Title: Friction Rendering : A New Computational Model of Friction Applied to Haptic Rendering
1Friction Rendering A New Computational Model of
Friction Applied to Haptic Rendering
- Han, Gabjong
- hkj84_at_postech.ac.kr
- POSTECH VR Lab
- 2006. 5. 29.
2Outline
- Introduction
- Previous Models
- An Online Discrete Scalar Model
- A Discrete Vectorial Model
- Experimental Results
- Conclusion
3Introduction - Motivation
- Friction occurs when two objects are in contacts
- Previous approach
- Add dynamic friction effects depending on time or
on state - Proposed method
- Make autonomous friction model whose computation
is based on displacements
4Introduction - Contributions
- It is autonomous
- It neither drifts, nor relaxes
- It is robust to noise
- It is computationally efficient
- It accounts for vector motions and forces
- It has four regimes
- Its parameters have physical meaning
- It has continuous counterpart
5Previous Models Basic Model
- Use mass-spring behavior
- Add damping term
- Add viscosity
- z w-x, v dx/dt
6Previous Models Bristle Model
- Compute bristles deflection effect
- Bristles deflection model
-
- v is relative velocity
- g(v) depends on material property
- Steady state condition
-
7Previous Models Seven Parameter Model
- Seven parameters
- s0, s1, s2, Fc, Fs, vs and v
- Simulate Stribeck effect
-
- Fc is Coulomb friction force
- Fs is Stribeck friction force
- vs is Stribeck velocity
8Previous Models Integrated Model
- Steady state situation
- Basic Bristle Stribeck model
- Integrated model
9Previous Models Dahls Model
- Use a differential equation
- Account for Coulomb friction
- Basic Bristle model
-
-
10Previous Models General Dahls Model
-
- Change the converging rate of F
- Take i 1, s0 1 and a F / Fc for simple
computation -
11An Online Discrete Scalar Model Autonomous Form
of Dahls Model
- Eliminating time
- In drifting situation
-
-
12An Online Discrete Scalar Model Drift Problem
- Drift occurs when a small cycle exists
- Drift-free friction model
- Have no minor paths
- Make a depend on z
-
13An Online Discrete Scalar Model Simple Model
14An Online Discrete Scalar Model Simple Model
- Stick-slide
- No integration to Stick-slide
- Two regimes stuck and sliding
- a(z) 0 for z lt zmax
- a(z) 1 elsewhere
15An Online Discrete Scalar Model General Model
- Integration to displacements
-
- Stick-slip-slide
- Three regimes stuck, sliding and oscillating
- a(z) 0 for z lt zstick
- a(z) 1 elsewhere
16An Online Discrete Scalar Model General Model
- Stick-creep-slip-slide
- Four regimes stuck, sliding and oscillating and
creeping - Function of a(z)
- Stick-gtcreeping-gtsliping-gtoscillrating-gtreversal-
gtfast-moving
17A Discrete Vectorial Model- Simple Model
- Point is vector model
- Z X-W
-
- Straightforward
18A Discrete Vectorial Model- General Model
- Direction must be updated before W
-
-
-
19Experimental Results - Setup
- Using PenCat haptic device
- 400 Hz update rate
- Haptic Technologies Inc.
- 3D vector test
20Experimental Results - First Experiment
- Using HIP as virtual pointer
- Z values represented by the set of lines
21Experimental Results - Second Experiment
- Actual test for general model
- X-Z plot
22Conclusion
- No drifts
- Autonomous
- Robust to noise
- Suitable for event-based interfaces
- Directly implementable
- Extension for 2D and 3D
- Showing four physical behaviors
23Reference
- Hayward, V. Armstrong, B. "A New Computational
Model of Friction Applied to Haptic Rendering."
Experimental Robotics VI, PP. Corke and J.
Trevelyan (Eds.), Springer, New York, 2000,
pp.404-412. - C. Canudas, H. Olsson, K.J. Astr om, and P.
Lischinsky. A new-model for control of systems
with friction. IEEE Transactions on Automatic
Control, 40(3)419--425, 1995.
24QnA