Analyzing the Effect of Unsprung Mass on Ride Characteristics of an Electric Vehicle

Student’s Name Fareed Khan P. AE (FT-2016) Academic Monish Gowda M. H. and Ashok C. Meti Supervisor(s) Fareed Khan P. Industrial [email protected] Supervisor(s) Ph. No: 0 80955 98718 Keywords: Unsprung Mass, Displacement Transmissibility, Ride Comfort, Electric Vehicles, Suspension

Abstract: Automotive industry is taking a new step for green environment and this is definitely not trending news to the world. In the near future most of the IC engines will be replaced with electric vehicles (EV) and the main reasons for this are air pollution and limited availability of petrol and diesel. In electric vehicles unsprung (푚푢) mass will vary due to layout of batteries and motor. With the variation in 푚푢, ride comfort and handling of the vehicle will diminish. Hence a good suspension system is very important to maintain a high standard ride comfort. The present work is aimed at developing a systematic methodology that leads to arriving at spring stiffness and damping co-efficient for the selected mass ratio (푚푠/푚푢) of an electric vehicle for improved ride comfort. In order to analyze the ride characteristics, mathematical modelling was built using 2 DOF quarter car suspension model and solved using MATLAB software. The benchmark EV was chosen and the vehicle parameter inputs were given as input to the MATLAB software. From the displacement and acceleration results obtained from MATLAB code for all the varying unsprung mass the ride characteristics like Displacement Transmissibility ratio (μ), Suspension Travel ratio (η) and Absolute acceleration ratio (υ) were analyzed. All these results are then plotted with ratio of sprung to unsprung mass natural frequency (훼) values. When the RMS ride parameters are plotted with natural frequency ratio 훼, there is 5.7-57.14% and 3.9-16% increase in RMS transmissibility ratio (Sμ) and RMS absolute acceleration (Sυ) respectively with increase in 훼. Whereas in the case of RMS suspension travel ratio there is 8.5-157% increase in RMS suspension travel (Sη) ratio with reduction in 훼 value. From analyzing the result trends 훼=0.2 was selected to achieve less displacement, improved ride comfort and reduced suspension system space for easier accommodation. From the selected 훼 value the spring stiffness and damping co-efficient are found through developed MATLAB program.

2 DOF quarter car model RMS Transmissibility Ratio (Sμ) vs Mass Ratios (ϵ) for varying 훼

Conclusion: From the analysis 훼=0.2 was selected to achieve better ride comfort and reduced suspension space and the spring stiffness and damping co-efficient are found through developed Matlab program.

Book of Abstracts 32 January 2019