Comfort in cars: Estimating Equivalent Temperature for comfort driven Heating, Ventilation and Air Conditioning (HVAC) control

Equivalent Temperature is generally considered an accurate predictor for thermal comfort in car cabins. However, direct measurement of this parameter is impractical in fielded applications. The paper presents an empirical, multiple linear regression based approach for estimating body segment equivalent temperatures for car cabin occupants from different sensors within the car. Body part equivalent temperature at eight segments and cabin sensor data (air temperature, surface temperature, mean radiant temperature, humidity and solar load) was gathered in a variety of environmental and cabin conditions. 38 experimental hours of trials in a controlled environment and 26 experimental hours of realistic driving trials were used for training and evaluating the estimator's performance. The estimation errors were on average between 0.5 °C and 1.9 °C for different body parts for trials within a controlled environment, while for trials in realistic driving scenarios they ranged between 1 °C and 2 °C. This demonstrates that passenger body part equivalent temperature can be estimated using a multiple linear regression from environmental sensors and leads the way to comfort driven Heating, Ventilation and Air Conditioning control.