H.S. Choi

2-DOF kinematic XY stage design based on flexure element

This paper presents a planar motion stage design based on flexure element that allow large ranges of motion along x and y direction without causing over-constraint or significant error motions. From comparing the conventional XY stage with the flexure-based compliant XY stage, the main bottleneck for the flexure-based compliant XY stage is parasitic motion because of inherent characteristics of flexure element. Based on the constraint analysis, new mechanism is designed to eliminate the parasitic error, and piezoelectric actuator is used to improve the positioning resolution.

Control and design of a 3 DOF fish robot ‘ICHTUS’

Recently, there is a rising interest on studying fish-like underwater robots because of real fishs great maneuverability and high energy efficiency. However, the researches about the fish-like underwater robots have not been done so much and there are still diverse problems in respect of using of the fish robot in the real environment such as in the river. For example, the fish robot has a short operating time and cannot move narrow passage such as swimming between aquatic plants. Therefore, this paper mainly describes a control method according to propulsion algorithm for improving energy efficiency and obstacle avoidance. The fish robot ‘Ichthus’ has a 3-DOF serial link-mechanism and is developed in KITECH. Also, we propose a dynamic equation of the fish robot to use the underwater environment. In the control portion, response characteristics of the fish robot were analyzed according to the input parameters of tail fins amplitude and oscillation frequency. In consequence of this result, Control parameters of robot fish were found. These parameters are useful to increase energy efficiency and it can be used when the fish robot moves in the real environment.

Implementation of the readout system in the UFFO Slewing Mirror Telescope

China Center of Advanced Science and Technology (CCAST);Chinese Academy of Sciences (CAS);Institute of High Energy Physics (IHEP);National Natural Science Foundation of China (NSFC)

Readout of the UFFO Slewing Mirror Telescope to detect UV/optical photons from Gamma-Ray Bursts

The Slewing Mirror Telescope (SMT) was proposed for rapid response to prompt UV/optical photons from Gamma-Ray Bursts (GRBs). The SMT is a key component of the Ultra-Fast Flash Observatory (UFFO)-pathfinder, which will be launched aboard the Lomonosov spacecraft at the end of 2013. The SMT utilizes a motorized mirror that slews rapidly forward to its target within a second after triggering by an X-ray coded mask camera, which makes unnecessary a reorientation of the entire spacecraft. Subsequent measurement of the UV/optical is accomplished by a 10 cm aperture Ritchey-Chretien telescope and the focal plane detector of Intensified Charge-Coupled Device (ICCD). The ICCD is sensitive to UV/optical photons of 200–650 nm in wavelength by using a UV-enhanced S20 photocathode and amplifies photoelectrons at a gain of 104–106 in double Micro-Channel Plates. These photons are read out by a Kodak KAI-0340 interline CCD sensor and a CCD Signal Processor with 10-bit Analog-to-Digital Converter. Various control clocks for CCD readout are implemented using a Field Programmable Gate Array (FPGA). The SMT readout is in charge of not only data acquisition, storage and transfer, but also control of the slewing mirror, the ICCD high voltage adjustments, power distribution, and system monitoring by interfacing to the UFFO-pathfinder. These functions are realized in the FPGA to minimize power consumption and to enhance processing time. The SMT readout electronics are designed and built to meet the spacecrafts constraints of power consumption, mass, and volume. The entire system is integrated with the SMT optics, as is the UFFO-pathfinder. The system has been tested and satisfies the conditions of launch and those of operation in space: those associated with shock and vibration and those associated with thermal and vacuum, respectively. In this paper, we present the SMT readout electronics: the design, construction, and performance, as well as the results of space environment test.

Development of a micro manipulator using a microgripper and PZT actuator for microscopic operations

Micro manipulation system for microscopic applications using PZT actuator and microgripper is developed. This system is designed for handling a bio cell under optical microscope and consists of an actuator using PZT, a microgripper, and a man-machine interface. With these essential parts implemented prototype micro manipulation system, a practical manipulation experiments including grasping and moving a specific bio cell is conducted to evaluate the system performance and effectiveness.

Data Acquisition System for the UFFO Pathfinder

The Ultra-Fast Flash Observatory (UFFO) Pathfinder is a payload on the Russian Lomonosov satellite, scheduled to be launched in November 2011. The Observatory is designed to detect early UV/Optical photons from Gamma-Ray Bursts (GRBs). There are two telescopes and one main data acquisition system: the UFFO Burst Alert & Trigger Telescope (UBAT), the Slewing Mirror Telescope (SMT), and the UFFO Data Acquisition (UDAQ) system. The UDAQ controls and manages the operation and communication of each telescope, and is also in charge of the in- terface with the satellite. It will write the data taken by each telescope to the NOR flash memory and sends them to the satellite via the Bus-Interface system (BI). It also receives data from the satellite including the coordinates and time of an external trigger from another payload, and distributes them to two telescopes. These functions are imple- mented in field programmable gates arrays (FPGA) for low power consumption and fast processing without a micro- processor. The UDAQ architecture, control of the system, and data flow will be presented.

Soft biomimetic leg design and fabrication process of cockroach-inspired robot

Successful locomotion of bio-mimetic robots over uneven terrains with obstacles and cliffs is still a challenge. In this paper we try to find another way to depict a soft biomimetic leg of cockroach by using Silicon & Urethane material and embedded actuator. Comparing others research, our proposed structure is simple and has one actuator for each leg, which is easy to control the 6 legs locomotion, however the structure design consider the real cockroach size and joints of the cockroach leg sufficiently. On the other side, based on the Voice Coil Motor (VCM) design, leg integrate the motor, soft structure and flexure hinge by using Structure Casting Manufacturing (SCM) method to fabricate.

Space teleoperation scheme for Korean Lunar Rover

This paper provides the architecture of the teleoperation system of the Korean Lunar Rover under development. First, we conducted a simulation experiment for the possibility of real-time teleoperation of the lunar exploration rover because the communication time-delay between the earth and the moon is expected to be 6 seconds. Based on the experimental results, we propose suitable teleoperation system architecture for Korean Lunar Rover.

Generation of optimal swimming algorithm using reference velocity for robotic fish "ichthus V3"

Reference velocity is a performance index required to derive the efficient movement of each joint from pseudo-inverse which is a joint movement optimized based on the speed of front joint in a multi-body with hyper redundancy and has been applied in finding the optimal solution of each joint at kinematic level when creating the swimming motion of a bio-inspired robotic fish. The motion of each joint in creating the movement of a bio-inspired robotic fish has been programmed based on sinusoidal motion inspired by the swimming pattern of an actual fish and successful in creating a flexible movement up to this point, but it turns out that the actual movement of a bio-inspired robotic fish in the water is different from what is expected when the analyzed optimal solution of joint motion in a bio-inspired robotic fishs movement is applied since the thickness, length and width of the target fish affects the result of analysis. When the solution of joint motion based on reference velocity is applied, on the other hand, more flexible swimming movement than those in other existing researches has been observed even though there are still some differences between the movements of an actual fish and a bio-inspired robotic fish such as forward-speed, turning radius and so on.

Opto-mechanical performances of slewing mirror space telescope for GRB detection

The UFFO (Ultra-Fast Flash Observatory) Pathfinder is a space instrument onboard the Lomonosov satellite scheduled to be launched in November 2011. It is designed for extremely fast observation of optical counterparts of Gamma Ray Bursts (GRBs). It consists of two subsystems; i) UBAT (UFFO Burst Alert & Trigger Telescope) and ii) SMT (Slewing Mirror Telescope). This study is concerned with SMT opto-mechanical subsystem design and optical performance test. SMT is a F/11.4 Ritchey-Chretien type telescope benefited from compact design with a short optical tube assembly for the given focal length of 1,140 mm. SMT is designed to operate over a wide range of wavelength between 200 nm and 650 nm and has 17 arcmin FOV (Field of View), providing 4 arcsec in detector pixel resolution. The main detector is 256 x 256 ICCD (Intensified Charge-Coupled Device) of 22.2μm in pixel size. This SMT design offers good imaging performance including 0.77 in MTF at Nyquist frequency of 22.52 /mm and 2.7 μm in RMS spot radius. The primary (M1) and secondary (M2) mirror are hyperbolic surfaces and were manufactured within 1/50 waves (He-Ne, 632.8nm) in RMS surface error. After completion of the initial integration, the SMT opto-mechanical subsystem reached to the system wavefront error better than 1/10 waves in room temperature. We then tested the opto-mechanical performances under thermal cycling and vibration. In this study, we report the SMT subsystem design solution and integration together with thermal and vibration test results.