Grasp-Oriented Non-Prehensile Manipulation via Learning a Graspability Field
Pith reviewed 2026-06-30 05:14 UTC · model grok-4.3
The pith
Learning a graspability field lets one reinforcement learning policy reconfigure objects for grasping without predefined poses or external planners.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
A graspability field constructed from synthesized grasps supplies a scalar measure of how suitable any object configuration is for grasp execution. Training a reinforcement learning policy to maximize this measure produces a single controller that manipulates objects into graspable states and automatically switches to grasping once the field value indicates readiness, eliminating the need for target poses, external planners, or manually specified stopping conditions. The same field values correlate with real-world grasp success.
What carries the argument
The graspability field: a scalar function over object configurations that quantifies grasp feasibility, derived from a set of synthesized grasps and used both as reinforcement learning reward and termination criterion.
If this is right
- A single policy suffices for the full sequence from non-prehensile reconfiguration to grasp execution.
- Manipulation terminates automatically when the graspability field reaches a suitable threshold.
- No separate external planner or manually chosen target pose is required.
- The learned field values serve as a predictor of real-world grasp success.
Where Pith is reading between the lines
- The same field-based objective could be applied to prepare objects for other actions besides grasping.
- Replacing discrete pose targets with continuous feasibility fields may simplify other multi-stage robotic tasks.
- Expanding the set of synthesized grasps to cover more object geometries would test how far the current construction generalizes.
Load-bearing premise
The graspability field built from synthesized grasps accurately reflects real-world grasp feasibility and transfers from simulation to physical robots.
What would settle it
Physical-robot trials in which the policy's graspability values show no correlation with measured grasp success rates would falsify the claim that the field captures usable grasp feasibility.
Figures
read the original abstract
Non-prehensile manipulation is often used as a preparatory step for robotic grasping, yet existing approaches typically require a predefined target object pose. In practice, however, objects admit multiple graspable configurations and the desired pose is not known in advance. We reformulate non-prehensile manipulation for grasping as optimizing an object centric graspability objective rather than reaching a specific pose. We construct a graspable set from synthesized grasps and define a graspability field that measures how suitable an object configuration is for successful grasp execution. The scalar measure provides a dense learning signal for reinforcement learning and determines when to terminate manipulation. This yields a closed-loop manipulation-to-grasp pipeline driven by a single policy. Experiments in simulation and on a real robot show that the policy reliably reconfigures objects into graspable states and transitions to grasping without external planners or manually specified stopping conditions. The predicted graspability distance correlates with real world grasp success, which indicates that the learned representation captures grasp feasibility of object configurations.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes reformulating non-prehensile manipulation as optimization of an object-centric graspability objective rather than a target pose. A graspability field is constructed from synthesized grasps to supply a dense RL reward signal and an automatic termination condition, yielding a single closed-loop policy that reconfigures objects into graspable states and transitions to grasping. Experiments in simulation and on a physical robot are reported to show reliable performance and correlation between the predicted graspability distance and real-world grasp success.
Significance. If the generalization claims hold, the work offers a unified objective for preparatory manipulation and grasping that removes the need for separate pose planners or hand-crafted stopping rules, which could simplify pipelines for robotic manipulation in unstructured settings.
major comments (3)
- [Abstract] Abstract: the central claim that the graspability field 'captures grasp feasibility of object configurations' and enables reliable real-robot transfer rests on correlation with grasp success, yet no quantitative metrics (e.g., Pearson coefficient, success-rate tables, or failure-case analysis) are supplied to establish that the correlation is not driven by shared simulation artifacts.
- [§3] The construction of the graspable set from synthesized grasps (presumably §3) defines the field via simulation-based synthesis; any unmodeled mismatch in friction, contact compliance, or sensor noise creates a domain gap that directly affects both the RL reward and the termination signal, yet the manuscript provides no ablation on domain-randomization strength or sim-to-real transfer metrics.
- [§5] Experiments section: the assertion that the policy 'transitions to grasping without external planners or manually specified stopping conditions' is load-bearing for the closed-loop contribution, but no comparison against baselines that use explicit termination or separate grasp planners is reported, leaving the advantage of the single-policy formulation unquantified.
minor comments (2)
- [§3] Notation for the graspability scalar and distance should be introduced with a clear equation reference rather than prose description only.
- [§5] Figure captions for real-robot trials should list the number of objects, trials per object, and success criteria to allow reproducibility assessment.
Simulated Author's Rebuttal
We thank the referee for the thoughtful comments, which help clarify the strength of our claims on correlation, domain transfer, and the benefits of the unified policy. We respond to each major comment below.
read point-by-point responses
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Referee: [Abstract] Abstract: the central claim that the graspability field 'captures grasp feasibility of object configurations' and enables reliable real-robot transfer rests on correlation with grasp success, yet no quantitative metrics (e.g., Pearson coefficient, success-rate tables, or failure-case analysis) are supplied to establish that the correlation is not driven by shared simulation artifacts.
Authors: We agree that the abstract would benefit from explicit quantitative support. The manuscript body reports real-robot grasp success rates conditioned on graspability values, but we will revise the abstract to include a Pearson correlation coefficient between predicted graspability distance and observed grasp success, plus a table of success rates across binned graspability thresholds in both simulation and on the physical robot. Failure cases will also be briefly analyzed to address potential simulation artifacts. revision: yes
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Referee: [§3] The construction of the graspable set from synthesized grasps (presumably §3) defines the field via simulation-based synthesis; any unmodeled mismatch in friction, contact compliance, or sensor noise creates a domain gap that directly affects both the RL reward and the termination signal, yet the manuscript provides no ablation on domain-randomization strength or sim-to-real transfer metrics.
Authors: The current manuscript demonstrates successful sim-to-real transfer through physical robot experiments, but we concur that dedicated ablations on randomization strength are absent. We will add an ablation varying domain randomization parameters (friction, compliance, noise) and report the resulting sim-to-real success rates and graspability prediction accuracy to quantify robustness to the domain gap. revision: yes
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Referee: [§5] Experiments section: the assertion that the policy 'transitions to grasping without external planners or manually specified stopping conditions' is load-bearing for the closed-loop contribution, but no comparison against baselines that use explicit termination or separate grasp planners is reported, leaving the advantage of the single-policy formulation unquantified.
Authors: The experiments show reliable closed-loop behavior on the real robot using only the learned graspability signal for both reward and termination. However, we acknowledge that the advantage over pipelines with explicit termination rules remains unquantified without direct baselines. Adding such comparisons would require substantial additional implementation and fair metric alignment; we will therefore expand the discussion section to address this limitation and identify it as future work rather than performing new baseline experiments in the revision. revision: partial
Circularity Check
No circularity: graspability field constructed independently from synthesized grasps and validated externally
full rationale
The paper constructs a graspable set from synthesized grasps and defines a graspability field as a scalar measure of configuration suitability for grasping. This field supplies a dense RL reward and termination signal, with the resulting policy evaluated in simulation and on physical robots where predicted distances correlate with real grasp success. No derivation step reduces by construction to fitted parameters from the same data, self-citations, or renamed inputs; the chain relies on external synthesis and physical validation rather than self-definition. This is the most common honest outcome for papers whose central quantities are defined upstream of the learning loop and tested against independent benchmarks.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Synthesized grasps can define a graspable set that supports learning a generalizable field for real-world use.
invented entities (1)
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graspability field
no independent evidence
Reference graph
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