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>

Zig-zag electrode pattern for high brightness in a super in-plane-switching liquid-crystal cell

Choi, Hyunchul,Yeo, Jun-ho,Lee, Gi-Dong Wiley (John WileySons) 2009 JOURNAL- SOCIETY FOR INFORMATION DISPLAY Vol.17 No.10

3-D Locomotive and Drilling Microrobot Using Novel Stationary EMA System

Hyunchul Choi,Kyoungrae Cha,Semi Jeong,Jong-oh Park,Sukho Park IEEE 2013 IEEE/ASME transactions on mechatronics Vol.18 No.3

<P>For 3-D locomotion and drilling of a microrobot, we proposed an electromagnetic actuation (EMA) system consisting of three pairs of stationary Helmholtz coils, a pair of stationary Maxwell coils, and a pair of rotating Maxwell coils in the previous research . However, this system could have limited medical applications because of the pair of rotational Maxwell coils. In this paper, we propose a new EMA system with three pairs of stationary Helmholtz coils, a pair of stationary Maxwell coils, and a new locomotive mechanism for the same 3-D locomotion and drilling of the microrobot as achieved by the previously proposed EMA system. For the performance evaluation of the proposed EMA system, we perform a 3-D locomotion and drilling test in a blood vessel phantom. In addition, the two EMA systems are compared to show that the newly proposed EMA system has 440% wider working space and 49% less power consumption than the previous EMA system.</P>

Wireless Biomimetic Swimming Mini-Robots Using Electro-Magnetic Actuation (EMA) System

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

For the actuation of mini-robots, various types of electromagnetic based actuation (EMA) methods were proposed. Compared with conventional actuation system using electric motor, EMA system has many advantages for the wireless actuation of mini-robots. This paper introduces our proposed biomimetic swimming mini-robots such as tadpole robot and jellyfish robot. The developed biomimetic swimming mini-robots could be driven by an external alternating magnet field using three pairs of Helmholtz coils. The swimming mini-robots consist of a buoyant swimming mini-robot body, permanent magnets, and fins. Especially, the tadpole swimming mini-robot has a single fin which is directly linked to the permanent magnet and the jellyfish swimming mini-robot has multiple fins which have a permanent magnet at the end of fins. The external alternating magnetic field from three pairs of Helmholtz coils could generate the propulsion and steering force of the tadpole mini-robot and the jellyfish mini-robot in 2- and 3-dimensional (D) space.

Two-dimensional actuation of a microrobot with a stationary two-pair coil system

Choi, Hyunchul,Choi, Jongho,Jang, Gunhee,Park, Jong-oh,Park, Sukho Institute of Physics Publishing 2009 Smart materials & structures Vol.18 No.5

<P>This paper proposes a new two-dimensional (2D) actuation method for a microrobot that uses a stationary two-pair coil system. The coil system actuates the microrobot by controlling the magnitude and direction of the external magnetic flux. The actuation of the microrobot consists of an alignment to the desired direction and a linear movement of the microrobot by non-contact electromagnetic actuation. Firstly, the actuation mechanism of the stationary coil system is theoretically derived and analyzed. Secondly, the tendency of the magnetic flux in the coil system are analyzed and compared by preliminary theoretical analysis. Through various locomotive experiments of the microrobot, the performance of the electromagnetic actuation by the proposed stationary two-pair coil system is evaluated. Using the proposed 2D actuation method, the microrobot is aligned to the desired direction by Helmholtz coils and is driven to the aligned direction by Maxwell coils. By the successive current control of the coil system, the microrobot can move along a desired path, such as a rectangular-shaped or a diamond-shaped path. </P>

Two-dimensional locomotion of a microrobot with a novel stationary electromagnetic actuation system

Choi, Hyunchul,Choi, Jongho,Jeong, Semi,Yu, Chungsun,Park, Jong-oh,Park, Sukho Institute of Physics Publishing 2009 Smart materials & structures Vol.18 No.11

<P>In this paper, we study the locomotion of a microrobot for intravascular therapy. As an intravascular microrobot has to be small, a conventional actuator, such as a micro-motor, and a battery cannot be integrated. To solve this integration problem, we analyze a microrobot with an electromagnetic actuation (EMA) system. Previously, an EMA system using two stationary coil pairs was proposed for the 2-dimensional (D) planar locomotion of a microrobot. The EMA system used two stationary pairs of Helmholtz coils and two stationary pairs of Maxwell coils in the <I>x</I>- and <I>y</I>-direction, respectively. This paper proposes a novel stationary EMA system using two pairs of Helmholtz coils and one pair of Maxwell coils. The 2D locomotion of the microrobot using the proposed EMA system is analyzed and verified by various experiments. The microrobot actuated by the proposed EMA system was able to move in the desired direction on the desired path. The comparison between the proposed EMA system and the previous EMA system showed that the proposed system had an 18% smaller volume and used 91% less coil current for the same actuation force than the previous EMA system. The proposed EMA system produced 2D locomotion of the microrobot, while having a small volume and a lower power consumption than the previous EMA system. </P>

Biomimetic Swimming Mini-Robots Using Electro-Magnetic Actuation (EMA) System

Hyunchul Choi,Semi Jeong,Cheong Lee,Youngho Ko,Seong Young Ko,Jong-Oh Park,Sukho Park 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

For the actuation of mini-robots, electromagnetic based actuation (EMA) methods were proposed. EMA system has many advantages for the wireless actuation of mini-robots. This paper introduces our proposed biomimetic swimming mini-robots such as tadpole robot and jellyfish robot. The biomimetic swimming mini-robots could be driven by an external alternating magnet field using three pairs of Helmholtz coils. The swimming mini-robots consist of a buoyant robot body, permanent magnets, and fins. Especially, the tadpole mini-robot has a single fin which is directly linked to the permanent magnet and the jellyfish mini-robot has multiple fins which have a permanent magnet at the end of fin. The external alternating magnetic field from three pairs of Helmholtz coils could generate the propulsion and steering force of the tadpole mini-robot and the jellyfish mini-robot in 2- and 3-dimensional (-D) space. Firstly, we demonstrated the fabrications of the EMA coil system and the mini-robots. Secondly, we summarized the locomotive algorithms of the mini-robots using EMA. Thirdly, we setup the control system for the EMA driven mini-robots, which consists of EMA coils, dual cameras, controller, power amplifier, and conventional joystick. Through various experiments, we evaluated the locomotion algorithms the swimming mini-robots using EMA system. Finally, we demonstrated the performances of the swimming mini-robots in 2-D and 3-D space.

Comparison of risk and protective factors associated with smartphone addiction and Internet addiction

Choi, Sam-Wook,Kim, Dai-Jin,Choi, Jung-Seok,Ahn, Heejune,Choi, Eun-Jeung,Song, Won-Young,Kim, Seohee,Youn, Hyunchul Akadémiai Kiadó 2015 JOURNAL OF BEHAVIOURAL ADDICTIONS Vol.4 No.4

<P><B>Background and Aims</B></P><P>Smartphone addiction is a recent concern that has resulted from the dramatic increase in worldwide smartphone use. This study assessed the risk and protective factors associated with smartphone addiction in college students and compared these factors to those linked to Internet addiction.</P><P><B>Methods</B></P><P>College students (<I>N</I> = 448) in South Korea completed the Smartphone Addiction Scale, the Young’s Internet Addiction Test, the Alcohol Use Disorders Identification Test, the Beck Depression Inventory I, the State–Trait Anxiety Inventory (Trait Version), the Character Strengths Test, and the Connor–Davidson Resilience Scale. The data were analyzed using multiple linear regression analyses.</P><P><B>Results</B></P><P>The risk factors for smartphone addiction were female gender, Internet use, alcohol use, and anxiety, while the protective factors were depression and temperance. In contrast, the risk factors for Internet addiction were male gender, smartphone use, anxiety, and wisdom/knowledge, while the protective factor was courage.</P><P><B>Discussion</B></P><P>These differences may result from unique features of smartphones, such as high availability and primary use as a tool for interpersonal relationships.</P><P><B>Conclusions</B></P><P>Our findings will aid clinicians in distinguishing between predictive factors for smartphone and Internet addiction and can consequently be utilized in the prevention and treatment of smartphone addiction.</P>

Three-Dimensional Swimming Tadpole Mini-Robot using Three-Axis Helmholtz Coils

Choi, Hyunchul,Jeong, Semi,Lee, Cheong,Park, Bang Ju,Ko, Seong Young,Park, Jong-Oh,Park, Sukho 제어로봇시스템학회 2014 Transaction on control, automation and systems eng Vol. No.

Electromagnetic-actuated robotic systems have been studied recently for special purposes. Because these systems use external magnetic fields to control their robots, the robots can have simple structures and move with much freedom. In particular, these electromagnetic actuation (EMA) systems are being widely adopted for the actuation of biomedical mini-robots and microrobots for minimally invasive surgery (MIS) and diagnosis. We previously reported, as a feasible biomedical robot, the biomimetic swimming tadpole mini-robot, which can only swim above water. Indeed, the two-dimensional (D) plane swimming tadpole mini-robot is limited in its use because of its motility in the 2D plane. Therefore, this paper proposes a 3D swimming tadpole mini-robot that can move freely in water. First, in the proposed 3D swimming tadpole mini-robot, the buoyancy force was regulated for subaqueous swimming, and the permanent magnet was rearranged for precise movement. Second, to attain a 3D swimming motion, the actuation mechanism of the robot was developed using an EMA system. Finally, various experiments verified that the proposed 3D swimming tadpole mini-robot can swim freely in a 3D water environment.

Exceptional Lithium Storage in a Co(OH)₂ Anode: Hydride Formation

Kim, Hyunchul,Choi, Woon Ih,Jang, Yoonjung,Balasubramanian, Mahalingam,Lee, Wontae,Park, Gwi Ok,Park, Su Bin,Yoo, Jaeseung,Hong, Jin Seok,Choi, Youn-Suk,Lee, Hyo Sug,Bae, In Tae,Kim, Ji Man,Yoon, Won- American Chemical Society 2018 ACS NANO Vol.12 No.3

<P>Current lithium ion battery technology is tied in with conventional reaction mechanisms such as insertion, conversion, and alloying reactions even though most future applications like EVs demand much higher energy densities than current ones. Exploring the exceptional reaction mechanism and related electrode materials can be critical for pushing current battery technology to a next level. Here, we introduce an exceptional reaction with a Co(OH)<SUB>2</SUB> material which exhibits an initial charge capacity of 1112 mAh g<SUP>-1</SUP>, about twice its theoretical value based on known conventional conversion reaction, and retains its first cycle capacity after 30 cycles. The combined results of synchrotron X-ray diffraction and X-ray absorption spectroscopy indicate that nanosized Co metal particles and LiOH are generated by conversion reaction at high voltages, and Co<SUB><I>x</I></SUB>H<SUB><I>y</I></SUB>, Li<SUB>2</SUB>O, and LiH are subsequently formed by hydride reaction between Co metal, LiOH, and other lithium species at low voltages, resulting in a anomalously high capacity beyond the theoretical capacity of Co(OH)<SUB>2</SUB>. This is further corroborated by AIMD simulations, localized STEM, and XPS. These findings will provide not only further understanding of exceptional lithium storage of recent nanostructured materials but also valuable guidance to develop advanced electrode materials with high energy density for next-generation batteries.</P> [FIG OMISSION]</BR>