Rotational Force Conveyance for Wearable Haptics
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Solution Overview
Problem
Existing force conveyance systems, particularly those using pneumatic pressure and external robots, fail to accurately convey forces to the finger while allowing natural hand movement due to directional limitations and restricted mobility.
Innovation Solution
A force conveyance system comprising a hand-back-wearable unit with an active unit generating rotational force, an active link with 2 degrees of freedom, a passive link with 3 degrees of freedom, and a finger-wearable unit, along with sensors and a controller to estimate fingertip position and adjust rotational force, enabling 6 degrees of freedom for accurate force transmission without obstructing finger movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a pneumatic pressure system with a piston is used to convey force to a finger, then force can be conveyed to the user, but the direction of force acting on the finger is not perpendicular to the hand and the movement range of the hand is restricted due to the length of the piston
Solution Approach 1:
The patent replaces the traditional pneumatic pressure system with a rotational force generation system. Instead of using linear piston movement to convey force, the system uses rotational joints and links that can accommodate natural hand movements while maintaining force conveyance capability. The rotational mechanism allows the force to be applied in the correct perpendicular direction to the hand regardless of hand position.
Solution Approach 2:
The system dynamically adapts to hand movement through rotational joints and links. The rotational coupling allows the force transmission mechanism to adjust its orientation automatically as the hand moves, maintaining both force accuracy and movement freedom. The dynamic configuration ensures the force direction remains perpendicular to the hand surface throughout the range of motion.
2Force
If an external robot is used to convey force to a hand, then force can be conveyed, but the user cannot freely move their arm and mobility is restricted due to its large size
Solution Approach 1:
The system is divided into multiple small modular components including rotational joints, links, and sensors that can be distributed across the hand structure. This segmentation replaces the single large external robot with multiple small integrated units, enabling force conveyance while maintaining user mobility and natural arm movement.
Solution Approach 2:
The force conveyance mechanism is nested within the hand structure itself. The rotational joints and links are integrated into the wearable device that fits on the hand, with components nested within each other to minimize size and weight. This nested configuration allows the system to convey force without restricting user mobility.
3Force
If the movement range of the hand is restricted due to the length of the piston, then force direction can be controlled, but natural hand movement is limited
Solution Approach 1:
The system transitions from linear piston movement to rotational movement in a different dimension. Instead of constraining hand movement along a linear path determined by piston length, the rotational mechanism allows movement in multiple angular dimensions while maintaining force direction control through the rotational joint configuration.
Data Source
AI summary
Provided is a force conveyance system that is configured to have 6 degrees of freedom, thereby allowing freedom of movement such as opening/closing of a hand and adduction/abduction of a finger and reflecting a desired force to a fingertip without obstructing the movement of a finger. Also, the force conveyance system may estimate a fingertip position and a finger joint angle, measure a finger movement, and convey a more accurate force accordingly.