Hyuk Jin Lee

This paper presents a different type of rotary actuator in contrast to conventional rotary actuators that operate by fiber wound in the form of a helix on a cylinder-shaped elastomer. Our actuator has a fiber set placed in the rθ plane of an elastomer in the form of an annulus, this elastomer expands under pneumatic pressure input to deliver rotation and torque to a rigid shaft connected to the elastomer’s inner circumference. In addition to the description and testing of our actuator’s novel mechanism, the main contribution of this paper is the design’s verification through a theoretical analysis of the rotational motion generated by the mutual influence of the elastomer and inflexible fiber elements. We also show how the design parameters are related to the wound angle of how much the fiber set inserted in the elastomer was wound in a spiral configuration. For various wound angles, computer simulation and experiments were carried out to prove the validity of our analytical model. Further experiments were conducted to measure the performance of the actuators by conducting a torque test with rotation set to zero.

Existing human lung-mimicking requirements in various radiology application fields have led to the development of many different phantoms. However, most are static apparatus designed for equipment calibration. Although there are a few dynamic phantoms that generate predefined motions, they have complicated mechanisms that hamper even simple modifications for various lung illness simulations. As a result, existing dynamic phantoms in which a target can be embedded normally generate rectilinear target motions with limited displacement. Nevertheless, volume changes in the human lungs during normal respiration are significant, and targets inside the lungs move along various random paths depending on their location, stiffness, and the properties of the surrounding tissues. In the present work, a novel phantom design is introduced and tested. The phantom mimics the human lung motion and its deformation is initiated by a diaphragm movement. The phantom provides a fairly large deformation and the capability to adjust target motion paths. The presented device has a simple mechanism that can be easily modified to generate various pulmonary diseases. To produce a large deformation by diaphragm compressive motion, polyurethane cubic blocks constitute the deformable part of the lung phantom and a tumor made with silicone is inserted in the structure. The assembled lung part is housed within an acrylic case that is filled with water. The phantom system consists of acrylic, plastic, and low-density polyurethane to minimize artifacts when it undergoes computed tomography (CT) scans. The lung part is organized with various density polyurethane blocks, making it possible to produce nonlinear motion paths of the tumor. The lung part is deformed by a silicon film that is driven by external hydraulic pressure. A finite element method simulation and two-dimensional target motion tests were performed to verify phantom performance. The functionality of the proposed phantom system was confirmed in a series of CT images.

In a physical human-robot interaction (pHRi) system, improving transparency which allows humans to move as if there is no robot is a challenging topic. In general physical human-robot interaction, usage of the multiaxial force sensor for robot control is the norm. However the signal measured from the force sensor contains not only the force applied to the robot by the human motion intention but also the influence of the natural force feedback between the robot and the human hand produced by the robot motion. Therefore, in order to improve the transparency, it is necessary to charcterize the dynamics of the human hand as well as the dynamics of the robot. In this paper, an algorithm to improve the transparency is proposed. The proposed algorithm uses only a multiaxial force sensor and compensates the natural force feedback by using the human hand impedance. And it further improves the transparency of the pHRi system which has a limitation adjusting admittance parameters. In order to verify the algorithm, a device that can measure the impedance of the human hand is introduced, and a system model analysis and experiments using the hydraulic upper limb exoskeleton are carried out.

In the physical human-robot interaction system, improving transparency performance which allows humans to move as if there is no robot is a challenging topic. In general physical human-robot interaction, the multiaxial force sensor is used to control the robot. However the signal measured from the force sensor involves not only the force applied to the robot by the human motion intention but also the influence of the natural force feedback between the robot and the human hand due to the motion of the robot. Therefore, in order to improve the transparency performance, it is necessary to consider the dynamics of the human hand as well as the dynamics of the robot. In this paper, an novel algorithm to improve transparency performance is proposed. The proposed algorithm uses only the multiaxial force sensor and compensates the natural force feedback by using the human hand impedance and further improves the transparency performance which has a limitation adjusting admittance parameters. The validity of the proposed algorithm is described through the system model analysis and the experiment using the hydraulic upper limb exoskeleton.

Many researchers have been studying a walking robot that can walk in an Unknown environment. But there is a problem. When the leg is landing, the motor or torque sensor is damaged by the amount of impact generated from the uncleaned ground. In order to solve this problem, many researchers have tried to reduce the amount of impulse by placing a passive compliance element in a motor-pack.The efforts have been made to reduce the impact by creating virtual m, c, and k elements through active compliance, impedance control or admittance control. In this paper, we designed a new concept motor-pack that enters the joint of a walking robot. The main function is to make the motor-pack into a package type to protect important components from external shocks and speed up the communication speed due to the circuit intensiveness. The motorpack consists of motor, gear, bearing, encoder and torque sensor. In addition, this paper validates the SEA module as a torque sensor.

In this paper, we propose lumped methods of flexible elements of Flexible-Link manipulator to Flexible-Joint, and compare their performance evaluation to suggest the most suitable modeling method. The first method is to obtain the Equivalent Stiffness through the static analysis of Flexible-Link. The second method is to obtain the natural frequency through the modal analysis of the Flexible-Link System and to derive the Equivalent Stiffness. The final method is to construct an FRF (Frequency Response Function) Model using the input and output signals of the Flexible-Link System and to find Equivalent stiffness through approximation using polynomial and exponential functions. Flexible-Joint and Rigid-Link manipulator is modeled based on Equivalent Stiffness obtained by the above methods, and compared with the existing Flexible-Link model.

Recently the radiation therapy device that is tracking pulmonary tumors according to respiratory cycle is developed to minimize the dose to normal tissues such as 4D-CT and IMRT (Intensity modulated radio therapy). Accordingly, 4-Dimensional Phantom mimicked the human lung should be developed in order to measurement the accuracy of new radiation therapy device. Existing 4d-phantom is limited to represent patents lung motion and used metal materials. So Metal Artifact that debase CT image resolution exist. To improve Existing 4d-phantom, this study suggest the Hydraulic Lung Phantom that the volume change is large and the deformation is dynamical using abaqus simulation.