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.     

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.     

Miniaturized biopsy module using gripper tool for active locomotive capsule endoscope

Patient-friendly capsule endoscopes with a high-definition camera have gradually become a popular solution to the diagnosis of digestive systems. As a promising method for an active and precise diagnosis, an active locomotive intestinal capsule endoscope (ALICE) with wireless functionality using an electromagnetic actuation (EMA) system has been proposed. For a more precise diagnosis using a capsule endoscope, ALICE needs to have several additional functions, such as biopsy, drug delivery, and tattooing capabilities. Among these additional functions, this paper introduces a miniaturized biopsy module that can be integrated into ALICE. The proposed biopsy module, which uses a gripping tool, can be used to extract biopsy samples from a target lesion in a gastrointestinal organ. First, thanks to a controllable EMA system, along with the biopsy module, ALICE is driven to the target lesion in the intestinal tract using a generated magnetic field. Next, using a strong magnetic field, ALICE can open the gripper blade on its own and closely approach the target lesion. Finally, through the closing of the gripper blade, the biopsy sample can be harvested. The biopsy process is therefore controlled completely wirelessly through the interactions between the permanent magnet inside ALICE and the external magnetic field of the EMA system. A fabricated biopsy module with 13 mm diameter and 5 mm length was successfully integrated into an ALICE prototype 13 mm in diameter and 32 mm in length. Through an in-vitro experiment, we demonstrated the capability of ALICE when combined with the proposed biopsy module, such as its active locomotion and the extraction of a biopsy sample.     

Design Optimization of a Bidirectional Microswimming Robot Using Giant Magnetostrictive Thin Films

This paper presents a bidirectional optimization method on a wireless microswimming robot. The robot is developed based on fin beating propulsion employing two giant magnetostrictive thin films for left and right fins. An innovative drive approach, using separate second-stage resonance frequencies of the left and right fins to generate right and left thrusts, is proposed and implemented on a bidirectional microswimming robot prototype. Dynamic model of the proposed microrobot has been derived based on theoretical analysis. A discrete variate method for optimizing left fin configuration is proposed under the constraints of fixed surface area and sufficient fin end strength, and a genetic algorithms method for optimizing right fin configuration is employed under constraints of symmetry and linearity of bidirectional swimming. Simulation and experimental results have demonstrated that bidirectional swimming performance of the robot is greatly improved with low driving frequency and a large range of swimming speed in both directions.      

Electromagnetic field intensity triggered micro-biopsy device for active locomotive capsule endoscope

For an active and precise diagnosis, we developed an active locomotive intestinal capsule endoscope (ALICE), which can be wirelessly driven and controlled using an electromagnetic actuation (EMA) system. Since then, there has been a need to develop a biopsy device integrated into ALICE which can take a biopsy sample inside the gastrointestinal tract for a historical analysis of cancer disease. Toward this goal, this paper proposes a smart-triggered biopsy device for the ALICE using a micro-reed switch, where the integrated micro-reed switch is turned on using a strong magnetic field, and the biopsy device mechanism is activated by a micro-reed switch. To execute the biopsy process, first, the ALICE with the biopsy device is driven by an EMA system, where a moderate intensity magnetic field is used for driving the ALICE to reach a target region on the intestinal wall. After that, by increasing the magnetic field above a critical value, the ALICE is pushed hard against the target lesion, the micro-reed switch is turned on, and the biopsy device is triggered. The biopsy process, therefore, is totally wirelessly controlled by the external magnetic field of the EMA system, without an additional controller module. The prototype of the biopsy device, with dimensions of 12 mm in diameter and 5 mm in length, was integrated into the ALICE and the prototype of the ALICE, with the biopsy device having dimensions of 12 mm in diameter and 32 mm in length. The working principle and mechanism of the proposed biopsy device are introduced and the feasibility of ALICE with the biopsy device is demonstrated through in-vitro experiments.     

Development of high field permanent magnet

Permanent magnets are believed to be applicable only to make small and weak magnets. It is possible, however, to make a magnet with much higher strength than those in the past by introducing a saturated iron pole. Cooling down the magnet further enhances the field strength to a great extent. We have demonstrated that a permanent dipole magnet exceeding a typical permanent magnet more than by factor 3 is possible. A new challenge is to conceive such magnet for an accelerator application where time dependent alternating field is often requested.     

内燃机车永磁同步发电系统的研究

永磁同步发电系统具有体积小、重量轻、效率高、运行可靠等优点,已成为未来轨道交通牵引系统重要组成部分的发展趋势。本文主要介绍一种应用于内燃机车的永磁同步发电系统,首先分析了永磁同步发电机的外特性,其次从发电系统主电路构成和系统控制策略两个方面进行设计,最后通过系统建模与仿真,验证永磁同步发电系统的正确性与可行性。     

Modeling and control of a new horizontal-shaft hybrid-type magneticbearing

This paper reports on the development of a new horizontal-shaft hybrid-type magnetic bearing system. The bearing system will be used for a horizontal-shaft machine. The rotor is levitated due to the repulsive force between a stator and a rotor permanent magnet (PM). A lower cost and higher radial stiffness have been achieved by using a strontium-ferrite magnet on the rotor and an Nd-Fe-B PM above and below the rotor magnet. A finite-element analysis was performed to calculate the levitation force and radial stiffness. An upper stator magnet subtending an angle of 45° provides the best compromise between a large levitation force and radial stiffness. A model for the horizontal-shaft hybrid magnetic bearing system has been developed and includes the effect of the rotor dynamics and the electromagnetic forces. An integral servocontroller was designed to stabilize the axial position. The controller has been implemented in a digital signal processor. Experimental results performed on a prototype system are in agreement with the theoretical results     

SU-8微针执行器的研究

设计和采用MEMS工艺技术制作了一种由电磁驱动的微量取样执行器。执行器的结构包括微针、通道、反应室、电极以及永磁微阵列等。通过外部磁场可以实现双向线性驱动。本文主要介绍了利用SU 8光刻胶材料 ,采用多级曝光实现 3D结构的工艺技术 ,研制出了微针执行器的雏形器件。微针的尺寸为 6 0 0 μm× 80 0 μm× 4 0 μm ,微针孔径截面为 2 0 μm× 2 0 μm ,并给出了SEM分析的研究结果     

Precision stage using a non-contact planar actuator based on magnetic suspension technology

The precision stage using a novel contact-free planar actuator based on magnetic forces, magnetized force and Lorentz force, is suggested. In the promising magnetic structure, a mover is levitated by magnetized force between iron-core electromagnets attached under the upper-side of a stator and ferromagnetic plates belonging to the mover. And the mover is driven by Lorentz force that acts on permanent magnets with an identical polarity put under magnetic field by air-core coils. Namely, the mover is driven directly without any transmission mechanism, and does not need any auxiliary driver for its posture calibration. Then it is estimated that the proposed operating principle is very suitable for work requiring high accuracy and cleanness, or general-purpose nano-stage. In this paper, we discuss a driving principle of the planar system including the magnetic force generation mechanism, a framework for the force model, governing characteristics of the levitated plate, and a planar motion control of the constructed prototype. And experimental results are given to verify the derived theoretical model and the feasibility of the system.     

Design and control of a novel spherical permanent magnet actuator with three degrees of freedom

The paper describes the design and control of a new version of a spherical permanent magnet actuator, which is capable of three degrees of freedom and a high specific torque. Based on an analytical magnetic field distribution, the torque vector and back-emf are derived in closed forms. An optimal design procedure is proposed to achieve maximum output torque or maximum acceleration for a given payload. The control of the actuator, whose dynamics are similar to those of robotic manipulators, is facilitated by the establishment of a complete actuation system model and the application of the computed torque control law. The validity of the analysis and design techniques, and the effectiveness of the control strategy, are confirmed by measurements.     

Noncontact conveyance of conductive plate using omni-directional magnet wheel

A magnet wheel is chosen as the driving method to transfer a conductive plate without mechanical contact in space, due to its high force density. When permanent magnets (hereafter PMs) constituting the magnet wheel rotate below the conductive plate, not only a repulsive type of normal force but also a traction torque is generated on the plate. To utilize the torque as a thrust force, the magnetic fields from PMs are covered partially using a magnetic shield plate. So, in-plane positions of the conductive plate are controlled by turning the shield plate opened partially. In this paper, the operating principle of the noncontact conveyance system using a magnet wheel is discussed, including experimental verification. Specially, the resulting force from the suggested magnet wheel is AC force with oscillation, but it can be minimized through varying entry or exit shape of the open area of the magnetic shield plate.     

Sensorlose INFORM-geregelte Permanentmagnet-Außenläufermotoren für Industrie, Automotive und Traktion

In this paper, the optimization of external rotor permanent magnet motors with respect to sensorless position detection using the INFORM method is presented. The external rotor type offers special advantages in drives with high torque demand, especially at low speed and standstill. Typical applications are elevators, starter-generators and traction drives. Furthermore, the paper shows the calculation of reluctance properties due to saturation and geometry using numerical field calculation. This is an important fact for high-performance position estimation using the INFORM method. The accuracy of position estimation reaches a few electrical degrees; therefore it is fully sufficient for practical application in the mentioned fields. At the Institute of Electrical Drives and Machines at Vienna University of Technology, such PM external rotor drives have been designed, built and tested. The sensorless operation has been verified successfully.     

Intelligent switching control of a pneumatic muscle robot arm using learning vector quantization neural network

Pneumatic cylinders are one of the low-cost actuation sources used in industrial and prosthetic application, since they have a high power/weight ratio, high-tension force and long durability. However, problems with the control, oscillatory motion and compliance of pneumatic systems have prevented their widespread use in advanced robotics. To overcome these shortcomings, a number of newer pneumatic actuators have been developed, such as the McKibben Muscle, Rubber Actuator and Pneumatic Artificial Muscle (PAM) Manipulators. In this paper, the solution for position control of a robot arm with slow motion driven by two pneumatic artificial muscles is presented. However, some limitations still exist, such as a deterioration of the performance of transient response due to the changes in the external load. To overcome this problem, a switching algorithm of the control parameter using a learning vector quantization neural network (LVQNN) is proposed in this paper. The LVQNN estimates the external load of the pneumatic artificial muscle manipulator. The effectiveness of the proposed control algorithm is demonstrated through experiments with different external working loads.     

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.     

槽楔材料对PMLSM电磁特性的影响

为提高PMLSM的电磁性能并降低齿槽力和推力波动,文中提出一种在直线电机槽口安装槽楔的解决方案。槽楔材料对电机性能影响较大,为了使电磁性能最佳,文中以分数槽永磁直线同步电机为研究对象,分析了槽楔材料为硬磁、软磁和非磁时对电机气隙系数的影响。利用有限元法对比分析了3种槽楔材料下电机的气隙磁场、反电动势、齿槽力和推力波动等电磁性能,并对不同负载下削弱推力波动的程度进行对比。分析结果表明,硬磁性材料可以有效降低齿槽力和推力波动。最后研究了不同相对磁导率下硬磁性材料对电机性能的影响,并得到电机性能最佳时的相对磁导率值,为进一步提高电机性能提供了理论基础。     

Functional design features and initial performance characteristicsof a magnetic-implant guidance system for stereotactic neurosurgery

A helmet with a roughly cubic array of six superconducting coils is used to apply force on a small permanent magnet pellet in brain or in brain phantom material. This apparatus, called the Magnetic Stereotaxis System, will be used to deliver drugs and other therapies directly into deep brain tissues, under control of a computer and fluoroscopic imaging system. This paper considers only the force application aspects of the instrument. The primary design features of the helmet and power supply controls are presented, along with field plot data and single-axis motion results. The field plot data show that agreement with the finite-element iron-free field calculations is sufficiently high (>1%) for the instrument. These preliminary motion data indicate accuracy better than 2 mm for the impulsive pellet motion, even though the visual position observations had significantly greater error than the completed imaging system will have. The companion paper will take up analysis of the control aspects of the motion, and the authors' recent solutions to difficulties found in the experimental work described here     

Permanent magnet pulse motor with high temperature superconductinglevitation

A simple but stable noncontact high T_c superconducting levitation system with a vertical shaft has been presented. The levitation system consists of a superconductor and permanent magnets. In the system, a high T_c superconductor supports a lower end of the shaft, and a pair of permanent magnets supports the other end. Although a levitation is stable when the levitation system is used, since the restoring force is small in the horizontal direction, the levitation stability is small in the horizontal direction. Hence, it is difficult to drive the shaft by electromagnetic forces in using such motors. This paper describes a driving system consisting of six coils and a permanent magnet with eight poles, in which balance forces act on two opposite sides of the disc type rotor in the axial direction. The system has no unbalance force, and stable rotation is obtained without control. To validate the proposed system, experimental tests have been carried out. The experimental motor achieved stable rotation at speeds up to 1250 rpm     

电磁驱动推拉式射频MEMS开关的设计与制作

提出了一种新型电磁驱动推拉式射频MEMS开关。针对传统静电驱动单臂梁开关所需驱动电压大、恢复力不足等问题,设计了一种推拉式开关结构,降低了驱动电压(电流),提高了开关的隔离度,同时实现了单刀双掷的功能。单晶Si梁由于自身无应力,解决了悬臂梁残余应力引起的梁变形问题。通过理论计算和有限元分析,优化了开关设计尺寸,在外围永磁铁磁感应梯度dB/dz=100T/m,在线圈通入100mA电流的驱动下,单晶Si扭转梁末端可以获得约10μm的弯曲量,满足开关驱动要求。给出了开关的详细微细加工流程,对开关的传输参数进行了测试,在10GHz时隔离度为-40dB.     

Design and evolution of a piezoelectrically actuated miniature swimming vehicle

This work details the design of a miniature swimming vehicle that propels itself through oscillations of a flexible fin mounted in the stern. The fin is driven through a mechanism that is actuated by two curved-beam bending piezoelectric actuators. An optimization routine is used to design the mechanism for rigid body guidance. The actuators are modeled statically using the Bernoulli-Euler method. Hamilton's principle is applied to the actuators and, by employing the modal analysis, a dynamic actuator model is developed and compared to experimental data. The physical evolution of the swimming vehicle is discussed, and a prototype for an on-board digital control circuit is evaluated. The latest vehicle design, which incorporates on-board digital control, is presented in terms of its design and experimentally determined the performance characteristics. The current swimming vehicle prototype achieves fish-like maneuvering and an approximate velocity of 0.25 m/s.