Digital Mannequin Grasp Positioning With Flexible Hand-Tool Constraints
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Solution Overview
Problem
Current digital human modeling systems lack an automated solution for determining task-oriented grasping of tools, as existing methods either dissociate hand positioning from whole-body posture or require user intervention, leading to less plausible and ergonomically acceptable postures.
Innovation Solution
The implementation of a flexible cylindrical hand-tool constraint that simultaneously optimizes hand grasp and whole-body posture, allowing for degrees of freedom that adapt to tool geometrical features and intended actions, using an inverse kinematic solver to determine the optimal posture with minimal deviation from a neutral position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hand grasp and whole-body posture are treated separately in digital human modeling, then the modeling process is simpler, but the resulting postures are less plausible and ergonomically acceptable
Solution Approach 1:
The patent combines hand grasp determination and whole-body posture optimization into a unified framework. The flexible cylindrical constraint integrates both hand positioning and body posture into a single constraint system, allowing simultaneous optimization rather than separate processing, thereby improving posture plausibility while maintaining manageable complexity through systematic integration.
Solution Approach 2:
The flexible cylindrical constraint serves multiple functions simultaneously: it defines hand grasp geometry, allows rotational freedom for natural hand orientation, and optimizes whole-body posture. This multi-functional constraint replaces multiple separate constraints, achieving comprehensive posture control without proportionally increasing system complexity.
2Measurement precision
If automated tool grasping is implemented with flexible constraints, then task-oriented grasping accuracy improves, but computational complexity increases
Solution Approach 1:
The patent changes the constraint parameters from rigid fixed-position constraints to flexible cylindrical constraints with rotational degrees of freedom. This parameter change allows the hand to rotate naturally around the tool axis while maintaining grasp accuracy, achieving task-oriented precision without requiring overly complex computational models.
Solution Approach 2:
The flexible cylindrical constraint introduces dynamic rotational capability to the hand-tool interaction model. Instead of static fixed grasps, the system allows dynamic rotation around the tool axis, enabling task-oriented adjustment while maintaining computational tractability through a well-defined constraint structure.
3Manufacturing precision
If rigid hand-tool constraints are used, then hand positioning is more precise, but whole-body posture becomes less ergonomic
Solution Approach 1:
The patent segments the constraint into two independent components: a cylindrical constraint for hand positioning precision and a rotational degree of freedom for ergonomic adjustment. This segmentation allows the hand position to be precisely controlled relative to the tool while the rotation angle can be optimized for ergonomic body posture, resolving the contradiction between precision and ergonomics.
Solution Approach 2:
The rotational degree of freedom introduces dynamics to the hand-tool constraint, allowing the hand orientation to adapt dynamically for ergonomic positioning while maintaining precise hand-to-tool contact. This dynamic capability enables the system to achieve both positioning precision and ergonomic acceptability simultaneously.
Data Source
AI summary
Embodiments determine positioning of a mannequin. One such embodiment begins by determining a frame of a grasping element of a mannequin represented by a computer-aided design (CAD) model and determining a frame of an object to be grasped, where is object is also represented by a CAD model. To continue, degrees of freedom of the mannequin are specified and limits on the specified degrees of freedom are set. In turn, using an inverse kinematic solver, positioning of the mannequin grasping the object is determined based upon: (i) the determined frame of the grasping element, (ii) the determined frame of the object, (iii) the specified degrees of freedom, and (iv) the set limits on the specified degrees of freedom.