We propose a coil-patterned waveguide sheet for magnetic coupling in a 2-D waveguide power transfer system (2DWPT). In magnetic resonance wireless power transfer, the coupling coefficient decreases due to flux leakage. Our proposed system can extend the length of the Tx waveguide sheet without reducing the coupling coefficient. The leakage flux can be adjusted by reducing the group velocity in the waveguide sheet. The effectiveness of this waveguide power transfer method is supported by simple theoretical analyses. Our simulation and measurement results concur with the analytical findings and demonstrate that the proposed waveguide sheet can be extended while maintaining practical efficiency.

In recent years, the need for guide dogs has increased, and a more efficient methodology for training guide dog trainers is accordingly required. One challenge is that haptic information, which is a significant part of guide-dog training, is difficult to explain and visualize. Virtual reality (VR) systems have attracted attention owing to their ability to support high-level immersive interactions with the presence of multisensory experiences. A haptic-enabled VR system could address the limitations of the conventional method and support novice trainers in practicing in an immersive and remote transmission manner. This study presents a handle-based sensing setup for recording haptic experiences of trainers during guide dog training for use in a VR system. Considering trainers perceive and apply forces via handle to obtain and control dog motion status, the applied forces are decoded as haptic information and recorded using corresponding sensors. While accuracy of proposed setup for collecting required data is checked to be high(average errors of validating forces and yaw angles are 0.4N and 0.93° respectively), we believe that the proposed recording system is able to measure haptic experiences for further haptic experience re-establishments in proposed VR guide-dog training system and could finally facilitate the education of a large number of dog trainers.

Ultrasound beam propulsion, a propulsion system that uses airborne ultrasound phased arrays (AUPAs) to propel a blimp in an indoor environment to propel a blimp, has advantages for operations near humans such as no audible noises and no risk of propeller strike. To achieve the high mobility with limited actuation force of AUPAs, the dynamics should be fully exploited. In this paper, we propose a two-degree-of-freedom controller specifically tailored for ultrasound beam propulsion. We investigate the trajectory of bang-bang control with constant thrust (BBCT control), where a blimp accelerates and then decelerates with constant thrust reaching the terminal point at rest, as one of the most basic trajectories. First, we analytically derive the trajectory of a blimp under aerodynamic drag. Then, we provide a trajectory generator that derives the maximum constant thrust for an arrangement of AUPAs and the constraints on the control input. Finally, we integrate the trajectory generator and a PID-based feedback controller in a physical setup. We evaluated the proposed controller in physical and numerical experiments. The results showed that the proposed method allows a blimp to reach the terminal point almost in expected time. We also showed that the flight time is shorter than a PID-based one-degree-of-freedom controller, which was typically used in previous studies, by 19.0 − 43.2 %.

Human–robot interaction (HRI) has been widely researched in diverse applications. A robot following a person is one such scenario investigated in the HRI field. However, human movements and actions are complex and can change dramatically. We herein demonstrate a machine learning-based system that allows a person-following robot to track in real-time the predicted future motion of a walking human, from a first-person perspective. We assume that a depth sensor that can detect the human skeleton is loaded on a mobile robot to provide data on the user’s motion from a first-person perspective. The system calculates the coordinates of the center of gravity (COG) and 25 body joints of the user. These coordinates of COG and 25 body joints are relative to the robot based on the position of the person tracked, and these are used for the input dataset of a neural network (NN) that predicts human motion. A five-layered NN estimates the relative vectors in real-time between the current person’s COG and the future position of the 25 body joints. Using a proportional–integral–derivative (PID) controller, the person-following robot can track the predicted position of a walking human 0.5 s in advance to increase the robustness of following and to avoid delays.

Avoiding collisions with humans during daily life is essential in human–robot interaction (HRI) environments. To this end, we propose a neural network (NN) to predict walking motions—the most frequent human motion in HRI. In a previous study, an NN was set up for predicting the walking position 0.5 s ahead by using skeletal coordinates with a low root mean square error. However, the prediction accuracy was found to be lower when predicting the four limbs, possibly because their motions had strong position uncertainty during walking. In the present study, a particle filter (PF) was used to predict a possible range, rather than the specific coordinates, of foot positions. The PF was used in three steps: initialization, sampling importance resampling, and moving the particle to predict. Once the initial distribution was set up, only the last two steps needed to be repeated frame-by-frame. The probability state distribution results of the feet were verified using three measures, and the reliability of these results was verified.

This paper introduces a midair balloon interface, a fast and soft interactive object in mid-air. Our approach tackles the trade-off between safety and speed by controlling a soft helium-filled balloon with external actuators and sensors. We developed a prototype system that uses airborne ultrasound phased arrays to propel a balloon and high-speed stereo cameras to track its motion. This configuration realizes both a high thrust/weight ratio and such a soft body that is safe-to-collide. We describe a sight-based interaction and a touch-based interaction that leverage the safety and speed of a midair balloon interface. A sight-based interaction allows the user to keep the object inside her/his view within reach by controlling a balloon to follow the direction of the user’s face. A touch-based interaction allows the user to manipulate the object directly with his/her hand, issue a command by moving his/her finger on the surface, and receive vibrotactile feedback produced by vibrating the balloon with amplitude-modulated ultrasound. We describe the implementation and evaluation of the prototype and explore the application scenarios.

We propose LipNotif, a non-contact tactile notification system that uses airborne ultrasound tactile presentation to lips. Lips are suitable for non-contact tactile notifications because they have high tactile sensitivity comparable to the palms, are less occupied in daily life, and are constantly exposed outward. LipNotif uses tactile patterns to intuitively convey information to users, allowing them to receive notifications using only their lips, without sight, hearing, or hands. We developed a prototype system that automatically recognizes the position of the lips and presents non-contact tactile sensations. Two experiments were conducted to evaluate the feasibility of LipNotif. In the first experiment, we found that directional information can be notified to the lips with an average accuracy of ± 11.1° in the 120° horizontal range. In the second experiment, we could elicit significantly different affective responses by changing the stimulus intensity. The experimental results indicated that LipNotif is practical for conveying directions, emotions, and combinations of them. LipNotif can be applied for various purposes, such as notifications during work, calling in the waiting room, and tactile feedback in automotive user interfaces.

Augmented Human (AH) is a research field enhancing human physical abilities or supporting human activity using advanced technologies. As one of the AH approaches, previous studies have attached an actuator to a human body or tools used for an activity. The attached actuators are used to control their movements to support an activity. In this study, instead of attaching actuators, we propose to directly apply noncontact ultrasound force to a lightweight tool to manipulate it. The advantage of using noncontact force is that users do not need to wear a specific device and to process tools used for the activity. As a proof-of-concept system, we developed an ultrasound-based curveball system by which table tennis players can shoot a curveball regardless of their physical ability. In the system, a moving ping-pong ball (PPB) is a target tool for remote manipulation. The system curves the trajectory of a moving PPB by continuously focusing ultrasound on it. Users can control the curve timing and the curve direction (left or right) using a racket-shaped controller. In the user study, we conducted an actual table tennis match using the curveball system and qualitatively confirmed that the player using the system had the upper hand. Another user study using a ball dispenser quantitatively showed that the ultrasound-driven curveball increased the number of mistakes of the opponent player 2.95 times. These results indicate that the proposed concept is feasible.

In this study, we construct a neural network that learns a falling motion by measuring a behavior that simulates a fall forward due to a trip, in order to realize a system to predict a fall in advance. Recent advances in machine learning techniques have enabled the development of methods for predicting behavior in real time. This is expected to be used for walking to predict a fall and provide support in advance to reduce injuries. Although many systems have been proposed to measure and detect a fall, there are few studies on data measured when a fall is caused by an unexpected disturbance during normal walking. Therefore, we do not know how long it takes for a person to fall over after a disturbance occurs, and we do not have much understanding of how predictable the phenomenon is in principle. In this study, we constructed a system to simulate a fall with a disturbance and measured the 3D skeletal data. From these results, the average time between the disturbance and the start of the fall was calculated. By using a neural network to make predictions, we confirmed that falls can be predicted at the point of the disturbance.

In this study, we prototype and examine a system that allows a user to manipulate a 3D virtual object with multiple fingers without wearing any device. An autostereoscopic display produces a 3D image and a depth sensor measures the movement of the fingers. When a user touches a virtual object, haptic feedback is provided by ultrasound phased arrays. By estimating the cross section of the finger in contact with the virtual object and by creating a force pattern around it, it is possible for the user to recognize the position of the surface relative to the finger. To evaluate our system, we conducted two experiments to show that the proposed feedback method is effective in recognizing the object surface and thereby enables the user to grasp the object quickly without seeing it.

In this paper, we clarified the temporal condition in predicting human walking through a neural network. In order to examine the relationship between human walking and prediction, we analyzed the walking motion through two different types of prediction system. One analyzed the positional error of predicted body joints to examine which moment's motion while walking influences the prediction accuracy. As a result, the error peaked around the time when the system uses the information of Toe-Off (TO) for prediction. The other analysis uses the ternary classification which predicts the sudden change of walking behaviors: turn left, turn right or stop. By dividing the temporal data into a shorter period, we examine which phase contains the essence of the proceeding direction. As a result, the correct answer rate was high in the phase around TO. From these results, it is possible to improve the accuracy of gait prediction by using the skeleton data around TO moment since the TO is the time to determine the moving direction.

In this paper, we show the interaction with a future self-silhouette image using human body motion prediction. There has been a method of extracting skeleton information of a person and learning by using a neural network so as to predict the future body movement 0.5 seconds ahead and present it in real-time. By using this method, it has been shown that the position of the center of gravity can be estimated with an accuracy of about several centimeters for a limited motion such as jump and walking. In this paper, we focus on the fact that this previous method can estimate body movement and display it in real-time. The prediction and display enable to show the image 0.3 seconds before the actual motion, which is slightly longer than the time that a person can react after seeing the prediction result. Thus displaying user's own future action in 0.3 seconds in real-time may change their behavior by seeing it. In this paper, we focus on the jump action and project its predicted motion on the ground. By improving the previously reported method, it is possible to predict the motion with an error of about 2 cm on average on the movement of the center of gravity 0.5 seconds ahead. We projected the silhouette image under three different timing conditions: 1) delay, 2) real-time, and 3) prediction. The paper shows how three different conditions are felt and how they affect human actual movement.

Physically moving real objects via a computational force connects computers and the real world and has been applied to tangible interfaces and mid-air display. Many researchers have controlled only a stationary real object by computational force. On the other hand, controlling a moving object can expand the real space that is controllable by the computer. In this paper, we explore the potential of computational force from the viewpoint of changing the trajectory of a moving object. Changing the trajectory is the primitive model to control a moving object, and it is the technological challenge requiring high-speed measurement and non-contact force with high-spatial resolution. As a proof-of-concept, we introduce Hopping-Pong changing the trajectory of a flying Ping-Pong Ball (PPB) using ultrasound force. The result shows that Hopping-Pong changes the trajectory of a PPB 344 mm. We conclude that a computational force is capable of controlling a moving object in the real world. This research contributes to expanding the computationally controlled space with applications for augmented sports, HCI and factory automation.

In this paper, we present BaLuna, a prototype of an externally actuated midair display for indoor use in a room-scale workspace. This system is the first battery-less midair display with a one-meter-cubic workspace. The system projects an image onto a balloon screen whose position is controlled by airborne ultrasound phased array (AUPA) devices. Users can naturally manipulate the screen position by dragging and dropping the screen directly with their hands. We adapted feedback-based acoustic manipulation technology that enables sparsely distributed AUPA devices to control the screen position. This is combined with a depth-image-based tracking and a three-dimensionally calibrated projector.

This paper proposes a whole body human power-based energy harvesting (HPBEH) scheme which aggregates the power from multiple HPBEH devices distributed on a special cloth embroidered with conductive threads. Each HPBEH devices is connected by using a special connector consisting of a tack and a clutch without one-to-one wiring. In a conventional HPBEH system, each device individually has its own HPBEH element. Power aggregation system using a multiple HPBEH devices can supply higher power than conventional EH systems to a power-hungry device. And each HPBEH devices has a flexible piezoelectric element (PE) placed in the whole body joints and sole. In the flexible PEs, the output voltage and the time when output reaches the peak are different. The experimental results demonstrate the feasibility of the power aggregation system in those case.

In this paper, we show that an inverted pendulum can be stabilized manually even when a user does not know the physical characteristics and the current state of the pendulum. We display two markers: one indicates current position of the base of the pendulum and the other indicates the target position where the base should be located 0.3 seconds later. Subjects can stabilize the pendulum for a significantly longer time than seeing the real pendulum directly, just by chasing the target marker.

We propose a system that controls the spatial distribution of odors in an environment by generating electronically steerable ultrasound-driven narrow air flows. The proposed system is designed not only to remotely present a preset fragrance to a user, but also to provide applications that would be conventionally inconceivable, such as: 1) fetching the odor of a generic object placed at a location remote from the user and guiding it to his or her nostrils, or 2) nullifying the odor of an object near a user by carrying it away before it reaches his or her nostrils (Fig. 1). These are all accomplished with an ultrasound-driven air stream serving as an airborne carrier of fragrant substances. The flow originates from a point in midair located away from the ultrasound source and travels while accelerating and maintaining its narrow cross-sectional area. These properties differentiate the flow from conventional jet- or fan-driven flows and contribute to achieving a midair flow. In our system, we employed a phased array of ultrasound transducers so that the traveling direction of the flow could be electronically and instantaneously controlled. In this paper, we describe the physical principle of odor control, the system construction, and experiments conducted to evaluate remote fragrance presentation and fragrance tracking.

In this paper, we propose a machine learning-based system named "Computational Foresight" that can forecast human body motion 0.5 seconds before the actual motion in real-time. This forecasting system can be used to estimate human gestures in advance to the actual action for reducing delays in interactive system. In addition, the system can be applied to instruct sports actions properly, and prevent elderly from falling to the ground, and so on. Proposed system detects 25 human body joints to use those data for input dataset of machine learning. We created 5-layered neural network to estimate human body motion in real-time. In our experiment, we measured jump motions of subjects for learning. In our evaluation, the prototype system scored that the center of gravity of whole body can be forecasted 0.5 sec before with its accuracy of 7.9 cm.

The main goal of our research is to develop a haptic display that makes it possible to convey shapes, hardness, and textures of objects displayed on 3D TV. Our evolved device has three 5 mm diameter actuating spheres arranged in triangular geometry on each of three fingertips (thumb, index finger, middle finger). In this paper, we describe an overview of a novel haptic device and the first experimental results that twelve subjects had succeeded to recognize the size of cylinders and side geometry of a cuboid and a hexagonal prism.

This paper proposes a method to determine a physical layer (PHY) parameter that minimizes energy-per-bit rate (EBR) in a two-dimensional communication (2DC) environment. EBR is the power consumption used for 1- bit transmission/reception. 2DC uses a sheet-like waveguide medium, which guides the micro-wave along the sheet. In our previous work, the possibility of energy- efficient data transmission by using TransferJet devices in 2DC environment was reported. The reported maximum transmission rate was 71.1 Mbps with a power consumption of 118 mW. The EBR was two orders of magnitude lower than that of ZigBee despite the same power consumption. However, the data rate significantly degraded at some transceiver positions depending on the delay spread of the 2DC channel. The decrease of the transmission rate was caused by a mismatch between the PHY parameter of the communication system and the characteristics of the communication environment. This pa-per presents a method to determine an optimum PHY parameter for minimizing EBR. The experimental results demonstrate the feasibility of the energy-efficient data transmission in 2DC environments.

The unlicensed band for ultra-wideband (UWB) radio systems, 3.1-10.6 GHz, is an attractive frequency resource for indoor high-speed wireless communications. Recently we have proposed a scheme to use the UWB's frequency range for wireless local area networks (WLANs) using off-the-shelf 2.4-GHz WLAN devices and dedicated frequency converters. The signals converted into the UWB's frequency range are transferred through special floor tiles that guide microwaves with low loss. This demo shows a prototype system consisting of the frequency converters and two-dimensional communication (2DC) tiles.

In this paper, we propose a novel interactive system that mutually copies adjacent 3D environments optically and physically. The system realizes mutual user interactions through haptics without wearing any devices. A realistic volumetric image is displayed using a pair of micro-mirror array plates (MMAPs). The MMAP transmissively reflects the rays from an object, and a pair of them reconstructs the floating aerial image of the object. Our system can optically copy adjacent environments based on this technology. Haptic feedback is also given by using an airborne ultrasound tactile display (AUTD). Converged ultrasound can give force feedback in midair. Based on the optical characteristics of the MMAPs, the cloned image and the user share an identical coordinate system. When a user touches the transferred clone image, the system gives force feedback so that the user can feel the mechanical contact and reality of the floating image.

A method to present volumetric haptic objects in the air using spatial modulation of ultrasound is proposed. Previous methods of airborne ultrasonic tactile display were based on vibrotactile radiation pressure and sensor feedback systems, which result in low spatial receptive resolution. The proposed approach produces a spatially standing haptic image using stationary ultrasonic waves that enable users to touch 3D images without depending on vibrotactile stimulation and sensor feedback. The omnidirectional spatial modulated haptic images are generated by a phased array surrounding a workspace, which enables enough power to feel shapes without vibrotactile technique. Compared with previous methods, the proposed method can create a completely silent image without temporal ultrasonic modulation noise that is free of the problems caused by feedback delay and errors. To investigate the active touch profiles of an ultrasonic image, this paper discusses a method to synthesize a haptic holographic image, the evaluation of our algorithm, and the results of pressure measurement and subjective experiments.

In this paper, we evaluate isolation property of an ultra-wide band (UWB) two-dimensional communication (2DC) tile. The UWB 2DC tile is based on 2DC technology and enables a room-size and high-speed network. In 2DC, radio waves are confined in a sheet-like waveguide. An evanescent field is generated above the waveguide and used to establish the connection between the devices with a dedicated coupler. Energy radiated from the waveguide is so small that coexistence between signals in the tile and in the air with little interference in the same room is possible. To evaluate the interference between an over-the-air communication path and an on-tile communication path, the transmittance between an antenna in the air and a feeding coupler on the tile is measured with a vector network analyzer. The measurement is conducted with two typical boundary conditions of the waveguide: a short boundary and an open boundary. The experimental results show that the transmittance is about - 60 dB or less at 600 mm above the tile in each boundary. This value is lower than that of free-space propagation. Therefore, the UWB 2DC tile system can keep the stable and high-speed network even if the same frequency band is shared with in-air UWB communication.

We present HaptoMime, a mid-air interaction system that allows users to touch a floating virtual screen with hands-free tactile feedback. Floating images formed by tailored light beams are inherently lacking in tactile feedback. Here we propose a method to superpose hands-free tactile feedback on such a floating image using ultrasound. By tracking a fingertip with an electronically steerable ultrasonic beam, the fingertip encounters a mechanical force consistent with the floating image. We demonstrate and characterize the proposed transmission scheme and discuss promising applications with an emphasis that it helps us 'pantomime' in mid-air.

In this paper, we propose a remote grip force sensing method based on skin surface hardness measurement. The measurement system is composed of an airborne ultrasound phased array and a laser displacement sensor. The surface hardness distribution of a human hand is estimated by optically measured surface vibration amplitude induced by the ultrasound radiation pressure. The realtime grip force is estimated using the relationship between the hand surface compliance and the grip force which is obtained experimentally in advance. The feasibility of grip force estimation is confirmed for a gripping hand keeping a constant posture.

We fabricated a tactile display which can generate vibrotactile sensation on human skin on which no equipment is mounted. It utilizes focused airborne ultrasound radiation pressure for stimulation. The workspace of our new tactile display is widened to a cube of 1 m × 1 m × 1 m, which allows users free motions in it. In order to widen the workspace, our new prototype integrates multiple ultrasound transducer units and achieves a large aperture airborne ultrasound phased array. As the workspace is widened, it has become possible to stimulate arbitrary regions all over a human body. The amplitude of imposed radiation pressure can be time-variant. The profiles of generated vibrotactile stimuli can be designed with a temporal resolution of 0.5 ms and 320-level quantization of radiation pressure amplitude. It is easy to choose a recorded waveform and reproduce it as vibrotactile stimuli at an arbitrary spatial point. This paper introduces how our new tactile display works and reports its performance evaluation.

The overlapping of vibrations that are in different phases and in close proximity to each other produces a tactile image that is more localized than one produced by pin vibrators. The mechanism behind the former is still unclear; it may be attributed to the fact that the resultant vibration is highly localized and of a high frequency, making the tactile sensations more perceptible by the human hand. In this study, a finite element (FE) model of a human finger is analyzed to investigate the reason for the difference in the sizes of tactile images produced under different mechanical conditions. In the dynamic analysis, we observed the spatial distribution of the strain energy density (SED) in the model and estimated the perceptual area of the mechanical stimuli. To determine the perceptual area, the threshold SED for perceiving the vibratory stimuli was determined by analyzing the FE finger model on a flat vibratory surface. In the deformation analysis results, we observed that the spatial distribution of SED was more localized by the overlapped vibrations than in a pin vibrator. Moreover, spectral analysis revealed that a higher-frequency vibration was generated locally between the two vibrations. A psychophysical experiment was conducted to determine the effect of the high frequency component on detection thresholds.

This paper proposes a contactless touch screen that produces tactile sensation just 1-3cm before the actual touch on the screen. The system has a screen, visual projectors, and sensors for finger motion detection, which composes a non-contact touch screen by gesture sensing. In this paper we add a non-contact tactile display using an airborne ultrasound phased array. The key device of the system is a screen that is a scattering plane for visual projectors and transparent for ultrasound. We show the design of the screen and examine the effectiveness through numerical simulations and experiments. The screen has an additional property that stops the air flow going through the screen maintaining the transparency for the ultrasound. We constructed the contactless touch screen system and examined the position sensing accuracy under the tactile support.

In this paper, we propose a remote measurement system of surface compliance distributions for haptic broadcasting. Our system is composed of an ultrasound phased array generating acoustic radiation pressure on the remote object surface and a laser displacement sensor. The compliance is evaluated by the ratio of the surface displacement to the applied force. We set up a system to examine the feasibility of the method. In the experiments, the distribution of the surface compliance comparable to the human skin was successfully measured for a flat object surface.

We have prototyped a multi-finger haptic system that makes it possible to present a virtual object that applies attractive force to three fingers and the palm of the right hand, and evaluated the user's perception of the size and shape of an object. It was suggested from the results of a size experiment that the size perception can be conveyed more accurately by grasping the virtual object along with force feedback applied to the palm. We found from the results of a shape experiment that attractive force is mainly effective in the perception of tapering or curvature.

In this paper, we show experimental results indicating that tactile mechanoreceptors have non-linear sensitivity to an applied vibration. We focus on the perceptual characteristic of high frequency amplitude-modulated (AM) vibration. It is known that humans can feel AM vibration even when its carrier frequency is higher than the perceivable range. Non-linearity of perception should be taken into consideration for explaining this characteristic. We observed a deformation of the skin when the AM vibration is applied. We found that we can detect an envelope of the applied AM vibration, even when the skin surface deforms as a linear elastic body; whereas harmonic vibratory pairs cannot be perceived. This result indicates that only a squared value of a displacement, which is proportional to strain energy density, cannot explain the non-linearity of mechanoreceptors. These perceptual characteristics should be taken into consideration for designing a tactile display with multi-spectral vibrations. Otherwise, the simultaneous multi-spectral vibrations can affect each other and may change perceptions because of the non-linearity of the perceptual process.

A thermal change on a fingertip is essential for haptic perception. We have proposed a vision-based thermal sensor using thermo-sensitive paint and a CCD camera for telexistence. The thermo-sensitive paint is employed to measure thermal information on the basis of its color, which changes according to its temperature. The proposed sensor can simulate the physical interaction between a human fingertip and an object in order to measure surface thermal information correctly. Furthermore, because the proposed sensor can be easily integrated with our vision-based force sensor, a comprehensive measurement device for measuring haptic information can be realized. In this study, we constructed a prototype of the proposed thermal sensor and experimentally confirmed that this sensor could measure surface thermal information.

In this paper we describe a method of high accuracy device position and orientation detection for HCI environments. Our position and orientation detection is an additional function to the Two-Dimensional Communication technology, which enables devices placed on a thin sheet to achieve two key functions for ubiquitous computing, to communicate one another and to receive electricity through the sheet wirelessly. This paper discusses the method developed to specify the positions and orientation of devices placed on the sheet. It evaluates the accuracy of obtained position and orientation through an experiment using a prototype of our positioning sensor.

In this paper, a hologram with tactile reactions is presented. The developed system consists of three components; a holographic display, a hand tracker, and a tactile display. The tactile display, which is our original device, produces force on user's bare hand without any contact by using radiation pressure of airborne ultrasound. It adds the sense of touch to optical images floating in mid-air. In order to represent the feeling of impact, some improvements are added to the tactile display. As a result, the tactile display has an ability to produce up to 4.8 gf without air flow.

In this paper, we propose a new tactile sensor skin ("skin by touch area receptor" or STAR). The skin consists of two components. One is a sensor element which detects a contact area in addition to a contact force. The element is inspired by the fact that humans can discriminate sharpness of objects sensitively on any part of their bodies in spite of their several-centimeter two point discrimination thresholds. We have developed the sensor element that has such characteristics in a very simple structure; two layers of compressible insulators (urethane foam) which are sandwiched between three pieces of stretchable conductive sheets (conductive fabric). The other component is a sensor/communication chip. The chips are arranged at the boundaries of the elements, and the chips measure the capacitances between the conductive layers and send signals through the same conductive layers. The chips enable us to connect the elements to compose a soft robot skin including no long wires

In this paper, we propose a large-area tactile display by controlling suction pressure. This research is based on our discovery of tactile illusion that pulling a skin through a hole with air suction causes a sensation as if something like a stick is pushing the skin. This illusion implies that our mechanoreceptors are insensitive to the sign of stress (negative or positive), i.e. we detect not stress directly but strain energy. There are two key concepts to realize our tactile display. One is the tactile illusion mentioned above and the other is "multi primitive tactile stimulation." We explain our approach to produce various tactile sensations from a sharp edge to a plane surface with a simple structure of display device based on air pressure control, and report the experimental results.

The forms of communication available now are categorized into the one or three dimensional. One dimensional communication includes metal wires and optical fibers in which the electro-magnetic field is confined in one dimensional medium. Wireless communication based on RF or optical connection emits electro-magnetic field in 3-D space. Now what if we have "two-dimensional communication" in which signals travels from one point to another point freely in elastic two-dimensional space using electromagnetic field confined in 2-D space? In this paper, we describe such a new technology of 2-D communication brings new paradigm to robotics. The methodologies of machine-design, system-integration, sensing, and computing will be drastically changed. We show architecture of the 2-D signal transmission based on relaying packets between communication chips on a thin sheet, the physical structure of the 2-D signal transmission, the protocols of the signal relay, and the results of the basic experiments.

In this paper, we propose a tactile sensing element that communicates through two dimensional conductive skin layers without individual wires. Each tactile element has sensors and signal processors, and it broadcasts coded tactile signals through a couple of conductive layers. Since the conductive layers can be used for both the electrical power supply and the communication, simply sandwiching the chips between the layers completes electrical connection of tactile sensing chips. Since no metal wires exist, the skin is elastic and tough. High-resolution sensor skins can be easily fabricated in various shapes. In addition, because the tactile elements transmit the locally detected stress data with coded signals, we can obtain high-SN-ratio data from a very small sensing element put at a remote location. This paper describes the skin structure, the communication architecture, the structure of the sensing chip, and the results of basic experiments.

In this paper, we show a hypothesis on the sensing mechanism in the human tactile organ and its resolution. The hypothesis is that human skin cannot resolve any finer pattern than the resolution suggested by the two-point-discrimination test, but that variety created by four kinds of signals from four kinds of mechano-receptors makes it possible to detect fine feature of texture. This means if we control stimulus to four kinds of mechanoreceptors individually, the realistic contact-feeling display will not need higher spatial resolution than suggested by the two-point discrimination threshold. We examine this hypothesis through psychophysical experiments.

A human can lift up an object with almost minimal grasping force regardless of the friction coefficient between the fingers and the object, but the sensing mechanism for this remarkable task has not been well explained yet. We propose a tactile sensor to detect a friction coefficient at the moment of touch. With this sensor output we evaluate the largest lifting-force just before a slip happens, without any preliminary motions. The sensor has a sensing cell in the elastic body, which measures strain/stress components parallel and vertical to the surface. Those plural stress/strain parameters at a point gives the friction coefficient. A prototype sensor is fabricated with acoustic resonant tensor cell, and we examine its principles in experiments.

In this paper, we propose a method to realize flexible sensor skins integrated onto robot surfaces. By implanting wireless sensing elements in an elastic body, we obtain an elastic and tough sensitive skin which allows to be shaped freely. The element is a passive resonator chip whose resonant frequency reflects the stress around the chip. The resonant frequency is read out by a ground coil located at the bottom of the skin. The chip is simply composed of three functional parts, a coil for receiving and transmitting electrical power with wireless coupling, capacitance sensitive to stress, and ceramic resonator to provide high-Q resonance. The high quality factor brought by ceramic resonator enables us to distinguish a large number of chips, and to sense the stress with high accuracy. The structure, the method of wireless signal detection, and basic experiments of tactile sensing are presented.

Human-friendly robots of new generation will require sensor skin that is soft and covering the whole body. But it would be very difficult to fabricate it with the traditional technology, because placement and wiring of a vast amount of sensor elements on the 3-dimensionally configured robot surface is laborious. We propose a novel method to fabricate such a sensor skin. The skin contains sensor chips which receive the electrical power and transmit the tactile signal without wires. The skin is configured in an arbitrary shape easily, and it is elastic and tough because each sensing element does not need any fragile wires. The principle and the experimental results are described.

In this paper, we propose a device to stimulate only the superficial mechanoreceptors in the skin, and report the feeling caused by the stimulus. We describe the principle of the selective stimulation using air pressure, and we show the selectivity is more advanced than that of our previous system using magnet chips which was presented last year. We experimentally confirmed that a sparse array of the superficial stimulators could display realistic touch on objects including finer virtual textures than the stimulator spacing.

The human feels various tactile feeling by touching and rubbing the object lightly. In this paper, we propose a method to display such tactile feeling with reality. We produce the feeling by selective stimulation to each kind of mechanoreceptors, using elastic transfer property of the skin. Our system is composed of four magnet tips attached on the skin in a line and precisely driven by four coils. The two driving modes, the common phase mode and reversed phase mode, stimulate the deep receptors and shallow receptors in the skin, respectively. The system could give several types of tactile feeling with reality. The principle and experimental results are shown.

In this paper we propose a new tactile sensing element, acoustic resonant tensor cell. The structure has only a spherical cavity in an elastic tactile sensor body with two fine ultrasound paths extended respectively to an ultrasound transmitter and receiver which are placed at the bottom of the elastomer. The acoustic resonant frequency of the air in the cavity has an explicit relation with the principal stresses around it, which is easily detected by the ultrasound transducers. The sensor is simple and elastic. The single structure presents useful tactile features of multidimensions. The principle and experimental results are described.

This paper describes a new tactile sensor using acoustic cell structure based on the detection of ultrasound wavefronts in a flexible medium. The acoustic cell consists of a 2/spl times/2 ultrasonic transmitter matrix and a 2/spl times/2 ultrasonic sensing matrix which are placed face to face with an interval of a few tens of wavelength. These cells are embedded in flexible spherical finger-tip-like body of a tactile sensor. First, we show an ultrasonic transduction principle to discriminate small deformation of the cell in five dimensions, i.e. 3D displacement and a pair of surface angles of the transmitter matrix relative to the receiver. We then describe a tactile sensor using a single element of the cell, and show that the sensor can measure: 1) 10 /spl mu/m displacement by 18.5 mm cell height, and 2) 0.001 rad change of surface inclination. We apply the sensor to a robot finger which can sense not only its contact force with arbitrary orientation but also predict the slip of the grasped object.

Proposes a new tactile sensory structure using integrated sensing elements which the authors call a tensor cell. It is located sparsely in a flexible body of a tactile sensor, and samples there the complete information of a stress tensor which requires six degrees of freedom to describe it. The authors clarify first the advantage of this architecture theoretically based on elasticity theory and matrix algebra. Then the design of the actual tensor cell and experimental results are described, and an application of it to contact surface characterization is shown.

This paper describes our primary study for a new type of tactile sensing devices which are based on instantaneous localization of acoustic emissions caused necessarily by touch and/or contact movement. We assume the sensor structure which consists of a flexible spherical fingertip-like body and a quadruple PVDF sound sensing matrix is placed at a center of the body. The PVDF matrix works as a wideband acoustic emission (AE) transducers which is capable to detect the arrival direction of a wave packet. Therefore it can resolve and localize multiple ultrasonic emissions at a sensor surface caused by a touch and slip. In order to realize this type of tactile sensor, we present the theory of wave generation at collision, and apply the newly developed sound localization algorithm for an auditory sensor. By assuming the use of this algorithm, and from several experiments under various contact and slip conditions, we show the following features and tactile information: 1) quick localization of touch and detouch, 2) sensation of texture under movement, and 3) quick detection of precursor of slip.>

A new tactile sensing algorithm based on the elastic transfer function of surface deformation is proposed. Utilizing the inherent mechanism of an elastic body, it is shown that only a pair of vertically separated pressure probes can determine a single dominant spatial frequency of a fixed surface being touched, and also an arbitrary spatial spectrum of a moving surface profile without knowing its speed. Theory of vertical sampling in the elastic body is presented. Several experimental results utilizing a pair of pressure probes embedded in a silicone rubber sensor tip are shown.>