Quantification of NVH Parameter for AT/AMT Vehicle Target Setting Based On Customer Driving Patterns

Abstract

This study aimed to identify novel NVH parameter/s which govern the customer’s experience during wide open throttle (WOT) for automatic transmission and automatic manual transmission vehicles. As the demand for automated transmissions among customers is challenging NVH engineers to enhance the transmission performance. In automatic transmission vehicles at gear shifts, there is distinct noise and vibration present, which needs to be addressed to improve the ‘shift feel’ and ride quality. For the traditional manual transmission vehicles, SPL (Sound Pressure Level) and AI (Articulation Index i.e. ease of speech interpretation) are the acoustics parameters that sufficiently define the target. However, in case of automatic transmission vehicles, these two parameters are found to be inadequate for target setting. As part of the research, a survey was done among to determine key phenomenon subjectively felt during the automatic gear-shifting. The identified phenomenon were further used to formulate semantic pairs for jury assessments. A factor analysis on the subjective assessment data revealed three semantic sub dimensions. Based on the four descriptive phrases, a measure with semantic scales on each sub dimension was designed and employed in an experiment as the second research. Approx. 15 participants drove and evaluated seventeen vehicles with WOT condition. Participants were requested to make WOT on high-speed test track. After each event, participants were requested to complete the rating of the semantic differential phrases as well as absolute rating and vehicle ranking on the WOT condition. Along with this subjective rating, changes during of mechanical properties the event also were recorded as an objective parameter. This comprised sound pressure level at DEL IN, vibration level at head rest, sound quality measures, acceleration time and vehicle speed. Consequently, a series of statistical analyses showed how one was related to the others. The objective criteria that are related to the subjective quality sub dimension. On the basis of the evaluation of the driving intentions and speed sub dimensions, models of target setting parameters were also created. In relation to mechanical control factors, the study established a novel framework for evaluating subjective driving quality.