Data sensor coordination using time synchronization in a multi-bus controller area network system

• US 8,504,864 B2
• Filed: 12/01/2010
• Issued: 08/06/2013
• Est. Priority Date: 12/01/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Menon, Sandeep, Basnayake, Chaminda
• Primary Examiner(s): DU, THUAN N
• Application Number:
  US12/957,638
• Publication Number:
  US 20120140861A1
• Time in Patent Office: 979 Days
• Field of Search: 713/400, 713/401, 713/501, 713/600, 370/350, 370/503, 370/445, 370/519, 375/356, 375/362
• US Class Current: 713/401
• CPC Class Codes: B60T 7/18 operated by wayside apparatus
• CPC Class Codes: H04J 3/0644 External master-clock
• CPC Class Codes: H04J 3/0664 unidirectional timestamps
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling
• CPC Class Codes: H04L 2012/40215 Controller Area Network CAN
• CPC Class Codes: H04L 2012/40273 the transportation system being a vehicle

Abstract

A method is provided for synchronizing time in an unsynchronized vehicle controller area network system. A master control unit receives a global time from a time synchronization source. The master control unit estimates a respective time delay in transmitting messages by electronic control units on each controller area network bus. The time delay is a difference between a time when a message is generated by a respective electronic control unit for transmission on a respective controller area network bus and a time when the message is transmitted on the respective controller area network bus. The global time is adjusted for each respective controller area network bus based on the estimated time delays associated with each respective controller area network bus. Global time messages from the master control unit are transmitted to each electronic control unit that include the adjusted global times for an associated controller area network bus.

Claims

1. A method for synchronizing time in an unsynchronized vehicle controller area network system, the system having a plurality of electronic control units in communication within one another via a plurality of controller area network buses, the electronic control units are in communication with sensing devices for collecting sensed data obtained by the sensing devices, each electronic control unit transmitting messages on the plurality of controller area network buses for sharing sensed data with other electronic control units, and the plurality of electronic control units are in communication with a master control unit vehicle via the plurality of controller area network buses, the method comprising the steps of:

the master control unit receiving a global time from a time synchronization source;

the master control unit estimating a respective time delay in transmitting messages by the electronic control units in each controller area network bus, the time delay being a difference between a time when a message is generated by a respective electronic control unit for transmission on a respective controller area network bus and a time when the message is transmitted on the respective controller area network bus;

adjusting the global time for each respective controller area network bus based on the estimated time delays associated with each respective controller area network bus; and

transmitting global time messages from the master control unit to each electronic control unit that include the adjusted global times for an associated controller area network bus, wherein each electronic control unit connected to the controller area network receiving a respective global time message synchronizes a local clock based on the adjusted global time in the respective global time message.

2. The method of claim 1 wherein the vehicle controller area network system includes gateways for providing system interoperability between adjoining controller area network buses, wherein the gateway delays are added to the time delays and transmitted to respective electronic control units succeeding the gateway.

3. The method of claim 1 wherein sensed data obtained by a sensing device is collected by a respective electronic control unit, wherein the sensed data is time-stamped by the respective electronic control unit using the synchronized local clock prior to being transmitted on the respective controller area network bus.

4. The method of claim 3 wherein the sensed data transmitted by electronic control units of different controller area network buses is integrated based on the synchronized time-stamp of the sensed data.

5. The method of claim 4 wherein a global time is transmitted to a plurality of vehicles, wherein a respective master control unit of each vehicle determines time delays on each respective controller area network bus, wherein the global time is adjusted based on the time delay of each controller area network in each vehicle, wherein the adjusted global times determined by each master control unit of each vehicle are transmitted over each respective controller area network bus for synchronizing local clocks of the electronic control units of the plurality of vehicles.

6. The method of claim 5 wherein sensed data from the plurality of vehicles is wirelessly transmitted between the plurality of vehicles, wherein the sensed data from the plurality of vehicles is integrated based on the time-stamp of the sensed data.

7. The method of claim 1 wherein the global time is obtained from a GPS time source.

8. The method of claim 1 wherein the global time is obtained from a cell phone signal.

9. The method of claim 1 wherein the global time is obtained from an atomic clock.

10. The method of claim 1 wherein the global time is obtained from an internet.

11. The method of claim 1 wherein the global time is obtained from a designated vehicle within a group of vehicles in a vehicle-to-vehicle communication system.

12. The method of claim 1 wherein the global time is obtained from a road side equipment of a vehicle-to-infrastructure communication system.

13. A vehicle communication system comprising:

a plurality of sensing devices for obtaining vehicle-related data;

a plurality of electronic control units for receiving vehicle-related data from the plurality of sensing devices;

a plurality of controller area network buses coupled to the plurality of electronic control units for transmitting the vehicle-related data;

a master control unit in communication with each of the plurality of controller area network buses, the master control unit estimating a respective time delay for messages transmitted on each controller area network bus, the time delay being a difference between a time when messages are generated for transmitting and a time when messages are expected to be transmitted on an associated controller area network bus;

a time synchronization source for generating a global time;

wherein the global time is adjusted by the master control unit for each respective controller area network bus based on the respective time delay determined in each controller area network bus, wherein the master control unit transmits a respective message on each controller area network bus that includes the respective adjusted global time for each controller area network bus, and wherein each electronic control unit receiving the respective message synchronizes a local clock to the adjusted global time received in the respective message.

14. The system of claim 13 wherein the time delay determined by the master control unit for an associated controller area network bus is based on an average delay that is a function of a predetermined number of messages generated and transmitted on the associated controller area network bus.

15. The system of claim 13 wherein the time synchronization source is an in-vehicle time synchronization source.

16. The system of claim 13 wherein the time synchronization source is an external time synchronization source.

17. The system of claim 16 wherein external time synchronization source is provided through a vehicle-to-vehicle communication network.

18. The system of claim 16 wherein external time synchronization source is provided through vehicle-to-infrastructure communication network.

19. The system of claim 16 wherein external time synchronization source is a cellular phone communication service.

20. The system of claim 16 further comprising a gateway coupled to the controller area network buses, wherein the gateway provides system interoperability between two adjoining controller area network buses, wherein the gateway communicates to the master control unit time delay data relating to time delays of messages being processed through the gateway, wherein the master control unit adds the time delay of the gateway to the adjusted global time, and wherein the adjusted global time that includes the time delay of the gateway is transmitted on to electronic control units succeeding the gateway for local clock synchronization.