Fluidic Artificial Muscle Actuator End Fitting Swaging
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Solution Overview
Problem
Fluidic artificial muscle actuators face challenges in achieving a balance between generating maximum force and displacement while maintaining a robust and reliable connection, particularly in applications requiring both force and displacement transfer to external systems.
Innovation Solution
A new end fitting design and manufacturing technique involving a conical steel die to swage a thin-walled tube around the end fittings, braided sleeve, and bladder, combined with adhesive application to enhance mechanical strength and ensure a pressure-tight seal, resulting in a simple, robust, and cost-effective actuator with high tensile strength and long fatigue life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional connection methods are used for end fittings, then the actuator can transfer force and displacement to external systems, but the connection lacks robustness and reliability
Solution Approach 1:
The patent combines multiple connection methods into a single integrated end fitting structure. The swaged tube mechanically interlocks with the braided sleeve while adhesive bonds the bladder to the end fitting, creating a unified connection system that achieves both robustness and reliability simultaneously rather than using separate connection methods.
Solution Approach 2:
The end fitting assembly uses composite construction combining metallic swaged tube, polymeric adhesive, and braided sleeve materials. This multi-material approach allows each material to contribute its superior properties - the metal provides structural strength, the adhesive provides bonding reliability, and the braided sleeve provides flexibility and force transfer.
2Strength
If complex manufacturing processes are used to achieve robust connections, then connection strength improves, but manufacturing cost and complexity increase
Solution Approach 1:
The end fittings are pre-assembled with the braided sleeve and bladder before final integration into the actuator system. The swaged tube is pre-formed and positioned, and adhesive is pre-applied to optimal locations, allowing the final assembly to be completed in a single swaging operation rather than requiring multiple complex manufacturing steps.
Solution Approach 2:
The swaging process itself serves multiple functions simultaneously - it mechanically interlocks the tube with the braided sleeve, compresses the adhesive to create bonding surfaces, and seals the end fitting assembly. This self-service approach achieves robust connection strength through a single operation rather than requiring multiple separate manufacturing processes.
3Force
If maximum force generation is prioritized, then blocked force increases, but displacement capability decreases
Solution Approach 1:
The end fitting design incorporates dynamic characteristics that allow the connection to adapt between force transmission and displacement accommodation. The swaged tube's mechanical interlock with the braided sleeve provides rigid force transmission when needed, while the compliant adhesive layer and flexible connection geometry allow for displacement when the actuator contracts or expands.
Solution Approach 2:
The connection geometry and material properties are optimized to change effective stiffness based on operating conditions. Under high load conditions, the rigid swaged tube structure dominates providing high blocked force. Under displacement conditions, the compliant adhesive and flexible braided sleeve connection allow greater movement while maintaining structural integrity.
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 solution enables the production of fluidic artificial muscle actuators that effectively balance force and displacement, suitable for various applications including factory automation, prosthetics, and aerospace, with improved reliability and reduced manufacturing costs without compromising performance.
Implementation Method 1
The plastic deformation that occurs during the swaging process is axisymmetric and serves to clamp the sleeve and tube to the end fitting
Implementation Method 2
adhesive may be spread onto the outer surfaces of the end fittings themselves and/or to the section of the sleeve and/or bladder that comes into contact with the end fittings
Implementation Method 3
The inner elastic, bladder is pressurized with a fluid such as air or oil, causing an inflation and expansion of the bladder
Data Source
AI summary
A fluidic artificial muscle actuator consisting of an inner elastic bladder surrounded by a braided filament sleeve and sealed off on either end with end fittings. Pressurization of the actuator produces force and/or motion through radial movement of the bladder and sleeve which forces the sleeve to move axially. Both contractile and extensile motions are possible depending on the geometry of the braided sleeve. The fluidic artificial muscle actuator is manufactured using a swaging process which plastically deforms swage tubes around the end fittings, braided sleeve, and pressure bladder, creating a strong mechanical clamping action that may be augmented with adhesive bonding of the components. The swaging system includes the swaging die and associated components which are used to plastically deform the swage tube during assembly of the actuator.