JP3307916B2 - Fieldbus system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field bus system, and more particularly to an industrial measurement and control system.
The present invention relates to a field bus system that operates strongly and stably against a failure in an instrument room and can easily perform a test run for a new system.

[0002]

2. Description of the Related Art A typical conventional system configuration will be described with reference to FIG. The fieldbus system is composed of an instrument room side and a field side. In the instrument room, a host device 51 for controlling and managing the entire system is provided.
A control block 52 is provided. The block 52 forms a control loop with the host device. The host device 51 and each block 52 are connected by a field bus 53. The connection configuration of the block 52 is a multi-drop configuration when viewed from the host device 51. An arithmetic / control unit 51a and a communication / bus control unit 51b are provided inside the host device 51.
And a power supply unit 51c. Also, each block 52
A transmitter 54 as a detecting end device and an actuator 55 as an operating end device are provided. 56 in each block 52 is a repeater.

In the system having the above configuration, the detection signal from the transmitter 54 is transmitted to the host device 51 by communication via the field bus 53, and the calculation / control unit 5
At 1a, a control signal is generated based on the detection data, and the control signal is transmitted to the actuator 55 via the field bus 53, and a required control operation is performed. If necessary, the actuator 55 returns an answer back signal to the host device 51 via the field bus 53.

[0004] Each of the above-described operations is performed on the host device 51 at appropriate timing by each of a large number of blocks. Therefore, various data from the host device 51 and each block 52 frequently flow through the field bus 53. The control of the data flow in the field bus 53 is performed by the host device 5.
The communication and bus control unit 51b executes the arbitration of the communication right between the components.

[0005]

In the configuration of the conventional field bus system, a digital distributed control system (DCS) as an upper device occupies an important position in communication and control execution, and a signal flow of the entire field bus is performed. It performs operations such as control and management / control of bus lines.
This configuration itself exists as an extension of the conventional measurement control system, and is considered to be a very natural system configuration.

However, the conventional system configuration has the following problems.

First, when controlling a loop including a detection end and an operation end, a higher-level device on the instrument room side intervenes in the calculation and control processing. The probability that the entire system does not operate and the entire system does not operate increases. That is, it has a characteristic that the entire system is weak against a failure on the instrument room side.

[0008] Second, in the new installation of the system, first install each local device, confirm its operation, and then install the upper device, connect the local device and the upper device, and check the operation of the entire system. To do. In general, the progress of construction differs for each block of field instruments, which are local devices, so it is time-consuming to complete the operation check of all field instruments and to check the operation by combining them with a higher-level device. Will be quite late. Until it is connected to a higher-level device, each field instrument must perform a test operation without a higher-level device. In this case, a simulator corresponding to the higher-level device is used. This simulator is of a real-time control, and is quite large. In addition, even if the operation confirmation by the simulation is successful, the actual operation is not sufficiently guaranteed, and the actual operation of the field device cannot be completely performed.

Third, if a failure occurs in a higher-level device or a communication path between a higher-level device and a field-side repeater is interrupted by noise, the entire system becomes uncontrollable and the system fails. It has the property of being weak against
In particular, the above system has a problem that a trouble is likely to occur in a communication path between a higher-level device and a field-side repeater.

Fourth, in a steady control state, the host device needs to receive and transmit communication data to the detection end and the operation end of each control loop at a response speed required for each control loop. Since some control loops have a low response speed, the communication load increases, and the load on the communication of the host device becomes extremely large.

A main object of the present invention is to solve the above-mentioned problems, and to provide an arithmetic and control unit for control provided in a higher-level device on the instrument room side on the field side or on each field side. It is installed for each block, and in the regular control operation, it is possible to control the operation of detecting and operating a large number of blocks on the field side without going through the upper device, and furthermore, it is possible to control each block independently or for each block Another object of the present invention is to provide a fieldbus system which can perform control by communicating with each other while controlling the system, thereby having high freedom and response at the time of system startup, and also having high operation reliability.

Another object of the present invention is to provide a field bus system which can operate stably and has a high operation reliability even if a trouble occurs in the instrument room without affecting the field side. It is to provide.

Another object of the present invention is to set and change a control parameter inside a calculation / control unit provided on the field side by a command from a higher-level device, and to control the higher-level device in an unsteady state. Thus, an object of the present invention is to provide a fieldbus system having a flexible structure as a system.

[0014]

The present invention is configured as follows to achieve the above object. (1) A host device arranged on the instrument room side, a plurality of detecting end devices and operating end devices arranged on the field side, and a bus line connecting the host device and the plurality of detecting end devices and operating end devices. And the detection end device and operation
End device, a resulting Ru fieldbus system power via the bus line, said detection end device, the process
Measures variables and sends digital measurement signals to the bus line
And outputs the digital signal on the bus line.
It generates a control signal by receiving the measurement signal, and a calculation and control unit for controlling the operation terminal device to the field side.

(2) Preferably, in the above (1),
The arithmetic and control unit is configured to detect the detecting end device or the operating end device.
It is provided in the room.

[0016] (3) Preferably, Oite in (1) above,
The host device receives the output signal of said detection end device and the arithmetic and control unit or these on the bus line, to monitor the detection state and control state of the field-side based on the output signal.

(4) Preferably, in the above ( 1) , between the host device and the bus line, and
Communication buffer is disposed field side position, the communication
Buffer has a communication abnormality detection unit, when an abnormality in control room side of the host device is arranged has occurred, to shut off the communication of the host device side and the field side in the communication buffer.

(5) Preferably, in the above (1 ), the arithmetic and control unit controls the operating end device.
And a memory for storing control parameters .

(6) Preferably, in the above (5), the control parameter stored in the memory is PI
This is a parameter as a D controller .

[0020] (7), preferably, in the above (5), a control parameter stored in the memory is set and changed by the previous SL-level equipment.

[0021] (8), preferably, in the above (5), a control parameter stored in the memory via the bus line, is set and changed by removable terminal.

[0022] (9), preferably, the (5) and have your <br/>, before Symbol calculation and control unit includes an adjusting unit for setting and changing the control parameter.

(10) Preferably, in the above (1 ), a bus control unit for managing communication on the bus line is provided on the field side.

(11) Preferably, in the above ( 1 ), a bus line of a device connected to the bus line
The source address is added to the output signal to .

(12) Preferably, the above (10 )
Oite to the bus control unit, the polling method or preparative
It is connected to the bus line by the
Control the communication of the connected device.

(13) Preferably, in the above ( 1 ), a plurality of arithmetic / control units connected on the bus line are provided.
The cascade control is performed by the control unit .

In the fieldbus system according to the present invention, a control operation / control unit conventionally provided in a higher-level device in an instrument room is arranged on the field side, and an operation / control unit is provided in each block. Thus, a control loop is formed only on the field side irrespective of the host device. Thereby, autonomy of the control operation on the field side is realized. Also, the relationship between the instrument room side and the field side,
Alternatively, control functions are distributed as in a relationship between a host device and each control block. As described above, when the process amount is detected by the detection end device of each block and is output as a measurement signal, the calculation / control unit in the block inputs the measurement value and the measurement signal and the control prepared inside the block. A control signal is generated based on the parameters, and the control signal is used to control and operate an actuator which is an operation end device.

Further, the same control operation is executed by a single arithmetic / control unit having the same function provided on the field side. In these configurations, no host device is involved in the control operation in the steady state. However, the host device executes a monitor function for predetermined contents. If necessary in an unsteady state, the host device can issue a control command to a control block on the field side.

Further, a communication buffer is provided on a bus line between the field side and the higher-level device on the instrument room side. This communication buffer basically has a function of shutting off the field side and the instrument room side, and when an abnormality occurs on the instrument room side by further providing a data abnormality detection unit inside,
It is possible to operate only on the field side. This ensures the operation stability of the system.

Further, a configuration in which a control parameter stored in an operation / control unit provided on the field side can be set and changed from outside is clarified. This setting / change
This is performed by a host device or a dedicated terminal.

Further, it is also possible to provide as an adjustment unit in the operation / control unit itself on the field side.

Further, in the system configuration according to the present invention, the control function is distributed to each control block on the field side, so that a control bus is provided on the field side for controlling communication between a plurality of control blocks and a higher-level device. It performs necessary communication control and performs smooth communication.

[0033]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a general configuration of an autonomous distributed fieldbus system according to the present invention. Here, the meaning of the term is clarified. "Autonomous" means that required control can be executed on the field side alone or for each control block on the field side, and "distributed" means that control functions are distributed in arbitrary units.
In practice, various arrangements of the field bus other than those illustrated can be considered.

The field bus system according to the present invention comprises:
The boundary 1 is divided into an upper instrument room side and a lower field side. An upper-level device 2 is disposed in the instrument room. The upper-level device 2 includes a CRT display device and a console, and further includes an arithmetic and control device that functions as a higher-level device. The arithmetic and control unit in the host device 2 monitors (measures and monitors) the devices on the field side during normal operation, and outputs control parameter setting / change commands and control commands to the field instruments only when necessary. I do. A large number of control loops 3 each constituting a field instrument are arranged on the field side. This loop corresponds to the blocks described in the conventional system configuration. Each loop has a configuration for a unique function assigned thereto, and includes a transmitter 4, an actuator 5, and an operation / control unit 6 disposed therebetween. The control function provided to the arithmetic and control unit 6 generally differs for each loop, and for example, a function as a PID controller is typical. The arithmetic and control unit 6 has a memory 6a, and stores control parameters and the like for defining control characteristics in the memory 6a. With this configuration, in each loop 3, the measurement value detected by the transmitter 4 is sent to the calculation and control unit 6, and the calculation and control unit 6 obtains a control value based on each control parameter. 5 to perform an operation for required control.

Reference numeral 7 denotes a field bus. The above-mentioned host device 2 and each loop 3 are connected via the field bus 7, and at the same time, between the loops 3 by the field bus 7 on the field side. A repeater 8 is arranged at the input / output end of each loop 3, and each loop 3 is connected to the field bus 7 via the repeater 8. Further, a communication buffer 9 is provided on a communication path between the host device 2 and each repeater on the field bus 7. The position of the communication buffer 9 is on the field side. Communication buffer 9
Are provided with data buffers 10 and 11 and an abnormal data detection unit 12.

On the field side, the field bus 7
, A power supply unit 13 and a bus control unit 14 are further connected via a repeater 15. The power supply unit 13 supplies power to the field bus 7. This is because the field instruments connected to the field bus 7 include a two-wire instrument. The bus control unit 14 arbitrates a communication request (communication right) arbitrarily output from a device connected to the bus line,
This is for managing the data flow in the field bus 7. The power supply unit 13 and the bus control unit 14 are arranged on the field side to enable autonomous control by the field side alone.

Next, the control operation of the field bus system having the above configuration will be described.

In each of the plurality of loops 3, the transmitter 4 measures a process variable, converts it into an electric signal (digital signal), and outputs the measured value through serial communication. The output signal is transmitted to the operation / control unit 6 in the loop, but is also output to the field bus 7 through the repeater 8 and transmitted to all devices connected to the bus line. In principle, the operation / control unit 6 existing in the same loop receives the measurement signal transmitted from the transmitter 4 and performs a predetermined operation based on the measurement signal to generate a control signal. To obtain this control signal, the control parameters prepared in the memory 6a are used as described above. The obtained control signal is given to the actuator 5 in the same loop, and a driving operation for a predetermined control is executed.

Thus, a single control loop is formed by the components in the loop 3 forming one unit. On the other hand, another field instrument may calculate a control signal required in its own loop by using a measurement signal transmitted from a loop other than its own.

The measurement signal transmitted from the transmitter 4 of each loop 3 to the field bus 7 is further supplied to the host device 2 through the communication buffer 9. The communication buffer 9 is for asynchronously performing communication between the higher-level device 2 and the field instrument. When a failure occurs in the higher-level device 2 or the communication path on the instrument room side, abnormal data appears.
This is to detect this, disconnect the host device 2 from the field side, and maintain the soundness of the control operation on the field side. The measurement signal output from the transmitter 4 of each loop 3 is transmitted to the higher-level device 2 via the field bus 7 as described above, but the higher-level device 2 transmits the measurement signal in the steady operation state as described above. And monitor its contents. In normal operation, host device 2
Only performs monitoring and does not directly output a control command to the actuator 5 of each loop.

As an unsteady operation in the host device 2, a control parameter is directly designated to the operation / control unit 6 of the loop 3 as necessary, or a control parameter set in the memory 6 a is changed. It is possible to directly output a control command. Since the host device 2 is provided with input means such as a keyboard input device, the values of various control parameters are usually input by the operator.

A signal relating to a control amount generated in the arithmetic and control section 6 and further given to the actuator 5;
And an actuator 5 that operates based on the control signal
The answerback signal, such as the valve opening, is transmitted from the arithmetic and control unit 6 to the host device 2 via the field bus 7. The host device 2 inputs the answerback signal and monitors the operation state in the loop.

A large number of loops 3, which are field instruments installed on the field side, each have a built-in operation / control unit 6, and the transmitter 4 is controlled in accordance with control parameters or control contents stored in a memory 6a of the operation / control unit 6. The control signal is obtained by performing an operation on the measurement signal from the control signal, and the control operation is executed based on the control signal. The control contents and control parameters used for calculation and the like in each loop 3 are changed according to the system status and purpose. This change can be made by the higher-level device 2 as described above, or by communication through a dedicated terminal 16 temporarily connected to the field bus 7 via a repeater as shown in FIG. It is possible. As for the change of the control parameters and the like, the calculation / control unit 6 of each loop 3 may be configured so as to incorporate a setting unit, and may be configured so that an operator directly sets the setting manually.

In the above description of the operation, it has been described that any one of the plurality of loops 3 performs the control operation and simultaneously transmits necessary signals to the host device 2, but each of the plurality of loops 3 is independent. Therefore, adjustment between loops is required. The data transmission timing on the bus line is controlled by the bus control unit 14. As the control form, any of a polling method and a token passing method can be used.

Next, a token passing method will be described with reference to FIGS. 3 and 4 as an example of a mode for controlling data transmission timing.

FIG. 3 schematically shows a field bus system. As an example, a host device 2, three loops 3, and a bus control unit (FBC) 14 are shown. In the figure, M is a calculation / control unit of the host device 2 as a master controller,
T1 to T3 are transmitters of the first to third loops, respectively, and C1 to C3 are first to third calculation / control units, respectively. Although not shown, the transmitter 4 is T1
ＴTn, and the arithmetic and control unit 6 is assumed to be C1 to Cn, respectively.

In the above configuration, the token positions controlled by the bus control unit 14 are T1, C1, T2, C2... Tn, Cn,
It is assumed that the patrol is performed in the order of M, T1,. Assuming that there is a token at the position of the transmitter T1, a measurement signal is transmitted from the transmitter T1 and transmitted to the arithmetic and control unit C1 and the arithmetic and control unit M of the host device 2 in the same loop. Calculation / control unit C1 based on the transmitted measurement signal
Performs the required calculations and controls the actuator. The arithmetic and control unit M of the host device 2 simply takes in the measurement signal.

Next, when the token position moves to the position of the operation / control unit C1, the operation / control unit C1 transmits the control amount obtained as a result of the operation to the operation / control unit M of the host device 2. In the same manner, T2, C2,...

In the configuration of the illustrated example, cascade control is performed in the case of the arithmetic and control unit C2. In cascade control,
The calculation and control unit C2 calculates the control amount based on the measurement value output from the transmitter T2. The control amount is transmitted to the calculation and control unit M of the host device 2, and the calculation and control unit C2
It is configured to be able to receive even one.

The operation / control section C1 receives the cascade setting signal from the operation / control section C2 and uses it as a signal for controlling the actuator connected thereto. Devices connected to the bus line are configured to receive all signals generated on the bus line.

Therefore, if the address of the transmission source is added to the signal on the bus line, it becomes possible for the operation / control section C1 to select and receive only the signal required by itself.

Similarly, each transmitter and each arithmetic and control unit repeat transmission and reception in that order.

When the token position reaches the operation / control unit M of the host device 2, the host device 2 outputs set values and control parameters to the necessary devices among the transmitters and the operation / control units. . Through the series of operations described above, the token makes one cycle, and the communication operation is executed again in a similar sequence.

The control cycle in the communication of the above-mentioned control system will be quantitatively described in comparison with the prior art as follows. The control cycle of the control system in the case of the present embodiment is Tc = n (Tt + Tn), where Tc: token cycle cycle, Tt; transmitter communication time, Tn; communication time of operation / control unit, n: field bus Is the number of loops connected to

In the configuration of the conventional control system, the control cycle is as follows. Tc = n (Tt + Tm + Tn) where Tm is the processing time of the host device.

As is apparent from a comparison between the two expressions relating to Tc, the configuration of the control system according to the present invention does not depend on the processing time of the higher-level device. Therefore, if the communication time is reduced, that is, the transmission speed is increased. If the message length is shortened, the response speed can be further increased. In addition, the control amount information and answerback signal transmitted from the arithmetic and control unit do not require much responsiveness compared to the signal related to the measured value, so the token occupation of the arithmetic and control unit relative to the transmitter is relatively small. It is possible to reduce the degree. In this case, the control cycle is Tc ≒ nT
t, which can be greatly improved.

In the above embodiment, the operation / control unit is built in each loop on the field side. However, the operation / control unit is not provided individually in each loop. As shown, a single operation / control unit 17 may be provided on the field side. In this embodiment, the other configurations and basic control operations are the same. Even in such a configuration, since the calculation / control section 17 is provided on the field side, it is a distributed type and has autonomy with respect to the instrument room side, as in the case of the above embodiment. In addition, it is very strong against failures that occur on the instrument room side and has operational stability.

That is, according to the present invention, if the control / arithmetic unit is disposed at an arbitrary position on the field side, it is of a distributed type and has autonomy to the measuring instrument side.

Therefore, in the present invention, a single control / arithmetic unit can be provided on the field side as in the above-described example, and the field instruments such as the transmitter 4 and the actuator 5 of each loop 3 have It is also possible to incorporate a control / arithmetic unit.

[0060]

As is apparent from the above description, according to the present invention, the operation / control device conventionally provided inside the host device is provided on the field side, and the power supply and the bus are inevitably related thereto. Since the control unit is also provided on the field side, the control operation can be performed only on the field side without interposing a higher-level device. Therefore, even if a trouble occurs on the instrument room side, stable operation can be performed only on the field side.

When a new system is installed, the system can be started up by configuring only the field side and setting control parameters using a temporarily connected dedicated terminal. In this state, if a higher-level device is installed and operation starts thereafter, integrated monitoring and operation of the entire system is possible from that point on, and a smooth system startup can be performed.

Further, the host device only monitors the operation state of the field device in the steady operation state, and can output a control command to the field device in the non-steady state. Setting and changing of the stored control parameters can also be executed, thereby increasing the flexibility of the system.

A communication buffer is installed on the field bus between the instrument room and the field, which causes disturbances such as external noise and crosstalk in the communication path between the instrument room and the field, making communication difficult. When an error occurs, the communication buffer detects an error and disconnects the host device from the field, thereby improving the reliability of communication and eliminating the possibility that an error in the instrument room affects the field. Can be. Therefore, the field side can maintain the soundness of the control operation.

Further, since the host device is not directly involved in the control operation that requires real-time responsiveness, the load on the host device is reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of an autonomous distributed fieldbus system according to the present invention.

FIG. 2 is a configuration diagram showing how to set and change control parameters of a calculation / control unit of each loop.

FIG. 3 is a configuration diagram for explaining a communication system.

FIG. 4 is a diagram showing a table showing token traversal and signal transmission destinations.

FIG. 5 is a configuration diagram showing an example of a conventional field bus system.

[Explanation of symbols]

 2 Upper device 3 Loop 4 Transmitter (detection end device) 5 Actuator (operation end device) 6 Arithmetic / control unit 7 Field bus 8, 15 Repeater 9 Communication buffer 13 Power supply unit 14 Bus control unit 16 ···Terminal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G05B 9/02 G05B 15/02 G05B 23/02 G06F 13/00 G06F 13/38

Claims (13)

(57) [Claims] 1. A host device arranged on the instrument room side, a plurality of detecting end devices and operating end devices arranged on the field side, and the host device and the plurality of detecting end devices and operating end devices are connected. A bus line, and the detecting end device
And operating tip device, a resulting Ru fieldbus system power via the bus line, said detection end device, the process variable is measured digital
Output to the bus line, and receive the digital measurement signal on the bus line.
A field bus system comprising: a calculation / control unit for generating a control signal to control the operating device by controlling the operating device on the field side . 2. The field bus system according to claim 1,
In the above, the arithmetic and control unit may be the detection end device or
A field bus system provided in an operating device . 3. The method of claim 1 Symbol placement field bus system, the host device receives the output signal of said detection end device and the arithmetic and control unit or these on the bus line, based on said output signal A fieldbus system for monitoring a detection state and a control state on a field side. 4. The field bus system according to claim 1 , wherein said field bus system is between said higher-level device and said bus line.
Communication buffer in the field-side position is arranged, the communication buffer has a communication abnormality detection unit, when an abnormality in control room side of the host device is arranged is generated, and the host device side in the communication buffer Field side
Fieldbus system comprising that you shut off the communication. 5. The field bus system according to claim 1 , wherein the arithmetic and control unit controls the operation end device.
A field bus system having a memory for storing a control parameter for the control . 6. The field bus system according to claim 5, wherein the control parameter stored in said memory is P
A field bus system, which is a parameter as an ID controller . 7. The field bus system of claim 5, wherein the control parameters stored in said memory, before <br/> Symbol field bus system, characterized in that it is set and changed by the host device. 8. A Fieldbus system according to claim 5, wherein the control parameter stored in the memory, the field bus system via the bus line, characterized in that it is set and changed by removable terminal . 9. The field bus system of claim 5 wherein, prior Symbol arithmetic and control unit, a fieldbus system, characterized in that it comprises an adjusting unit for setting and changing the control parameter. 10. The field bus system according to claim 1 , wherein a bus control unit for managing communication on the bus line is provided on a field side. 11. The field bus system according to claim 1 , wherein a bus line of a device connected to said bus line is provided.
Output signal to the
And a field bus system. 12. The field bus system according to claim 10 , wherein said bus control unit is configured to use a polling method or a polling method.
Connected to the bus line by token passing method
A fieldbus system for controlling communication of a selected device . 13. The field bus system according to claim 1 , wherein a plurality of arithmetic and logic units connected on said bus line are provided.
A field bus system wherein cascade control is performed by a control unit .