Study On Friction Perception Of Human Skin And Quantitative Evaluation

The discomfort perception is an important indicator to evaluate the contacting frictional conditions of human skin when rubs against other objects. Although the discomfort perception is a human’s subjective feeling, it could be evaluated quantitatively by investigating the variation of frictional properties and physiological response of human skin on the base of regression analysis method. The results not only expand the theoretical foundation of skin tribology, but also provide a theoretical basis for the comfortable design and assessment of working or living implements which human skin often contact with.The frictional conditions of residual limb skin when contacting and rubbing with prosthetic sockets was simulated by using an UMT-Ⅱ Multi-specimen Biomedical Micro-Tribometer. The physiological responses were monitored by using a NeXus-10physiological feedback system and a FLIR E40Thermal Imager. The relationships between discomfort perception and the friction behavior and physiological response of human skin were comprehensively analyzed. The differences for discomfort perception between genders were discussed. Using partial least squares regression, a numerical model was set up between discomfort perception and skin friction behavior and physiological response changes.The main conclusions as follows:1. The discomfort perception of human skin strongly relates to the friction conditions. As the friction test, the surface temperature and the conductance value of the skin increased gradually, and the subjective feeling of frictional discomfort perception intensified. With normal force increasing, the friction force increased and friction coefficient decreased, the increments of skin temperature and conductance were not significant, while the amplitude and high-value wave crest number of electroencephalogram increased and the volunteers’ discomfort perception also enhanced; Under the same experimental condition, encouraged by the self-adaptation of human skin to external stimulus with the increasing number of test enhanced, the friction coefficient and friction force gradually reduced, as well as the increments of skin temperature and conductance also gradually reduced, meanwhile, the amplitude and high-value wave crest number of electroencephalogram decreased, and the volunteers’discomfort perception became weakened. The research indicated that the discomfort perception has much consistency with the friction characteristics and physiological response of skin, and the skin temperature, skin conductance and electroencephalogram could be used for representing the perception during the friction process of human skin.2. The friction characteristics and the physiological changes such as skin temperature and skin conductance of human skin exhibited no significant differences between genders; the amplitude and high-value wave crest number of electroencephalogram of the female were lower than that of the male in the relaxed state, however, under the same friction stimulation, the changes of the electroencephalogram and the degree of discomfort perception of female were stronger compared with the male volunteers.3. Under the support of regression analyzing software of SPSS and SIMCA-P, a further confirmation is numerically made that there exists a liner correlation between discomfort perception and skin friction behavior and physiological response by using ordinary least square estimate method, but it could not solve the multicollinearity problem among the independent variables. However, the use of partial least-square regression (PLS), not only solved the problem of multicollinearity, but also determined the best combination of the independent variables, including friction coefficient, skin temperature, and the amplitude and high-value wave crest number of electroencephalogram, which resulted in a model equation of PLS, between human discomfort perception and physiological indices and tribological stimulus. The accumulated explanatory capacity of the model for discomfort feeling was0.886and achieved a high accuracy. By using the model, the discomfort perception of human skin could be evaluated quantitatively.