Research On Quantitative Evaluation Method For Steering Comfort Of Intelligent Vehicle Occupant

Continuous driving for a long time will cause physiological fatigue and distraction of drivers,which will reduce their ability to control the vehicle.The development of automatic driving technology is one of the technical directions to solve this problem,and has become a research hotspot in the automotive field.For automatic driving,comfort is one of the direct embodiment of automatic driving control quality and an important factor that affects the subjective feeling of passengers in addition to conventional driving actions such as tracking and obstacle avoidance.Based on the National Natural Science Foundation of China（51875302）and National Natural Science Foundation of China（51675257）,the quantitative evaluation method of occupant comfort of intelligent vehicle under steering behavior is studied.The basic contents of the study include:（1）Design and conduct the steering comfort testThe experimental scene contains Slalom Test and urban scene test.The surface electromyography sensor and ECG signal sensor were used to measure the muscle activation and heart rate variability of the passengers.Occupants are asked to score their own comfort during the experiment.Finally,a matching data set including vehicle status information,occupant physiological signals and subjective evaluation of occupant comfort is formed.（2）Bioelectrical signal processingThe EMG and ECG physiological signals are processed and analyzed,and the characteristic indexes which can characterize the steering comfort are extracted.The root mean square value（RMS）of EMG is extracted from the EMG signals.On this basis,the cooperative contraction of the selected muscles is analyzed,and the cooperative contraction rate of the waist and neck of the passengers is calculated respectively.In the processing of ECG signal,the standard deviation of R-R interval（SDNN）,the standard deviation of adjacent R-R interval difference（RMSSD）,the ratio of R-R interval difference greater than50ms and 80ms to total interval（p NN50,p NN80）,average heart rate(HR_mean),heart rate fluctuation(HR_max-min)are obtained.（3）Research on the correlation between subjective evaluation and objective indexThe relationship between subjective comfort and EMG signals of the head,neck,trunk and other parts of the occupant in the process of snaking around the pile,as well as the changes of ECG signals of the occupant in different comfort states were studied.Through the correlation analysis between subjective evaluation and physiological indexes,the key physiological indexes with high correlation with occupant comfort evaluation are selected.（4）Establishment of passenger steering comfort evaluation modelThe key physiological indexes were analyzed by principal component analysis,and the dimensions of variables were reduced to extract muscle load factor,heart rate variability factor and heart rate fluctuation factor.Three common factors were taken as independent variables and occupant comfort evaluation as dependent variables.The objective physiological indexes of passengers are corresponded with the subjective feeling of comfort,which eliminates the subjective difference of passengers to a certain extent and makes the evaluation result of comfort more objective and accurate.