Estimation of the Caged Object's Posture under Forces Using Stepwise Geometric Calculations
Ryota Yokomura, Yutong Liu, Rui Fukui
AI summary
Problem
Existing contact models are computationally expensive and numerically unstable for small gaps, while research on three-dimensional caged object behavior under external forces remains limited.
Approach
The method approximates pose changes of caged 3D objects as stepwise rotations or translations about contact points using simple geometric calculations, handling slipping via surface normal angles.
Key results
- Pose estimation matches theoretical and force-based solutions for simple and small-clearance objects
- Computation completes within 0.6 seconds, proving practical efficiency
- Framework models slipping and stability via conditional branching on contact normals
- Enables relative pose correction without precise force control or high-DOF manipulators
Why it matters
Enables reliable, low-cost robotic assembly using simple position control by eliminating the need for complex force regulation or high-precision alignment mechanisms.
Abstract
In pin–hole assembly processes, precise alignment or compliance mechanisms are typically required. This paper proposes a method for connecting objects by utilizing caging to constrain their motion, enabling the insertion of a pin into a hole to adjust the allowable relative pose for assembly. This approach eliminates the need for force control, even with low- degree-of-freedom manipulators, and reduces deflection caused by misalignment during connection. Although previous research has extensively studied appropriate finger configurations for caging, the behavior of caged objects under external forces remains insufficiently investigated. Furthermore, when connect- ing caged objects by contact, pose estimation often requires complex collision computations that account for intricate object geometries, which are computationally expensive and may fail to converge when small gaps are present. To address this issue, we propose a geometric method that approximates pose changes of caged three-dimensional objects under external forces as rotations about contact points. As a representative case, we focus on objects composed of cuboid ele- ments. The estimated results for simple objects, including caged objects with small clearances, were consistent with geometrically derived theoretical solutions, and are obtained within 0.6 seconds, indicating a practical computation time.