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Fleet management standarr
Page 39
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Daf, Daimler Chrysler, MAN, Renault, Scania and Volvo have all agreed to adopt a common protocol that allows third parties access to on-board vehicle performance data. The Fleet Management System standard means data can be downloaded from any make of CAN-bus equipped vehicle using a standard communications port and in a format that can be analysed by most fleet management systems.
DaimlerChrysler and Volvo are currently still adapting the CAN buses on their latest models, but by mid 2003, all the major manufacturers will comply with the FMS standard. It is based on the Society of American Engineers' (SAE) J1939 protocol which specifies how the CAN bus works electrically including speed of data transmission and the protocol for the electronic messages. The FMS standard establishes what data will be broadcast over the CAN bus, and how it will be packaged and checked. The principle is that if each truck maker's CAN bus broadcasts the same amount of data at the same speed, any telematics unit can access it. The CAN buses all have a flrewall preventing any interference with critical safety systems, which means, in effect, that the telematics unit can listen and extra data form the CAN bus, but not transmit data to it. The on-board vehicle management computer controls and collects CAN bus data and some telematics units simply have an interface with it. Others retrieve data directly from the CAN bus which may be more suitable depending on how deep you want to dig. But remember collecting data is the easy part—only proper analysis makes it useful.