Fast and Efficient Detection of Shading of the Objects

The human thermal comfort, which has been a subject of extensive research, is a principal objective of the automotive climate control system. Applying the results of research studies to the practical problems require quantitative information of the thermal environment in the passenger compartment of a vehicle. The exposure to solar radiation is known to alter the thermal environment in the passenger compartment. A photovoltaic-cell based sensor is commonly used in the automotive climate control system to measure the solar radiation exposure of the passenger compartment of a vehicle. The erroneous information from a sensor however can cause thermal discomfort to the occupants. The erroneous measurement can be due to physical or environmental parameters. Shading of a solar sensor due to the opaque vehicle body elements is one such environmental parameter that is known to give incorrect measurement. The fundamental geometric principles of the intersection of a line segment and a plane can be used to determine if sensor is shaded, for given position of the sun with respect to a vehicle and geometry of the passenger compartment. However, realization of these principles using the fixed-point arithmetic is computationally expensive, due to their high memory and execution time requirements. The analytical method that uses relatively simple geometric relations is proposed to obtain the exact same results at significantly lower cost. The proposed method uses a constant azimuth curve to determine the range of elevation for each transparent body element of a vehicle, such as windshield, side glasses, rear glass and sun roof, for which a solar sensor is exposed to the direct-beam solar radiation. A sensor is said to be shaded if the current solar elevation angle is not included in any of the calculated ranges. The corrective action to the erroneous solar intensity while sensor is shaded, is suggested such that its influence on the thermal comfort of occupants is minimum.