What Fidelity Where?

Deriving Haptic

Design GuidelinesPresented September 2008 for

Biomedical Engineering Faculty,

Carleton University

By Jeremy Kuzub

Reproduce Reality

vs.

Reproducing Sensory “Reality”

http://oamenisifluturi.blogspot.com/2007/07/six-blind-men-and-elephant.html

Muscles

Tendons

Joints

Skin

http://hackerfriendly.com/wp/wp-content/uploads/2007/02/warm02big.jpg

To Do List:Learn precisely what sensory

information is sent to the brain

by:

Resolution

Bandwidth

Power

CrossTalk

Nonlinearity

Variation

http://hackerfriendly.com/wp/wp-content/uploads/2007/02/warm02big.jpg

To Do List Part 2:Develop guidelines for

designing haptic systems

http://static.flickr.com/117/272176745_09c599366a.jpg

Real world:

physical interaction

Perception of environment

Human Sensory transfer function

Goal: Understand the black box so we don’t have to emulate less relevant stimuli

Nerve endings –Our interface haptic with the physical world

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Reference paper:Deriving Haptic Design Guidelines from Human Physiological, Psychophysical, and Neurological Foundations

Kelly S. Hale and Kay M. Stanney

University of Central Florida

Tactile Feedback

http

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Different types of skin have different types of receptors

…and…

Different receptor types detect different types of stimuli

Tactile

Different receptor types detect different types of stimuli

Tactile: Gabrous (Hairless Skin)

Stimulus frequency

Stimulus resolution

0.5 mm2.0 mm

0 Hz

10 Hz

100 Hz

1000 Hz

1.0 mm1.5 mm

Pacinian Corpuscles

Ruffini Endings

Meissner Corpuscles

Merkel Disks

motion

Motion &deformation

Motion &deformation

motion

5 ms to perceive separate stimuli

20 ms to perceive stimuli order

Shape

Deformation

Movement

Texture

Grip

Vibration

Designers must determine which cues best suit the task

Change Rate

Tactile

http://www.web-l.com/cuteanimals/newborn-Egyptian-Tortoise-on-finger-tip.jpg

Let’s Touch upon Some Some Sample Difficulties

(aka Engineering Challenges)

Sense of touch varies on skin type – different receptor mixes

Senses get acclimated to stimuli (trigger threshold is dynamic!)

Tactile sensitivity can vary with sex!

Sense channels have crosstalk!

Kinesthetic Feedback

http://146.74.224.231/archives/2007/09/body_worlds_2_t.html

http://cnx.org/content/m11613/latest/IK_example1_sol.png

Muscles, Joints, and Tendons:How are my limbs moving and who’s moving them?

Kinesthetic

Ruffini EndingsStatic and dynamic joint

movement, extrema

Golgi Tendon organsposition force (my movement)

and static position

Muscle Spindlesawareness of movement

subjective weight

Golgi EndingsExtreme positions

http://www.eorthopod.com/images/ContentImages/knee/knee_ac

l_hamstring_tendon/knee_acl_hamstring_tendon_intro02.jpg

Active system: closed loop.

What is the Bandwidth?

0.5 -1.7Hz

Wait.

0.5 -1.7Hz ?http://www.newt.com/wohler/events/galapagos-2004/santa-

cruz/tortoise-lori-big.jpg

http://www.ipmc.cnrs.fr/~duprat/neurophysiology/images/brain2.jpg

http://digitalheadbutt.files.wordpress.com/2007/05/crouch-robot.jpg

memory motor trace of the

predicted movement….

= faster execution of complex

movements in the absence of slower

receptor feedback

Slow receptor feedback

… In other words, our bodies have some

network latency issues and must model

themselves to improve bandwidth at the

expense of accuracy!

http://www.emoryhealthcare.org/Images/spine_im

ages/Davinci%20Man.jpg

Position change sensitivity

decreases distally.

Sufficient movement must occur to detect direction

+/- 0.8 deg+/- 2.0 deg

+/- 2.5 deg

http://cats.lovetoknow.com/images/Cats/thumb/a/

a6/Holding_kitten.jpg/200px-Holding_kitten.jpg

Surface Stiffness saturation: 400 Newtons per meter

End point force saturation: 4 Newtons

…We do not need to create very large forces to convey

object size or surface hardness kinematically

Part III: (last part)

Combining Haptics with other senses:

Multimodal Interaction

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Hansen Writing Ball - 1870

We are visual

animals…

Haptics can enhance hand-eye coordination greatly when interacting

Most information is visual, but eyes can’t influence the environment (apologies to quantum physics…)

www.apple.ca

Spatial Memory via limb position – objects could be stored in ‘space’

Natural display interaction – flipping, turning, shaking, vibration

Typical Combination:

Vision + Haptics

This is a natural combination –

most humans are fully accustomed to the process of

See - reach - touch - feel - change - see

Multimodal Design:

Guidelines

Vision will usually dominate

Haptics provides spatial memory

Avoid time lag between visual and haptic cues

Brains think of space as absolute, not posture-relative

Touch and vision are cognitively linked – not two channels

http

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Multimodal Conclusion?

Redundancy, not Replacement

Haptics: Future?

Further

Study

Needed!

e.g.A man’s big toe has a

pressure detection threshold

of 355mg !

http://www-robotics.jpl.nasa.gov/roboticImages/img840-322-browse.gif