Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
Ultrasonics. 2020 Jul;105:106129. doi: 10.1016/j.ultras.2020.106129. Epub 2020 Mar 14.
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 (R = 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 (R = 0.9947, 0.9842, and 0.9935, respectively) with sample's modulus and can be considered as indicator candidates.
本文提出了一种基于机电类比的超声触觉传感器振动集中器的混合设计方法。使用安装有振动集中器的触觉传感器对弹性模量在 14kPa 到 150kPa 之间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，如共振频率偏移和等效电导，重点研究了它们作为新的刚度指标的可行性。作为触觉传感器的一种变体，超声触觉传感器具有高灵敏度和最小接触物体的优点，优于基于力-位移原理的传统触觉传感器。它们检测机械振动特性的变化，主要是传感器的共振频率偏移，作为物体机械特性的指标。振动集中器已被广泛采用以提高超声触觉传感器的性能，但它的设计尚未得到系统考虑。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。在机械方面，采用阻抗类比设计了一种用于传感器的超声振动集中器，以实现接触点的定位并增强在~40kHz 时的振动行为。在电方面，我们使用迁移率类比从实验室环境中的触觉传感测试中得出电参数。通过机械和电气特性测试证明了设计的能力。通过从触觉传感测试中研究各种电参数，发现由机电分析确定的等效电导与样品的弹性模量之间几乎具有完美的线性关系（R=0.9998），范围从 10kPa 到 70kPa，并且显示出作为软材料新的刚度指标的潜力。进一步的分析表明，电确定的串联共振频率偏移、并联共振频率偏移和最大相位角频率偏移与样品的模量也具有极好的线性关系（R=0.9947、0.9842 和 0.9935），可以考虑作为指标候选者。
