Spiral-Cable Soft Actuator for Precise Motion Without Ballooning
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Solution Overview
Problem
Existing soft actuators have limited degrees of freedom and variable stiffness, which restricts their range of motion and precision, and often suffer from 'ballooning' and fatigue issues due to non-uniform cross-sectional changes during movement.
Innovation Solution
A soft actuator design featuring a body portion with pressurizable chambers and cables arranged in a partial spiral configuration, allowing for precise movement control through axial and tangential force components, and adjustable stiffness via pressure control, enabling four degrees of freedom and preventing ballooning through a rigidifying reinforcing member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If soft pneumatic actuators are used to provide compliant movement, then adaptability and agility are improved, but ballooning occurs causing non-uniform cross-sectional changes and subsequent fatigue
Solution Approach 1:
The actuator employs a flexible membrane as the chamber wall that can deform under pressure while maintaining structural integrity. The membrane is constrained by a rigidifying member that prevents uncontrolled expansion, allowing the soft actuator to achieve compliant movement without the damaging ballooning effect that causes fatigue
Solution Approach 2:
The actuator combines soft compliant materials (membrane, flexible housing) with a rigidifying reinforcing member to create a composite structure. This composite design allows the actuator to benefit from the compliance of soft materials while the rigidifying member prevents excessive deformation and maintains uniform cross-section during actuation
2Adaptability or versatility
If a single soft actuator is designed to provide multiple degrees of freedom, then design choices and range of motion are improved, but structural complexity increases
Solution Approach 1:
The actuator is designed with a multi-functional cable system where cables arranged in spiral configurations serve multiple purposes: they provide structural reinforcement, enable multiple degrees of freedom through differential actuation, and maintain uniform cross-sectional shape. This universal design allows a single actuator structure to achieve complex motion capabilities without proportionally increasing complexity
3Adaptability or versatility
If cables are arranged in spiral configuration to enable multiple movement directions, then range of motion is improved, but control precision decreases
Solution Approach 1:
The cable system is segmented into multiple independently controllable cable groups, each arranged in specific spiral configurations. By segmenting the control system and actuating different cable groups differentially, the actuator can achieve precise control over multiple degrees of freedom, with each cable group contributing to specific motion components while maintaining overall precision
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 actuator achieves enhanced precision and range of motion with adjustable stiffness, reducing fatigue and maintaining a constant cross-sectional area, thus improving its performance and reliability in various applications.
Implementation Method 1
a body portion between the first and second parts, wherein the body portion includes at least one chamber configured to be pressurised
Implementation Method 2
the plurality of cables are arranged such that the application of a selected force to at least one of the cables causes a desired movement of the first part relative to the second part
Data Source
AI summary
An actuator (1) is described having a first part (4), a second part (2), and a body portion (3) between the first and second parts, wherein the body portion includes at least one chamber (14) configured to be pressurised and the body portion has a longitudinal axis; and a plurality of cables (6,7,8,9), wherein each of the plurality of cables is arranged in a respective at least partial spiral with respect to the longitudinal axis of the body portion (3); and wherein the plurality of cables are arranged such that the application of a selected force to at least one of the cables causes a desired movement of the first part relative to the second part.