Variable-Stiffness Actuator With Rapid Thermal Phase Switching
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Solution Overview
Problem
Existing variable-stiffness actuators for flexible members, such as endoscopes, lack efficient control over stiffness transitions due to slow phase changes and limited responsiveness, particularly in applications requiring rapid switching between flexible and rigid states.
Innovation Solution
A variable-stiffness actuator comprising a shape-memory member and a heating member surrounded by a heat transmitting medium, where the heating member generates heat to transition the shape-memory member between phases, and the heat transmitting medium's deformation enhances heat dissipation, allowing for rapid stiffness changes by controlling contact and non-contact states with the heating member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a shape-memory alloy wire is used to stiffen the flexible member, then the stiffness can be varied, but the phase change is slow and responsiveness is limited
Solution Approach 1:
The patent replaces the mechanical pulling action of the shape-memory alloy wire with an electrical heating system. A heating member generates heat to accelerate the phase change of the shape-memory alloy wire from martensite to austenite, enabling rapid stiffness transition without relying on slow mechanical deformation. This substitution of mechanical actuation with thermal actuation resolves the contradiction between stiffness variation capability and phase change speed.
Solution Approach 2:
The patent utilizes the phase transition properties of the shape-memory alloy wire more effectively by controlling temperature. The heating member accelerates the martensite-to-austenite phase transition, and a heat transmitting medium (such as a liquid or gas flowing through channels) rapidly removes heat to enable quick austenite-to-martensite transition. This active thermal management of phase transitions allows rapid switching between flexible and rigid states, resolving the slow responsiveness issue.
2Strength
If the shape-memory alloy wire is heated to stiffen the coil, then stiffness increases, but the heating process takes time and reduces responsiveness
Solution Approach 1:
The patent incorporates heat transmitting medium flow channels in close proximity to the shape-memory alloy wire and heating member, pre-positioned to enable immediate heat transfer when heating is initiated. The heat transmitting medium is already in place and can rapidly absorb and remove heat, reducing the time required for both heating and cooling cycles. This preliminary arrangement of thermal management components minimizes the time loss during stiffness transitions.
Solution Approach 2:
The patent employs controlled phase transitions of the shape-memory alloy wire through rapid thermal cycling. By using the heating member and heat transmitting medium to quickly transition the wire between martensite and austenite phases, the system achieves rapid stiffness changes. The phase transition mechanism allows the material to switch properties quickly in response to temperature changes, reducing the overall time required to achieve the desired stiffness state.
3Strength
If the flexible member is compressed to stiffen it, then the stiffness varies, but the control over stiffness transitions is inefficient
Solution Approach 1:
The patent replaces inefficient mechanical compression control with an electrical heating control system. The heating member can be precisely controlled through electrical signals to generate the exact amount of heat needed for rapid phase transition. This electrical control mechanism provides superior control efficiency compared to mechanical compression, allowing for precise and rapid adjustment of the flexible member's stiffness on demand.
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 faster and more responsive stiffness transitions, reducing the time required to switch between flexible and rigid states, thereby improving the actuator's responsivity and efficiency in applications like endoscopes.
Implementation Method 1
The heating member generates heat in response to supply of a current
Implementation Method 2
The heat transmitting medium is deformed to decrease an inner diameter of the heat transmitting medium to come into contact with the heating member, so as to cool the heating member
Implementation Method 3
a shape-memory member that increases in stiffness on heating
Data Source
AI summary
A variable-stiffness actuator includes a shape-memory member that increases in stiffness on heating, a heating member arranged to surround the shape-memory member along a longitudinal axis of the shape-memory member, and a heat transmitting medium arranged to surround the heating member along a longitudinal axis of the heating member. The heating member generates heat in response to supply of a current, so as to heat the shape-memory member. The heat transmitting medium is deformed to decrease an inner diameter of the heat transmitting medium to come into contact with the heating member, so as to cool the heating member. The heat transmitting medium is deformed to increase the inner diameter to come out of contact with the heating member.