1995-05-01

Objective Measurement of Automatic Transmission Shift Feel Using Vibration Dose Value 951373

An objective measure of automatic transmission shift disturbance is an important tool in many phases of the vehicle design process. To be useful, the objective measure must be directly related to the human perception of shift severity. Although it has been generally agreed that the objective measure should be some function of the fluctuation of vehicle fore/aft motion during the shift, measures used in the past, such as peak acceleration and rate of change of acceleration, fail to accurately reflect human perception when comparing two vehicles with very different shift mechanisms.This paper examines a particular function, the vibration dose value (VDV), which has been used to quantify human reaction to numerous types of vibration. When applied to vehicle fore/aft acceleration during a transmission shift, this function produces a single output number proportional to the driver's sensation of the severity of the shift, regardless of the character of the acceleration signal. Extensive customer and expert driver evaluations are described, which confirm correlation between the VDV of a properly filtered vehicle acceleration signal, and subjective ratings of the disturbance of a shift. The concept of subjective/objective correlation is also explored.

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