Study On Thermal Comfort Of Automobile Based On Subjective Evaluation

With the popularization of automobiles and the improvement of people’s quality of life,consumers are increasingly demanding the thermal comfort of automobiles.As an important aspect of automobile comfort,thermal comfort has become the focus and research focus of automobile manufacturers and consumers.The thermal environment inside the vehicle is different from the thermal environment in the building,its space is narrow,the air fluidity is poor,and the moving property of the vehicle makes the solar radiation of the vehicle change at any time,which will have an impact on the thermal environment inside the vehicle.The thermal comfort of the car body is not only related to the thermal environment,but also to the subjective feeling of the human body,and the sensitivity of different parts of the body to the thermal environment is different.Therefore,it is necessary to study the thermal comfort evaluation model and test method suitable for the vehicle passenger compartment.This article refers to some domestic and foreign research results in the automotive thermal comfort,combined with the existing test conditions,to carry out human thermal comfort test.Through the measurement of the thermal environment of a certain SUV vehicle during the summer exposure and air-conditioning cooling stages,the changes in the parameters such as the air temperature,relative humidity,and average radiation temperature in the vehicle were obtained;and a subjective questionnaire survey of human thermal comfort was taken to obtain the subjective thermal comfort of the human body during the cooling period.Through processing and analysis of data,the characteristics of the thermal environment in the vehicle and the overall and local thermal comfort of the human body are studied.Using the PMV-PPD and the equivalent temperature evaluation index to objectively evaluate the overall and local thermal comfort of the human body.The prediction model of local thermal comfort of human body based on objective thermal environment parameters is established by support vector machine(SVM).The test data is processed,and the training set and test set are selected.After normalizing the sample data,the radial basis kernel function is selected as the prediction kernel function,and the parameters of the kernel function parameters are optimized through the grid optimization method.Taking the air temperature,relative humidity,average radiation temperature and body metabolism as independent variables,and the local thermal comfort as the dependent variable,human thermal comfort prediction models for the human head,trunk,upper limbs,and lower limbs were established.The prediction results show that the support vector machine method can be used to predict the local thermal comfort of the human body.Study the relationship between local thermal comfort and overall comfort.Using the concept of support vector machine classification,the training samples and test set classification,normalization,selection of kernel functions,parameter optimization,etc.were performed on the test samples,and any three local thermal sensations were used to establish the overall comfort prediction model.Then use all the human body’s local thermal sensation to predict overall comfort.From the prediction results,it can be seen that the use of thermal sensations from all parts of the human body can better predict the overall comfort of the human body.The accuracy of classification using all human body building prediction models is above 85%,which satisfies engineering applications and illustrates the applicability of the support vector machine approach.