Steering Column/Instrument Panel NVH Analysis in Full Size Pickup Trucks Using MSC/NASTRAN - Part 1

Recent surveys of customer satisfaction with full size pickup trucks have raised the standards for passenger comfort and refinement of such vehicles. Customers for this type of vehicle demand performance levels for attributes such as NVH, ride, and handling that previously belonged to luxury passenger cars. Along with the increased passenger comfort, full size pickup trucks must retain a tough image and be as durable as the previous generation trucks.

The challenge is to design for NVH performance that can match and surpass many well behaved and “good” NVH passenger cars without any compromise in durability performance. One aspect of “good” NVH is a steering wheel which is free from vibration. As part of the development of a new design for a full sized pick up truck, an NVH subjective rating of 8-9 (10 is maximum) was targeted for the design of steering column/ instrument panel assembly. To support this subjective rating, the steering column was targeted to have 32 0 hz in-vehicle steering column vertical frequency and the instrument panel was targeted to have less than one millimeter displacement during vehicle operation.

In this paper, the authors demonstrate the design of the steering column/instrument panel assembly using FEA as a design tool. This enabled the designers to look at different concepts during the layout stage with the knowledge that the concepts already met the NVH requirements. The design and analysis tool used throughout the entire process was MSC/NASTRAN. The basic elements of NVH are frequency and the mode shape of interest which have been studied in detail. Also forced vibration analysis was conducted and compared against the targets set forth by the NVH team. The results of the analysis were confirmed with test data from prototype vehicles.