Moon Gu Lee

Locomotive mechanism design and fabrication of biomimetic micro robot using shape memory alloy

Recently, micro robots have been applied in various industrial areas. Some of them are requested to be able to move in small space or rough environment that people cannot reach. It is necessary to have a capability to move at even overturned and adapt simple mechanism to fabricate it easily with small size. In this paper, a novel bio-mimetic micro robot with simple mechanism using shape memory alloy (SMA) is introduced to generate earthworm-like locomotive motion. There have been many kinds of mobile micro robot using the SMA. However, these actuators generally require electric cable for power supply, which might have an adverse effect on the mobility of the micro robot The proposed micro robot system is composed of an actuator with SMA spring and silicone bellows, wireless control system, wireless power supply (battery) and body frames. The robot is also analyzed to customize required specifications. After the design and experiment, we find out that the micro robot can move a wireless free motion and be fabricated easily. Like an earthworm, the robot can travel on uneven, slippery and flexible environment.

Design and fabrication of a bio-material property measurement system

Recently, diseases in gastro-intestinal tract have drastically increased. As a result, endoscopic technologies are being developed to diagnose and treat these diseases. Biomaterial property is essential information to develop endoscopic devices especially capsule type endoscope. For the past decades, experiments to obtain material property of gastro-intestinal tract are performed on in-vitro state. Therefore, material properties of digestive organs are not in-vivo test result but in-vitro result. In this research, we design, develop, and fabricate a bio-material property measurement (BMPM) system. The measuring system consists of a probing device, tendon device and suction part. The probe measures the force transmitted from the biomaterial as the sensing module protrudes based on the tendon controls, while the suction device seizes the organ. By using the system, we can measure the local deformation force and the piercing force. The measured deformation and piercing force data can be used for the locomotive and clamping mechanism design of the capsule type endoscope. In order to evaluate the validity of the BMPM, we perform the operation in an esophagus, stomach and colon of a pig. In conclusion, we could measure each organs material properties under in-vitro state without dissection of digestive organs. Some in-vivo test results are expected to design endoscopic devices using the proposed BMPM system.

Development of Novel Platform to Predict the Mechanical Damage of a Miniature Mobile Haptic Actuator

Impact characterization of a linear resonant actuator (LRA) is studied experimentally by a newly-developed drop tester, which can control various experimental uncertainties, such as rotational moment, air resistance, secondary impact, and so on. The feasibility of this test apparatus was verified by a comparison with a free fall test. By utilizing a high-speed camera and measuring the vibrational displacement of the spring material, the impact behavior was captured and the damping ratio of the system was defined. Based on the above processes, a finite element model was established and the experimental and analytical results were successfully correlated. Finally, the damage of the system from impact loading can be expected by the developed model and, as a result, this research can improve the impact reliability of the LRA.

Effect of Surface Treatment on Fatigue Strength of SCM440H

Increased efficiency and improved performance associated with light-weight materials were investigated in this study. Numerous studies have investigated surface treatments to improve the fatigue strength of metals. Laser heat treatment is a promising method because the power and spot size can be easily controlled, allowing a small heat affected zone (HAZ). However, changes in the material properties can result; in particular, the material can become more brittle. In this study, a combination of laser heat treatment and vibration peening was proposed to increase fatigue strength without changing the material characteristics. SCM440H was investigated experimentally, and specimens were tested using a giga-cycle ultrasonic fatigue tester. The results show that the combination of these two processes significantly increased the fatigue strength and, furthermore, different fracture types were observed after a small and large number of cycles.

Design and optimisation of micro forging system to reduce parasitic motion

As the demand for high reliability in mechanical parts increases, micro forging technology is drawing attention. In forging by a vibration tip, the straightness of the processing direction is important, and as the parasitic motion in the other direction is lower, the stress that is applied to the specimen is concentrated so that a stronger effect can be achieved. In this study, box-like, closed structure forging system to minimise parasitic displacement is designed and optimised by Taguchi method. A resonant frequency and a mode shape were analysed by means of a modal analysis. The processing direction displacement and parasitic displacement generated in the excitation horn was assessed by means of a harmonic analysis that actually added an excitation force. The displacement was measured to verify the design model and tested by very-high-cycle fatigue life testing. The results confirmed that the fatigue life was improved by micro forging.