Abstract
Time-synchronization technology can provide a common notion of time among the participating nodes on a network. This is essential not only for protocol operation for time-critical services but also for the time stamp for information included in the message. Precise time information can be very crucial for such things as autonomous driving because there are various sensor measurements from multiple cameras, and radio detection and ranging (radar) and light detection and ranging (LiDAR) are used for perceiving the current situation via sensor fusion. A well-known synchronization method, IEEE 1588, denoted as the precision time protocol (PTP), can be used for various applications. For in-vehicle networks of autonomous cars, we have to consider that the network may be comprised of subnetworks based on different protocols such as controller area network (CAN) and Ethernet. However, implementing PTPs on such heterogeneous vehicle networks causes several problems. First, the PTP procedure must be modified to be implement on a CAN network. Second, to calculate the delay and offset for PTP, the processing delay that occurs during message conversion must be considered. In this paper, we propose a synchronization method for CAN–Ethernet networks to solve these problems. The performance of the proposed synchronization method is evaluated by experiments on a real CAN–Ethernet network.
Highlights
As autonomous driving technology has rapidly developed and become closer to commercialization, ensuring that stability and reliability of vehicle control and communication technologies are getting more important [1,2]
Lee presented a method for improving the quality of service (QoS) of the network in a vehicle that applies the time trigger technique of FlexRay and Ethernet [19]; in the study, external clocks of the Ethernet nodes and gateway were first synchronized through the precision time protocol (PTP)
Figure shows the experimental setup for the performance evaluation of the controller area network (CAN)–Ethernet network synchronization
Summary
As autonomous driving technology has rapidly developed and become closer to commercialization, ensuring that stability and reliability of vehicle control and communication technologies are getting more important [1,2]. To improve autonomous vehicle performance, increasing research is being conducted concerning time synchronization among the sensors and controllers connected via communication networks. While the time-synchronization method for a single-protocol network, either CAN or Ethernet network is established, heterogeneous communication environments, such as a CAN–Ethernet network, require additional work to achieve time synchronization. Lee presented a method for improving the quality of service (QoS) of the network in a vehicle that applies the time trigger technique of FlexRay and Ethernet [19]; in the study, external clocks of the Ethernet nodes and gateway were first synchronized through the PTP. A method for applying the PTP mechanism to CAN communication to achieve precise time synchronization and a method for correcting the processing delay_required by the gateway is proposed.
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