HighFidelity Haptic Synthesis of Contact with Deformable Bodies - PowerPoint PPT Presentation

1 / 23
About This Presentation
Title:

HighFidelity Haptic Synthesis of Contact with Deformable Bodies

Description:

It is required that an interpolation method to generate all possible responses ... Interpolate the coordinate bases. Interpolate the components ... – PowerPoint PPT presentation

Number of Views:51
Avg rating:3.0/5.0
Slides: 24
Provided by: poste5
Category:

less

Transcript and Presenter's Notes

Title: HighFidelity Haptic Synthesis of Contact with Deformable Bodies


1
High-Fidelity Haptic Synthesis of Contact with
Deformable Bodies
  • Jaeyoung Cheon
  • icejae02_at_postech.ac.kr
  • VR Lab, POSTECH
  • 2006. 6. 5

2
Outline
  • Introduction
  • Simulating Soft Objects
  • Response Synthesis
  • Local Force Field Continuum
  • Passivity
  • Conclusion

3
Introduction
4
Introduction Requirements of High-fidelity
Haptic Synthesis
  • Resemblance of virtual force response with actual
    responses
  • Force continuity under all allowed maneuvers
  • Passivity of the virtual environment
  • High-force update rate to combat the adverse
    effects of discretization

5
Simulating Soft Objects Considerations for
Haptic Rendering
  • Rigid object
  • Location, geometry, texture, frictional
    properties, etc.
  • Deformable object
  • Considerations of rigid object
  • Materials, support, internal structure, etc.

6
Simulating Soft Objects Previous approach
  • Assume that contact occurs at one, or at a small
    number of points
  • Localized deformation
  • The force of contact and the feel depend
    critically on the details of the shape of the
    object in contact
  • Localized deformation can be neglected.
  • By St. Venants principle
  • If a deformable body is loosely supported, one is
    permitted to ignore the contact details.
  • If it is well supported, the contact details
    dominate.

7
Simulating Soft Objects
8
Simulating Soft Objects
  • For deformable bodies, the point contact
    representation for realistic virtual interactions
    with deformable bodies is an idealization that is
    neither necessary nor sufficient.
  • Key Aspects for High-fidelity Haptic Rendering
  • The shape of the tool
  • The way it makes contact with the body

9
Response Synthesis
  • Common Method
  • To encode the virtual objects properties
  • To predict the contact responses by solving the
    continuum equations of deformation
  • The cost is heavy, thus it requires
    simplification.
  • Two Types of Approach to Speed Up
  • To represent high-order dynamic deformation
    models
  • The contact problem can be over simplified.
  • To precalculate a large number of responses
  • Effective but cannot represent nonlinear aspects

10
Response Synthesis The Proposed Method
  • A precalculation method for non-linear contact
    problems
  • Properties
  • The number of precomputation steps is
    proportional to
  • The number of possible cases of interaction
  • The number of dimensions considered
  • The precomputation burden can be reduced.
  • The storage requirements are acceptable.

11
Local Force Field Continuum Sticking State
  • There is no need to compute its shape during
    deformation after sticking state until slipping
    occurs.
  • Local force field at c for p
  • c The initial contact point on the body surface
  • p The corresponding point on the tool surface
  • These are the only quantities required to
    determine the subsequent response

12
Local Force Field Continuum Sticking State
13
Local Force Field Continuum The Force at
Contact Point
  • fc(d)fcx(dcx)ucxfcy(dcy)ucyfcz(dcz)ucz
  • Ucucx, ucy, ucz Local coordinate system
  • fcx(dcx), fcy(dcy), fcz(dcz) The
    force-deflection curves
  • d(t)p(t)-c(t) Deflection
  • p(t) p changes according to the movements of the
    tool
  • c(t) c changes when the tool slides over the
    body

Instrument
c(t)
Deformable Body
d(t)
p(t)
14
Local Force Field Continuum Sliding State
  • fcr(dcr) µc(dcz) fcz(dcz)
  • µ Coefficient of friction
  • fcr, dcr The respective projections of fc and
    dc on the surface of the undeformed body
  • c moves over the body surface such that dr lt
    dcr

15
Local Force Field Continuum The Force at
Contact Point
16
Local Force Field Continuum Reconstruction of
The Continuum
  • It is required that an interpolation method to
    generate all possible responses from a finite
    set.
  • Division of the surface into triangular patches
  • Two-step process
  • Interpolate the coordinate bases
  • Interpolate the components
  • Weight of interpolation is determined by
    barycentric coordinate.

17
Local Force Field Continuum Reconstruction of
The Continuum
18
Local Force Field Continuum Arbitrary Tool
Contacts
  • Cartesian product of two sets of initial contact
    points
  • One on the tool
  • One on the body

Instrument patch
Body patch
19
Passivity
  • High update rate can resolve passivity problems.
  • But attempting to run all haptic simulations at a
    high rate clearly is a great limitation.
  • Multirate Design for Passivity
  • High Rate Process
  • To evaluate interpolation equations
  • To supply forces to the device
  • Lower Rate Process
  • To supply local data to the high rate process
  • i.e. Collision detection

20
Passivity Multirate Design - Patch Update
  • Aspect of Continuity
  • Well preserved
  • Aspect of Passivity
  • Delayed collision detection causes
  • Deflection inconsistency
  • Tangential force inconsistency
  • Frictionless sliding movement on the surface of a
    nonhomogeneous body with constant penetration

21
Conclusion
  • The continuum reconstruction approach enables
  • To create high-fidelity haptic simulation
  • To reproduce many nonlinear effects of interest
    to surgical simulation
  • Limitations
  • The simulation of contact conditions that have
    been precomputed is available.
  • It can not simulate permanent changes.
  • It does not consider introducing new surfaces at
    runtime.

22
References
  • M. Mahvash and V. Hayward, "High-Fidelity Haptic
    Synthesis of Contact with Deformable Bodies,"
    IEEE Computer Graphics and Applications, vol. 24,
    pp. 48-55, 2004.

23
Supplement St. Venants Principle
  • Definitions
  • The difference between the stresses caused by
    statically equivalent load systems is
    insignificant at distances greater than the
    largest dimension of the area over which the
    loads are acting.
  • The localized effects caused by any load acting
    on the body will dissipate or smooth out within
    regions that are sufficiently away from the
    location of the load.
  • Statically equivalent systems of forces produce
    the same stresses and strains within a body
    except in the immediate region where the loads
    are applied.
Write a Comment
User Comments (0)
About PowerShow.com