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Haptics

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Isabell Westrich

on 25 December 2013

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Transcript of Haptics

Definition
Haptic Loop
Challenges
Free motion of operator when there is no contact
Continuous nature of the physical dynamics and the discrete nature of the computer control
Early research
Lederman and Klatzky, 1987
Texture
Hardness
Temperature
Weight
Volume
Shape
Motion
Function
Haptic Interface
generate the sense of virtual touch in the form of:
force feedback : receptors in the joints like weight, motion
tactile feedback : sensors in the skin like temperature, texture
Introduction
HAPTICS
Haptic Device Design

Admittance
devices
"...technology of experiencing
and creating touch sensations in human operators."


operator applies the force and constrain the operator`s position to match the appropriate deflection of a simulated object in a virtual world
Impedance
devices
the force is applied as a vector to the position of the operator according to computed behavior of the simulated object
industrial robots

HAPTICS
Tactile Display
Phantom Premium
Allow us to derive device requirements!
Mechanisms
Sensing
Different movements for each
What is Tactile Display?
Actuation and Transmission
Used to convey force, contact and shape info to skin, mainly fingertips
Specific Pupose: Display of contact events:
location, slip/shear, texture, shape
Merriam-Webster Dictionary:
1."relating to sense of touch"
2."perceptible by touch"
Applications
for high-fidelity haptic sensations
Automotive
Education
Entertainment
Human-computer interactions
Manufacturing
Molecular biology
Surgical robotics
Scientific visualization
Space
desirable mechanism attributes for open-loop force control
low inertia, high stiffness & suitable kinematic
- weight minimized
- Kinematic singularities &
high transmission ratios must be avoided

Vibration Feedback
Most common way to provide tactile feedback using:
The Phantom Omni device
from SensAble Technologies
-piezoelectric materials
-small voice-coil motors etc.
ideal haptic device: move freely & free of singular configurations
HystSim
hysteroscopy
device
Measures of Mechanism Performance
Kinematic performance
Jacobian matrix
J
(p,q)
- manipulability
- mechanism isotropy
- minimum force outout
Human vibration sensing range:
Up to 1kHz with a peak around 250 Hz
Optimization
Sensors used to measure the state of the device
Encoders
Rotary optical quadrature encoders = position sensors
Haptic Rendering
quantitative performance measure
M= min W(theta)
s
Vibration Feedback
Sensing
Kinematics
Collision
Surface points
Force
Kinematics
Actuation
Touching is sensed via sensors in our skin
Haptic applications require velocity measurement (damping)
velocity: numerical diff of the posn signal
or specialized hardware for time measurement

Force Sensors
enables perception of free motion
by canceling device friction
Haptics display usually uses a 1st order
stiffness model but lacks realism.

-Higher order models
-Empirical data
-Both simultaneously could be used
actuators are controlled to provide appropriate haptic sensations to the human operator
Kinematics : Joint angle space is converted to cartesian frame and end effector is haptic interface point(HIP) also called avatar as the virtual representation of haptic interface
Vibration Feedback
Requirements:
- low inertia, low friction, low torque ripple & back-drivability
- usually open-loop force control (low friction & inertia)
Can be used to simulate:
-Patterned textures
-Roughness etc.

Collision detection
: objects are represented by polygons-splines and check if HIP is inside the body, if not then force is zero!
Determining surface point
: if HIP is in the body, put this on the surface
Force calculation
: due to object geometry or object surface; texture or friction;
Basdogan and Srinivasan, 2002:
F=kx; x:depth of the penetration
k: stiffness
low k : soft surface
high k: undesirable
vibrations


Haptic Paddle
Vibration Feedback
Can also be used for sensory substitution to convey
-attention
- direction
-other information

eg. tactile back display when driving
Vibration Feedback
Haptic Rendering
Rendering in Complex Environments
Mathematical Models; Hannaford and Okamura, "Haptics", 2002.
Otaduy and Lin, "Haptic Rendering", 2008 introduced an energy based method;

Samur, "Performance Metrics for Haptic Interfaces", 2012 summarized psychophysical evaluation studies and tests
Different equipments are used for this evaluations in design,
Kern, "Engineering Haptic Devices", 2009:
Actuators; electrodynamic, electromagnetic, piezoelectric, electrostatic
Force sensors; capacitive, optic, piezoelectric
Positioning sensors
Interface Selection
Contact Location, Slip and Shear Display
Increases accuracy in teleoperated systems greatly
vs.
To prevent dropping objects due to positioning error: tactile array sensors to measure:
-pressure distribution
-contact location
-local object geometry
Local Shape
Pin array,generally covered with an elastic layer
Psychophysical and perceptional experimental results for array specifications
e.g. deformation without pressure change --> lump!
OR helping visually impaired
Local Shape
Pins are indepedently controlled but currently not feasable!
Actuators:
-Piezoelectric
-Shape Memory Alloy
-MEMS
-Electromagnetic
References
Hannaford and Okamura, "Haptics", 2002.
Lederman and Klatzky, Hand Movement: A Window into Haptic Object Recognition, 1987.
Basdogan and Srinivasan, Haptic Rendering in Virtual Environments, 2002
Samur, "Performance Metrics for Haptic Interfaces", 2012.
Otaduy and Lin, "Haptic Rendering", 2008.
Kern, "Engineering Haptic Devices", 2009
Salisbury et al, "Haptic Rendering: Introductory Concepts", 2004.
Bontreger, The Design of a Haptic Device for Training and Evaluating Surgeon and Novice Laparoscopic Movement Skills, MS Thesis, 2011.
Satava et al, "Surgical Robotics System Applications and Visions", 2011
Basdogan and Srinivasan, 2002
Salisbury et al, Haptic Rendering: Introductory Concepts
Hannaford and Okamura, "Haptics", 2002
Samur, 2012
Samur, 2012
Thank you for your attention!
Questions?
ex.:
three free parameters
ten possible values

10 designs must be evaluated
3
1 dof haptic device
Full transcript