Abstract:
To improve ride comfort a reduction in the acceleration experienced by occupants is required. Simulation software and test equipment are able to measure reductions in acceleration that are too small for humans to perceive. It is therefore important to know how large the reduction in vibration should be for occupants to perceive an improvement in comfort. This study determined difference thresholds (DTs) for ten automotive engineers seated in a vehicle on a 4-poster test rig. Participants were exposed to all six axes of vibration. DTs were determined for two road profiles using vertical acceleration measured on the seat and seat rail. The two road profiles were obtained by scaling the magnitude of the vertical displacements of a test track used for ride comfort evaluations. The two roads had different magnitudes, but the same spectral shape, and were therefore used to investigate the validity of Weber's Law. The BS 6841 weighted r.m.s. magnitude of the vertical acceleration measured on the seat were 0.58 and 1.01 m/s2 for the two roads. An up-down-transformed-response (UDTR) test procedure was used with a three-down-one-up rule to determine DTs. There was no statistically significant difference found in the medians of the relative difference threshold (RDT), calculated from the vertical seat acceleration, over the two roads. The median RDT for the two roads were 10.1 % and 8.6 % respectively. Results were consistent with Weber's law.
