Advanced Automotive Fault Diagnosis
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LÔØI NOÙI ÑAÀU, ledklok
| 11.3.2 OBD3
Plans for OBD3 are currently under consider- ation, which would take OBD2 a step further by adding the possibility of remote data transfer. This would involve using remote transmitter/ transponder technology similar to that which is already being used for automatic electronic toll collection. An OBD3 equipped vehicle would be able to report emissions problems directly back to a regu- latory authority. The transmitter/transponder would communicate the Vehicle Identification Number (VIN) and any diagnostic codes that have been logged. The system could be set up to automati- cally report an emissions problem the instant the MIL light comes on, or alternatively, the system could respond to answer a query about its current emissions performance status. What makes this approach so attractive is its efficiency, with remote monitoring via the on-board telemetry, the need for periodic inspections could be eliminated because only those vehicles that reported problems would have to be tested. The regulatory authorities could focus their efforts on vehicles and owners who are actually causing a violation rather than just random testing. It is clear that with a system like this, much more efficient use of available regulatory enforcement resources could be implemented, with a consequential improvement in the quality of our air. An inevitable change that could come with OBD3 would be even closer scrutiny of vehicle emissions. The misfire detection algorithms cur- rently required by OBD2 only watches for mis- fires during driving conditions that occur during the prescribed driving cycles. It does not monitor misfires during other engine operating modes like full load for example. More sophisticated methods of misfire detection (as previously dis- cussed in Chapter 7) will become common place. These systems can feed back other information to the ECU about the combustion process; for example, the maximum cylinder pressure, deton- ation events or work done (via an Indicated Mean Effective Pressure (IMEP) calculation). This adds another dimension to the engine control system allowing greater efficiency and more power from any given engine design by just using more sophis- ticated ECU control strategy. Future OBD system will undoubtedly incorp- orate new developments in sensor technology. Currently the evaluation is done via sensors moni- toring emissions indirectly. Clearly an improve- ment would be the ability to measure exhaust gas composition directly via on-board measurement (OBM) systems. This is more in keeping with emis- sion regulation philosophy and would overcome the inherent weakness of current OBD systems; that is, they fail to detect a number of minor faults that do not individually activate the MIL, or cause exces- sive emissions but whose combined effect is to cause the production of excess emissions. The main barrier is the lack of availability of suitably durable and sensitive sensors for CO, NOx and HC. Some progress has been made with respect to this and some vehicles are now being fit- ted with NOx sensors. Currently there does appear to be gap between the laboratory based sensors used in research and reliable mass produced units that could form the basis of an on-board monitor- ing (OBM) system. The integration of combustion measurement in production vehicles produces a similar problem. tải về 7.07 Mb. Chia sẻ với bạn bè của bạn:
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