to and output from the plant via the IO card 3. SN and V are sensors and valves connected to the IO card 3. Detection signal of sensor SN is IO card 3
, And the operation amount given to the valve V is output from the IO card 3. Reference numeral 4 denotes a field bus card connected to the bus 2, reference numeral 5 denotes a field bus connected to the field bus card 4, and reference numerals 6 ₁ , 6 _2, ... In the illustrated example, a sensor is connected to the field device. The plant control by the distributed control system and the plant control by the field bus system are independently performed. Fieldbus systems can distribute control functions to the fields. FIG. 13 is a diagram showing a specific configuration example of a field bus system. 13 that are the same as those in FIG. 12 are given the same reference numerals. The field device ₆₁ function block B1 is provided for performing analog input. The field device 6 _2, function block B2 performs a PID operation, function block B3 perform analog output is provided. Two field devices ₆₁ and 62 function block ₂ has B1~B3
To construct a control system. FIG. 14 is a diagram showing a configuration image of the constructed control system. This control system is a control loop for performing feedback control. In such a control system, signal transmission between function blocks in different field devices is realized by communication between field devices. For example, signal transmission from the function blocks B1 to B2 is realized by communication between the field device ₆₁ and 6 _2. As described above, in the field bus system, function blocks are connected across different field devices to construct a control system. Therefore, in order for the control in the field bus system to be executed correctly, communication between the field devices needs to be performed efficiently. To do this, when the function block performs the processing,
Then, a scheduling operation is required to determine when to communicate the result to a function block in another field device. However, the conventional fieldbus system did not have a scheduling function. SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and has one control module.
Group as one group
Grouping the application blocks, and for each group
Sorting from input to output, each function
Time and communication with the
To schedule by assigning time
Accordingly, it is an object of the present invention to realize a fieldbus system scheduling method in which communication between field devices is performed efficiently and a control system constructed by connecting function blocks in different field devices can correctly perform control. . [0007] The present invention provides a scheduling method for a field bus system having the following configuration.
Is the way . A field bus is laid in the plant, field devices are connected to the field bus, function blocks for executing processing for control are mounted on the field devices, and the field is controlled by a control system constructed by combining the function blocks. It is applied to the bus system, the next hand by the scheduling means
Function block scheduling data in order
Of a fieldbus system characterized by generating
Scheduling method. (S1) Function block to be scheduled
The step of extracting (S2) Function block to be scheduled
Performing the ordering according to the following rules. (A) Function blocks that are related sequentially are grouped
Ping. At this time, one control loop is connected to one group.
And make (B) Sorting in the direction from input to output for each group
To do. (S3) Function stored in database memory
Refer to the maximum processing time of
Calculating the processing time of the block. (S4) A pair of function blocks in a connection relationship
And extract the function blocks in the order of input and output.
The process of forming a pair. (S5) Regarding communication stored in database memory
Calculating the communication time by referring to the parameters; (S6) Only when there is an execution order between groups,
Determining the order of execution. (S7) Time at which the function block executes processing
Assigning a time to execute communication with the server. The present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an apparatus for performing the method according to the present invention.
It is a figure showing an example . In FIG. 1, reference numeral 10 denotes a database memory, and reference numeral 20 denotes a schedule creation unit. The following information is stored in the database memory 10. Function block connection information Parameter values related to maximum processing time communication of function blocks These pieces of information are created by using a tool for constructing a field bus system. In the schedule creating section 20, reference numeral 201 denotes scheduling means, which is scheduling data for determining the timing at which the function block executes processing by using information necessary for scheduling stored in the database memory 10. This is referred to as processing scheduling data), and scheduling data for determining the timing at which the function block executes communication (this data is referred to as communication scheduling data) is generated. FIG. 2 is a diagram showing an example of a data format of process scheduling data, and FIG. 3 is a diagram showing an example of a data format of communication scheduling data. As shown in FIG. 2, the processing scheduling data includes a start time,
It consists of block tag name and processing time data. As shown in FIG. 3, the communication scheduling data includes a start time,
It consists of the tag name and parameter name of the source function block, the tag name and parameter name of the destination function block, and the data of communication time. Reference numeral 202 denotes data input means for inputting data defined by a user. FIG. 4 shows data input means 202.
FIG. 5 is a diagram showing an example of input data from a. As shown in FIG. 4, the input data includes version name, macro cycle, and time resolution data. 203 is a memory,
Processing scheduling data, communication scheduling data, and input data of the data input unit 202 are stored. Reference numeral 204 denotes a display unit, and the scheduling unit 201
The processing scheduling data and the communication scheduling data created in step are displayed. Reference numeral 205 denotes a generation unit which receives the scheduling data generated by the scheduling unit 201, converts the data into data of a data format set in each field device, and generates new data as necessary. When performing the scheduling as described above,
A two-stage generation process is performed in which the scheduling means 201 generates scheduling data, and then the generation means 205 generates data handled by the field device. This is because the user first generates the scheduling data in a format that is easy for the user to understand, and displays this on the display unit 204 so that the user can easily grasp the schedule and realize user-friendly operability. Reference numeral 206 denotes a correction unit which corrects and changes the scheduling data generated by the scheduling unit 201. Reference numeral 207 denotes a rescheduling unit which adjusts the timing to resolve the conflict when a schedule conflict occurs as a result of the modification by the modifying unit 206. For this adjustment, for example, the following processing is performed. Modified or changed elements leave their position on the time axis intact and avoid other competing elements. Revert a modified or changed element to its original state. Reference numeral 208 denotes a graphical data generating means.
The scheduling means 201 generates data for graphically displaying timing based on the scheduling data. The display unit 204 performs graphical timing display based on the generated data. An example of a graphical timing display will be described. FIG. 5 is a diagram showing a configuration example of the field bus system. In FIG. 5, 6 _n and 6 _{n + 1} are field devices. The field device 6 _n is provided with a function block B10 for performing digital input and a function block B11 for performing analog input. The field device _{6a + 1} includes a function block B12 for performing digital output, a function block B13 for performing PID calculation, and a function block B14 for performing analog output. FIG. 6 is a diagram showing an example of a graphical timing display for the field bus system of FIG. In FIG. 6, the horizontal axis represents the time axis. DO, D
I, AI, PID, and AO correspond to the function blocks B12, B10, B11, B13, and B14, respectively. L is the time during which the function block executes processing, M is the time during which the function block performs communication, and N is the communication time for other than control. The communication time for other than control is, for example, the communication time required to generate an alarm or to display trend data on a screen. By displaying the graphical timing as shown in FIG. 6, the user can easily grasp the schedule of each function block in the field device. The operation of the present invention will be described. FIG. 7 is a flowchart showing the flow of the entire scheduling operation. The operation will be described according to the order of steps in the flowchart. (S1) FBAP (Function Block A)
applicationProcesses) configuration. FBAP is a control loop group constructed by combining various function blocks. FIG. 8 shows the FB
FIG. 3 is a diagram illustrating an example of an AP. In FIG. 8, T1 and T2 are connection terminals for connecting the function block B2 to the function blocks in the distributed control system.
The signal transmitted from the function block in the distributed control system to the function block B2 passes through the connection terminal T1, and the signal transmitted from the function block B2 to the function block in the distributed control system passes through the connection terminal T2. (S2) A schedule creation screen is opened on the display unit 204. (S3) Data defined by the user is input by the data input unit 202. (S4) The scheduling means 201 generates scheduling data. (S5) Display the generated scheduling data on the display unit 2
04 is displayed. (S6) The generated scheduling data is converted into a data format set in the field device. (S7) It is determined whether the generated scheduling data is a satisfactory result. If the result is satisfied, the process ends. (S8) If the scheduling data is not a satisfactory result, the correcting means 206 corrects the scheduling data. (S9) As a result of the modification by the modification unit 206, if a schedule conflict occurs, rescheduling is performed by the rescheduling unit 207 to eliminate the conflict. FIG. 9 is a flowchart showing the procedure by which the scheduling means 201 generates scheduling data. (S1) A scheduling element is extracted. The scheduling element here is a function block. (S2) The scheduling elements are ordered. Here, the ordering is performed according to the following rules. Group elements that are related sequentially. At this time,
One control loop is one group. Sorting from input to output for each group. Alternatively, each group is sorted in the direction of the arrow connecting the elements. Separate backward pass. (S3) The processing time of each element is calculated. At this time, the maximum processing time of the function block stored in the database memory 10 is referred to. (S4) A pair of function blocks having a connection relationship is extracted. At this time, pairs of elements (function blocks) are formed in the order of input and output. The backward path is extracted only when it exists between different field devices. (S5) The communication time is calculated with reference to the communication parameters stored in the database memory 10. (S6) Only when there is an execution order between groups,
Determine the order of execution. The execution order is determined by the user. (S7) The time at which the element executes processing and the time at which communication is executed are assigned. Time is assigned according to the following rules. No communication allows time overlap. Execution of the processing in the function block allows time overlap only when the field devices are different. The temporal order of all elements and communications is guaranteed. (S8) Generate a timing table. The timing table is, for example, a graphical timing table as shown in FIG. The timing table does not include those for which the processing time and the communication time are zero. FIG. 10 is a flowchart showing a procedure for extracting and sorting scheduling elements.
FIG. 10 is a flowchart showing a specific procedure of the processes S1 and S2 in FIG. (S1) A scheduling element is extracted and an element list A
To be stored. The scheduling element at this time is a connection terminal for connecting the function block of the field device and the function block of the distributed control system. For example, it corresponds to the connection terminals T1 and T2 in FIG. (S2) It is determined whether there is an element. If there is no element, the process ends. (S3) One element is extracted from the element list A. At this time, the extracted element is deleted from the element list A. (S4) The extracted element (target element) is inserted into the element list Bn. Here, n is a positive integer starting from 1 and is a control loop number. (S5) The input / output element of the target element is extracted and inserted into the element list Bn. The inserted element is deleted from the element list A and added to the additional list 1. Of the extracted input / output elements, the input element is inserted immediately before the target element in the element list Bn, and the output element is inserted immediately after the target element in the element list Bn. . At this time, elements that already exist in the element list Bn are not inserted. (S6) The content of the additional list 1 is stored in the additional list 2,
Clear the contents of Addition List 1. (S7) It is determined whether or not there is an element in the additional list 2. (S8) When there is an element, the element (target element) is extracted from the additional list 2, and the extracted element is deleted from the additional list 2. (S9) If there is no element, the next control loop number n + 1
, An element list Bn + 1 is generated. Each of the lists described above is provided for temporarily storing data. Hereinafter, similar processing is repeated. FIG. 11 is a flowchart showing a procedure for assigning a time at which an element executes processing and a time at which communication is executed. FIG. 11 is a flowchart showing a specific procedure of the process S7 in FIG. In the processing S5 and S9 in FIG. 11, the time Tadd of the overlapping portion is given by the following equation. Tadd = (end time of overlapping element)-(start time of target element) In processing S10, a list such as (target element name, start time) is temporarily stored. The rescheduling procedure is almost the same as the procedure shown in the flowchart of FIG.
The following parts are different. The processes S1 to S6 in FIG. 9 use the scheduling data generated by the scheduling unit 201. In the process S7 of FIG. 9, the following restrictions are added. The “fixed” elements and communications are allocated at the times described in the scheduling data. "Fixed"
The corrected element is an element corrected by the correction unit 206. Once a modified element is easily modified, it becomes meaningless to modify it, so "fixed" elements are defined in this way. If a "fixed" element overlaps with something that must be processed before communication is performed, rescheduling is not possible. The fixing work itself has been violated. According to the present invention, one control loop is connected to one
As a group, function blocks that are sequentially related
Group the work. Input from each group
Sort in the direction of force. Each function block
The time to execute the process and the time to execute the communication
Assign. Schedule in this way
By performing the communication between the field devices efficiently,
Function blocks from different field devices
The control system built by connecting the cats controls correctly.
Fieldbus System Scheduling Method
The law was realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a configuration example of an apparatus for performing a method according to the present invention.
FIG . FIG. 2 is a diagram showing an example of a data format of processing scheduling data. FIG. 3 is a diagram illustrating an example of a data format of communication scheduling data. FIG. 4 is a diagram showing an example of input data of a data input unit. FIG. 5 is a diagram showing a configuration example of a field bus system. FIG. 6 is a diagram showing a graphical timing display example. FIG. 7 is a diagram illustrating the operation of the present invention. FIG. 8 is a diagram illustrating an example of an FBAP. FIG. 9 is a diagram illustrating the operation of the present invention. FIG. 10 is a diagram illustrating the operation of the present invention. FIG. 11 is a diagram illustrating the operation of the present invention. FIG. 12 is a diagram illustrating a configuration example of a distributed control system and a field bus. FIG. 13 is a diagram showing a specific configuration example of a field bus system. FIG. 14 is a diagram showing a configuration image of a constructed control system. [Description of Signs] 5 Fieldbus 61, 62, 6n, 6n + 1 Field devices B1 to B3, B10 to B14 Function block 10 Database memory 20 Schedule creation unit 201 Scheduling unit 204 Display unit 205 Generation unit

Claims (1)

(57) [Claims] [Claim 1] A field bus is laid in a plant, a field device is connected to the field bus, and a function block for executing a control process is mounted on the field device. It is applied to a field bus system for controlling a plant control system which is constructed by combining the blocks, the next hand by the scheduling means
Function block scheduling data in order
Of a fieldbus system characterized by generating
Scheduling method. (S1) Function block to be scheduled
The step of extracting (S2) Function block to be scheduled
Performing the ordering according to the following rules. (A) Function blocks that are related sequentially are grouped
Ping. At this time, one control loop is connected to one group.
And make (B) Sorting in the direction from input to output for each group
To do. (S3) Function stored in database memory
Refer to the maximum processing time of
Calculating the processing time of the block. (S4) A pair of function blocks in a connection relationship
And extract the function blocks in the order of input and output.
The process of forming a pair. (S5) Regarding communication stored in database memory
Calculating the communication time by referring to the parameters; (S6) Only when there is an execution order between groups,
Determining the order of execution. (S7) Time at which the function block executes processing
Assigning a time to execute communication with the server.