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Correlation of Objective and Subjective test results for Ride comfort with Heave, Pitch and Roll motion for a Passenger Vehicle
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on November 21, 2019 by SAE International in United States
Event: NuGen Summit
Research Objective The importance of evaluating ride comfort with high degrees of accuracy objectively and its correlation with subjective perception is increasing day by day because of the long duration of the driving experience. The complex motion of the vehicle which is the combination of heave, roll and pitch motion is responsible for causing extreme uneasiness to the driver as well as the passenger. In this paper, ride comfort evaluation is done on the highway with similar traffic conditions with the help of Vibration Dose Value Analysis, Suspension Working Space and Ride Diagram methods for two hatchbacks and its correlation with the complex motion like choppiness of the vehicle is established that will help us to enhance the driver ride experience. Methodology The ride testing is performed for two hatchbacks on a highway road with different kinds of terrain ranging from highly uneven road roughness to moderately smooth surface for a speed range of 60-100 kmph. The road environment is chosen for testing in order to record and analyze the most practical vehicle response to the road excitations. The different sensors used for the testing are mentioned below with their respective mounting locations. 1. Tri-axial Seat pad Accelerometer Driver and passenger seat pad Driver and passenger backrest 2. Tri-axial accelerometer Vehicle Floor (Driver end) Vehicle Floor (Passenger end) 3. Inertial Measurement Unit Near to CG of the vehicle 4. Potentiometers Across all the four suspension systems The correlation between the heave motion, roll angular velocity and pitch angular velocity and its effect on ride comfort are analyzed by carrying out the objective and subjective tests. Furthermore, a subjective test will be performed for the same in order to validate the results with human perception. Results The vertical acceleration of driver seat pad, derivatives of roll and pitch angle w.r.t time of vehicle are analyzed in both time and frequency domain. The probability density functions of heave, roll and pitch motion are plotted and compared for speeds at 60,80 and 100 kmph. Vibration dose values are obtained as 1.43, 1.39, 2.38 m/s1.75 for different speeds respectively. The response of the suspension system analyzed in the form of suspension working space informs about the cause of complex motion of the vehicle. The FFT of the heave, roll and pitch motion are plotted that confirms the results obtained from the time domain data. The Joint Probability Density function is plotted for understanding the correlation of heave with pitch and roll motion. On comparing these results with the Vibration dose values we know that for this type of test conditions with the increase in speed of the vehicle, pitch and roll motion also affect the comfort levels of the driver as well as the passenger. Limitations of this study The results obtained and the correlation established are only valid for highway road conditions. They can’t be used to predict the same for some different road conditions. The correlation between heave, roll and pitch motion can be improved with continued research in the same domain. What does the paper offer that is new in the field in comparison to other works of the author? The evaluation methods for ride assessment are used in order to study and analyze the effect of the complex motion of the vehicle on the ride comfort in order to achieve high levels of accuracy while measuring the ride of the vehicle. Conclusion From the probability density plots for roll and pitch angular velocities at 60,80 and 100 kmph it is clearly evident that pitching of the vehicle is more dominant than the roll motion and the magnitude of pitch increases with the increase in speed of the vehicle. It shows that the heave motion decreases whereas the roll and pitch motion increase with an increase in speed. Finally, comparing these relationships for two vehicles, this study helps in finding the best vehicle in terms of ride comfort for given test conditions.