SMA Coil Rigidity Control via Differential Pitch Segmentation
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Solution Overview
Problem
Existing rigidity variable apparatuses for insertion tools, such as endoscopes, struggle to efficiently change the rigidity of insertion portions in response to temperature changes, limiting their adaptability and functionality.
Innovation Solution
A rigidity variable apparatus comprising one or more coil units with SMA element wires wound at different pitches, where the SMA element wires start to deform to memorized shapes at a predetermined temperature, and an electrothermal heater to control the temperature and rigidity of the insertion portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single SMA wire is used to change rigidity, then the structure is simple, but the rigidity change speed is slow
Solution Approach 1:
The single SMA wire is segmented into multiple parallel SMA wires (first SMA element wire and second SMA element wire). Each wire is independently wound at different pitches and can deform independently when heated, allowing faster and more controlled rigidity changes while maintaining structural simplicity.
2Manufacturing precision
If multiple SMA wires with different pitches are used, then the rigidity control precision is improved, but the manufacturing complexity increases
Solution Approach 1:
The SMA wires are pre-formed with specific spiral shapes at different pitches before assembly. The first SMA element wire is formed with a first spiral shape at a first pitch, and the second SMA element wire is formed with a second spiral shape at a second pitch. These pre-formed wires are then assembled in parallel, simplifying the manufacturing process while achieving precise rigidity control through the pitch differences.
3Stability of the object's composition
If the insertion portion maintains high rigidity, then the operational stability is improved, but the adaptability to curved paths decreases
Solution Approach 1:
The insertion portion's rigidity is made dynamic through the dual-SMA-wire mechanism. When heated, both SMA wires deform simultaneously but at different rates due to their different pitches, enabling the insertion portion to transition between rigid (for stable operation) and flexible (for curved path navigation) states, thus achieving both operational stability and adaptability.
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 changes the rigidity of the insertion portion by switching the heating state, allowing for both high rigidity and flexibility adjustments in a short time, enhancing the operational range and efficiency of insertion tools.
Implementation Method 1
an electrothermal heater configured to heat the coil
Implementation Method 2
the first SMA element wire memorizing a spiral shape with a second pitch narrower than the first pitch and being extended from the spiral shape with the second pitch to a spiral shape with the first pitch, the second SMA element wire memorizing a spiral shape with a third pitch narrower than the first pitch
Data Source
AI summary
A rigidity variable apparatus includes: one or a plurality of coil units including a spiral-shaped coil portion in which a plurality of SMA element wires made of a shape-memory alloy are wound around an axis at a first pitch in a state where the SMA element wires are overlapped with each other in a predetermined axis direction, each of the SMA element wires memorizing a spiral shape with a pitch narrower than the first pitch, one of the plurality of SMA element wires starting to deform to the memorized spiral shape with a predetermined pitch when at a predetermined temperature or higher, another of the plurality of SMA element wires starting to deform to the spiral shape with a different pitch; and an electrothermal heater configured to heat the coil portion.