JP7190964B2 - Communication error detector - Google Patents

Description

The present disclosure relates to a communication abnormality detection device.

A bus based on CAN (Controller Area Network) is known as a typical in-vehicle network. A short-circuit state of a pair of communication lines (hereinafter referred to as "communication line short-circuit abnormality") is known as one of the types of abnormalities that can occur in a CAN-based bus.

Japanese Unexamined Patent Application Publication No. 2016-20185

By the way, in addition to a mode in which a short circuit state occurs continuously, there is a mode in which a short circuit state occurs intermittently as modes of short circuit abnormality in a communication line. Even in such a mode in which a short-circuit state occurs intermittently, it may be useful to detect a short-circuit abnormality in a communication line. In the conventional technology, it is difficult to detect a short-circuit abnormality in a communication line in a mode in which such a short-circuit state occurs intermittently.

SUMMARY OF THE INVENTION An object of the present invention is to detect a short-circuit abnormality in a communication line in a mode in which a short-circuit state occurs intermittently.

According to the present invention, there is provided a communication abnormality detection device in a communication system that performs communication based on a potential difference between a pair of communication lines,
a determination unit that determines whether or not the pair of communication lines is in a short-circuit state at predetermined intervals;
changing a first counter value by a first predetermined value in a first direction, which is either an increasing direction or a decreasing direction, when the determination unit determines that the short-circuit state exists at every predetermined period; a counter updating unit that changes a second counter value by a second predetermined value in a second direction, which is either an increasing direction or a decreasing direction, when the determining unit determines that the short-circuit state does not exist;
short-circuit abnormality detection for detecting a short-circuit abnormality in the pair of communication lines when the first counter value exceeds a first threshold on the first direction side with respect to the first predetermined value in the first direction; Department and
a reset unit that resets the first counter value when the second counter value exceeds the second threshold in the second direction with respect to the second predetermined value. A communication anomaly detection device is provided.

According to the present invention, it is possible to detect a short-circuit abnormality in a communication line in a mode in which a short-circuit state occurs intermittently.

1 is a schematic diagram showing an example of the overall configuration of a communication system 1 using a bus 2 based on CAN; FIG. FIG. 4 is a schematic diagram showing a hardware configuration example of a node Nd1; 2 is a schematic diagram showing a functional configuration example of a microcomputer 10 of a node Nd1; FIG. 4 is a schematic flow chart showing an example of short-circuit abnormality detection processing executed by the microcomputer 10; 7 is a schematic flow chart showing an example of short-circuit abnormality detection processing according to a comparative example; FIG. 7 is a diagram showing a history example of determination results of determination unit 110 when short-circuit states occur continuously; FIG. 7 is a diagram showing a history example of determination results of determination unit 110 when a short-circuit state occurs intermittently. FIG. 10 is a diagram showing an example of detection history of a short-circuit state that is preferably detected as a short-circuit abnormality; 4 shows an example of detection history of a short-circuit state that is preferably not detected as a short-circuit abnormality.

Each embodiment will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an overall configuration example of a communication system 1 using a bus 2 based on CAN (Controller Area Network).

The communication system 1 includes a CAN-based bus 2 and a plurality of nodes Nd (only nodes Nd1-Nd2 are shown).

The bus 2 is composed of a pair of communication lines (denoted as “CAN-H” and “CAN-L” in FIG. 1, etc.). A communication system 1 is an example of a communication system that performs communication based on a potential difference between a pair of communication lines CAN-H and CAN-L.

A plurality of nodes Nd are connected to the bus 2 . Note that the number of nodes is arbitrary. A plurality of nodes Nd can communicate with each other based on the potential difference between the pair of communication lines CAN-H and CAN-L. That is, multiple nodes Nd can communicate in a two-wire differential voltage scheme. Specifically, any one of the plurality of nodes Nd can transmit a message to the bus 2 and other nodes can receive the message from the bus 2 . The messages are CAN compliant and the CAN_ID (identification) of the message indicates the priority. The data field of the message includes various vehicle information, control information, and the like.

Next, the configuration inside the node Nd1 will be described as a representative of the node Nd1 among the plurality of nodes Nd.

FIG. 2 is a schematic diagram showing a hardware configuration example of the node Nd1.

Node Nd1 includes a microcomputer 10 (hereinafter referred to as "microcomputer 10"), a CAN transceiver 20, and a termination circuit 21, as shown in FIG.

The microcomputer 10 may form, for example, an ECU (Electronic Control Unit). In this case, the ECU may be an ECU that controls the electric power steering device. The microcomputer 10 includes a CPU 11, a ROM 12, a RAM 13, etc., and a CAN controller 14 therein. The CAN controller 14 performs various communication processes and the like via the bus 2 using the CAN transceiver 20 .

The CAN transceiver 20 transmits and receives electrical signals (messages) defined by CAN. This electrical signal is recessive when the potential difference between the pair of communication lines CAN-H and CAN-L is equal to or less than the threshold, and is dominant when the potential difference is greater than the threshold.

If the dominant (“0”) and the recessive (“1”) are simultaneously transmitted on the bus 2, the dominant is given priority. This ensures that high priority messages take precedence over low priority messages. Specifically, the numbers of the CAN_ID are transmitted to the bus 2 in binary notation in descending order. Among a plurality of messages, a message having "0" first in descending order has priority over a message having "1" in the same order. Here, the smaller the number of CAN_ID, the higher the position of "0" in binary notation. For example, if the number of the CAN_ID is "9", it is "1001" in binary notation. CAN_ID "9" with "0" has priority over CAN_ID "10" with the third highest value of "1".

The priority given to each message is determined by the vehicle system designer to maintain the desired health of the vehicle system. In general, messages related to vehicle cruise control (run, stop, turn) are given relatively high priority. Messages related to vehicle travel control include, for example, messages related to braking force control, driving force control, and steering control. On the other hand, messages related to controls that enhance convenience and comfort (eg climate control) are given relatively low priority.

The termination circuit 21 is connected between the pair of communication lines CAN-H and CAN-L and terminates the bus 2 with a predetermined resistance value.

FIG. 3 is a schematic diagram showing a functional configuration example of the microcomputer 10 of the node Nd1.

The microcomputer 10 includes a determination section 110, a counter update section 112, a reset section 114, and a short-circuit abnormality detection section 116, as shown in FIG. The determination unit 110 , the counter update unit 112 , the reset unit 114 , and the short-circuit abnormality detection unit 116 can be realized by the CAN controller 14 or the CPU 11 executing the program in the ROM 12 .

The determining unit 110 determines whether or not the paired communication lines CAN-H and CAN-L are in a short-circuit state at predetermined intervals ΔT1. For example, the determination unit 110 determines that the node is in the short-circuit state when the own node transmits dominant and receives recessive, and determines that the node is not in the short-circuit state when the node transmits dominant and receives dominant. . The predetermined period ΔT1 may be a constant period, or may be an irregular period (for example, a period each time the own node transmits a dominant).

In the following, for convenience of explanation, the determination unit 110 outputs the determination result as a binary value every predetermined period ΔT1, and one of the binary values indicates that there is a short-circuit state between the pair of communication lines CAN-H and CAN-L. It represents the determined determination result, and is also written as "H: Abnormal". The other of the two values represents the result of determination that there is no short-circuit state between the paired communication lines CAN-H and CAN-L, and is also written as "L: normal".

The counter update unit 112 updates the value of the abnormality counter C1 (example of the first counter value) every predetermined period ΔT1, which is the same as the determination period of the determination unit 110, when the determination result of the determination unit 110 is "H: abnormal". is incremented by a first predetermined value ("1" in this example), and if the determination result of the determination unit 110 is "L: normal", the value of the normal counter C2 (example of the second counter value) is increased to the second It is incremented by a predetermined value ("1" in this example).

The reset unit 114 resets the value of the abnormal counter C1 to an initial value (for example, 0) when the value of the normal counter C2 exceeds a predetermined threshold Th2 (an example of the second threshold). The predetermined threshold Th2 is an arbitrary value equal to or greater than the second predetermined value and is a suitable value.

Moreover, the reset unit 114 resets the value of the normality counter C2 to an initial value (for example, 0) when the value of the normality counter C2 exceeds the predetermined threshold value Th2.

Moreover, the reset unit 114 resets the value of the normality counter C2 to an initial value (for example, 0) when the determination result of the determination unit 110 is “H: Abnormal”. Note that, in a modification, the reset unit 114 may reset the value of the normality counter C2 to an initial value (for example, 0) when the determination result of the determination unit 110 is "H: Abnormal" continuously. .

The short-circuit abnormality detection unit 116 detects a short-circuit abnormality between the pair of communication lines CAN-H and CAN-L when the value of the abnormality counter C1 exceeds a predetermined threshold Th1 (an example of the first threshold). The predetermined threshold Th1 is an arbitrary value equal to or greater than the first predetermined value, and is a suitable value.

Of the plurality of nodes Nd, all or some of them other than node Nd1 may have the same units 110 to 116 as node Nd1, or all other than node Nd1 It is not necessary to have each part 110-116.

FIG. 4 is a schematic flow chart showing an example of short-circuit abnormality detection processing executed by the microcomputer 10. As shown in FIG. The short-circuit abnormality detection process in FIG. 4 is repeatedly executed at predetermined intervals ΔT1.

First, in step S400, the microcomputer 10 determines whether or not the confirmed state is "normal". The confirmed state has two values of "normal" and "abnormal", and the state in which the short-circuit abnormality is detected by the short-circuit abnormality detection unit 116 corresponds to the confirmed state="abnormal". The initial value of the definite state is "normal". If the confirmed state is "normal", the process proceeds to step S402; otherwise, the process for this cycle ends.

In step S402, the microcomputer 10 determines whether or not the determination result of the determination unit 110 for the current cycle is "L: normal". If the determination result of the determining unit 110 for the current period is "L: normal", the process proceeds to step S404, otherwise the process proceeds to step S410.

At step S404, the microcomputer 10 increments the value of the normality counter C2 by "1".

In step S406, the microcomputer 10 determines whether or not the value of the normality counter C2 exceeds a predetermined threshold Th2. If the value of the normality counter C2 exceeds a predetermined threshold value Th2 (for example, "9"), the process proceeds to step S408; otherwise, the process for this cycle ends.

In step S408, the microcomputer 10 resets the value of the normal counter C2 to "0" and resets the value of the abnormal counter C1 to "0".

At step S410, the microcomputer 10 increments the value of the abnormality counter C1 by "1" and resets the value of the normality counter C2 to "0".

In step S412, the microcomputer 10 determines whether or not the value of the abnormality counter C1 has exceeded a predetermined threshold Th1. If the value of the abnormality counter C1 exceeds a predetermined threshold value Th1 (for example, "9"), the process proceeds to step S414; otherwise, the process for this cycle ends.

In step S414, the microcomputer 10 sets the confirmed state to "abnormal". If the definite state is set to "abnormal", a short circuit fault is signaled. For example, a notification to that effect may be output to the outside, or diagnostic information indicating the short circuit abnormality may be generated.

Here, with reference to FIG. 5 and subsequent figures, the effect of this embodiment will be described while comparing it with a comparative example.

FIG. 5 is a schematic flow chart showing an example of short-circuit abnormality detection processing according to a comparative example. The short-circuit abnormality detection process according to the comparative example shown in FIG. 5 differs from the short-circuit abnormality detection process according to the present embodiment shown in FIG. 4 in that step S500 is executed instead of steps S404 to S408. At step S500, the value of the abnormality counter C1 is reset to "0".

By the way, the short-circuit state of the pair of communication lines CAN-H and CAN-L may occur intermittently instead of continuously.

FIG. 6A is a diagram showing a history example of the determination results of the determination unit 110 when the short-circuit state occurs continuously, and FIG. 6B is a diagram of the determination result of the determination unit 110 when the short-circuit state occurs intermittently. It is a figure which shows the example of a log|history. 6A and 6B each show a history (time series) of determination results of the determination unit 110 from the top.

In the example shown in FIG. 6A, the determination result of determination unit 110 transitions from "L: normal" to "H: abnormal" from time t1, and thereafter, the determination result of determination unit 110 continues to be "H: abnormal". ing. On the other hand, in the example shown in FIG. 6B , although the determination result of determination unit 110 transitions from “L: normal” to “H: abnormal” from time t2, the determination result of determination unit 110 immediately thereafter changes to “ L: normal”. Then, after that, the determination result of the determination unit 110 again transitions from time t4 "L: normal" to "H: abnormal". Also in this case, the determination result of determination unit 110 becomes "L: normal" immediately after that at time t5.

In the comparative example, a short-circuit abnormality can be detected when the short-circuit state occurs continuously as shown in FIG. 6A. Specifically, when the short-circuit state occurs continuously, the determination result in step S402 is continuously "NO" until the value of the abnormality counter C1 exceeds the predetermined threshold value Th1, so step S500 functions. Without doing so, the definite state is set to "abnormal".

On the other hand, in the comparative example, when the short-circuit state occurs intermittently as shown in FIG. 6B, there are relatively many cases where the short-circuit abnormality cannot be detected. Specifically, when the short-circuit state occurs intermittently, it depends on the relationship between the duration of the series of short-circuit states and the predetermined threshold value Th1. In many cases, it does not become "NO" continuously until the threshold value Th1 is exceeded. If the determination result in step S402 does not continuously become "NO" until the value of the abnormality counter C1 exceeds the predetermined threshold value Th1, step S500 functions and the value of the abnormality counter C1 is reset. In this case, even if the next short-circuit state (for example, a short-circuit state that transitions from time t4 “L: normal” to “H: abnormal” at time t4 in FIG. 6B) occurs, the difference between the duration of the short-circuit state and the predetermined threshold Th1 Depending on the relationship, the value of the abnormality counter C1 is reset again.

In this way, in the comparative example, when the short-circuit state occurs intermittently, the short-circuit abnormality is detected over a relatively long period of time by resetting the value of the abnormality counter C1 at the end of each short-circuit state. Impossible situations tend to persist.

On the other hand, according to the present embodiment, there is a high possibility that a short-circuit abnormality can be detected not only when the short-circuit state occurs continuously, but also when the short-circuit state occurs intermittently.

That is, in the present embodiment, as in the case of the comparative example, a short-circuit abnormality can be detected when the short-circuit state occurs continuously as shown in FIG. 6A. Specifically, when the short-circuit state occurs continuously, the determination result in step S402 is continuously "NO" until the value of the abnormality counter C1 exceeds the predetermined threshold value Th1, so step S500 functions. Without doing so, the definite state is set to "abnormal".

On the other hand, in the present embodiment, the possibility of not being able to detect the short-circuit abnormality can be appropriately reduced when the short-circuit state occurs intermittently as shown in FIG. 6B. Specifically, when the short-circuit state occurs intermittently, it depends on the relationship between the duration of the series of short-circuit states and the predetermined threshold value Th1. In many cases, it does not become "NO" continuously until the threshold value Th1 is exceeded. If the determination result in step S402 does not continuously become "NO" until the value of the abnormality counter C1 exceeds the predetermined threshold value Th1, instead of step S500, the value of the normal counter C2 is first incremented in step S404, and then Only when the value of the normality counter C2 exceeds the predetermined threshold value Th2 in step S406, step S408 functions to reset the value of the abnormality counter C1. In this manner, in this embodiment, even if there is a period during which the short-circuit state is not detected temporarily, the value of the abnormality counter C1 is not reset as long as the value of the normality counter C2 does not exceed the predetermined threshold value Th2. do not have. Therefore, when the next short-circuit state (for example, a short-circuit state that transitions from "L: normal" to "H: abnormal" at time t4 in FIG. 6B) occurs, the relationship between the duration of the short-circuit state and the predetermined threshold value Th1 , the short-circuit abnormality can be detected when the value of the abnormality counter C1 exceeds the predetermined threshold value Th1.

Here, with reference to FIGS. 7A and 7B, an operation example of this embodiment will be described.

7A and 7B are explanatory diagrams of the short-circuit abnormality detection process of FIG. 4. FIG. 7A shows a detection history example of a short-circuit state that is preferably detected as a short-circuit abnormality, and FIG. 1 shows an example of a detection history of a short-circuit state that is preferably not detected. 7A and 7B show, from the top, the history (time series) of the judgment result of the judgment unit 110, the time series of the value of the abnormality counter C1, the time series of the value of the normal counter C2, and the time series of the confirmed state. .

In FIG. 7A, the short circuit state is intermittently detected at relatively short intervals ΔT5. In this way, when the short-circuit state occurs intermittently at relatively short intervals ΔT5, there is a high possibility that the short-circuit abnormality to be notified is high, and therefore it is preferably detected as a short-circuit abnormality.

On the other hand, in FIG. 7B, a short circuit condition is detected after a relatively long interval ΔT5. In this way, when the short-circuit state occurs multiple times at relatively long intervals ΔT5, it is considered highly likely that it is caused by other factors such as noise. Therefore, it is preferable not to detect it as a short circuit anomaly.

In this regard, according to the present embodiment, by appropriately setting the predetermined threshold Th1 and the predetermined threshold Th2, when the short-circuit state occurs intermittently at relatively short intervals ΔT5 as shown in FIG. , while detecting a short-circuit fault, it is possible not to detect a short-circuit fault when short-circuit conditions occur at relatively long intervals ΔT5, as shown in FIG. 7B.

Specifically, in the examples shown in FIGS. 7A and 7B, the predetermined threshold Th1 and the predetermined threshold Th2 are both "9".

In FIG. 7A, the value of the normal counter C2 increases during the period corresponding to the interval ΔT5, but since the interval ΔT5 is relatively short, the value of the normal counter C2 only increases to "2" or "3". , the predetermined threshold value Th2=“9” is not exceeded. Therefore, the value of normality counter C2 is reset to "0" at the end of interval ΔT5 (ie when the short circuit condition is again detected). As a result, the value of the fault counter C1 is not reset due to the relatively short interval ΔT5, and in FIG. 7A, when the fourth short circuit condition is detected (see time t9 in FIG. 7A), A short-circuit abnormality is detected when the value of the counter C1 exceeds the predetermined threshold Th1 (that is, the determined state becomes "abnormal").

In contrast, in FIG. 7B, the value of the normal counter C2 increases during the period corresponding to the interval ΔT5, but since the interval ΔT5 is relatively long, the value of the normal counter C2 reaches “10” (that is, exceeding the predetermined threshold Th2=“9”). Therefore, the value of the abnormal counter C1 (and the value of the normal counter C2) are reset to "0" during the interval ΔT5 (see time t10 in FIG. 7B). As a result, the value of the anomaly counter C1 is reset due to the relatively long interval ΔT5, and in FIG. 7A, the value of the anomaly counter C1 is reset even if the second short circuit condition is detected (see time t11 in FIG. 7B). It is incremented from "0". Therefore, the detection of the first short-circuit state is substantially masked and does not affect the determination of the short-circuit abnormality based on the second short-circuit state.

In this manner, according to the present embodiment, the relatively short interval ΔT5 when the possibility of the short-circuit abnormality to be notified is high and the relatively long interval ΔT5 when the possibility of the short-circuit abnormality to be notified is low. By using the difference to set an appropriate predetermined threshold value Th2 that can separate these, it is possible to increase the detection accuracy of the short-circuit abnormality (the possibility that only the short-circuit abnormality to be notified is detected as the short-circuit abnormality). .

By the way, the detection of the first short-circuit state in FIG. 7B may occur due to factors such as noise that are unrelated to the short-circuiting of the pair of communication lines CAN-H and CAN-L. In such cases, the duration ΔT6 of detection of a short circuit condition is relatively short. On the other hand, even in the case of FIG. 7A, the duration ΔT6 of detection of a short circuit condition is similarly relatively short.

Therefore, if the predetermined threshold value Th1 is set too small with respect to such a relatively short duration ΔT6, factors unrelated to the short-circuiting of the paired communication lines CAN-H and CAN-L, such as noise, Due to the detection of the short circuit condition that occurs, there is a high probability that the short circuit anomaly will be detected.

In this regard, in FIGS. 7A and 7B, the predetermined threshold Th1 is set to work only for a significantly long duration with respect to such a relatively short duration ΔT6, so that noise, etc. It is possible to reduce the possibility of detecting a short-circuit abnormality due to a factor unrelated to the short-circuit of the communication lines CAN-H and CAN-L.

In this manner, the predetermined threshold Th2 is appropriately set so as to match the relatively short interval ΔT5 that occurs at the time of the short-circuit abnormality in the mode in which the short-circuit state occurs intermittently. However, it may be set appropriately so as not to react to the relatively short duration ΔT6 caused by factors unrelated to the short circuit of the pair of communication lines CAN-H, CAN-L.

Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes are possible within the scope described in the claims. It is also possible to combine all or more of the constituent elements of the above-described embodiments.

For example, in the above-described embodiment, the value of the abnormality counter C1 is changed in the increasing direction (example of the first direction) each time the determination result of the determination unit 110 is "H: abnormal", but this is not the only option. can't That is, the value of the abnormality counter C1 may be changed in the decreasing direction (example of the first direction) each time the determination result of the determination unit 110 is "H: abnormal". In this case, the initial value of the abnormality counter C1 may be, for example, "predetermined threshold value Th1+1", and when the value of the abnormality counter C1 becomes smaller than 1, the short-circuit abnormality may be detected.

Similarly, in the above-described embodiment, the value of the normality counter C2 is changed in the increasing direction (example of the second direction) each time the determination result of the determination unit 110 is "L: normal". Not limited. That is, the value of the normality counter C2 may be changed in the decreasing direction (example of the second direction) each time the determination result of the determination unit 110 is "L: normal". In this case, the initial value of the normal counter C2 is, for example, "predetermined threshold value Th2+1", and when the value of the normal counter C2 becomes smaller than 1, the value of the abnormal counter C1 and the value of the normal counter C2 are reset. good.

<Appendix>
In addition, the following additional remarks will be disclosed with respect to the above examples.

[Appendix 1]
A communication abnormality detection device (for example, a microcomputer 10) in a communication system that performs communication based on a potential difference between a pair of communication lines (for example, a pair of communication lines CAN-H and CAN-L),
a determining unit (e.g., determining unit 110) that determines the presence or absence of a short-circuit state of the pair of communication lines at predetermined intervals;
If the determination unit determines that the short-circuit state exists at each predetermined period, the first counter value (eg, the value of the abnormality counter C1) is increased by a first predetermined value (eg, "1"), or When it is changed (eg, incremented) in the first direction, which is one of the decreasing directions, and the determination unit determines that there is no short-circuit state, the second counter value (eg, the value of the normal counter C2) is set to the second value. a counter updating unit (eg, counter updating unit 112) that changes (eg, increments) a second direction, which is either an increasing direction or a decreasing direction, by a predetermined value (eg, “1”);
When the first counter value exceeds the first threshold (for example, a predetermined threshold Th1) located on the first direction side with respect to the first predetermined value in the first direction, the short-circuit abnormality of the pair of communication lines A short-circuit abnormality detection unit (for example, a short-circuit abnormality detection unit 116) that detects
resetting the first counter value when the second counter value exceeds, in the second direction, a second threshold (for example, a predetermined threshold Th2) located on the second direction side with respect to the second predetermined value; and a reset unit (for example, reset unit 114).

According to Supplementary Note 1, for example, when both the first direction and the second direction are increasing directions, even if the first counter value becomes larger than the first predetermined value, it does not exceed the first threshold (for example, the predetermined threshold Th1). In this case, the short-circuit abnormality of the pair of communication lines is not detected. Therefore, it is possible to reduce the possibility of detecting a short-circuit abnormality in the pair of communication lines due to noise or the like. On the other hand, if the first threshold is relatively large, the robustness against noise can be enhanced, but on the other hand, it becomes difficult to detect a short-circuit abnormality based on a short-circuit state that occurs in a mode in which a short-circuit state occurs intermittently. This is because, in the mode in which the short-circuit state occurs intermittently, the period during which the determination unit determines that there is a short-circuit state is the same as the period during which the determination unit determines that there is a short-circuit state due to noise or the like. This is because it tends to be relatively short.

In this regard, according to Supplementary Note 1, even if the second counter value becomes larger than the second predetermined value, if it does not exceed the second threshold value (for example, the predetermined threshold value Th2), the first counter value is not reset. do not have. This makes it difficult to reset the first counter value even when the determination unit temporarily determines that there is no short-circuit state due to the mode in which the short-circuit state occurs intermittently. As a result, it becomes possible to detect a short-circuit abnormality in a communication line in a mode in which a short-circuit state occurs intermittently.

In this manner, according to Supplementary Note 1, it is possible to detect a short-circuit abnormality in a communication line in a mode in which a short-circuit state occurs intermittently while ensuring robustness against noise.

[Appendix 2]
The communication abnormality detection device according to appendix 1, wherein the reset unit further resets the second counter value when the determination unit determines that the short-circuit state exists.

According to Supplementary Note 2, the second counter value is reset when it is determined that there is a short-circuit state, so the second counter value increases without being reset in a mode in which the short-circuit state occurs intermittently. Inconvenience resulting from this (that is, inconvenient that the second counter value exceeds the second threshold value and the first counter value is reset) can be reduced.

[Appendix 3]
3. The communication abnormality detection device according to appendix 1 or 2, wherein the pair of communication lines form a bus (for example, bus 2) based on CAN (Controller Area Network).

According to Supplementary Note 3, in a communication system using a CAN-based bus, it is possible to detect a short-circuit abnormality in a communication line in a mode in which a short-circuit state occurs intermittently.

1 Communication system 2 Bus 10 Microcomputer 14 CAN controller 20 CAN transceiver 21 Termination circuit 110 Judgment unit 112 Counter update unit 114 Reset unit 116 Short circuit abnormality detection unit C1 Abnormal counter C2 Normal counter CAN-H Communication line CAN-L Communication line Nd Node Nd1 node Nd2 node

Claims (3)

A communication abnormality detection device in a communication system that performs communication based on a potential difference between a pair of communication lines,
a determination unit that determines whether or not the pair of communication lines is in a short-circuit state at predetermined intervals;
changing a first counter value by a first predetermined value in a first direction, which is either an increasing direction or a decreasing direction, when the determination unit determines that the short-circuit state exists at every predetermined period; a counter updating unit that changes a second counter value by a second predetermined value in a second direction, which is either an increasing direction or a decreasing direction, when the determining unit determines that the short-circuit state does not exist;
Short-circuit abnormality detection for detecting a short-circuit abnormality in the pair of communication lines when the first counter value exceeds the first threshold on the first direction side with respect to the first predetermined value in the first direction. Department and
resetting the first counter value and the second counter value when the second counter value exceeds the second threshold in the second direction with respect to the second predetermined value; and a reset unit that resets the communication error detection device. 2. The communication error detection device according to claim 1, wherein the reset unit further resets the second counter value when the determination unit determines that the short-circuit state exists. 3. The communication abnormality detection device according to claim 1, wherein said pair of communication lines form a bus based on CAN (Controller Area Network).

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