SAE International Study of Frequency Characteristics of Vehicle Motions for the Derivation of Inherent Jerk 2016-01-1681

Jerk in a vehicle is a feel of user which appears due to sudden acceleration changes. The amplitude and frequency components of the jerk defines quality of an engine or an AMT calibration tuning. Traditional jerk evaluation methods use amplitude (peak) of the jerk as a performance index and its frequencies are either used as weighing factor with amplitude or not taken into account. A method is proposed in this paper to quantify and differentiate the non-acceptable level of jerk which is perceivable to human body. Jerk is obtained by differentiating the acceleration data which contains the frequencies in the lower to higher range. Differentiation of such signal causes an amplification of undesired noise in both analog and digital circuits. This results in significant loss or disturbances in the useful data. In the process of filtering out such unwanted noise or signals, frequency characteristics of test data collected on vehicle in different driving conditions are analyzed for the identification of predominant frequencies. A Butterworth low pass filter is implemented for the analyzed cutoff frequency to remove the undesired signals from acceleration data thus ensuring analysis on actual jerk. This filter has the advantages of low order and higher attenuation of frequencies in pass band, improving the stability and accuracy of its response. The results are verified by carrying out subjective and objective assessment on test vehicle for perceivable jerk. The present work derives comprehensive method which can differentiate desired and perceivable frequencies from the test data and quantifies the actual jerk.