Research On Fuzzy Assessment Of Riding Comfort Of Electric Bus Under Operating Conditions Based On Occupant Heart Rate Variability

At present,the research on vehicle ride comfort mainly focuses on the analysis of vibration response characteristics of vehicle-occupant,but seldom on the physiological response of occupants.Therefore,Heart Rate Variability-HRV analysis reflecting human autonomic nervous activity is introduced in this paper to evaluate the ride comfort of pure electric bus.In this paper,by collecting bus operation data and ECG signals of 23 passengers on a line in Xi’an under actual operating conditions,using wavelet technology and HRV technology,the occupant’s physiological response under the running state of the vehicle is analyzed.Meanwhile,the occupant’s subjective feeling,objective evaluation,HRV analysis and vehicle driving acceleration are comprehensively evaluated and analyzed by fuzzy evaluation,and an evaluation index of occupant comfort considering the occupant’s physiological response characteristics is proposed.According to GB/T 4970-2009 Vehicle Ride Test Method,this paper measures and collects the vibration response of the occupant’s seat and standing under the actual operating conditions of the vehicle,analyses the objective evaluation of the occupant’s comfort under different sitting postures(standing and sitting postures)and different subjective feeling of comfort,and finds that there are differences between subjective feeling and objective evaluation of comfort.While collecting vehicle driving data,ECG signals of different occupant postures are collected,and HRV analysis is carried out on ECG signals to obtain occupant physiological index data.According to the characteristics of occupant ECG signal,the appropriate wavelet basis function is selected by using wavelet transform and wavelet packet analysis technology to eliminate baseline drift and EMG noise in ECG signal and improve signal-to-noise ratio.The accurate results of extracted heart rate interval(RR interval)are guaranteed by de-trending and re-sampling.The ECG signals of 23 occupants are analyzed by time-domain,time-frequency and non-linearity methods.The results show that 1.HRV time-frequency analysis method is the most intuitive and effective one.When the occupants are uncomfortable,the peak values of power spectrum density occur in the high and medium frequency parts of time-frequency analysis.The comfort of sitting position is obviously better than that of standing position,and the influence of tangential(X-direction)acceleration on occupant comfort is more obvious.2.The values of(standard deviation of RR interval)and RMSSD(mean square root of RR interval)in HRV time domain analysis increase with the variation of comfort and have strong correlation.3.The ratio of long axis to short axis(SD1/SD2)in nonlinear analysis increases with increasing degree of discomfort.The relevant membership function is constructed,the fuzzy evaluation model of ride comfort is built,and the final ride comfort evaluation is obtained by combining objective evaluation,subjective feeling,HRV evaluation and driving acceleration.The results of the fuzzy evaluation are: 4th gear when standing(uncomfortable),3rd gear when sitting(uncomfortable),3rd gear when comprehensive comfort(uncomfortable).This paper studies the fuzzy evaluation of ride comfort of electric bus from the perspective of occupant physiology,which has a good application prospect.The research process and conclusions can provide reference for further exploration.