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Haptic Interface

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.

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Haptic Interface

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  1. Haptic Interface April 2006 Prof. Ed Colgate Northwestern University Evanston, IL USA

  2. Today’s Class • Course overview • Introduction to Haptics • Haptics overview • History • Applications/Motivations • How to design effective haptic interfaces • Current challenges • Break • Psychophysics

  3. Northwestern University Chicago

  4. 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

  5. Northwestern Scenes

  6. Prof. Kevin Lynch Prof. Mitra Hartmann Prof. Michael Peshkin Northwestern>Dept of Mechanical Engineering>LIMS Not shown: Prof. Malcolm MacIver

  7. LIMS Research • Human-Robot Interaction • Haptic (touch) interface • Assistive robots • Robot Motion Planning • Underactuated systems • Biologically-Inspired Robotics • Robotic fish • Active sensing Prototype variable friction haptic display Developed by John Glassmire Robotic Ribbon Fin Developed by Michael Epstein

  8. 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

  9. 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

  10. Website http://othello.mech.northwestern.edu/~colgate/UPC/

  11. hap·tic ('hap-tik)adj.Of or relating to the sense of touch; tactile.[Greek haptikos, from haptesthai, to grasp, touch. (1890)] Location/configuration Motion Force Compliance Cutaneous Kinesthesia Temperature Texture Slip Vibration Force

  12. Our focus: programmable haptic interfaces • Mainly: kinesthetic interface to virtual environments • Also: tactile interface to virtual environments Phantom - kinesthetic Pin Array – low frequency cutaneous

  13. More generally: human-robot interaction • Telemanipulation • Exoskeletons • Physical Rehabilitation and Exercise machines • Intelligent Assist Devices (IADs) • Advanced prosthetics • “Near-field” telerobotics • Human-robot-human

  14. A Little History • Ray Goertz, Argonne National Lab, 1940s

  15. 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…

  16. ~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

  17. 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!

  18. LIMS continues to be active in haptics

  19. Three-rotational virtual spring and damper

  20. Ball in a box

  21. 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 Haptics has many applications

  22. Visual 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 Training

  23. Virtual Prototyping Applications McNeeley et al. (Boeing Corp.)

  24. Rehabilitation Applications

  25. Teleoperation Applications

  26. 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

  27. Entertainment Applications

  28. 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

  29. How to design effective haptic interfaces • A simple three-step program… • Understand how the human sensory and perceptual systems work • Use this information to develop performance metrics • Understand how to build/control machines that display haptic percepts and meet performance metrics

  30. A. How haptic sensing works • Let’s see it in action…

  31. 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

  32. 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

  33. 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 Mechanoreceptors Mechanoreceptors differ according to: -frequency response -receptive field -location

  34. 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

  35. Sensory Homunculus

  36. 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

  37. Bilateral Nature of Kinesthetic Sensing • 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 Human Hand/Arm Environment effort flow effort  flow = Power

  38. 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!

  39. B. Performance metrics for haptics • Performance can be assessed at various levels: • Peripheral sensors • From sensors to CNS • Perceptual • Functional

  40. Pressure thresholds • Weinstein, 1968 • Pressure measured with precisely calibrated nylon filaments pressed into skin

  41. 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

  42. Frequency response thresholds • Bolanowski, 1988

  43. Just Noticeable Differences • DI is the increment in intensity that, when added to stimulus intensity I, produces a just noticeable difference. • DI/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

  44. JNDs Sources: Biggs and Srinivasan “Haptic Interfaces” Schiffman “Sensation and Perception”

  45. 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, “Tactile Displays”, in W. Barfield, and T.A. Furness (Eds.), Virtual Environments and Advanced Interface Design, Oxford University Press, New York, 1995, pp. 349-414.

  46. Information Transmission Rates Optacon Tadoma

  47. 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

  48. Conclusions: haptic performance • High bandwidth • Temporal to 1 kHz • Spatial discrimination to 1 mm • Extraordinary sensitivity to certain stimuli • 300 Hz vibration (.1 mm), raised edges (<1 mm) • 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

  49. Displaying haptic percepts • Ground-based devices • Body-based devices • Inertial reaction devices • Tactile displays

  50. Ground-based devices • Phantom • Haptic Master • Cobot Hand Controller • List goes on…

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