Magnetic Control System Research Articles

Analysis and Design of Magnetic Levitation and Mechanical Spring Compound Vibration Isolation Control System

In this paper, the magnetic levitation and mechanical spring compound vibration isolation control system is designed by applying maglev active control on the basis of mechanical vibration isolator. The system can effectively solve the problems of fixed structure parameters and poor environmental adaptability of passive vibration isolators, and can be applied to the anti-vibration protection of precision instruments in complex environments. This paper analyses the mechanism and characteristics of maglev vibration isolation, deduces the dynamic model of the system, discusses the design of the active vibration isolation control strategies, and carries out several simulation experiments of vibration isolation in different environments. The results show that the design scheme of the system is reasonable and feasible.

Plasma magnetic cascade multiloop control system design methodology in a tokamak

The paper treats the methodology of the design and analysis of a tokamak plasma magnetic cascade multiloop control system with the example of the Globus-M spherical tokamak (Ioffe Institute, S-Petersburg, Russia) including a set of new features. The methodology covers: plasma equilibrium reconstruction based on the experimental data, derivation of linear plasma models relative to the reconstructed plasma equilibrium taking into account plasma diagnostics methods and equipment, development of a new original model of a thyristor current inverter as an actuator included in the system feedback, original multivariable cascade multiloop structure analysis by Relative Gain Array/μ-procedures, and design of an H∞, multivariable plasma shape control system with adaptation of the magnetic axis position.

Process of the Positioning Complex Modeling Objects with Elements of Intellectual Analysis

The calculation and results of simulation of the magnetic control system for the spacecraft momentum are presented in the paper. The simulation includes an assessment of the reliability of calculating the Earth’s magnetic field parameters, as well as an assessment of the quality of object stabilization by resetting the total momentum with the aid of the system under review. The outcome of a comparative analysis of resource efficiency and energy efficiency are demonstrated in the implementation of the proposed hardware models of controllers on FPGA. The calculate is performed on the mechatronic system parameters of realistic situation.

Software protection of the maglev transport control system

Background: The article examines the issues of regulation and the development of methodological approaches to ensuring the security of the software system for the management of magnetic-leaving transport at all stages of the life cycle, as well as the development of a tool to detect high-level (logical) software vulnerabilities.
 Aim: Development of a methodology for the creation of an error-free and impact-resistant software for the management system of magnetic-levitational transport.
 Methods: In the development of the methodology, the existing practices of searching for errors and vulnerabilities in software and approaches to the algorithmization of program code were studied.
 Results: During the study, a methodology was developed for creating an error-free and impact-resistant software for the management system of magnetic-levitational transport, which makes it possible to exclude the possibility of errors in the software, which significantly increases the safety of the overall transportation process.
 Conclusion: The application of the developed technique will improve the security of software for magnetic levitation transport control system from destructive external influences

Plasma Control in Tokamaks. Part 2.

Various systems of magnetic control of plasma position, current, and shape are considered in vertically elongated tokamaks including spherical tokamaks being in operation. The systems of Resistive Wall Modes suppression are described. Tokamaks constructions and cross-sections, structural schemes of plasma control systems are given; heed is paid to operating principles of plasma control systems; experimental results of plasma control in tokamaks are given. Various engineering realizations of magnetic plasma control systems in tokamaks are presented.

External resonance magnetic field control system based on the Siemens S7-400 controllers at the T-10 tokamak

A multilevel control system of a tokamak-reactor should provide measurements of the physical and technological plasma parameters in real time under conditions of high radiation fluxs. For the control systems of the ITER tokamak-reactor, it is planned to use automatic control systems based on the Siemens S7 programmable logic controllers (PLCs) which can operate under these conditions. Along with the possibility of multilevel remote control of the equipment, the PLC provides timely responses in emergency situations without human involvement and adaptive control in real time. This article presents results of using the Siemens S7 417-4 controllers for external resonant magnetic field control in the T-10 tokamak in the regimes with increased electromagnetic fields and radiation fluxs in shots with ohmic and additional microwave plasma heating.

Design of Magnetic Bearing Control System Based on Active Disturbance Rejection Theory

At present, most of the magnetic bearing system adopts the classical proportional–integral–derivative (PID) control strategy. However, the external disturbances, system parameter perturbations, and many other uncertain disturbances result in PID controller difficult to achieve high performance. To solve this problem, a linear active disturbance rejection controller (LADRC) based on active disturbance rejection controller (ADRC) theory was designed for magnetic bearing. According to the actual prototype parameters, the simulation model was built in matlab/simulink. The step and sinusoidal disturbances with PID and LADRC control strategies were simulated and compared. Then, the experiments of step and sinusoidal disturbances were performed. When control parameters are consistent, the experiment showed that the rotor displacement fluctuation decreased by 28.6% using the LADRC than PID control under step disturbances and decreased by around 25.8% under sinusoidal disturbances. When the rotor is running at 24,000 r/min and 27,000 r/min, the displacement of rotor is reduced by around 15% and 13.7%, respectively. Rotate the rotor with step disturbances and sinusoidal disturbances. It can also be seen that LADRC has the advantages of fast response time and good anti-interference. The experiments indicate that the LADRC has better anti-interference performance compared with PID controller.

Design and Implementation of the Resonant Magnetic Perturbations Feedback Control System for Tearing Mode Suppression on J-TEXT

Tearing modes (TMs) degrade the performance of tokamak plasma, and can even lead to disruption. Using externally exerted resonant magnetic perturbations (RMPs) to suppress TM is a promising and effective way. In order to suppress the 2/1 TM, 2/1 RMP must be applied in given phase regions to stabilize magnetic island and accelerate island rotation. The RMP feedback control system acquires the multiple-channel poloidalMirnov signal, processes the acquired data and calculates the magnetic island phase in real time, and switches on the RMP power supply when the phase is in the designated region. The feedback control system is based on NI cRIO and developed mainly using LabVIEW field-programmable gate array. The typical 2/1 mode magnetic island on J-TEXT rotates at a frequency from 2 to 10 kHz. To ensure the control precision within 2°, the control period must be within 500 ns. Due to the noisy characteristic of the Mirnov signal, the feedback control system uses a series of error correction methods in real time to obtain accurate phase. Various control strategies have been adopted to exploit the RMP coil and power supply. Observable result is presented in this paper.

Implementation of active magnetic control system for piston centering in labyrinth piston compressor

This paper introduces a kind of active magnetic control system (AMCS) to solve the problem of the eccentric running of the piston in labyrinth piston compressor. Besides, a new control strategy based on three closed-loops of current, speed and displacement is applied to the control system. Firstly, the structure of the labyrinth piston compressor and the typical force condition to the piston are given. According to this, the AMCS that mainly contains the electromagnetic guiding sleeve, the displacement sensor, the piston rod and the control circuit is designed. And the model of the AMCS is built. Hereinto, the model of the electromagnetic coil in the guiding sleeve is nonlinear and a linearization method is proposed. Secondly, the three closed-loops control strategy is modeled and the regulators are designed. And the speed closed-loop is built on a new speed observation method of the least square linear fitting using the displacement data. Finally, simulation and experiments are done to verify the feasibility of the control system. The experimental results are in accordance with the simulated. It shows that the system can implement the precise centering of the piston. And the controller presents good robustness and high control precision.

Plasma Magnetic Control in Tokamak Devices

In tokamak experimental reactors, the magnetic control system is one of the main plasma control systems that is required, together with the density control, since the very beginning, even before first operations. Indeed, the magnetic control drives the current in the external poloidal circuits in order to first achieve the breakdown conditions and, after plasma formation, to track the desired plasma current, shape and position. Furthermore, when the plasma poloidal cross-section is vertically elongated, the magnetic control takes also care of the vertical stabilization of the plasma column, and therefore it is an essential system for operation. This chapter introduces a reference architecture for plasma magnetic control in tokamaks. Given the proposed architecture, the techniques to design all the required control algorithms is also presented. Experimental results obtained on the JET and EAST tokamaks and simulations for machines currently under construction are shown to prove the effectiveness of the proposed architecture and control algorithms.

The dependence of divertor power sharing on magnetic flux balance in near double-null configurations on Alcator C-Mod

Management of power exhaust will be a crucial task for tokamak fusion reactors. Reactor concepts are often proposed with double-null divertors, i.e. having two magnetic separatrices in an up-down symmetric configuration. This arrangement is potentially advantageous since the majority of the tokamak exhaust power tends to flow to the outer pair of divertor legs at large major radius, where the geometry is favorable for spreading the heat over a large surface area and there is more room for advanced divertor configurations. Despite the importance, there have been relatively few studies of divertor power sharing in near double null configurations and no studies at the poloidal magnetic fields and scrape-off layer power widths anticipated for a reactor. Motivated by this need we have undertaken a systematic study on Alcator C-Mod, examining the effect of magnetic flux balance on the power sharing among the four divertor legs in near double-null plasmas. Ohmic L-modes at three values of plasma current and ICRF-heated enhanced D-alpha (EDA) H-modes and I-modes at a single value of plasma current are explored, producing poloidal magnetic fields of 0.42, 0.62 and 0.85 Tesla. For Ohmic L-modes and ICRF-heated EDA H-modes, we find that the point of equal power sharing between upper and lower divertors occurs remarkably close to a balanced double null. Power sharing amongst the outer (upper versus lower) and inner (upper versus lower) pairs of divertors can be described in terms of a logistic function of magnetic flux balance, consistent with heat flux mapping along magnetic field lines to the outer midplane. Power sharing between inner and outer legs is found to follow a Gaussian-like function of magnetic flux balance with non-zero power to the inner divertors at double null. The overall behavior of H-modes operated near double null and for I-modes operating to within one heat flux e-folding of double null are found similar to Ohmic L-modes, with a significant reduction of power on the inner divertor legs. The results are encapsulated in terms of empirically-informed analytic functions of magnetic flux balance. When combined with magnetic equilibrium control system specifications, these relationships can be used to specify the power flux handling requirements for each of the four divertor target plates.

Magnetic Bearing Control System based on PI and PID Controllers

Magnetic Bearing Control System based on PI and PID Controllers

Superconducting magnet control system of the JT-60SA

The JT-60U is being upgraded to a full-superconducting tokamak referred as the JT-60 Super Advanced (JT-60SA) as one of the JA-EU broader approach projects. JT-60SA will use superconducting magnets to confine the plasma and achieve a plasma current with flat top durations of up to 100 seconds. JT-60SA magnets are cooled by a helium refrigerator, whereby the local flow control is done by a “magnet controller”. During cool down of the JT-60SA, the TF winding pack(WP) and the TF case are connected in series. Since the winding packs of the TF coils (TFWP) has rather high pressure loss, part of the helium flow from the refrigerator needs to bypass them and supplies directly the TF cases and support structures. The magnet controller controls the distribution of the flow. During nominal operation, 876g/s helium are supplied to the TFWP, which is too large for TF case. By introducing a bypass valve for TF case, about 0.1 MPa pressure loss can be saved. Finally the magnet controller has to react on off-normal situations for fail safe operation.

Robust H∞ switching MIMO control for a plasma time-varying parameter model with a variable structure in a tokamak

The paper deals with design and simulation of hierarchical multi-loops feedback magnetic plasma control system on the base of experimental data for the operating Globus-M spherical tokamak in line with the special methodology developed. The components of the system are designed to achieve high-performance operation during short pulses of plasma discharges about 200 ms. The plasma equilibrium reconstruction algorithm with regularization in terms of moving filaments without iterations was developed. The LPV plant model was derived from reconstructed plasma equilibriums as a distributed parameter system with time-varying parameters. A switching plasma shape multivariable controller was designed by the H∞ robust loop-shaping approach for magnetic field at X-point and poloidal fluxes on plasma separatrix (isoflux control). The novelty of the plasma shape control system is the application of robust switching control with a controller state vector matching. The feedback control was applied to the whole discharge with the transition from a limiter phase to a diverter phase when the plasma changed its magnetic topology as a controlled structure.

Fundamental study on the magnetic field control method using multiple HTS coils for Magnetic Drug Delivery System

The magnetic drug delivery system (MDDS) is a key technology to reduce the side effects in the medical applications, and the magnetic force control is very important issue in MDDS. In this application, the strength of magnetic field and gradient required to MDDS devices are 54 mT and 5.5 T/m, respectively. We proposed the new magnetic force control system that consists of the multiple racetrack HTS magnets. We can control the magnetic field gradient along the longitudinal direction by the arrangement of the multiple racetrack HTS magnets and operating current of each magnet. When the racetrack HTS magnets were used, the critical current was reduced by the self-magnetic field. Therefore, the shape design of HTS magnet to reduce the magnet field into the surface of HTS tapes was required. Therefore, the electromagnetic analysis based on finite element method (FEM) was carried out to design and optimize the shape of multiple racetrack HTS magnet. We were able to suppress the reduction of critical current by placing the magnetic substance at upper and lower side of the HTS magnets. It was confirmed that obtained maximum values of magnetic field strength and field gradient were 33 mT and 0.18 T/m, respectively.

Magnetically controlled growing rods in the treatment of early-onset scoliosis: a note of caution.

The MAGnetic Expansion Control (MAGEC) system is used increasingly in the management of early-onset scoliosis. Good results have been published, but there have been recent reports identifying implant failures that may be associated with significant metallosis surrounding the implants. This article aims to present the current knowledge regarding the performance of this implant, and the potential implications and strategies that may be employed to identify and limit any problems. We urge surgeons to apply caution to patient and construct selection; engage in prospective patient registration using a spine registry; ensure close clinical monitoring until growth has ceased; and send all explanted MAGEC rods for independent analysis. The MAGEC system may be a good instrumentation system for the treatment of early-onset scoliosis. However, it is innovative and like all new technology, especially when deployed in a paediatric population, robust systems to assess long-term outcome are required to ensure that patient safety is maintained. Cite this article: Bone Joint J 2017;99-B:708-13.

Magnetic Motion Control and Planning of Untethered Soft Grippers using Ultrasound Image Feedback.

Soft miniaturized untethered grippers can be used to manipulate and transport biological material in unstructured and tortuous environments. Previous studies on control of soft miniaturized grippers employed cameras and optical images as a feedback modality. However, the use of cameras might be unsuitable for localizing miniaturized agents that navigate within the human body. In this paper, we demonstrate the wireless magnetic motion control and planning of soft untethered grippers using feedback extracted from B-mode ultrasound images. Results show that our system employing ultrasound images can be used to control the miniaturized grippers with an average tracking error of 0.4±0.13 mm without payload and 0.36±0.05 mm when the agent performs a transportation task with a payload. The proposed ultrasound feedback magnetic control system demonstrates the ability to control miniaturized grippers in situations where visual feedback cannot be provided via cameras.

Control-oriented tools for the design and validation of the JT-60SA magnetic control system

The construction and operation of the JT-60SA tokamak is the main project currently carried out jointly by Japan and the European Union under the Broader Approach agreement. Within the Integrated Project Team, Japanese and European scientists are developing and testing a number of tools to support preliminary studies and future operations of JT-60SA. Within this collaborative framework, European scientists are using a set of assessed modeling tools to design and validate possible solutions for the plasma magnetic control system of JT-60SA.This paper introduces these tools and describes a possible control architecture to be used on the JT-60SA tokamak. The effectiveness of the proposed architecture is shown by means of numerical simulations.

Hierarchical robust systems for magnetic plasma control in tokamaks with adaptation

We consider synthesis and modeling of hierarchical robust magnetic control systems for plasma in tokamaks with adaptation of the magnetic axis' vertical position. The studies were done for ITER (Cadarache, France) and Globus-M (St. Petersburg, Russia) tokamaks. Our original synthesis method ensures an improvement in performance for the shape of the plasma by resolving the contradiction between position and plasma shape via adaptation in a hierarchical system. Numerical modeling of synthesized control systems on multivariable linear models of plasma and nonlinear plasma-physics code DINA that unites basic equations of plasma dynamics in a magnetic field has shown the efficiency of the proposed approach and a possibility to apply it in a physical experiment.

Steering and control of miniaturized untethered soft magnetic grippers with haptic assistance.

Untethered miniature robotics have recently shown promising results in several scenarios at the microscale, such as targeted drug delivery, microassembly, and biopsy procedures. However, the vast majority of these small-scale robots have very limited manipulation capabilities, and none of the steering systems currently available enable humans to intuitively and effectively control dexterous miniaturized robots in a remote environment. In this paper, we present an innovative micro teleoperation system with haptic assistance for the intuitive steering and control of miniaturized self-folding soft magnetic grippers in 2-D space. The soft grippers can be wirelessly positioned using weak magnetic fields and opened/closed by changing their temperature. An image-guided algorithm tracks the position of the controlled miniaturized gripper in the remote environment. A haptic interface provides the human operator with compelling haptic sensations about the interaction between the gripper and the environment, as well as enables the operator to intuitively control the target position and grasping configuration of the gripper. Finally, magnetic and thermal control systems regulate the position and grasping configuration of the gripper. The viability of the proposed approach is demonstrated through two experiments involving 26 human subjects. Providing haptic stimuli elicited statistically significant improvements in the performance of the considered navigation and micromanipulation tasks. Note to Practitioners-The ability to accurately and intuitively control the motion of miniaturized grippers in remote environments can open new exciting possibilities in the fields of minimally-invasive surgery, micromanipulation, biopsy, and drug delivery. This paper presents a micro teleoperation system with haptic assistance through which a clinician can easily control the motion and open/close capability of miniaturized wireless soft grippers. It introduces the underlying autonomous magnetic and thermal control systems, their interconnection with the master haptic interface, and an extensive evaluation in two real-world scenarios: following of a predetermined trajectory, and pick-and-place of a microscopic object.