Multijoint Motion Assisting Apparatus with Linear Member
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Solution Overview
Problem
Existing finger motion assisting devices struggle to apply sufficient fingertip force for holding objects, especially when the fingers are in a relaxed state, due to limitations in power transmission and flexibility, making it difficult to securely hold heavy objects like a plastic bucket containing 4 kg of items.
Innovation Solution
A multijoint structure with a linear member and a drive unit that allows for bidirectional motion control, enabling the transmission of power along the finger surface, with a sliding/holding part and a control unit that adjusts the sliding direction, speed, and position to assist both flexing and extending motions, and includes a locking mechanism for safety and a biosignal detection unit for voluntary control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a linear member is used to transmit power along the finger surface, then the device can assist finger motion, but it cannot apply sufficient fingertip force (9.8 N or more) in a relaxed state
Solution Approach 1:
The patent employs a dynamic transmission ratio mechanism where the gear ratio changes based on the finger joint angle. When the finger is in a relaxed state with smaller bending angle, the system provides a larger transmission ratio to amplify the actuator's output force, enabling sufficient fingertip force (9.8 N or more) to be applied even when the user's muscle force is minimal. This dynamic adjustment resolves the contradiction between maintaining relaxed operation and generating adequate holding force.
2Manufacturing precision
If the mounting part is manufactured to match individual finger joint lengths, then the device fits individuals well, but it is difficult to swiftly apply the device to persons suffering from finger paralysis
Solution Approach 1:
The patent segments the mounting structure into multiple adjustable components that can be configured to match different finger joint lengths. The mounting part includes adjustable linkages and connection points that allow rapid adaptation to individual anatomical variations without requiring custom manufacturing for each user. This segmentation enables swift application to multiple persons while maintaining precise fit for each individual's finger dimensions.
3Reliability
If power is transmitted along the finger surface at all times, then holding motion can be assisted, but the device structure becomes complex
Solution Approach 1:
The patent introduces a multijoint structure with linear members that act as intermediaries between the actuator and the finger. These linear members are inserted through the multijoint structure and can be extended or retracted to transmit power along the finger surface when needed, while retracting when not in use. This intermediary mechanism enables reliable holding motion assistance only when required, avoiding the need for continuously active complex power transmission structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus effectively applies a holding force of 9.8 N or more to the fingertips, allowing secure grasping of objects, even in a relaxed state, with a simple configuration that is adjustable to fit individual finger lengths and ensures safety by preventing excessive motion.
Implementation Method 1
When sliding the rear link toward the sliding/holding part in a direction which compresses the space between the respective links, the linear member is extended so as to pull the front link and cause the multijoint structure to engage in a bending motion on the one hand, and, when sliding the rear link toward the sliding/holding part in a direction which decompresses the space between the respective links, the linear member is loosened so as to cause the multijoint structure to engage in an extending motion
Implementation Method 2
the drive unit includes an actuator in which a pulley having a predetermined diameter is engaged with an output axis; and a power line which is stretched between the pulley and a fixed axis of the sliding/holding part, and fixed and connected to the pulley, and rotative force of the output axis of the actuator is transmitted as linear motion to the rear link which is fixed to a part of the power line via the pulley
Data Source
AI summary
A motion assisting apparatus includes a multijoint structure having links in series rotatably connected in a relative manner, the links being integrally deformed in a bendable manner, a linear member inserted through each of the links, wherein one end is fixed to the link in front and another end is elongated via the link in rear, a sliding/holding part which fixes an elongated portion of the linear member, and slidably guides the rear link in a connecting direction between each of the links, a drive unit which drives the rear link to slide toward the sliding/holding part and causes the multijoint structure, through which the linear member has been inserted, to engage in an extending or flexing motion, and a control unit which drive-controls the drive unit so that a sliding direction, a sliding speed and a sliding position of the rear link will become an intended state.