Ryuta Okazaki

Vibrotactile and pseudo force presentation using motor rotational acceleration

Linear vibration actuators such as the Force Reactor from Alps Electric Co. or the Haptuator from Tactile Labs Inc. are actively used to present numerous tactile sensation to the fingertip. They have high responsiveness compared with conventional eccentric rotating mass vibration motors, and are also able to produce pseudo-haptic illusions when asymmetric signals are applied. However, this type of actuator has certain design challenges, such as resonance via the spring attached to the vibration mass, and limited acceleration amplitude at low frequency because of the limited travel distance of the mass. In our study, we propose a new haptic presentation method using the rotational motors counterforce that occurs during acceleration. We use the rotor of motor itself as the vibration mass, so the mass can move indefinitely without limitation. This paper reports on the use of a DC motor as a vibration actuator. The results show that the response time of a DC motor is about 3 ms, which is faster than current linear vibration actuators. The peak amplitude of vibration is at a low frequency (about 40 Hz). We also found that a DC motor is able to provide a rotational pseudo-force sensation. The combination of vibration and pseudo-force produced by a single motor allows a wide range of haptic presentation to the fingertips.

FinGAR: combination of electrical and mechanical stimulation for high-fidelity tactile presentation

It is known that our touch sensation is a result of activities of four types of mechanoreceptors, each of which responds to different types of skin deformation; pressure, low frequency vibration, high frequency vibration, and shear stretch. If we could selectively activate these receptors, we could combine and present any types of tactile sensation. This approach has been studied but not fully achieved. In our study, we developed FinGAR (Finger Glove for Augmented Reality), in which we combined electrical and mechanical stimulation to selectively stimulate these four channels and thus to achieve high-fidelity tactile sensation. The electrical stimulation with array of electrodes presents pressure and low frequency vibration with high spatial resolution, while the mechanical stimulation with DC motor presents high frequency vibration and shear deformation of the whole finger. Furthermore, FinGAR is lightweight, simple in mechanism, easy to wear, and does not disturb the natural movement of the finger, all of which are necessary for general-purpose virtual reality system.

Vibrotactile stimulation can affect auditory loudness: a pilot study

Very few cases have been reported where tactile stimulation affects auditory perception. In this pilot study, we asked volunteers to compare the loudness of combinations of vibrotactile and auditory stimuli. A 50-300 Hz band-limited pink noise signal was used as the stimulus in the two modalities, simultaneously heard through headphones and felt in the hands to be compared to when it was heard only. On average, the same auditory stimulus was judged to be about one dB louder when it was simultaneously heard and felt rather than when it was heard only. This condition could be interpreted as having enhanced the perception of loudness by a whole jnd.

Judged Consonance of Tactile and Auditory Frequencies

With the aim of augmenting auditory sensation by tactile stimuli, we investigated cross-modal relationships between the two modalities, focusing on frequency. The results showed that frequency consonance between tactile and audio stimuli depends on the relationship between harmonics, in a manner similar to auditory waves, but with broader peaks.

Change in the Amount Poured as a Result of Vibration When Pouring a Liquid

Visual and tactile stimulation is known to affect the experience of eating and drinking. In this study, we focused on the vibration of a Japanese sake bottle when used to pour liquid. We manufactured a device that can be attached to the neck of any plastic bottle and investigated how beverage consumption was affected by the vibration. We found that presentation of the vibration affected the amount of poured beverage when visual and sound cues were masked.

Altering Distance Perception from Hitting with a Stick by Superimposing Vibration to Holding Hand

Distance perception by hitting objects with a handheld stick is an important cue for people with visual impairments who use a white cane in daily life. In a previous paper, we found that adding vibration to the thumb side of the cane shortened the perceived collision distance more than adding vibration to the little-finger side, which partly agrees with our hypothetical model. In this paper, we conducted a similar experiment, changing the real distance between the palm and the object to explore the robustness of our hypothetical model. The experimental results showed that perceived collision distance shortened regardless of the real distance, but may be easily induced when the object is placed far from the palm.

[D07] Mutual referral of thermal sensation between two thermal-tactile stimuli

When thermal stimulation is applied to one location on the skin and tactile stimulation is presented to another, we perceive the thermal sensation on the latter location as well. While this illusion, known as thermal referral, has been well studied, there is little knowledge on the mutual interaction among multiple thermal-tactile stimuli. We conducted an experiment for verifying the mutual interaction of thermal referral between two thermal-tactile stimuli on forearm and found that there are strong asymmetry between the stimuli locations and between the thermal conditions. The elbow side perceives more thermal referral and synthetic heat (thermal grill illusion) than the wrist side. The warm sensation tends to spread from the periphery toward the center, whereas the cool sensation tends to spread from the center toward the periphery.

Detection of tangential force for a touch panel using shear deformation of the gel

Many capacitive touch panels detect the position and contact area of the user finger, and can estimate the vertical force from the change in the contact area. However, they cannot detect and measure the tangential force. This research aims to enable the measurement of tangential force using a gel layer, which deforms when a tangential force is applied. By measuring the finger motion of the user, we can estimate tangential force from the gel spring ratio. Using this input method, any part of the touch panel surface becomes a joystick, or virtual objects can be modeled by deforming them with the fingers.

CollarBeat: whole body vibrotactile presentation via the collarbone to enrich music listening experience

There are numerous proposals for whole body tactile displays that aim to improve the sense of immersion in audio contents. However, these devices commonly have problems, such as long setup times due to numerous actuators, and user confinement to the system. To address these issues, we proposed to present the vibration to a wide area of the body via bone conduction. In this paper, we first investigated whether presenting vibration to the bone really contributes vibration transmission to wider areas of a users body. Next, we performed a psychophysical experiment to evaluate subjective vibration feeling with music listening experience using our setup. Results suggest that presenting vibration through the collarbone induces vibration transmission more widely through the users body and enhances subjective music listening experience.

Presentation of Softness Using Film-Type Electro-Tactile Display and Pressure Distribution Measurement

Electro-tactile display has simple mechanical structure, and it can present tactile stimulus. However, electro-tactile display lacks feedback corresponding to touching motion. In this research, we developed a device that combines an electro-tactile display and pressure distribution sensor. The device not only solves the problem of unnatural electrical sensation, but also enables the expression of haptics-related physical characteristics, such as softness and viscosity. In an experiment, we validated whether the presentation of softness sensation is possible. As a result, presentation of softness sensation is confirmed that is possible by using pressure distribution measurement.