Development of a flexible three-axial tactile sensor array for a robotic finger

In this paper, we propose a flexible three-axial tactile sensor array for measuring both normal and shear loads. The sensor array has 16 tactile sensor units based on piezoresistive strain gauge. It is constructed on a Kapton polyimide film using advanced polymer micromachining technologies. Thin metal strain gauges are embedded in polyimide to measure normal and shear loads, which are tested by applying forces from 0 to 1?N. The developed sensor unit had a hysteresis error of about 9% and repeatability error of about 1.31%. The sensor showed a good resulting image when pressed by a circle-shaped object with 10?N loads. The proposed flexible three-axial tactile sensor array can be applied in a curved or compliant surface that requires slip detection and flexibility, such as a robotic finger.     

Design and fabrication of a flexible three-axial tactile sensor array based on polyimide micromachining

This paper describes the design and fabrication of a flexible three-axial tactile sensor array using advanced polyimide micromachining technologies. The tactile sensor array is comprised of sixteen micro force sensors and it measures 13 mm × 18 mm. Each micro force sensor has a square membrane and four strain gauges, and its force capacity is 0.6 N in the three-axial directions. The optimal positions of the strain gauges are determined by the strain distribution obtained form finite element analysis (FEA). The normal and shear forces are detected by combining responses from four thin-film metal strain gauges embedded in a polyimide membrane. In order to acquire force signals from individual micro force sensors, we fabricated a PCB based on a multiplexer, operational amplifier and microprocessor with CAN network function. The sensor array is tested from the evaluation system with a three-component load cell. The developed sensor array can be applied in robots’ fingertips, as well as to other electronic applications with three-axial force measurement and flexibility keyword requirements.     

Detection and prevention of slip using sensors with different properties embedded in elastic artificial skin on the basis of previous experience

In dexterous robotic manipulation, it is essential to control the force exerted by the robot hands while grasping. This paper describes a method by which robot hands can be controlled on the basis of previous experience of slippage of objects held by the hand. We developed an anthropomorphic human scale robot hand equipped with an elastic skin in which two types of sensor are randomly embedded. One of these sensors is a piezoelectric polyvinylidenefluoride (PVDF) film which can be used for the detection of pressure changes. The other is a strain gauge which can measure static pressure. In our system, PVDF films are used to detect slipping, and strain gauges to measure stresses which are caused by normal and shear forces. The stress measured by the strain gauges is used as input data to a neural network which controls the actuators of the robot. Once slip is detected, the neural network is updated to prevent it. We show that this system can control the grasp force of the robot hand and adapt it to the weight of the object. By using this method, it was shown that robots can hold objects safely.     

压阻式触觉传感器对法向力和剪切力的检测

灵活的触觉传感器应该具有像皮肤一样的功能,能够检测施加力的大小和方向.改进的压阻式触觉传感器,主要由中心芯和4个侧壁组成,法向力和剪切力的感测元件不同.将压阻式触觉传感器嵌入到一个聚二甲基硅氧烷(PDMS)弹性体中,以实现力的柔性检测.通过仿真分析,得到此种触觉传感器对法向力的检测范围为600 Pa~65 kPa,可测得的最小剪切力为900 Pa.通过进一步分析,得到施加法向力和剪切力时法向力感测元件阻值的变化曲线,可得此种触觉传感器能够有效降低法向力感测元件与剪切力感测元件之间的干扰.所开发的触觉传感器可以灵活检测施加的法向力和剪切力,可应用于机器人手臂和假肢上.     

一种新型机器人三维力柔性触觉传感器的设计

基于柔性力敏导电橡胶材料,设计了一种能测量三维力的新型机器人柔性触觉传感器。研究了力敏导电橡胶材料的压阻效应,阐述了触觉传感器的设计思想,分别进行了触觉传感器单元设计和阵列结构设计和研究。获得了计算三维力的数学模型,并通过实验进行了三维力的验证。结果表明,设计的机器人三维力柔性触觉传感器具有设计简单,造价低廉,柔顺性好等优点,而且布置成阵列结构可用于医疗、体育、机器人等领域中检测三维力信息。     

Fabrication and performance assessment of a novel stress sensor applied for micro-robotics

An innovative tactile sensor is analyzed and verified by intensive experiments. By using micro-cantilever beams, on which the strain gauge layers (Pt/Ti) are deposited, the corresponding induced strains can be detected and converted into electric resistance change, with respect to either applied normal stress or shear stress. The four micro-cantilever beams are allocated in the fashion such that any adjacent beams are perpendicular to each other to decouple any potential measure discrepancy due to non-ideal orthogonality. In addition, the micro-cantilever beams are curled before hands so that they can concurrently detect normal stress and shear stress. To be protected from being damaged by strong stress, the curled cantilever beams are covered up by elastomer material. Therefore, the micro-tactile sensor can detect normal stress up to 250 kPa and shear stress up to 35 kPa. Besides, since the elastomer is made of PDMS, which is of high bio-compatibility, the tactile sensor can be used to directly contact with human body. By taking the design and fabrication parameters into account, the curled micro-cantilever beams, which is of multi-layer structure by polymer/Pt/Ti/Si, can be produced with high yield rate. Finally, the efficacy of the tactile sensor is verified by experiments via a micro-manipulator, a high-resolution microscope and a force sensor for calibration.     

移动机器人非视觉传感器及其信号处理方法

非视觉传感器是机器人认识和了解外部环境的重要途径，移动机器人常用的非视觉 传感器包括超声、红外、接近传感器等．这些传感器大多是以环或阵列的形式出现，因此其 信号处理往往要占用机器人大量的CPU时间．本文提出了一种采用多DSP控制和处理各类非视 觉传感器的方法，给出了传感器信号处理的原理和具体实现．同时我们引入了并行处理的机 制，各类传感器信号处理可同时进行，在很大程度上提高了机器人传感器信号处理的速度， 有利于机器人在实时动态环境中运行．并给出了非视觉传感器信号处理的实验结果，验证了 该方法的有效性．      

柔性触觉传感技术及其在医疗康复机器人的应用

柔性触觉传感器易于贴合皮肤等不规则表面,相比刚性传感器具有更强的信号感知能力、更高的精度和更佳的穿戴舒适性,在人机交互、医疗设备、可穿戴设备、健康监测等领域发挥着重要作用.鉴于此,从传感器不同工作原理出发,对柔性触觉传感器进行系统地介绍和对比,从结构优化的角度分析传感器性能优化方法,整理出微结构、结构疏松化、多模态测量...     

Parylene surface-micromachined membranes for sensor applications

This paper reports the design, fabrication process, and testing results of Parylene surface-micromachined membranes with integrated strain gauges or thermal resistors made of thin film metals. The membrane is suspended above the substrate. This paper demonstrates the feasibility of sensor applications with a force (tactile) sensor and a fluid shear stress sensor.     

Experimental Testing of a Gauge Based Collision Detection Mechanism for a New Three‐Degree‐of‐Freedom Flexible Robot

The use of flexible robots can be easily justified in two main cases: (1) when the weight of the robot has to be minimized and (2) when collisions between the robot and the environment are foreseen, since a flexible, lightweight robot implies less impact energy. The position control of these robots has already been analyzed in previous communications. However, the second of these cases justifying the use of flexible robots requires further consideration, leading to the development of a force controller. Inmost up to date analysis the force control is studied beginning from a known contact point at a given collision time. In a more realistic approach, however, an accurate detection of the collision would be needed prior to dealing with the force control. After developing a reliable position controller for a three‐degree‐of‐freedom flexible robot using strain gauges placed over the robot structure, in this paper we deal with the possibility of carrying out the collision detection for the same prototype. This has been easily achieved by analyzing some estimated signals such as tip position and tip velocity. However, a complete analysis of the information obtained with the sensors has been required to obtain those estimates and a signal processing scheme had to be devised for a previous filtering of the original signals from the sensors (encoders and strain gauges). This work has been carried out as a first step towards the position/force control. Experimental results on a three‐degree‐of‐freedom flexible arm prototype are presented to verify how well this method performs. © 2003 Wiley Periodicals, Inc.     

一种柔性三维力触觉传感器阵列的实现方法

介绍了一种可安装在曲面上,对三维力进行检测的柔性三维力触觉传感器阵列的实现方法.首先采用MEMS技术制备三维力触觉传感器阵列,再将多个三维力触觉传感器单元分别通过倒装焊技术集成在已加工好的柔性电路板基底上,实现了传感器与信号处理电路的互连和传感器阵列(4×4)的柔性化.采用信号选通的多路信号采集方法简化了传感器阵列的信号处理电路.测试结果表明,柔性触觉传感器阵列可弯曲变形90°以上,检测三维力的分辨率达到0.1 N.     

Development of soft and distributed tactile sensors and the application to a humanoid robot

This paper describes a comprehensive tactile sensor system which can cover wide areas of full-body robots. Based on design criteria which are introduced from requirements, we develop two types of tactile sensor elements. One is a multi-valued touch sensor which has multi-level pressure thresholds. It is capable of covering wide areas of robot surfaces. The other is made of soft, conductive gel, which has the advantage of compliance compared with other sheet-type tactile sensors. With these two types sensors, we develop the tactile sensor system on the full-body robot 'H4'. Details of the sensor system on the robot and some experiments using tactile information are described.     

中国微米纳米-基于混合频率激励的新型公共电极式电容触觉传感阵列设计

本文设计了一种基于混合频率激励的三自由度柔性电容触觉传感阵列。每个传感单元中由传感电极层上的四片传感电极和公共电极层上的一片公共电极构成四个电容传感子单元,当四个电容传感子单元按正方形排列时,所测得的接触力将被分解为一组正向压力和两组剪切力分量。信号采样采用混合频率激励的方法替代单频激励,四片传感电极分为激励端和输出端,激励端加载频率分别为f1和f2的两组电压信号Ui1和Ui2,输出端的两组信号通过带通滤波器可提取四组谐波分量,从而实现四个电容传感子单元的电容量测量。该方法简化了信号采样机构,有效实现多维触觉信息的同步检测与分离。每个传感单元在z轴方向的正向压力测试灵敏度为0.17%/mN,x-y轴方向的灵敏度为0.43%/mN。结果表明该触觉传感阵列是一种有价值的可实现低成本触觉传感的新型测量装置。     

基于新型多模态触觉传感器的机器人交互物体分类

多模态传感融合对于机器人探索外界环境十分重要,而现有的触觉传感器只能收集一种触觉模态信息,其收集到的多模态信息存在弱配对问题,为了解决此问题,研究了一种基于触觉和视觉融合的多模态触觉传感器。该传感器可以利用一个感知层同时收集2种异构触觉模态信息,弥补了传统触觉传感器的缺陷,同时可以利用收集到的多模态信息对不同物体的几何形状进行分类,在研究过程中,通过按压实验收集了圆形、正方形、长方形和三角形4种形状物体的触觉信息,再利用K最近邻(KNN)算法进行几何形状分类,实验结果证明了该传感器在区分不同物体的形状上具有良好的效果。     

多功能传感器

多功能传感器可以同时测量几个物理量。简述多功能传感器的结构,并介绍了模拟人体皮肤的触觉传感器及其它几种多功能传感器。     

A contact-type piezoresistive micro-shear stress sensor forabove-knee prosthesis application

A prototype contact-type micro piezoresistive shear-stress sensor that can be utilized to measure the shear stress between skin of stump and socket of above-knee (AK) prosthesis was designed, fabricated and tested. Micro-electro-mechanical system (MEMS) technology has been chosen for the design because of the low cost, small size and adaptability to this application. In this paper, the finite element method (FEM) package ANSYS has been employed for the stress analysis of the micro shear-stress sensors. The sensors contain two transducers that will transform the stresses into an output voltage. In the developed sensor, a 3000×3000×300 μm³ square membrane is formed by bulk micromachining of an n-type (100) monolithic silicon. The piezoresistive strain gauges were implanted with boron ions with a dose of 10¹⁵ atoms/cm². Static characteristics of the shear sensor were determined through a series of calibration tests. The fabricated sensor exhibits a sensitivity of 0.13 mV/mA-MPa for a 1.4 N full scales shear force range and the overall mean hysteresis error is than 3.5%. In addition, the results simulated by FEM are validated by comparison with experimental investigations     

A flexible-arm as manipulator position and force detection unit

This paper presents a self-sensory robot arm to two basic sensing problems in control of flexible manipulators: detection of the position and orientation variations due to structural deformation and detection of the contact force of end-effector when manipulator interacts with its environment. Taking advantage of structural flexibility, a flexible robot arm with strain gauges distributed on it acts as a sensing unit. The position and orientation of flexible arm are expressed as a function of curvature of the arm. An interpolation technique gives this continuous curvature function from a finite set of measurements made with strain gauges. A relation between strain measurements and endpoint force of flexible arm is developed and the contact force of end-effector is then determined using a force propagation algorithm. The proposed technique and algorithm were implemented and evaluated in a laboratorial flexible arm. Experimental validations using a vision system and two force sensors have shown that the self-sensory flexible arm can provide accurate endpoint position and force in both static and dynamic loading situations.     

基于PI衬底的柔性MEMS电容式触觉力传感器设计与制作

论述了一种可应用于机器人或医学修补技术的触觉传感器及其在旋涂的柔性聚酰亚胺衬底的新制作方法.该传感器是由多层无机和有机薄膜组成的柔性薄膜结构.结合传感器结构特点及各结构层材料的加工性能,进行工艺优化整合.尤其首次在载体硅片与PI衬底之间引进PDMS分离层,使得柔性器件的分离工艺大大简化.最后得到一种简单、低廉且与常规MEMS技术兼容的工艺.所制的传感器结构轻薄,可挠性好,且能贴附在任意形状的物体表面同时实现法向力和切向力的测量.     

Recent progress in tactile sensing and sensors for robotic manipulation: can we turn tactile sensing into vision?1

This paper surveys recently published literature on tactile sensing in robotic manipulation to understand effective strategies for using tactile sensing and the issues involved in tactile sensing. It consists of a brief review of existing tactile sensors for robotic grippers and hands, review of modalities available from tactile sensing, review of the applications of tactile sensing in robotic manipulations, and discussion of the issues of tactile sensing and an approach to make tactile sensors more useful. We emphasize vision-based tactile sensing because of its potential to be a good tactile sensor for robots.     

导电橡胶触觉传感器阵列的标定实验研究

导电橡胶传感器是智能机器人服装的核心机件;标定出导电橡胶传感器的压阻特性是实现智能机器人触觉传感服装的核心内容之一;实验中,将导电橡胶安装在柔性阵列电极板里制作成触觉传感器阵列服装。对该传感器提出多种测量方法,确立其标定模型;给出数据建模的一般步骤。指出导电橡胶传感器设计的改进方向与部分方法。