External Permanent Magnet Research Articles

Research on constant tension yarn transfer control technology based on AGA-PID and FOC algorithm

To solve the problems of poor real-time tension tracking, large overshoot, long adjustment time, and large tension fluctuation error that exist in the current control system for yarn feeding in the circular weft knitting machine, this paper presents an optimized and improved adaptive genetic algorithm (AGA) for adjusting the PID (Proportional Integral Derivative) parameters of the tension control part of the yarn-conveying system (AGA-PID). The algorithm is combined with the field-oriented control technology of the permanent magnet synchronous motor to design a closed-loop control strategy for the yarn-conveying system of a circular weft knitting machine. The MATLAB-Simulink simulation model was used to analyze the external tension loop-based AGA-PID controller and permanent magnet synchronous motor dual closed-loop control strategy of the yarn transport control system. The experimental verification was conducted by constructing an experimental platform that simulates the real process of yarn transportation. The outcomes of system simulations and experiments have consistently demonstrated that the AGA-PID control algorithm outperforms the GA-PID and PID control algorithms in terms of overshooting, response speed, stability, and anti-jamming ability. The yarn transport control system, which is designed to operate based on an AGA-PID control algorithm, is capable of reducing the fluctuations in tension that occur during the transportation of yarn and exhibits enhanced control accuracy, effectively stabilizing yarn tension control during the conveying process. The application of this algorithm can enhance the overall elasticity uniformity and surface flatness of knitted fabrics, thereby facilitating the realization of adjustable and controllable local elasticity in fabrics.

Drag reduction utilizing a wall-attached ferrofluid film in turbulent channel flow

This study explores the application of a wall-attached ferrofluid film to decrease skin-friction drag in turbulent channel flow. We conduct experiments using water as a working fluid in a turbulent channel flow set-up, where one wall is coated with a ferrofluid layer held in place by external permanent magnets. Depending on the flow conditions, the interface between the two fluids is observed to form unstable travelling waves. While ferrofluid coating has been previously employed in laminar and moderately turbulent flows (Reynolds number $Re<4000$ ) to reduce drag by creating a slip condition at the fluid interface, its effectiveness in fully developed turbulent conditions, particularly when the interface exhibits instability, remains uncertain. Our primary objective is to assess the effectiveness of ferrofluid coating in reducing turbulent drag with particular focus on scenarios when the ferrofluid layer forms unstable waves. To achieve this, we measure flow velocity using two-dimensional particle tracking velocimetry (2D-PTV), and the interface contour between the fluids is determined using an interface tracking algorithm. Our results reveal the significant potential of ferrofluid coating for drag reduction, even in scenarios where the interface between the surrounding fluid and ferrofluid exhibits instability, with observed drag reduction rates up to 95 %. In particular, waves with an amplitude significantly smaller than a viscous length scale positively contribute to drag reduction, while larger waves are detrimental, because of induced turbulent fluctuations. However, for the latter case, slip outcompetes the extra turbulence so that drag is still reduced.

A New Data-Driven Diagnosis Method for Compound Fault of Mixed Eccentricity and Demagnetization in External Rotor Permanent Magnet Motors

A New Data-Driven Diagnosis Method for Compound Fault of Mixed Eccentricity and Demagnetization in External Rotor Permanent Magnet Motors

Microscale fiber-integrated vector magnetometer with on-tip field biasing using N - V ensembles in diamond microcrystals

In quantum sensing of magnetic fields, ensembles of nitrogen-vacancy centers in diamond offer high sensitivity, high bandwidth and outstanding spatial resolution while operating in harsh environments. Moreover, the orientation of defect centers along four crystal axes forms an intrinsic coordinate system, enabling vector magnetometry within a single diamond crystal. While most vector magnetometers rely on a known bias magnetic field for full recovery of three-dimensional (3D) field information, employing external 3D Helmholtz coils or permanent magnets results in bulky, laboratory-bound setups, impeding miniaturization of the device. Here, a novel approach is presented that utilizes a fiber-integrated microscale coil at the fiber tip to generate a localized uniaxial magnetic field. The same fiber-tip coil is used in parallel for spin control by combining dc and microwave signals in a bias tee. To implement vector magnetometry using a uniaxial bias field, the orientation of the diamond crystal is preselected and then fully characterized by rotating a static magnetic field in three planes of rotation. The measurement of vector magnetic fields in the full solid angle is demonstrated with a shot-noise-limited sensitivity of 19.4nT/Hz1/2 and microscale spatial resolution while achieving a fiber sensor head cross section of less than 1mm2. Published by the American Physical Society 2024

Design and multi‐objective optimisation of double‐layer non‐uniform Halbach external‐rotor permanent magnet synchronous motor

AbstractIn order to further improve the output torque and stability of the external rotor permanent magnet synchronous motor, a double‐layer non‐uniform Halbach external rotor permanent magnet synchronous motor (DNH) structure is proposed and optimised. Finite element models of DNH and other structures are established to compare the electromagnetic characteristics of these motors and verify the superiority of the proposed structure. Secondly, the multi‐objective whale optimisation algorithm is improved, and the algorithm is tested by test function to verify the improvement effect. Further, the Spearman correlation of the parameters is calculated, and the parameters are layered. The first layer parameters are optimised by the improved multi‐objective whale optimisation algorithm, and the second layer parameters are optimised by parameter scanning. Finally, the motor performance of the initial scheme, single layer optimisation scheme, and hierarchical optimisation scheme is compared by simulation. The simulation results show that the hierarchical optimisation method is superior to the single layer optimisation method. By comparing with other schemes, the performance advantages of hierarchical optimisation DNH in terms of average output torque, cogging torque, torque ripple, permanent magnet cost and other parameters are proved, as well as the effectiveness of the optimisation method.

Optimal Motion Control of a Capsule Endoscope in the Stomach Utilizing a Magnetic Navigation System with Dual Permanent Magnets.

We propose a method to control the motion of a capsule endoscope (CE) in the stomach utilizing either a single external permanent magnet (EPM) or dual EPMs to extend the examination of the upper gastrointestinal tract. When utilizing the conventional magnetic navigational system (MNS) with a single EPM to generate tilting and rotational motions of the CE, undesired translational motion of the CE may prevent accurate examination. We analyzed the motion of the CE by calculating the magnetic torque and magnetic force applied to the CE using the point-dipole approximation model. Using the proposed model, we propose a method to determine the optimal position and orientation of the EPM to generate tilting and rotational motions without undesired translational motion of the CE. Furthermore, we optimized the weight of dual EPMs to develop a lightweight MNS. We prototyped the proposed MNS and experimentally verified that the developed MNS can generate tilting and rotational motions of the CE without any translational motion.

Design and Comparison of External Permanent Magnet Topologies for Improving Motion Control in Gastrointestinal Examination

Design and Comparison of External Permanent Magnet Topologies for Improving Motion Control in Gastrointestinal Examination

Hybrid trajectory planning of two permanent magnets for medical robotic applications

Independent robotic manipulation of two large permanent magnets, in the form of the dual External Permanent Magnet (dEPM) system has demonstrated the possibility for enhanced magnetic control by allowing for actuation up to eight magnetic degrees of freedom (DOFs) at clinically relevant scales. This precise off-board control has facilitated the use of magnetic agents as medical devices, including catheter-like soft continuum robots (SCRs). The use of multiple robotically actuated permanent magnets poses the risk of collision between the robotic arms, the environment, and the patient. Furthermore, unconstrained transitions between actuation inputs can lead to undesired spikes in magnetic fields potentially resulting in unsafe manipulator deformation. This paper presents a hybrid approach to trajectory planning for the dEPM platform. This is performed by splitting the planning problem in two: first finding a collision-free physical path for the two robotically actuated permanent magnets before combining this with a path in magnetic space, which permits for a smooth change in magnetic fields and gradients. This algorithm was characterized by actuating each of the eight magnetic DOFs sequentially, eliminating any potential collisions and reducing the maximum undesired actuation value by 203.7 mT for fields and by 418.7 mT/m for gradients. The effect of this planned magnetic field actuation on a SCR was then examined through two case studies. First, a tip-driven SCR was moved to set points within a confined area. Actuation using the proposed planner reduced movement outside the restricted area by an average of 41.3%. Lastly, the use of the proposed magnetic planner was shown to be essential in navigating a multi-segment magnetic SCR to the site of an aneurysm within a silicone brain phantom.

Design and Optimization of External Rotor Consequent Pole Permanent Magnet Motor with Low Iron Loss and Low Torque Ripple

To reduce the iron loss and torque ripple of an external rotor consequent pole (ERCP) motor used in an electric vehicle air-conditioning compressor, the magnetic pole structure of the motor was improved, and an unequal piecewise consequent pole (CP) structure was designed. The performance of the motor is optimized by reducing the harmonic content in the air gap flux density and reducing the iron saturation degree of the motor. The designed CP structure can significantly reduce the iron loss and torque ripple of the motor. Based on the Taguchi method, the optimal size parameters of the unequal piecewise CP structure are determined, and the final optimization design scheme is obtained. The results of finite element simulation and high-precision iron loss model show the following: compared with the original motor, the iron loss and torque ripple of the motor with the final optimized design scheme are significantly reduced.

Investigating morphological, optical and magnetic properties of blended novel ZnO-Ag/NiFe2O4 nanocomposite

Metal oxide nanoparticles and magnetic nanoparticles are combined to create magnetic nanocomposites (MNCs) with unique physical, chemical, and biological properties. A new ZnO-Ag/NiFe2O4 ternary magnetic nanocomposite was created in the current study using a simple and straightforward solid-phase mixing process with subsequent thermal treatment. The structural, optical, and magnetic properties of the ZnO-Ag/NiFe2O4 nanocomposite were studied using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDAX), vibrating sample magnetometry (VSM), and Raman spectroscopy. Brunauer–Emmett–Teller (BET) analysis was performed to analyze the surface area and average pore diameter of the nanocomposite. Cyclic voltammetry and photoelectrochemical analysis were performed to study the electrical behavior and charge carrier concentrations. According to XRD studies, the ZnO-Ag/NiFe2O4 nanocomposite is composed of the hexagonal wurtzite of ZnO and the spinel cubic structure of NiFe2O4. FESEM analysis revealed that the crystals of the nanocomposite were nearly spherical, and EDAX elemental mapping indicated that the elements were evenly dispersed across the sample without any impurities. The average diameter of the ZnO-Ag/NiFe2O4 nanocomposite obtained from the TEM images was nearly 50.65 nm. The specific surface area and average pore diameter of the ZnO-Ag/NiFe2O4 nanocomposite were 13.58 m2/g and 4.33 nm, respectively, according to BET analysis. CV analysis revealed a sharp increase in the specific capacitance of the ZnO-Ag/NiFe2O4 nanocomposite. The specific capacitances of the 1 M NaOH electrolyte, ZnO nanoparticles and ZnO-Ag/NiFe2O4 nanocomposite were 55.7302 F/g, 53.947 F/g, and 87.229 F/g, respectively, at a 0.05 V/s scan rate. With a coercive field (Hc) of 167 Oe, remnant magnetization (Mr) of 0.73 emu/g, and saturation magnetization (Ms) of 6.58 emu/g, the blended magnetic nanocomposite ZnO-Ag/NiFe2O4 exhibited superparamagnetic behavior at ambient temperature. Using an external permanent magnet, the ZnO-Ag/NiFe2O4 nanocomposite may be extracted from the reaction mixture, indicating its probable environmental and biomedical application.

Multi-objective optimization design of external rotor permanent magnet synchronous motor for robot arm

Multi-objective optimization design of external rotor permanent magnet synchronous motor for robot arm

Simplified Design of PM Machine for Spacecraft Electro-Mechanical Batteries

Electromechanical Batteries have important advantages comparing to chemical batteries and using them is popularized specially in Low Earth Orbit satellites recently. External rotor Permanent Magnet machines are used in these systems as Motor/Generator. Simplified parametric design method is given for PM machine design in this paper. Finite element based simulations are used to confirm design presses and show less than 7% error in parametric design that is acceptable for simple primary design.

Cogging Torque Reduction in PM machines Used in Electro-Mechanical Battery

Electro-Mechanical Batteries have important advantages comparing chemical batteries and using them is popularized specially in Low Earth Orbit satellites recently. External rotor Permanent Magnet machines are used in these systems as Motor/Generator. The main problem of these machines is their cogging torque originated from high strength PM's. Different methods for cogging torque reduction are available, anyway not all of them are applicable in spacecraft EMB’s machines. In this paper different method of cogging torque will be investigated and proper manners will be extracting. Finite Element Method (FEM) simulations are used for this aim.

Closed-Loop Magnetic Manipulation for Robotic Transesophageal Echocardiography

This article presents a closed-loop magnetic manipulation framework for robotic transesophageal echocardiography (TEE) acquisitions. Different from previous work on intracorporeal robotic ultrasound acquisitions that focus on continuum robot control, we first investigate the use of magnetic control methods for more direct, intuitive, and accurate manipulation of the distal tip of the probe. We modify a standard TEE probe by attaching a permanent magnet and an inertial measurement unit (IMU) sensor to the probe tip and replacing the flexible gastroscope with a soft tether containing only wires for transmitting ultrasound and IMU data and show that six-degree-of-freedom (DOF) localization and five-DOF closed-loop control of the probe can be achieved with an external permanent magnet based on the fusion of internal inertial measurement and external magnetic field sensing data. The proposed method does not require complex structures or motions of the actuator and the probe compared with existing magnetic manipulation methods. We have conducted extensive experiments to validate the effectiveness of the framework in terms of localization accuracy, update rate, workspace size, and tracking accuracy. In addition, our results obtained on a realistic cardiac tissue-mimicking phantom show that the proposed framework is applicable in real conditions and can generally meet the requirements for teleoperated TEE acquisitions.

Global Dynamic Analysis of a Typical Bistable Piezoelectric Cantilever Energy Harvesting System

This paper focuses on global dynamic behaviors of a bistable piezoelectric cantilever energy harvester with a tip magnet and a single external permanent magnet at the near side. The initial distance between the magnetic tip mass and the external magnet is altered as a key parameter for the enhancement of the energy harvesting performance. To begin with, the dynamical model is established, and the equilibria as well as potential wells of its non-dimensional system are discussed. Three different values of the initial distance are selected to configure double potential wells. Next, the saddle-node bifurcation of periodic solutions in the neighborhood of the nontrivial equilibria is investigated via the method of multiple scales. To verify the validity of the prediction, coexisting attractors and their fractal basins of attraction are presented by employing the cell mapping approach. The best initial distance for vibration energy harvesting is determined. Then, the Melnikov method is utilized to discuss the threshold of the excitation amplitude for homoclinic bifurcation. And the triggered dynamic behaviors are depicted via numerical simulations. The results show that the increase of the excitation amplitude may lead to intra-well period-2 and period-3 attractors, inter-well periodic response, and chaos, which are advantageous for energy harvesting. This study possesses potential value in the optimization of the structural design of piezoelectric energy harvesters.

Magnetically recyclable Cu-BTC@Fe3O4-catalyzed synthesis of cyano functionalized chroman-4-ones

An intramolecular radical cascade acyl-cyanation of o-(allyloxy)benzaldehydes with Me3SiCN using magnetically recyclable Cu-BTC@Fe3O4 catalyst (BTC = 1,3,5-benzenetri- carboxylate) and peroxides as the stoichiometric oxidants affords 3-cyanomethyl-functionalized chroman-4-ones in moderate to good yields. The catalyst can be readily recovered with an external permanent magnet, with slight decrease in its activity after successive five runs.

Torque Ripple Suppression Research of V-Shaped External Rotor Permanent Magnet Motor

Aiming at the problems of large torque ripple and poor output torque performance of external rotor permanent magnet synchronous motors, this paper took a three-phase 24-slot 19-pole external rotor motor as the research object, uses the magnetic circuit method and Lorentz theorem to analyze and calculate the motor torque, and improved the output torque by optimizing the position parameters of the V-shaped permanent magnet. The output torque was further optimized by a circular groove on the side of the stator teeth. The finite element simulation results show that the output performance of the motor can be improved by selecting the proper permanent magnet position. Stator tooth chooses slot position for Z = 1.2 mm, R = 3.5 mm torque ripple when dropped by 81.9%, up 7.6% on the output torque, motor performance is improved.

Independently Actuated Soft Magnetic Manipulators for Bimanual Operations in Confined Anatomical Cavities

Soft magnetic manipulators offer the prospect of improved surgical outcomes through their potential for miniaturization and inherently safe tissue interaction. However, independent actuation of multiple manipulators within the same confined workspace is limited by undesired simultaneous actuation and manipulator–manipulator interactions. Herein, for the first time, approaches for the independent magnetic actuation of two magnetic continuum manipulators within the same confined workspace are proposed. A novel modular magnetic soft robot segment design is proposed with modified geometry to provide preferential bending planes and high angles of deflection. This design is integrated into two dual‐segment magnetic manipulators which, when arranged in parallel, can deliver independent bending in two planes of motion. Two distinct independent control strategies are proposed, based on orthogonal manipulator magnetization profiles and local field gradient control, respectively. Each dual‐manipulator configuration is characterized over a sequence of applied magnetic fields and gradients, induced via a dual robotically controlled external permanent magnet system. Manipulator independence, bending range of motion, and twisting behaviors are evaluated as a function of control strategy and manipulator separation distance. To demonstrate the system's potential in clinical scenarios, a dual‐manipulator configuration is adapted to carry an endoscopic camera and optic fiber, respectively. The resultant bimanual system is deployed in the confined anatomy of a skull‐base phantom to simulate minimally invasive ablation of a pituitary adenoma. Independent motion of the camera and tool within the confined workspace demonstrate the potential for an independent magnetic tool manipulation for surgical applications.

Closed Loop Static Control of Multi-Magnet Soft Continuum Robots

This paper discusses a novel static control approach applied to magnetic soft continuum robots (MSCRs). Our aim is to demonstrate the control of a multi-magnet soft continuum robot (SCR) in 3D. The proposed controller, based on a simplified yet accurate model of the robot, has a high update rate and is capable of real-time shape control. For the actuation of the MSCR, we employ the dual external permanent magnet (dEPM) platform and we sense the shape via fiber Bragg grating (FBG). The employed actuation system and sensing technique makes the proposed approach directly applicable to the medical context. We demonstrate that the proposed controller, running at approximately 300 Hz, is capable of shape tracking with a mean error of 8.5% and maximum error of 35.2% . We experimentally show that the static controller is 25.9% more accurate than a standard PID controller in shape tracking and is able to reduce the maximum error by 59.2%.

Precise angle estimation of capsule robot in ultrasound using heatmap guided two-stage network

PurposeA capsule robot can be controlled inside gastrointestinal (GI) tract by an external permanent magnet outside of human body for finishing non-invasive diagnosis and treatment. Locomotion control of capsule robot relies on the precise angle feedback that can be achieved by ultrasound imaging. However, ultrasound-based angle estimation of capsule robot is interfered by gastric wall tissue and the mixture of air, water, and digestive matter existing in the stomach. MethodsTo tackle these issues, we introduce a heatmap guided two-stage network to detect the position and estimate the angle of the capsule robot in ultrasound images. Specifically, this network proposes the probability distribution module and skeleton extraction-based angle calculation to obtain accurate capsule robot position and angle estimation. ResultsExtensive experiments were finished on the ultrasound image dataset of capsule robot within porcine stomach. Empirical results showed that our method obtained small position center error of 0.48 mm and high angle estimation accuracy of 96.32%. ConclusionOur method can provide precise angle feedback for locomotion control of capsule robot.