Evaluation of Virtual Light Touch Phenomenon by Vibrotactile Stimulation Control Based on Body Fluctuation

Abstract

An increasing frequency of fall accidents associated with demographic aging in Japan has given rise to a need for effective fall prevention methods. Elderly people often use support devices such as canes and walking frames to reduce the risk of falling, but such measures may be inappropriate for certain environments. Previous research has shown that unsteadiness can be mitigated via light touch contact (LTC) with curtains or similar object at a force of up to around 1N, and the authors also previously proposed a virtual light touch contact (VLTC) approach based on LTC. VLTC supports standing stability based on a surrounding virtual partition connected to a vibrotactile fingertip stimulator. It is known that the posture retention effect is not achieved via simple continuous fingertip stimulation;rather, vibrotactile stimulation is required for control based on fingertip motion characteristics such as acceleration. However, with LTC the effect can be achieved via constant contact with a piece of paper or similar object without the need for fingertip movement. Assuming that reaction force from a fixed point fluctuates with body sway or psychological tremors in LTC, the LTC effect may be achievable by reproducing such fluctuations via vibrational stimulation. In this study, the authors proposed a novel VLTC method involving the use of vibration stimulation control to reproduce fluctuations in contact reaction force caused by the individual’s movement based on fingertip acceleration data. Verification of the method indicated a reduction of postural fluctuations similar to that achieved with LTC. This finding suggests that reduction of center-of-gravity sway achieved with LTC may be associated with slight changes in reaction force from a fixed point, which improves the position sense of the fingertip.