以Database發展之智慧型Gateway達成遠端CAN-Based輪椅車監控系統

Abstract

因CAN Bus在穩定性、即時性與價格的整體表現在眾多工業網路中佔有其優勢，故CAN-Based分散式的網路控制系統是目前的一個趨勢。為了達到遠端監控，因此我們將需要一個Gateway來橋接CAN與Ethernet兩種不同協定的網路，並能遠端監控CAN-Based分散式的網路控制系統。 遠端監控CAN-Based分散式的網路系統需考量當CAN Bus上有節點以高優先權的CAN訊息霸佔CAN Bus時，遠端監控者便無法送出訊息給其他CAN Bus上的節點。因此我們利用Database定期計算CAN網路流量，並將其紀錄在Database中，遠端使用者傳送的控制命令會先傳送到Database中，該控制命令訊息將依據CAN網路流量與CAN網路中是否有其他訊息的優先權高於控制命令，來判斷是否提高成優先權，再將其傳送到CAN Bus上到其他節點。 遠端監控CAN-Based分散式的網路系統將監控所有CAN Bus上所傳遞的訊息，並將其紀錄在Database中，以供查詢除錯使用。但CAN Bus的頻寬有限，所以我們必須規劃CAN Bus上的節點，以主動方式或被動方式來更新Database中的節點狀態。主動方式將主動地傳遞CAN訊息給Gateway以更新Database中的節點狀態。被動式是當遠端監控者下達CAN RTR(Remote Transmit Request)訊息到CAN Bus後，始由CAN Bus上節點之硬體自動接收，並自動回應遠端監控者要求的CAN訊息，以更新Database中節點的狀態，如此利用RTR可加快訊息的更新與減少CAN網路的使用與浪費。 在輪椅車控制器方面，設計一穩健控制器能改善開迴路控制的突衝現象，並追隨一目標函數，讓輪椅車使用者有更好的舒適度。最後達成可靠與有效率的CAN-Based遠端監控系統。

CAN possess the advantages of stability, real-time performance, and low price among various industrial field bus systems. As Internet becomes more popular in automation, the gateway to bridge the CAN and Ethernet in order to remotely monitor CAN-based network control system is thus required. Since high-priority message may occupy the CAN bus and the low-priority message may be thus blocked in transmission, the priority of message in the distributed system in remote monitoring system is critical. The developed smart gateway monitors the flow rate of the CAN bus and increase the priority of the low-priority message to guarantee the remote control. Moreover, the monitoring system uses the database to restore all CAN messages in the bus in order to serve the query status of CAN nodes or to control CAN nodes. Moreover, updating the new status of the nodes will be carried in the database only as the status changes, because the bandwidth of CAN is limited. When the supervisor inquires certain messages with the RTR format in CAN bus, CAN nodes then send messages to the database of the gateway to update its status information for serving the supervisor efficiently. In order to achieve a comfortable motion for the wheelchair users, a robust controller to improve its open-loop control performance is applied. The controller will be designed to track the target function with smooth responses. The developed smart gateway has been applied to the CAN-based wheelchair to obtain satisfactory results.