Magnetic Control System Research Articles

Control of elongated plasmas in superconductive tokamaks in the absence of in-vessel coils

The roadmap for the commissioning and first operations of superconductive tokamaks envisages the possibility of running discharges with fairly elongated plasmas before the complete installation of the in-vessel components, including vertical stabilization coils, or any other specific sets of coils to be used for the magnetic control of fast transients. In the absence of dedicated actuators, the magnetic control system shall perform the essential fast control actions by using the out-vessel superconductive coils, if needed. These are typically less efficient in reacting to fast transients, due to the shielding effect of the vessel and imply a coupling with other control tasks relying on the same actuators, such as plasma current, position, and shape control. Hence, effective actuator-sharing strategies must be put in place. This paper presents an architecture and a possible control strategy that is able to cope with vertically unstable elongated plasmas subject to fast varying disturbances, in the absence of dedicated in-vessel coils. The architecture exploits a model-based actuator-sharing approach to effectively accomplish the main magnetic control objectives while minimizing the cross-couplings among the various tasks. The effectiveness of the approach is demonstrated by means of nonlinear simulations of realistic JT-60SA scenarios. In particular, an isoflux plasma shape controller is integrated with plasma current control and vertical stabilization. The proposed control approach proves to control vertical displacement events and plasma deformations due to fast variations of poloidal beta with satisfactory performance.

MAGNETIC CONTROL SYSTEM WITH TWO-COMPONENT VIBRATION-INDUCTION MAGNETIC FIELD TRANSDUCER

The features of identifying and evaluating the parameters of surface cracks by the amplitude and phase change of the spectral components of the signals of a magnetic control system with a two-component vibration-induction primary transducer (VIT) are considered. The structure of the magnetic control system and the device of a two-component VIT are given. Spectral diagnostic signs of the signal of measuring information on the normal and tangential control channels during the movement of the VIT over the crack are determined. Estimates of the threshold sensitivity to small cracks, the depth of occurrence of subsurface cracks, and the range of variation of the working gap are given. It is shown that it is possible to obtain approximate estimates of the depth and width of a rectangular surface crack by the lowering gradient method based on statistically constructed regression dependences of depth and width on the amplitude values of the main significant harmonics of the normal and tangential control channels.

A Review of Levitation Control Methods for Low- and Medium-Speed Maglev Systems

Maglev transportation is a highly promising form of transportation for the future, primarily due to its friction-free operation, exceptional comfort, and low risk of derailment. Unlike conventional transportation systems, maglev trains operate with no mechanical contact with the track. Maglev trains achieve levitation and guidance using electromagnetic forces controlled by a magnetic levitation control system. Therefore, the magnetic levitation control system is of utmost importance in maintaining the stable operation performance of a maglev train. However, due to the open-loop instability and strong nonlinearity of the control system, designing an active controller with self-adaptive ability poses a substantial challenge. Moreover, various uncertainties exist, including parameter variations and unknown external disturbances, under different operating conditions. Although several review papers on maglev levitation systems and control methods have been published over the last decade, there has been no comprehensive exploration of their modeling and related control technologies. Meanwhile, many review papers have become outdated and no longer reflect the current state-of-the-art research in the field. Therefore, this article aims to summarize the models and control technologies for maglev levitation systems following the preferred reporting items for systematic reviews and meta-analysis (PRISMA) criteria. The control technologies mainly include linear control methods, nonlinear control methods, and artificial intelligence methods. In addition, the article will discuss maglev control in other scenarios, such as vehicle–guideway vibration control and redundancy and fault-tolerant design. First, the widely used maglev levitation system modeling methods are reviewed, including the modeling assumptions. Second, the principle of the control methods and their control performance in maglev levitation systems are presented. Third, the maglev control methods in other scenarios are discussed. Finally, the key issues pertaining to the future direction of maglev levitation control are discussed.

Anti-Gravity System Based on Magnetic Levitation Technology

This paper presents a design of an anti-gravity system based on magnetic levitation technology. The system utilizes the force generated by magnetic principles to counteract gravity and achieve object suspension and control. The design objective is to achieve portable maglev technology for everyday use. Specific requirements include adjustable speed range, endurance time, effective suspension range, mass, control mode, safety, magnetic field strength, suspension stability, altitude control precision, resistance to strong magnetic field interference, and portability. The system structure includes suspension device, magnetic field generator, sensor, and control system. Control strategies such as PID control, fuzzy control, and sliding mode control can be employed, and signal communication can be achieved through Bluetooth, Wi-Fi, or fiber optic communication. By selecting and designing appropriate control strategies and integrating suspension, magnetic field generator, and sensor components, the anti-gravity system based on magnetic levitation technology can achieve height control and suspension stability.

Comprehensive analysis of the magnetic field closed-loop control system in SERF atomic magnetometer

Benefiting from the capability to measure and suppress magnetic field interferences in situ, the closed-loop magnetometer system has garnered significant attention. In this paper, the low-pass filtering link is analyzed theoretically and experimentally for the first time within the framework of the single-beam spin exchange relaxation free atomic magnetometer system (the object to be controlled). The analysis not only elucidates its impact on the closed-loop system but also establishes optimal operating parameters through a comprehensive consideration of factors such as steady-state error, bandwidth, and other metrics. A comparison and analysis of the direct output signal of the system with the controller output signal reveal the necessity of using the controller output as the closed-loop system’s output, supported by the amplitude and frequency response characteristics of the output signal. The paper introduces evaluation indicators essential for comparing the long-term measurement stability of open- and closed-loop systems, and it explores the correlation between the output signals of the open- and closed-loop systems and the cardio-magnetic input signals. Finally, the calibration methods for multi-channel closed-loop magnetometers are discussed.

Predict the last closed-flux surface evolution without physical simulation

One of the main challenges in developing effective control strategies for the magnetic control system in tokamaks has been the difficulty in obtaining the last closed-flux surface (LCFS) evolution results from control commands. We have developed a data-driven model that combines a predictive model and a surrogate model for physics simulation programs. This model is capable of predicting the LCFS without relying on physical simulation codes. Addressing the data characteristics of LCFS, we have proposed a specialized discretization approach to achieve dimensionality reduction. Furthermore, we have excluding the control references, the model can be seamlessly integrated into the control system, providing real-time LCFS prediction. Following comprehensive testing and multifaceted evaluation, our model has demonstrated highly satisfactory results of 95% or above, meeting practical requirements.

Ultrasensitive detection of the H5N1 nucleic acid fragment by ICP-MS using DNA dendrimer-carried silver nanoparticle labeling.

The importance of avian influenza virus (AIV) detection in clinical diagnosis and prognosis has been deeply recognized. In this study, the ultrasensitive detection of AIV subtype H5N1 was achieved by ICP-MS combined with DNA dendrimer-carried silver nanoparticle (AgNP) labeling. First, a magnetic control system was constructed by anchoring double-strand DNAs (dsDNAs) which contained a complementary sequence of H5N1 and two locked triggers on the surface of magnetic beads (MBs). When H5N1 was present, the two triggers were released and initiated dendrimer hybridization chain reactions which led to the generation of DNA dendrimer-carried AgNPs on the surface of the MBs. Finally, the AgNPs were collected via magnetic separation, digested by nitric acid, and tested using ICP-MS. The signal intensities of 107Ag were positively correlated with the concentrations of H5N1. Notably, the DNA dendrimer assembly contributed to significant signal amplification and good sensitivity with the limit of detection as low as 2.0 × 10-11 mol L-1. Moreover, the method displayed favorable selectivity against mismatched H5N1 and good recoveries in human serum samples. It is a promising analytical tool for the H5N1 virus and other subtypes of AIV, and has potential value in clinical diagnosis and prognosis of infectious diseases.

System integration of magnetic medical microrobots: from design to control.

Magnetic microrobots are ideal for medical applications owing to their deep tissue penetration, precise control, and flexible movement. After decades of development, various magnetic microrobots have been used to achieve medical functions such as targeted delivery, cell manipulation, and minimally invasive surgery. This review introduces the research status and latest progress in the design and control systems of magnetic medical microrobots from a system integration perspective and summarizes the advantages and limitations of the research to provide a reference for developers. Finally, the future development direction of magnetic medical microrobot design and control systems are discussed.

Development of Microrobot with Optical Magnetic Dual Control for Regulation of Gut Microbiota.

Microrobots have emerged as a promising precision therapy approach that has been widely used in minimally invasive treatments, targeted drug delivery, and wound cleansing, and they also offer a potential new method for actively modulating gut microbiota. Here, a double-faced microrobot was designed to carry gut bacteria via covalently immobilizing the antibodies, and a corresponding integrated optical and magnetic dual-driving control system was also developed for precise control of the microrobot. The microrobot utilizes magnetic microsphere as its core, with one side coated in gold, which serves as the optical receptor surface and the interface for bacterial attachment. The specific gut bacterium, S. cerevisiae, was immobilized on the gold-coated side using the corresponding antibodies. The dual-driving control system enables the precise modulation of gut bacteria by synergistically manipulating the microrobots' movement via the optical field and magnetic field. The feasibility of independent and coordinated control using optical fields and magnetic fields was validated through experimental and numerical simulation approaches. This work introduces a novel method for the precise modulation of gut microbiota, providing a new avenue for disease treatments based on gut bacteria.

Simulation and Verification of a Magnetically Controlled System for a Wireless Capsule Robot

Abstract The incidence of digestive system disease is increasing with the development of society, the environmental transition, and changes in people's lifestyles. A magnetically controlled system (MCS) aimed at the examination of the digestive tract based on octupole electromagnets was proposed to manipulate a wireless capsule endoscopy (WCE) with an internal permanent magnet inside. The parameterization was utilized to optimize the magnetic field of the MCS by determining the structure of the electromagnets. Theoretical calculation and numerical simulation were carried out to compare the external magnetic field generated by the electromagnets with the internal magnetic field generated by the WCE. In vitro tests were studied on the experimental platform to evaluate the performance of the MCS, and it was found that the MCS performed well in directing the WCE's movement and causing the WCE to execute the prescribed action. The system, as a preliminary exploration of the magnetic field control system, was supposed to be employed in gastrointestinal examinations in the future.

Real-Time Plasma Magnetic Control System with Equilibrium Reconstruction Algorithm in the Feedback for the Globus-M2 Tokamak

To control the plasma shape during a tokamak discharge, it is necessary to calculate the plasmashape in real-time. The rate requirements for the shape calculations are especially high for tokamaks with asmall radius, such as Globus-M2 (St. Petersburg, Russia). A real-time magnetic plasma control system forthe Globus-M2 tokamak with flux and current distribution identification (FCDI) algorithm for the plasmaequilibrium reconstruction in feedback is presented. The control system contains discrete one-dimensionaland matrix proportional-integral-derivative controllers synthesized by the matrix inequality method usingthe plasma LPV model calculated on experimental data, and carries out the coordinated control of the plasmaposition and shape as well as the compensation for the scattered field of the central solenoid. The FCDI algorithmis improved for the operation in the real-time mode, and makes it possible to reconstruct the plasmashape in 20 μs. The digital control system with a feedback algorithm was simulated on a real-time test bench,consisting of two Speedgoat Performance Real-Time Target Machines (RTTM), and demonstrated the averageTask Execution Time (TET) value in 67 μs.

Analysis of vertical displacement events in tokamaks removing the evolutionary equilibrium assumption

A key parameter for the vertical stabilisation system of future fusion devices like ITER is the maximum allowable vertical displacement which can be recovered by the magnetic control system (Gribov 2015 Nucl. Fusion 55 073021). The computation of this figure of merit is based on MHD evolutionary equilibrium models: the perturbation of the vertical position implicitly considers a perturbation of the external passive currents which guarantees MHD equilibrium. In this paper, we quantify the consequences of considering non-equilibrium perturbations of the vertical position. In this case, one has to specify separately the initial perturbation of the vertical position and of the external currents. We show in particular under which circumstances the evolution of the vertical position, as predicted by the evolutionary equilibrium models, coincides with that obtained considering also plasma inertia.

Current Limit Avoidance Algorithms for DEMO Operation

Tokamaks are the most promising devices to prove the feasibility of energy production using nuclear fusion on Earth which is foreseen as a possible source of energy for the next centuries. In large tokamaks with superconducting poloidal field (PF) coils, the problem of avoiding saturation of the currents is of paramount importance, especially for a reactor such as the European demonstration fusion power plant DEMO. Indeed, reaching the current limits during plasma operation may cause a loss of control of the plasma shape and/or current, leading to a major disruption. Therefore, a current limit avoidance (CLA) system is essential to assure safe operation. Three different algorithms to be implemented within a CLA system are proposed in this paper: two are based on online solutions of constrained optimization problems, while the third one relies on dynamic allocation. The performance assessment for all the proposed solutions is carried out by considering challenging operation scenarios for the DEMO reactor, such as the case where more than one PF current simultaneously saturates during the discharge. An evaluation of the computational burden needed to solve the allocation problem for the various proposed alternatives is also presented, which shows the compliance of the optimization-based approaches with the envisaged deadlines for real-time implementation of the DEMO plasma magnetic control system.

Magnetic Levitation System Prototype Using Proportional-Integral-Derivative Control

Magnetic levitation is a phenomenon of levitation objects by using a magnetic field to defy gravity. Magnetic levitation is an interesting research topic widely used in industry or transportation such as magnetic levitation trains, conveyors, lifts, and many more. In general, magnetic levitation can be realized by regulating the current as a magnetic field source. However, due to the normally unstable power supply source, results in magnetic field instability. Therefore, a magnetic field control system is needed to stabilize the magnetic levitation system. In this study, a magnetic lifting system has been developed using the Proportional-Integral-Derivative (PID) control method and hall effect sensor. The result shows that by using the PID controller, the magnetic object successfully floated stably at the reference point form 1.4 cm to 6.5 cm with an error ± 0.02 cm and overshoot 0.2 cm, if without using PID, oscillations occur with an error rate of ± 0.1 cm and overshoot of 0.6 cm.

Neural Network Trajectory Tracking Control on Electromagnetic Suspension Systems

A new adaptive-like neural control strategy for motion reference trajectory tracking for a nonlinear electromagnetic suspension dynamic system is introduced. Artificial neural networks, differential flatness and sliding modes are strategically integrated in the presented adaptive neural network control design approach. The robustness and efficiency of the magnetic suspension control system on desired smooth position reference profile tracking can be improved in this fashion. A single levitation control parameter is tuned on-line from a neural adaptive perspective by using information of the reference trajectory tracking error signal only. The sliding mode discontinuous control action is approximated by a neural network-based adaptive continuous control function. Control design is firstly developed from theoretical modelling of the nonlinear physical system. Next, dependency on theoretical modelling of the nonlinear dynamic system is substantially reduced by integrating B-spline neural networks and sliding modes in the electromagnetic levitation control technique. On-line accurate estimation of uncertainty, unmeasured external disturbances and uncertain nonlinearities are conveniently evaded. The effective performance of the robust trajectory tracking levitation control approach is depicted for multiple simulation operating scenarios. The capability of active disturbance suppression is furthermore evidenced. The presented B-spline neural network trajectory tracking control design approach based on sliding modes and differential flatness can be extended to other controllable complex uncertain nonlinear dynamic systems where internal and external disturbances represent a relevant issue. Computer simulations and analytical results demonstrate the effective performance of the new adaptive neural control method.

MaRCoS, an open-source electronic control system for low-field MRI

Every magnetic resonance imaging (MRI) device requires an electronic control system that handles pulse sequences and signal detection and processing. Here we provide details on the architecture and performance of MaRCoS, a MAgnetic Resonance COntrol System developed by an open international community of low-field MRI researchers. MaRCoS is inexpensive and can handle cycle-accurate sequences without hard length limitations, rapid bursts of events, and arbitrary waveforms. It has also been readily adapted to meet the requirements of the various academic and private institutions participating in its development. We describe the MaRCoS hardware, firmware and software that enable all of the above, including a Python-based graphical user interface for pulse sequence implementation, data processing and image reconstruction.

Magnetic Energy Losses and Temperature Control System for Giant Magnetostrictive Transducer.

The giant magnetostrictive transducer (GMT) can be widely used in ultra-precision machining in precision-fluid-control fields. The temperature stability of GMT is critical for the reliable generation of output characteristics. This study presents a magnetic-energy-losses method for the GMT working at high frequency, and designs a temperature-stable control system to improve energy transmission and heat dissipation. Based on the loss-separation theory and experimental data, the temperature-rise characteristics of the transducer are analyzed. The temperature rise considers the effects of hysteresis loss, the eddy-current loss, the anomalous loss and the Joule heat. A constitutive relation among losses, frequency and magnetic-flux density is given. The temperature distribution of the transducer can be quickly and accurately calculated, using the constitutive equation. According to the convective heat-transfer and the thermal-compensation method, a temperature-control system is designed. A prototype of the system is then fabricated and tested to verify the feasibility and efficacy of the proposed design methods. The results demonstrate that the output- displacement deviation can be controlled at less than 0.65 μm, and the temperature difference is less than 3 °C.

Magnetic Levitation Actuation and Motion Control System with Active Levitation Mode Based on Force Imbalance

Accurate large-displacement magnetic levitation actuation and its stability remain difficult in non-liquid environments. A magnetic levitation actuation and motion control system with active levitation mode is proposed in this paper. The actuating force of the system is generated by the external magnetic field. A neural network proportion-integration-differentiation (PID) controller is designed for active actuation, and a force imbalance principle is built for the step motion mode. Dual electromagnetic actuators are configured to generate a superimposed magnetic field, ensuring that the electromagnetic force on the ball is more uniform and stable than single actuators. Dual-hall-structure sensors are used to measure displacement, thereby reducing overshoot and ensuring stability whilst motivating the ball. Due to the high adaptability of the neural network to complex systems with nonlinear and ambiguous models, the PID controller composed of neurons has stronger adaptability through tuning the PID controller parameters automatically. Furthermore, the proposed controller can solve the shortcoming that the deviation between the controlled object and the steady-state operating point increases and the tracking performance deteriorates rapidly. The strong robustness and stability in active levitation and motion control is achieved during both ascending and descending processes.

Controllability and observability of discretized satellite magnetic attitude control system

<abstract><p>In this paper, two different discrete schemes of the second-order linear time-varying system represented by the linearized satellite magnetic attitude control motion equation are obtained by Euler method. Then, the controllability and observability conditions of a new discrete second-order linear time-varying system are proposed and the validity of these conditions is further verified by some numerical examples. Next, the theoretical results are applied to investigate the controllability and observability of the discretized satellite magnetic control system. Different periods $ \tau $ are chosen to investigate the effect on the controllability and observability of the resulting discrete system. The corresponding conclusions are obtained.</p></abstract>

DEID-Based Control of Networked Rapid Control Prototyping System: Design and Applications

This article presents a novel networked rapid control prototyping (NRCP) system, which can significantly facilitate the theoretical analysis and product design of networked control systems (NCSs). The NRCP system consists of a PC controller equipped with MATLAB/Simulink software and an embedded target designed with open-source hardware, e.g., Raspberry Pi and STM32. Therefore, it benefits from the following advantages, such as simple structure, low cost, convenient deployment, and robust scalability. In order to verify the effectiveness and superiority of the proposed NRCP, a networked magnetic levitation control system (NMLCS) is developed on the basis of this NRCP system. Furthermore, a discrete-time equivalent-input-disturbance (DEID)-based model predictive control approach is proposed for NMLCS to deal with the common practical issues in NCSs, such as time delay and disturbance. Specifically, the time delay is modeled as delay-induced disturbance (DID), whose influence is effectively estimated and eliminated by the designed controller. Several experimental case studies are performed to verify the effectiveness of the NRCP, the DEID-based control algorithm, and the analytical method of DID.