HCC: Medium: Collaborative Research: Force Feedback for Fingertips

表面触觉是在物理表面（如触摸屏和触摸板）上创建可编程的触觉效果。与传统的力反馈设备不同，要求操作员抓住末端执行器，表面触觉设备必须直接向指尖提供反馈。近年来，随着触摸屏界面的迅速兴起，人们探索了许多表面触觉的方法，包括振动触觉、形状变形和可变摩擦。PI和他的团队开创了一种方法，该方法可以在每个指尖上产生可控的剪切力。指尖的力反馈（F3），让指尖有机会与基于物理的虚拟环境进行交互，就像力反馈设备使整个手都能做到的那样。使用F3，手指可以与具有质量，刚度和阻尼以及更复杂的动态（例如，碰撞，机制和力场）的虚拟物体进行交互。通过协调多个指尖的触觉效果，甚至可以产生更引人注目的错觉。然而，F3的技术、基础科学和应用仍处于起步阶段。F3的工作原理是将横向振动与某种形式的整流耦合起来。例如，一种方法是将表面的高频横向振动与摩擦减少效应同步，从而在每次振动时产生滑移过渡。摩擦力是通过静电力或声刺激来调节的。目前的方法在超声波频率下工作，但对这些频率下指尖的机械或电气行为知之甚少，或者如何优化从表面到手指的能量传递。这项研究将在三个主要领域产生新的知识：F3的物理基础，设备设计和交互设计。首先，将进行摩擦学和声学测量，以阐明剪切力产生的机制。高带宽摩擦计和光学成像系统将用于研究摩擦，定制的激励器将用于研究声能在指尖的传播。激光多普勒振动仪将用于测量表面波的传播，而磁共振弹性成像将用于研究皮下组织内剪切波的传播。分数微积分和有限元技术将用于建立生物学上合理的指尖摩擦学和力学模型，与数据相匹配。二是开发新一代高性能F3器件。有了良好的模型，就有可能设计出阻抗匹配的设备，从而使力产生最大化，并将能量浪费降到最低。此外，这些新设备将提供对多个指尖位置的力矢量的控制。第三，设计新颖的多指交互。关键的观点是，复杂的感知，比如可以抓住的“物体”，感觉好像它们在相对于表面移动，可以从适当协调的指尖力量中产生，这是由于格式塔式的分组原则。更广泛的影响：从历史上看，PI和他的团队在人机交互方面为同事提供技术并与他们合作时产生了最大的影响。受此启发，一个开源的F3工具包将被开发和共享。此外，本科生和高中生将参与研究，为开源工具包开发软件例程和示例应用程序。最后，该工具包将与研究人员已经实施的两项教学创新相结合：翻转教室和便携式实验室。

Surface haptics is the creation of programmable haptic effects on physical surfaces such as touch screens and touch pads. Unlike traditional force feedback devices that require the operator to grasp an end effector, surface haptic devices must provide feedback directly to the fingertips. With the dramatic rise of touch screen interfaces in recent years, many approaches to surface haptics have been explored, including vibrotactile, shape morphing, and variable friction. The PI and his team have pioneered an approach in which the surface generates controlled shear forces on each fingertip. Force Feedback for Fingertips (F3), gives fingertips the opportunity to interact with physics-based virtual environments, much like force feedback devices enable the whole hand to do. With F3, fingers can interact with virtual objects that have mass, stiffness and damping as well as more complicated dynamics (e.g., collisions, mechanisms, and force fields). By coordinating haptic effects at multiple fingertips, even more compelling illusions can be generated.The technology, underlying science, and application of F3 are, however, still in their infancy. F3 works by coupling lateral vibrations to some form of rectification. For example, one approach involves high-frequency lateral vibrations of the surface synchronized with a friction reduction effect, resulting in a slip-push transition at each oscillation. The friction is modulated by means of electrostatic forces or acoustical stimulation. Current approaches work at ultrasonic frequencies, but little is known about the mechanical or electrical behavior of fingertips at these frequencies, or how energy transfer from a surface to the finger can be optimized.This research will produce new knowledge in three main areas: the physical underpinnings of F3, device design and interaction design. First, both tribological and acoustic measurements will be made to elucidate the mechanisms by which shear forces are generated. A high-bandwidth tribometer and optical imaging system will allow friction to be studied, and a custom-built exciter will allow the propagation of acoustic energy in the fingertip to be studied. Laser Doppler vibrometry will be used to measure surface wave propagation while magnetic resonance elastography will be used to study shear wave propagation within the subcutaneous tissues. Fractional calculus and finite element techniques will then be used to build biologically plausible models of fingertip tribology and mechanics that match the data. Second, a new generation of high-performance F3 devices will be developed. Armed with good models, it will be possible to design impedance-matched devices so that force production is maximized and energy wastage is minimized. Additionally, these new devices will provide control over the force vector at each of multiple fingertip locations. Thirdly, novel multi-finger interactions will be designed. The key idea is that sophisticated percepts, such as "objects" that can be grasped and that feel as though they are moving relative to the surface, can emerge from properly coordinated fingertip forces due to Gestalt-like grouping principles.Broader Impacts: Historically, the PI and his team have had greatest impact when providing technology to and collaborating with colleagues in human-computer interaction. Inspired by this, an open source F3 kit will be developed and shared. In addition, undergraduate and high school students will participate in the research, developing software routines and sample applications for the open source kit. Finally, the kit will be integrated with two pedagogical innovations already implemented by the investigators: flipped classrooms and portable laboratories.