Wearable Robot Using Shape Memory Alloy Actuators for Wrist Assistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current rehabilitation robots for upper limb mobility are not suitable for wearable applications due to their sturdy structure, weight, and large volume, limiting their use to fixed locations and restricting their ability to assist wrist and elbow movements effectively.
Innovation Solution
A wearable robot utilizing flexible actuators that mimic human muscle movements through contraction and relaxation, powered by heat and refrigerant circulation, with a control unit managing the actuators to provide assistive movements for the wrist, elbow, and other upper limb functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solid structure with motors is used for rehabilitation robots, then force transmission and structural stability are improved, but weight and volume increase, making the robot unsuitable for wearable applications
Solution Approach 1:
The patent replaces traditional rigid metal structures with flexible materials including fabric layers, elastic bodies, and thin film components. The wearable robot comprises multiple fabric layers (first fabric layer, second fabric layer) connected by elastic bodies, eliminating the need for heavy metal linkages while maintaining structural integrity and force transmission capability through the flexible components.
2Speed
If hydraulic pressure actuators are used for flexible robots, then contraction/relaxation response characteristics are improved, but large-scale pneumatic equipment is required, preventing downsizing
Solution Approach 1:
The patent extracts and removes the heavy pneumatic equipment from the wearable robot system entirely. Instead of using hydraulic or pneumatic actuators requiring large-scale equipment, the invention employs shape memory alloy wires that can be directly integrated into the fabric structure, achieving rapid contraction and relaxation responses without external pneumatic systems.
Solution Approach 2:
The patent replaces the mechanical pneumatic-hydraulic actuation system with a thermal-field-based actuation system using shape memory alloys. The control unit heats the shape memory alloy wires to induce contraction, and natural cooling or water circulation enables relaxation, substituting complex mechanical actuation with a simpler thermal field approach.
3Shape
If dielectric and ionic polymer actuators are used, then large-deformative relaxation motion is achieved, but output force is limited and contraction motion is difficult to implement
Solution Approach 1:
The patent employs composite material structures combining shape memory alloy wires with fabric layers and elastic bodies. The shape memory alloy provides high output force through thermal actuation, while the fabric and elastic components enable large deformations and flexible motion. This composite approach overcomes the limitations of single-material actuators by distributing functions across multiple materials.
4Weight of moving object
If heat-operated flexible actuators are used, then size and thickness are reduced with large force and displacement capability, but response speed becomes slow and control becomes difficult
Solution Approach 1:
The patent implements preliminary cooling action by circulating water through cooling channels in the fabric structure before and during actuator operation. This pre-cooling and continuous cooling during operation maintains the shape memory alloy wires in a state ready for rapid heating and contraction, significantly improving response speed while keeping the actuator size small and integrated into the wearable fabric.
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 wearable robot effectively imitates human muscle movements, providing assistive support for daily activities and rehabilitation by offering a lightweight, flexible, and portable solution for patients with limited mobility, enhancing wrist and upper limb mobility with high displacement and force capabilities.
Implementation Method 1
a driving part which is contractively deformed by a current or transfer heat applied from the control unit or is relaxed when the heat is lost
Implementation Method 2
The flexible actuator includes a driving part which is contractively deformed by a current or transfer heat applied from the control unit
Implementation Method 3
a refrigerant circulating part which is implemented to surround the driving part and circulates a refrigerant so that the contractively deformed driving part is cooled
Implementation Method 4
a refrigerant circulating part which is implemented to surround the driving part and circulates a refrigerant so that the contractively deformed driving part is cooled
Data Source
AI summary
Disclosed is a wearable robot for assisting a wrist, including: a plurality of flexible actuators; and a control unit configured to control any one of the plurality of flexible actuators to be contracted or relaxed according to a wrist movement of a wearer. Each of the plurality of flexible actuators includes: a driving part which is contractively deformed by a current or transfer heat applied from the control unit or is relaxed when the heat is lost, and a refrigerant circulating part which is implemented to surround the driving part and circulates a refrigerant so that the contractively deformed driving part is cooled under control of the control unit.