Synchronize Your Watches: Part II: Special-Purpose Solutions for Distributed Real-Time Control

The ability to carry out coordered activities in distributed applications is currently considered a basic requirement in most industrial scenarios as well as in many areas with demanding real-time constraints, such as modern electric power systems, the automotive/avionic domains, and some types of networked embedded control systems. For this reason, the majority of the networks that were conceived recently for use in these environments provide some means to deal with distributed clock (DC) synchronization. EtherCAT is a high-performance Ethernet-based industrial network. Its main goal is to enable the adoption of Ethernet communications in automation applications that require short cycle times and low communication jitters. This protocol is an open standard based on master-slave architecture. An important feature of EtherCAT is the DC synchronization mechanism, which enables all devices to share the same system time. In this way, typical control operations, such as the generation of coordered output signals or the precise timestamping of input events, can be synchronized for all devices in the network.