触摸法评价物体柔软性的感知觉力学原理分析

MECHANISTIC PRINCIPLES OF SENSORY ANALYSIS ON OBJECT SOFTNESS BY TOUCH MEANS

物体柔软性的触觉认知机理是当前感官工程研究的重点.基于触摸法评价物体柔软性时物体与指尖软组织的力学作用过程,及指尖皮下机械刺激感受体接受机械刺激的模式,建立了与这一机械作用过程等效的生物力学模型;基于该模型,提出并证明了表征触觉系统感应、辨别物体柔软性的能力指标——机械敏感性和感觉敏感性;以提出的两个指标,参数化讨论了人的触觉系统在判断和辨别物体柔软性的一般力学原理.理论研究证明,以触摸方式评价物体柔软性时,皮下触觉感受体及相应高级认知系统的感知能力取决于物体与皮肤软组织的抗压力阻,且与触摸力的动态变化有关.也正是传递机械信号的介质——软组织的可变形性致使触觉感测系统有别于实验室压缩仪的工作模式.

It is a fascinating field for elucidating and quantifying the tactual performance of object softness in sensory engineering. In term of the macroscopically contacting interaction between fingerpad and object surfaces as well as the touching means, an equivalent biomechanical model is developed to simulate the process of cutaneous low-threshold mechanoreceptors sensing object softness. And then, two indexes which characterize the ability of human tactual system in detecting and discriminating object softness, namely mechanical sensitivity and perceptual sensitivity are established on the basis of the developed biomechanical model. By the established indexes, it is discussed parametrically that the general mechanistic principle that human tactual system processes the property of object against compression. With the former discussion in theory, it is concluded that the mechanical resistance of object against compression is the tentative potential physical property on which human tactual system discriminate the softness of objects. Furthermore, the decetability and discriminability of human tactual system in object softness depends on the ratio of the mechanical resistance against compression of objects to that of soft tissues within fingertip, and on the touching force exerted by fingertip. Meanwhile, in terms of the deformable medium of soft tissues within human fingertip communicating mechanical resistance of the detected objects against compression, the working principle of human tactual system is different from that of the manmade testing machine with a designed sensitivity, and human can not discriminate from all of compliant objects with significant instrumental differences by compression testers. All of conclusions will help to understand the variation of estimation on fabric softness by touch means, and to improve the performance of prediction model and virtual rendering of object softness.