JP2000047715A - Communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make connectable a slave device, which has a slow response speed, to a master station while maintaining a high-speed communication by sending alternative data back to the master station within the reception permissible time of the master station side without waiting for corresponding communication answer data to have been generated when the communication answer data do not have been generated after a request from the master station arrives. SOLUTION: The slave device 2 has a communication answer buffer function 2d of sending alternative data back to the master station 1 within the reception permissible time of the master station side 1 without waiting the communication answer data to have been generated if the corresponding communication answer data do not have been generated on the side of the slave device 2 when a remote I/O request arrives from the master station 1 through a communication line T. An inverter communication part consists principally of a communication CPU 2b and a remote I/O communication answer buffer 2d. Through the operation of this inverter communication part, remote I/O communication answer buffer data are sent back at short intervals so as to match communication cycles of high-speed response irrelevantly to the operation of an inverter internal process CPU 2c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, connecting a master station including a PLC as a control center and one or more slave stations as input / output devices via a high-speed communication network to exchange various control data. The present invention relates to a communication device suitable for a PLC system or the like which realizes a desired control specification while performing
In particular, the present invention relates to a communication device that enables a slave station having a slow processing speed to join a high-speed communication network without lowering the overall communication speed.

[0002]

2. Description of the Related Art A master station including a PLC, which is a control center, and a remote slave unit including input / output devices are connected via a communication line, and various input / output data are transmitted and received between the master station and each slave station. By doing so, control systems that achieve desired control specifications are widely used in large-scale production lines in factories and the like.

The communication lines of this type of control system include:
Various slave units such as an I / O link unit, a remote I / O terminal, a remote adapter, a sensor terminal, an analog terminal, a temperature sensor terminal, an inverter, and an environment-resistant terminal are selectively connected. When receiving any command from the master, the slaves can immediately return a response to the command (hereinafter referred to as a slave having a high response speed). Otherwise, a response cannot be returned (hereinafter, referred to as a slave having a low response speed). A typical example of the former is a remote I / O terminal, and an example of the latter is an inverter. Here, as is well known, an inverter is a device connected to a communication line connected to a master station, and is a control device that controls rotation of a three-phase induction motor or the like in response to a command from the master station. It is. From the master station to the inverter as a slave unit, commands such as rotation speed, normal rotation / reverse rotation, and start / stop are given as commands. From the inverter to the master station, the actual rotation corresponding to those commands is given. The mode (rotational speed, normal / reverse, start / stop, etc.) is returned as a response.

In a conventional control system employing a relatively low-speed communication system, a remote I / O between a PLC constituting a master station and an inverter constituting a slave station is provided.
The state of the O request and the response processing to the O request are schematically shown in the flowchart of FIG. In the figure,
First, the PLC constituting the master station has a remote I / O
The request is transmitted to the inverter (Step 501). Next, the inverter communication unit constituting the slave station receives the remote I / O request via the communication line, and passes the received remote I / O request to the inverter internal processing CPU (step 502). Next, the inverter internal processing CPU constituting the slave station executes a process according to the remote I / O request received from the inverter communication unit. In this process, after the three-phase induction motor, which is a load, is started, its rotation speed is increased to a designated rotation speed (step 503). Next, when a certain processing time elapses, a predetermined monitoring circuit or the like operates to generate a response to the remote I / O request. This response includes, for example, frequency information of the output power source, forward / reverse rotation information of the connected motor, abnormal state of the motor (overcurrent, overvoltage, overload, overheating, etc.), warning information (simultaneously with the forward rotation command and A rotation command has been input, etc.). The response to the remote I / O request thus obtained is handed over to the inverter communication unit (step 504). Next, the inverter communication unit transmits a response corresponding to the received remote I / O request to the master station (step 505). Then, the PLC constituting the master station receives a response corresponding to the remote I / O request (step 506). Thereafter, the processing of steps 501 to 506 is repeated.

As apparent from the above description, in the conventional data processing procedure performed between the PLC constituting the master station and the inverter constituting the slave station, a series of consistent data processing is performed inside the inverter. After that, a response corresponding to the remote I / O request is returned to the master station. In other words, when the remote I / O request arrives from the master station via the communication line at the slave station side, if the corresponding communication response data has not been generated at the slave station side, the communication response data is not generated. After the completion of the generation, the communication response data whose generation has been completed is returned to the master station. Therefore, on the side of the master station, taking into account the data processing time on the side of the slave station, there is a sufficient communication processing time between the transmission processing shown in step 501 and the reception processing shown in step 506. Is secured.

[0006]

Recently, this type of PLC has been proposed.
In the system, there is a demand for faster input / output responsiveness in each slave station. Similarly, higher-speed communication systems are also required. One of them is:
There is a communication method based on Device Net, which is an open network proposed by AB (Arlen Bradley) of the United States. In the flow of such high-speed operation, the inverter device as a slave station is affected by the responsiveness of the induction motor to be controlled, as described above. There is. That is, even if the responsiveness of the inverter alone is increased, the responsiveness of the induction motor is very slow, so that there is not much effect. For this reason, development of this type of inverter device has been focused on cost reduction rather than high-speed response.

For this reason, if an inverter device having a low response speed participates in a control system in which several slave units whose response speed is increased by a high-speed communication line are joined, the processing speed of the master station becomes higher. Furthermore, it was found that the inverter internal processing could not respond and the master station side timed out, or the inverter could not respond to continuous transmission from the master station, and the inverter internal processing overflowed and communication became impossible. In order to avoid such a situation, the performance of the PLC master station should be reduced (by setting the processing time to be slower) or the processing speed of the inverter should be reduced in accordance with the inverter device having a slow response speed. More irrational measures, such as speeding up, must be taken.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to connect a master station and a slave station by adopting this kind of high-speed communication system. In the control system, while maintaining high-speed communication,
A further object of the present invention is to enable connection of a slave unit having a low response speed.

[0009]

According to the first aspect of the present invention, when a corresponding communication response data has not been generated after a request from a master station such as a PLC arrives, the communication is performed. There is provided a communication device for returning predetermined substitute data to a master station within a reception allowable time of the master station without waiting for completion of generation of response data.

The invention described in claim 2 of the present application is
2. The communication device according to claim 1, further comprising a memory that is sequentially updated with the contents of the communication response data corresponding to the request from the master station, and using the contents of the memory as substitute data.

The invention described in claim 3 of the present application is
An inverter device which is detachable from a PLC and converts a DC power supply into an AC power supply having an arbitrary frequency. The inverter device has a built-in communication device according to claim 1 or 2 and transmits data including information on the frequency to communication response data. And returning it to the PLC.

Further, the invention described in claim 4 of the present application includes a PLC that is a control center, a master station that performs request processing in an arbitrary internal processing cycle, and an inverter device that is a device to be controlled. 3. A communication system according to claim 1, further comprising a control system communicably connected to a slave station in which communication response data generation processing is performed in an internal processing cycle longer than a cycle of the master station. Is included in the control system.

In the inventions described in the above claims, there are two "requests from the master station". One of the requests is called a “command command”, which is a command coming from the PLC. The other one is "Remote I / O"
It is called. This is an ID signal of an I / O channel determined in advance in device network communication, and is used for inquiring and processing the contents of a command corresponding to the I / O channel on the inverter side. is there. The “requirements” referred to in the present invention include the above 2
One thing is included.

Also, "without waiting for the completion of the generation of the communication response data" means that the communication response data is returned to the master station for the first time after the completion of the generation of the communication response data. It is specified to clarify the difference.

The phrase "within the allowable reception time of the master station" means that the communication response data from the slave station to the master station is always returned within the allowable reception time of the master station. This is clearly specified.

According to the above definition, according to the present invention, although the alternative data is returned to the master station without waiting for the completion of the generation of the communication response data, the return must always be performed immediately. However, it is only necessary to perform the operation within the allowable reception time of the master station.

[0017] According to the invention described in each of the claims, some substitute data is returned to the master station side irrespective of the communication response data generation processing on the slave station side. Even a slave station that takes a long time to generate can normally receive simulated communication response data on the master station side. Therefore, in a PLC system in which several slave units having high input / output response speeds are connected to a master station via a high-speed communication line, a slave station having a low input / output response speed is connected to the communication and processing speed of the entire system. Can be participated without lowering More specifically,
Even if it is difficult to increase the input / output response speed due to the characteristics of the induction motor, the inverter device can participate in a PLC system employing a high-speed communication line without any problem. The degree of freedom in designing such a system can be improved.

Further, according to the second aspect of the present invention, since the actual communication response data generated with a slight time delay is used as the substitute data returned to the master station, the control on the master station side is performed. Reliability can be maintained. In other words, although the substitute data returned to the master station has a slight time delay, it is actual communication response data, so that there is little possibility that the logic control on the PLC side will be affected.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of a PLC system to which the present invention is applied is conceptually shown in a block diagram of FIG.
This example shows a state in which a master station 1 including a PLC and a slave station 2 including an inverter are connected via a high-speed communication line T.

As described above, the feature of the slave station 2 to which the present invention is applied is that when a remote I / O request arrives from the master station 1 via the communication line T, the slave station 2 If the corresponding communication response data has not been generated on the two sides,
Without waiting for the completion of the generation of the communication response data, the master station 1
A communication response buffer function 2d for returning predetermined alternative data to the master station 1 within the allowable reception time on the side. Hereinafter, this point will be described in more detail.

The functions of the master station 1 including the PLC can be conceptually represented as a ladder program 1a, a communication protocol 1b, and a communication physical layer 1c. Similarly, the function of the slave station 2 including the inverter includes the communication physical layer 2a, the communication CPU
2b, inverter internal processing CPU 2c and remote I / O
It can be conceptually represented as an O communication response buffer function 2d.

In the master station 1, the ladder program 1a
Is sent to the communication physical layer 1c via the communication protocol 1b, and is sent out to the communication line T therefrom. The remote I / O request command sent to the communication line T is received by the slave station 2 via the communication physical layer 2a and sent to the communication CPU 2b. Next, the communication CPU 2b sets a condition that the state of the inverter internal processing CPU 2c is not Busy.
The received remote I / O request command is transferred to the inverter internal processing CPU 2c. Thereafter, the inverter internal processing CP
The U2c executes the above-described internal processing, waits for completion of the execution of the internal processing, and generates response data to the remote I / O request. This response data is transmitted to the communication CPU 2
b. The communication CPU 2b gives the response data received from the inverter internal processing CPU 2c to a remote I / O communication response buffer 2d which is a main part of the present invention. A predetermined buffer memory is provided in the remote I / O communication response buffer 2d. This buffer memory is updated with the contents of the response data each time new response data is generated in the inverter internal processing CPU 2c. Then, the latest response data is always read from the remote I / O communication response buffer 2d. The read response data to the remote I / O request is transmitted to the communication physical layer 2
is transmitted onto the communication line T via a. The response data transmitted on the communication line T is received by the master station 1 via the communication physical layer 1c. The received response data reaches the ladder program 1a via the communication protocol 1b.

As described above, the buffer memory included in the remote I / O communication response buffer 2d always stores the latest response data. On the other hand, the communication CPU 2b sends the remote response data every time a remote I / O request arrives. A command is given to the I / O communication response buffer 2d, and the latest response data stored in the buffer memory at that time is transmitted to the communication physical layer 2d.
A is transmitted to the communication line T via a. In other words, when the function of the communication CPU 2b and the function of the remote I / O communication response buffer 2d are combined, when the remote I / O request arrives from the master station via the communication line, the slave station responds. If the communication response data to be generated has not been generated, a communication response buffer function that returns predetermined alternative data to the master station within the allowable reception time of the master station without waiting for the completion of generation of the communication response data is realized. It is being done. In particular, in this embodiment, the remote I / O communication response buffer 2d is provided with a buffer memory that is sequentially updated with the contents of the communication response data, and the contents of the buffer memory are used as substitute data. 2 can transmit the communication response data to the master station side, and the processing procedure regarding the exchange of transmission / reception data between the master station and the slave station described above is shown in chronological order. It should be noted that, in the figure, the same circled numbers represent processes executed in substantially the same time zone.

First, the PLC on the master station side sends a remote I / O request to the inverter serving as a slave station (step 201). Then, after receiving the remote I / O request, the inverter communication unit of the slave station (including the communication physical layer 2a, the communication CPU 2b, the remote I / O communication response buffer 2d, etc.)
Check the status of. Here, the inverter internal processing C
If the PU 2c is not in the busy state, the remote I / O from the inverter communication unit to the inverter internal processing CPU 2c
The request is passed (step 202). Next, in the inverter internal processing CPU 2c, the remote I / O
The processing is started according to the O request (step 203).
As described above, processing in accordance with the remote I / O request requires a certain processing time.

On the other hand, after passing the remote I / O request to the inverter internal processing CPU 2c, the inverter communication unit immediately sends the remote I / O request to the master station without waiting for the completion of the communication response in the inverter internal processing CPU 2c. / O communication response buffer data is returned (step 204). The transmission of the remote I / O communication response buffer data is performed based on the buffer data (latest communication response data) stored in the buffer memory in the remote I / O communication response buffer 2d. The buffer data returned from the inverter communication unit to the master station is sent within the allowable reception time of the master station. Therefore, the master station normally receives the communication response buffer data returned from the inverter communication unit as a response to the remote I / O request (step 205).

Thereafter, at the master station, the second remote I / O
An O request is transmitted to the slave station, the inverter (step 206). Then, the inverter communication unit of the slave station receives the remote I / O request, and then executes the inverter internal processing CP.
Check the state of U2c. At this time, the inverter internal processing CPU 2c is already executing a process according to the remote I / O request, and is in the busy state. Therefore, in this state, the remote communication from the inverter communication unit to the inverter internal processing CPU 2c is performed.
No / O request is passed (step 207).
Thereafter, the inverter communication section returns remote I / O communication response buffer data to the master station (step 2).
08). That is, even in this state, since the response to the remote I / O request has not yet been created in the inverter internal processing CPU 2c, the buffer data is immediately returned to the master station without waiting for the creation. (Step 208).

On the other hand, in this state, when a response to the remote I / O request is created in the inverter internal processing CPU 2c (step 209), the created communication response data is immediately passed to the inverter communication unit. . As described above, the response to the remote I / O request includes, for example, frequency information of an output power source, forward / reverse rotation information of a connected motor, and abnormality of a motor (overcurrent, overvoltage, overload, overheating, etc.). Etc.) condition,
This is warning information (for example, a forward rotation command and a reverse rotation command are input at the same time). Then, the contents of the buffer memory in the remote I / O communication response buffer 2d are updated with the received communication response data (step 211).
That is, the contents of the buffer memory in the remote I / O communication response buffer 2d are stored in the inverter internal processing CPU 2
It is sequentially updated with the latest response data created in c.

In the same way as above, the master station normally receives a response to the remote I / O request (step 210), and then transmits a third remote I / O request to the inverter (step 210). Step 212). Then, after receiving the remote I / O request (step 213), the inverter communication unit on the slave station checks the state of the inverter internal processing CPU 2c in the same manner as described above. At this time, since the state of the inverter internal processing CPU 2c is not the Busy state, a remote I / O request is transferred from the inverter communication unit to the inverter internal processing CPU 2c. In response to this, the inverter internal processing CPU 2c performs processing in accordance with the remote I / O request in the same manner.

On the other hand, after passing the remote I / O request to the inverter internal processing CPU 2c, the inverter communication section returns the remote I / O communication response buffer data to the master station in the same manner as described above (step 215). . The master station normally receives the buffer data returned from the inverter communication unit of the slave station as a response to the remote I / O request (step 216). Thereafter, the master station repeats the same processing.

As described above, in the embodiment shown in FIGS. 1 and 2, the internal processing of the inverter is performed by the operation of the inverter communication section mainly composed of the communication CPU 2b and the remote I / O communication response buffer 2d. Irrespective of the operation of the CPU 2c, the remote I / O communication response buffer data is returned at short intervals so as to match with the communication cycle of the high-speed response. Even if the operation of the processing CPU takes a long time, when the slave station is viewed from the master station, the apparent response speed is sufficiently high. Therefore, as a communication system, A
Even if a high-speed communication method based on the open network Device Net proposed by B (Arlen Bradley) is adopted, the inverter can be handled in the same manner as other high-speed response handsets, and communication speed can be maintained. At the same time, the inverter can operate normally.

Next, a more specific embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows an example of a more specific system configuration of a remote control system using a PLC. In the figure, 3 is a master unit as a master station, 4 is an I / O link unit, 5 is a remote I / O terminal, 6 is a remote adapter, 7 is a sensor terminal, 8 is an analog terminal, 9 is a temperature sensor terminal, Reference numeral 10 denotes an inverter, and 11 denotes an environment-resistant terminal. These nine slave units 4 to 11 are connected to each other via a high-speed communication line 12. The basic configuration of the inverter 10 is the same as the conventional one, but this inverter 1
The communication device according to the present invention includes an option card 10a.
It is built in the form of

Inverter 10 and option card 1
The details of the circuit configuration of Oa are shown in FIG. As shown in the figure, the entire circuit includes a physical layer 100, a communication management unit 200, and an inverter main circuit unit 300. The physical layer 100 and the communication management unit 200
Are mounted on the option card 10a. Also,
The option card 10a is detachably connected to the inverter main body circuit section 300 via a connector CN.

The physical layer 100 has a built-in physical layer power supply 101, driver receiver 102, photocoupler 103, etc., and is connected to the communication line 12 via a terminal block 104. The driver / receiver 102 is a photocoupler 103
Is connected to the communication management unit 200 via the.

The communication management section 200 is mainly composed of a CPU 201, a communication controller 202, an EEP-ROM 203, a shared memory 204 and the like. Here, the shared memory 204 is constituted by a dual port memory, and a remote I / O
It is used to transfer O request data and response data to remote I / O requests. Further, the shared memory 204 also functions as the buffer memory described above. The inverter body circuit section 300 includes the gate array 3
01, inverter CPU 302, flash ROM 30
3, photo coupler 304, IPM 305, power supply circuit 30
6, the rectifier 307 and the like. Here, the inverter CPU 302 corresponds to the inverter internal processing CPU 2c described above, and the inverter CPU 302 controls the entire inverter main circuit 300.

When a remote I / O request arrives via the communication line 12, the remote I / O request is
The data is taken into the CPU 201 via the driver / receiver 102, the photocoupler 103, and the communication controller 202, and further written into the shared memory 204. The I / O request written in the shared memory 204 is taken into the inverter CPU 302 via the gate array 301 by, for example, a handshake process, and is decoded and executed. The response data to the remote I / O request obtained by this execution is stored in various ports 308,
After being taken into the inverter through 310, 312, 314, etc., the shared memory 2 is passed through the gate array 301.
04 is written. The CPU 201 appropriately reads out the communication response buffer data written in the shared memory 204 in response to the remote I / O request, and reads the communication response buffer data via the communication controller 202, the photocoupler 103, and the driver / receiver 102. Send to.

According to this embodiment, the option card 1 is used for the existing inverter device having a relatively slow processing speed.
Only by adding 0a, the inverter device can function as a slave unit capable of high-speed input / output response.

According to the two embodiments described above, when a remote I / O request arrives from a master station to a slave station,
The inverter communication unit of the slave station gives a remote I / O request to the inverter internal processing CPU on condition that it is not in the Busy state, and then creates response data for the remote I / O request in the inverter internal processing CPU. Until, the response data to the previous remote I / O request recorded in the buffer memory is
Since the response is repeatedly returned to the master station in response to the remote I / O request, the remote I / O communication response data is sent to the master station at a period much shorter than the processing time in the inverter internal processing CPU. Can be returned. Therefore, when the slave station is viewed from the master station, the apparent input / output response speed is much shorter than the response data generation cycle performed by the inverter internal processing CPU. It can be applied to a communication system.

[0038]

As is clear from the description of each of the embodiments, according to the present invention, it is possible to maintain the performance of high-speed communication as it is and to allow a slave station such as an inverter having a low processing speed to participate in communication. Becomes possible. In addition, a conventional model can be connected at low cost by placing a dummy between the communication master station without changing the processing speed of the inverter main body in order to participate in high-speed communication. Further, by employing this communication method, the internal processing of the inverter is independent, and the internal processing of the inverter can be performed irrespective of the communication cycle of the master station. This has the effect of increasing the software development efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram conceptually showing the overall configuration of a PLC control system to which the present invention is applied.

FIG. 2 is a flowchart showing a data processing procedure between a master station and a slave station in the PLC control system to which the present invention is applied.

FIG. 3 is a system diagram showing a system configuration of a PLC control system to which the present invention is applied.

FIG. 4 is a block diagram showing in detail an inverter internal circuit to which the present invention is applied.

FIG. 5 is a flowchart showing a data processing procedure between a master station and an inverter serving as a slave station in a conventional PLC control system.

[Explanation of symbols]

 Reference Signs List 1 master station 1a ladder program 1b communication protocol 1c communication physical layer 2 slave station 2a communication physical layer 2b communication CPU 2c inverter internal processing CPU 2d remote I / O communication response buffer 3 master unit 4 I / O link unit 5 remote I / O Terminal 6 Remote adapter 7 Sensor terminal 8 Analog terminal 9 Temperature sensor terminal 10 Inverter 11 Environmental resistance terminal 10a Option card 12 High-speed communication line 100 Physical layer 101 Physical layer power supply 102 Driver / receiver 103 Photocoupler 200 Communication management unit 201 Communication CPU 202 Communication Controller 204 Shared memory 300 Inverter main body circuit section 301 Gate array 302 Inverter CPU 304 Photocoupler 305 IPM 306 Power supply circuit 307 rectifier

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H220 BB03 CC05 CC09 CX05 CX09 DD04 EE10 FF10 JJ03 JJ12 JJ29 5K034 AA01 CC06 DD01 HH01 HH02 TT04

Claims (4)

[Claims] When a corresponding communication response data is not generated after a request from a master station such as a PLC arrives,
A communication device for returning predetermined substitute data to a master station within a reception allowable time on the master station side without waiting for completion of generation of the communication response data. 2. The communication according to claim 1, further comprising a memory that is sequentially updated with the contents of communication response data corresponding to a request from the master station, and using the contents of the memory as substitute data. apparatus. 3. An inverter device which is detachable from the PLC and converts a DC power supply into an AC power supply having an arbitrary frequency, wherein the communication device according to claim 1 or 2 is built in and includes information on the frequency. An inverter device for returning data to a PLC as communication response data. 4. A communication response in an internal processing cycle longer than a cycle of the master station, including a master station including a PLC as a control center and performing a request processing in an arbitrary internal processing cycle, and an inverter device as a control target device. A control system communicably connected to a slave station where data generation processing is performed, wherein the slave station includes the communication device according to claim 1 or 2. .