對于當(dāng)今的大多數(shù)應(yīng)用,標(biāo)準(zhǔn) EtherCAT 的高性能已經(jīng)足夠了。因此,EtherCAT G 通信的開發(fā)考慮到了超大規(guī)模應(yīng)用和許多設(shè)備,以及越來越多地使用特別數(shù)據(jù)密集型設(shè)備,例如視覺相機(jī)、復(fù)雜運(yùn)動(dòng)系統(tǒng)或具有高采樣率的測量應(yīng)用。機(jī)器視覺、狀態(tài)監(jiān)測或創(chuàng)新的傳輸系統(tǒng) XTS 和 XPlanar 需要為每個(gè)設(shè)備在每個(gè)周期傳輸數(shù)百字節(jié)的過程數(shù)據(jù)。結(jié)合不到一毫秒的短周期時(shí)間,在這種情況下需要 EtherCAT G 提供的高傳輸帶寬。
個(gè)實(shí)用的 EtherCAT G 應(yīng)用程序是 XPlanar 傳輸系統(tǒng)。這種平面電機(jī)系統(tǒng)能夠?qū)哂辛鶄€(gè)自由度的被動(dòng)自由浮動(dòng)動(dòng)子進(jìn)行運(yùn)動(dòng)控制和高精度定位。由于獨(dú)特的新系統(tǒng)需要連續(xù)的位置反饋,因此產(chǎn)生了非常大的數(shù)據(jù)量,必須在幾微秒內(nèi)傳輸。如果沒有 EtherCAT G 的高性能,這幾乎是不可能的。
這兩個(gè)示例計(jì)算說明了使用 EtherCAT G 和分支概念可以實(shí)現(xiàn)的性能提升或數(shù)據(jù)傳輸時(shí)間的節(jié)省。
加快通信時(shí)間:34 µs 內(nèi) 128 個(gè)伺服軸
- 初始應(yīng)用選擇了具有 128 個(gè)伺服軸的機(jī)器網(wǎng)絡(luò)。
- 每個(gè)設(shè)備輸入和輸出 8 個(gè)字節(jié)的“標(biāo)準(zhǔn)數(shù)據(jù)寬度”導(dǎo)致每個(gè)周期總共輸入和輸出 1024 個(gè)字節(jié)。對于經(jīng)典的 EtherCAT 設(shè)備,考慮到硬件傳播延遲時(shí)間和報(bào)文長度,將產(chǎn)生 237 µs 的通信時(shí)間。
如果現(xiàn)在標(biāo)準(zhǔn)的 EtherCAT 設(shè)備被 EtherCAT G 設(shè)備取代,通信時(shí)間可以減少到 150 µs,因?yàn)楦叩臄?shù)據(jù)速率會(huì)縮短幀長度。如果使用分支概念并將整個(gè)網(wǎng)絡(luò)分成 8 個(gè) EtherCAT G 段,每個(gè)段有 16 個(gè)伺服驅(qū)動(dòng)器,則可以實(shí)現(xiàn)僅 34 µs 的通信時(shí)間——即現(xiàn)在的通信速度提高了 7 倍。
利用帶寬優(yōu)勢:以 100 ksamples/s 掃描 200 個(gè)模擬輸入
- 測量狀態(tài)監(jiān)測應(yīng)用程序,其中監(jiān)測 10 公里長的傳送帶。
- 應(yīng)用由 200 個(gè)模擬通道 (±10 V) 組成,每個(gè)通道具有 100,000 個(gè)樣本/秒(10 µs 測量間隔),必須以 1 ms 的周期時(shí)間進(jìn)行掃描。
目前的解決方案由四個(gè)獨(dú)立的 100 Mbit/s EtherCAT 網(wǎng)絡(luò)組成,每個(gè)網(wǎng)絡(luò)具有 26 個(gè)具有過采樣功能的兩通道模擬輸入端子 (EL3702)。每個(gè) EtherCAT 網(wǎng)絡(luò)都需要 8 個(gè) 1313 字節(jié)的報(bào)文,因此需要 322 Mbit/s 的帶寬。因此,四個(gè)網(wǎng)絡(luò)中的每一個(gè)都使用了 88% 的可用帶寬。
如果四個(gè) EtherCAT 網(wǎng)絡(luò)現(xiàn)在被一個(gè) EtherCAT G 網(wǎng)絡(luò)和 EK1100 總線耦合器替換為 EK1400 EtherCAT G 總線耦合器(分支控制器),則可以繼續(xù)使用現(xiàn)有的標(biāo)準(zhǔn) EtherCAT 端子模塊。在相同的周期時(shí)間 (1 ms) 下,帶寬利用率僅為 350 Mbit/s,因此只需一個(gè) EtherCAT G 網(wǎng)絡(luò)。剩余的 650 Mbit/s 帶寬可擴(kuò)展通道并支持更高的模擬采樣率。
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These two sample calculations illustrate the boost in performance or the savings in data transmission time that can be achieved with EtherCAT G and the branch concept.
Accelerating communication times: 128 servo axes in 34 µs
- A machine network with 128 servo axes was selected as the initial application.
- A “standard data width” of 8 bytes in and out per device results in a total of 1024 bytes in and out per cycle. With classic EtherCAT devices, taking into account hardware propagation delay times and telegram lengths, a communication time of 237 µs will result.
If standard EtherCAT devices are now replaced by EtherCAT G devices, the communication time can be reduced to 150 µs just on account of the shortened frame length due to the higher data rate. If the branch concept is used and the complete network is divided into eight EtherCAT G segments with 16 servo drives each, a communication time of only 34 µs can be achieved – i.e. communication is now 7 times faster.
Using the bandwidth advantage: scanning 200 analog inputs with 100 ksamples/s
- An measurement Condition Monitoring application where a 10 km-long conveyor belt is monitored.
- Application consists of 200 analog channels (±10 V) with 100,000 samples/s (10 µs measurement interval) per channel, which have to be scanned with a cycle time of 1 ms.
The present-day solution consists of four independent 100 Mbit/s EtherCAT networks, each with 26 two-channel analog input terminals with oversampling function (EL3702). Eight telegrams with 1313 bytes each are required in every EtherCAT network, resulting in a required bandwidth of 322 Mbit/s. Thus, each of the four networks utilises 88% of the available bandwidth.
If the four EtherCAT networks are now replaced by an EtherCAT G network and the EK1100 Bus Couplers by EK1400 EtherCAT G Bus Couplers (branch controllers), it is possible to continue to use existing standard EtherCAT Terminals. With the same cycle time (1 ms), bandwidth utilisation of only 350 Mbit/s results in just one EtherCAT G network. The remaining bandwidth of 650 Mbit/s enables an extension of the channels and the support of even higher analog sampling rates.