Abstract
Engineering Objective:
Higher fuel efficiency and lower emissions are the key objectives for the modern engines. Those crucial objectives are reached through advanced air (intake & exhaust) and thermal (cooling) management which are supported by several control loops relying on a position sensor and an actuator (pneumatic & electrical). Given the harsh environment (temperature, vibrations…) and the reliability and accuracy expectations, contactless (non-contacting) position sensors are nowadays considered as mandatory and will eventually replace the historical contacting potentiometers.
Methodology:
Starting from the advantages and weakness of the contacting position sensor (benchmark), this paper introduces the major contactless technologies implemented for engine management applications with an in-depth review of their benefits and disadvantages. Magnetic (Hall-Effect, IMC®/Triaxis®, Magnetoresistive…) and inductive (Eddy Current, Variable Transformer, LC…) sensing approaches are introduced, described and compared.
Results:
Those non-contacting position sensors enable a myriad of engine management applications (gasoline and diesel) targeting a decrease of the fuel consumption (improved mileage and reduced CO2 emissions) as well as lower and cleaner emissions (NOX, CO, particulate matter...) to meet the norms imposed by the respective legislations (e.g. Euro 6, Beijing VI…) for air quality. A pretty exhaustive presentation of the applications is provided, e.g. ETC, CVVL, EGR, VGT… To the contrary of the passive potentiometers, the contactless solutions are active and associated to integrated circuits for the entire sensors or for the signal-conditioning. Combined with modern communication protocols (e.g. SAE J2716 a.k.a. SENT), the contactless sensors are able to broadcast additional environmental (e.g. temperature) or diagnostic information (anticipating future ISO26262/ASIL requirements).
Limitations:
This paper is limited to the scope of engine management. However, the sensing technologies which are covered are also addressing many transmission, chassis/body and interior applications.
Differentiating Factors:
The paper is focused on the technical approach for both the sensing technologies and the supported applications. It is driven by a non-commercial approach in order to offer at a glance a fair review of the competing position sensing technologies and provide a large review of the automotive applications portfolio (engine management).
Conclusions
In a technology battle engaged for more than two decades, the contactless technologies clearly take the advantage vs. the contacting potentiometers which have pioneered the first engine management applications (e.g. ETC). They clearly now enables many more applications aiming for top-notch robustness and performances (down-sizing, increased mileage, lower and cleaner emissions) combined with advanced features such as digital reporting protocol and on-board diagnostics.
KEYWORDS – position, sensors, contactless, engine, fuel-efficiency, emissions