Takayuki Iwamoto

Noncontact Tactile Display Based on Radiation Pressure of Airborne Ultrasound

This paper describes a tactile display which provides unrestricted tactile feedback in air without any mechanical contact. It controls ultrasound and produces a stress field in a 3D space. The principle is based on a nonlinear phenomenon of ultrasound: Acoustic radiation pressure. The fabricated prototype consists of 324 airborne ultrasound transducers, and the phase and intensity of each transducer are controlled individually to generate a focal point. The DC output force at the focal point is 16 mN and the diameter of the focal point is 20 mm. The prototype produces vibrations up to 1 kHz. An interaction system including the prototype is also introduced, which enables users to see and touch virtual objects.

Non-contact Method for Producing Tactile Sensation Using Airborne Ultrasound

This paper describes a new tactile device which produces stress fields in 3D space. Combined with 3D stereoscopic displays, this device is expected to provide high-fidelity tactile feedback for the interaction with 3D visual objects. The principle is based on a non-linear phenomenon of ultrasound, acoustic radiation pressure. We fabricated a prototype device to confirm the feasibility as a tactile display. The prototype consists of 91 airborne ultrasound transducers packed in the hexagonal arrangement, a 12 channel driving circuit, and a PC. The transducers which were in the same distance from the center of the transducer array were connected to form a 12 channel annular array. The measured total output force within the focal region was 0.8 gf. The spatial resolution was 20 mm. The prototype could produce sufficient vibrations up to 1 kHz.

Non-contact tactile sensation synthesized by ultrasound transducers

This paper describes a new tactile device which produces stress fields in 3D space. Combined with mid-air and/or 3D stereoscopic displays, this device provides high-fidelity tactile feedback for interaction with visual objects. The principle is based on a nonlinear phenomenon of ultrasound; acoustic radiation pressure. The fabricated prototype device consists of 324 airborne ultrasound transducers, and the phase and intensity of each transducer are controlled individually. The total output force within the focal region is 1.6 gf. The spatial resolution is 20 mm. The prototype can produce sufficient vibrations up to 1 kHz. An interaction system including the prototype is also introduced which tracks users hand and provides suitable touch feeling.

Airborne ultrasound tactile display

The authors and colleagues invented an ultrasound-based noncontact tactile display in 2008 and have been developing this technology since then. It is suitable for gesture input systems and aerial imaging systems because no physical contact is required to provide haptic feedback. An ultrasonic phased array generates a focal point of airborne ultrasound to press the skin surface. The amplitude modulation of ultrasound provides vibrotactile stimulation covering the entire frequency range of human tactile perception. The position of the focal point is computationally controlled to follow users’ hands and/or provide a trajectory of stimulation. While this technology was originally invented as a tactile display, a wide variety of other applications has been recently reported that exploit noncontact force generated at a distance. Examples include noncontact measurement by pressing or vibrating objects, levitation and manipulation of small objects, and actuation of fragile or soft materials. The present chapter describes the background, principles, systems, and applications of this ultrasonic technology.

Two-dimensional Scanning Tactile Display using Ultrasound Radiation Pressure

In this paper, we propose a new tactile display which produces spatio-temporal stress patterns on a 2-D plane. The first prototype of the display consists of an octagonal arrangement of ultrasound linear arrays. Each array has 40 pieces of PZT(lead zirconate titanate) transducer. The 320 channel driving circuit was designed to produce 1000 frames of 2-D stress patterns per second. The 2-D stress patterns can cover 1cm by 1cm area. Simulation studies were carried out to examine the adequacy of the proposed design. It showed that the octagonal arrangement can produce a well-focused force spot to be scanned in the display area. The results were satisfactory compared to other polygonal arrangement. Several initial results on the 2-D prototype are also discussed.

Finger Ring Tactile Interface Based on Propagating Elastic Waves on Human Fingers

We propose a new tactile device which measures several DOF vibrations propagating along the finger. The device can be used both as a tactile sensor and human-machine interface. In this paper, as a pilot experiment, we carried out experiments on the identification of contact positions by using 2 DOF vibrations. It was shown that with a 2-axis accelerometer placed on the backside of the proximal phalanx, tapping on distal phalanx and middle phalanx can be discriminated

Two Dimensional Stress Reproduction Using Ultrasound Tactile Display

We proposed a new tactile display which produces spatio-temporal stress patterns on a 2D plane. In this paper, the first prototype is reported. The display consists of eight ultrasound linear arrays arranged so that the PZT pieces were concentric octagons. In order to produce 2D spatio-temporal stress patterns, the focal point of ultrasound was scanned over the display surface. We measured the waveform of the sound pressure at the focal point and the spatial distribution of the radiation pressure around the focal point. The data showed that the temporal and spatial property of the display were sufficiently fine for our method for producing 2D spatio-temporal stress patterns

Measuring finger peripheral signal based on electrical synchronization

In this paper, we propose a method to measure tactile nerve signals on the skin noninvasively. The natural tactile nerve signals generated by mechanical touches are hidden behind thermal noises on the skin. In our method, we observe the tactile signals while synchronizing the firing by electrical stimulation. We expect the power of synchronized nerve signals can exceed the thermal noise. Synchronization is realized simply by stimulating mechano-receptors with electrical impulses. After the impulse, the stimulated receptors cannot fire until the refractory period ends. Then all receptors under over-threshold stress are expected to fire simultaneously.

1A2-A08 Tactile Interface using multi DOF vibration on human finger

1. はじめに 人間が触覚を用いて,対象の機械的性質に関する情報を得 る際には,まず触動作を行い,対象との接触により皮膚を変 形・振動させ,それをその直下の皮膚内部にある機械受容器 により計測している.もし,この変形・振動を,対象との接 触状態を妨げることなく測定することが可能であれば,使用 者の感覚を阻害することがなく,使用者が得ているのと同等 の触覚情報を得られるセンサデバイスが実現できると考えら れる.このようなセンサの先行研究としては,Mascaro ら[1][2] による,爪色の変化を利用し指先にかかる力,および指関節 角を推定した事例がある. 我々は,触動作に伴い生じる,指の振動,および指全体の 移動を取得する,指輪型のデバイスを提案する.このデバイ スは,指の根元に装着し,触動作により生じる複数の振動モ ードを取得する.異なるモードの振動や指の移動情報を利用 することにより,接触位置の定位や,対象テクスチャに関す る情報などが得られると考えている. また,このようなデバイスは,触覚情報の取得のみではな く,情報入力インターフェイスとしても用いることが可能で ある.Fukumoto ら[3]は UbiButton というデバイスを提案して いる.UbiButton は手首に取り付けた加速度センサにより指先 に加えたタッピングを検知し,タッピングの回数やリズムを 入力コマンドして解釈するデバイスである.我々の提案する デバイスは複数の振動モードを利用して接触位置定位を行う ことで,指上に仮想のボタン群を配置し,利便性を向上させ ることが可能であると考えられる. 本稿では,3 軸加速度センサを利用した簡便な試作機を用い て,このデバイスの情報入力インターフェイスとしての可能 性を示す.指の先端を叩いた場合と中節を叩いた場合との判 別を,3 軸の出力のうち 2 軸分の出力を利用して行った.

2P2-B25 Two-Dimensional Scanning Tactile Display Using Radiation Pressure by Multiple Acoustic Linear Arrays

In this paper, we propose a new tactile display which produces spatio-temporal stress patterns on a 2-D plane. We fabricated the first prototype. The prototype display consists of eight ultrasound linear arrays. Each array has 40 pieces of PZT transducer. The arrays were arranged so that the PZT pieces were concentric octagons. We measured the spatial distribution of radiation pressure and confirmed that the focal point was successfully produced and the spatial resolution was about 1.5 mm.