Vezzoli Eric, Vidrih Zlatko, Giamundo Vincenzo, Lemaire-Semail Betty, Giraud Frederic, Rodic Tomaz, Peric Djordje, Adams Michael
IEEE Trans Haptics. 2017 Apr-Jun;10(2):196-207. doi: 10.1109/TOH.2017.2671432. Epub 2017 Feb 17.
Ultrasonic vibration is employed to modify the friction of a finger pad in way that induces haptic sensations. A combination of intermittent contact and squeeze film levitation has been previously proposed as the most probable mechanism. In this paper, in order to understand the underlying principles that govern friction modulation by intermittent contact, numerical models based on finite element (FE) analysis and also a spring-Coulombic slider are developed. The physical input parameters for the FE model are optimized by measuring the contact phase shift between a finger pad and a vibrating plate. The spring-slider model assists in the interpretation of the FE model and leads to the identification of a dimensionless group that allows the calculated coefficient of friction to be approximately superimposed onto an exponential function of the dimensionless group. Thus, it is possible to rationalize the computed relative reduction in friction being (i) dependent on the vibrational amplitude, frequency, and the intrinsic coefficient of friction of the device, and the reciprocal of the exploration velocity, and (ii) independent of the applied normal force, and the shear and extensional elastic moduli of the finger skin provided that intermittent contact is sufficiently well developed. Experimental validation of the modelling using real and artificial fingertips will be reported in part 2 of this work, which supports the current modelling.
采用超声振动以一种能引发触觉感受的方式来改变指垫的摩擦力。先前已提出间歇性接触和挤压膜悬浮的组合是最有可能的机制。在本文中，为了理解由间歇性接触控制摩擦调制的潜在原理，开发了基于有限元（FE）分析的数值模型以及弹簧 - 库仑滑块模型。通过测量指垫与振动板之间的接触相移来优化有限元模型的物理输入参数。弹簧 - 滑块模型有助于解释有限元模型，并导致确定一个无量纲组，该无量纲组能使计算出的摩擦系数近似叠加到该无量纲组的指数函数上。因此，有可能使计算出的摩擦相对减小合理化，即（i）取决于振动幅度、频率、装置的固有摩擦系数以及探索速度的倒数，并且（ii）只要间歇性接触充分发展，就与所施加的法向力以及指皮肤的剪切和拉伸弹性模量无关。本文第二部分将报告使用真实和人造指尖对该模型进行的实验验证，这支持了当前的建模。
