Prioritized Independent Contact Regions for Form Closure Grasps - - PowerPoint PPT Presentation

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Prioritized Independent Contact Regions for Form Closure Grasps - - PowerPoint PPT Presentation

Mar 16, 2023 162 likes •726 views

Prioritized Independent Contact Regions for Form Closure Grasps Robert Krug, Dimitar Dimitrov, Krzysztof Charusta and Boyko Iliev Center for Applied Autonomous Sensor Systems (AASS) rebro University, Sweden robert.krug@oru.se Robert Krug

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Prioritized Independent Contact Regions for Form Closure Grasps

Robert Krug, Dimitar Dimitrov, Krzysztof Charusta and Boyko Iliev

Center for Applied Autonomous Sensor Systems (AASS) Örebro University, Sweden

robert.krug@oru.se

Robert Krug IROS 2011 1 / 17

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Independent Contact Regions (ICR)

Impossible to position the fingers of a grasping device precisely at the desired contact locations

Robert Krug IROS 2011 2 / 17

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Independent Contact Regions (ICR)

Impossible to position the fingers of a grasping device precisely at the desired contact locations Representation of a grasp as a set of regions [Nguyen, 1986] Each region is associated with

  • ne finger

Robert Krug IROS 2011 2 / 17

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Independent Contact Regions (ICR)

Impossible to position the fingers of a grasping device precisely at the desired contact locations Representation of a grasp as a set of regions [Nguyen, 1986] Each region is associated with

  • ne finger

If each finger is placed within its respective region . . . . . . certain grasp properties are preserved

Robert Krug IROS 2011 2 / 17

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Independent Contact Regions (ICR)

Impossible to position the fingers of a grasping device precisely at the desired contact locations Representation of a grasp as a set of regions [Nguyen, 1986] Each region is associated with

  • ne finger

If each finger is placed within its respective region . . . . . . certain grasp properties are preserved

Robert Krug IROS 2011 2 / 17

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Independent Contact Regions (ICR)

Impossible to position the fingers of a grasping device precisely at the desired contact locations Representation of a grasp as a set of regions [Nguyen, 1986] Each region is associated with

  • ne finger

If each finger is placed within its respective region . . . . . . certain grasp properties are preserved

Robert Krug IROS 2011 2 / 17

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Independent Contact Regions (ICR)

Impossible to position the fingers of a grasping device precisely at the desired contact locations Representation of a grasp as a set of regions [Nguyen, 1986] Each region is associated with

  • ne finger

If each finger is placed within its respective region . . . . . . certain grasp properties are preserved

Robert Krug IROS 2011 2 / 17

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SLIDE 8

Independent Contact Regions (ICR)

Impossible to position the fingers of a grasping device precisely at the desired contact locations Representation of a grasp as a set of regions [Nguyen, 1986] Each region is associated with

  • ne finger

If each finger is placed within its respective region . . . . . . certain grasp properties are preserved Regions are not unique

Robert Krug IROS 2011 2 / 17

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Motivation

Outline

1

Motivation

2

Concept Wrench Spaces Approximating the EWS

3

Algorithm

4

Numerical Evaluation

5

Summary & Outlook

Robert Krug IROS 2011 3 / 17

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Motivation

Current Methods [Pollard, 2004] [Roa and Suárez, 2009] [Krug et al., 2010]

Regions are represented by sets of contact points on a discretized object

Robert Krug IROS 2011 4 / 17

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Motivation

Current Methods [Pollard, 2004] [Roa and Suárez, 2009] [Krug et al., 2010]

Regions are represented by sets of contact points on a discretized object A grasp family is synthesized from a prototype force-closure grasp . . . . . . using simple heuristics

Robert Krug IROS 2011 4 / 17

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Motivation

Current Methods [Pollard, 2004] [Roa and Suárez, 2009] [Krug et al., 2010]

Regions are represented by sets of contact points on a discretized object A grasp family is synthesized from a prototype force-closure grasp . . . . . . using simple heuristics Expected disturbances are considered Frictionless/frictional & soft finger point contact models are eligible

Robert Krug IROS 2011 4 / 17

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Motivation

Current Methods [Pollard, 2004] [Roa and Suárez, 2009] [Krug et al., 2010]

Regions are represented by sets of contact points on a discretized object A grasp family is synthesized from a prototype force-closure grasp . . . . . . using simple heuristics Expected disturbances are considered Frictionless/frictional & soft finger point contact models are eligible Problem: Strong conditioning on the prototype grasp → number & distribution

  • f points forming the regions are often undesirable

Robert Krug IROS 2011 4 / 17

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Motivation

Presented approach

General idea: Specify a desired grasp family

⇒ validate it against expected disturbances

Robert Krug IROS 2011 5 / 17

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Motivation

Presented approach

General idea: Specify a desired grasp family

⇒ validate it against expected disturbances

Or, alternatively: Synthesize a grasp family from a prototype grasp

Robert Krug IROS 2011 5 / 17

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Motivation

Presented approach

General idea: Specify a desired grasp family

⇒ validate it against expected disturbances

Or, alternatively: Synthesize a grasp family from a prototype grasp Resulting regions are less dependent on the prototype grasp

Robert Krug IROS 2011 5 / 17

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Motivation

Presented approach

General idea: Specify a desired grasp family

⇒ validate it against expected disturbances

Or, alternatively: Synthesize a grasp family from a prototype grasp Resulting regions are less dependent on the prototype grasp Formal definition of resistible disturbances w.r.t. grasp families . . . . . . and an efficient way to approximate them

Robert Krug IROS 2011 5 / 17

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Motivation

Presented approach

General idea: Specify a desired grasp family

⇒ validate it against expected disturbances

Or, alternatively: Synthesize a grasp family from a prototype grasp Resulting regions are less dependent on the prototype grasp Formal definition of resistible disturbances w.r.t. grasp families . . . . . . and an efficient way to approximate them The frictionless point contact model is used

Robert Krug IROS 2011 5 / 17

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Concept

Outline

1

Motivation

2

Concept Wrench Spaces Approximating the EWS

3

Algorithm

4

Numerical Evaluation

5

Summary & Outlook

Robert Krug IROS 2011 6 / 17

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Concept Wrench Spaces

The Grasp Wrench Space (GWS)

Which disturbance wrenches can a single grasp resist?

Robert Krug IROS 2011 7 / 17

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Concept Wrench Spaces

The Grasp Wrench Space (GWS)

Assuming the frictionless point contact model . . .

Robert Krug IROS 2011 7 / 17

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Concept Wrench Spaces

The Grasp Wrench Space (GWS)

Assuming the frictionless point contact model . . .

τs = (ps ×f s), ws = f s τs

  • Robert Krug

IROS 2011 7 / 17

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Concept Wrench Spaces

The Grasp Wrench Space (GWS)

Assuming the frictionless point contact model . . .

Robert Krug IROS 2011 7 / 17

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Concept Wrench Spaces

The Grasp Wrench Space (GWS)

Grasp Wrench Space (GWS) → Wrenches exertable by a single grasp

Robert Krug IROS 2011 7 / 17

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Concept Wrench Spaces

The Grasp Wrench Space (GWS)

GWS → mirror image of resistible disturbance wrenches

Robert Krug IROS 2011 7 / 17

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Concept Wrench Spaces

The Exertable Wrench space (EWS)

Which disturbance wrenches can a grasp family resist?

Robert Krug IROS 2011 8 / 17

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Concept Wrench Spaces

The Exertable Wrench space (EWS)

Consider adding points to ICR / grasp members to the grasp family

Robert Krug IROS 2011 8 / 17

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Concept Wrench Spaces

The Exertable Wrench space (EWS)

Consider adding points to ICR / grasp members to the grasp family

Robert Krug IROS 2011 8 / 17

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Concept Wrench Spaces

The Exertable Wrench space (EWS)

The Exertable Wrench Space → analogue to the GWS for single grasps

Robert Krug IROS 2011 8 / 17

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Concept Wrench Spaces

The Exertable Wrench space (EWS)

Mirror image of the disturbances resistible by every member of a grasp family

Robert Krug IROS 2011 8 / 17

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Concept Wrench Spaces

The Exertable Wrench space (EWS)

Intersection of the GWS corresponding to members of the grasp family EWS

=

  • {GWS1,...,GWSV}

V =

# of grasp family members

Robert Krug IROS 2011 8 / 17

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Concept Wrench Spaces

The Task Wrench Space (TWS)

How to take expected disturbances into account?

Robert Krug IROS 2011 9 / 17

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Concept Wrench Spaces

The Task Wrench Space (TWS)

How to take expected disturbances into account? TWS → wrenches necessary to counter expected disturbances

Robert Krug IROS 2011 9 / 17

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Concept Wrench Spaces

The Task Wrench Space (TWS)

How to take expected disturbances into account? TWS → wrenches necessary to counter expected disturbances EWS of a specified desired grasp family has to contain the TWS

Robert Krug IROS 2011 9 / 17

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Concept Approximating the EWS

Approximating the EWS

Computing the EWS is costly (computing & intersecting V convex hulls )

Robert Krug IROS 2011 10 / 17

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Concept Approximating the EWS

Approximating the EWS

Computing the EWS is costly (computing & intersecting V convex hulls ) Approximate confining hyperplanes . . .

Robert Krug IROS 2011 10 / 17

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Concept Approximating the EWS

Approximating the EWS

Computing the EWS is costly (computing & intersecting V convex hulls ) Approximate confining hyperplanes . . . . . . by solving Quadratic Programs (QP’s)

Robert Krug IROS 2011 10 / 17

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Concept Approximating the EWS

Approximating the EWS

Computing the EWS is costly (computing & intersecting V convex hulls ) Approximate confining hyperplanes . . . . . . by solving Quadratic Programs (QP’s) Current Methods → Approximation based

  • n the prototype grasp’s GWS

Robert Krug IROS 2011 10 / 17

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Algorithm

Outline

1

Motivation

2

Concept Wrench Spaces Approximating the EWS

3

Algorithm

4

Numerical Evaluation

5

Summary & Outlook

Robert Krug IROS 2011 11 / 17

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Algorithm

Variant 1 - validate a predefined grasp family

Robert Krug IROS 2011 12 / 17

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Algorithm

Variant 1 - validate a predefined grasp family

Input:

Desired contact regions Expected disturbances (formulated as a TWS)

Robert Krug IROS 2011 12 / 17

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Algorithm

Variant 1 - validate a predefined grasp family

Input:

Desired contact regions Expected disturbances (formulated as a TWS)

Output: Approximated EWS

Robert Krug IROS 2011 12 / 17

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Algorithm

Variant 2 - Synthesize a valid grasp family

Input:

Prototype grasp Expected disturbances (formulated as a TWS) Logic for sequential point inclusion

Robert Krug IROS 2011 13 / 17

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Algorithm

Variant 2 - Synthesize a valid grasp family

Input:

Prototype grasp Expected disturbances (formulated as a TWS) Logic for sequential point inclusion

Output: Approximated EWS Iterative grasp family evaluation

Robert Krug IROS 2011 13 / 17

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Algorithm

Variant 2 - Synthesize a valid grasp family

Input:

Prototype grasp Expected disturbances (formulated as a TWS) Logic for sequential point inclusion

Output: Approximated EWS Iterative grasp family evaluation Also allows for fixed regions

Robert Krug IROS 2011 13 / 17

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Numerical Evaluation

Outline

1

Motivation

2

Concept Wrench Spaces Approximating the EWS

3

Algorithm

4

Numerical Evaluation

5

Summary & Outlook

Robert Krug IROS 2011 14 / 17

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Numerical Evaluation

Comparison to Current Methods

Comparison via 100 randomly generated 7-fingered form-closure grasps

Robert Krug IROS 2011 15 / 17

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Numerical Evaluation

Comparison to Current Methods

Comparison via 100 randomly generated 7-fingered form-closure grasps 3 times larger independent regions

Robert Krug IROS 2011 15 / 17

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Numerical Evaluation

Comparison to Current Methods

Comparison via 100 randomly generated 7-fingered form-closure grasps 3 times larger independent regions 2 orders of magnitude higher computation times

Robert Krug IROS 2011 15 / 17

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Summary & Outlook

Outline

1

Motivation

2

Concept Wrench Spaces Approximating the EWS

3

Algorithm

4

Numerical Evaluation

5

Summary & Outlook

Robert Krug IROS 2011 16 / 17

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Summary & Outlook

Summary & Outlook

Contributions: Methods to evaluate/synthesize grasp families w.r.t. disturbances

Robert Krug IROS 2011 17 / 17

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Summary & Outlook

Summary & Outlook

Contributions: Methods to evaluate/synthesize grasp families w.r.t. disturbances Allow for arbitrary object geometries . . . . . . utilizing the frictionless point contact model

Robert Krug IROS 2011 17 / 17

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Summary & Outlook

Summary & Outlook

Contributions: Methods to evaluate/synthesize grasp families w.r.t. disturbances Allow for arbitrary object geometries . . . . . . utilizing the frictionless point contact model Extension of the GWS (for single grasps) to the Exertable Wrench Space (for sets

  • f grasps)

Robert Krug IROS 2011 17 / 17

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Summary & Outlook

Summary & Outlook

Contributions: Methods to evaluate/synthesize grasp families w.r.t. disturbances Allow for arbitrary object geometries . . . . . . utilizing the frictionless point contact model Extension of the GWS (for single grasps) to the Exertable Wrench Space (for sets

  • f grasps)

Future Work:

⇒ Incorporate point contact with friction

Robert Krug IROS 2011 17 / 17

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References

References

Krug, R., Dimitrov, D., Charusta, K., and Iliev, B. (2010). On the efficient computation of icr for force closure grasps. In Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems, pages 586–591. Nguyen, V.-D. (1986). Constructing force-closure grasps. In Proceedings of the IEEE International Conference on Robotics and Automation, volume 3, pages 1368–1373. Pollard, N. S. (2004). Closure and quality equivalence for efficient synthesis of grasps from examples. International Journal of Robotics Research, 23(6):595–614. Roa, M. A. and Suárez, R. (2009). Computation of independent contact regions for grasping 3-d objects. IEEE Transactions on Robotics, 25:839–850.

Robert Krug IROS 2011 17 / 17