This paper proposed a hybrid design approach of a vibro-concentrator, a vital component of an ultrasonic tactile sensor, by using electro-mechanical analogy. Lab experiments on soft materials with elastic modulus from 14 kPa to 150 kPa were conducted using the tactile sensor installed with the vibro-concentrator to verify the performance of the design. Various mechanical and electrical parameters, such as resonance frequency shift and equivalent conductance, were discussed, focusing on their feasibility as new stiffness indicators. As a variant of tactile sensors, ultrasonic tactile sensors have the advantage of high sensitivity and minimal contact with the object over traditional tactile sensors based on force-displacement principle. They detect the changes in mechanical vibration characteristics, mostly resonance frequency shift of the sensor, as an indicator of the mechanical properties of the object. A vibro-concentrator has been frequently adopted to improve the performance an ultrasonic tactile sensor, but its design has yet been systematically considered. We propose a hybrid design approach based on electro-mechanical analogy for both mechanical and electrical analyses. Mechanically, impedance analogy was adopted to design an ultrasonic vibration concentrator for the sensor to localize the contact and reinforce the vibration behavior at ~40 kHz. Electrically, we used mobility analogy to derive electrical parameters from the tactile sensing tests in lab environment. The competence of the design was demonstrated by mechanical and electrical characteristic tests. By investigating various electrical parameters from tactile sensing tests, the equivalent conductance determined by the electro-mechanical analysis was found to have almost perfectly linear relationship (R2 = 0.9998) with the samples' elastic modulus ranging from 10 kPa to 70 kPa, and showed its potential as a new stiffness indicator for soft materials. Further analyses suggested that the electrically determined series resonance frequency shift, parallel resonance frequency shift, and maximum phase angle frequency shift also had excellent linearities (R2 = 0.9947, 0.9842, and 0.9935, respectively) with sample's modulus and can be considered as indicator candidates.

中文翻译：

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基于机电类比的超声波触觉传感器设计

本文通过使用机电类比，提出了一种振动集中器的混合设计方法，振动集中器是超声波触觉传感器的重要组成部分。使用安装有振动集中器的触觉传感器对弹性模量从 14 kPa 到 150 kPa 的软材料进行了实验室实验，以验证设计的性能。讨论了各种机械和电气参数，例如共振频移和等效电导，重点关注它们作为新刚度指标的可行性。作为触觉传感器的一种变体，超声波触觉传感器与基于力-位移原理的传统触觉传感器相比，具有灵敏度高、与物体接触少的优点。它们检测机械振动特性的变化，主要是传感器的共振频移，作为物体机械性能的指标。振动集中器经常被用来提高超声波触觉传感器的性能，但其设计尚未得到系统的考虑。我们提出了一种基于机电类比的混合设计方法，用于机械和电气分析。在机械上，采用阻抗类比为传感器设计超声波振动集中器，以定位接触并增强~40 kHz 的振动行为。在电气方面，我们使用移动性类比从实验室环境中的触觉传感测试中推导出电气参数。机械和电气特性测试证明了设计的能力。通过研究触觉传感测试的各种电气参数，发现由机电分析确定的等效电导与样品的弹性模量范围从 10 kPa 到 70 kPa 具有几乎完美的线性关系（R2 = 0.9998），并显示其作为软材料新刚度指标的潜力。进一步的分析表明，电学确定的串联谐振频移、并联谐振频移和最大相角频移与样品的模量也具有极好的线性（分别为 R2 = 0.9947、0.9842 和 0.9935），可被视为候选指标。