基于CAN总线的分布式高精度时钟的实现

Implementing a Distributed High-Resolution Real-time Clock by the CAN-bus

在许多对时间要求很严格的应用中都需要一个精确的实时时钟,如分布式控制中的测试设备就需要一个精确到毫秒级的实时时钟。集中式控制系统达到毫秒级非常容易,但是在分布式控制系统(例如连接在CAN-bus上的传感器和执行机构),由于他们没有全局的时钟节拍,使系统达到毫秒级的同步就很困难。这个问题可以通过在一定的精度内同步所有的节点时钟来解决。该文提出了一种应用在总线上的时钟同步协议,并且以CAN-bus为例在实验室中得以实现。经验证该协议能够提供一个大约10毫秒的同步精度。该协议简单且不需要额外的硬件,它只是占有一定的带宽(<20个信息/每秒)。如必要也可在大型网络中达到与外部时钟基准同步的要求。

Much time critical applications,e.g.the measurement devices in distributed control system,require a real-time clock with an accuracy of microseconds.In a centralized system it is easy to implement the requirement,but in a distributed system (like a number of sensor and actuator nodes connected via the CAN-bus),this is more difficult as there is no global system tick.Synchronizing the local clocks of all nodes with a sufficient accuracy can solve this problem.This paper offers a clock synchronization protocol on the CAN-network and implements it in the lab.The results show this protocol can reach the accuracy of 10 microseconds.The protocol is simple and hardware-independent;it uses only a small amount of bandwidth(<20 messages/second).If necessary,e.g.in large scale networks,the protocol can be synchronized with an external time-base.