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슬관절 수술용 전기소작 완드에 적용되는 형상기억합금 코일스프링의 설계인자에 따른 회복력 및 행정거리의 관계
양영규(Young-Gyu Yang),원성연(Sung-Yeon Won),김철웅(Cheol-Woong Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The Electrosurgical Knee Wand (EKW) offers a radio frequency ablation method using plasma for coagulation or removal of targeted tissues inside of knees. However, it is necessary to develop an actuator which is controllable in human body in order to improve accessability and accuracy for ablation of tissues and simultaneously prevent any excess costs using the actuators with rigid heads. Therefore, in this study, we established a Tensile SMA Spring model, which would maximize shape memory effect of the actuator from Shape Memory Alloy wires, and performed a dynamic characteristic test for practical application. In addition, the test was elaborated by considering variations in design factors of the model for observing its design control and effect. Specifically, the variations were diameters of SMA wire and internal and external diameters of SMA springs. They were rapidly cooled off after 30-minute heat treatment at 500℃. The experiment was also conducted to evaluate displacement of the SMA springs with their free length of 4~5 ㎜ and extended length when it was fixed on an acrylic plate parallel to the force gauge. For temperature control, the current with a pre-established programmable DC power supply was injected. We measured temperature, force and displacement as the shape of the SMA spring was restored with the current injection. The temperature data, 1Hz, was measured with a thermometer, restoring force, 10㎐, with a force gauge and actuator's stroke, 10㎐, with a digital displacement sensor.
슬관절 수술용 전기소작완드에 적용되는 형상기억합금 코일스프링의 회복력 및 행정거리의 관계
양영규(Young-Gyu Yang),한기봉(Gi-Bong Han),김철웅(Cheol-Woong Kim) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.12
슬관절 소작용 완드(Electrosurgical Knee Wand, EKW)는 고주파 소작법으로 슬관절 인대, 조직 등의 응고, 삭마, 절제, 등에 적용된다. EKW와 radiofrequency를 이용한 조직응고, 삭마 등의 슬관절 수술에서 수술안전성, 편의성 및 성공률을 극대화하기 위해서는 병변에 매우 정확하고 안전하게 EKW가 선택적 접근을 할 수 있도록 유도하는 탁월한 방향조종제어능이 핵심기술이다. 따라서 본 연구에서는 대퇴경골부 제한적인 공간에서 가장 적합한 수술용 의료기기 액추에이터로 판단되는 형상기억합금(SMA) 와이어를 이용하여 형상기억효과를 극대화할 수 있는 SMA 인장스프링 모델을 제작하여 실험을 수행하였다. 또한 SMA의 열전기적 특성 및 전류변화에 따른 온도특성에 대한 연구를 수행하고 SMA 인장스프링의 설계조건에 따른 회복력 및 행정거리의 관계를 평가하였다. 그 결과, SMA 인장스프링의 직경이 작아질수록 최대온도는 증가하였다. 전류인가 15초의 경우는 전류량 증가와 힘의 증가가 비례한 반면 전류인가 30초는 매우 불안정한 결과가 나타났다. 반면, 전류량 증가와 행정거리(TS) 증가 관계는 전류인가 15초일 때가 전류인가 30초일 때보다 더 안정적인 결과가 나타났다. Electrosurgical knee wand (EKW) is a high-frequency thermocautery instrument and is often used for coagulation, ablation, excision, and extirpation of knee ligaments and tissues. In order to maximize the success rate, ease, and safety of knee surgery using EKW and radiofrequency ablation, it is necessary to ensure that the EKW selectively approaches the lesion with utmost accuracy and safety. The key feature of this instrument is its excellent maneuverability. Hence, the authors constructed a tensile spring model based on a shape memory alloy (SMA), which exhibits the shape memory effect. This model can be used in knee surgery as it is considered the most biocompatible femorotibial surgical actuator. The changes in external temperature with current and the thermoelectric characteristics of the SMA were investigated. The relationship between the restoring force and the typical stroke (TS) in response to the conditions in the SMA tensile spring design were evaluated. In conclusion, as the diameter of the SMA tensile spring decreased, the maximum temperature increased. The strain in the actuator caused a stable and proportional increase in the force and induced current for up to 15s, but this increase became very unstable after 30s. Moreover, the relationship between the current and the TS was more stable than that between the current and the restoring force.
수핵성형술용 형상기억합금(SMA) 액추에이터 와이어의 열처리 조건 변화가 온도제어 파라미터(t1)에 미치는 영향
오동준(Dong-Joon Oh),김철웅(Cheol-Woong Kim),양영규(Young-Gyu Yang),김태영(Tae-Young Kim),김재정(Jay-Jung Kim) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.5
차세대 의료기기 시장을 변화시킬 것으로 기대되는 형상기억합금(SMA) 기반의 최소침습용 의료기기는 시술자의 손동작과 같은 유연성과 섬세함을 구현할 수 있는 장점이 있다. 그러나 SMA의 비선형 열전기적 특성으로 인해 SMA 기반 차세대 의료기기 엑추에이터는 자유로운 방향조종 구현이 제한적이고 상용화에 있어서 큰 한계성으로 작용한다. 본 논문은 SMA의 효과적인 온도제어를 위해 전류-온도간의 개방루프 계단응답을 분석하고 1차 미분방정식 해와 비교하여 온도제어에 필요한 파라미터 ?을 도출한 뒤 실험적으로 그 기능을 검증하였다. 또한 ?은 전류를 입력으로 온도를 출력으로 하는 시불변 선형계의 특성함수의 폴(pole)이므로 주파수에 의한 온도제어에 관계된 파라미터인 것으로 나타났다. 본 논문의 결과는 SAM 기반의 차세대 의료기기 액추에이터의 효과적인 위치제어 설계에 응용될 수 있다. Shape Memory Alloy (SMA) has recently received attention in developing implantable surgical equipments and it is expected to lead the future medical device market by adequately imitating surgeons' flexible and delicate hand movement. However, SMA actuators have not been used widely because of their nonlinear behavior called hysteresis, which makes their control difficult. Hence, we propose a parameter, t1, which is necessary for temperature control, by analyzing the open-loop step response between current and temperature and by comparing it with the values of linear differential equations. t1 is a pole of the transfer function in the invariant linear model in which the input and output are current and temperature, respectively; hence, t1 is found to be related to the state variable used for temperature control. When considering the parameter under heat treatment conditions, Tmax was found to assume the lowest value, and t1 was irrelevant to the heat treatment.
Min-Hyung Park(박민형),Cheol-Woong Kim(김철웅),Young-Gyu Yang(양영규) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
With the technological advances in the development of the surgical instruments, the mimimally invasive surgery(MIS) and natural orifice transluminal endoscopic surgery(NOTES) have gotten wider acceptance than the traditional endoscopic and laparoscopic surgeries. In the laparo-endoscopic single-site surgery(LESS™), the number of ports made on a patient's abdominal wall can be reduced, and then, it will result in the fast recovery time, less hospital stay, and even less or no scars. However, the use of flexible laparoscopic instruments is essential to perform the LESS™. In this study, a new articulable joint of the laparoscopic instrument was designed by shape memory alloy (SMA) wires, and its articulation dependent on the amplitude and duration of the current was measured. Moreover, the amount of error when a certain position was maintained was also calculated.
하지강성 가변 인공건 액추에이터(Leg Stiffness controllable Artificial Tendon Actuator, LeSATA™)의 개발
한기봉(Gi-Bong Han),어은경(Eun-Kyung Eo),지대원(Dae-Won Jee),양영규(Young-Gyu Yang),김철웅(Cheol-Woong Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
If we can design a knee actuating mechanism as a primary actuator for supporting knee extension, it might be possible to revolutionarily store or release elastic strain energy, which is consumed during the gait cycle, and as a result leg stiffness is expected to increase. In this case, it is necessary to design an ankle actuating mechanism as a secondary actuator which will adjusted excessive artificial leg stiffness from the primary actuator by reserving or releasing the elastic strain energy, because the energy, which is a part of kinetic and potential energy generated by human walking and is temporarily reserved in collision phase, will be discharged in rebound phase of elastic recoil. Dissimilar to previous study, we assumed that the leg stiffness could be increased by controlling walking speed with relative angular velocity of two segments and accordingly we are currently developing a knee-ankle two actuator system. As mentioned above, however, the artificial knee actuating will generate a new compensatory mechanism in the ankle part. It suggests that excessive leg stiffness caused by the artificial knee actuating will lead to a stumbling gait in abnormal collision phase accompanied by foot touch-down. Therefore, in designing the actuators we also considered the increase in walking speed and stumbling from repetitive acceleration in swing phase of previous gait cycles, satisfying the conditions with regard to relative angular velocity of two segments, thigh and shank, in order to raise leg stiffness. Furthermore, it might be difficult to confirm the effectiveness of the actuators if kinematic energy from unnecessary human walking is released under artificial deceleration control, which was designed to prevent an increase in walking speed. Therefore, we believed that the solution for the compensatory mechanism in ankle joint would be conversely derived by confirming the effect of changes in metatarsophalangeal joint tilt angle and walking speed on knee movement. Accordingly, we invented a new generation leg stiffness actuator in order to avoid the stumbling gait from the ankle joint compensatory mechanism caused by leg stiffness. The trademark of the device is called Leg Stiffness Artificial Tendon Actuator (LeSATA™). The stiffness between two springs could be variably controlled by adding eccentric mass inside the actuator, LeSATA. We also verify the functionality of the actuator which will automatically transfer between walking and running mode by actively monitoring any changes in gait pattern of LeSATA™ and in relative angular velocity between thigh and shank.
와전류탐상에 의한 미세혈관 문합용 마이크로링-핀시스템(AnaFix<SUP>®</SUP>)의 자기장민감성 및 전기전도도 평가
박천웅(Cheon-Woong Park),서용범(Yong-Beom Seo),지대원(Dae-Won Jee),양영규(Young-Gyu Yang),김철웅(Cheol-Woong Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Automated devices for microvascular anastomoses are more frequently used lately and the Microvascular Anastomotic Coupler (MAC) System is widely known for its clinically proven ring-pin system. In this study, we also developed a new anastomotic coupler system, AnaFix<SUP>®</SUP>, for secure end-to-end anastomoses. The coupler system consists of two rings and six pins inserted for each ring. Titanium Ti-6Al-4V and HDPE (High Density Polyethylene) are commonly used for micro-sized rings and pins, respectively, due to its bio-compatibility as well as accurate and consistent anastomoses. However, the pins produced by Ti-6Al-4V, which would be permanently implemented, can cause non-uniformity in MRI images by interfering them as artifacts. Therefore, it is necessary to evaluate electric current density, magnetic field sensitivity and electrical conductivity of the Ti-6Al-4V pins in human body to prevent the image distortions created by them. For the study, we performed the following simulations. 1) Calculation of electric current density from the pins in a 1T~4T(Telsa) magnetic field. 2) Evaluation of electrical conductivity of the electric current density. 3) Verification of magnetic susceptibility with comparative displacement of the pins.