[EtherCAT Feature Packs]
EtherCAT 電纜冗餘是指 EtherCAT 通訊系統即使在電纜故障的情況下也能保持連續可靠的通訊的能力。電纜冗餘採用環形拓撲，可在兩個方向上運行。如果一條電纜發生故障或斷開連接，另一條電纜路徑仍可運作以確保通訊不間斷。電纜冗餘增強了 EtherCAT 網路的容錯能力，最大限度地減少停機時間並提高整體系統可靠性。
電纜冗餘中電纜是否斷線分為以下三種情況。以下您將了解如何實現電纜冗餘，以及這些場景之間 EtherCAT 主控制器的差異。
- 無電纜破損
- 兩個從站之間的電纜斷開
- 主從之間的電纜斷開
為了便於解釋，這裡做一些假設：
- 假設週期時間設定為 125 µs。
- 假設所有從站只有輸入 PDO（沒有輸出PDO），則過程資料幀中的工作計數器（WKC）在經過每個從站時都會加1。
- 假設 EtherCAT 網路上只有 6 個從站，預期工作計數器 (EWKC) 為 6。
- Primary Port and Secondary Port send process data frames in every cycle at the same time.
無電纜破損
Without Cable Broken:
- Primary frame from primary port will be received by secondary port, which frame with WKC = 6.
- Secondary frame from secondary port will be received by primary port, which frame with WKC = 0.
- Master will discard the secondary frame because primary frame’s WKC equals to EWKC and secondary frame’s WKC equals to 0, it means that without cable broken.
兩個從站之間的電纜斷開
Unplug the cable between Slave 3 and Slave 4:
- If you unplug the cable manually, it might with some interference which last several cycles. (N = 0 ~ more)
- If the interference continues for a period of time, some slaves will enter the SAFEOP state due to SyncManager Watchdog.
Cable broken between Slave 3 and Slave 4:
- Primary frame from primary port will be received by primary port, which frame with WKC = 3.
- Secondary frame from secondary port will be received by secondary port, which frame with WKC = 3.
- Primary frame and secondary frame will be combined by Master, because primary frame’s WKC is less than EWKC and secondary frame’s WKC is greater than 0, it means that the cable broken event is happened between two slaves.
主從之間的電纜斷開
Unplug the cable between Master and Slave 1:
- If you unplug the cable manually, it might with some interference which last several cycles. (N = 0 ~ more)
- If the interference continues for a period of time, some slaves will enter the SAFEOP state due to SyncManager Watchdog.
Cable broken between Master and Slave 1:
- Primary frame from primary port will lost.
- Secondary frame from secondary port will be received by secondary port, which frame with WKC = 6.
- Master will ignore the primary frame because primary frame was lost and secondary frame’s WKC equals to EWKC, it means that the cable broken event is happened between Master and Slave 1.
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For more details, please refer to the EtherCAT API 使用手冊.
