Hand Posture Subspaces for Dexterous Robotic Grasping

Dipartimento di Ingegneria dell’Informazione Università degli Studi di Siena

IIT- Genova 24 January 2011

A review of Columbia University’s work

Targets

- Outline affinities with Hands.dvi project

- Underline Ciocarlie and Allen’s results

- Find possible suggestions and define a different

way for our project

Eigengrasps (1/2)

- Low-dimensional hand posture subspaces to express coordination patterns between multiple DOFs for robotic hands

- Based on Santello’s results

- Same meaning of the synergies vectors

- Defined on a 20 DOFs human hand model, the concept has been extended to different robotic hands

- M.T. Ciocarlie and P.K. Allen, “Hand Posture Subspaces for Dexterous Robotic Grasping,” The International Journal of Robotics Research, vol. 28, Jun. 2009, pp. 851-867. - M.T. Ciocarlie, C. Goldfeder, and P.K. Allen, “Dexterous Grasping via Eigengrasps : A Low-dimensional Approach to a High-complexity Problem,” Proceedings of the Robotics: Science & Systems, 2007. - C.Goldfeder, M.T. Ciocarlie, and P.K. Allen, “Dimensionality reduction for hand-independent dexterous robotic grasping,” IROS 07, Citeseer, 2007.

Eigengrasps (2/2)

- Empirical mapping on non-human hands

- Use similarities with human hands

- For Barreth Hand, spread angle DOF mapped into

human finger abduction

Grasp Synthesis through Low-dimensional Posture Optimization (1/5)

- Control algorithms operate on eigengrasp directions and they do not need to be customized for low-level operations

- All of the results presented were obtained by treating all hand models identically, without the need for any hand-specific tuning or change in parameters

- Form closure- Maximization of a high-dimensional quality function

p hand posture, w wrist position and orientation, d number of hand

DOFs

Grasp Synthesis through Low-dimensional Posture Optimization (2/5)

- If d=20 then 26-dimensional optimization domain

- Proposed solution

- New problem

- Only 8 parameters to compute when b=2

Grasp Synthesis through Low-dimensional Posture Optimization (3/5)

- Quality function formulation

- Simulated annealing used for optimization

Grasp Synthesis through Low-dimensional Posture Optimization (4/5)

- Obtained grasps

- Solution: use this result as pre-grasp position and

complete the grasping by closing fingers

Grasp Synthesis through Low-dimensional Posture Optimization (5/5)

- Results

- Number of form-closed grasps obtained from 20 pre-grasps found in a two-dimensional eigengrasp space

On-line Interactive Dexterous Grasping (1/2)

- Remove computation of wrist position through a human operator that move the hand

- Quality Function Formulation using Scaled Contact Wrench Spaces

On-line Interactive Dexterous Grasping (2/2)

M.T. Ciocarlie and P.K. Allen, “On-Line Interactive Dexterous Grasping”

Conclusion

- Definition of pre-grasp position obtained in

synergy subspaces

- Definition of eigengrasps for different hand models

- Form closure grasp obtained from pre-grasp

position

- On-line interactive grasping