Hyundo Choi

Surgical robot for single-incision laparoscopic surgery.

This paper introduces a novel surgical robot for single-incision laparoscopic surgeries. The robot system includes the cone-type remote center-of-motion (RCM) mechanism and two articulated instruments having a flexible linkage-driven elbow. The RCM mechanism, which has two revolute joints and one prismatic joint, is designed to maintain a stationary point at the apex of the cone shape. By placing the stationary point on the incision area, the mechanism allows a surgical instrument to explore the abdominal area through a small incision point. The instruments have six articulated joints, including an elbow pitch joint, which make the triangulation position for the surgery possible inside of the abdominal area. The presented elbow pitch structure is similar to the slider-crank mechanism but the connecting rod is composed of a flexible leaf spring for high payload and small looseness error. We verified the payload of the robot is more than 10 N and described preliminary experiments on peg transfer and suture motion by using the proposed surgical robot.

49.1: New Concept for Improvement of White Color Balance in Hologram Back-light Units

We have improved a white color balance using multi-grating period structure in the holographic backlight units that can be applicable to mobile LCD panel where several LEDs are placed at edge of guide plate as light sources. New H-LGP is based on the characteristics of grating and its diffraction angle can be determined by specific grating period. With this idea, hologram backlight unit can realize not only lower weight and less power consumption but also higher light utilization by eliminating couple of prismatic sheets which have been widely used in conventional unit inevitably.

Conically shaped remote center-of-motion mechanism for single-incision surgery

In this paper, we introduce a remote center-of-motion (RCM) mechanism with a conical shape for laparoscopic surgeries that involve a single incision. The mechanism, which has two revolute joints and one prismatic joint, is designed to maintain a stationary point at the apex of the conical shape. By aligning the stationary point with the incision area, the mechanism allows a surgical instrument to explore the abdominal area through a small incision point. We have previously analyzed the reachable workspace of this mechanism. Here, we arrange two RCM mechanisms on a single conical structure but separated in space to avoid mutual interference, so as to enable the entire system to manipulate two surgical instruments through a single incision point without colliding. We describe the operational principle of this system, in addition to comparisons of various RCM mechanisms and the kinematics for parameter design and motion control. Finally, we describe preliminary experiments on peg transfer and suture motion by using the proposed RCM mechanism.

Flexible sliding frame for gait enhancing mechatronic system (GEMS)

This paper presents a novel flexible sliding thigh frame for a gait enhancing mechatronic system. With its two-layered unique structure, the frame is flexible in certain locations and directions, and stiff at certain other locations, so that it can fît well to the wearers thigh and transmit the assisting torque without joint loading. The paper describes the basic mechanics of this 3D flexible frame and its stiffness characteristics. We implemented the 3D flexible frame on a gait enhancing mechatronic system and conducted experiments. The performance of the proposed mechanism is verified by simulation and experiments.This paper presents a novel flexible sliding thigh frame for a gait enhancing mechatronic system. With its two-layered unique structure, the frame is flexible in certain locations and directions, and stiff at certain other locations, so that it can fît well to the wearers thigh and transmit the assisting torque without joint loading. The paper describes the basic mechanics of this 3D flexible frame and its stiffness characteristics. We implemented the 3D flexible frame on a gait enhancing mechatronic system and conducted experiments. The performance of the proposed mechanism is verified by simulation and experiments.

A Multifunctional Ankle Exoskeleton for Mobility Enhancement of Gait-Impaired Individuals and Seniors

This letter proposes a multifunctional ankle exoskeleton to safely expand the mobility. By applying torque to the ankle in dorsiflexion and plantarflexion, the exoskeleton prevents foot drop and foot slip and helps the ankle to push off the ground. The exoskeleton includes a remote center-of-motion (RCM) mechanism, a linear actuation module, and fastening modules. The RCM mechanism, which has two degrees of freedom, is designed to be aligned with the talocrural and subtalar axes of the ankle. A key feature of the RCM mechanism is a three-dimensional combination of two four-bar linkage mechanisms that have the linear motion and rotational motion, respectively. Only the talocrural axis is actively actuated for dorsiflexion and plantarflexion of the ankle, whereas the subtalar axis is passively released to allow the unconstrained motion by the user. The active axis is driven by a linear actuation mechanism comprising a ball-screw and a brushless dc motor. The device can be separated into fastening modules and actuation module and weighs only 869 g/leg without the battery. The results of ground and treadmill tests indicate that the peak torque and average positive mechanical power delivered by the exoskeleton are approximately 20 N·m and 6.21 W, respectively.

Compact Hip-Force Sensor for a Gait-Assistance Exoskeleton System

In this paper, we propose a compact force sensor system for a hip-mounted exoskeleton for seniors with difficulties in walking due to muscle weakness. It senses and monitors the delivered force and power of the exoskeleton for motion control and taking urgent safety action. Two FSR (force-sensitive resistors) sensors are used to measure the assistance force when the user is walking. The sensor system directly measures the interaction force between the exoskeleton and the lower limb of the user instead of a previously reported force-sensing method, which estimated the hip assistance force from the current of the motor and lookup tables. Furthermore, the sensor system has the advantage of generating torque in the walking-assistant actuator based on directly measuring the hip-assistance force. Thus, the gait-assistance exoskeleton system can control the delivered power and torque to the user. The force sensing structure is designed to decouple the force caused by hip motion from other directional forces to the sensor so as to only measure that force. We confirmed that the hip-assistance force could be measured with the proposed prototype compact force sensor attached to a thigh frame through an experiment with a real system.

A self-aligning knee joint for walking assistance devices

This paper presents a novel self-aligning knee mechanism for walking assistance devices for the elderly to provide physical gait assistance. Self-aligning knee joints can assist in flexion/extension motions of the knee joint and compensate the knees transitional movements in the sagittal plane. In order to compensate the center of rotation, which moves with the flexion/extension motion of the human knee joint, a self-aligning knee joint is proposed that adds redundant degrees of freedom (i.e., 2-DoF) to the 1-DoF revolute joint. The key idea of the proposed mechanism is to decouple joint rotations and translations for use in lower-extremity wearable devices. This paper describes the mechanical design of this self-aligning knee mechanism and its implementation on a wearable robot and in preliminary experiments. The performance of the proposed mechanism is verified by simulations and experiments.This paper presents a novel self-aligning knee mechanism for walking assistance devices for the elderly to provide physical gait assistance. Self-aligning knee joints can assist in flexion/extension motions of the knee joint and compensate the knees transitional movements in the sagittal plane. In order to compensate the center of rotation, which moves with the flexion/extension motion of the human knee joint, a self-aligning knee joint is proposed that adds redundant degrees of freedom (i.e., 2-DoF) to the 1-DoF revolute joint. The key idea of the proposed mechanism is to decouple joint rotations and translations for use in lower-extremity wearable devices. This paper describes the mechanical design of this self-aligning knee mechanism and its implementation on a wearable robot and in preliminary experiments. The performance of the proposed mechanism is verified by simulations and experiments.

A Wearable Virtual Chair with the Passive Stability Assist.

This paper introduces a wearable device which performs function of swinging chair with worn status on the legs. The users with the proposed device can sit in anyplace and experience the stable swing motion. The device is designed to maintain the stability within the stable swing region while moving back and forth by external forces or user intension. The coupled motion between ankle and knee provides the users concave swing motion in chair mode, while the joints passively follows the motion of the legs in normal gait mode. The key feature of this stable motion is a CAM-drive implemented around the ankle frame and connected to the knee joint by wires. With any directional motion of the ankle joint, the knee joint rotate only one direction to lift up the body of the user. So it can move following concave equilibrium line. We verified the payload of the device is more than 70 kg in computer-aided stress simulation as well as in experiments.

Three-axis force sensor with fiber Bragg grating

Haptic feedback is critical for many surgical tasks, and it replicates force reflections at the surgical site. To meet the force reflection requirements, we propose a force sensor with an optical fiber Bragg grating (FBG) for robotic surgery. The force sensor can calculate three directional forces of an instrument from the strain of three FBGs, even under electromagnetic interference. A flexible ring-shape structure connects an instrument tip and fiber strain gages to sense three directional force. And a stopper mechanism is added in the structure to avoid plastic deformation under unexpected large force on the instrument tip. The proposed sensor is experimentally verified to have a sensing range from −12 N to 12 N, and its sensitivity was less than 0.06 N.Haptic feedback is critical for many surgical tasks, and it replicates force reflections at the surgical site. To meet the force reflection requirements, we propose a force sensor with an optical fiber Bragg grating (FBG) for robotic surgery. The force sensor can calculate three directional forces of an instrument from the strain of three FBGs, even under electromagnetic interference. A flexible ring-shape structure connects an instrument tip and fiber strain gages to sense three directional force. And a stopper mechanism is added in the structure to avoid plastic deformation under unexpected large force on the instrument tip. The proposed sensor is experimentally verified to have a sensing range from -12 N to 12 N, and its sensitivity was less than 0.06 N.

Kinematic control of redundant arms based on the virtual incision ports for robotic single-port access surgery

This paper presents a novel kinematic control scheme based on the Virtual Incision Ports (VIPs) for redundancy resolution of redundant robotic arms for single-port access (SPA) surgery. In general, manipulators have 6 DoFs except grippers to be able to reach the desired pose in 3D space. If a surgical robot for SPA surgery has only 6 DoFs, then its workspace could be restricted severely. Therefore most robots including our developed robot consist of more than 6 DoFs with an elbow to maintain triangulation. This means they have a redundancy resolution problem. One of the most popular methods for a redundancy resolution is a pseudo-inverse Jacobian method [1]. In case of robotic SPA surgery, however, this method intrinsically has a high possibility for hurting abdominal organs and muscles or conflicting with other instruments because of the unexpected elbow movements. Our control scheme can decrease the possibility of a collision with them and provide a more flexible working area for surgical tasks by reallocating the VIP. Results presented from simulation and experiment will demonstrate them.