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Haptic Interface. April 2006 Prof. Ed Colgate Northwestern University Evanston, IL USA. Today’s Class. Course overview Introduction to Haptics Haptics overview History Applications/Motivations How to design effective haptic interfaces Current challenges Break Psychophysics. - PowerPoint PPT Presentation
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Haptic Interface
April 2006
Prof. Ed Colgate
Northwestern University
Evanston, IL USA
© J. Edward Colgate, 2006
Today’s Class
Course overview Introduction to Haptics
Haptics overview History Applications/Motivations How to design effective haptic interfaces Current challenges
Break Psychophysics
© J. Edward Colgate, 2006
Northwestern University
Chicago
© J. Edward Colgate, 2006
Northwestern University
Founded in 1851 in Evanston, IL Two campuses today: Evanston and Chicago ~8000 undergraduates and ~6000 graduates in 9
schools ~1400 undergraduates and ~700 graduates in the
McCormick School of Engineering and Applied Science
9 Departments in McCormick Applied Math; Biomedical; Chemical; Civil & Environmental;
Computer; Electrical; Industrial; Materials Science; Mechanical
© J. Edward Colgate, 2006
Northwestern Scenes
© J. Edward Colgate, 2006
Northwestern>Dept of Mechanical Engineering>LIMS
Prof. Michael Peshkin
Prof. Kevin Lynch
Prof. Mitra Hartmann
Not shown: Prof. Malcolm MacIver
© J. Edward Colgate, 2006
LIMS Research
Human-Robot InteractionHaptic (touch) interfaceAssistive robots
Robot Motion PlanningUnderactuated systems
Biologically-Inspired RoboticsRobotic fishActive sensing
Prototype variable friction haptic display
Developed by John Glassmire
Robotic Ribbon Fin
Developed by Michael Epstein
© J. Edward Colgate, 2006
Goals of this course Gain familiarity with key ideas in haptics
Haptic perception Psychophysics Design and control of haptic interfaces Passivity, Z-width Haptic Rendering
Hands-on experience with haptics Gain some familiarity with current research and
literature Identify opportunities for research in haptics
© J. Edward Colgate, 2006
Grading
30% Class participation/contribution Ask questions! Offer opinions, insights, etc.
40% Homework 3 assignments, due Wed, Thu, Fri
30% Paper presentations Each student gives a 15 minute presentation of a
paper All papers are from 2006 Haptics Symposium
© J. Edward Colgate, 2006
Website
http://othello.mech.northwestern.edu/~colgate/UPC/
© J. Edward Colgate, 2006
hap·tic ('hap-tik)adj.
Of or relating to the sense of touch; tactile.[Greek haptikos, from haptesthai, to grasp, touch. (1890)]
Temperature TextureSlip Vibration Force
Location/configuration Motion ForceCompliance
Cutaneous Kinesthesia
© J. Edward Colgate, 2006
Our focus: programmable haptic interfaces
Mainly: kinesthetic interface to virtual environments
Also: tactile interface to virtual environments
Phantom - kinesthetic
Pin Array – low frequency cutaneous
© J. Edward Colgate, 2006
More generally: human-robot interaction
Telemanipulation Exoskeletons Physical Rehabilitation and Exercise
machines Intelligent Assist Devices (IADs) Advanced prosthetics “Near-field” telerobotics Human-robot-human
© J. Edward Colgate, 2006
A Little History
Ray Goertz, Argonne National Lab, 1940s
© J. Edward Colgate, 2006
Computer simulation replaces the slave manipulator
Fred Brooks, UNC Chapel Hill, 1970s
Developed to study molecular docking
User feels interaction force between molecules
Master was one of Goertz’s Didn’t work very well…
© J. Edward Colgate, 2006
~1990 – Haptic Interface Emerges as an Engineering Discipline
Margaret Minsky’s “virtual sandpaper” system developed at the MIT Media Lab
Dov Adelstein’s force reflecting joystick developed in the MIT Biomechanics Lab
Force
Minsky, 1990
© J. Edward Colgate, 2006
LIMS has been involved since the early days (~1991)
Paul Millman’s 4DOF Haptic Interface Originally developed with
telemanipulation in mind Never got around to
developing the slave!
© J. Edward Colgate, 2006
LIMS continues to be active in haptics
© J. Edward Colgate, 2006
Three-rotational virtual spring and damper
© J. Edward Colgate, 2006
Ball in a box
© J. Edward Colgate, 2006
Haptics has many applications
Blind Persons Programmable Braille Access to GUIs
Training Medical Procedures Astronauts
Education Computer-Aided Design
Assembly-Disassembly Human Factors
Entertainment Arcade (steering wheels) Home (game controllers)
Automotive BMW “iDrive” Haptic Touchscreens
Mobile Phones Immersion “Vibetonz”
Animation/Modeling Art Material Handling
Virtual Surfaces
© J. Edward Colgate, 2006
TrainingVisual display alone is not sufficient for certain
types of virtual environments. To learn physical skills, such as using complicated hand tools, haptic information is a requirement
Applications
© J. Edward Colgate, 2006
Virtual Prototyping
Applications McNeeley et al. (Boeing Corp.)
© J. Edward Colgate, 2006
Rehabilitation
Applications
© J. Edward Colgate, 2006
Teleoperation
Applications
© J. Edward Colgate, 2006
Computer interface for blind users
Text-based computers can easily be enhanced to include a speech synthesizer
Graphical user interfaces are inherently visual A haptic display can help a blind computer user
interact with graphics-based operating systems
© J. Edward Colgate, 2006
Entertainment
Applications
© J. Edward Colgate, 2006
Underlying motivations for haptics
Looking across applications, we find common motivations:
Haptics is required to solve the problem Interfaces for the blind Phlebotomy training (task is mainly “feel”) Vibetonz – a private communication channel
Haptics improves realism and sense of immersion Entertainment Animation/modeling
Haptics provides constraint Assembly/disassembly Virtual surfaces
© J. Edward Colgate, 2006
How to design effective haptic interfaces
A simple three-step program…
A. Understand how the human sensory and perceptual systems work
B. Use this information to develop performance metrics
C. Understand how to build/control machines that display haptic percepts and meet performance metrics
© J. Edward Colgate, 2006
A. How haptic sensing works
Let’s see it in action…
© J. Edward Colgate, 2006
Some terminology
“Haptic” refers to the perceptual system that draws information from the skin and kinesthesis
“Proprioception” is the unconscious perception of movement and spatial orientation arising from stimuli within the body itself
“Kinesthesia” is the sense that detects bodily position, weight, or movement of the muscles, tendons, and joints
“Tactual Stereognosis” is the perception of the form of an object by means of touch
© J. Edward Colgate, 2006
Sensors that contribute to haptic perception
4 types of mechanoreceptors
2 types of thermoreceptors
2 types of nociceptors (free nerve endings for pain)
3 types of kinesthetic receptors
© J. Edward Colgate, 2006
Mechanoreceptors
Mechanoreceptorsdiffer according to:
-frequency response-receptive field-location
Merkel’s Disk(SA I)
• 0.4 Hz - 100 Hz• 11 mm2 receptive field• shallow
•Curvature, shape, pressure
Meissner’s Corpuscle(FA I)
• 2 Hz - 200 Hz• 13 mm2 receptive field• shallow
• flutter vibration; tickle; texture?
Pacinian Corpuscle(FA II)
• 40 Hz - 800 Hz• 101mm2 receptive field• deep
• vibration
Ruffini Endings(SA II)
• 0.4 Hz - 100 Hz• 59 mm2 receptive field• deep
• skin stretch, force
© J. Edward Colgate, 2006
The skin is an important organ!
Large: approximately 2 m2
Abundant sensors: ~500,000 mechanoreceptors spread across the
body ~17,000 in the glabrous (non-hairy) skin of the hand
© J. Edward Colgate, 2006
Sensory Homunculus
© J. Edward Colgate, 2006
Kinesthetic receptors Muscle Spindles
provide muscle length and velocity information
Golgi Tendon Organs provide tension information
Joint Afferents provide joint angle and angular velocity information Ruffini endings and
Pacinian corpuscles located in joint capsule
Note that people with artificial joints have almost normal sense of joint position
© J. Edward Colgate, 2006
Bilateral Nature of Kinesthetic Sensing
Human Hand/Arm
Environmenteffort
flow
effort flow = Power
Unlike vision & audition, kinesthetic sensing is two-way
There is also the prospect for significant power exchange with the environment as part of a haptic interaction
© J. Edward Colgate, 2006
Conclusions: how haptic sensing works
A vast number of sensors in both the skin and musculoskeletal system work in conjunction with the motor control system to enable sensing of mechanical stimuli Haptic sensing is bilateral
Perception clearly involves the CNS as well as the peripheral nervous system, but that is the subject of another lecture…
We’ve just barely scratched the surface!
© J. Edward Colgate, 2006
B. Performance metrics for haptics
Performance can be assessed at various levels: Peripheral sensors From sensors to CNS Perceptual Functional
© J. Edward Colgate, 2006
Pressure thresholds Weinstein, 1968 Pressure
measured with precisely calibrated nylon filaments pressed into skin
© J. Edward Colgate, 2006
Point localization thresholds
Weinstein, 1968 Distance between
body point stimulated and subject’s impression of where stimulation took place
Two-point discrimination data are similar
© J. Edward Colgate, 2006
Frequency response thresholds
Bolanowski, 1988
© J. Edward Colgate, 2006
Just Noticeable Differences
I is the increment in intensity that, when added to stimulus intensity I, produces a just noticeable difference.
I/I = k is the “Weber fraction” Weber hypothesized that k would remain
constant across all values of I for a given modality. Not true, but often a reasonable approximation
© J. Edward Colgate, 2006
JNDsVision (brightness, white light) 1.5%
Audition (middle pitch & moderate loudness) 10%
Smell (odor of India rubber) 25%
Taste (table salt) 33%
Kinesthesis (lifted weights) 2%
Pressure (cutaneous pressure “spot”) 14%
Length 10% or less
Velocity 10%
Acceleration 20%
Force on skin 7%
Compliance 23%
Viscosity 34%
Sources: Biggs and Srinivasan “Haptic Interfaces” Schiffman “Sensation and Perception”
© J. Edward Colgate, 2006
Perceptual Measures
Channel capacity in bits/sec Max information flow at receptor level:
~107 bits/sec for eye ~106 bits/sec for hand ~105 bits/sec for ear
Post-processing rate for tactile information is ~2-56 bits/sec Compare to ~40 bits/sec for speech and ~30
bit/sec for reading Kaczmarek, K.A., and P. Bach-y-Rita, “TactileDisplays”, in W. Barfield, and T.A. Furness (Eds.), VirtualEnvironments and Advanced Interface Design, OxfordUniversity Press, New York, 1995, pp. 349-414.
© J. Edward Colgate, 2006
Information Transmission Rates
Reading ~ 30 bits/sec
Kinesthetic Morse Code 2.7 bits/sec
Tadoma 12-14 bits/sec
Optacon (vibrotactile) 5.4 bits/sec (40 wpm)
Tadoma Optacon
© J. Edward Colgate, 2006
Example of a Functional Measure
Object identification via tactual stereognosis Klatzky, Lederman and Metzger 1985 96% correct identification of 100 common objects 94% within first 5 seconds; 68% within first 3
seconds
© J. Edward Colgate, 2006
Conclusions: haptic performance High bandwidth
Temporal to 1 kHz Spatial discrimination to 1 mm
Extraordinary sensitivity to certain stimuli 300 Hz vibration (.1 m), raised edges (<1 m)
Huge dynamic range: forces from ~0.5N to ~500N JNDs generally consistent with other senses
Better for signals (e.g. force) than impedances (e.g. compliance) Haptics does not excel as a high bandwidth channel for
structured information (characters, words, text) But Tadoma illustrates the power of a highly parallel approach
Haptics does excel at 3D object recognition
© J. Edward Colgate, 2006
Displaying haptic percepts
Ground-based devices Body-based devices Inertial reaction devices Tactile displays
© J. Edward Colgate, 2006
Ground-based devices
Phantom Haptic Master Cobot Hand Controller List goes on…
© J. Edward Colgate, 2006
Body-based devices
Cybergrasp Rutgers Hand Master Again, many others
© J. Edward Colgate, 2006
Inertial Reaction Devices
Game controllers
motors
eccentric masses
shafts
© J. Edward Colgate, 2006
Tactile Displays
Pin arrays (Optacon, Harvard displays, many others)
Lateral stretch Electrocutaneous displays Haptic field displays
© J. Edward Colgate, 2006
Some current challenges in haptics
Low power, embedded haptics Mobile electronics
Exploiting tactual stereognosis (e.g., for automobile instrument panels) Exoskeletal devices haven’t been the answer
Haptics over the internet (e.g., for telesurgery) Latencies are a big issue
Haptic feedback for amputees
© J. Edward Colgate, 2006
Haptics for prosthetics
“Sensory reinnervation” provides a possible means for restoring the sense of touch to amputees
Kinesthetic and tactile sensorsHaptic
display