JP7585779B2 - Communication device, elevator communication device, and communication method - Google Patents

Description

This disclosure relates to a communication device.

One of the network protocols that is widely used in in-vehicle networks is the Controller Area Network (CAN) communication method. This communication method is also widely used in industrial equipment, agricultural machinery, medical equipment, railways, elevators, etc.

In the CAN communication method, binary digital signals with logical values of "0" and "1" are converted into differential signals and transmitted via a two-wire communication bus line (CAN_H line (hereinafter, H line) and CAN_L line (hereinafter, L line)). The differential signals transmitted on the H line and L line respectively express two states, dominant and recessive, depending on the voltage level. In the protocol standardized by ISO11898, if the voltage of the signal on the H line is high level and the voltage of the signal on the L line is low level, and the potential difference between the H line and the L line exceeds a predetermined value, it expresses the logical value "0" as dominant, and if the voltage of the signal on the H line is low level and the voltage of the signal on the L line is high level, and the potential difference between the H line and the L line is below a predetermined value (including the same potential), it expresses the logical value "1" as recessive.

If communication stops for some reason while the CAN communication system is in operation, this may affect safety in applications such as the above-mentioned in-vehicle equipment. For this reason, a method has been proposed to detect signs of communication malfunctions so that the communication system does not stop unintentionally while in operation.

In a conventional method, signals transmitted and received by a CAN transceiver of a communication device are input to a monitoring circuit installed on the communication line to detect abnormalities. Voltage judgment values are set to determine whether or not an abnormality exists for the high and low voltage values of the H-line and L-line signals input to the monitoring circuit, and abnormalities (signs of element destruction) are detected by comparing the voltage values with the power judgment values (see, for example, Patent Document 1).

JP 2006-108952 A

In the above-mentioned conventional technology, the presence or absence of an abnormality in the CAN transceiver is determined by comparing the voltage values of the H line and L line with a voltage judgment value that judges the presence or absence of an abnormality, and signs of element destruction are detected. However, in a CAN communication system, communication problems can occur due to delays in the communication path. Although the conventional technology detects deterioration of the CAN transceiver, it does not have a mechanism for detecting delays in the communication path.

Causes of delays in communication paths include, for example, temperature changes in the environment in which the communication lines are installed, as well as when the communication lines are bundled together with other wiring such as power lines into a communication cable, the other wiring may heat up depending on the load situation, causing the temperature of the communication lines to rise. When the temperature of the communication lines rises, the impedance increases and delays occur. Also, when the CAN communication method is applied to equipment with a long service life such as elevators, the communication lines deteriorate over time due to long-term use, increasing the impedance and causing delays.

The purpose of this disclosure is to detect signs of communication problems caused by delays in the communication path in a CAN communication system.

In order to solve the above-mentioned problems and achieve the objective, the communication device disclosed herein is a communication device that transmits and receives data with other communication devices via a communication line based on a CAN communication protocol, and is equipped with a control unit that controls the transmission and reception of data, a delay time calculation unit that receives as input transmission data output from the control unit and reception data output from the other communication device in response to the transmission data, and calculates the delay time of the communication path from a signal set in the ACK bit of the transmission data and an acknowledgement signal set in the ACK bit included in the reception data, and a delay determination unit that compares the delay time with a threshold value and outputs delay determination information.

According to the present disclosure, it is possible to detect signs of communication problems caused by delays in the communication path in a CAN communication system.

FIG. 1 shows an example of the configuration of a communication system according to a first embodiment. FIG. 1 is a diagram showing a configuration example of a CAN transceiver according to a first embodiment of the present invention; FIG. 1 is a diagram showing an example of a data frame structure used in the CAN communication method according to the first embodiment; Truth table of logical operations executed by the delay time calculation unit according to the first embodiment FIG. 2 is a diagram showing a schematic diagram of a logical operation result of the delay time calculation unit according to the first embodiment; FIG. 1 is a diagram showing an example of the configuration of a delay time calculation unit and a delay determination unit according to the first embodiment; FIG. 13 is a diagram showing the relationship between the time width of a delay time pulse and a threshold value according to the first embodiment. FIG. 1 shows a modified example of the configuration of a communication system according to the first embodiment. FIG. 1 shows a modified example of the configuration of a communication system according to the first embodiment. 1 is a flowchart for explaining the operation of the first communication device according to the first embodiment. 11 is a flowchart for explaining the operation of the first communication device according to the second embodiment. FIG. 13 is a diagram showing a configuration example of a communication system according to a third embodiment. FIG. 13 is a diagram showing a schematic diagram of a relationship between a delay time and a usage time according to the third embodiment. 11 is a flowchart for explaining the operation of the first communication device according to the third embodiment. Hardware diagram of a first communication device according to the first to third embodiments

Below, an embodiment of the present disclosure will be described with reference to the attached drawings. In each drawing, the same or corresponding parts are given the same reference numerals. Duplicate descriptions will be simplified or omitted as appropriate. Note that the present disclosure is not limited to the embodiment described below.

Embodiment 1.
1 is a diagram showing an example of the configuration of a communication system according to an embodiment of the present disclosure. A first communication device 1 is connected to a second communication device 11 via a communication line 8. The first communication device 1 has a communication control board 2, which has a control unit 3, a CAN controller 4, and a CAN transceiver 5. The communication control board 2 further has a delay time calculation unit 6 and a delay determination unit 7 for detecting a sign of a communication failure caused by a delay in the communication path.

The second communication device 11 also has a communication control board 12, which has a control unit 13, a CAN controller 14, and a CAN transceiver 15. In FIG. 1, a configuration in which the first communication device 1 and the second communication device 11 are connected is disclosed for the sake of simplicity, but the first communication device 1 may be connected to multiple communication devices other than the second communication device 11. The configurations of the parts of the first communication device 1 and the second communication device 11 are the same except that the first communication device 1 is provided with a delay time calculation unit 6 and a delay determination unit 7. In addition, when the first communication device 1 is a master and is connected to multiple other communication devices (i.e., in the case of one-to-many communication), it is also possible to use a listen-only function in which a communication device identified by the first communication device 1 responds to the first communication device 1. This can also be applied to the following embodiments in the case of one-to-many communication. The listen-only function will be described later.

The communication line 8 is a two-wire communication bus line (H line 81, L line 82), and typically uses a twisted pair cable. The communication line 8 may be bundled with other wiring such as a power line and installed as a communication cable.

The control unit 3 includes a CAN controller 4. The CAN controller 4 controls data transmission and reception with the second communication device 11 via the CAN transceiver 5. The control unit 3 also detects delays in the communication path based on delay determination information output from the delay determination unit 7.

The control unit 3 is a microcomputer and includes a processor 31 and a memory 32. The processor 31 is, for example, a CPU (Central Processing Unit), a microprocessor, or a DSP (Digital Signal Processor). The memory 32 is, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory), and stores software programs, log data, and the like. The processor 31 executes a software program stored in the memory 32 to realize the function of at least one circuit of the first communication device 1. Note that the memory 32 is not limited to being built into the control unit 3 as shown in the figure. It may be an external storage device capable of inputting and outputting data to and from the first communication device 1.

2 is a diagram showing an example of the configuration of the CAN transceiver 5. The CAN transceiver 5 has a transmission buffer 51, a reception buffer 52, transistors 53 and 54, and input/output ports 55 (for H line) and 56 (for L line). The transmission buffer 51 converts the transmission data (TxD), which is binary digital data received from the CAN controller 4, into a differential signal and outputs it to the transistors 53 and 54. The transistors 53 and 54 adjust the voltage of the differential signals transmitted through the H line 81 and the L line 82, respectively, so that the differential signals are at a predetermined potential. The voltage-adjusted differential signals are output from the input/output ports 55 and 56 and transmitted to the CAN transceiver 15 of the second communication device 11 via the communication line 8. The input/output ports 55 and 56 also receive the differential signal transmitted from the second communication device 11. The reception buffer 52 converts the differential signal into reception data (RxD), which is binary digital data, and outputs it to the CAN controller 4.

Next, an ACK (Acknowledge) function that confirms that data transmitted from the CAN controller 4 of the first communication device 1 has been successfully received by the CAN controller 14 of the second communication device 11 will be described. FIG. 3 is a diagram showing an example of a data frame structure used in the CAN communication method. In this disclosure, a "data frame" is a format used when transmitting and receiving data between communication devices, and refers to a group of transmitted signals. This frame structure is one example, and the present disclosure can be applied to any CAN communication method in which a signal equivalent to an ACK signal is transmitted and received.

A data frame contains SOF (Start Of Frame), ID (Identifier), RTR (Remote Transmission Request), control field, data field, CRC (Cyclic Redundancy Check) sequence, CRC delimiter, ACK (Acknowledge) slot, ACK delimiter, and EOF (End Of Frame). The numbers shown in the diagram indicate the bit length available for use in each section. Note that ITM (Intermission) is not included in the data frame. After ITM, the bus enters an idle state.

The CAN controller 4 performs a CRC calculation on the data in the SOF, ID, control field, and data field, stores the calculation result in a CRC sequence, and transmits it. The ACK slot contains a 1-bit ACK signal (hereafter referred to as the ACK bit). The CAN controller 4 transmits the ACK bit as recessive ("1").

The CAN controller 14 of the second communication device 11 responds to the CAN controller 4 at the same time that the CAN controller 4 transmits the ACK bit in the ACK slot of the data frame. The CAN controller 14 performs a similar CRC calculation on the contents of the received data frame. If the calculation result matches the result calculated by the CAN controller 4 stored in the CRC sequence, the CAN controller 14 sets the ACK bit to dominant ("0") and responds to the CAN controller 4 asynchronously.

In the CAN protocol, dominant signals on the communication line 8 have a higher priority than recessive signals, so even if the CAN controller 4 sets the ACK bit to recessive, the CAN controller 14 sets it to dominant, and the ACK bit in the data frame monitored by the CAN controller 4 also becomes dominant. Therefore, by confirming that the ACK bit in the data frame is dominant, the CAN controller 4 recognizes that the second communication device 11 has received the data normally.

Next, we will explain how to detect delays in the communication path.

By branch 2a between the CAN controller 4 and the CAN transceiver 5, the transmission data sent from the CAN controller 4 is input to the delay time calculation unit 6. In addition, the data received from the second communication device 11 is input to the CAN controller 4 via the CAN transceiver 5, and is also input to the delay time calculation unit 6 as received data by branch 2b. Note that since the received data is the data sent by the CAN controller 4 except for the ACK bit, unless there is an abnormality in the communication path, the bits up to the ACK slot will be the same as the data sent by the CAN controller 4.

The delay time calculation unit 6 performs a logical operation using the transmitted data and received data as input. Figure 4 is a truth table of the logical operation performed by the delay time calculation unit 6. The delay time calculation unit 6 performs a logical operation on a binary signal bit according to the truth table in Figure 4, with a high voltage state being recessive ("H") and a low voltage state being dominant ("L"), and outputs the operation result Q to the delay determination unit 7. As shown in the logical formula below, the operation result Q is output by taking the logical product of the transmitted data and the received data with the logic inverted.

図５は、遅延時間算出部６の論理演算を模式的に示す図である。縦軸を電圧、横軸を時間として、（ａ）送信データ、（ｂ）受信データ、（ｃ）論理演算結果が示される。前述の通り、第２の通信装置１１が正常にデータを受信してＡＣＫビットをドミナントに設定して応答した場合、遅延時間算出部６に入力される送信データと受信データのＡＣＫスロットの前までのビットは同じであるから、図４に示す真理値表に従う論理演算の結果、これらのビットの電圧レベルはドミナント（“Ｌ”）となる。

5 is a diagram showing a schematic diagram of the logical operation of the delay time calculation unit 6. The vertical axis is voltage and the horizontal axis is time, and (a) transmission data, (b) reception data, and (c) logical operation result are shown. As described above, when the second communication device 11 normally receives data and responds by setting the ACK bit to dominant, the transmission data input to the delay time calculation unit 6 and the reception data are the same until the ACK slot, so that the voltage level of these bits becomes dominant ("L") as a result of the logical operation according to the truth table shown in FIG. 4.

On the other hand, regarding the ACK bit, the ACK bit of the transmission data sent by the first communication device 1 is recessive ("H"), whereas the response from the second communication device 11 is dominant ("L"). This response is returned asynchronously from the second communication device 11 at the timing when the first communication device 1 is transmitting the ACK bit, so there is a period during which the ACK bit of the received data is recessive ("H"). As shown in FIG. 5(c), a signal during the period when it is recessive ("H") is extracted as the result Q of the logical operation of the ACK bit of the transmission data and the received data. In the following explanation, this extracted signal is called a delay time pulse.

FIG. 6 is a diagram showing an example of the configuration of the delay time calculation unit 6 and the delay judgment unit 7. The delay time calculation unit 6 performs the above-mentioned logical operation by the logical operation unit 61, and outputs the extracted delay time pulse to the counter unit 62. The counter unit 62 samples the delay time pulse using a clock (for example, about 100 times the communication speed) faster than the bit time of the communication speed, thereby measuring the time width with high accuracy. The fast clock here means a clock that can measure the time width of the delay time pulse with a certain degree of accuracy in order to calculate the delay time of the communication path, and can be selected appropriately. The delay time pulse indicates that the delay is increasing when the time width becomes shorter. The delay time calculation unit 6 calculates the delay time from the time width of the delay time pulse and outputs it to the delay judgment unit 7. Since the delay time of the communication path is the time width of the ACK bit minus the time width of the delay time pulse, the time width of the delay time pulse itself can be treated as the same as the delay time. Therefore, the delay time calculation unit 6 may output the time width of the delay time pulse itself to the delay judgment unit 7 as the calculated delay time. Alternatively, the delay time or the fluctuation in the time width of the delay time pulse from the state of the communication path after the communication path is opened or maintained as the starting point may be output as the calculated delay time.

The delay time depends on the length of time from when the CAN controller 4 transmits a recessive ACK bit until when it receives a dominant ACK bit set by the CAN controller 14. The delay determination unit 7 or the control unit 3 continuously monitors for signs of communication problems caused by delays in the communication path based on fluctuations in the delay time. The delay determination unit 7 reads out the threshold value stored in the memory 32, and the comparison unit 71 compares the delay time with the threshold value, and outputs delay determination information.

To detect signs of communication failure, the threshold is set based on a delay time shorter than the limit value of the delay time at which a communication failure occurs. The short delay time here is set with a certain margin from the limit value, taking into account the stable operation of the communication system. Figure 7 shows the ACK bit portion of the ACK slot extracted from the data string in Figure 5, and shows a schematic diagram of the relationship between the time width of the delay time pulse and the threshold value. The sections A-B, A-C, and A-D indicated by arrows correspond to the delay time, respectively. Section A-B corresponds to the delay time when the communication path is opened, or when a part is replaced for maintenance and the state is similar to that when the path is opened. Section A-D indicates the limit value of the delay time, and if the delay time becomes longer than this, a communication failure occurs. Section A-C corresponds to the above-mentioned threshold, and is set as a tolerance value within the range in which stable communication is possible with a delay time shorter than the limit value. Therefore, even if the delay time reaches the threshold, stable communication is guaranteed to continue.

The delay determination unit 7 compares the delay time calculated by the delay time calculation unit 6 (including the time width of the delay time pulse, or the fluctuation of the delay time or the time width of the delay time pulse starting from the state of the communication path after the communication path is opened or maintained) with a threshold value, and outputs delay determination information. The delay determination information indicates the result of comparing the delay time with the threshold value, and includes information that the delay time is less than the threshold value, or that the delay time is equal to or greater than the threshold value. When the delay determination unit 7 determines that the delay time is equal to or greater than the threshold value, the control unit 3 detects a sign of a communication malfunction caused by a delay in the communication path based on the output delay determination information. Note that although the condition is that the delay time is equal to or greater than the threshold value, the condition that the delay time is equal to or greater than the threshold value includes the condition that the delay time exceeds the threshold value, and therefore this condition may be replaced with the delay time exceeding the threshold value, and there is no substantial difference between them. Similarly, in the following explanation, the condition is that the delay time is equal to or greater than the threshold value, but the condition may be that the delay time "exceeds" the threshold value.

As an additional configuration, a listen-only function that can be used when the first communication device 1 is connected to multiple other communication devices as a master (i.e., in the case of one-to-many communication) is described. This function identifies other communication devices that respond with an ACK bit by sending a listen-only request from the first communication device 1 in order to measure the delay time of the communication path. In the modified communication system shown in FIG. 8, it is assumed that communication devices 101, 102, and 103 corresponding to the above-mentioned second communication device are connected to the first communication device 1. When a listen-only request is issued from the first communication device 1 to the communication devices 101 and 102, the communication devices 101 and 102 transition from the normal communication mode to the listen-only mode. In this mode, the communication devices 101 and 102 do not respond with an ACK bit even if they receive data transmitted from the first communication device 1. Since the communication device 103 is in normal communication mode, when it receives data transmitted from the first communication device 1, it responds by changing the ACK bit from recessive to dominant as described above. In other words, by using this function for multiple communication devices connected to the first communication device 1 in one-to-many communication, the first communication device 1 can extract the ACK bit from a specified communication device. Since the listen-only function partially restricts communication with devices other than the specified communication device, it is more desirable to use it in situations where communication is not affected, such as during test runs or maintenance.

As an additional configuration, as shown in FIG. 9, the first communication device 1 may be provided with an alarm unit 9 that turns on a fail lamp and displays a warning on the display of the control panel. FIG. 9 is a diagram showing a modified example of a communication system. When the delay determination unit 7 determines that the delay time is equal to or greater than a threshold, the control unit 3 outputs a command to the alarm unit 9, and the alarm unit 9 notifies the outside of a sign of a communication failure caused by a delay in the communication path. Alternatively, the delay determination unit 7 may directly issue a command to the alarm unit 9. This enables predictive maintenance to be performed by systematically stopping communication and replacing parts that cause delays in the communication path.

As an additional configuration, in comparing the delay time with the threshold value, the delay determination unit 7 repeats the comparison multiple times and outputs delay determination information based on the results of the multiple comparisons. Misjudgments may occur due to fluctuations in the time width of the delay time pulse and measurement errors of the counter unit 62, and by making a judgment based on multiple comparisons, it is possible to improve the accuracy of detecting signs of malfunctions caused by delays in the communication path.

As an additional configuration, the difference between the delay time predicted from the installation information of the communication path and the delay time calculated by the delay time calculation unit 6 may be compared with a threshold value. For example, the threshold value is set to be less than 20% of the difference between the predicted delay time calculated from the installation information of the communication path and the delay time calculated by the delay time calculation unit 6, and if the delay determination unit 7 determines that the difference between the predicted delay time and the calculated delay time is equal to or greater than the threshold value, it detects that there is a sign of a communication failure due to delay in the communication path even if communication can continue. This makes it possible to detect a sign of a communication failure before the delay time increases cumulatively to reach the threshold value due to characteristic deterioration such as aging. For example, this leads to early detection of initial defects after the opening of a communication path or after maintenance is performed.

Examples of information included in the installation information of the communication path include basic information of the communication system such as the length of the communication line 8 and the communication speed, the installation environment of the communication cable in which the communication lines 8 are bundled, the expected temperature fluctuation range of the communication cable depending on the load situation, and a table in which the basic information, temperature fluctuation, and usage time correspond to the delay time predicted from these. Then, the delay time is predicted based on the actual communication cable length, communication speed, and temperature measurement value, the information on the usage time of the communication cable, and the installation information. Parameters related to the delay time other than the above may be included. Note that, for the above table, for example, the relationship between the installation information and the delay time predicted from the installation information can be calculated in advance based on theoretical prediction or statistical analysis of actual data obtained from the communication system, and the table can be stored in the memory 32. Also, a feature amount can be extracted from the actual data obtained from the communication system, machine learning can be performed, and a learned model that estimates a predicted value of the delay time from the installation information of the communication path can be generated in advance and stored in the memory 32.

Next, the operation of the first communication device 1 will be described using the flowchart in FIG. 10. Transmission data output by the first communication device 1 to the second communication device 11 and reception data, which is a response from the second communication device 11, are input (S101). A delay time pulse is extracted from the ACK bits of the transmission data and the reception data (S102), and the time width of the delay time pulse is measured (S103).

The delay time calculated based on the time width of the measured delay time pulse is compared with a threshold value to determine whether the delay time is equal to or greater than the threshold value (S104). If it is determined that the delay time is less than the threshold value, the processes of steps S101 to S103 are repeated. If it is determined that the delay time is equal to or greater than the threshold value, a communication failure may occur if the delay time increases further with continued use, and therefore the output delay determination information is used to detect a sign of a communication failure caused by a delay in the communication path (S105).

In addition, in Figs. 1 and 9, the delay time calculation unit 6, the delay determination unit 7, and the control unit 3 are configured separately, but the control unit 3 may be configured to include the delay time calculation unit 6 and the delay determination unit 7. The delay determination unit 7 may have its own storage means and hold the threshold value, rather than reading the threshold value from the memory 32.

As described above, the first communication device 1 according to the first embodiment is a communication device that transmits and receives data with other communication devices based on the CAN communication protocol via a communication line 8, and includes a control unit 3 that controls the transmission and reception of data, a delay time calculation unit 6 that receives as input transmission data output from the control unit 3 and reception data output from the other communication device in response to the transmission data, and calculates the delay time of the communication path from the transmission data and an ACK signal included in the reception data, and a delay determination unit 7 that compares the delay time with a threshold value and outputs delay determination information. This configuration makes it possible to detect signs of malfunctions caused by delays in the communication path.

In particular, in elevators, the communication cables are longer than those used in the other applications mentioned above, some reaching hundreds of meters, and because they have a long service life, they are susceptible to delays in the communication path due to temperature fluctuations and deterioration over time. For this reason, the present disclosure, which detects signs of malfunctions caused by delays in the communication path, is suitable for an elevator communication device that communicates between the elevator control panel and the operating equipment of the car or hall. Similarly, in the embodiments described below, the disclosed communication device can be applied to elevator control to form an elevator communication device.

Embodiment 2.
A description will be given of a first communication device 1 according to embodiment 2. The first communication device 1 according to the present disclosure compares the delay time calculated by the delay time calculation unit 6 with a first threshold value and a second threshold value.

In this embodiment, the first threshold and the second threshold are set based on a delay time that is shorter than the delay time limit. The second threshold corresponds to the threshold described in the first embodiment, and is set based on a delay time that is longer than the first threshold. In other words, the second threshold is set for the allowable delay time, and the first threshold is set to preliminarily detect signs of communication problems caused by delays in the communication path before the delay time reaches the second threshold. Note that the number of thresholds is not limited to two, and it is also possible to set three or more thresholds.

The delay determination unit 7 compares the delay time calculated by the delay time calculation unit 6 with a first threshold, and if it determines that the delay time is equal to or greater than the first threshold, outputs first delay determination information to the control unit 3. The delay determination unit 7 then compares the delay time calculated by the delay time calculation unit 6 with a second threshold, and if it determines that the delay time is equal to or greater than the second threshold, outputs second delay determination information to the control unit 3. If the delay time is equal to or greater than the first threshold, the control unit 3 executes a control process that is set according to the first threshold. The control unit 3 executes different control processes when the delay time is equal to or greater than the first threshold and when the delay time is equal to or greater than the second threshold.

As an example of a control process set according to the first threshold, the control unit 3 changes the log data collection conditions to be used for maintenance when the delay time reaches the second threshold. After the delay time reaches the first threshold, the control unit 3 starts recording logs such as the delay time or the time width of the delay time pulse, the ambient temperature of the communication line 8, and the load status of the communication cable. Alternatively, if the log is acquired before the delay time reaches the first threshold, the control unit 3 shortens the period for acquiring the log. By reducing data collection in situations where there is a low possibility of a malfunction while obtaining log data to be used for maintenance, the storage resources of the memory 32 that records the log data can be efficiently utilized. In particular, when the first communication device 1 manages communication with multiple other communication devices as a master, the volume of log data collected from these communication devices becomes large, and such a setting is effective. The log data may be stored in the memory 32 of the first communication device 1 or in an external storage device not shown.

The notification unit 9 may also notify maintenance personnel that the delay time has reached or exceeded the first threshold. When the delay time is less than the second threshold but greater than or equal to the first threshold, preliminary detection of signs of communication failure caused by delays in the communication path can improve predictability of when maintenance will be required, enabling more planned preparation for maintenance. Furthermore, if the period from the previous maintenance until the first threshold is reached is short, some kind of failure may have occurred in the communication path, and it is possible to carry out maintenance and find the defective part early, before the delay time reaches the second threshold.

Next, the operation of the first communication device 1 will be described using the flowchart in FIG. 11. Note that steps common to FIG. 10 in embodiment 1 will be assigned the same step numbers and duplicated descriptions will be omitted.

After the time width of the delay time pulse is measured (S103), it is determined whether the delay time is equal to or greater than a first threshold (S201). If it is determined that the delay time is less than the first threshold, the process returns to before step S101, and monitoring of the delay time continues. If it is determined that the delay time is equal to or greater than the first threshold, a control process set according to the first threshold exemplified above is executed based on the output first delay determination information (S202).

Next, it is determined whether the delay time is equal to or greater than a second threshold (S203). If it is determined that the delay time is less than the second threshold, the process returns to before step S101, and monitoring of the delay time continues. If it is determined that the delay time is equal to or greater than the second threshold, if use continues and the delay time increases, a communication malfunction may occur, so the second delay determination information that is output detects a sign of a communication malfunction caused by a delay in the communication path (S105). Note that step S203 may be executed after step S201, or the determinations of steps S201 and S203 may be executed in parallel, and then steps S202 and S105 may be executed.

As described above, in the communication device 1 according to the second embodiment, the delay determination unit 7 compares the delay time calculated by the delay time calculation unit 6 with at least the first threshold and the second threshold, and the control unit 3 executes different control processes when the delay time is equal to or greater than the first threshold and when the delay time is equal to or greater than the second threshold. With this configuration, it is possible to preliminarily detect signs of malfunctions caused by delays in the communication path and perform maintenance or prepare for maintenance.

Embodiment 3.
A first communication device 1 according to a third embodiment will be described. In this embodiment, the first communication device 1 includes a delay cause estimation unit 10 as shown in Fig. 12. The delay cause estimation unit 10 estimates the cause of a delay when a delay time is equal to or greater than a threshold value.

If the cause of the delay is deterioration over time, the delay time will increase according to the length of time the cable has been used since installation. On the other hand, if the cause of the delay is temperature fluctuations or irregular noise in the communication cable, the delay time may temporarily fluctuate accordingly. For example, if the communication cable temporarily becomes overloaded and the temperature of the communication lines 8 bundled together in the communication cable rises, the delay time will increase due to an increase in the impedance of the communication lines 8. However, when the overload is eliminated, the temperature of the communication cable will drop and the delay time will decrease.

The delay cause estimation unit 10 estimates the cause of the delay time exceeding the threshold value, and estimates whether the cause of the delay is temporary characteristic degradation such as temperature fluctuation. If it is estimated to be temporary characteristic degradation, the control unit 3 adjusts the communication speed within a range that does not affect system communication. Specifically, the first communication device 1, which is the master, transmits baud rate setting change information to the second communication device 11, which is the local, and both the master and local self-reset the processors 31, 131 of the control units 3, 13, thereby slowing down the communication speed and increasing the tolerance for delay, allowing communication to continue.

An example of a cause estimation method of the delay cause estimation unit 10 will be described with reference to FIG. 13. The delay cause estimation unit 10 refers to the relationship between delay time and usage time from the log data. In FIG. 13, the horizontal axis indicates the usage time of the communication path after the communication path is opened or maintained, and the vertical axis indicates the delay time, and the delay time of the communication path at each usage time is plotted. The causes of delay in the communication path include a mixture of temporary characteristic deterioration such as temperature fluctuations and non-temporary characteristic deterioration due to aging. Therefore, as shown in FIG. 13, the delay time at each usage time varies due to the influence of temporary characteristic deterioration. The delay cause estimation unit 10 extracts data on usage time with little influence of delay due to temporary characteristic deterioration from the measured values of the temperature, load status, and environmental noise of the communication cable, and predicts the tendency of the delay time excluding the influence of temporary characteristic deterioration by approximating the data with a straight line or curve. Note that the extracted data as shown in FIG. 13 may be approximated with a band having a certain width instead of approximating with a curve. Such a prediction of the tendency of the delay time excluding the influence of temporary characteristic deterioration may be performed by referring to the delay time predicted from the installation information of the communication path described above.

When the delay time excluding the effects of temporary characteristic degradation is predicted to reach the threshold value at usage time t2, and the threshold value is reached at usage time t1 prior to usage time t2, the delay cause estimation unit 10 refers to data such as the temperature and load status of the communication cable at that time and estimates whether the delay time exceeding the threshold value is due to temporary characteristic degradation. For example, if there is a temporary temperature rise due to the communication cable being overloaded when the threshold value is reached, it is estimated to be temporary characteristic degradation.

The operation of the first communication device 1 will be explained using the flowchart in Figure 14. Note that steps common to Figure 9 in embodiment 1 will be assigned the same step numbers and duplicate explanations will be omitted.

If it is determined in step S104 that the delay time is equal to or greater than the threshold, the cause of the delay is estimated (S301). Next, based on the estimation result, it is determined whether the delay is due to temporary characteristic degradation or not (S302). If the delay is due to temporary characteristic degradation, the communication speed is adjusted (S303). After the communication speed is adjusted, the process returns to before step S101, and monitoring of the delay time continues. On the other hand, if the delay is not due to temporary characteristic degradation, it is estimated that the delay is mainly due to aging, and if the delay time increases with continued use, there is a possibility that a communication failure will occur. Therefore, the output delay determination information is used to detect a sign of a communication failure due to a delay in the communication path (S105).

As described above, the communication device 1 according to the third embodiment includes a delay cause estimation unit 10 that estimates the cause of the delay time exceeding a threshold, and the control unit 3 is configured to adjust the communication speed when the estimated cause of the delay is temporary characteristic degradation. With this configuration, it is possible to continue stable communication by increasing the tolerance for delay.

In the first embodiment, it has been explained that the processor 31 of the control unit 3 may read out a software program stored in the memory 32 to realize the functions of each unit of the first communication device 1, and this is also true in the second and third embodiments. Also, as shown in FIG. 15, each functional unit of the first communication device 1 including the control unit 3 may be realized as a processing circuit 33 that is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination of these. Also, some of the functions of the first communication device 1 may be realized by a software program, and the remaining functions may be realized by a dedicated processing circuit 33.

Although the embodiments of the present disclosure have been described above, the configuration of the first communication device of the present disclosure is not limited to the configurations described in the first to third embodiments. The first communication device 1 of the present disclosure can be combined with another known technology, and it is also possible to omit or change part of the configuration, such as by combining them as appropriate, within the scope of the gist of the present disclosure.

1 First communication device, 2 Communication control board, 3 Control unit, 31 Processor, 32 Memory, 4 CAN controller, 5 CAN transceiver, 6 Delay time calculation unit, 7 Delay determination unit, 8 Communication line, 9 Notification unit, 10 Delay cause estimation unit, 11 Second communication device

Claims (11)

A communication device that transmits and receives data to and from another communication device via a communication line based on a CAN communication protocol,
A control unit for controlling transmission and reception of data;
a delay time calculation unit that receives transmission data output from the control unit and reception data output from the other communication device as a response to the transmission data, and calculates a delay time of a communication path from a signal set in an ACK bit of the transmission data and an acknowledgment response signal set in an ACK bit included in the reception data;
A communication device comprising a delay determination unit that compares the delay time with a threshold value and outputs delay determination information. The communication device according to claim 1, characterized in that the threshold is set based on a delay time that is shorter than the limit value of the delay time at which a communication failure occurs. The communication device according to claim 1 or 2, characterized in that the delay time calculation unit is provided with a logical operation unit, and extracts a delay time pulse for calculating the delay time from the signal set in the ACK bit and the acknowledgment response signal by taking the logical product of the transmission data and the received data with the logic inverted. 4. The communication device according to claim 1, wherein the delay time calculation unit includes a counter unit and measures the time width of the delay time pulse using a clock that is faster than a bit time of a communication speed. A communication device as described in any one of claims 1 to 4, characterized in that when the communication device is connected to multiple other communication devices, the communication device transmits a listen-only request to identify other communication devices that will respond with the confirmation response signal in order to measure the delay time of the communication path. The communication device according to any one of claims 1 to 5, characterized in that the delay determination unit repeats a comparison of the delay time with the threshold value multiple times and outputs delay determination information based on the results of the multiple comparisons. The communication device according to any one of claims 1 to 6, characterized in that the delay determination unit compares the difference between the delay time predicted from the communication path installation information and the delay time calculated by the delay time calculation unit with a threshold value. The delay determination unit compares a first threshold value and a second threshold value that is set based on a delay time longer than the first threshold value with the delay time calculated by the delay time calculation unit;
8. The communication device according to claim 1, wherein the control unit executes different control processes when the delay time is equal to or greater than the first threshold value and when the delay time is equal to or greater than the second threshold value. a delay cause estimation unit that estimates a cause of the delay time being equal to or greater than the threshold,
The communication device according to claim 1 , wherein the control unit adjusts a communication speed when the delay is caused by temporary deterioration of characteristics. An elevator communication device in which the communication device according to any one of claims 1 to 9 is applied to elevator control. A communication method for transmitting and receiving data to and from another communication device via a communication line based on a CAN communication protocol, comprising:
A step of receiving transmission data and reception data output from the other communication device as a response to the transmission data, and calculating a delay time of a communication path from a signal set in an ACK bit of the transmission data and an acknowledgment response signal set in an ACK bit included in the reception data;
comparing the delay time with a threshold value;
and outputting delay determination information based on a comparison of the delay time with the threshold value.

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