MEDICAL APPLICATIONS
1. Soft Rehabilitation Robot
● Soft Wearable Robot with Passive Gravity Compensation
We developed a novel soft wearable robot that can perfectly compensate the gravitational torque of lower arm using wearable mechanism and SMA-based soft artificial muscle which the restoring force is enhanced. This robot can generate assistive torque up to 2 Nm passively, and generate up to 3.5 Nm actively.
● Soft wearable robot for assisting with wrist movements
Applying soft robotic technologies for wearable robots is a great approach for a compact, lightweight, user-friendly and portable exoskeleton since the soft actuators and sensors are lightweight, compact and have high DOFs. We have interests in the use of SMA actuator for a soft wearable robot since it produces high force and displacement with thin, flexible and lightweight features. The SMA-based wearable robot, named Soft Wrist Assist (SWA), assists 2 DOFs wrist motions, only weighting 151g of the wearable part.
● Soft wearable robot for assisting with elbow & forearm movements
We developed a soft wearable robot that helps people with impaired mobility perform daily activities by assisting with elbow flexion and forearm supination/pronation. We used SMA-based artificial muscles to generate high torque and improve performance. The robot can produce more than 3 Nm of torque in the direction of elbow flexion, which is helpful for lifting objects. It can also increase the range of motion for forearm supination/pronation by an average of 15.7°. We tested the robot on patients with stroke and spinal cord injuries to evaluate its effectiveness. The results show that the robot improves both range of motion and the amount of force generated. Overall, the soft wearable robot has the potential to improve the quality of life for people with mobility impairments.
● Soft wearable robot for assisting with shoulder movements
We developed a new mechanism to assist with shoulder
abduction using a four-bar linkage-based support hinge mechanism and an
artificial muscle based on shape memory alloy (SMA). The SMA coils are used to
make the system lightweight while still actively and passively supporting the
wearer's movement. The artificial muscle can generate up to 273 N of force with
energy input and 180 N without energy input while only weighing 0.04 kg. To
account for the rotation axis shifts of the arm during shoulder abduction, we
modeled the trajectory of the arm along the shoulder abduction using the
scapulohumeral rhythm. The designed robot can generate up to 10.1 Nm of torque
with energy input and 6.3 Nm without energy input. We tested the mechanism's assistive effect by
measuring electromyography while performing shoulder abduction with and without
the support of the mechanism. The results show that the proposed mechanism
reduces muscle load and fatigue during shoulder abduction exercises. In
summary, our new mechanism is a lightweight and effective way to assist with
shoulder abduction, and it has the potential to improve the quality of life for
people with shoulder impairments.
2. Soft Robots in Surgical Robot
● Soft sensors in surgical robot manipulator
To achieve minimally invasive surgery (MIS) to prevent
damage to the patients, flexible & soft surgical
instruments were developed. Our group developed a joint angle sensing
method that uses coiled soft sensors to estimate the shape of a hyperredundant
manipulator, which is commonly used in flexible endoscopic surgical robots.
These sensors are small in size and highly stretchable, making them easy to integrate
between individual joints while maintaining a center hollow and sensing both
compression and extension. We experimentally selected the pre-stretch length of
the sensors to maximize sensitivity, and we validated the design by
implementing two sensors on a two-degree of freedom single joint manipulator.
The sensors at all joints could sense joint angles independently and
simultaneously with a root-mean-square error (RMSE) less than 2.53°. Based on
our proposed method, we achieved a two-degree of freedom configuration of the
hyperredundant manipulator that can be used in real applications. The
manipulator follows a constant curvature model in real-time with an RMSE of
2.30° and 2.63° for pitch and yaw joint angles, respectively.
● Soft endoscopic surgical robots
Although various endoscopic surgery robots
developed in previous studies are versatile and have high lesion accessibility,
they have limitations in terms of reaching the target lesion through the curved
path in the large intestine and providing a stable tasking environment for the operator.
An endoscopic surgery robot was developed for performing surgery in the large
intestine. The robot was easily inserted into the target lesion in the curved colon
through the mounted soft actuator and demonstrated high structural stiffness through
the insertion of the sigmoidal auxiliary tendons. The robot was able to access the
target lesion in the curved colon through teleoperation alone. Further, it was
confirmed that the high structural stiffness overtube improved the overall task
performance in the user test.
