Optimization and analysis of Helmholtz-like three-coil wireless power transfer system applied in gastrointestinal robots

Meng, Yicun,Wang, Zhiwu,Jiang, Pingping,Wang, Wei,Chen, Fanji,Yan, Guozheng The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.4

Wireless power transfer (WPT) systems based on magnetic resonance provides a possible method to supply energy for implantable medical devices, such as gastrointestinal robots and wireless capsule endoscopes. However, low power transfer efficiency (PTE) (most researches show it to be lower than 3%) and poor power received stability are the key limitation of WPT systems in such applications. Three-coil WPT systems are regarded as an effective method to improve the power transfer efficiency and power received of gastrointestinal robots. Thus, an analytical model of a three-coil inductive link was established in this paper. Then the power transfer efficiency of load coil was optimized by changing the coil turns and raising a novel coil configuration: a Helmholtz-like load coil. As a result, the power transfer efficiency and power deliver to load (PDL) of this three-coil WPT system are tremendously improved. To verify the proposed design, a prototype simulated the gastrointestinal robot working situation and it was implemented for an experimental test. The results obtained from the experimental test demonstrate that the proposed three-coil WPT system with 9 turns load coil and 40 turns receiving coil achieves a PTE of 4.32% and a PDL of 541.5 mW. Moreover, the best PTE attained by the novel Helmholtz-like load coil was 6.45% and the PDL was 845 mW.

3D Helmholtz Coil-based Hybrid Manipulation for Active Locomotion of Magnetic Micro/Nano Robots

Sung Hoon Kim Korean Magnetics Society 2018 Journal of Magnetics Vol.23 No.4

This study presents hybrid control based on three-axis Helmholtz coil for manipulation of magnetic micro/nano robots. In general, magnetic force and torque control requires both Maxwell and Helmholtz coils. Therefore, the configuration of the magnetic manipulation system is complex and requires many power supplies. The hybrid method controls the three-axis Helmholtz coil and three power supplies through mechanical switch control to generate magnetic force and torque. Magnetic torque is controlled by the three-axis Helmholtz coil with a rotating magnetic field, and magnetic force is controlled by generating gradient magnetic field through the separated coils by the switch control. Three switches separate each Helmholtz coil and six switches control the separated six coil with the three power supplies. The hybrid control can provide simple configuration of coil system, various active locomotion, and precision control in complex environments. To verify the proposed method, we conducted magnetic simulation with various experimental tests.

Position-based compensation of electromagnetic fields interference for electromagnetic locomotive microrobot

Choi, Jongho,Choi, Hyunchul,Jeong, Semi,Park, Bang Ju,Ko, Seong Young,Park, Jong-Oh,Park, Sukho SAGE Publications 2013 Proceedings of the Institution of Mechanical Engin Vol.227 No.9

<P>Recently, the locomotion of a microrobot wirelessly actuated by electromagnetic actuation systems has been studied in many ways. Because of the inherent characteristics of an electromagnetic field, however, the magnetic field of each coil in the electromagnetic actuation system induces magnetic field interferences, which can distort the desired electromagnetic field, preventing the microrobot from following the desired path. In this article, we used two pairs of Helmholtz coils and two pairs of Maxwell coils in a two-dimensional electromagnetic actuation system. Generally, the two pairs of Helmholtz coils generate the torque for the rotation of the microrobot and the two pairs of Maxwell coils generate the propulsion force of the microrobot. Both pairs of Helmholtz and Maxwell coils have to work to simultaneously align and propel the microrobot in a desired direction. In this situation, however, the electromagnetic fields produced by the Helmholtz coils can interfere with those produced by the Maxwell coils. This interference is closely dependent on the position of the microrobot in the region of interest inside the electromagnetic coils system. This means that the alignment direction and propulsion force of the microrobot can be distorted according to the position of the microrobot. Therefore, we propose a compensation algorithm for the electromagnetic field interference using the position information of the microrobot to correct the magnetic field interferences. First, the interference of an electromagnetic field obeying the Biot–Savart law is analyzed by numerical analysis. Second, a position-based compensation algorithm for the locomotion of a microrobot is proposed. Various locomotion tests of a microrobot verified that the proposed compensation algorithm could reduce the normalized average tracking error from 5.25% to 1.92%.</P>

헬륨홀츠 코일로 자화시킨 자속누설탐상의 수치모델링 연구

구자선,신영길 한국비파괴검사학회 2019 한국비파괴검사학회지 Vol.39 No.3

헬름홀츠 코일은 두 개의 동일한 코일들로 구성되는데 두 코일은 코일의 반경만큼 떨어져 있고 그 사이의 내부에 축 방향으로 균일한 선형 자기장을 발생시키는 특성이 있다. 본 연구에서는 헬름홀츠 코일에 의해 발생된 자기장으로 자성체 봉을 자화시키고 봉의 결함으로부터 발생되는 누설자속신호를 조사하였다. 누설자속신호는 봉 표면을 따라 홀 센서를 스캔하여 얻어지는데, 신호의 본질은 홀 센서를 수직으로 지나는 자속밀도 성분들이다. 이들을 유한요소 모델링을 통해 구하고 결함신호들을 조사, 분석하였다. 먼저 결함의 축 상 위치에 따라 전반적인 신호의 레벨이 다르게 나타나며, 같은 크기의 결함이라도 위치에 따라 신호의 형태가 다르게 나타난다는 것을 관찰할 수 있었다. 본 연구에서는 그 원인을 파악하여 신호들을 보정하였고 그 결과, 거의 같은 신호형태로 나타낼 수 있었다. 이러한 과정을 거치면서 결함의 정확한 크기 파악을 위해서는 결함이 코일의 중심에 위치하도록 하여 결함신호를 채취할 필요가 있음을 알 수 있었다. 결함의 깊이 및 폭 변화에 따른 누설자속신호의 변화도 조사하였는데, 깊이 변화는 신호에 비례하여 반영되지만 폭 변화의 경우에는 일정 폭까지는 신호가 커지다가 폭이 더 증가하면 오히려 감소하는 것을 관찰할 수 있었으며, 결함의 부피가 같더라도 깊이 변화가 폭 변화보다 더 민감하게 신호에 반영된다는 것을 알 수 있었다. 헬름홀츠 코일을 사용한 탐상결과는 일반 코일을 사용한 결과와 거의 비슷하게 나타남을 알 수 있었다. Helmholtz coils consist of two identical coils at a distance the size of a single coil’s radius. As a result, the coils generate uniform and linear magnetic fields in the axial direction between them. In this study, the magnetic fields generated by Helmholtz coils were used to magnetize a ferromagnetic rod to investigate magnetic flux leakage (MFL) signals due to defects in the rod. The flux leakage signal is the result of the magnetic flux density components flowing perpendicular to the Hall sensor. These signals were calculated and analyzed through finite element modeling. Results showed that the levels of the overall signals differ depending on the axial position rather than the size of the defect, as defects of the same size were evaluated. Investigation into the cause of this difference provided a correction method, the application of which then resulted in a nearly identical signal pattern. This study, established the necessity of measuring the defect signal with the defect positioned at the center of the Helmholtz coils in order to estimate its exact size. Defect signals from various defect depths and widths were also investigated. It was concluded that although the variation of defect depth was reflected proportionally on the MFL signal, the variation of defect width was not. It was also found that depth change is reflected more sensitively on the signal than changes in width, despite uniform defect volume. The use of Helmholtz coils produced nearly identical signals as those produced by ordinary coils.

3D Helical Motion of Capsule Endoscope Microrobot using Electromagnetic Actuation System

Cheong Lee,Hyunchul Choi,Semi Jeong,Donghai Li,Zhen Jin,Gwangjun Go,Kiduk Kwon,Seong Young Ko,Jong-oh Park,Sukho Park 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10

We propose a new electromagnetic actuation (EMA) system for a locomotion function of capsule endoscope microrobot. The EMA system consists of 3 pair of Helmholtz coils in x-y-z axis and 1 pair of Maxwell coils in z-axis and the capsule endoscope microrobot has a permanent magnet. Generally, the Helmholtz coils generate a uniform magnetic flux which can align the microrobot to an arbitrary desired direction and make a torque for the rotation of the microrobot. The Maxwell coils generate a uniform gradient magnetic flux which can propel the microrobot to the aligned direction. With the proposed EMA system, the capsule endoscope microrobot can show a precessional motion by the Helmholtz coils and an ascending motion by the z-axis Maxwell coils. By the precessional motion and the ascending motion of the capsule endoscope microrobot, it can push a wall of an esophagus and move inside an esophagus. Through various experiments using a spherical magnet and a glass tube, the feasibility and enhancement of the capsule endoscope microrobot using the proposed EMA system can be verified.

EMA System을 이용한 마이크로로봇의 3차원 구동에 관한 연구

정세미(Semi Jeong),최현철(Hyunchul Choi),최종호(Jongho Choi),박석호(Sukho Park),박종오(Jongoh Park) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

For treatment of cardiovascular disease and drug delivery, the locomotion mechanisms of microrobot have been studied. However, by the restriction of integration of rnicrorobot such as actuation part, sensing module and treatment tool, the development of microrobot is very difficult. For solving this problem, we propose a new electromagnetic actuation (EMA) system which can produce external actuation force by electromagnet field. In 3 dimensional (D) spaces, the EMA system is able to align microrobot to the desired direction and propels microrobot to the aligned direction. The proposed EMA system consists of a stationary Helmholtz-Maxwell coils pairs and a rotational Helmholtz-Maxwell coils pairs. For 3D locomotion of microrobot, two Helmholtz coils pair can magnetize and align the microrobot to desired direction and two Maxwell coils pair can produce propulsion force to microrobot. For the detailed actuation of microrobot in 3D space, the gravitational force of microrobot can be compensated. Finally, the performances of the proposed EMA system ware validated by various experiments.

초파리 집단의 선택불리에 관한 지구자기장 2배의 자기장 영향

김은태,정승문,박은규 圓光大學校 1996 論文集 Vol.31 No.2

본 연구에서는 한국 거제도의 자연집단 야생형 초파리와 가시돌연변이형 황색체-백색안 초파리를 Helmholtz coils장치를 이용해서 유도한 지구자기장 2배의 자기장내의 집단과 비교 집단인 지구자기장내의 집단에서 발생된 성적 선택빈도를 조사하여, 선택불리에 관한 다음과 같은 유전적 행동의 결과을 얻었다. 초파리 집단의 전체 평균 발생율은 Helmholtz coils장치를 이용해서 유도한 지구 자기장 2배의 지기장내의 집단과 지구자기장내 집단에서 각각 55.10%와 44.90%로 관찰되었다. 이 결과는 지구자기장내의 초파리 집단의 발생율이 지구자기장 2배의 초파리 집단의 발생율보다 상대적으로 낮은 수치로 조사되었다. 야생형 유전자를 운반한 염색체의 선택빈도는 20세대까지 전체 평균빈도가 위의 양집단에서 각각 0.7177과 0.7180으로 관찰되었다. 이 결과는 지구자기장 2배의 자기장 집단에서 더 높은 선택불리 행동을 보여 주었다. 돌연변이형 yw 유전자를 운반한 염색체의 선택빈도는 각각의 조절된 자기장내의 초파리 집단에서 각각 0.0349와 0.0372로 관찰되었다. 이 결과도 지구자기장 초파리 집단보다 지구자기장 2배의 자기장 초파리 집단에서 더 강한 선택불리를 보여 주었다. Duncan's multiple range test와 LSD값으로 유의차이 유무를 검정하였던 바 야생형 그룹과 다른 3개의 돌연변이형 그룹사이에서 고도의 유의차이가 있음이 밝혀졌다. To elucidate the genetic behavior of selective disadvantage among sex-linked mutants of Drosophila melanogaster bred and kept by the genetic study laboratory room, Wonkwang University and the wild type collected at Keojaedo island, and reared under the influence of two different strength of magnetic fields, i.e. the double and the ambient magnetic field, this study was carried out at the above indicated laboratory room. The over-all mean emergence rates of Drosophila melanogaster populations reared in controlled magnetic fields, i.e. the double using Helmholtz coils and the ambient showed 55.10% and 44.90% respectively. Referring to these data, the fly population raised in the ambient magnetic field showed a relatively lower emergence rate than the double magnetic field population. The mean selective frequencies of wild type gene-carrying chromosomes up to tweentieth generation, affected by two different magnetic fields, showed 0.7177 and 0.7180 with the magnetic field strength as mentioned other before. The data explains that Drosophila melanogaster population reared in the double magnetic field showed higher selective disadvantage. The selective frequencies of the individual of yw gene-bearing chromosomes showed 0.0349 and 0.0372 by the same order of magnetic field strength indicated above. It was shown that the fly population reared at the double strength generated by Helmholtz coils cleared the relatively strong selective disadvantage being 0.0349, however the opposite value was 0.0372 resulted from the ambient magnetic field. Through Duncan's multiple range test and LSD value, the highly significant differences between the wild type and anyone of the other three mutants were calculated.

A Study on 3D Locomotion of Intravascular Therapeutic Microrobot using EMA System

Semi Jeong,Hyunchul Choi,Cheong Lee,Kiduk Kwon,Gwangjun Go,Doo Sun Sim,Kyung Seob Lim,Myung Ho Jeong,Seong Young Ko,Jong-oh Park,Sukho Park 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10

In this paper, we proposed an intravascular microrobot using an EMA system with bi-plane X-ray fluoroscopy. The proposed EMA system consists of a pair of stationary Helmholtz-Maxwell coils in x-axis and a pair of rotational uniform-gradient saddle coils on x-axis. The microrobot using the EMA system can be aligned to the desired direction by the uniform magnetic field from the Helmholtz-uniform saddle coil pairs and can be propelled to the aligned direction by the uniform gradient magnetic field from the Maxwell-gradient saddle coil pairs. Based on this actuating principle, we developed the microrobot which can move and have a treatment function in blood vessel. For the position recognition of the microrobot, a bi-plane X-ray fluoroscopy was installed in the EMA system. The bi-plane X-ray fluoroscopy can provide frontal and lateral views of mini-pig and the image of the microrobot. In addition, the bi-plane X-ray fluoroscopy can be rotated together with the pair of rotational uniform-gradient saddle coils on x-axis. Through various in-vitro and in-vivo experiments, we could verify the feasibility of the proposed intravascular therapeutic microrobot.

새로운 전자기 구동 시스템을 이용한 2차원 평면 이동 마이크로 로봇

최현철(Hyunchul Choi),최종호(Jongho Choi),정세미(Semi Jeong),유충선(Chungsun Yu),박종오(Jongoh Park),박석호(Sukho Park) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

In this study, we examined the locomotion using of intravascular therapy microrobot with novel stationary electromagnetic actuation system. Locomotion of the microrobot is very important in various function of microrobot. However, by th size limitation of microrobot cannot be integrated a conventional actuator and a battery. To solve the actuation problem, we consider the locomotion of the microrobot with an Electromagnetic Actuation (EMA) system. Previously, an EMA system using two stationary coil pairs was proposed for the 2D planar locomotion of the microrobot. The EMA system used two stationary pairs of Helmholtz coils and of Maxwell coils in the x-and y-direction. This study proposes a novel stationary EMA system using two pairs of Helmholtz coils and one pair of Maxwell coils. The proposed EMA system can produce 2D locomotion of the microrobot, while having a small system volume and low power consumption than previous EMA system.

전자기 구동 시스템을 이용한 마이크로로봇의 3차원 이동 및 드릴링

이걸(Jie Li),최현철(Hyunchul Choi),차경래(Kyoungrae Cha),정세미(Semi Jeong),박종오(Jongoh Park),박석호(Sukho Park) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5

This paper proposed a novel electromagnetic-driven microrobot system with locomotion and drilling functions in 3D(dimensional) space. Because of the size limitation of the microrobot, it does not have actuator, battery and controller. Therefore, for the driving of the microrobot, electromagnetic actuation (EMA) systems were used. The proposed EMA system consists of three rectangular Helmholtz coil pairs in x, y and z axis and a Maxwell coil pair in z axis. The magnetic field generated in the EMA coil system could be controlled by the input currents of the EMA coils. The Helmholtz coil pairs were used to align the microrobot with the desired direction and also rotate it for the drilling function. In addition, the surface of the microrobot has many bumps to enhance the drilling performance. The Maxwell coil pair in z axis was used for the propulsion of the microrobot. Through the various experiments, Finally. The locomotion and drilling performances of the proposed EMA microrobot system were verified.