Spiral Actuator Tube with Segmented Torsional Rigidity
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Solution Overview
Problem
McKibben-type actuators, used in applications like wearable assist devices, face limitations in freely bending in directions other than their primary flexion direction due to increased rigidity and force requirements with pressure application, restricting their movement and functionality.
Innovation Solution
An actuator body with a spirally wound tube featuring distinct first and second portions with varying torsional rigidity, grooves, and thickness, allowing for flexible deformation and easy bending in multiple directions by adjusting pressure and external forces, while maintaining high torsional rigidity in the primary flexion direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fluid pressure is applied to the inside of the rubber tube in a McKibben-type actuator, then the actuator can perform flexion action, but the actuator is inhibited from freely bending in directions other than flexion direction due to increased rigidity
Solution Approach 1:
The tube is divided into multiple segments with different torsional rigidities along its longitudinal axis. Each segment has distinct structural characteristics (different wall thicknesses or reinforcement patterns) that allow the actuator to exhibit different mechanical properties in different regions, enabling both controlled flexion and free bending in other directions
Solution Approach 2:
Different portions of the tube are designed with locally varied properties: some regions have higher torsional rigidity to maintain structural integrity during flexion, while other regions have lower rigidity to allow free bending. This local differentiation of mechanical properties resolves the contradiction between needing rigidity for flexion and flexibility for multi-directional bending
2Strength
If the tube wall thickness is increased to enhance torsional rigidity, then the actuator can maintain structural integrity during flexion, but the actuator becomes harder to bend in other directions
Solution Approach 1:
The tube wall thickness is segmented along the longitudinal axis, with thicker sections providing high torsional rigidity where structural integrity is needed during flexion, and thinner sections providing bending flexibility where multi-directional movement is desired. This spatial segmentation of wall thickness resolves the contradiction between strength and flexibility
Solution Approach 2:
The tube exhibits local quality variations in wall thickness, creating regions with different mechanical properties. Thicker regions locally enhance torsional rigidity for structural support, while thinner regions locally reduce resistance to bending, allowing the actuator to simultaneously achieve both high strength and adaptability
3Ease of manufacture
If the tube is made uniformly thick to simplify manufacturing, then production is easier, but the actuator cannot achieve both high torsional rigidity and free bending capability
Solution Approach 1:
The manufacturing process is segmented into stages that create different wall thickness regions. The tube is formed with varying thickness profiles through controlled deposition or extrusion processes, allowing complex non-uniform structures to be manufactured systematically. This segmentation of the manufacturing process makes it feasible to produce tubes with spatially varying properties that enable both high torsional rigidity and free bending
Solution Approach 2:
The manufacturing approach dynamically adjusts parameters such as wall thickness during the formation process. By controlling the deposition rate, extrusion pressure, or cooling conditions at different positions along the tube, the manufacturing process can create the desired non-uniform thickness profile, transforming a static manufacturing challenge into a dynamic controllable process
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
Enables the actuator to perform flexion actions with ease and freely bend in directions other than the primary flexion direction, enhancing its versatility and functionality in applications like wearable assist devices without significant increases in pressure or force requirements.
Implementation Method 1
a McKibben-type actuator that stretches and contracts due to pressure of fluid
Implementation Method 2
This actuator is stretched or contracted by converting radial expansion into axial contraction while pressurizing the inside of the rubber tube
Implementation Method 3
each of the plurality of first portions has higher torsional rigidity than each of the plurality of second portions
Implementation Method 4
a tube that has a space therein and is wound spirally about a first axis
Data Source
AI summary
An actuator body includes a tube that has a space therein and is wound spirally about a first axis. The tube has a plurality of first portions and a plurality of second portions, the tube has one or more grooves in at least one of an outer circumferential surface and an inner circumferential surface thereof, and the one or more grooves are provided spirally about a longitudinal axis of the tube, the space is in contact with the inner circumferential surface, and the outer circumferential surface is a surface opposite to the inner circumferential surface, each of the plurality of first portions has higher torsional rigidity than each of the plurality of second portions, the plurality of first portions are aligned along the first axis, and the plurality of first portions do not overlap the plurality of second portions.