Development of a thermal model for a heated steering wheel to compensate defective feedback variables

Paper #:
  • 2017-01-1636

Published:
  • 2017-03-28
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Abstract:
Problem Already in the initial design failure mode analysis of this relatively young feature it became clear that an accurate sensor reading is critical to the performance of the heated steering wheel system. As the temperature reception capability of the human palm is very distinct, small deviations [≤0.1°??/??] from the targeted wheel temperature may be registered as "getting too hot" or "remaining too cold". As per industry standard, heated wheels only utilize a single sensor input to the temperature control circuitry, making it even more important for the sensor to reflect the current surface temperature. Certainly the sensor must be placed where it neither can be seen nor felt, decoupling surface from the sensor's temperature. Production tolerances for sensor placement on the heater mat along with heater mat placement tolerances relative to the armature's position add to the decoupling issue, causing unacceptably high or low steering wheel surface temperatures. Solution By creating a thermal energy model as an "observer", the sensor temperature can be checked upon plausibility. Upon a certain deviation from the expected value, the model may take over heat-up and regulation processes to provide a temperature of the steering wheel which is just right. For future applications, the sensor may not even be necessary. The model has been developed for versatility using physical laws/axioms and standardized interfaces for heat conduction, convection, and radiation. This enables the model to be used for other heated applications, too - by only adapting material parameters and the feedback controller layout. Presentation contents - Human perception of temperature/heat - Introduction to disturbance variables and measurement - Thermal model creation & implementation, implications, difficulties - Benefits and prospects of the thermal energy model and its transfer to other systems
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