
在 ETHERNET Powerlink 中,第 3 層和第 4 層中的 TCP(和 UDP)IP 堆棧由 Powerlink 協(xié)議擴展。另一個中間件基于 TCP(和 UDP)IP 以及 Powerlink 堆棧(異步數(shù)據(jù)傳輸)。此外,還有一個用于快速循環(huán)數(shù)據(jù)傳輸(同步數(shù)據(jù)傳輸)的堆棧。Powerlink 堆棧完全控制網(wǎng)絡上的數(shù)據(jù)流量。該方法稱為時隙通信網(wǎng)絡管理 (SCNM),以提供以太網(wǎng)的實時能力。每個站都具有定時和嚴格限制的通信權(quán)限,并且可以向網(wǎng)絡內(nèi)的其他站發(fā)送數(shù)據(jù)。在特定時間,只有一個站點可以訪問總線,因此不可能發(fā)生沖突,從而實現(xiàn)嚴格的確定性性能。除了用于同步數(shù)據(jù)傳輸?shù)倪@些單獨的時隙之外,
擴展版本(版本 2)包含基于 CANopen(與 CAN in Automation (CiA) 組合作)的通信和設備配置文件。ETHERNET Powerlink 第 3 版包括基于 IEEE 1588 的時間同步機制。

德國公司 Jetter 提供了一種通過以太網(wǎng) TCP/IP 進行同步的方法,它稱之為 JetSync。它使用類似于 IEEE 1588 的進程,但也支持異步通信。該公司聲稱,其系統(tǒng)比使用嚴格的同步時隙方法實現(xiàn)的結(jié)構(gòu)更加開放和靈活。
JetSync 支持運動控制應用以及通過 TCP/IP 傳輸普通異步數(shù)據(jù)。該公司表示,這實現(xiàn)了使用標準組件在 PLC、驅(qū)動器、遠程 I/O 模塊和 SCADA 組件之間進行通信的兼容性。Jetter 聲稱,僅使用在標準以太網(wǎng)基礎設施上運行的 TCP/IP 就可以將運動軸同步到優(yōu)于 10 的軸抖動。
Modbus/TCP – IDA
近合并的 Modbus-IDA 集團正致力于進一步開發(fā)用于使用 Modbus/TCP 作為消息結(jié)構(gòu)的分布式控制系統(tǒng)的 IDA 架構(gòu)。
Modbus/TCP 是 Modbus 協(xié)議的衍生,開放規(guī)范基于以太網(wǎng)和標準 TCP/IP,直接安裝在第 4 層。它為主從通信定義了一種結(jié)構(gòu)簡單、開放且廣泛使用的傳輸協(xié)議。
IDA 不僅僅是一個協(xié)議(如 Modbus),而是一個集成了分布式和智能自動化方法的綜合接口。IDA 方法包含控制系統(tǒng)、通信服務和設備/軟件接口的整個架構(gòu)。它提供水平和垂直集成,并廣泛使用 Web 服務。
IDA 架構(gòu)同時考慮了實時和非實時通信。確定性方面將通過直接安裝在 TCP/UDP 堆棧上的 IDA 中間件來實現(xiàn)。中間件包含 Modbus/TCP 協(xié)議作為標準。非實時和基于 Web 的通信使用 TCP/IP 堆棧。用于設備和系統(tǒng)操作的診斷和數(shù)據(jù)編程、參數(shù)設置等將使用 IT 標準協(xié)議 HTTP、FTP 和 SNMP 交付。IDA 方法保證了無縫通信架構(gòu)(垂直和水平),而 Modbus/TCP 的結(jié)合為智能傳感器等各種設備開辟了市場。

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The German company Jetter offers a method of synchronisation via Ethernet TCP/IP which it calls JetSync. It uses processes similar to IEEE 1588 but also supports asynchronous communication. The company claims that its system leads to a more open and flexible structure than that achieved by using strict synchronisation time-slot methods.
JetSync supports motion control applications as well as transmission of ordinary asynchronous data through TCP/IP. This, says the company, achieves compatibility using standard components for communication between PLCs, drives, remote I/O modules and SCADA components. Jetter claims that synchronisation of motion axes to better than 10?s axis jitter can be achieved just using TCP/IP alone running on a standard Ethernet infrastructure.
Modbus/TCP – IDA
The recently merged Modbus-IDA Group is working towards further development of the IDA architecture for distributed control systems using Modbus/TCP for the message structure.
Modbus/TCP is a derivative of the Modbus protocol and the open specification, based on Ethernet and standard TCP/IP, mounts directly on Layer 4. It defines a simple structured, open and widely used transmission protocol for a master-slave communication.
IDA is not only a protocol (like Modbus), but a comprehensive interface that integrates methods for distributed and intelligent automation. The IDA approach takes in the entire architecture of the control system, communication services and device/software interface. It provides both horizontal and vertical integration and makes extensive use of Web Services.
IDA architecture takes account of both real-time as well as non realtime communication. The deterministic aspects will be realised through IDA middleware which is directly mounted on the TCP/UDP stack. The middleware contains the Modbus/TCP protocol as a standard. Non real-time and web-based communication uses the TCP/IP stack. Diagnostics and data programming, parameterisation, etc, for operation of devices and systems will be delivered using the IT standard protocols HTTP, FTP and SNMP. The IDA approach promises a seamless communication architecture (vertical and horizontal) while incorporation of Modbus/TCP opens up the market for a variety of devices such as intelligent sensors.