Papers by Author: Seung Bok Choi

Abstract: In modern society, a plenty of car accident is occurred and a lot of people get injury every day. For this reason, the importance of car safety has been increased and car safety has been extensively studied. Especially in many countries, the law about using baby safety seat is legislated to protect babies and children from accident. Thus, recently numerous products for baby safety have been developed. In this paper, a new type baby car seat is proposed to protect babies and children from frontal accident. In order to achieve this goal, design requirements of spring and MR(Magnetorheological) Damper which are main elements for a new type baby car seat are investigated.

Abstract: It is very prevalent in medical industry to adopt robotic technology such as robotic minimally invasive surgery (RMIS). This causes the surgeon not to sense viscosity and stiffness of the tissue or organ. In order to generate the tactile recognition of human organ, this work proposes a novel tactile device using magnetorheological (MR) fluid. The MR fluid is fully inserted into diaphragm and several pins. Due to controllability of rheological properties by the intensity of the magnetic flux density, the operator can feel different force from the proposed tactile device. In order to evaluate the performance of tactile device, two method is proposed. One is to measure the repulsive force with applying several control inputs. The other method is to check the performance of tactile sensation using psychophysical experiments. From these results, the usability of the tactile device is proved.

Abstract: This article presents performance results of a novel jetting dispenser system actuated dual piezostack actuators. The proposed piezo jetting dispenser system consists of a couple of piezostack actuators, lever mechanism, and needle part. The proposed dispenser can provide a very small dispensing dot size of high viscous adhesive, 10,000cp at 100°C, at a high dispensing flow rate in semi-conductor packaging processes. After describing the mechanism and operating principle of the proposed dispenser, a mathematical model of the system is obtained by considering behaviors of the piezostack, the return spring, the dispensing needle, and the adhesive fluid dynamics. For the computer simulation, the specific geometric dimensions of the proposed jetting dispenser are chosen in order to achieve operation requirements: needle motion amplitude: up to 0.15 mm; operating frequency: up to 500 Hz. With the high viscosity conditions, the dispensed amount of the adhesive and the maximum displacement of the piezo and the needle at 500Hz are evaluated in time domain.

Abstract: This paper proposes a novel type of tactile device using magnetorheological (MR) fluid which can be applied in minimally invasive surgery (MIS) robotic system. The remarkable feature of rheological properties of MR fluid by the intensity of the magnetic field makes this potential candidate of the tactile device. As the first step, in order to determine proper input magnetic field the repulsive forces of the real body parts such as hand and neck are measured. Secondly, an appropriate size of the tactile device is designed and manufactured base on magnetic analysis. The final step of this study is to measure the repulsive forces of dividing 5 areas in the tactile device.

Abstract: In this research, a slave robot is proposed and integrated with an electrorheological (ER) haptic master for minimally invasive surgery (MIS). A novel mechanism of the slave robot with a gimbal joint is developed to realize 4-DOF motions. The proposed slave robot consists of two arms, gimbal joint and fixed bar. The haptic master can generate a repulsive force as well as position motion for the slave robot. The manufactured slave robot and haptic master are remotely connected with each other via TCP/IP communications. Both repulsive force and position tracking control are evaluated in experiment.

Abstract: Electropolishing, the anodic dissolution process without contact with tools, is a surface Treatment method to make a surface planarization using an electrochemical reaction with low current density. Stainless steel can be put various applications which require purity and high precision surface of products. The aim of this study is to investigate the characteristic of electropolishing effect for stainless steel workpieces. In order to analyze the characteristics of electropolishing effect, surface roughness and micro-burr size were measured in terms of machining conditions such as current density, machining time and electrode gap. The tendencies about improvement of surface roughness by electropolishing for stainless steel workpieces were determined.

Abstract: This paper presents a new design of an electro-rheological (ER) fluid-based haptic master device that is used for a minimally invasive surgery (MIS). This device consists of a bi-directional ER clutch/brake and an ER brake from which a repulsive force is realized. First, the modeling of these clutches/brakes is conducted. In addition, to transmit a complex rotation from the handle of the device to three independently rotary movements, a gimbal mechanism is adopted. At last, in order to evaluate the repulsive forces generated from the device, an experimental test is undertaken.

Abstract: This paper proposes a new brake featuring magneto-rheological (MR) fluid. The outstanding feature of the proposed MR brake is the possibility of compensating for the passive friction completely. It consists of two coils, one quasi-stator and two rotors. These rotors are in relatively reverse rotation mode. After a configuration of this brake is proposed, an optimization procedure based on integrated finite element analysis (FEA) and Particle Swarm Optimization (PSO) algorithm is developed to obtain its geometric dimensions. Then, the simulated performance of the optimized brake is shown with remarkable discussions.

Abstract: This study presents the configuration and modeling of haptic mater device for minimally invasive surgery (MIS) using ER fluid. The haptic device has 3-DOF rotational motion which is realized by the ER spherical joint. The ER spherical joint is designed based on Bingham model. The haptic master device that consists of spherical joint as an inner electrode and sphere housing as an outer electrode is manufactured. Generated torque of the manufactured haptic master device is then experimentally evaluated with respect to applied electric field.

Abstract: This paper proposes an active mount of naval ships in order to reduce unwanted vibrations. The active mount consists of rubber element and piezostack actuator. To avoid being broken piezostack actuator, the inertial actuator which the piezostack actuator is connected to the inertial mass and rubber element is devised. After describing the configuration of the mount, the active mount system supported by four mounts is then constructed. To attenuate the transmitted vibrations, the feedforward control is designed and experimentally implemented to the system. Vibration control performances such as vertical accelerations are evaluated at each mount and presented in frequency domain.