SMP Reversible Joint for Low-Force Robotic Assembly
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Solution Overview
Problem
Current joining mechanisms for autonomous assembly, such as revolute joints, latches, welded or adhesively bonded joints, and electro-magnetic couplings, face issues with micro-dynamic stability, non-reversibility, or require constant power, making them unsuitable for reversible and stable connections in various environments and industries, especially for space solar arrays that need to withstand axial loads and integrate electrical connections.
Innovation Solution
A self-aligning reversible joint using shape memory polymer (SMP) composite structures that require less force for assembly or disassembly, utilizing a polymer-based bushing with an embedded heating element to change mechanical properties, allowing for automated assembly and disassembly with robotic tools, and enabling structural load transfer and electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional joining mechanisms (welded or adhesively bonded joints) are used, then strong structural connection is achieved, but the joints are not reversible and require constant power or complex mechanisms for assembly/disassembly
Solution Approach 1:
The patent changes the physical state of the polymer material from rigid to elastic through temperature activation. The polymer bushing transitions from a rigid state (at low temperature) that provides strong structural connection to an elastic state (at high temperature) that enables easy disassembly. This parameter change resolves the contradiction by making the joint reversible without complex mechanisms.
Solution Approach 2:
The patent uses composite materials consisting of polymer matrix combined with shape memory alloy particles or fibers. This composite structure provides both the strength of metallic materials and the reversibility of polymeric materials. The shape memory component enables controlled transformation between rigid and elastic states, achieving reversibility without increasing device complexity.
2Force
If shape memory polymer composite structures are used, then assembly force is reduced, but heating energy is required to activate the polymer
Solution Approach 1:
The patent replaces the traditional mechanical force-based assembly system with a thermally activated system. Instead of applying large mechanical forces for assembly and disassembly, the system uses controlled heating to trigger the shape memory effect. This substitution reduces the mechanical force requirement while introducing a different energy form (thermal energy) that can be more efficiently controlled and applied.
3Ease of operation
If the polymer sleeve is made elastic to allow insertion, then assembly is easier, but the joint cannot retain structural load
Solution Approach 1:
The patent makes the joint dynamically adaptable by enabling the polymer material to change its mechanical properties in response to temperature changes. The joint transitions from a rigid load-bearing state during operation to an elastic compliant state during assembly/disassembly. This dynamic behavior resolves the contradiction by providing both ease of operation and structural strength at different operational phases.
Solution Approach 2:
The patent utilizes phase transitions of the shape memory polymer material between crystalline (rigid) and amorphous (elastic) states. During assembly, heating triggers the transition to the amorphous phase, allowing easy insertion. After assembly, cooling restores the crystalline phase, providing the necessary structural load capacity. This phase transition mechanism simultaneously achieves ease of assembly and structural strength.
4Extent of automation
If traditional joints are used for autonomous assembly, then alignment is required, but misalignment tolerance is poor
Solution Approach 1:
The patent employs the flexible elastic state of the polymer bushing to accommodate misalignment during autonomous assembly. When the polymer is in its elastic state (heated), it can deform to accommodate positional and angular misalignments between components. This flexibility enables autonomous robotic assembly without requiring high-precision alignment, resolving the contradiction between automation and manufacturing 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 SMP composite reversible joint enables robust, repeatable, and efficient assembly of large structures with limited robotic output force, tolerating misalignment and facilitating multiple assembly cycles, while managing power resources effectively for in-space applications.
Implementation Method 1
The polymer-based bushing is capable of being activated by heating of the embedded heating element to reversibly change the polymer sleeve to become elastic
Implementation Method 2
The polymer sleeve comprises a shape memory polymer or a shape memory polymer composite material forming a central channel
Data Source
AI summary
A reversible joint includes male and female components. The male component has a rigid stud with a shaft region and a head region having a greater width, than the shaft region. The female component includes a polymer-based bushing including a polymer sleeve and an embedded heating element. The polymer sleeve is formed from a shape memory polymer (SMP) or an SMP composite and includes a central channel. The polymer-based bushing is capable of being activated by heating with the embedded heating element to reversibly render the polymer sleeve elastic and allow deformation of the central channel to an expanded channel width during insertion of the head region. The polymer sleeve becomes rigid after deactivation of the polymer-based bushing for retention of the male component. Load bearing assemblies formed by connecting modular structures with the reversible joint are also provided along with installation tools for the same.