Electromagnetic Soft Actuators for Portable Joint Braces
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Solution Overview
Problem
Current soft robotic actuators face challenges in being portable, adaptable to different joint sizes, and matching the performance of mammalian skeletal muscles in terms of response time and output power-to-size ratio, with existing actuators exhibiting nonlinear behavior, low energy efficiency, and requiring stationary power sources.
Innovation Solution
Development of electromagnetic soft actuators that can be actuated by on-board batteries, comprising solenoid-type or voice coil motor-type designs, which are scalable, miniaturizable, and assembled into artificial sarcomeres to form exofibers for integration into active joint braces, providing linear forces similar to actin and myosin filaments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If shape memory alloy actuators are used, then high power-to-weight ratio and mechanism simplicity are achieved, but highly nonlinear behavior, low energy efficiency, and slow response speed occur
Solution Approach 1:
The patent replaces shape memory alloy actuators with electromagnetic actuators that use electromagnetic fields instead of thermal-mechanical phase transitions. This substitution eliminates the highly nonlinear behavior and slow response speed of SMA actuators while maintaining high power-to-weight ratio, and improves energy efficiency by using direct electromagnetic force generation without phase change losses.
Solution Approach 2:
The patent changes the actuation mechanism from thermal-phase change (SMA) to electromagnetic field interaction. By using electromagnetic actuators with coil windings and magnetic fields, the system achieves linear controllable force generation, fast response times, and improved energy efficiency while maintaining the high power-to-weight ratio needed for wearable applications.
2Weight of moving object
If pneumatic artificial muscles are used, then low weight and inherent compliant behavior are achieved, but stationary power sources and accessories such as air pumps and valves are required
Solution Approach 1:
The patent extracts and removes the stationary power source requirements (air pumps, valves, compressed air tanks) from the system by replacing pneumatic actuation with electromagnetic actuation. The electromagnetic actuators can be powered directly by portable batteries, eliminating the need for complex pneumatic infrastructure while maintaining light weight and compliance.
Solution Approach 2:
The patent substitutes the pneumatic system (requiring compressible air and stationary power sources) with an electromagnetic system using coil actuators and magnetic fields. This substitution maintains the lightweight and compliant characteristics of soft actuators while enabling portable operation with onboard batteries, significantly reducing device complexity.
3Speed
If dielectric elastomer actuators are used, then actuation speed and low density are achieved, but high operating voltages are required preventing operation with on-board batteries
Solution Approach 1:
The patent changes the operating voltage parameter from high voltage (dielectric elastomer actuators requiring kilovolt-level operation) to low voltage (electromagnetic actuators operating at battery-compatible voltages). The electromagnetic coil actuators achieve comparable or superior actuation speeds while being compatible with standard onboard battery systems, enabling practical wearable deployment.
4Force
If electromagnetic soft actuators are miniaturized, then force generation per unit volume increases, but manufacturing precision and assembly complexity increase
Solution Approach 1:
The patent segments the electromagnetic actuator into modular components (outer cylinder, inner shaft, coil windings, magnetic elements) that can be manufactured separately and assembled. This segmentation allows for standardized manufacturing processes and simplifies quality control, enabling miniaturization while managing manufacturing precision requirements through modular assembly rather than monolithic fabrication.
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 electromagnetic soft actuators achieve increased force generation per unit volume as they decrease in size, enabling powerful mechanical performance in active joint braces, allowing for efficient and portable assistance in rehabilitation and assistive devices.
Implementation Method 1
electromagnetic soft actuators, which may be referred to as ESAs, that can be actuated by on-board batteries and produce linear forces that cause the actuators to contract in a similar manner to actin and myosin filaments inside a sarcomere
Implementation Method 2
In some embodiments, the actuators comprise solenoid-type electromagnetic soft actuators
Implementation Method 3
In other embodiments, the actuators comprise voice coil motor-type electromagnetic soft actuators
Data Source
AI summary
In one embodiment, an electromagnetic soft actuator includes a first soft outer member comprising a soft internal electrically conductive coil, a second soft outer member comprising a soft internal electrically conductive coil, and a soft inner shaft on which the first and second soft outer members are mounted, the first and second soft outer members being linearly displaceable along a length of the soft inner shaft, the soft inner shaft comprising a permanent magnet, wherein the first and second outer members linearly move under an electromagnetic force relative to the soft inner shaft and each other when an electric current is applied to the soft internal electrically conductive coils.