soft actuators & sensors

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soft actuators & sensors

soft actuators & sensors

1. Soft Sensors


● Force Myography (FMG) system utilizing force sensor using weaved optical fiber
 
 We have developed a novel sleeve-type Force Myography (FMG) system featuring a thin, flexible force sensor utilizing woven optical fibers for motion recognition. This compact sensor demonstrates high sensitivity and a wide force sensing range (>10N). It achieves accuracy in force estimation exceeding 99.17% and boasts a fast response time, making it ideal for real-time applications. The sensor's design enables comfortable embedding into clothing, highlighting its potential for prosthetics and virtual reality interactions. Our proof of concept involves estimating elbow flexion angles, achieving a correlation coefficient of 94.27%, as demonstrated in the first video. Additionally, we successfully recognize wrist motion using multiple sensors, as depicted in the second video. The proposed FMG sensor presents a promising solution for precise and intuitive human-robot interaction.




● Multi-DOF force sensor incorporated into soft robotic gripper
 
 We have developed a multi-DOF force sensor that can be incorporated into soft grippers to detect the grasping force, and the slipping state of the objects. The proposed sensor employs lightweight and compact optical fibers, thereby allowing for cost-effective fabrication, and a robust sensing system that is immune to electromagnetic fields. By innervating the soft gripper with optical fibers, a durable system is achieved with the fibers functioning as a strengthening layer, thereby eliminating the need for embedding an external stiffening structure for efficient bending actuation. Because of its excellent integration capability, the sensor can detect force without disturbing the grasping performance of the soft gripper and enables robust and stable sensing.


 



 
● Real-time shape estimation using coiled fiber sensors
 
 We developed a real-time method to estimate the shape of a hyper-redundant manipulator having embedded coiled fiber sensors. The fiber sensors are highly flexible, compact, and inexpensive as well as they can functionally measure both compressive and tensile strain of hyper-redundant manipulator. Also, the numbers of sensor and the placements were determined by analysis of the kinematics and moment distribution of the manipulator. Consequently, we can estimate the shpae of the manipulator under both free-loading and loading conditions.
 



● Flexible Strain Sensor
 
 Our group has developed a highly stretchable optical strain sensor for wearable applications using a polymeric optical fiber embedded in silicone elastomer. The developed sensor detects uniaxial strain via output light intensity, allowing reliable detection of tensile strain from 0% to 120% with fast, reversible, and durable performance thanks to its novel design.
 





● Polymer-Waveguide-Based flexible tactile sensor
 
 Our group has reported A polymer-waveguide-based transparent and flexible force sensor array, which satisfies the principal requirements for a tactile sensor working on curvilinear surfaces, such as thinfilm architecture (thickness < 150 μm), localized force sensing (ca. 0–3 N), multiple-point re cognition (27 points), bending robustness (10.8% degradation at R = 1.5 mm), and fast response (bandwidth > 16 Hz).
 




● Highly stretchable-compressible coiled polymer sensor for soft continuum manipulator
 
 Our group has developed a coiled polymer optical strain sensor achieving high stretchability and compressibility with low hysteresis error. The sensor's bending curvature changes under strain, leading to a change in light intensity. The compact structure allows placement of three sensors in a soft continuum manipulator, providing a 3 DoF configuration including bending and torsion motions. An artificial neural network provides a real-time, accurate representation of the manipulator's configuration.
 

 
2. Soft Actuators
 
 ● Fast operational Shape Memory Alloy (SMA) artificial muscle
 
 Our lab have developed various types of artificial muscle based on soft actuators. One of our achievement includes development of powerful and fast shape memory alloy(SMA)-based artificial muscle, which can generate high force (>3 kgf) at high operating frequency (2 Hz).
 



● High-output force electrohydraulic actuator
 
 We developed a novel soft actuator with high force and large displacement with relatively low operating voltage based on the induced interfacial charge phenomenon of a functional material called polyvinyl chloride (PVC) gel combined with electrohydraulic working principle. This actuator exerts a force as high as 16 times of its body weight.
 

 




● Dielectric elastomer actuator-based artificial muscle
 
 Research interests in our group include developing an electro-active polymer-based soft actuator. Our group has developed spring-rolled dielectric elastomer actuator (DEA) based artificial muscle and proposed and verified a mathematical model addressing both hyper-elastic and time-dependent behavior of the developed actuator.

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