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.     

Electrostatic tactile display with thin film slider and its application to tactile telepresentation systems

A new electrostatic tactile display is proposed to realize compact tactile display devices that can be incorporated with virtual reality systems. The tactile display of this study consists of a thin conductive film slider with stator electrodes that excite electrostatic forces. Users of the device experience tactile texture sensations by moving the slider with their fingers. The display operates by applying two-phase cyclic voltage patterns to the electrodes. The display is incorporated into a tactile telepresentation system to realize explorations of remote surface textures with real-time tactile feedback. In the system, a PVDF tactile sensor and a DSP controller automatically generate voltage patterns to present surface texture sensations through the tactile display. A sensor, in synchronization with finger motion on the tactile display, scans a texture sample and outputs information about the sample surface. The information is processed by a DSP and fed back to the tactile display in real time. The tactile telepresentation system was evaluated in texture discrimination tests and demonstrated a 79 percent correct answer ratio. A transparent electrostatic tactile display is also reported in which the tactile display is combined with an LCD to realize a visual-tactile integrated display system.     

Remote Tactile Transmission with Time Delay for Robotic Master–Slave Systems

This study develops a method to compensate for the communication time delay for tactile transmission systems. For transmitting tactile information from remote sites, the communication time delay degrades the validity of feedback. However, so far time delay compensation methods for tactile transmissions have yet to be proposed. For visual or force feedback systems, local models of remote environments were adopted for compensating the communication delay. The local models cancel the perceived time delay in sensory feedback signals by synchronizing them with the users' operating movements. The objectives of this study are to extend the idea of the local model to tactile feedback systems and develop a system that delivers tactile roughness of textures from remote environments to the users of the system. The local model for tactile roughness is designed to reproduce the characteristic cutaneous deformations, including vibratory frequencies and amplitudes, similar to those that occur when a human finger scans rough textures. Physical properties in the local model are updated in real-time by a tactile sensor installed on the slave-side robot. Experiments to deliver the perceived roughness of textures were performed using the developed system. The results showed that the developed system can deliver the perceived roughness of textures. When the communication time delay was simulated, it was confirmed that the developed system eliminated the time delay perceived by the operators. This study concludes that the developed local model is effective for remote tactile transmissions.     

Reconstruction of surface texture based on spatial information measured with a pen-type texture sensor

Surface texture is one of the important properties for the human to identify objects by touch. Effective reconstructions of textures are necessary for realistic interactions between the human and environment via human–computer interfaces. This paper presents a systematic approach for sensing and reconstructing periodic surface textures. Three significant issues are discussed: a pen-type texture sensor that measures the spatial information based on the measurements of contact forces; an algorithm for the reconstruction of periodic textures based on the obtained spatial information; and the method of incremental scanning to identify the polar spectrum of a surface by limited number of scans. The concept of polar spectrum is introduced to describe the spatial properties of the surface, that is, the relation between spatial frequencies and the direction of measurement. The pattern of polar spectrum is used to facilitate surface reconstructions. Experimental results based on the spatial information obtained with a laser displacement sensor and the pen-type texture sensor demonstrate the effectiveness of the proposed methods for the measurement and reconstruction of periodic textures.     

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...     

Development of a High-Resolution Human-Specific Breath Gas Sensor for Survivor Detection in Disaster Zones

This paper presents a new type of ultrasonic gas molecule concentration sensor for rescue robotics. This device can measure the change of gas concentration with a sampling rate of over 400 kHz. The performance is evaluated by measuring the CO₂ concentration in human respiration gas. The experiments show that the proposed sensor could detect a difference between 5% CO₂-containing air, humidified air and dry air with over 50 dB signal-to-noise, which are the main components of our respiration gas. Another important result was that our sensor could give information about the 'dead space', which is distributed from the lungs to the mouth. The 'dead space' could not be detected by previously proposed commercially distributed gas sensors because of the time needed to analyze the gas. We verified the distance dependency of the respiration detection in a open space that was considered for use for finding survivors. These results make the proposed sensor especially applicable for finding survivors in disaster zones.     

PVDF-Based Microfabricated Tactile Sensor for Minimally Invasive Surgery

This paper aimed to develop a miniaturized tactile sensor capable of measuring force and force position in minimally invasive surgery. The in situ measurement of tactile information is a step forward toward restoring the loss of the sense of touch that has occurred due to shift from traditional to minimally invasive surgeries. The sensor was designed such that it can sense low forces which could be comparable to those produced by pulsating delicate arteries, yet can withstand high forces comparable to grasping forces. The influence of some hidden anatomical features, such as lumps, voids, and arteries, on the stress distribution at the grasping surface was studied. In this paper, the capability of the sensor to determine and locate any point load was also investigated. The proposed sensor was designed and manufactured to be highly sensitive, using polyvinylidene fluoride (PVDF). The microfabrication procedure of the sensor, including corner compensation for toothlike projections and patterning of PVDF film, was discussed. The micromachined sensor was tested, and the experimental results were compared with the results of 3-D finite element modeling. $hfill$[2007-0286]      

Realizing whole-body tactile interactions with a self-organizing,multi-modal artificial skin on a humanoid robot

In this paper, we present a new approach to realize whole-body tactile interactions with a self-organizing, multi-modal artificial skin on a humanoid robot. We, therefore, equipped the whole upper body of the humanoid HRP-2 with various patches of CellulARSkin – a modular artificial skin. In order to automatically handle a potentially high number of tactile sensor cells and motors units, the robot uses open-loop exploration motions, and distributed accelerometers in the artificial skin cells, to acquire its self-centered sensory-motor knowledge. This body self-knowledge is then utilized to transfer multi-modal tactile stimulations into reactive body motions. Tactile events provide feedback on changes of contact on the whole-body surface. We demonstrate the feasibility of our approach on a humanoid, here HRP-2, grasping large and unknown objects only via tactile feedback. Kinesthetically taught grasping trajectories, are reactively adapted to the size and stiffness of different test objects. Our paper contributes the first realization of a self-organizing tactile sensor-behavior mapping on a full-sized humanoid robot, enabling a position controlled robot to compliantly handle objects.     

A sensor for dynamic tactile information with applications in human–robot interaction and object exploration

We present a novel tactile sensor, which is applied for dextrous grasping with a simple robot gripper. The hardware novelty consists of an array of capacitive sensors, which couple to the object by means of little brushes of fibers. These sensor elements are very sensitive (with a threshold of about 5 mN) but robust enough not to be damaged during grasping. They yield two types of dynamical tactile information corresponding roughly to two types of tactile sensor in the human skin. The complete sensor consists of a foil-based static force sensor, which yields the total force and the center of the two-dimensional force distribution and is surrounded by an array of the dynamical sensor elements. One such sensor has been mounted on each of the two gripper jaws of our humanoid robot and equipped with the necessary read-out electronics and a CAN bus interface. We describe applications to guiding a robot arm on a desired trajectory with negligible force, reflective grip improvement, and tactile exploration of objects to create a shape representation and find stable grips, which are applied autonomously on the basis of visual recognition.     

Development of a sensor system for collecting tactile information

This paper presents the development of a sensor system for collecting tactile information. An active sensing system using the piezoelectric effect and the pyroelectric effect of a PVDF (Polyvinylidene fluoride) film is proposed. The active sensing is designed with human motions for tactile perception in mind. First, as the pretest, the distinction examination of six fabrics with different textures is carried out through human tactile perception. Next, the proposed sensor system is assembled. The sensor is composed of a PVDF film and a soft rubber. The surface of the sensor can be heated through temperature control. The sensor is attached on the tip of a robot finger driven by a piezoelectric bimorph strip and the root of the finger is mounted on a linear slider. Two kinds of active sensing are introduced. First, the heated sensor is contacted with an object and pyroelectric output signals are collected in order to obtain the information on tactile warmth. Next, the heated sensor is slid over the object and piezoelectric output signals are collected in order to obtain the information on feelings of vibration. Through the discussion about each sensing, three indexes representing features of the collected data are extracted and proposed as the sensor outputs for the evaluation of tactile sensation. The measurement using the sensor system is done on the samples used in the distinction examination. Comparison with the results shows that the sensor system extracts features on feelings of vibration and warmth.     

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.     

Extracting data from human manipulation of objects towards improving autonomous robotic grasping

Humans excel in manipulation tasks, a basic skill for our survival and a key feature in our manmade world of artefacts and devices. In this work, we study how humans manipulate simple daily objects, and construct a probabilistic representation model for the tasks and objects useful for autonomous grasping and manipulation by robotic hands. Human demonstrations of predefined object manipulation tasks are recorded from both the human hand and object points of view. The multimodal data acquisition system records human gaze, hand and fingers 6D pose, finger flexure, tactile forces distributed on the inside of the hand, colour images and stereo depth map, and also object 6D pose and object tactile forces using instrumented objects. From the acquired data, relevant features are detected concerning motion patterns, tactile forces and hand-object states. This will enable modelling a class of tasks from sets of repeated demonstrations of the same task, so that a generalised probabilistic representation is derived to be used for task planning in artificial systems. An object centred probabilistic volumetric model is proposed to fuse the multimodal data and map contact regions, gaze, and tactile forces during stable grasps. This model is refined by segmenting the volume into components approximated by superquadrics, and overlaying the contact points used taking into account the task context. Results show that the features extracted are sufficient to distinguish key patterns that characterise each stage of the manipulation tasks, ranging from simple object displacement, where the same grasp is employed during manipulation (homogeneous manipulation) to more complex interactions such as object reorientation, fine positioning, and sequential in-hand rotation (dexterous manipulation). The framework presented retains the relevant data from human demonstrations, concerning both the manipulation and object characteristics, to be used by future grasp planning in artificial systems performing autonomous grasping.     

Tactile sensing and control of robotic manipulation

—This paper reviews the current state of the art and predicts the outlook in robotic tactile sensing for real-time control of dextrous manipulation. We begin with an overview of human touch sensing capabilities and draw lessons for robotic manipulation. Next, tactile sensor devices are described, including tactile array sensors, force-torque sensors, and dynamic tactile sensors. The information provided by these devices can be used in manipulation in many ways, such as finding contact locations and object shape, measuring contact forces, and determining contact conditions. Finally, recent progress in experimental use of tactile sensing in manipulation is discussed, and future directions for research in sensing and control are considered.     

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。     

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.     

Dynamics of a learning controller for surface tracking robots onunknown surfaces

An extended Kalman filter is applied to simulated sensor information as an approach to the surface estimation problem. It is assumed that a robotic probe equipped with a tactile sensor is given the task of working with a completely unknown surface. Kinematics and control based on tactile measurements are briefly discussed. An estimator which provides surface information as obtained by an inherently noisy force sensor is designed. From these estimates, a controller is given the capability of learning the constraint surface, thereby rejecting the noisy sensor data. After a short time, surface tracking is similar to the case of constrained motion on known surfaces     

SmartTouch: electric skin to touch the untouchable

Augmented haptics lets users touch surface information of any modality. SmartTouch uses optical sensors to gather information and electrical stimulation to translate it into tactile display. Augmented reality is an engineer's approach to this dream. In AR, sensors capture artificial information from the world, and existing sensing channels display it. Hence, we virtually acquire the sensor's physical ability as our own. Augmented haptics, the result of applying AR to haptics, would allow a person to touch the untouchable. Our system, SmartTouch, uses a tactile display and a sensor. When the sensor contacts an object, an electrical stimulation translates the acquired information into a tactile sensation, such as a vibration or pressure, through the tactile display. Thus, an individual not only makes physical contact with an object, but also touches the surface information of any modality, even those that are typically untouchable.     

Haptically Enabled Handheld Information Display With Distributed Tactile Transducer

This paper describes the design, construction, and initial evaluation of a handheld information device that supports combined tactile and graphical interaction. The design comprises a liquid crystal graphic display co-located with a miniature, low-power, distributed tactile transducer. This transducer can create electronically-controlled lateral skin deformation patterns which give the sensation of sliding over small shapes. It is integrated within a slider mechanism to control scrolling. It also functions as a detent when pushing on it. Tactile feedback and the combination of visual and tactile feedback in a mobile context enable the development of new functions, such as multimodal navigation within large graphic spaces     

敏感高分子“人工皮肤” 力觉感受器 的数学理论依据

本文以PVDF敏感材料的结构性能为出发点,对机器人触觉传感器——人工皮肤的理论基础进行了研究,并就PVDF的压电性从弹性力学的角度进行了分析。在此基础上给出了这一变形体的非线性动态系统的数学描述,为精确而有效地采集力觉感受器的压电信号奠定了基础,为机器人触觉力传感器的设计与制造提供了理论依据。