Investigation and Modeling for Mechanism of Human Slippage Sensation

点击翻译按钮获取中文摘要

In the present study, we attempted to apply the human dextrous grasping to robotics. Due to this, we are focusing on human slippage receptor relating closely to haptic sensing. First of all, in order to measure human capability of slippage sensing, we developed a slippage force presentation machine capable of presenting various slippage force on human fingers. Also, we adopted PEST (Parameter Estimation Sequential Testing) method as psychophysical experiment because it was able to obtain efficiently threshold and subjective equivalence and developed computer programs to control the present machine based on PEST method. In a series of experiments, we adopted slippage forces 2, 2.75, 3.5, 4.25 and 5 N as standard stimuli for PEST method. For smooth surface of acrylic board, rather small slippage force caused slight large Weber fraction (ratio of threshold and standard stimulus) 0.14 and Weber fraction was increasing with increasing standard stimulus. It means that detecting precision for slippage force is decreasing with decreasing slippage force. This result is quite normal phenomenon comparing with other sensations such as vision and hearing. Next, we examined influence of surface condition on threshold of slippage force. Abrasive paper surface coursed threshold to be smaller comparing with acrylic surface. This is because, since higher grasping force is needed to prevent subject fingers from slipping on the surface in the case of acrylic surface, it provides noise stimulus for human slippage receptors. Finally, we examined relationship between grasping force and output of EMG (electromyrogram) to obtain high correlation coefficient exceeding 0.9. It indicates that we can use EMG as a grasping force sensor.