Haptics（触覚学） - 東京工業大学長谷川晶一研究室

Virtual reality and interaction
Haptics（触覚学）
Shoichi Hasegawa
http://haselab.net /class /vr/
This slide is based on “Advanced interactive system”
by Prof. H. Kajimoto in the University of Electro Communications
http://kaji-lab.jp /ja /index.php?people /kaji /interactive
Haptics (触覚学)
Studies on touch （触れることの学問）
Haptic perception
Somatosensory system
Haptic interaction
Haptic technology
Related words
Tactile (触覚の)
Touch (触れること)
Somatosensory system（体性感覚）
Responses to changes on the surface or internal
state of the body.
Including
Thermoreceptors(温度受容器)
Mechanoreceptors(機械受容器)
Nociceptors(侵害受容)
In
Skin(皮): Cutaneous receptors (皮膚受容器)
Skeletal Muscle(骨格筋), Tendon(腱), Joint(関節)
Internal organs(内蔵)
Cardiovascular system(循環器系)
Cutaneous receptors (皮膚受容器)
Skin Strunture (Hairless Parts)
Skin surface
表皮／Epidermis
機械受容器：機械的変形に応答
Mechanoreceptor: Sense Mechanical
Deformation
浅部／Shallow part
マイスナー小体／MeissnerCorpuscle
メルケル細胞／Merkel Cell
真皮／Dermis
皮下組織／
Deeper Tissue
深部／Deep part
ルフィニ終末／Ruffini Ending
パチニ小体／Pacinian Corpuscle
その他／Misc
自由神経終末（痛覚、温度感覚）
FreeEnding (Pain, Temperature)
メルケル細胞／Merkel Cell
•皮膚下0.9mmに密に存在．
•唯一の細胞性受容器．神経とシナプス接合
•静的な歪に応答
•発火頻度は歪の大きさに比例
•単独の活動では純粋な圧覚を生成
•Densely Populated at 0.7 - 0.9mm depth.
•Sense Static Deformation.
•Pulse Frequency is Proportional to Deformation.
•When activated, Pure Pressure Sensation is generated.
マイスナー小体／Meissner Corpuscle
•皮膚下0.7mmに密に存在．
•低周波振動(15-100Hz)に応答（共振30Hz)
•発火周波数～振動周波数
•単独の活動では振動感覚，パタパタ感を生じる
•Densely populated at 0.5 – 0.7mm depth.
•Sense Low Frequency Vibration (15-100Hz)
•Has Resonant Frequency （30Hz)
•Pulse Frequency ～Vibration Frequency
•Single Activity Generates “Flutter” Vibratory Sensation
パチニ小体／Pacinian Corpuscle
•皮膚下2mm以上の深部にまばらに存在．
•高周波振動に応答(60-800Hz)(共振250Hz)
•発火周波数～振動周波数
•単独の活動では音叉に触れたような振動感覚，指全体の痺れ
•Sparsely populated at deep region (2mm～)
•Sense High Frequency Vibration (60-800Hz)
•Has Resonant Frequency (250Hz)
•Pulse Frequency～Vibration Frequency
•Single Activity Generates “numb” sensation, just like touching a tuing fork or speaker
ルフィニ終末／Ruffini Ending
•皮膚下2mm以上の深部に疎らに存在．
•静的な横ずれに応答
•発火頻度は横ずれの大きさに比例
•単独の活動では感覚を生じない
•Sparcely Populated in a deep region (2mm～ depth)
•Senses Static Horizontal Deformation
•Pulse Frequency is Proportional to Horizontal Deformation.
•Single activation does not generate sensation
Threshold [μm]
時間的役割分担／Temporal Roles
Frequency[Hz]
Merkel
Meissner
Pacinian
•Merkel：直流成分／圧力
•Meissner：低周波成分／速度
•Pacinian：高周波成分／加速度
•Merkel：DC / Displacement & Pressure
•Meissner：Low Freq. Vibration / Velocity
•Pacinian：High Freq. Vibration / Acceleration
空間的役割分担／Spatial Roles
Meissner
Merkel
Pacinian
•Merkel：細かいパターン／Small Pattern
•Meissner：皮膚上の細かい動き／Small Area Movement
•Pacini：広い面積の動き／Large Area Movement
各機械受容器の役割分担
We only see through narrow slit
Spatial
Resolution
Merkel
Meissner
Pacinian
Temporal
Resolution
ポイント：時間的，空間的な相補性
We combine “Spatially Fine, but Temporally Rough” sensation and “Spatially
Rough, but Temporally Fine sensation.
In other words, we “see” the world through very narrow slit.
皮膚構造と受容器
Skin Structure and Mechanoreceptors
•表皮：硬い
•真皮：柔らかい
•MerkelとMeissnerは境界に存在
•Epidermis：Hard
•Dermis：Soft
Merkel and Meissner are at the interface of
the two layers.
Stress is Concentrated at Merkel
Strain is Largest at Meissner
Gregory J. Gerling, “Fingerprint lines may not directly affect SA-I mechanoreceptor response,” Somatosensory and Motor Research 2008.
形状は主にMerkelによってコーディングされる
Shape is mainly coded by Merkel Cells
Merkelの活動
Meissnerの活動
Vibration Amplitude(μm)
周波数は受容器の活動比率でコーディングされる
Frequency is mainly coded by combination of receptor
activities.
人間の振動知覚閾
Frequency
Vibration Amplitude(μm)
周波数は受容器の活動比率でコーディングされる
Frequency is mainly coded by combination of receptor
activities.
人間の振動知覚閾
※
Frequency
※振動子が小さいとPaciniの「空間加算」効果が無くなり、高周波が感じにくくなる
If the vibrator size is small, high freq. threshold rizes, because “spatial
summation effect” of Pacinian corpuscle is reduced.
その他の触覚／Other cutaneous sensations
無毛部
有毛部
Glabrous part
Hairy part
皮膚表面付近の自由神経終末（C繊維）
Free nerve ending near skin surface （C fiber）
温度感覚：冷繊維と温繊維／Temperature sensation by two fibers.
痛覚：鋭痛と鈍痛はAγ繊維とC繊維が担当／Pain sensation by two fibers
有毛部／Hairy skin
毛包受容器／Follicle Receptor
毛の根元を取り巻き，毛が曲がるときのみ活動（速度検出）
ただしこれに代わり，Meissner小体は無い．
Activated by low frequency vibration, substituting Meissner corpuscle
信号伝搬速度／Conduction Velocity
有髄神経
Myelinated
無髄神経
Unmyelinated
name
diameter(μm)
velocity(m/s)
Aα
15
100
Many muscle nerves
Aβ
8
50
Many sensory nerves
Aγ
5
20
Some muscle and
sensory nerves
Aδ
3
15
Fast pain
C
0.5
1
Slow pain, heat, cold
sensation, etc
• Rule: Thicker = Faster
脊椎
role
• Myelinated Axon: Invention of vertebrate animals
(animals with back-bone).
• Other animal’s strategy: Thicker the better.
•
ex）Squid’s gigantic nerve (diameter: 0.5mm)
軸索上の電位伝搬／Axonal Transmission
Dendrite
Cell Body
Nerve Axon
Nerve Ending
Chemical “ion” is
exchanged via membrane.
Ion exchange propagates.
Voltage Difference
~70mV
軸索のタイプ／Axon types
Axon length: Reaches to 1m.
ミエリン髄鞘／Myelin Sheath: Insulator
Electrical Current is limited to very small “gap” (ランビエ
絞輪／Ranvier Node)⇒Very Fast “Skip”
有髄神経：Myelinated axon=very fast
無髄神経：Unmyelinated axon = very slow
どうやって調べる／How we know?
By using needle, we can directly measure nerve
activities. Vallbo, “Sensations evoked from the glabrous skin of the human hand by electrical
stimulation of unitary mechanoseisitive afferents,” Brain Res., 1981.
Procedure
(Medical Doctor’s License Required)
(0)See where the nerve bundle is. (by ultrasonography)
(1)Insert a needle (φ0.1mm), which is connected to Amp&Speaker
(2)Identify Location and Type of Receptor by the Sound.
(3)Do Experiment on that Location.
50μV
Antagonistic Muscles
拮抗筋
•Two muscles are responsible for one joint. Isn’t it redundant?
•Answer1: Muscle can only exert force when it shrinks.
•Answer2: By Two muscles, “Force” and “Impedance(softness)” is
independently presented.
•Muscle A – Muscle B = Exerted Force
•Muscle A + Muscle B = Joint Softness
23
Receptors around Muscle and Joint
Muscle Spindle
筋紡錘
Inside Muscle
React to Muscle Length Change
=Velocity
Golgi Tendon Organ
At the Tendon (Muscle-Bone
Connection)
React to Muscle Force
=Force
Joint Mechanoreceptor
Inside Joint
React to Joint Angle
=Position
Efference copy (遠心性コピー)
Copy of motor commands from brain to muscle
Body schema (Body image, 身体図式,身体像 = One’s
perception on own body) is generated from both
somatosensory system and efference copy.
Tactile Perception & Illusion
触覚の（狭義の）錯覚：錯触
Tactile Illusions
The Aristotle(アリストテレス) illusion
Barber Pole Illusion
Motion Aftereffect (滝の残効)
Apparent motion (仮現運動)
Phantom Sensation(Funneling)
(ファントムセンセーション)
Velvet illusion (ベルベットイリュージョン)
Rubber hand illusion(ラバーハンドイリュージョン)
…etc
特に近年，触覚研究の発展に伴って増加．
Recent works revealed new tactile illusions
Tactile Illusion similar to vision: Apparent motion
視覚で類推できる錯触例：仮現運動
Intensity of stimulus
Ａ
Ｂ
Stimulus A
Time
Stimulus B
Tactile Illusion similar to audio: Phantom Sensation(Funneling)
聴覚で類推できる錯触例：ファントムセンセーション
Stimulus A
Perceived
position
Stimulus B
短パルス刺激で発生
複数刺激子の間に知覚
位置は移動できる
Generated by short pulses
Image generated between
stimulators
Position can be controlled
Ａ
Ｂ
Time
触覚独自の錯触:ベルベットイリュージョン
Tactile Unique Illusion: Velvet Illusion
荒い網の目（テニスラケットなど）を両手で挟み，
前後に動かすと，モワッとしたベルベット感を生じる．
Sandwiching coarse mesh of a net, such as tennis
racket by two hands, and moves. Then, smooth
surface like velvet is felt.
触覚独自の錯触:サーマル・グリル・イリュージョン
Tactile Unique Illusion: Thermal Grill Illusion
Skin
Hot Cold H
C
H
C
近い距離で温感と冷感を同時に提示すると痛覚を生じる
Close presentation of hot and cold temperature generates pain
sensation.
実験上、皮膚を損傷せずに痛みを生成するためによく用いられる
Used for the generation of pain sensation without skin damage.
Haptic Perception Mechanism
(other than skin sensation)
Haptic Illusions
Vision + Haptics
Cutaneous + Haptics
Haptic Illusions (part of. other than purely cutaneous illusion)
錯触（皮膚感覚による錯触のぞく）の一部
Vision + Haptics
Cutaneous（皮膚感覚） + Haptics
Vision Induced Haptics(1):
Size-Weight Illusion
同じ重量であれば、小さいものをより重く感じる。
If two objects are the same weight, smaller one felt hevier.
iPadやMacBookAirを「意外に重く」感じる理由？
Vision Induced Haptics(2):
Pseudo-Haptics
視覚的な動きによって、触覚的な抵抗感を感じる。マウス
カーソルの動きを遅くしたときのブレーキ感。
Visual motion induces haptic resistance. (ex) Braking
feeling when mouse cursor is suddenly slowed down.
http://www.irisa.fr/tactiles/index-eng.html
PseudoHaptics
http://www.youtube.com/watch?v=F6h_19PxKO8
Vision Induced Haptics(3):
Rubber Hand Illusion
見えていない実際の手に触覚的な刺激を与え、同時にゴムの
手に視覚的な刺激を与える。しばらくするとゴムの手が自分
の手であるように感じる
Watching a rubber hand being stroked synchronously
with one’s own unseen hand causes the rubber hand
to be attributed to one’s own body, to “feel like it’s
my hand.”
Botvinick, M., & Cohen, J.: Rubber hands "feel" touch that eyes see, Nature, 391, 756 (1998)
Armel , K. C. , & Ramachandran, V. S. : Projecting sensations to external objects: evidence from skin
conductance response, Proc R Soc Lond B Biol Sci, 270, 1499-1506 (2003)
Rubber Hand Illusion
https://www.youtube.com/watch?v=nzF_DfOafKw
Reduction of phantom pain
by mirror box
幻肢痛：手足を失った後に、切断部位は問
題ないのに激しい痛みを感じる現象。
ひとつの仮説：失った手足の脳内座標(ボ
ディマップ)が狂い、体内に「食い込む」こ
とで脳内で痛みシグナルが発生。姿勢をも
とに戻せないために痛みを生じ続ける。
Phantom pain: After one’s
hand/arm/leg was removed, pain
seems to occur from the removed site.
One hypo.: Removed limb’s body map
in the brain comes wrong, and the
brain generates pain signal.
ミラーボックスセラピー
Mirror box therapy
ミラーボックスを使い、両手を使っていることを
イメージさせることで、脳内で無いはずの手を
動かすことができる。これにより幻肢痛を劇的
に低減できる。
Using mirror box, patients can “move” their
lost limb in their brain, so that the phantom
pain is dramatically reduced.
(参考)視覚による痛みの低減
Visually small reduces pain
反転させた双眼鏡を使って痛みの患部を観察すると痛みが減る。
Observing the pain region with reverted binocular, the pain is reduced.
G. Lorimer Moseley, Timothy J. Parsons1 and Charles Spence “Visual distortion of a limb modulates the pain and swelling
evoked by movement,” 2008
皮膚感覚によるハプティック錯覚 Cutaneous Induced Haptics：
ピノキオ錯覚-1／Pinocchio Illusion-1
自分の前の人の鼻を撫でつつ、自分の鼻も撫で
ると、１分程度で半分程度の人が自分の鼻が伸
びたように感じる。Rubber Hand Illusionの
視覚無し版として理解可能
皮膚感覚によるハプティック錯覚 Cutaneous
Induced Haptics：ハンガー反射／Hanger Reflex
側頭部圧迫によって外力を知覚
頭部の回旋をも誘発
Front temporal pressure induces
“rotational” force perception.
Rotation itself is induced.
Illusion on shape recognition by
motion
Ando H. et al., Novel Tactile Contour Presentation: Embossed Touch Display, ACM SIGGRAPH 2006 Sketches
While rubbing a shape, the shape is moved synchronously.
Recognized as changing of shape instead of motion.
→ Integration of motion on skin and hand motion is rough
皮膚圧迫による外力錯覚
Illusory external force by pressure
http://reality.ei.tuat.ac.jp/
稲葉、藤田：指先圧迫による擬似反力提示装置の提案と試作,日本バーチャルリアリティ学会論文誌,2007.
Minamizawa, Haptic Interface for Middle Phalanx Using Dual Motors, EuroHaptics, 2006.
皮膚の圧迫により、本来は外力がない状況で外力を感じる
Simple pressure sensation is perceived as external force.
Haptic display
Haptic display’s target
Shape
Texture
Temperature
Material
Force
Internal structure/mechanism
Dynamics
Difference is scale
However, can use
different method
because of human
perception.
Shape display’s strategy
Reproduce object shape
From Xmen2000 cinema
Reconstruct Object Shape
遭遇型／Encounter Type
Reconstruct Hand Shape
装着型 / Wear Type
把持型 / Grip Type
Reproduce object shape
http://www.youtube.com/watch?v=7qOaGIgSAE0
Tactile Display for the blind
大量の高密度実装→アクチュエータの小ささ、安さが鍵
Numerous, dense arrays→Actuator needs to be small and cheap
より細いアクチュエータ → 形状記憶合金
Thinnest actuator → SMA
Coil-Type SMA（Shape Memory Alloy）
Extremely thin and moves large
Shrink when heated
Lumen (Ivan Poupyrev, 2005)
Pop UP ! (Masashi Nakatani, 2004)
Reproduce Skin Deformation
“Carpet is expensive. Shoes are enough!” Lets Wear.
Small and lightweight tactile
display (KAIST)
http://www.youtu
be.com/watch?v
=CT4WZexTloo
Problem: How can the actuator be so small and dense? (again)
Physical Telepresence
Force display by
Ultra Sonic's Sound pressure
Is Actuator really necessary?：
SandScape (Yao Wang et al., 2002)
Projector
Hot mirrio
IR camera
Sandbox （beads）
IR light source
http://tangible.media.mit.edu/projects/sandscape/
How to reconstruct the world?
Reconstruct Shape
遭遇型／Encounter Type
High Cost, but free hand
True “Contact”=Natural Tactile Sensation
Reconstruct Hand Shape
装着型・把持型／
Wear Type, or Grip Type
Low Cost but must equip
Most Commercial Haptic Interface
遭遇型／Encounter Type
Active Environment Display (Tachi et al., 1994)
Encounter Type II TELESAR II master hand (2005)
Space between finger and display is kept
constant.
Flexion
Extension
 When Virtual Object contacts, it is displayed.
No Contact!
Syuhei Nakagawara, Hiroyuki Kajimoto, Naoki Kawakami, Susumu Tachi and Ichiro Kawabuchi: An EncounterType Multi-Fingered Master Hand Using Circuitous Joints, ICRA2005
How to reconstruct the world?
Reconstruct Shape
遭遇型／Encounter Type
High Cost, but free hand
True “Contact”=Natural Tactile Sensation
Reconstruct Hand Shape
装着型・把持型／
Wear Type, or Grip Type
Low Cost but must equip
Most Commercial Haptic Interface
Wear Type: CyberGrasp /CyberForce
http://www.youtube.com/watch?v=Td7QcAgCtWE&feature=fvw
Wear Type(２)SPIDAR-8(WALAIRACHT et al., 1999)
(left) 4 finger, (right) 4 finger
One finger is pulled by 3 wires
Somsak WALAIRACHT, Yasuharu KOIKE, Makoto SATO: `A New Haptic Display for Both-Hands-Operation: SPIDAR-8′, ISPACS’99
対向型多指触覚インターフェイス(Kawasaki et al.)
Five-Fingered Haptic Interface
HIRO, Kawasaki lab Gifu university
http://www.youtube.com/watch?v=XxlYY0xo4gk
How to reconstruct the world?
Reconstruct Shape
遭遇型／Encounter Type
High Cost, but free hand
True “Contact”=Natural Tactile Sensation
Reconstruct Hand Shape
装着型・把持型／
Wear Type, or Grip Type
Low Cost but must equip
Most Commercial Haptic Interface
Grip type(1)PHANToM (SensAble)
 Most Famous Haptic Interface with 6DOF
 Fingerstall type was developed, but most are pen-grip type
 最も有名なハプティックデバイス。6自由度をサポート
 指サックタイプも開発されたが多くはペングリップタイプ
Massie T. H., Salisbury J. K., “The PHANTOM Haptic Interface: A Device for Probing Virtual
Objects,”Symposium on Haptic Interfaces for Virtual Environmet and Teleoperator Systems, 1994.
Small but significant difference between wear type and grip type
装着型と把持型の小さくて大きな違い
装着型／Wear type：
指ごとにサポートする必要
Each finger must be supported
古典的VR/ Classical VR
把持型／Grip type：
｢ペン」等の類推の利く道具に対して力提
示（道具再現型）．指への力提示は間接的
Force is presented to “Tool”, and
presentation to hand is indirect.
現実的解/
Practical solution for many
applications
Grip type(1)PHANToM (SensAble)
http://www.youtube.com/watch?v=u9jdhUvOmMw
Omega (force dimension)
http://www.youtube.com/watch?v=Oh7saN3hI68
Falcon (Novint)
http://www.youtube.com/watch?v=mW70elK9Yrs&feature=related
• Very cheap haptic device is sold for gaming use
• 格安ハプティックデバイス。ゲーム用途で販売
Magnetic levitation:
Butterfly haptics
Stick with disk driven by electromagnet
Movable part
is light
Strong drive
→
Crisp feedback
Magnetic levitation:
Butterfly haptics
http://www.youtube.com/watch?v=cMi75SrDbsk
SPIDAR-G
HapticMaster (MOOG FCS)
http://www.youtube.com/watch?v=tgGEcE1VS6I
Van der Linde R.Q., Lammertse P., Frederiksen E., Ruiter B(2002) The HapticMaster, a new high-performance haptic
interface
•
産業用ロボット的なバックドライバビリティのない剛構造＋力センサ
• Rigid structure without back-drivability, like industrial robot. With force sensor
Make it light, or make it rigid?
軽く作るかしっかりつくるか?
back-drivability
Whether output shaft can be
moved by hand
出力軸を直接動かせるかどうか
As Human handles output shaft directly,
control method is closely related to
back-drivability
Ordinary gear
Back-drivable, but reduced if
gear ratio is higher (up to 50:1).
Worm gear
Not back-dribable.
Make it light, or make it rigid?
Light device：
Wire drive, low gear ratio
Back-drivable
Rigid device:
Industrial robot, etc.
High gear ratio, no back-drivability
React force sensor equipped between
handle and arm.
How to control “light” haptic interface
mx  f  cx  kx
Impedance based method
Measure grip position.
Output force according to the position and velocity.
As in the first step, position must be changed by the user,
the haptic interface must be back-drivable.
How to control “rigid” haptic interface?
mx  f  cx  kx
Admittance based method
Measure operator’s force
Calculate world’s behavior according to the force, and
change position of the grip.
Force sensor is necessary, but back-drivability is not. Rigid
robot such as industrial robot can be used.
Haptic displays utilizing haptic perception
characteristics
What is essential for bump sensation?
凹凸感にとって重要なものは何か
Force direction is more
important than vertical finger
position.
Gabriel Robles-De-La-Torre & Vincent Hayward: Force can overcome object geometry in the perception of shape
through active touch Nature 2001.
What is essential for bump sensation?
凹凸感にとって重要なものは何か
Face normal >> position
as a clue for convex/concave
characteristic on global shape.
Maarten W. A. Wijntjes, Akihiro Sato, Vincent Hayward, Astrid M. L. Kappers
Local Surface Orientation Dominates Haptic Curvature Discrimination, Trans. On Haptics, 2009.
Lateral(横向きの) haptic(force) display
Active type
Actively drive skin horizontally.
Passive type
friction force is controlled, and perceived by skin
motion.
Skin stretch
Small part of skin is stretched
Active type Lateral Display
•Lateral Vibration is achieved
by Micro-Machine
Hayward,”Tactile display device using distributed
lateral skin stretch,” ASME, DSC, 2000.
Tactile display device using distributed lateral skin stretch
http://player.vimeo.com/video/413506
Lateral force display by motor and string
http://www.youtube.com/watch?v=Prq9-uJSqSE
嵯峨他、剪断力を用いた2.5次元触覚ディスプレイにおける定量的凹凸感提示手法、VR学会大会2011
Passive type Lateral Display
Controlling friction coefficient by
ultrasonic vibration
Change surface friction by ultrasonic vibration
Squeeze film effect (スクイーズ効果)
Air pressure around vibrating
surface comes to higher than
other area.
Levitating on a thin air film
TPaD(Laura Winfield, 2007)
Passive type Literal Display
Using adhesion between skin and electrode by high voltage
高圧電極と皮膚の電気的吸引利用
Change normal force
Kaczmarek et al., “Polarity Effect in
Electrovibration for Tactile Display,” IEEE Trans.
Biomedical Engineering,, 2006.
Olivier Bau et al., “TeslaTouch: Electrovibration for
Touch Surfaces,” UIST2010
TeslaTouch (2010)
http://www.teslatouch.com/
Reproducing Receptor Activity by Strain Energy
ひずみエネルギー再現に着目した受容器活動再現
空気吸引による圧覚生成／Using air suction
吸引と押下で，受容器位置に生じる歪エネルギーが同じ→人は区
別できない
Suction and push produces the same amount of strain energy,
so that human cannot distinguish.
Makino “A cutaneous feeling display using suction pressure,” SICE Annu. Conf., 2003.
Electrical Muscle Stimulation
拮抗筋の電気刺激で抵抗力を提示
軽量。ただし刺激場所での触覚も生じる
Antagonist Muscle is electrical stimulated.
Light weight, but strong tactile sensation also give to the
stimulating area.
IVRC1993
機能的電気刺激
Functional Electrical Stimulation
http://www.youtube.com/watch?v=4HazUyV0X
主にリハビリテーションで用いられる。
日常生活の補助（＝長期的な刺激）にはなお課題。
Mainly used in rehabilitation.
Several problems remains for long-term stimulation.
(FIY) Power support by exoskeleton
http://sanlab.kz.tsukuba.ac.jp/r_hal.php
筑波大学山海研究室 HAL
General Electric “Hardiman” (1965)
Reproducing Nerve Activity by Electrical Stimulation
電気刺激により神経活動を再現
脳内解釈された刺激点
Sensation point
神経発火点
Stimulation point
• 利点：エネルギー効率／機械的脆弱性・共振特性から開放
• 課題：空間的なマッピング・選択刺激の実現
• Good point: Energy efficienty, no mechanical parts so
mechanical resonance free.
• Bad point: Stimulation point and Sensation point is different
Electrical Stimulation from Skin Surface皮膚表面
からの電気刺激
 神経末端の刺激され易さから空間マッピング実現
各受容器の神経配置の特徴を利用した選択刺激
 Electrical Stimulation from Surface: Stimulate Nerves directly.
If we can “Selectively” Stimulate the Nerves, we can generate ANY tactile Sensations.
 Just Like we make colors by mixing primary colors.
梶本「皮膚感覚神経を選択的に刺激する電気触覚ディスプレイ」電子情報通信学会誌, 2001.
神経束への電気刺激
Stimulation to nerve bundle
Prosthesis(義手)
Sensor
Embedded electrodes
Sensor
•Matrix electrodes (holes) are embedded, and
nerve will grow into the holes.
•埋め込み型マトリクス電極。神経再生時に電極を
通過して学習による空間マッピング．
鈴木「神経再生型電極に関する研究」東京大学博士論文, 1998
Tactile AR
Self-diagnosis tool of Breast Cancer Checker
as Tactile AR
Silicon oil reduces friction between
two films
Checking Breast Cancer
Rub breast through oil-contained thin plastic bag.
The oil reduces surface texture, and internal tumor
(腫瘍) can be observed
Tactile Contact Lens as Tactile AR
触覚のAR：触覚コンタクトレンズ
佐野他：触覚コンタクトレンズ (ROBOMEC’04)
Simple Tactile AR: Adding Clicking Sensation
簡便な触覚AR：クリック感の付与
Give short vibration instead of click sound
 Fukumoto et al., Active click: tactile feedback for touch panels
CHI2001
iPhone 3D touch
Material feeling
Vibrations caused by touching is
one of the clues for material feel
Vibration on
Tapping (敲く)
Characteristic vibration (固有振動)
Rubbing （擦る）
Friction vibration
Allison M. Okamura
Hasegawa lab 2009
Vibration from material
Task: Find a real plate nearest to the virtual plate
10 participant
Fixed by 2 points
Structure:
81% correct
Fixed by 3 points
Acrylic
MDF (wood like board)
Material: 60% correct
Hasegawa lab 2013109
Simulation based vibration generation
Thermal Display
Thermal sensor + touch sensor
Peltier device
Temperature
Skin surface
接触瞬間から2～3秒間の温度変化が
材質感推定の強力な手がかり
2 to 3s temperature change is the key
Time to detect object property.
Peltier device with temperature sensor
Object surface
is used to reproduce the time course.
Contact
Yamamoto, “Control of Thermal Tactile Display Based on Prediction of Contact Temperature,” ICRA2004
Haptic rendering
Haptic rendering
Computation for haptic display
Shape display
Output force ∝ penetration depth
Dynamics
Simulate equations of motion for objects to display.
Give reaction force of output force to the simulated
object
Shape display
Control loop for haptic interface
(impedance type)
Virtual World
Force display
1
2
3
F=kx
1.Measure finger position
2.Collision detection and output force computation
3.Display the output force
High update rate is necessary
Finger position
Outside of
the shape
inside
Process# in previous slide 1 2
time
3 1 2
Too much penetration
3 1 2
3 1 2
3 1 2
3 1 2
Too much reflection force
3
High update rate is necessary
Finger position
Outside of
the shape
Stable contact
inside
Process #
time
123123123123123123123123123
Stable contact requires fast update rate like 1kHz.
While vision/graphics requires 30Hz-60Hz
Shape display
Shape display by force
Force is proportional to penetration depth
Haptic pointer
＝Tool/Finger tip position
in virtual world
Sudden change of output force direction gives strange and unstable feel.
Shape display
Proxy (God Object) method
Proxy
Haptic pointer
Motion rule for Proxy
Try to move to local nearest position to the haptic pointer
Do not enter inside object
Friction force
Add friction to proxy method (by limiting motion)
1
3
2
1
q0
q
5
4
5
Friction cone
Static friction force< m0n
m0 = tanq 0
m = tanq
6DOF haptic rendering
Display contact between arbitrary shaped objects
任意形状同士の接触の提示
Computation Methods
Point cloud and penetration depth
Represent Haptic pointer’s shape by many points.
Contact volumes between two convex shapes.
凸多面体同士の接触体積
Virtual Coupling
Haptic interface and proxy are connected by 6DOF spring
damper model. Proxy has inertia. Then, simulate them.
６DOF Proxy
Find the motion of proxy when its inertia→0
Point could (McNeely et.al. 1999 (Boeing))
Objects→Voxel(b), Pointer→Point cloud(c)
Output force is based on penetration depth from
the center of
the voxel
Pointer is moved by Virtual Coupling
Point cloud
Pointer→point cloud, Object→Triangle mesh
Making wall on triangle edges
penetration depth is computed
for the point surrounded by walls
Real-time interference analysis between a tool and an environment
S. Hoa, S. Sarmaa, Y. Adachi, 2001
Overlapped volume between two convex shapes
S.Hasegawa and M.Sato, 2004
Overlapped volume between two convex shapes
S.Hasegawa and M.Sato, 2004
Shapes are represented by
Convex polyhedron
Find overlapped volume
Integrate them and get
force and torque
Integrate penetration For each triangles
Why convex
凸
Convex shape have only one minimum
local = global minimum
Local minimum is easy
Global minimum is difficult
Convex shape
Local Local and
Global
Local
Decompose
non-convex
into convex
Non convex shape may have many
minimum
local ≠ global minimum
Non convex
(concave 凹) shape
Contact analysis
Overlapped volume of two convex shapes
D. E. Muller and F. P. Preparata :
“Finding the intersection of two convex”
(1978)
Find the shape (faces and vertices) of overlapped volume
from two convex polyhedrons and
a point on the overlapped volume.
126
Contact analysis
Dual transform: transform faces to vertices and
vise vasa.
Dual transformation
O
n
O
1
n
Contact analysis
The process
A point in the
overlapped volume
Vertices of
Overlapped volume
Two convex
represented by
half planes
Dual
transform
Dual
transform
Quick hull algorithm
finds outer edges and
vertices
Virtual Coupling
(Colgate 1995)
Connect proxy and haptic pointer by 3DOF
translation and 3DOF rotation spring-dampers.
Haptic pointer
Simulate dynamics
Proxy
6DOF proxy method
Inertia of Proxy in Virtual Coupling → 0
１
２
３
Do not take state 2.
Instead transit to state 3 instantly
Intermediate representation and multi rate
haptic rendering
Fast update Simulator
Haptic interface
Force
rate for all
Position
Fast update rate (1kHz)
Multi-rate with intermediate representation
Simulation
Intermediate
(Local shape)Haptic
rendering
Finger position
impulse
Slow update (20Hz)
Haptic interface
Force
Position
Fast update (1kHz)
動き始めの遅れも補償する局所シミュレーション方式
(須佐ら 2009)
http://www.youtube.com/watch?v=5kFMNyeKTyE

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