Swimming microrobot actuated by two pairs of Helmholtz coils system

Various electromagnetic based actuation (EMA) methods have been proposed for the actuation of microrobots. The advantage of EMA is that it can generate a wireless driving force for the microrobot, and this is the reason why many researchers have focused on the EMA driven microrobot. This paper proposes a swimming microrobot driven by an external alternating magnet field using two pairs of Helmholtz coils. The microrobot with a fish like shape consists of a buoyant robot body, a permanent magnet, and a fin. Especially, the fin is directly linked to the permanent magnet and is swung by the alternating magnet field. The external alternating magnetic field generates the propulsion and steering force of the microrobot. In this paper, firstly, we design and fabricate the EMA coil system and the tadpole type microrobot. Secondly, we propose the locomotive mechanism of the microrobot using EMA. Thirdly, we set up the control system for the EMA driven microrobot. Finally, through various experiments, we demonstrate and evaluate the performance of the swimming microrobot.     

E波段折叠波导行波管集成极靴结构设计及仿真

为进一步提升毫米波折叠波导行波管的输出功率,通过整体加工的工艺方法,将折叠波导慢波结构和周期永磁聚焦系统在母材上同时加工,形成一种集成极靴结构。基于圆形注电子光学系统,设计了E波段折叠波导行波管的集成极靴结构。利用三维电磁场模拟软件(CST)的微波工作室,设计并模拟了慢波结构的冷特性参数,并根据慢波结构尺寸设计周期永磁聚焦系统。通过电磁工作环境仿真软件(OPERA)对磁场进行仿真验证,最终整管粒子数值模拟(PIC)计算结果表明,在61~71 GHz频带内可获得大于1 kW的饱和输出功率。该集成极靴结构在提供强轴向磁场的同时,具有结构紧凑、散热性好等优点。     

Design and Simulation of Pole Piece for Focusing of Multi-beam Electron Gun

The design of the aperture in the pole piece of a multi-beam confined-flow electron gun has been studied using the commercially available code OPERA 3D and validated the results using the CST particle studio, and the OmniTrak simulation tools. The results obtained by these tools are in good agreement with respect to the beam-waist radius and the throw of the electron gun. The square aperture proved to be a better option than circular aperture in providing the axisymmetric and uniform magnetic field. The shape and size of the pole piece have been optimized to enhance the laminarity of the electron beam using square aperture.     

Sequential Magneto-Actuated and Optics-Triggered Biomicrorobots for Targeted Cancer Therapy

Micro/nanorobots have the potential to be remotely propelled and manipulated in complex biological fluid and organ tissue. However, the combination of the sophisticated physiological barriers, remote-controlled navigation, real-time motion tracking, and diagnostic/therapeutic effects are tremendous challenges for application and translation. An unique sequential magneto-actuated and optics-triggered biomicrorobot (AI microrobot) for actively targeted cancer treatment is prepared. The AI microrobot consists of two components, magnetospirillum magneticum (AMB-1), providing the ability to autonomously swim toward the tumor site via internal hypoxia-driven effects and an external applied magnetic field, and indocyanine green nanoparticles, acting as a fluorescence imaging agent and photothermal therapy. The AI microrobots are tracked in vivo by fluorescence and magnetic resonance imaging. It is found that the AI microrobots can sequentially migrate to the hypoxic internal area of tumors and then effectively eradicate solid tumors through photothermal therapy under NIR laser irradiation. The sequential magneto-actuated and optics-triggered AI microrobots platform described here presents a bioinspired strategy toward remotely controlled propulsion, actively targeted cargo delivery, and satisfactory therapeutic performance in the circulatory system.     

Manipulation of micro-particles using a magnetically actuated microrobot

Recently, various micromanipulation methods using a microrobot have been studied in medicine and biology. In particular, the methods based on the use of a microrobot actuated by an electromagnetic actuation (EMA) system have received much attention because the microrobot using EMA system has free locomotion and precise controllability. These advantages of an electromagnetic actuated microrobot can be used to manipulate micro-particles. Previously, we proposed a 2-dimensional (2D) locomotive microrobot using EMA system and realized the free 2D locomotion of a microrobot of 10 mm length and 1 mm diameter. In this paper, we propose a microrobot for the manipulation of micro-particles. First, we fabricate a microrobot of desired shape and size by the conventional micro-molding technique. Second, we control the fabricated microrobot by using a 2D EMA system and test its basic performances such as directional controllability and velocity. The results of these basic tests confirmed that the microrobot had precise directionality with direction error from 1.52 deg. to 2.16 deg. and moving velocity range from 2.34 mm/s to 18.67 mm/s. In addition, the microrobot has the positioning errors in the 0.07–0.12 mm range and the propulsion force of the microrobot is continuously changed in proportional to the applied current in Maxwell coil. Finally, the proposed microrobot and its EMA system were tested for their ability to position a micro-particle. The results confirmed that the microrobot using the EMA could be used for the manipulation of various micro-particles.     

Design and Implementation of a Micromanipulation System Using a Magnetically Levitated MEMS Robot

Magnetic levitation of microrobots is presented as a new technology for micromanipulation tasks. The microrobots were fabricated based on microelectromechanical systems technology and weigh less than 1 g. The robots can be positioned in 3-D using magnetic field. It is shown that microrobots can be produced using commercially available magnets or electrodeposited magnetic films. A photothermal microgripper is integrated to the microrobots to perform micromanipulation operations. The microgrippers can be actuated remotely by laser focusing that makes the microrobot free of any wiring. This leads to increased motion range with more functionality in addition to dust-free motion and ability to work in closed environments. The 3-D motion capability of the microrobots is verified experimentally and it was demonstrated that the microgrippers can be operated in a vertical range of 4 mm and a horizonal range of 4 mm $,times,$5 mm. Micromanipulation experiments such as pick-and-place, pushing, and pulling were demonstrated using objects with 100 $mu$ m and 1 mm diameter.      

毫米级全方位微装配机器人的识别、定位及运动控制

介绍了一种毫米级全方位微机器人,设计用于微型工厂中的微装配操作.采用外部计算机视觉系统进行监控,先利用CCD摄像头捕捉微型机器人顶部及夹钳上的特征标志,再通过设计的视觉处理方法,实现了对微机器人的高精度识别和定位.在利用计算机视觉进行反馈控制的基础上,采用了对装配平台进行分区、快速前进与高精度步进相结合的运动控制策略,实现高精度的微装配任务.实验验证了以上方法和策略的有效性.     

A new type of fish-like underwater microrobot

This paper presents a new prototype model of an underwater fish-like microrobot utilizing ionic conducting polymer film (ICPF) actuator as the servo actuator to realize swimming motion with three degrees of freedom. A biomimetic fish-like microrobot using ICPF actuator as a propulsion tail fin and a buoyancy adjuster for the swimming structure in water or aqueous medium is developed. The overall size of the underwater prototype fish shaped microrobot is 45 mm in length, 10 mm in width, and 4 mm in thickness. It has two tails with a fin driven respectively, a body posture adjuster, and a buoyancy adjuster. The moving characteristic of the underwater microrobot is measured by changing the frequency of input voltage from 0.1-5 Hz in water and the amplitude of input voltage from 0.5-10 V. The experimental results indicate that changing the amplitude and frequency of input voltage can control the swimming speed of proposed underwater microrobot.     

软磁样品对半浸没式物镜的影响及故障排除

由于半浸没式物镜极靴下方存在磁场,用扫描电镜表征磁性样品时存在因样品被吸入物镜而严重影响成像的风险.本文中,日立S4700型场发射扫描电镜突然出现图像信噪比急剧下降、像散不能消除的问题,经过分析和排查发现是由软磁性的泡沫镍被吸入物镜极靴导致的故障.本文从物镜结构、合轴、像散三个方面分析了磁性样品对电镜成像的影响,并结合...     

Systematic design of double-sampling /spl Sigma//spl Delta/ A/D converters with a modified noise transfer function

Double-sampling /spl Sigma//spl Delta/ analog-digital converters (ADCs) are sensitive to path mismatch which causes quantization noise to fold into the signal band. A recent solution for this problem consists of modifying the noise transfer function (NTF) of the modulator such that it has one or several zeros at the Nyquist frequency, next to those in the baseband. In this brief, we present a systematic design strategy for such ADCs. It consists of finding optimal pole positions for the modified NTF. This can be combined with optimizing the zeros as well. Next, we introduce several efficient structures that have enough degrees of freedom to realize the optimized pole positions.     

Fundamental characteristics of a magnetoresistive sensor using Y1Ba2Cu3O7-x ceramicsuperconducting films

The fundamental characteristics of a magnetic sensor fabricated from a Y₁Ba₂Cu₃O_7-x ceramic superconducting film are investigated. The operation principle of the sensor is based on the magnetoresistive properties of the material. The Y₁Ba₂Cu₃O_7-x ceramic film was prepared by the spray pyrolysis method. An element of the magnetic sensor consists of the film patterned to a meander shape. the sensitivity is discussed in connection with the noise measurement of the element. A magnetic field resolution of 2×10^-6 G/(Hz) ^1/2 at 100 Hz was obtained in the 0.1-100 G range. The sensitivity is much higher than that of a conventional semiconductor magnetic sensor. With an AC modulation provided by a magnetic field, phase detection of the magnetic field can be performed using a lock-in amplifier. An improvement in the low-frequency (<1 Hz) magnetic field resolution of about one order of magnitude was obtained using this method     

A very thin power amplifier multichip module for 1.9-GHz cellularphone systems

A compact thin power amplifier module for 1.9-GHz cellular phone systems has been incorporated using MCM-D technology and planarization technology of all passive components. The module consists of four Si-MOSFETs and is 9.4×7.2×1 mm, resulting in a volume of 0.07 cc including its shield metallic case. The module was designed with the computer simulator, Libra, and simplified lumped-element equivalent circuits of passive components. The fabricated module exhibited an output power of 33.3 dBm and power efficiency of 29%. These results suggest that these technologies will be very useful for the miniaturization of circuit components for GHz-band mobile communications     

MCG simulations with a realistic heart-torso model

Magnetocardiograms (MCGs) simulated high-resolution heart-torso model of an adult subject were compared with measured MCGs acquired from the same individual. An exact match of the measured and simulated MCGs was not found due to the uncertainties in tissue conductivities and cardiac source positions. However, general features of the measured MCGs were reasonably represented by the simulated data for most, but not all of the channels. This suggests that the model accounts for the most important mechanisms underlying the genesis of MCGs and may be useful for cardiac magnetic field modeling under normal and diseased states. MCGs were simulated with a realistic finite-element heart-torso model constructed from segmented magnetic resonance images with 19 different tissue types identified. A finite-element model was developed from the segmented images. The model consists of 2.51 million brick-shaped elements and 2.58 million nodes, and has a voxel resolution of 1.56×1.56×3 mm. Current distributions inside the torso and the magnetic fields and MCGs at the gradiometer coil locations were computed. MCGs were measured with a Philips twin Dewar first-order gradiometer SQUID-system consisting of 31 channels in one tank and 19 channels in the other     

激光在线测厚振动分析与精度优化

激光测厚具有安全可靠、测量精度高、测量范围大等优点,广泛应用于纸张、电池极片等薄膜类材料厚度的在线测量。带材宽幅方向扫描测厚时由于扫描架往复运动会产生机械振动,影响在线测厚精度。针对该问题,以锂离子电池极片厚度测量为例,使用双激光差动式测厚平台对电池极片和铜箔分别进行厚度测量,然后对测厚数据进行频谱分析,探究其振动规律的相似性,并基于频谱分析结果采用滑动带阻滤波方式对测厚数据进行处理,滤波后极片和铜箔的厚度极差分别降低了33.4%和73.8%,有效过滤了机械振动导致的测量误差,可满足极片和铜箔厚度测量的精度要求。     

A mobile microrobot actuated by a new electromagnetic wobblemicromotor

Microactuators are perhaps the most critical components of micromechatronic systems. Micromotors with diameters in the range between 10-1 mm are needed, but are not readily available for practical use. This paper describes a teleoperated mobile microrobot, actuated by a new electromagnetic wobble micromotor, and designed to participate in the “International Micro Robot Maze Contest" organized every year in Nagoya, Japan. This competition is an excellent benchmark to compare the performance of different microactuators. The working principle, design, fabrication, and performance of the wobble micromotor are described. The microrobot has a volume of 1 cm³ and incorporates two wobble micromotors, the rotors of which are the driving wheels. The micromotor generates a torque of 350 μN·m at each step and a maximum speed of about 180 r/min. The operator controls the motion of the microrobot by a remote joystick connected to the microrobot by flexible ultraminiature wires. The microrobot is highly maneuverable, has a maximum speed of 10 cm/s and can climb a slope of 15°. Two microrobots, which differ only in some constructive details, were fabricated. A smaller version (4-mm diameter) of the wobble micromotor has been developed for use in an innovative miniature robot system for diagnosis and intervention in the colon     

W波段大功率集成极靴式互作用结构研究

针对W波段大功率折叠波导行波管的技术难点,提出了一种一体式加工的集成极靴式互作用结构,该结构将直角型折叠波导嵌入到极靴中,实现注-波互作用结构与聚焦系统的集成,提高周期永磁系统的聚焦能力,再通过增加阴极发射的电子注电流,实现功率的提升。文中首先介绍了集成极靴式互作用结构,提供该结构中慢波结构的尺寸参数,计算其色散特性及耦合阻抗曲线,并设计了相应的磁聚焦系统。最终对互作用结构进行仿真模拟,在90~100 GHz频带内可获得高于700 W的饱和输出功率。带内饱和增益均小于20 dB,可有效防止自激振荡的产生,该互作用结构可广泛应用于级联功率放大模块的后级放大器中。     

Analysis of Negative-Saliency Permanent-Magnet Machines

In this paper, a negative-saliency permanent-magnet (PM) synchronous machine analysis is presented. This particular saliency feature is achieved by replacing a portion of the magnet material by a soft iron piece over the rotor pole. In this manner, the d-axis inductance is increased, whereas the q-axis inductance is almost not affected, leading to the condition that Ld is higher than Lq (negative saliency) corresponding to the inverse condition of typical PM machines. An expression for the optimum pole configuration is derived. It is shown that, with appropriate control of the stator current based on the machine's saliency, the unfavorable effects of magnet reduction on torque production can be compensated. It is also shown that the machine saliency affects the location of the operating points when it operates under vector control. Finally, the theoretical analysis is validated with experimental results obtained from a prototype axial-flux PM machine that exhibits negative saliency.     

折叠波导慢波结构特性的研究

应用电磁场仿真软件对折叠波导慢波结构进行理论分析、结构设计和数值模拟。计算和分析了折叠波导的色散特性和散射参量,根据折叠波导特殊结构采用了整体极靴结构。模拟得出了折叠波导的周期磁场,通过调节磁场大小对电子注进行有效聚焦,并得到了电子束在磁场中的运动轨迹。结果表明,折叠波导是一种很适合用作毫米波大功率行波管的慢波结构。     

In vivo MR-tracking based on magnetic signature selective excitation

A novel magnetic resonance (MR)-tracking method specifically developed to locate the ferromagnetic core of an untethered microdevice, microrobot, or nanorobot for navigation or closed-loop control purpose is described. The tracking method relies on the application of radio-frequency (RF) excitation signals tuned to the equipotential magnetic curves generated by the magnetic signature of the object being tracked. Positive contrast projections are obtained with reference to the position of the magnetic source. A correlation function performed on only one k-space line for each of the three axes and corresponding to three projections, is necessary to obtain a 3-D location of the device. In this study, the effects of the sphere size and the RF frequency offset were investigated in order to find the best contrast noise ratio (CNR) for tracking. Resolution and precision were also investigated by proper measurement of the position of a ferromagnetic sphere by magnetic resonance imaging (MRI) acquisition and by comparing them with the real position. This method is also tested for a moving marker where the positions found by MRI projections were compared with the ones taken with a camera. In vitro and in vivo experiments show the operation of the technique in tortuous phantom and in animal models. Although the method was developed in the prospect of new interventional MR-guided endovascular operations based on miniature untethered devices, it could also be used as a passive tracking method using tools such as catheters or guide wires.     

In Vivo MR-Tracking Based on Magnetic Signature Selective Excitation

A novel magnetic resonance (MR)-tracking method specifically developed to locate the ferromagnetic core of an untethered microdevice, microrobot, or nanorobot for navigation or closed-loop control purpose is described. The tracking method relies on the application of radio-frequency (RF) excitation signals tuned to the equipotential magnetic curves generated by the magnetic signature of the object being tracked. Positive contrast projections are obtained with reference to the position of the magnetic source. A correlation function performed on only one k-space line for each of the three axes and corresponding to three projections, is necessary to obtain a 3-D location of the device. In this study, the effects of the sphere size and the RF frequency offset were investigated in order to find the best contrast noise ratio (CNR) for tracking. Resolution and precision were also investigated by proper measurement of the position of a ferromagnetic sphere by magnetic resonance imaging (MRI) acquisition and by comparing them with the real position. This method is also tested for a moving marker where the positions found by MRI projections were compared with the ones taken with a camera. In vitro and in vivo experiments show the operation of the technique in tortuous phantom and in animal models. Although the method was developed in the prospect of new interventional MR-guided endovascular operations based on miniature untethered devices, it could also be used as a passive tracking method using tools such as catheters or guide wires.