Tactile Sensing for Robotic Applications

This chapter provides an overview of tactile sensing in robotics. This chapter is an attempt to answer three basic questions: \u2022 What is meant by Tactile Sensing? \u2022 Why Tactile Sensing is important? \u2022 How Tactile Sensing is achieved? The chapter is organized to sequentially provide the answers to above basic questions. Tactile sensing has often been considered as force sensing, which is not wholly true. In order to clarify such misconceptions about tactile sensing, it is defined in section 2. Why tactile section is important for robotics and what parameters are needed to be measured by tactile sensors to successfully perform various tasks, are discussed in section 3. An overview of `How tactile sensing has been achieved\u2019 is given in section 4, where a number of technologies and transduction methods, that have been used to improve the tactile sensing capability of robotic devices, are discussed. Lack of any tactile analog to Complementary Metal Oxide Semiconductor (CMOS) or Charge Coupled Devices (CCD) optical arrays has often been cited as one of the reasons for the slow development of tactile sensing vis-\ue0-vis other sense modalities like vision sensing. Our own contribution \u2013 development of tactile sensing arrays using piezoelectric polymers and involving silicon micromachining - is an attempt in the direction of achieving tactile analog of CMOS optical arrays. The first phase implementation of these tactile sensing arrays is discussed in section 5. Section 6 concludes the chapter with a brief discussion on the present status of tactile sensing and the challenges that remain to be solved

POSFET tactile sensing arrays using CMOS technology

This work presents fabrication and evaluation of novel POSFET (Piezoelectric Oxide Semiconductor Field Effect Transistor) devices based tactile sensing chip. In the newer version presented here, the tactile sensing chip has been fabricated using CMOS (Complementary Metal Oxide Semiconductor) technology. The chip consists of 4 x 4 POSFET touch sensing devices (or taxels) and both, the individual taxels and the array are designed to match spatio–temporal performance of the human fingertips. To detect contact events, the taxels utilize the contact forces induced change in the polarization level of piezoelectric polymer (and hence change in the induced channel current of MOS). The POSFET device on the chip have linear response in the tested dynamic contact forces range of 0.01–3 N and the sensitivity (without amplification) is 102.4 mV/N

Enhanced Triboelectric Nanogenerator Performance via an Optimised Low Permittivity, Low Thickness Substrate

With electrical power generated from mechanical contact, the triboelectric nanogenerators (TEN Gs) have attracted attention recently as a promising route to realising self-powered sensors (e.g. tactile sensors, biomedical sensors etc.). Due to their limited power range (0.1-100 mW/cm 2 ), it is important to optimise the output performance of TENGs. Among the factors that confer higher performance are materials with a strong triboelectric effect and materials with low permittivity. It can be difficult to realize these two benefits in a single contact material. This paper presents a solution to this challenge by optimising a low permittivity substrate beneath the tribo-contact layer. Results are simulated over a range of both substrate permittivity and thickness. The open circuit voltage is found to increase by a factor of 1.8 in moving from PVDF to the lower permittivity PTFE and by a further factor of 37.2 when the substrate thickness is reduced from 200 to \pmb1 μm. For PTFE with \pmb1 μm thickness, this amounts to 12.2 kV, as against 327V known from simulations up to now. These results clearly indicate that optimized low permittivity, low thickness substrates represent a potential route to self-powered sensors

Epidermial electronics: flexible electronics for biomedical applications

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