Development of a Thermal Model for a Heated Steering Wheel to Compensate Defective Feedback Variables

Along with the development and marketability of vehicles without an internal combustion engine, electrically heated surfaces within these vehicles are getting more and more important. They tend to have a quicker response while using less energy than a conventional electric heater fan, providing a comfortable temperature feel within the cabin. Due to the big area of heated surface it is important to spread the heating power in a way that different heat conduction effects to underlying materials are considered. In case an accurate sensor feedback of the targeted homogeneous surface temperature cannot be guaranteed, a thermal energy model of the heated system can help to set and maintain a comfortable surface temperature. For a heated steering wheel development project, different models have been created to meet that aim using mechanistic approaches starting with a predominantly first-order dynamics model and ending with a distributed parameter multi-feedback system. By comparing strengths and weaknesses of the individual models regarding -among others- thermal accuracy, processor, and resource usage, one approach finally was selected for implementation. In future applications, a surface temperature sensor may not even be necessary. The thermal 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.