Laboratory study as basis of the development for a seat testing procedure in horizontal directions

Abstract

Horizontal whole-body vibration (WBV) can have an influence on health and comfort of drivers. Driver seats with additional suspensions in x- and/or y-axis should reduce the influence of vibration on the driver. No standards or test procedures are available for testing seats with horizontal suspensions. A standard test procedure for seats with horizontal suspensions could be developed from a test protocol used in a recent inter-laboratory study. To reduce the variability of the results obtained by different laboratories or repetitions, the test procedures should carefully consider methodological aspects with relevance to the results. Specifications of typical signals obtained in practice, or well-defined random time series as a basis for generation of test signals, with defined signs of acceleration would enable identical excitations in time domain and could reduce the variability of results caused by the non-linearity of the seat–human system. Nine healthy subjects volunteered for the study to test a seat with suspensions in three directions. They were selected with regard to three groups of body mass (52.4–54.6, 75.5–77.1, 98–100.7 kg). A random signal and two signals obtained in practice (tractor and truck) were selected for excitations in x- and y-directions by a six DOF electro-hydraulic simulator (hexapod). The errors between the desired and measured accelerations were calculated. The error depends on the signal, the direction and the subject. In the time domain, the absolute value of the error ranged from 1.8% to 42.4%. The SEAT value generally depends on the body mass, but in some cases the SEAT value of a lighter subject was lower than the SEAT value of a heavy one. This indicates that only one heavy and one light subject are not suited to calculate reliable parameters for an evaluation and comparison of seats. The non-symmetric displacements of the seat frame in x-direction indicate the non-linear behaviour of the seat–subject system. Relevance to industry Driver seats with suspensions in horizontal directions can reduce the influence of WBV on the health-risk of drivers. Laboratory test procedures are helpful for the evaluation and design of seats, if the results obtained by different laboratories are comparable. The paper describes methodological aspects that affect the test results and their variability.