Quantitative Evaluation of Distortion in Sketching under Mono and Dual Axes Whole Body Vibration

Abstract

Performance of sedentary activities such as reading and writing, in trains is known to be affected by the vibrations. An experimental study was therefore initiated to investigate the interference perceived in sketching task under low frequency random vibration in both mono and dual axes. Thirty healthy male subjects participated in the study. Random vibration stimuli were excited in various axes in frequency range of 1-20 Hz at magnitudes of 0.4, 0.8 and 1.2 m/s 2 . The task required the subjects to sketch the given geometric figures such as circle, rectangle and triangle under vibration environment in two subject postures (sketch pad on lap and on table). Three performance methods were used to measure the effect of vibration stimuli and posture. They consisted of two specifically designed objective methods for percentage distortion measurement and one subjective method using Borg CR10 scale. The results revealed that the percentage distortion and difficulty in sketching increased with an increase in vibration magnitude and was found to be higher for vibration in Y-and Z-axis. Similar trend was observed for percentage distortion and difficulty in sketching for dual axes also. The perceived difficulty and impairment in sketching performance was greater while sketching on lap for X-axis, while the effect was just the reverse for other axes.

Effects of posture and vibration magnitude on seat to head transmissibility during exposure to fore-and-aft vibration

“…This implies that the motion of head is cross coupled for X-axis seat excitation and is more pronounced in backrest posture. Bhiwapurkar et al [30][31] found interference with reading activities due to visual disturbance in backrest posture in fore-aft seat vibration for same vibration magnitude and frequency range. For the forward lean posture, the absence of this second peak implies that the motion of head is small -probably because of the low transmission of X-axis motion of the spine.…”

“…The study is conducted on the vibration simulator developed as a mockup of a railway vehicle, housed in partially soundproof room. 30,31 It consists of a platform of 2 m  2 m size, fabricated from a light aluminum alloy frame with thick steel plates at the top and bottom to which the three exciters pushrods are bolted via ball joints. The platform incorporates a table and chairs with rigid wooden seats securely fixed.…”