Three-axis pneumatic tactile display with integrated capacitive sensors for feedback control

In this paper, we propose a three-axis pneumatic tactile display that is precisely controlled by using integrated capacitive displacement sensors. The proposed tactile display consists of a core body with a 3 × 3 balloon array on its top surface, four lateral balloons made of latex rubber, and inner and outer frames that include capacitive displacement sensors based on a flexible printed circuit board. The 3 × 3 balloon array on the core body is designed to apply normal haptic stimulation to a human fingertip. In addition, the lateral motions of the core body and each frame produce haptic stimulation in a tangential direction. Precise control of lateral motion was achieved by feedback control using the capacitive displacement sensors. The size of the fabricated tactile display was 26 × 26 × 18 mm³. We experimentally performed manipulation of the proposed device with a custom control system, thereby demonstrating accurate control of displacement.     

Mechanical feedback analysis of a ferrofluid-based module with 2D dynamic traveling waves for tactile display application

With the advances of human-machine systems, tactile displays have become one of the important features for modern products. Tactile feedback can increase working efficiency and help humans to explore new environments or objects by the sense of touch. This study used a 3 × 3 electromagnet array and a ferrofluid bladder to build a tactile display module, which can create smooth and continuous real-time 2-D dynamic traveling waves. The interactions of magnetic fields between electromagnets in the array were used to control the directions of the magnetic lines of force to create different graph patterns. Our user test showed that the overall tactile perception rate was 74% for the 2-D dynamic graph patterns generated using the ferrofluid-based tactile display module.     

KAT II: Tactile Display Mouse for Providing Tactile and Thermal Feedback

This paper proposes a tactile display mouse providing both pin-array-type tactile feedback and thermal feedback. The pin-array-type tactile display is composed of a 6 × 5 pin-array that is actuated by 30 piezo-electric bimorphs. Micro shape and vibrotactile feedback can be generated by the device, and various planar distributed patterns can be displayed as can Braille cell patterns. The thermal feedback device is composed of a thin-film resistance temperature detector, a Peltier thermoelectric heat pump and a water cooling jacket. Users can discriminate among different materials by considering the temperature variation that can be sensed as they touch an object's surface. This paper also includes an experimental evaluation of the tactile display mouse to prove the effectiveness of displaying textures. Evaluation of the ability to identify material properties was conducted using the thermal feedback part that displays a simulated temperature profile. To investigate thermo–tactile interaction, an experiment determining perceived magnitude of vibrotactile stimulus according to different temperature conditions was conducted.     

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.     

Lump localisation through a deformation-based tactile feedback system using a biologically inspired finger sensor

The ability to localise harder areas in soft tissues is often desired during robot-assisted surgical operations. A deformation-based tactile feedback system was tested for the detection of objects within soft tissues, after being chosen over common pressure-based designs. This system uses a biologically inspired sensor that offers a new finger-like approach to tactile sensing. A tactile shape display developed from previous successful designs was used to output the sensed tactile information. Using the tactile feedback system on a mechanical teleoperated device, test subjects palpated a number of artificial tissue models to locate objects of varying stiffness. The addition of the tactile feedback system improved the detection of the objects from 64% to 98%, reduced the localisation error from 18 to 11 mm, and also decreased the time the users spent palpating the tissue from 55 to 37 s. This demonstrates that a deformation-based tactile feedback system can be used to successfully locate hard embedded objects within soft tissue, with a significant improvement over force and visual feedback alone. During testing, it was found that the users were able to more accurately locate the softest embedded objects compared to stiffer ones. Reasons for this observation are discussed.     

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.     

A compact planar distributed tactile display and effects of frequency on texture judgment

This paper describes the development of a planar distributed tactile display and the evaluation of the results of its effectiveness for displaying textures. The tactile display is composed of a 6 × 5 pin array actuated by 30 piezoelectric bimorphs. The distance between each pin's centers is 1.8 mm. Vertical excursion of each pin is controlled over a 0–0.7 mm range. Perceptual experiments were conducted to evaluate the performance of the system under three conditions: active touch, passive touch with vibration and passive touch without vibration. The experimental results showed that vibrational stimuli helped subjects discriminate tactile patterns. Measurements of the error rate during discrimination tasks were used to find an optimal vibration frequency for stimuli presented at a constant sensation level (32 SLdB above threshold). The experiment was repeated, this time holding the energy transferred mechanically to the fingertip tissue constant. At low frequencies, we found that the passive stimulation allowed subjects to discriminate just as well as active touch of static stimuli did. The results suggested new possibilities for displaying texture using passive touch, constant energy and spatially varied vibration frequency.     

Development of a smart handheld surgical tool with tactile feedback

This paper presents a handheld surgical tool adapting a tactile feedback system. The tool consists of a 3-degree-of-freedom (DOF) force sensor and three tactile displays. The sensor is easily embedded in the tool by adopting the capacitive transduction principle. The sensor measures the direction and magnitude of the 3-DOF force applied to the tool tip. The fingertip grasping the tool is stimulated by the tactile display to transmit the contact force information measured by the sensor. The tactile display is actuated by employing a soft actuator technology based on a dielectric elastomer actuator such as a type of electroactive polymer actuator. In this work, a prototype of the tool is designed and fabricated. Its performance is experimentally validated.     

Modeling of a joint-type flexible endoscope based on elastic deformation and internal friction

Flexible endoscopes are widely used in minimally invasive surgical robot systems. Various kinematic models have been developed for describing the deformation of such endoscopes. For joint-type flexible endoscopes, most existing models neglect the effect of internal friction and cannot precisely show the shape.

In this paper, we propose a new nonlinear bending model. The rubber tube and metal net at each joint are approximated as a tube under elastic deformation and are assigned an equivalent bending stiffness. The internal friction force is also taken into account to build the moment balance equation at each joint. Groups of experiments were performed to validate the nonlinear model. The results closely confirm the model’s predictions. The model’s tip position error during the bending and unbending phases are 1.48?±?0.99?mm and 1.68?±?0.91?mm respectively; the bending angle errors are ?5.50?±?2.54° and 1.68?±?3.66°, respectively The model can also take account of the hysteresis effect of the bending, which is quite common for cable-driven flexible robots. Moreover, the model has good computational efficiency, making it suitable for real-time control.     

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.     

Tactile display terminal for visually handicapped

An experimental computer-driven tactile display terminal has been designed for the visually handicapped. The display presents solid graphic information by means of 16 × 16 tactor elements. Laboratory assessment has shown the optimum height of tactors for the perception of letters to be about 2 mm, and subjects were able to recognize simple three-dimensional patterns.     

Towards developing perceivable tactile feedback for mobile devices

As mobile technologies such as cellular telephones reduce in both size and cost, and improve in fidelity, they become a more attractive option for performing tasks such as surfing the Web and accessing applications while on-the-go. The small size of the visual display limits the amount of information that can be presented, which may lead to cluttered interfaces. Tactile feedback (e.g. vibrations) provides one solution to reducing the burden on the visual channel. This paper describes a series of studies conducted with the goal of developing perceivable tactile icons (tactons) to aid in non-visual interactions with mobile applications. In contrast to previous work, our research addresses the development of pairs of tactons, rather than individual tactons, with the goal of conveying two-state signals such as ‘on/off’, ‘slower/faster’, or ‘left/right’. Such communication can help reduce visual demands associated with using mobile applications, allowing the device to convey important information while the users’ hands and eyes are otherwise occupied. Realistic conditions were simulated in a laboratory-based environment to determine how auditory distracters could affect the perception of tactons. Findings show that recognition rates differed depending on the design of the vibration pair parameters, and type of auditory distracter. This research culminated in a set of guidelines, which tactile interface designers can integrate as they design mobile applications to improve access, as well as insights which can guide future research on tactile feedback for mobile devices.     

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。     

A bio-inspired predictive sensory-motor coordination scheme for robot reaching and preshaping

This paper presents a sensory-motor coordination scheme for a robot hand-arm-head system that provides the robot with the capability to reach an object while pre-shaping the fingers to the required grasp configuration and while predicting the tactile image that will be perceived after grasping. A model for sensory-motor coordination derived from studies in humans inspired the development of this scheme. A peculiar feature of this model is the prediction of the tactile image. The implementation of the proposed scheme is based on a neuro-fuzzy module that, after a learning phase, starting from visual data, calculates the position and orientation of the hand for reaching, selects the best-suited hand configuration, and predicts the tactile feedback. The implementation of the scheme on a humanoid robot allowed experimental validation of its effectiveness in robotics and provided perspectives on applications of sensory predictions in robot motor control.     

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.     

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.     

遥操作机器人的新型力反馈算法*

在采用液压挖掘机改造的遥操作机器人双向伺服控制系统中,针对大臂和前臂两个自由度构建力反馈控制算法。以准确地获取从端机器人与环境的作用力,使反馈力能够更好地反映从端工作状况为目的,采用构建干扰力补偿项的方法消除干扰力对反馈力的影响;以机器人转角为输入,以空载时检测到的液压缸作用力为输出,通过径向基函数构建干扰力补偿项,此补偿项可对多种因机器人的机械本体动力学特性产生的干扰力之合力进行补偿。实验证明,在以液压机构为从手的双向力反馈系统中,通过构建干扰力补偿项的方法提高力反馈效果的方法是可行的,采用的带有干扰力     

Magnebike: A magnetic wheeled robot with high mobility for inspecting complex‐shaped structures

This paper describes the Magnebike robot, a compact robot with two magnetic wheels in a motorbike arrangement, which is intended for inspecting the inner casing of ferromagnetic pipes with complex‐shaped structures. The locomotion concept is based on an adapted magnetic wheel unit integrating two lateral lever arms. These arms allow for slight lifting off the wheel in order to locally decrease the magnetic attraction force when passing concave edges, as well as laterally stabilizing the wheel unit. The robot has the main advantage of being compact (180 × 130 × 220 mm) and mechanically simple: it features only five active degrees of freedom (two driven wheels each equipped with an active lifter stabilizer and one steering unit). The paper presents in detail design and implementation issues that are specific to magnetic wheeled robots. Low‐level control functionalities are addressed because they are necessary to control the active system. The paper also focuses on characterizing and analyzing the implemented robot. The high mobility is shown through experimental results: the robot not only can climb vertical walls and follow circumferential paths inside pipe structures but it is also able to pass complex combinations of 90‐deg convex and concave ferromagnetic obstacles with almost any inclination regarding gravity. It requires only limited space to maneuver because turning on the spot around the rear wheel is possible. This high mobility enables the robot to access any location in the specified environment. Finally the paper analyzes the maximum payload for different types of environment complexities because this is a key feature for climbing robots and provides a security factor about the risk of falling and slipping. © 2009 Wiley Periodicals, Inc.     

Methods for haptic feedback in teleoperated robot-assisted surgery

Teleoperated minimally invasive surgical robots can significantly enhance a surgeon's accuracy, dexterity and visualization. However, current commercially available systems do not include significant haptic (force and tactile) feedback to the operator. This paper describes experiments to characterize this problem, as well as several methods to provide haptic feedback in order to improve surgeon's performance. There exist a variety of sensing and control methods that enable haptic feedback, although a number of practical considerations, e.g. cost, complexity and biocompatibility, present significant challenges. The ability of teleoperated robot-assisted surgical systems to measure and display haptic information leads to a number of additional exciting clinical and scientific opportunities, such as active operator assistance through "virtual fixtures" and the automatic acquisition of tissue properties.     

MEMS-based tactile displays

This paper discusses state-of-the-art tactile displays fabricated by a micro-electronic-mechanical-system (MEMS). A tactile display conveys tactile sensations to users by using actuators. Traditional tactile displays consist of large size actuators, such as a motor or an ultrasound vibrator, to convey tactile feedback by vibration. In addition, the tactile sensation of traditional displays has poor resolution. Microelectromechanical system (MEMS) technology, which is a miniature fabrication process, enables etching, sputtering and assembling of miniature structures. Recently, the technology was applied to tactile displays. For example, shape memory alloy (SMA) actuators are widely used in tactile displays to convey roughness or vibration. The actuators are fabricated by a sputtering process and then thinned. The displays convey various tactile sensations, including feedback and tactile sensations of objects such as paper or wood. This paper is a review of tactile displays fabricated by MEMS technology. We also describe the fabrication processes and stimulation methods to present the potential and applications of the displays.