JP2020080463A - Numerical control device with error correction function during communication - Google Patents

Abstract

To suppress the number of times of retransmission and prevent the stop of a machine when a retransmitted frame is also destroyed in a communication in a numerical control device.SOLUTION: A numerical control device equipped with an error detection function by CRC includes a reception buffer that can store at least one reception frame, a comparison unit that compares a first received frame and a retransmitted second received frame to detect a mismatch, a plurality of CRC calculation units that calculate a CRC on the basis of the received frame, a data selection unit that controls data included in the received frame which is data to be sent to each of the plurality of CRC calculation units, and a result selection unit that selects the data to be used on the basis of the calculation results of the plurality of CRC calculation units, and has a function to perform error correction by calculating CRC of a pattern obtained by combining the first received frame and the second received frame in parallel when the second received frame is received.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a numerical control device that exchanges data by communication between units in order to control an object to be controlled.

  In a numerical control device for a machine tool, an I/O device for controlling a drive device for driving a motor, a solenoid, etc. exists at a position distant from the numerical control device, and therefore it is necessary to communicate data such as commands.

  When IEEE802.3 defined for Ethernet (registered trademark) is used, if a frame storing data is destroyed, the frame is destroyed in order to prevent the controlled object from operating based on an erroneous frame. A CRC (Cyclic Redundancy Check) that can easily detect a burst error may be used as a means for detecting this.

  Further, as a measure against the case where a correct frame cannot be received due to the frame being destroyed by noise or the like, there is a case where the probability that the frame can be normally received is increased by retransmitting the frame.

  By the way, in the error detection by CRC, the error location cannot be specified and the error cannot be corrected, so that the retransmission is necessary to receive the correct frame. However, in communication in a numerical control device in which real-time property is important, if the same frame is retransmitted a plurality of times, the communication cannot be completed within a specified time, and the machine stops.

  An object of the present invention is to prevent the machine from stopping while suppressing the number of retransmissions when the retransmitted frame is also destroyed in the communication in the numerical control device.

  A numerical control device according to the present invention is a numerical control device for a machine having an error detection function by CRC, and has a reception buffer capable of storing at least one reception frame, a first reception frame and a retransmitted frame. A comparison unit for comparing the received frame of the second time to detect a mismatched portion; a plurality of CRC calculation units for calculating a CRC based on the received frame; and data to be sent to each of the plurality of CRC calculation units. The second reception frame includes a data selection unit that controls data included in the reception frame, and a result selection unit that selects data to be used based on the CRC calculation results of the plurality of CRC calculation units. Has a function of correcting an error by concurrently calculating a CRC of a pattern obtained by combining the first received frame and the second received frame.

  According to the present invention, it becomes possible to perform error correction with a small delay and prevent the machine from stopping.

It is a block diagram which shows the system which concerns on embodiment of this invention. It is a figure explaining the error correction method which concerns on embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the control device 1 includes a control unit 11, a transmission unit 12, and a reception unit 13. The transmission unit 12 includes a transmission buffer 121 that stores data to be transmitted, a transmission control unit 122 that generates a transmission frame, a CRC calculation unit 123 that calculates a CRC assigned to a frame, and a frame transmission unit 124 that transmits a frame. And The reception unit 13 includes a frame reception unit 134 that receives a frame, a CRC calculation unit 133a that checks the CRC of the received frame, a reception control unit 132 that controls a data storage destination according to the information of the frame, and received data. And a reception buffer 131 for storing the received data. Further, the receiving unit 13 compares the received frames with each other to detect a mismatched portion, a mismatch buffer 136 for temporarily storing a mismatched portion and a frame at the time of a mismatch, and a CRC calculation unit 133b for error correction. , 133c, a data selection unit 137 that counts the number of times of mismatch and switches data to be sent to the CRC calculation units 133b and 133c, and a result selection unit that selects a data pattern to be used from the results calculated by the CRC calculation units 133a, 133b, and 133c. And 138. Like the control device 1, the drive device 2 also includes a control unit 21, a transmission unit 22, and a reception unit 23. The configuration of the transmission unit 22 is the same as the configuration of the transmission unit 12. The configuration of the receiving unit 23 is the same as the configuration of the receiving unit 13.

  During normal communication in which no error occurs, the command value generated by the control device 1 is transmitted to the drive device 2, the drive device 2 receives the command value, drives the machine according to the command, and sends a response to the control device 1. Send to. Specifically, the control unit 11 of the control device 1 generates a command value for the drive device 2 and writes the command value in the transmission buffer 121. After that, the control unit 11 sends a transmission start command to the transmission control unit 122. The transmission control unit 122 that has received the transmission start command sends the data in the transmission buffer 121 to the CRC calculation unit 123. The CRC calculation unit 123 calculates a CRC from the received data, and sends a frame in which CRC information is added to the data to the frame transmission unit 124. The frame transmitter 124 transmits the transmitted frame to the drive device 2.

  The frame reception unit 234 in the drive device 2 sends the frame received from the control device 1 to the reception control unit 232 via the CRC calculation unit 233a. The CRC calculation unit 233a calculates the CRC of the received frame, determines whether the data of the received frame is correct, and notifies the reception control unit 232 of the determination result. The reception control unit 232 saves the reception frame in the reception buffer 231, and when the CRC calculation unit 233a determines that the reception frame is normal, notifies the control unit 21 that the reception is completed. The control unit 21 drives the device based on the command information stored in the frame stored in the reception buffer 231, stores the response information in the transmission buffer 221, and transmits it to the control device 1 so as to transmit the transmission control unit. Instruct to 222. The transmission control unit 222 that has received the instruction transmits a frame to the control device 1 in the same operation as the transmission unit 12.

  In the communication flow, when the frame transmitted from the control device 1 is destroyed, the reception control unit 232 stores the reception frame in the reception buffer 231, and the CRC calculation unit 233a confirms that the reception frame is abnormal. Since it has been notified, the transmission control unit 222 is instructed to transmit the frame of the retransmission request. Upon receiving the instruction, the transmission control unit 222 generates a retransmission request frame and transmits it to the control device 1. The control device 1 that has received the retransmission request retransmits the same frame to the drive device 2 in response to the request.

The drive device 2 that has received the retransmitted frame executes error correction processing in parallel during frame reception processing. This error correction process will be described with reference to FIG. FIG. 2A shows that the data is destroyed in the section from the A ₀ byte to the A ₁ byte in the received frame before retransmission. FIG. 2B shows that the data is destroyed in the section from the B ₀ byte to the B ₁ byte in the received frame at the time of retransmission. FIG. 2C and FIG. 2D show a frame created by combining two received frames before and during retransmission. In the present embodiment, due to the nature of CRC, if there is a burst error longer than the CRC length and there are errors in two or more locations in a single frame, the reliability decreases, so error correction is not performed. Therefore, in the following, a case where the section in which the frame is destroyed is shorter than the CRC length will be described.

The frame reception unit 234 passes the received frame to the reception control unit 232 via the CRC calculation unit 233a. The reception control unit 232 having received the retransmission-time reception frame reads the pre-retransmission reception frame stored in the reception buffer 231, and transmits the pre-retransmission reception frame and the retransmission-time reception frame to the comparison unit 235 and the data selection unit 237. In addition, the reception frame at the time of retransmission is stored in the reception buffer 231. The comparison unit 235 compares the received pre-retransmission received frame with the re-transmission received frame, and if the frames do not match, outputs a mismatch detection signal to the data selection unit 237. In the case of the example in FIG. 2, in the section from A ₀ byte to A ₁ byte and the section from B ₀ byte to B ₁ byte, a mismatch occurs between the pre-retransmission received frame and the retransmitted received frame. Therefore, a mismatch detection signal is output for these sections. The data selection unit 237 causes the CRC calculation unit 233b to execute the CRC calculation shown in FIG. 2C, and causes the CRC calculation unit 233c to execute the CRC calculation shown in FIG. 2D. Sort the data.

Specifically, the data selection unit 237 transmits the retransmission reception frame (b) to the CRC calculation unit 233b at the start of reception of the retransmission reception frame, and the CRC calculation unit 233c transmits the pre-retransmission reception frame ( a) is transmitted. Then, the data selection unit 237, when receiving the mismatch detection signal _{(A 0),} from which CRC length until the _(C L Byte in the present embodiment), the destination (CRC calculation section 233b, 233 c) wherein the data transmitted to _the, replacing the received frame from the position a 0 + _{C L,} the CRC calculation section 233b transmits a retransmission previous received frame (a), the retransmission time received frame to the CRC calculation section 233c of (b) Send. Further, at that time, the data selection unit 237 increments a counter (hereinafter referred to as a non-coincidence counter) for recording the number of non-coincidences of the data in the frame inside the data selection unit 237, and sets the head of the non-coincidence position in the non-coincidence buffer 236. The data of A ₀ shown and the data of A ₀ to A ₀ +C _L −1 which is data of C _L bytes are stored. The data selection unit 237 also performs the same operation as above when receiving the next mismatch detection signal (B ₀ ). That is, the data selection unit 237 replaces the data to be sent to the CRC calculation unit 233b and the CRC calculation unit 233c from the position of B ₀ +C _L again, increments the mismatch counter in the same manner as above, and moves the mismatch buffer 236 to the beginning of the mismatch position. The data of B ₀ shown and the data of B ₀ to B ₀ +C _L −1 which is data of C _L bytes are stored. Since the mismatch detection signal does not appear until the reception is completed after that, each CRC calculation unit (CRC calculation unit 233a, 233b, 233c) calculates the CRC based on the data distributed to itself, and selects the CRC result as the result. And send to section 238.

The result selection unit 238 receives calculation results from the three CRC calculation units (CRC calculation units 233a, 233b, 233c) and determines valid results. When the result of the CRC calculation unit 233a, which is the CRC calculation result of the retransmission reception frame, is correct, the result selection unit 238 uses the retransmission reception frame stored in the reception buffer 231 as it is. If only the CRC calculation result of the CRC calculation unit 233b is correct, the result selection unit 238 indicates that the received frame calculated by the CRC calculation unit 233b (the received frame shown in FIG. 2C) is correct. The pre-retransmission received data (B ₀ to B ₀ +C _L −1 data) of the mismatched portion B stored in 236 is written in the reception buffer 231 to perform error correction. When only the CRC calculation result of the CRC calculation unit 233c is correct, the result selection unit 238 receives the pre-retransmission received data (data of A ₀ to A ₀ +C _L −1) of the mismatched portion A stored in the mismatch buffer 231. Write to and correct the error. When the CRC calculation results of both the CRC calculation unit 233b and the CRC calculation unit 233c are correct, the result selection unit 238 does not perform error correction because the result CRC calculation results in which one of the CRC calculation units 233b is incorrect are incorrect. The reception control unit 232 is notified of the reception error, and the retransmission request is made again. Similarly, the result selection unit 238 does not perform error correction even when the results of all the CRC calculation units are erroneous, notifies the reception control unit 232 of a reception error, and requests retransmission again.

  If there is an error of CRC length or more without error correction, and if there are two or more errors in the same frame, there will be three or more mismatched points (two errors exceed the CRC length. Therefore, if the mismatch counter is 3 or more, the reliability of the received frame is low and the error correction is invalidated. The invalidation is performed by the data selection unit 237 continuing the reset input to the CRC calculation unit 233b and the CRC calculation unit 233c and setting the CRC calculation result to a fixed value.

<Modification 1>
In the above embodiment, the case where the retransmission process is performed by sending the retransmission request when the frame cannot be received normally has been described, but the same frame is always transmitted a plurality of times instead of being retransmitted in response to the retransmission request. The frame may be received more than once by a method such as.

<Modification 2>
In the above embodiment, the case where the control device 1 and the drive device 2 are connected by one-to-one communication has been described, but a network connected by other than one-to-one communication such as ring connection may be used. .. In this case, by preparing a reception buffer for each communication partner, it becomes possible to perform error correction even when a communication frame with another communication partner is interrupted between the frame and the retransmission frame.

  The control device 1 and the drive device 2 described above are realized, for example, by the cooperation of hardware resources and software. Specifically, the control device 1 and the drive device 2 include a processor such as a CPU (not shown). The function of each unit of the control device 1 and the drive device 2 is realized by the processor reading and executing a program stored in a storage device (not shown). The program is stored in the storage device via a recording medium such as a CD or a DVD, or via a communication path such as a network. Alternatively, each unit of the control device 1 and the drive device 2 may be realized by a hardware resource such as a processor or an electronic circuit. A device such as a memory may be used in the realization thereof. As another example, each unit of the control device 1 and the drive device 2 may be realized by a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or the like.

  DESCRIPTION OF REFERENCE NUMERALS 1 control device, 2 drive device, 11,21 control unit, 12,22 transmission unit, 13,23 reception unit, 121,221 transmission buffer, 122,222 transmission control unit, 123,133a, 133b, 133c, 223, 233a , 233b, 233c CRC calculation unit, 124, 224 frame transmission unit, 131, 231 reception buffer, 132, 232 reception control unit, 134, 234 frame reception unit, 135, 235 comparison unit, 136, 236 mismatch buffer, 137, 237 Data selection unit, 138, 238 result selection unit.

Claims (1)

In the numerical control device of the machine equipped with the error detection function by CRC,
A reception buffer capable of storing at least one reception frame,
A comparing unit that compares the first received frame with the retransmitted second received frame to detect a mismatched portion;
A plurality of CRC calculation units that calculate a CRC based on the received frame;
A data selection unit that controls data included in the received frame, which is data to be sent to each of the plurality of CRC calculation units;
A result selection unit that selects data to be used based on the CRC calculation result of each of the plurality of CRC calculation units;
Have
When the second received frame is received, the CRC of the pattern obtained by combining the first received frame and the second received frame is also calculated in parallel to have an error correction function.
Numerical control device.

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