Shunsuke Yoshimoto

Development of a spatially transparent electrotactile display and its performance in grip force control

An important function for a tactile navigation system of a handheld tool, such as a surgical scalpel, is the spatial transparency of the device. This paper proposed a new tactile display that can augment touch sensation at the finger pulps without the need for a stimulator between the tool and the finger pulps. We utilized transcutaneous electrical nerve stimulation at the middle phalanx of a finger to separate the stimulated and the perceived areas. In order to verify the effects of the spatial transparency, the performances of grip force control were examined. The results indicated that the proposed display was effective in helping the user to maintain the stable control of the grip force when using a handheld tool.

Tactile mapping approach using electrical stimulus pattern

The fine concavo-convex shape of the object surface is a critical component that determines its texture. A previous electrotactile display could not tactually present fine concavo-convex objects but only a line pattern on the plane. In this study, the authors proposed a physiology-based tactile mapping method by formulating nerve activities that stem from a mechanical stimulus. The proposed electrical stimulus allows a human to perceive a concavo-convex shape. A stimulus frequency coded the skin displacement given by a concavo-convex shape and represented the adaptation of receptors with exponential approximation. As an example of tactually presenting a concavo-convex shape, roughness was introduced by using a Brownian surface, which enables a user to touch a surface of varying degrees of roughness with a developed tactile display mounted on a computer mouse. The results of subjective experiments showed a statistical difference among the perceived roughness of displayed rough surfaces. This study concluded that the proposed tactile mapping method was effective to present a touch sensation for concavo-convex shapes corresponding to a stimulus frequency below 100 Hz.

Material Roughness Modulation via Electrotactile Augmentation

Tactile exploration of a materials texture using a bare finger pad is a daily human activity. However, modern tactile displays do not allow users to experience the natural sensations of a material when artificial sensations are presented. We propose an electrotactile augmentation technique capable of superimposing vibrotactile sensations in a finger pad, thereby allowing the texture modulation of real materials. Users attach two stimulus electrodes to the middle phalanx of a finger and a grounded electrode at the base of the finger in order to evoke nerve activity. This paper evaluates the proposed electrotactile augmentation for roughness modulation of real materials. First, we introduce the principle of the electrotactile display, which presents artificial sensations at the finger pad. We then confirm that the perceived frequency of mechanical vibration at the finger pad can be shifted using electrotactile augmentation. Finally, we discuss a user study, wherein participants rated the roughness of real materials explored using the proposed system. Experimental results indicate that fine- and macro-roughness perceptions of real materials can be altered using electrotactile augmentation.

Roughness Modulation of Real Materials Using Electrotactile Augmentation

In this paper, we present a roughness modulation technique that employs electrotactile augmentation to alter material texture perception, which is conducted through mechanically unconstrained touch. A novel electrotactile augmented reality system that superimposes modulating nerve activity onto afferent nerves at the middle phalanx of a finger is described. We conducted a user study in which participants were requested to rate the roughness of real materials that were explored using the system. The results indicated that participants could perceive the modulated fine- and macro-roughness via the electrotactile augmentation.

Haptylus: haptic stylus for interaction with virtual objects behind a touch screen

Tablet PCs and smartphones rapidly become popular nowadays. People can touch objects on the touch panel display of the tablet PC or smartphone, but only get sensation of touching the surface of the display. Recently, some systems capable of inserting themselves into the display by using retractable stylus have been proposed. Beyond [Lee and Ishii 2010] is one of these systems. It consists of a retractable stylus, a table-top display, an infrared marker and a camera set at an environment. A virtual tip of the stylus is rendered when the retractable stylus is pushed to the table-top display. The head position of the user is detected by the infrared marker and the camera, and the virtual objects and the tip of the stylus are rendered properly according to the heads position. The system enables the user to interact with a virtual object under the table. However, the stylus dose not shrink or extend automatically because the stylus dose not have any actuators such as a motor. So the user is unable to feel the haptic sensation from the virtual object. It is necessary for the user to perceive the force from the virtual object to interact with the object more realistically. Another limitation is the fact that the system is stationary. ImpAct [Withana et al. 2010] is another interaction system with a smartphone and a retractable stylus. The force feedback is represented by simply stopping the shrinkage of the stylus. However, the system gives only the rigid force feedback without tactile sensations. And the system does not give a user the tactile sensation from the virtual objects. In addition, the system does not consider the viewpoint of the user.

Noninvasive simultaneous measurement of blood pressure and blood flow velocity for hemodynamic analysis

We describe a noninvasive and simultaneous measurement method of beat-by-beat blood pressure and blood flow velocity waveforms in the radial artery using tonometry and Doppler flowmetry. We conducted a subjective experiment in which hold-down pressure of tonometry was controlled for determining optimal hold-down pressure and the measurement accuracy under the optimal hold-down pressure was evaluated. As a result, blood pressure and blood flow velocity could be measured simultaneously without the influence of the hold-down pressure on the blood flow velocity. It was possible to analyze hemodynamic indicators, such as wave intensity and vascular impedance, with blood pressure and blood flow using the system. The proposed system for detecting unexpected fluctuations in blood pressure and the involved mechanisms may contribute to the treatment of cardiovascular diseases.We describe a noninvasive and simultaneous measurement method of beat-by-beat blood pressure and blood flow velocity waveforms in the radial artery using tonometry and Doppler flowmetry. We conducted a subjective experiment in which hold-down pressure of tonometry was controlled for determining optimal hold-down pressure and the measurement accuracy under the optimal hold-down pressure was evaluated. As a result, blood pressure and blood flow velocity could be measured simultaneously without the influence of the hold-down pressure on the blood flow velocity. It was possible to analyze hemodynamic indicators, such as wave intensity and vascular impedance, with blood pressure and blood flow using the system. The proposed system for detecting unexpected fluctuations in blood pressure and the involved mechanisms may contribute to the treatment of cardiovascular diseases.

Palm+Act: operation by visually captured 3D force on palm

Recently, there has been considerable interest in technologies that appropriate human body parts, especially the skin, as an input surface for human-computer interfaces. Since human skin is always available and highly accessible, such on-body touch interfaces enable the control of various systems in ubiquitous environments. An interface utilizing skin as an input surface provides a mobile input system that does not require dedicated control devices for a specific system. There are many researches that demonstrate the concept of on-body touch interaction with a ubiquitous sensing device [Harrison et al. 2011].

Superimposed skin pressure sensor

Unconstrained sensing of human-environment interaction is one of the most important technology which is expected to provide ubiquitous interfaces and high fidelity motion analysis systems as well as stress-free bioinstrumentation. Unconstrained tactile sensing is a challenging topic because tactile sensing devices are inherently required to mediate between the human and an object [Dahiya et al. 2010]. Therefore, it is still difficult to obtain human behavioral information without disturbing touch conditions.

Unobtrusive tactile sensing based on electromechanical boundary estimation

Unobtrusive tactile sensing is an important yet challenging topic for medical and robotic fields. We proposed a novel tactile sensing technology for obtaining the force of an interaction and the position at which it makes contact with an object of arbitrary shape without any mechanical obstructions. The proposed sensing method is based on electromechanical boundary estimation from the potential distribution, which is related to the contact state of the two objects with a potential applied. To evaluate the sensing method, we investigated the error of positional estimation and the relationship between force and sensor output. The experimental results indicated that the contact position can be estimated with a correctable systematic error several mm.We also confirmed a high correlation between the interacting force and the system output.

Finger motion capture from wrist-electrode contact resistance

Hand motion capture is an important yet challenging topic for biomechanics and human computer interaction. We proposed a novel electrical sensing technology for capturing the finger angles from the variation of the wrist shape. The proposed device detects the signal related to the wrist-electrode contact resistances, which change according to the variation of the wrist shape accompanying finger movements. The developed sensing device consists of a wrist band, sixteen electrodes and a sensing circuit of contact resistances. We investigated the relationships between the finger angles and the system outputs by using a glove-type joint angle sensor. As a result, we confirmed high correlations of the system outputs with the finger angles for several electrodes. Therefore, we conclude that the proposed system can be used for the estimation of the finger joint angles.