Accoto Dino, Donadio Alessandro, Yang Sibo, Mathews Nripan
Robotics Research Centre, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
School of Materials Science and Engineering, Nanyang Technological University, Singapore.
Soft Robot. 2022 Jun;9(3):509-517. doi: 10.1089/soro.2020.0199. Epub 2021 Jun 7.
Conventional grippers fall behind their human counterparts as they do not have integrated sensing capabilities. Piezoresistive and capacitive sensors are popular choices because of their design and sensitivity, but they cannot measure pressure and slip simultaneously. It is imperative to measure slip and pressure concurrently. We demonstrate a dual slip-pressure sensor based on a thermal approach. The sensor comprises two concentric microfabricated heaters maintained at constant temperature. An elastic dome, with embedded liquid metal droplets, is placed on top of concentric heaters. Heat transfer between sensor and the object in contact occurs through the elastic dome. This heat transfer causes changes in the power absorbed by the sensor to maintain its temperature and allows for measurement of pressure while identifying slip events. Liquid metal droplets contribute to enhanced thermal conductivity (0.37 W/m-K) and reduced specific heat (0.86 kJ/kg-K) of the polymer without compromising on mechanical properties (Young's modulus-0.5 MPa). For pressure monitoring, sensor measures change in power ratio against increase in applied force, demonstrating a highly linear performance, with a high sensitivity of 0.0356 N (pressure only) and 0.0189 N (slip with simultaneous pressure applied). The sensor discriminates between different contact types with a 96% accuracy. Response time of the sensor (60-75 ms) matches the measured response time in human skin. The sensor does not get affected by mechanical vibrations paving way for easy integration with robotic manipulators and prosthetics.
传统夹具落后于人类对手，因为它们没有集成传感能力。压阻式和电容式传感器因其设计和灵敏度而成为热门选择，但它们无法同时测量压力和滑动。同时测量滑动和压力势在必行。我们展示了一种基于热方法的双滑动压力传感器。该传感器包括两个保持恒温的同心微制造加热器。一个嵌入液态金属微滴的弹性圆顶放置在同心加热器上方。传感器与接触物体之间的热传递通过弹性圆顶发生。这种热传递会导致传感器吸收的功率发生变化，以维持其温度，并在识别滑动事件时允许测量压力。液态金属微滴有助于提高聚合物的热导率（0.37W/m-K）并降低比热容（0.86kJ/kg-K），同时不影响机械性能（杨氏模量-0.5MPa）。对于压力监测，传感器测量功率比随施加力增加的变化，表现出高度线性的性能，压力单独测量时灵敏度为0.0356N，同时施加压力时滑动测量灵敏度为0.0189N。该传感器区分不同接触类型的准确率为96%。传感器的响应时间（60-75ms）与在人体皮肤中测量的响应时间相匹配。该传感器不受机械振动影响，为与机器人操纵器和假肢的轻松集成铺平了道路。
