Robot Skin Research Articles

Highly Soft Viscoelastic Robot Skin With a Contact Object-Location-Sensing Capability

This paper concerns the development of robot skin capable of accurately sensing the location of objects in area contact with the skin surface. There has been no report on tactile sensing which attained not only skin deformation detection but also contact object location sensing with high accuracy. In the category of optomechatronics technology, we apply optical fibers to transmit surface deformation information of soft skin for sensing the location of an object in contact with the soft skin accurately. In the paper, we illustrate the structure of the robot skin, and describe the principle of both detecting the position of the reflector chips and sensing the contact location of an object. The robot skin is characterized by the fact that the surface is low cost and easily replaceable, and the sensing performance is robust against any electromagnetic disturbance. We then show experimental results for verifying the principles using a wedge-shaped object. For evaluating the sensing accuracy, comparisons are made: 1) between the location of a real convex of the object and that of the corresponding estimated polygon and 2) for the position of two vertices of the object when independent fitting and Lagrangian fitting methods are applied.

2P2-I03 二次元通信層を利用する触覚センシング

大面積のロボット表面を被覆する方法として, 誘導結合を利用する無線触覚素子とその実装方法が提案されているが, この方法では電力消費が大きく, 他のセンサや通信に対しノイズ源ともなり得るものであった。そこで本研究では皮膚内部に二次元的に広がる導電層によって信号を伝達する新しい人工皮膚を提案する。本方式によれば, 従来の無線触覚素子の素子配置の自由度をわずかに失うだけで前述の問題が解決され, 素子配置の高密度化も容易である。また, 提案する素子においては微小素子内部で計測された応力3成分を符号化して送信するため, 10ビット程度の測定レンジが容易に得られると考えられる。ここではその構造, 基本原理と現在までの基礎実験結果を述べる。

SA‐I Mechanoreceptor Position in Fingertip Skin May Impact Sensitivity to Edge Stimuli

Background: The skin plays a role in conditioning mechanical indentation into distributions of stress/strain that mechanoreceptors convert into neural signals. Solid mechanics methods have modelled the skin to predict the in vivo neural response from mechanoreceptors. Despite their promise, current models cannot explain the role that anatomical positioning and receptor organ morphology play in producing differences in neural response. This work hypothesises that the skin′s intermediate ridges may help explain, in part, the sensitivity of slowly adapting type I (SA‐I) mechanoreceptors to edge stimuli. Method: Two finite‐element models of the fingertip were built, validated and used to analyse the functionality of the intermediate ridges. One of the two‐dimensional, cross‐sectional models included intermediate ridges, while the other did not. The analysis sought to determine if intermediate ridges (1) increase the magnitude of strain energy density (SED) near the SA‐I location and (2) help differentiate one 2.0‐mm indenter from two 0.5‐mm wide indenters with a 1.0‐mm gap. Results: Higher concentrations of SED were found near the tips of the intermediate ridges, the anatomical location that coincides with the SA‐I receptors. This first result suggested that the location of the SA‐Is in the stiffer epidermal tissue helps magnify their response to edge stimuli. The second result was that both models were equally capable of predicting the spatial structure within the in vivo neural responses, and therefore the addition of intermediate ridges did not help in differentiating the indenters. Conclusion: The finding, a 15%–35% increase in response when the sampling point lies within the stiffer tissue at the same depth, seeks to inform the positioning of force sensors in robotic skin substrates.

An arbitrarily distributed tactile piezoelectric sensor array

This paper introduces a new principle and real structure of a non-scanning, fast response, arbitrarily distributed tactile sensor array using a piezoelectric resonator, and its application as a force/pressure sensor array. The piezoelectric sensor has a high mechanical quality factor and stability, and the quasidigital output can be measured easily and precisely. The sensory method in the array is non-scanning; the sensory position can be measured precisely and speedily. Because of the softness of the piezoelectric film, a tactile sensor array using piezoelectric film can be used for the sensitive skin of an intelligent robot.

Smart sensor networks for robotic sensor skins

Data acquisition and data fusion of large numbers of sensors present unique challenges for control systems designers and applications engineers alike. In recent years the sensors industry has been moving towards the use of smart sensors, fieldbus networks, and localized smart processes. Merritt Systems Inc. of Rockledge, Florida, has been in the forefront of these developments since 1987 when it started pursuing the development of large sensor networks for robotic obstacle avoidance. As a result of this work a number of unique smart sensors and network technologies have been developed which have a wide range of applications beyond robotics. These include: one of industry’s first smart sensors, smart sensor networks, PC‐based data acquisition and control systems, and novel robotic modelling and motion planning algorithms. Whenever large networks of sensors with mixed sensing media are used, this technology has far‐reaching applications to industry and the research community.

Tactile shear sensing using anisotropically conductive polymer

A new technique for tactile shear sensing using a z-direction-only conductive polymer material is discussed. A thin layer of the material is in situ cured, in the presence of a z-direction magnetic field, on the surface of a circuit board containing a contact-pad array. A small metallic cursor embedded in an overlaid elastomeric skin slides over the z-direction conductive polymer upon shear motion, and its change in position is detected by the occurrence of simple circuit connections between neighboring contact pads. This shear sensor has the advantages of being compliant, transparent, able to accommodate pad height variations, and capable of high-resolution sensing. It may also serve as temperature and pressure sensor because of the characteristic and reversible variation of the z-direction electrical resistance in the conductive polymer upon changes in ambient temperature and contact pressure. The new sensor may be useful for potential applications such as touch-sensitive controllers for computer-related products and robotic skins.