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.     

A Polymer-Based Flexible Tactile Sensor for Both Normal and Shear Load Detections and Its Application for Robotics

This paper proposes and demonstrates a novel flexible tactile sensor for both normal and shear load detections. For the realization of the sensor, polyimide and polydimethylsiloxane are used as a substrate, which makes it flexible. Thin metal strain gauges, which are incorporated into the polymer, are used for measuring normal and shear loads. The salient feature of this tactile sensor is that it has no diaphragm-like structures. The unit tactile cell characteristics are evaluated against normal and shear loads. The fabricated tactile sensor can measure normal loads of up to 4 N, and the sensor output signals are saturated against loads of more than 4 N. Shear loads can be detected by different voltage drops in strain gauges. The device has no fragile structures; therefore, it can be used as a ground reaction force (GRF) sensor for balance control in humanoid robots. Four tactile unit sensors are assembled and placed in the four corners of the robots sole. By increasing bump dimensions, the tactile unit sensor can measure loads of up to 2 kgf. When loads are exerted on the sole, the GRF can be measured by these four sensors. The measured forces can be used in the balance control of biped locomotion systems.     

Design and fabrication of a hybrid silicon three-axial force sensor for biomechanical applications

This paper presents the design and development of a silicon-based three-axial force sensor to be used in a flexible smart interface for biomechanical measurements. Normal and shear forces are detected by combining responses from four piezoresistors obtained by ion implantation in a high aspect-ratio cross-shape flexible element equipped with a 525 μm high silicon mesa. The mesa is obtained by a subtractive dry etching process of the whole handle layer of an SOI wafer. Piezoresistor size ranges between 6 and 10 μm in width, and between 30 and 50 μm in length. The sensor configuration follows a hybrid integration approach for interconnection and for future electronic circuitry system integration. The sensor ability to measure both normal and shear forces with high linearity (99%) and low hysteresis is demonstrated by means of tests performed by applying forces from 0 to 2 N. In this paper the packaging design is also presented and materials for flexible sensor array preliminary assembly are described.     

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.     

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.     

基于FBG的机器人柔性触觉传感器

为了满足机器人与外界环境、对象发生接触及交互作用时的触觉感知需求,提出了一种基于光纤布拉格光栅（FBG）的柔性触觉传感器．该传感器采用3×3 FBG阵列作为柔性传感元件,聚二甲基硅氧烷（PDMS）材料构成双层柔性基体．介绍了传感器的传感原理并采用有限元方法对其弹性体进行力学仿真分析,基于标定实验平台完成该传感器的静态标定实验．传感器的空间分辨率为25mm,在10mm×10mm载荷施加单元下,对力的感知范围为0～7N,且传感器具有较好的线性度和灵敏度,重复性和一致性良好,力灵敏度为0.16nm/N．实验结果和分析研究都证明了柔性触觉传感器的可行性．该传感器与人体皮肤触感及结构极为相似,且布线简单、抗干扰能力强．     

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.     

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。     

High precision intelligent flexible grasping front-end with CMOS interface for robots application用于智能机器人精细抓握的高灵敏度柔性抓握前端

This paper presents a high-precision intelligent flexible robot grasping front-end with an integrated capacitive tactile sensor array and a conditioning chip. The capacitive tactile sensor is the primary part of the front-end, it determines the overall performance. The micro-needle array sandwich structure in the tactile sensor increases the repeatability and stability, and ensures the sensitivity. The assembled sensor exhibits a saturation at 10.53 N (421 kPa) with a sensitivity of 1.9%/kPa. Furthermore, a conditioning chip is utilized in a custom readout interface to achieve better performance by reducing signal attenuation, and to increase the compatibility of the front-end. The chip is optimized for the parasitic shunt capacitance in the capacitor array. A dual bidirectional charge-discharge conversion method and a two-port detection method are matched to achieve the goal of reducing the shunting influence, and attenuating the offset voltage or the noise input effects. A prototype of the interface has been fabricated using 180-nm CMOS technology. Sensor with the value of 0.5 pF shunted by capacitors of 47 pF has been detected with an error of 1% within 100 μs.     

A flexible three-axial capacitive tactile sensor with multilayered dielectric for artificial skin applications

In this paper, a new flexible three-axial force sensor was designed and investigated, which was composed of four capacitors, and the mechanism was based on the capacitance change induced by an applying three-axial force. For the configuration of the electrodes, four sensing electrodes and a public electrode were in the same plane, which was based on fringe effect theory. Different from the traditional dielectric layer with single material, this multilayered dielectric consisted of both the air gap and polydimethylsiloxane. The structure of the multilayered dielectric changed under the external/applied force, leading to variation of dielectric constant ε, which caused the capacitance change. Measurement results showed that the full-scale range of detectable force was around 0–10 N for all three axes. The average sensitivities of the force sensor units were 0.0095, 0.0053, and 0.0060 N⁻¹ for the normal, X-axis, and Y-axis shear forces, and more test proved its high potential for application in skin-like sensing field.

     

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.     

进化算法与基于同伦理论算法在多维触觉阵列传感器解耦应用中的对比

为获取大规模多维柔性触觉阵列传感器触觉信息,比较进化算法与基于同伦理论的算法在传感器解耦中的应用.仿真结果表明对一定规模的阵列传感器来说,进化算法解耦效果优于其它人工智能算法,但对大规模阵列传感器则无法满足实时性和准确性.通过引入时间参数,基于同伦理论的解耦算法将传统的传感器静态解耦转换成动态解耦过程.算法不仅适用于大规模阵列触觉传感器的信息解耦,而且解决高维、多参数传感器信息精确、实时解耦的难题.     

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。     

Object imaging with a piezoelectric robotic tactile sensor

A two-dimensional, electrically multiplexed robotic tactile sensor was realized by coupling a piezoelectric polyvinylidene fluoride (PVDF) polymer film to a monolithic silicon integrated circuit (IC). The IC incorporates 64 sensor electrodes arranged in a symmetrical 8×8 matrix. Each electrode occupies a 400×400 μm square area, and they are separated from each other by 300 μm. A 40-μm-thick piezoelectric PVDF polymer film was attached to the electrode array with an electrically nonconductive methane adhesive. The response of the tactile sensor is linear for loads spanning 0.8-135 grams-of-force (gmf) (0.00-1.35 Newtons (N)). The response bandwidth is 25 Hz, the hysteresis level is tolerable, and, for operation in the sensor's linear range, taxel crosstalk is negligible. The historically persistent stability and response reproducibility limitation associated with piezoelectric-based tactile sensors has been solved by implementing a novel pre-charge voltage bias technique to initialize the pre- and post-load sensor responses. A rudimentary tactile object image measurement procedure for applied loads has been devised to recognize the silhouette of a sharp edge, square, trapezoid, isosceles triangle, circle, toroid, slotted screw, and cross-slotted screw     

一种基于导电橡胶的三维力柔性触觉传感器阵列机理与仿真研究

根据接触力学理论和导电橡胶的电阻应变关系,对一种基于压敏导电橡胶的三维力柔性触觉传感器阵列的传感机理进行深入的探索,并应用静电比拟法导出传感器节点间电阻与表面应力激励的关系,建立了传感器阵列表面三维力激励与输出电阻的物理模型。以此为基础对传感器输入输出特性进行了仿真,并基于仿真结果对传感器结构进行优化。仿真结果验证了该传感器结构设计的合理性。     

Design and microfabrication of a flexible oral electrotactile display

A polyimide-based flexible oral tactile display with an array of 7/spl times/7 tactors is designed for presentation of electrotactile patterns onto the roof of the mouth. The device is microfabricated on a rigid substrate using thin-film and electroplating processes and then released by peeling it off from the substrate. Dome-shaped tactors are electroplated through round openings 300 /spl mu/m in diameter in the flexible polyimide base for more uniform current distribution and better contact with the skin. The overall dimensions of the tactor array are 18.5/spl times/18.5 mm/sup 2/, with a center-to-center spacing of 2.54 mm between adjacent tactors. Each tactor is 200 /spl mu/m in height and 700 /spl mu/m in diameter. The device robustness is improved by using a grid-pattern design for the openings to overcome the stress mismatch between the rigid tactors and the flexible base. The flexible oral tactile display has been tested in human subject experiments and found to deliver comfortable electrotactile stimulation with relatively low stimulation intensities.     

Characterization of a capacitive tactile shear sensor for application in robotic and upper limb prostheses

This paper presents the characterization of a novel tactile sensor designed to measure shear forces. The sensor design is targeted for use in robotic and prosthetic hands, where haptic feedback or ability to detect shear forces associated with slip are critical. The presented sensor utilizes the principle of differential capacitance to measure the mechanical deflection of the sensor element. The dynamic range of the sensor can be varied by encapsulating the sensor terminal within silicone of varying hardness. The design features ease of mass production, low per-unit-cost, novel overload protection and low wire count, while still preserving the ability to achieve reasonable spatial resolutions and array densities. Mathematical and COMSOL multiphysics models of the sensor are presented, in addition to results from practical experiments. Sensors with a full scale displacement range of ±0.525 mm were produced and the differential capacitance was measured. Shear force transduction was characterized over the range of 0 N–4 N with the sense terminal encapsulated by silicone with a shore A hardness of 20. The effect of elastomer hardness on the sensor's dynamic range was analyzed. The differential capacitance, when measured at each fixed interval, was found experimentally to have a maximum standard deviation of 4.28e?16 F over a ±2 N range. A maximum standard deviation of 1.35e?15 F was measured across characterized full scale sensor range of ±4 N. The sensor design has a sensitivity of 1.967 fF/N of applied force and the sensor output was found to be approximately linear. The coefficient of determination, r², was found to be 0.941.     

新型智能机器人触觉传感服装阵列标定的研究

为使智能机器人在汽车冲撞试验中获得准确的触觉信息,研发了一种基于导电橡胶压阻特性的新型触觉传感服装阵列.针对该传感阵列设计了静态标定试验装置,在常温下(25℃)研究了不同型号的导电橡胶( N05,N10,N15)的压阻行为特性,选出压敏性最佳的N10作为触觉传感服装的敏感元件;在此基础上提出了标定方案,标定结果表明:高...     

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。     

基于导电橡胶的一种新型类皮肤触觉传感器阵列的研究

本文设计了一种基于导电橡胶的类皮肤柔性触觉传感器阵列,传感器阵列采用交叉排列的两层节点的框架结构,用注射成型(LIMS)的方法进行导电橡胶的整体浇注,通过测量外力作用下导电橡胶的阻值变化,求解出加载在柔性传感器表面上的三维力位置和大小。该设计突破了当前基于盔甲的柔性触觉传感器的设计思路,具有优良力学特性、柔韧性好、抗干扰能力强、在传感器表面可以连续点测量的特性。实验仿真结果表明,在理想导电橡胶的条件下,设计的柔性触觉传感器阵列测量三维力有较高的分辨率和精度,可以满足当前用于作机器人皮肤的需要。