This paper presents a dynamic model for the identification of asymmetric hysteresis in the force response of the fingertip under cyclic local deformation of the fingertip soft tissues. Viscoelastic effects, marked anisotropy and nonlinearity contribute to the hysteretic behaviour of the force of the fingertip undergoing indentation. The fingertip force in response to an indentation stimulus varies along the loading and unloading cycles; the resulting hysteresis loops are asymmetric. The asymmetry arises from the simultaneous convexity of the branches of the hysteresis loop. The proposed model belongs to the class of multistate friction models that can effectively describe the hysteresis in the presliding regime of motion of general mechanisms with friction, by exploiting a mechanical analogy obtained through the concatenation of multiple elasto-plastic elements. The multistate model, which provides the mechanical representation of the fingertip response through a set of newly-conceived switching elements and viscoelastic blocks, can reproduce the convex and asymmetric hysteresis loops of the fingertip mechanical response, including the viscoelastic effects of stress relaxation and the influence of time interval between consecutive cycles of indentation.

The model has been validated through the experimental identification of fingertip indentation tests performed on an optomechanical test-rig. This model potentially opens the way for efficient model-based control strategies of servomechanisms involved in tactile and haptic displays and interfaces.

本文提出了一种动态模型，用于识别在指尖软组织循环局部变形下指尖力响应中的不对称滞后。粘弹性效应、显着的各向异性和非线性会导致指尖压痕力的滞后行为。响应压痕刺激的指尖力随着加载和卸载循环而变化；由此产生的磁滞回线是不对称的。不对称性源于磁滞回线分支的同时凸性。所提出的模型属于多态摩擦模型类，可以有效地描述具有摩擦的一般机构在运动的预滑动状态下的滞后现象，通过利用通过多个​​弹塑性元素的串联获得的机械类比。多态模型通过一组新构思的开关元件和粘弹性块提供指尖响应的机械表示，可以再现指尖机械响应的凸形和非对称滞后回线，包括应力松弛的粘弹性效应和影响连续压痕循环之间的时间间隔。

该模型已通过在光机械测试台上进行的指尖压痕测试的实验识别得到验证。该模型可能为涉及触觉和触觉显示和界面的伺服机构的高效基于模型的控制策略开辟了道路。