JP2007160976A - Vehicular network system and network node - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular network system capable of eliminating any delay error included in time information as much as possible, when a plurality of sensors are connected thereto via a communication network to use the time information. <P>SOLUTION: A node 9 which is arranged in the middle of an in-vehicle LAN 8 to relay information transmitted from each sensor or the like receives the time stamp data T(n) transmitted from any one of them, and obtains the delay time Δt from the time stamp data T(n) and the reference time Ts(n) acquired from a GPS receiver 14 or a wave clock 15 equipped on the node. When the delay time Δtc corrected according to the communication situation on the in-vehicle LAN 8 is obtained when receiving the time stamp data T(n), time information T(n+1) is generated and transmitted to a body ECU. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle network system for transmitting information detected by sensors connected to at least a part of a plurality of sensors arranged in each part of a vehicle, and a network node used in the system.

  Sensor fusion is a technique for improving the detection accuracy of a specific detection target by integrating information obtained by a plurality of types of sensors, and examples thereof are disclosed in Patent Documents 1 and 2 and the like. Assuming that this technology is applied to a vehicle, for example, it is recognized from absolute position ranging information obtained by using GPS (Global Positioning System), relative position ranging information obtained from a laser radar, and an image captured by a camera. It is also possible to obtain more accurate absolute position or relative position information by integrating / complementing the target information and the like.

And when actually applying sensor fusion, it is patented that each sensor is connected via a communication network such as an in-vehicle LAN, and time information is used to synchronize information obtained from each sensor. It is disclosed in Document 1. Patent Document 2 discloses that the time information is acquired from a GPS signal.
JP 2003-168197 A JP 2002-99906 A

However, when using time information (time stamp) acquired from a GPS signal as disclosed in Patent Document 2, a transmission delay is caused by a communication distance between transmission and reception, a processing time in a transmission (time source) side node, and the like. Will occur. Accordingly, there is a problem in that the side that receives the transmitted time information must receive a time that is later than the actual reception time, and cannot grasp an accurate time.
For example, if a delay time of 100 ms occurs when using sensor fusion to obtain accurate position information, an error of about 3 m occurs when the vehicle is traveling at a speed of 100 km / h.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to eliminate a delay error included in time information as much as possible when a plurality of sensors are connected via a communication network and time information is used. The object is to provide a vehicle network system and a network node used in the system.

According to the vehicle network system of claim 1, the node that is arranged in the middle of the communication network and relays information transmitted from each sensor is time information T (n) transmitted by any of the plurality of sensors. Is received, the delay time Δt is obtained from the difference between the time information T (n) and the reference time Ts (n) acquired by the reference time information acquisition means provided in the device. When the time information T (n) is received and the delay time Δtc corrected according to the communication status on the communication network is obtained, the transmission destination of the time information T is
T (n + 1) = T (n) + Δtc
Send.

That is, the delay time Δt obtained by (T (n) −Ts (n)) is the transmission delay td1 based on the distance between transmission and reception on the communication network (in this case, the distance between the destination and the node) and the time information T And transmission delay td2 based on the communication status at the time of receiving (n). The former transmission delay td1 is a fixed time, while the latter transmission delay td2 varies depending on the processing load of the transmission source, the communication load on the network, and the like.
Therefore, if the transmission delay td2 is estimated and subtracted from the delay time Δt, the corrected delay time Δtc becomes a constant value corresponding to the transmission / reception distance including only the transmission delay td1. Therefore, if the time information T (n + 1) obtained by adding the corrected delay time Δtc to the time information T (n) transmitted by the transmission source is transmitted, more accurate time information can be provided to the transmission destination. Thus, the accuracy of the synchronization processing performed using the time information can be improved.

  According to the vehicle network system of the second aspect, when the node receives the sensor information transmitted from any of the plurality of sensors, the node corrects the delay time Δt according to the content of the sensor information. For example, when the time information T (n) and the sensor information are transmitted from the same transmission source, the transmission delay time differs depending on the processing load required for the transmission source sensor to transmit the sensor information. . Further, even when the time information T (n) and the sensor information are transmitted from different transmission sources, the communication load on the network varies depending on the content (for example, data size) of the transmitted sensor information. Therefore, the transmission delay time is different. Therefore, if the delay time Δt is corrected according to the content of the sensor information, the delay time Δtc can be obtained appropriately.

  According to the vehicle network system of the third aspect, the node selects and uses any one of a plurality of reference time information acquisition means for acquiring time information using a radio wave signal. That is, in the case where the time information is acquired using the radio signal, it is assumed that the radio signal cannot be received depending on the position of the vehicle. Therefore, if a plurality of reference time information acquisition means are prepared and any one of them is selected according to the reception status of the radio signal, the reference time can be continuously acquired.

  According to the vehicle network system of claim 4, the node acquires in advance an error between the reference times obtained from each of the plurality of reference time information acquisition means, and between the selection targets before and after switching the acquisition target of the reference time The reference time is adjusted to reflect the time error at. That is, when a plurality of reference time information acquisition means are switched and used, if there is an error between the reference times acquired from each, the error is reflected as it is when the acquisition target is switched. Therefore, if the reference time is adjusted to reflect the time error that occurs between the selection targets before and after the switching, the first selected reference time can be used continuously.

  An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a diagram showing a configuration of the vehicle network system. In each part of the vehicle 1, for example, an outside air temperature sensor 2, a radar (sensor) 3, an engine speed sensor 4, a vehicle speed sensor 5, a throttle sensor 6, and the like are arranged. Each is connected to an in-vehicle LAN (communication network) 8 which is an in-vehicle network via a sensor ECU (Electronic Control Unit). In addition, a node (network node) 9 that relays data transmitted on the network is disposed in the middle of the in-vehicle LAN 8.

  A body ECU 10 is connected in the vicinity of the node 9 in the in-vehicle LAN 8, and sensor information transmitted from the sensors 3 to 6 is transmitted to the body ECU 10 via the node 9. That is, the node 9 and the body ECU 10 are connected to each other with a distance that allows a transmission delay time between them to be ignored. The body ECU 10 integrates the sensor information and performs sensor fusion in the same manner as in Patent Documents 1 and 2, for example, so as to obtain a relative distance from the host vehicle to the vehicle positioned ahead with high accuracy. Yes.

  FIG. 1 is a functional block diagram showing the configuration of the node 9 with respect to the part according to the gist of the present invention. The node 9 is composed of, for example, a microcomputer. The basic function of the node 9 is that when data transmitted to the in-vehicle LAN 8 by any sensor is received by the data receiving unit 11, the data is sent to the destination. It is transmitted from the transmission unit 12. Since the node 9 in this embodiment also has a function as a time correction observer, a delay time Δt correction logic unit (hereinafter simply referred to as a correction logic unit) 13 is provided between the data reception unit 11 and the data transmission unit 12. Has been inserted.

The node 9 includes a GPS receiver (reference time information acquisition means) 14 and a radio clock (reference time information acquisition means) 15. The GPS receiver 14 shares, for example, a car navigation device (not shown) arranged for detecting the current position of the vehicle. The radio clock 15 receives time information in Japan standard time, which is measured by an atomic clock, as a radio signal transmitted from a transmitting station, and an internal microcomputer performs time display based on the time information. .
Then, the node 9 selects one of the time information included in the GPS signal received by the GPS receiver 14 and the time information obtained from the radio clock 15 via the time source switching unit 16, and the time The data is output to the stamp adding unit 17. The time stamp assigning unit 17 outputs the time information given from the time source switching unit 16 to the correction logic unit 13 as reference time information Ts (n).

  The correction logic unit 13 receives the time stamp data T (n) output from the transmission sources of the sensors 3 to 6 or the reference data (detection data by the sensor or the like) RD from the upstream side of the in-vehicle LAN 8 via the data reception unit 11. Then, the transmission delay time Δtc is obtained based on them. Then, the time stamp data T (n + 1) considering the transmission delay time Δtc is transmitted to the transmission destination via the data transmission unit 12 and the downstream side of the in-vehicle LAN 8.

Next, the operation of the present embodiment will be described with reference to FIG. FIG. 2 is a flowchart showing processing performed when the node 9 receives data. First, when the data receiving unit 11 receives data, the correction logic unit 13 determines whether the received data is time stamp data T (n) or reference data RD as sensor information. (Steps S1, S9). If it is not any data (step S9: “NO”), the data is discarded (step S11), and a data reception wait state is entered.
When the received data is the reference data RD (step S9: “YES”), the correction logic unit 13 refers to the content of the reference data RD and estimates the communication load according to the content. Accordingly, the correction data value td is determined (step S10). And it will be in a data reception waiting state.

Here, the correction data value td according to the contents of the reference data RD is determined as follows. For example, when the time information T (n) and the reference data RD are transmitted from the same transmission source, if the processing load required for the transmission source sensor or the like to transmit the reference data RD is heavy, the transmission delay Time gets bigger. Then, the weight of the processing load is estimated according to the type of the reference data RD. Even if both are transmitted from different transmission sources, if the size of the transmitted reference data RD is large, the communication load on the in-vehicle LAN 8 becomes heavy. For example, the engine speed is high, the throttle opening (accelerator depression angle) is large, or the vehicle speed is high.
Therefore, if other data (here, the time stamp data T (n)) is being transmitted in parallel with the reference data RD as described above, the transmission time of the other data is affected and transmitted. The delay becomes larger. In step S10, the correction data value td is determined according to the content of the reference data RD, that is, the communication load.

  On the other hand, when the received data is time stamp data T (n) (step S1: “YES”), the time source switching unit 16 determines whether or not the GPS receiver 14 can receive a GPS signal at that time. If it is receivable (“YES”), the time information included in the GPS signal is acquired and set as the reference time Ts (n) (step S3). On the other hand, if the GPS signal cannot be received (“NO”), the time information is acquired from the radio clock 15 and set as the reference time Ts (n) (step S4).

The time source switching unit 16 measures in advance a synchronization error between the reference time acquired from the GPS signal and the reference time acquired from the radio clock 15, and the time source is transmitted from the GPS receiver 14 to the radio clock. When switched to 15, the reference time acquired from the radio timepiece 15 is corrected according to the synchronization error (step S5). By processing in this way, the time error caused by switching the time source is canceled.
In subsequent step S6, the correction logic unit 13 obtains the transmission delay time Δt on the in-vehicle LAN 8 for the received time stamp data T (n) by the equation (1).
Δt = T (n) −Ts (n) (1)
That is, with respect to the reference time Ts (n) obtained from the time stamp assigning unit 17, the time stamp data T (n) obtained and issued from the transmission source has a transmission delay time Δt until reaching the node 9. Because it contains.

Then, the correction logic unit 13 corrects the transmission delay time Δt by the equation (2) using the correction data td determined in step S10 to obtain the delay time Δtc (step S6).
Δtc = Δt−td (2)
That is, the delay time Δt obtained by the equation (1) is received from the transmission delay td1 based on the distance between transmission and reception on the in-vehicle LAN 8 (in this case, the distance between the transmission destination and the node 9) and the time information T (n). And transmission delay td2 based on the communication status at the time. The former transmission delay td1 is a fixed time, while the latter transmission delay td2 varies depending on the processing load of the transmission source, the communication load on the network, and the like.
Therefore, in step S10, the transmission delay td2 is estimated as the correction data td. If the correction data td is subtracted from the delay time Δt in step S7, the corrected delay time Δtc becomes a constant value corresponding to the transmission / reception distance including only the transmission delay td1.

  Therefore, in the subsequent step S8, time information T (n + 1) is generated by adding the corrected delay time Δtc to the time stamp data T (n) transmitted from the transmission source. Then, the time information T (n + 1) becomes a value obtained by adding the delay time Δtc based on the physical communication distance on the in-vehicle LAN 8 to the time T (n) at which the transmission is performed by the transmission source. Will be expressed. The generated time information T (n + 1) is transmitted to the transmission destination, that is, the body ECU 10, and the body ECU 10 performs relative distance detection using the sensor fusion technique using the time information T (n + 1). It is.

  As described above, according to the present embodiment, the node 9 that is arranged in the middle of the in-vehicle LAN 8 and relays information transmitted from the sensors 3 to 6, etc., transmits the time stamp data T ( n), the delay time Δt is obtained from the difference between the time stamp data T (n) and the reference time Ts (n) acquired from the GPS receiver 14 or the radio timepiece 15 included in the time stamp data T (n). When the delay time Δtc corrected according to the communication status on the in-vehicle LAN 8 is obtained when n) is received, time information T (n + 1) (= T (n) + Δtc) is generated and transmitted to the body ECU 10. I made it. Accordingly, it is possible to provide more accurate time information to the transmission destination, and it is possible to improve the accuracy of the synchronization processing for the sensor fusion technique performed using the time information.

When the node 9 receives the reference data RD transmitted by any one of the sensors 3 to 6, the node 9 corrects the delay time Δt according to the content of the reference data RD, and accordingly obtains the delay time Δtc appropriately. Can do. In addition, since the node 9 selects and uses the reference time Ts (n) acquired from either the GPS receiver 14 or the radio clock 15, either radio signal is received depending on the position of the vehicle 1. Even when it becomes impossible, the reference time Ts (n) can be continuously acquired.
Further, the node 9 measures the synchronization error between the reference time acquired from the GPS signal and the reference time acquired from the radio clock 15 in advance, and switches the time source from the GPS receiver 14 to the radio clock 15. In this case, since the reference time acquired from the radio clock 15 is corrected according to the synchronization error, it is possible to cancel the time error caused by switching the time source and continuously use the first selected reference time. it can.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications are possible.
Needless to say, each sensor or the like disposed in the vehicle may be selected according to the use of the individual vehicle, and sensors other than those shown in FIG. 3 may be used.
The target from which the reference time is first acquired may be the radio clock 15.
The GPS receiver 14 does not necessarily need to share what is used for the car navigation device, and may be used only for the vehicle network system of the present invention.
Three or more reference time information acquisition means may be prepared to select a time source or only one. When a plurality of time sources are switched and used, the time correction processing based on the synchronization error between them may be performed as necessary.
Further, the reference time information acquisition unit is not limited to the time measuring operation based on the radio signal transmitted from the outside, such as the GPS receiver 14 and the radio clock 15.
The subject that performs sensor fusion is not limited to the body ECU 10, and may be performed by a sensor ECU associated with any one of the sensors.

The functional block diagram which is one Example of this invention and shows the structure of a node about the part which concerns on the summary of this invention Flow chart showing processing to be performed when a node receives data The figure which shows the structure of the network system for vehicles

Explanation of symbols

In the drawings, 1 is a vehicle, 2 is an outside air temperature sensor, 3 is a radar (sensor), 4 is an engine speed sensor, 5 is a vehicle speed sensor, 6 is a throttle sensor, 8 is an in-vehicle LAN (communication network), and 9 is a node ( (Network node), 10 is a body ECU, 13 is a delay time Δt correction logic unit, 14 is a GPS receiver (reference time information acquisition means), and 15 is a radio clock (reference time information acquisition means).

Claims (5)

A plurality of sensors that are arranged in each part of the vehicle and detect information necessary when the vehicle travels, and a communication network that is connected to at least a part of these sensors and transmits information detected by the sensors And a network system for vehicles comprising a node arranged in the middle of this communication network and receiving data transmitted by any sensor and transmitting it to a transmission destination.
Any one or more of the plurality of sensors is configured to be able to output time information detected by itself on the communication network,
The node includes a reference time information acquisition unit,
When the time information T (n) transmitted by any of the plurality of sensors is received, the difference between the time information T (n) and the reference time Ts (n) acquired by the reference time information acquisition means Obtain the delay time Δt,
When the time information T (n) is received, the delay time Δt is corrected to Δtc according to the communication status on the communication network (where n is a natural number indicating the time series of the time information T).
In the transmission destination of the time information T, as time information T (n + 1),
T (n + 1) = T (n) + Δtc
A vehicle network system characterized by transmitting   2. The vehicle network system according to claim 1, wherein when the node receives sensor information transmitted from any of the plurality of sensors, the node corrects the delay time Δt according to the content of the sensor information. . The node includes a plurality of reference time information acquisition means configured to acquire reference time information using a radio wave signal transmitted from the outside,
The vehicle network system according to claim 1 or 2, wherein any one of the plurality of reference time information acquisition means is selected and used.   The node acquires in advance an error between reference times obtained by each of the plurality of reference time information acquisition means, and when switching the target for acquiring the reference time, the node calculates the time error between the selection targets before and after the switching. 4. The vehicle network system according to claim 3, wherein the reference time is adjusted by reflecting the reference time. A network node used for the vehicle network system according to claim 1.

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