Haptic Perception and
Devices
David Johnson
What is Haptics?
• adj. Of or relating to the sense of touch;
tactile. [Greek haptikos, from haptesthai,
to grasp, touch.]
– Haptics involves both proprioceptive and
tactile senses, in concert with other senses.
• adj. The science of applying touch (tactile)
sensation and control to interaction with
computer applications.
The Sense of Touch
• Everyday Tasks
– Dialing a phone
– Playing a guitar or piano
– Finding a light switch
– Using a mouse
• Touch is complex: tying a shoelace
• Only bi-directional communication
channel – both input & output
Why is Touch Important?
• Touch-tone phone
– Rich tactile cues
– Can be done
without looking
– Effortless
• PC calculator
– No tactile cues
– Only visual
feedback
– Painstaking
Tactile Perception
• Provides information about our
environment
– e.g. hot, cold, smooth, rough
• Provides feedback
– e.g. when trying to lift an object, press
buttons, etc.
• Difficulties if no feedback?
Haptics
Human skin
Surface of average sized
adult human: 1.8 m2
(1000 times that of retina)
Weight: 5 kg
Total number of axons:
1.1*106
Retina: 106 axons,
Cochlea: 6*104 axons
Haptics and Vision
Information
capacity (bits/sec)
Temporal
acuity
Fingertip
102
5 ms
Ear
104
0.01 ms
Eye
106-109
25 ms
Peripheral Pathways of Touch
•
Mechanoreceptors - pressure, texture,
vibration
•
•
Proprioceptors - body position
Nocioceptors
– Two pathways for pain
•
•
•
one fast pathway for sharp pain,
one slow pathway for dull pain
Thermoreceptors
Four Receptor Types
a) Merkel Disks -- constant
sources of stimulation over a
small area, such as if you
were carrying a pebble
b) Meissner Corpuscles -respond best to active touch
involved in object exploration
c) Ruffini Endings -- constant
stimulation over a larger area
- also detects skin stretch
d) Pacinian Corpuscles -extremely sensitive over a
large receptive field -- blow
gently on the palm of your
hand
Functional characteristics of Skin Mechanoreceptors:
Receptive field size (I = small, II = large)
and adaptation rate (FA = fast adapting, SA = slow adapting)
FA I
SA I
FA II
SA II
Receptors
Meissner’s
Corpuscle
Merkel
Cell Complex
Pacinian
Corpuscle
Receptive
Field
Intensity and Time Course of Neural Signal (adaptation)
Neural
Spike train
Stimulus
Kandel et. al., 2000
Ruffini
Ending
Receptive Field
The two-point threshold
for any part of the body
is determined by the size
of the receptive fields
and the extent of overlap
Proprioception
• All muscles have
nerve fibers which
detect the amount
the muscle is
stretched
• All joints have fibers
which detect the
relative position of
each bone
• Together these allow
you to determine the
position of every part
of your body.
[Green]
Proprioception Includes
The Vestibular Sense
Ocular Motor
[Green]
Haptics
Haptic Interfaces
• Fully duplex channel. You can both
transmit and receive information
simultaneously.
• Requires very high refresh rates of approx.
1000 Hz for realistic feel.
• Requires very high spatial resolution.
– On smooth glass surface, dot of height 1-3
µm and diameter of 550 µm can be detected
by the fingertip (Johansson & LaMotte, 1983)
Tactile Technologies
• Tactile information is produced by perturbing the
skin
– Pins or other mechanical vibrating elements - either
alone or in an array, as in devices for Braille display
• typically used for fingertip stimulation
– Air jets blow to produce a disturbance
– Cushions of air can be inflated or deflated to vary
pressure on skin
– Electrical stimulation - low levels of current provide a
localized tingling sensation
• Typically used in gloves, or for larger body areas
Laterotactile
• Induce sensations of
indent from lateral
movement of skin
Vibrotactile
Electrotactile
Servomotor mechanical
Tactile Vest
Force-Feedback Technologies
• Kinesthetic (relating to the feeling of
motion) info is produced by exerting
mechanical forces
– Haptic devices movie
MPB Freedom7 and Cubic
CyberForce
[Chang]
6DOF Delta
Magnetic Levitation
•
•
•
•
CMU
Very high fidelity
Small workspace
movie
Exoskeleton
• 5DOF
Rutgers Hand Master
• Pneumatic
Foot Haptics
(locomotion interface)
Omni-directional treadmill
Foot-based interfaces
Sarcos Biport
Iwata’s GaitMaster
Whole-Body Haptics
Sarcos Treadport II
CirculaFloor
• Moving floor tiles
• An example of
“encountered haptics”
Discussion
• Mechanical aspects are more daunting
than for other VR technologies
• Must handle gross positioning
(proprioception) and fine detail (tactile)
• Burgeoning area
– 10 years ago, 20 papers a year
– Now, 1000’s.