Haptic Perception and Devices David Johnson
Dec 20, 2015
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
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
Human skin
Haptics and Vision
Information Temporal
capacity (bits/sec) 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)
Kandel et. al., 2000
Meissner’s Merkel Pacinian RuffiniCorpuscle Cell Complex Corpuscle Ending
Receptors
Receptive
Field
Intensity and Time Course of Neural Signal (adaptation)
NeuralSpike train
Stimulus
FA I SA I FA II SA II
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.
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Proprioception Includes The Vestibular SenseOcular Motor
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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
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
6DOF Delta
Magnetic Levitation
• CMU• Very high fidelity• Small workspace• movie
Exoskeleton
• 5DOF
Rutgers Hand Master
• Pneumatic
Foot Haptics (locomotion interface)
Sarcos Biport Iwata’s GaitMaster
Omni-directional treadmill
Foot-based interfaces
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.