車輛OBDII與CAN BUS通訊系統的探討與應用

Study And Implementation Of Vehicle OBDII And CAN BUS Communication System

陳建燁(Jian-Ye Chen)

國立虎尾科技大學/工程學院/動力機械工程研究所/碩士(2005年)

摘要

本論文目的是探討車輛電子裝置間的通訊系統，分別為OBDII與CAN BUS，在定性差異比較與製作上需注意的問題，以及發展出相關的車輛應用裝置等，應用裝置的發展上，選擇CAN BUS通訊系統，開發出具CAN BUS功能之第三煞車燈與汽車電動座椅裝置。
比較OBDII的通訊協定SAE J1850、ISO 9141與CAN BUS規範，可以了解SAE J1850、ISO 9141系統，雖然在應用層的協定與故障碼的制定相同，但在實體層與資料連結層方面，卻都有其特有的制定方式，同樣的，CAN BUS也擁有其特有的實體層與資料連結層，由此可以了解三種系統彼此間並不相容；實際製作上，論文中是以SAE J1850 VPW與ISO 9141等兩種通訊協定為主，SAE J1850 VPW主要以Atmel 89C51微處理器來進行通訊模擬，而ISO 9141則利用Microsoft Visual C++，對車輛引擎電腦(ECU)直接進行通訊連線測試，由製作的過程中了解SAE J1850 VPW實際通訊時，脈波寬度的調變控制上需較規範中的發送標準值64 us或128 us為大，才能避免通訊時錯誤的產生；ISO 9141於初始化時需適當的切換傳輸速率，以及調配資料的傳輸時間，以避免因資料遺失而產生通訊失敗的狀態。
CAN BUS網路系統，主要作為論文中新開發出的第三煞車燈與電動汽車座椅裝置的通訊實現方法，使第三煞車燈裝置除了能提高行車安全性外，並具有即時性的資訊分享功能；汽車電動座椅則具有遠端控制與資訊分享功能，並提供系統識別(system identification)時，利用PCL 818H為控制卡時如何製作與修正馬達驅動器的方法。

並列摘要

This thesis is focused on qualitative study of characteristic differences between OBDII and CAN BUS communication network system on vehicles, and implementing the CAN BUS system into two electronically-controlled devices for vehicles― the auxiliary brake light and the electric car seat.

By comparing SAE J1850 and ISO 9141 protocols for OBDII with that for CAN BUS, we can perceive that the former two standards accept common protocols on application layer and share the same forms of diagnostic codes, but all have their own special standards and structures on physical and data link layers. Hence, these three communication network systems are basically incompatible. Communication systems based on J1850VPW and ISO 9141 are practically realized. An ATMEL 89C51 microprocessor is utilized for developing the SAE J1850 VPW system. As for ISO 9141, Microsoft Visual C++ is used to directly test the communication connection process between a PC and an engine ECU. It is found that the pulse width of J1850 VPW for modulation control needs to be greater than the standard transmitting values of 64 us or 128 us to avoid communication errors. We also found that during the initialization process of ISO 9141 the transmitting rate should be properly switched and the data transmitting time should be correctly modulated so as to prevent from causing communication failure.

CAN BUS communication network system is used to realize communication function for the newly-developed auxiliary brake system and the electric car seat. The advantages for the former application are improving driving safety and proving desirable function of real-time information exchange. The purposes for the latter application are fulfilling remote control and information exchange, and providing a communication method so that PCL 818H control board can be utilized to develop the power driver of motor and perform system identification.

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