When interacting with deformable objects, tactile cues at the finger pad help inform our perception of material compliance. Nearly all prior studies have relied on highly homogenous, engineered materials such as silicone-elastomers and foams. In contrast, we employ soft plum fruit varying in ripeness; ecological substances associated with tasks of everyday life. In this article, we investigate volitional exploratory strategies and contact interactions, for comparison to engineered materials. New measurement techniques are introduced, including an ink-based method to capture finger pad to fruit contact interactions, and instrumented force and optical sensors to capture imposed force and displacement. Human-subjects experiments are conducted for both single finger touch and two finger grasp. The results indicate that terminal contact areas between soft and hard plums are indistinguishable, but the newly defined metric of virtual stiffness can differentiate between the fruits’ ripeness, amidst their local variations in geometry, stiffness, and viscoelasticity. Moreover, it affords discrimination independent of one's touch force. This metric illustrates the tie between the deployment of active, exploratory strategies and the elicitation of optimal cues for perceptual discrimination. Compared to single finger touch, perceptual discrimination improves further in pinch grasp, which is indeed a more natural gesture for judging ripeness.

中文翻译：

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自然兼容物体的触觉探索策略引发虚拟刚度提示

当与可变形物体交互时，指垫上的触觉提示有助于告知我们对材料合规性的感知。几乎所有先前的研究都依赖于高度同质的工程材料，例如有机硅弹性体和泡沫。相比之下，我们采用成熟度不同的软李子；与日常生活任务相关的生态物质。在本文中，我们研究了意志探索策略和接触相互作用，以与工程材料进行比较。引入了新的测量技术，包括一种基于墨水的方法来捕获指垫与水果接触的相互作用，以及用于捕获施加的力和位移的仪器力和光学传感器。对单指触摸和双指抓握都进行了人类受试者实验。结果表明软李子和硬李子之间的终端接触区域无法区分，但新定义的虚拟刚度度量可以区分果实的成熟度，因为它们在几何形状、刚度和粘弹性方面存在局部变化。此外，它提供了独立于人的触摸力的辨别力。该指标说明了积极探索性策略的部署与感知辨别最佳线索的引出之间的联系。与单指触摸相比，捏握的感知辨别力进一步提高，这确实是一种更自然的判断成熟度的手势。和粘弹性。此外，它提供了独立于触摸力的区分。该指标说明了积极探索性策略的部署与感知辨别最佳线索的引出之间的联系。与单指触摸相比，捏握的感知辨别力进一步提高，这确实是一种更自然的判断成熟度的手势。和粘弹性。此外，它提供了独立于触摸力的区分。该指标说明了积极探索性策略的部署与感知辨别最佳线索的引出之间的联系。与单指触摸相比，捏握的感知辨别力进一步提高，这确实是一种更自然的判断成熟度的手势。