A Six-Dimensional Magnetic Localization Algorithm for a Rectangular Magnet Objective Based on a Particle Swarm Optimizer

To build a wireless capsule endoscope with active external guidance for controllable and interactive diagnosis on the gastrointestinal tract, it is necessary to track the capsule's 3-D position and 3-D orientation. An approach to tracking is to enclose a small rectangular permanent magnet in the capsule. The magnetic field produced around the body by the rectangular magnet can be detected by magnetic sensors outside the patient's body. With these detected magnetic sensor data, the 3-D localization and 3-D orientation parameters can be computed by an appropriate algorithm based on the mathematical model of the rectangular magnet's magnetic field. We tried several nonlinear optimization algorithms, and simulation experiments show that the particle swarm optimization algorithm can work effectively with good accuracy when the magnet moves within a predetermined range.      

Optimization method for permanent-magnet structures

A nonlinear optimization method useful for designing permanent-magnet structures is presented. The method determines an optimal arrangement of magnetic material so that the magnitude of the remanence is spatially uniform and the field generated by the magnet satisfies a set of prescribed linear constraints. In addition, it is shown how to impose auxiliary conditions on the remanence in order to simplify a magnet's fabrication. A uniform magnitude of the remanence is necessary if a magnet is to be constructed out of a single type of magnetic material     

Robust 3-D Motion Tracking From Stereo Images: A Model-Less Method

Traditional vision-based 3-D motion-estimation algorithms require given or calculated 3-D models while the motion is being tracked. We propose a high-speed extended-Kalman-filter-based approach that recovers camera position and orientation from stereo image sequences without prior knowledge, as well as the procedure for the reconstruction of 3-D structures. Empowered by the use of a trifocal tensor, the computation step of 3-D models can be eliminated. The algorithm is thus flexible and can be applied to a wide range of domains. The twist motion model is also adopted to parameterize the 3-D motion. It is minimal since it only has six parameters as opposed to seven parameters in quaternion and 12 parameters in matrix representation. The motion representation is robust because it does not suffer from singularities as Euler angles. Due to the fact that the number of parameters to be estimated is reduced, our algorithm is more efficient, stable, and accurate than traditional approaches. The proposed method has been applied to recover the motion from stereo image sequences taken by a robot and a handheld stereo rig. The results are accurate compared to the ground truths. It is shown in the experiment that our algorithm is not susceptible to outlying point features with the application of a validation gate.     

A Small Low-Cost Hybrid Orientation System and Its Error Analysis

Inertial orientation systems have many potential uses beyond air- and spacecraft applications. Compared to the conventional large-scale system, the novel aspects of an orientation system based on micro electromechanical systems (MEMS) are small size, lightweight, low-power consumption, and low cost by the inclusion of microsensors with on-chip functionality, such as micromachined rate gyroscopes, accelerometers, and etc. However, the performance associated with these low-cost MEMS sensors is generally not satisfied. A conventional strapdown method based on integral of angular rate to figure out attitudes will inevitably induce long-term drift. For eliminating this accumulative error and thus using the low-cost navigation system for a long-duration mission, a hybrid configuration by combining a MEMS-based azimuth-level detector with the conventional strapdown system is proposed in this paper. The azimuth-level detector is composed of three-axis MEMS accelerometers and three-axis MEMS magnetometers. With an absolute solution based on the gravity and the earth magnetic field rather than the integral algorithm, attitude and heading estimation without drift errors can be obtained so as to facilitate adjusting the attitude and heading for the conventional strapdown system. The hierarchical computation process for estimating the attitude and heading using the hybrid system is depicted first. Then, comprehensive system errors including transformation errors of the computation, such as skew, scale, and drift errors, are analyzed. Finally, it is verified by both of formula analysis and experimental test that the accumulative errors can be effectively eliminated via this hybrid scheme.      

磁流体浸没物磁场力分析及磁浮特性

物体浸没于磁流体中表现出磁浮特性，对其受力状态分析是准确描述其悬浮状态的前提和基础。基于非线性磁流体应力张量模型和稳态Bernoulli方程，建立磁流体中浸没物受力模型。借助非磁性体受力模型的简化计算方法以及磁性体与磁流体之间的多场效应关系，分别对非磁性体、磁性体两类浸没物在磁流体中所受磁浮力进行分析，结果表明非磁性浸没物在磁流体中仅受到外加磁场贡献的一次磁浮力，而磁性浸没物除受到一次磁浮力外，还受到其自身激发磁场贡献的二次磁浮力．永磁体在磁流体中位置决定的磁浮力满足一定条件时，永磁体能够自悬浮于磁流体中。     

近程光电视觉传感器感知物体空间信息的研究

本文论述了二种新型光电近程视觉传感器的工作原理、计算方法和系统构成。一种是由多个点光源和位置敏感器(PSD)构成的传感器,文中从误差分析、统计运算的角度出发推导出确定被测对象空间信息的算法;另一种是由多个点光源和单个探测元件构成的传感器,这种传感器通过对位相信息的测定来感知物体的三维信息。两种传感器都能得到被测点到传感器之间的距离信息及被测表面空间取向的信息。所论及的传感器可用于机器人对三维物表面轮廓的追踪运动以及提供物体形状的三维描述信息等方面。     

Adaptive nonlinear tool path optimization for five-axis machining

Current tool path computation in the CAM algorithms approximates the surface by piecewise linear interpolation. In the case of three-axis machining on a CNC machine the tool will exactly reproduce this computed tool path. However in the case of five-axis simultaneous machining the real tool path on the CNC machine will not follow the linear approximation computed by the conventional CAM algorithm. A new CAM algorithm is proposed which approximates the surface to be machined by a piecewise curved approximation. This curve represents the real tool path followed on the five-axis machine. This piecewise curved approximation is further optimized by formulating the tool path computation as the generation of a grid based on a variational smoothness penalty function. This new algorithm considerably improves the accuracy and reduces the number of blocks and machining time.     

矢量线阵二维波达方位估计的方法

声矢量传感器南声压传感器和质点振速传感器组成,它可以空间共点、时间同步测量声场的声压标量和振速矢量信息。钏对声压线阵无法同时分辨目标的方位角和俯仰角,而三维矢量传感器线阵会带来成本的增加和工程应用上的困难．利用二维矢量传感器组成的直线阵对目标的二维波达方位进行联合估计,详细推导了矢量阵MUSIC算法的数学表达式,并着重对矢量线阵在三维坐标不同轴上时对方位估计的影响进行了研究。仿真结果表明二维矢量线阵布放在水平的X轴或Y轴上时存在方位模糊．而布放在垂直的Z轴上时可以实现全空间无模糊定向,且对双目标也有较高的分辨率。     

Analytical design of permanent-magnet traction-drive motors

This paper presents an analytical method for the design of permanent-magnet (PM) traction-drive motors with emphasis on calculation of the magnet's volume and size. The method uses a set of formulas to properly size the magnets without the high effort of finite-element analysis (FEA). The formulas not only give optimized magnet sizes, but also provide quick solutions for the preliminary designs. The method can be used in the initial design stage to set up the base for FEA and optimization, as well as throughout the entire design and optimization process to validate a PM motor design. Numerical methods and experiments confirm the accuracy of the proposed method.     

Distributed odor source localization

This paper presents an investigation of odor localization by groups of autonomous mobile robots. First, we describe a distributed algorithm by which groups of agents can solve the full odor localization task. Next, we establish that conducting polymer-based odor sensors possess the combination of speed and sensitivity necessary to enable real world odor plume tracing and we demonstrate that simple local position, odor, and flow information, tightly coupled with robot behavior, is sufficient to allow a robot to localize the source of an odor plume. Finally, we show that elementary communication among a group of agents can increase the efficiency of the odor localization system performance.     

Design of a Halbach Magnet Array Based on Optimization Techniques

We have designed a Halbach magnet array by using a numerical optimization method based on finite-element analysis. The magnetization direction of each element is defined as the design variable. The optimal magnet arrays composed of two and three linear magnet layers can then be investigated to increase the attractive, repulsive, and tangential magnetic forces between magnet layers. We have applied a magnet array maximizing the tangential force to a torsional spring composed of two- and three-magnet rings. The two-dimensional finite-element analysis incorporates optimization techniques such as the sequential linear programming and the adjoint variable method.      

Design and implementation of an adaptive inverse controller for a micro-permanent magnet synchronous motor control system

An adaptive inverse controller design for a micro-permanent magnet synchronous motor control system is proposed. The adaptive inverse controller is constructed by using an adaptive model and an adaptive controller. The parameters of the adaptive model and adaptive controller are on-line tuned. By using the proposed adaptive inverse controller, the transient responses, load disturbance responses and tracking responses of the control system are improved. To detect the shaft rotor position, a micro-encoder is attached with the micro-permanent magnet synchronous motor. The micro-encoder provides only 100 pulses/revolution because of its space limitation. As a result, the resolution of the position signal and speed signal is not good enough. In order to improve the resolution, a state estimator is proposed here. By using the proposed state estimator, the control system can be operated from 1 to 25 000 r/min. The adaptive inverse control algorithm and the state estimation algorithm are executed by a digital signal processor, TMS320F28335. In addition, the proposed adaptive inverse control algorithm can be applied to the position control for the micro-permanent magnet synchronous motor as well. Several experimental results validate the theoretical analysis. The experimental results show that the proposed system has good performance including transient responses, load disturbance responses, and tracking responses.     

Laserbeschriftung von Hartferritmagneten zur Kennzeichnung von Druckgussteilen

With the presented method of magnetic labeling die cast components are labeled and provided with production data as well as protection against plagiarism. The magnetic labels are cast close under the surface of the component during the casting operation. Serial numbers, data and graphical information was engraved on the surface of hard ferrite magnets by laser marking using a diode-pumped ytterbium fiber laser. The data and graphical information was encoded as data matrix codes. Inexpensive strontium ferrite magnets were used. Melting processes and thermally induced material changes on the magnet surface during the laser labeling of the magnets results in a local demagnetization. The measurable decrease of the magnetic field strength is a result of local heating above the Curie temperature and the geometrical change of the magnet surface. The patterns with changing magnetic flux density can be visualized directly by a magnetic viewer or measured by magnetic field sensors such as Hall effect sensors. This paper deals foremost with the laser labeling process and the induced changes on the surface of the magnets as well as visualization and measuring test. First results of casting trials are presented, to confirm the stability of the magnetic labeling procedure during the casting operation.     

Selection of the parameters of a permanent magnet synchronous machine by using nonlinear optimisation

The selection of the parameters of a permanent magnet synchronous machine (PMSM) is analysed using nonlinear optimisation. The constraints of the optimisation can be set to take the control principle into account. Compared with previously presented analyses, constant flux-based control as well as an absolute maximum criterion where no constraints are made to the control principle is analysed. Moreover, the requirements of the application are easily incorporated into the presented optimisation as additional constraints. On the basis of the results, the parameters of the PMSM (permanent magnet's flux linkage and the direct and quadrature axis inductances) can be selected. The results show that when using a constant flux linkage-based control principle (e.g. direct-torque control) more torque can be obtained compared with minimum current vector control. After analysing the effect of different parameters, a design procedure is suggested and an interactive design programme is implemented with Matlab     

磁传感器在导航系统中的应用

介绍了一种基于磁传感器和加速度计,结构简单、低成本、高精度的方位传感器。该传感器利用当地的地磁场矢量和重力加速度矢量确定传感器在空间的姿态信息。分析了使传感器产生误差的各种因素,如温度影响、附近铁磁物体和噪声影响等,并给出了消除这些干扰因素影响的技术。实验研究表明,此传感器能够为移动机器人导航提供可靠的高精度姿态信息。     

Measuring the Magnetic Flux Density in the CMS Steel Yoke

The Compact Muon Solenoid (CMS) is a general purpose detector, designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6-m-diameter by 12.5-m-length free bore, enclosed inside a 10,000-ton return yoke made of construction steel. The return yoke consists of five dodecagonal three-layered barrel wheels and four end-cap disks at each end comprised of steel blocks up to 620 mm thick, which serve as the absorber plates of the muon detection system. Accurate characterization of the magnetic field everywhere in the CMS detector is required. To measure the field in and around the steel, a system of 22 flux loops and 82 3-D Hall sensors is installed on the return yoke blocks. Fast discharges of the solenoid (190 s time-constant) made during the CMS magnet surface commissioning test at the solenoid central fields of 2.64, 3.16, 3.68 and 4.01 T were used to induce voltages in the flux loops. The voltages are measured on-line and integrated off-line to obtain the magnetic flux in the steel yoke close to the muon chambers at full excitations of the solenoid. The 3-D Hall sensors installed on the steel–air interfaces give supplementary information on the components of magnetic field and permit to estimate the remanent field in steel to be added to the magnetic flux density obtained by the voltages integration. A TOSCA 3-D model of the CMS magnet is developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. The results of the measurements and calculations are presented, compared, and discussed.     

Numerical Simulations of vector field distributions generated by circular permanent-magnet arrays with side-openings

In the rotary-magnetic refrigerator, a circular permanent-magnet array with side-openings (CPMAS) provides a magnetic field exceeding the remanence of each magnet. Here we show that the magnetic induction in the pole gap as well as inside the magnets of a CPMAS can be calculated using an analytical vectorial formula. The method is based on the representation of the field of a uniformly magnetized magnet by straight current-carrying wires on the surface of the magnet. The Biot-Savart law gives the vector field of a single wire of arbitrary orientation, position, and length; the sum of fields from each wire gives the total field. The magnetization hysteresis loop of the permanent magnet is included by varying the current density; this is then used to calculate modifications to the center field by demagnetization, including remanence inversion under the field generated by the CPMAS itself. The field analysis procedure described here can be used to optimize the structure of permanent-magnet arrays, especially for three-dimensional arrays of restricted or asymmetric geometry, for various applications.     

Nonlinear compensation for non-contact electronic joystick with a single hall sensor

A new non-contact electronic joystick using a single hall-sensor, which detects a horizontal vector in the magnetic field, is demonstrated. Furthermore, the nonlinear characteristics between the output of the hall-sensor and the movement of the joystick bar are compensated to be linear. The dynamic horizontal vector of the magnetic flux is detected by the hall-sensor, whereas a permanent magnet is rotated with the joystick bar, which has a two-dimensional detecting area. Using the nonlinear adjustment equations, the output signals of the hall-sensor become linear, giving higher accuracy in two-dimensional movement. Through real experiments, it is shown that the single hall-sensor structure mechanism is superior to the dual-sensor structure in sensing two-dimensional motion without offset.     

直升机光电助降系统的双摄影测量算法及实验研究

基于信标的摄影测量定位技术,提出了一种用于光电助降系统的双摄影测量算法.利用两台CCD 摄像机探测直升机两侧各四个信标,建立目标坐标系、摄像机坐标系和图像坐标系,根据信标、镜头中心和信标像点的共线性得到关于旋转矩阵和平移矢量的线性方程组,由此计算出直升机相对于着降点的位姿.设计了一套直升机光电助降实验系统,使用高性能DSP 系统进行实时图像处理,运用双摄影测量算法实时计算直升机着降引导信息.模拟实验结果表明,在两摄像机距离着降点8～13 m 范围内,光电助降实验系统的距离测量精度达到±5 cm,而角度测量精度达到±3°.     

Dual camera calibration for 3-D machine vision metrology

A dual-camera calibration algorithm and procedure are presented. The algorithm is based on the method of direct linear transformation and results in an overdetermined set of linear algebraic equations that can be utilized in determining the coordinate position of some identifiable feature in a scene relative to any set of orthogonal axes. Both radial and tangential lens distortions are considered in a second step of the calibration algorithm to improve the accuracy of the position sensor. Since the algorithm incorporates both types of lens distortions, it can be applied to a camera with any combinations of lenses, e.g. a lens system with a supplementary lens for close-up observations