Comparison of Measurement Methods for Evaluating Displacement of Commercial Vehicle Seats 2019-01-1481
Vehicle seats and seat suspension have been evolving ever since the introduction of seats with built-in, integral suspensions. Measuring the relative displacements of the seat suspension may help better understand the magnitude and frequency of displacements the seat suspension and ultimately the occupant is exposed to. These displacement measurements may complement acceleration measurements and may provide additional information to help improve vehicle seat design. Displacement can be measured directly with lasers and potentiometers, but it would be less complicated if accelerometers, already being used to measure and characterize the vehicle and vehicle seat vibration, could be used to measure the displacement. Accelerometers can produce relatively accurate, correlated displacement results from well behaved, controlled, sinusoidal cyclical vibrations, but their utility for measuring real-world random vibration needs further evaluation and characterization. This paper will compare gold-standard methods for measuring vertical seat displacements directly to displacements measured and derived by double integrating the vertical accelerations from accelerometers. Actual field displacement, acceleration and GPS measurements were collected from vehicles as they travelled over different road types. In this paper the directly measured displacement data will be compared to the accelerometer derived displacements. Differences between the two techniques and the displacement differences across the different road types encountered will be characterized with respect to frequency, amplitude, phase, and coherence. A major difference was the large magnitude multi-centimeter displacements measured during the impulsive road events compared to the relatively small, sub-centimeter, cyclical displacements measured when travelling on city streets, highways and freeways. Designing commercial vehicles seats to handle these two displacement extremes poses a current and future challenge.
James Haylett, Peter Johnson
CVG, Univ of Washington
Noise and Vibration Conference & Exhibition