Air Gap Changes Research Articles

Self-Oscillating Converter Based on Phase Tracking Closed Loop for a Dynamic IPT System

The coupling of converters with resonant networks poses significant challenges for frequency tracking and power control in inductive power transfer (IPT) systems. This paper presents an implementation method that addresses these issues by dividing the system’s operation into two distinct states: self-oscillating and power-injecting. Based on these states, a phase-closed loop is constructed. Within this closed loop, the phase tracking unit detects and tracks frequency drift, while the power regulating unit incorporates an integrator and adopts a control variable to adjust the output power by modifying the duration of the power injecting state. Meanwhile, the oscillating unit operates in the self-oscillating state. Operating in this manner, the system achieves self-oscillation and demonstrates the capability to effectively track and compensate for system variations within a single cycle. A verification prototype has been constructed, and it demonstrates that the converter within it completely decoupled from the resonant network. Experimental results validate that altering the control variable solely affects the duration of the power-injecting state, allowing for independent control of the output power. When the control variable changes from 2.0 V to 3.5 V, the output power changes from 178 W to 519 W while the self-oscillating state remains unchanged. Furthermore, the system accurately tracks frequency changes, even under significant variations in the coupling coefficient or load, without compromising the power injection state. When the air gap changes from 3 cm to 12 cm, the duration of the self-oscillating state changes from 22.1 μs to 26.3 μs, while the power injecting state remains unchanged. This approach exhibits a robust performance, particularly suitable for dynamic IPT systems sensitive to parameter variations.

Ultrafast Nanodrum-on-Chip Pixels.

Environmentally friendly, ultrafast display pixels of micrometer sizes are fabricated with nanometer-thick gold films and Si/SiO2 wafers. The color displayed is due to both the plasmon response of the gold film and the optical interference from the Fabry-Peerot cavity formed by the underlying silicon substrate, the semitransparent gold film and the air gap between them. When an electric potential is applied to the gold film, the electrostatic force induces an attraction between the gold film and the silicon wafer. Due to the flexibility of the film, the size of the air gap changes, resulting in a changing color. By applying different driving signals, we have achieved cyan, magenta, and yellow reflected colors. The maximum switching rate of the pixel is primarily determined by the thickness dependence of the metal drum and its Young's modulus and is typically in the MHz regime.

Maximizing Output Power Using a Magnetic Energy Harvesting System Considering the Relationship Between Harvesting Time and Induced Voltage Due to a Change of Airgap

Maximizing Output Power Using a Magnetic Energy Harvesting System Considering the Relationship Between Harvesting Time and Induced Voltage Due to a Change of Airgap

Analysis, Design, and Validation of a Decoupled Double-Receiver Wireless Power Transfer System With Constant Voltage Outputs for Industrial Power Supplies

Unwanted cross-couplings greatly hinder the development of double-receiver wireless power transfer (WPT) systems. Whenever the air gap changes or misalignment occurs, cross couplings disrupt the system stability. This article investigates a magnetic coupler for a double-receiver WPT system, which dramatically suppresses the unwanted cross-couplings. Two types of undesirable couplings are significantly reduced by using orthometric DD coils and Q-shaped coils. First, the unwanted couplings between receivers can be eliminated, validated by the measured coupling coefficient <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AB</sub> = 0.003. Therefore, two receivers can work independently. Second, the unwanted couplings among the source coil and receivers can be eliminated ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1A</sub> = 0.003 and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1B</sub> = 0.003), resulting in load-independent constant voltage output. Compensation networks can also be designed straightforwardly. In addition, the inverter can achieve zero phase angle, alleviating volt-ampere rating and increasing efficiency. Thanks to the presented structure, this coupler design process is efficient because the decoupling is from the shape rather than turns. Also, it can be easily generalizable to other output voltage or power levels since turns can be changed to meet different charging demands. Validated by a laboratory prototype, experimental results successfully show remarkable agreement with the theoretical analysis, ensuring 72 V load-independent constant output voltages. It also realizes a 90.16% maximum measured overall dc–dc power transfer efficiency with 12 cm air gaps when delivering 518.4 W to two 20 Ω loads.

USE OF T-SHAPED TOOTH IN A DIRECT CURRENT MACHINE WITH A WINDLESS ROTOR

The electric direct current machine with a windingless rotor (DCWR) is significantly different from the classic direct current machine; its magnetic system does not have a common yoke and consists of a number of magnetically loose teeth and grooves open on both sides. The presence of grooves in which there is no bottom creates a number of air gaps, which leads to a decrease in the magnetic conductivity of the magnetic conductor in the transverse direction, which, again, leads to a weakening of the reaction field of the Фa armature and the rejection of additional poles and compensation winding. Therefore, the size of the working air gap can be reduced to the minimum possible value from a technological point of view. According to the structural schemes, the DCWR belongs to the type of induction machines with two stationary windings on the stator and a toothed magnetic conductor of the rotor, in which the magnetic induction in the working air gap changes only in magnitude without changing the sign. Therefore, the rotor in the DCWR is not remagnetized and is made of ordinary structural steel. The inductor type of the magnetic system allows having only one, common for all poles, excitation winding in the DCWR, and the rotor is very similar to the rotor of multi-pole synchronous machines with permanent incorporated magnets. At the same time, DCWR does not have permanent magnets, which allows to significantly reduce the cost of an electric machine. Replacing straight teeth with T-shaped ones allows you to significantly increase the efficiency of the DCWR design by improving its heat dissipation. The results of calculations and modeling of the stationary thermal field presented in the article show that the use of T-shaped teeth allows you to significantly increase the overload capacity of the DCWR or increase its power.

Optimal Control of the Positional Electric Drive and Its Implementation

The article deals with the optimal control of the positional electric drive of the stator element of a segment-type wind turbine. The calculation options charts current in the assumption of the minimum energy consumption and the implementation of line chart current using the phenomenon of capacitor discharge. The analysis of the implementation is expressed in a jump-like change in current and a triangular graph of the speed change. This article deals with small capacity synchronous wind turbine generators with a segment type stator. These units have the possibility of intentionally changing the air gap between the rotor and stator. This allows: (1) Reduce the starting torque on the rotor shaft, which will allow the rotor to pick up at low wind speeds. (2) Equivalent to change of air gap in this case is change of excitation of synchronous generators. Thus, the purpose of the article is to consider a method of excitation of generators in a segmented design, by controlling the gap with the electric drive, while providing control should be carried out with minimal losses.

Application of New Co-simulation in System Simulation of Doubly-fed Induction Generator

This paper proposes a doubly-fed induction generator (DFIG) model built on three simulation platforms: Maxwell, Simplorer and Simulink. It can solve the overall modeling problem of the DFIG system effectively. In this paper, the generator physical simulation model (rotating shaft, rotor, stator and winding) are first established in Maxwell. Then, the internal (stator/rotor winding) and external circuit of DFIG are connected in Simplorer. The external circuit includes converter (generator side and grid side), filter, transformer and grid. Moreover, both the generator-side converter and the grid-side converter are controlled by Simulink. Finally, the simulation calculation study on the 5.5kW DFIG are carried out to validate the theoretical analysis. It is shown that SAGE causes distortion of the air gap magnetic field, the magnetic flux density (MFD) is inversely related to air gap changes. In addition, with the increase of SAGE, the curve of electromagnetic torque (EMT) moves down and rotor unbalanced magnetic pull (UMP) fluctuations become more obvious. The model can simulate the DFIG system accurately and effectively. And the simulation results are consistent with the theoretical derivation, which proves the validity of the model. This provides an effective method for the whole simulation and fault analysis of DFIG system.

A simulation of an electric machine considering the coupling of rotor‐ and electrodynamics

AbstractIn this paper, a method is presented to determine the vibrational behavior of an electric motor and the associated structure. Therefore, a holistic simulation approach is used, which takes into account the mutual influence of structural mechanics and electrodynamics. For this purpose, a multi body simulation (MBS) is extended so that electromagnetic loads can be considered, which are calculated by using the finite element method (FEM). In electric machines an undisturbed and constant magnetic field is of great importance. Even small variations of the air gap lead to changes in the magnetic field compared to the ideal geometry, which cause a change in the resulting torque and vibration excitation. Especially local and global asymmetric air gap changes due to load‐ and operation‐dependent deformations of the stator and rotor are problematic. Such deformations result on the one hand from the electromagnetically excited structural vibrations and on the other hand from the rotordynamic loads. For these reasons, it is necessary to consider the electro‐ and structural‐dynamic effects together. The developed method is presented on a simple generic motor to show the influence of the coupling.

Dynamic Modeling and Analysis of Demagnetizing Rotor of Permanent Magnet Synchronous Motor

This study performs a dynamic modeling and analysis of the axial uniform demagnetization rotor of a motor to investigate the demagnetization peculiar for permanent magnet synchronous motor (PMSM). First, the air‐gap change in the motor is analyzed by constructing a dual coordinate system of stator and rotor, and the unbalanced magnetic pull (UMP) model under uniform demagnetization and eccentricity is constructed. Second, combined with the UMP and the self‐gravity, a dynamic model of the rotor under a uniform demagnetization and eccentricity is established. Lastly, the accuracy of the mathematical model of UMP under uniform demagnetization and eccentricity is confirmed by the mutual corroboration of Maxwell simulation and MATLAB calculation; and based on the dynamics model, the dynamic characteristics of the rotor system under different degrees of uniform demagnetization are studied. This study provides a theoretical basis for the accurate demagnetization fault diagnosis and vibration control of PMSMs in the future.

PIDNN control for Vernier-gimballing magnetically suspended flywheel under nonlinear change of stiffness and disturbance

Vernier-gimballing magnetically suspended flywheel is often used for attitude control and interference suppression of spacecrafts. Due to the special structure of the conical magnetic bearing, the radial component generated by the axial magnetic force and the change of the magnetic air gap will cause the nonlinearity of stiffness and disturbance. That will lead to not only poor stability of the suspension control system but also unsatisfactory tracking accuracy of the rotor position. To solve the nonlinear problem of the system, this article proposes a proportional–integral–derivative neural network control scheme. First, the rotor model considering the nonlinear variation of disturbance and stiffness parameters is established. Then, the weight of neural network is adjusted by the gradient descent method online to ensure the accurate output of magnetic force. Finally, the convergence analysis is carried out based on the Lyapunov stability theory. Compared with the general proportional–integral–derivative control and the radial basis function neural network control, the simulation results demonstrate that the proposed method has the highest tracking accuracy and excellent performance in improving stability. The experimental results prove the correctness of the theoretical analysis and the validity of the proposed method.

Modeling of active magnetic bearing in rotating payload satellite considering shaft motion coupling

This paper establishes the refined dynamic model of the five degree-of-freedom active magnetic bearing used in the earth-oriented satellite system with an unbalanced rotating payload based on the more refined air gap change model for stator motion. The disturbance effects of the thrust active magnetic bearing and the coupling effects of shaft motion are analyzed by the equivalent stiffness and damping model, especially when the satellite system is in the fine pointing phase. Numerical simulation results are provided to verify the accuracy of the proposed simplified stiffness and damping model, the disturbance term effects on active magnetic bearing, and the significance of the refined magnetic bearing dynamic model for improving the payload working ability in the fine pointing phase.

Design and Implementation of Hybrid Fuzzy Control of a Magnetic Levitation System

In this research paper scientific model of the levitation system based on the magnetic field has been implemented with the help of the fuzzy-logic controller. The behaviour of alluring (maglev) mainly based on the PID-controller being used. Therefore, a controller based on PID has been organized to control efficiently and get the desired performance of the maglev system under study. But, as evident from the literature review, a PID controller has its limitations and is typically undefined in the situation of changing the load because PID controllers have fixed constraints. Due to these limitations, a controller that is based on fuzzy logic has been designed to overcome these problems. By using the fuzzy logic, again has been selected for the PID-controller by using the different values of load and set the reference value to calculate the gain error. Best suited membership functions have been used to fuzzifier the gain parameters. An optimal inference engine has been designed to map inputs to the corresponding outputs. Finally, a de-fuzzifier has been designed to get crisp values which reflect the gain constraints of the designed PID Regulator. This fuzzy controller supervises the conventional PID controller to automatically adjust its parameters to control the maglev system even with varying load and varying air gap changes.

Comparisons of Fuzzy MRAS and PID Controllers for EMS Maglev Train

In this paper, a Magnetic Levitation (MAGLEV) train is designed with a first degree of freedom electromagnetbased totally system that permits to levitate vertically up and down. Fuzzy logic, PID and MRAS controllers are used to improve the Magnetic Levitation train passenger comfort and road handling. A matlab Simulink model is used to compare the performance of the three controllers using step input signals. The stability of the Magnetic Levitation train is analyzed using root locus technique. Controller output response for different time period and change of air gap with different time period is analyzed for the three controllers. Finally the comparative simulation and experimental results demonstrate the effectiveness of the presented fuzzy logic controller.

Comparisons of Fuzzy MRAS and PID Controllers for EMS Maglev Train

In this paper, a Magnetic Levitation (MAGLEV) train is designed with a first degree of freedom electromagnet-based totally system that permits the teach to levitate vertically up and down. Fuzzy logic, PID and Mras controllers are used to improve the Magnetic Levitation train passenger comfort and road handling. A matlab Simulink model is used to compare the performance of the three controllers using step input signals. The stability of the Magnetic Levitation train is analyzed using root locus technique. Controller output response for different time period and change of air gap with different time period is analyzed for the three controllers. Finally the comparative simulation and experimental results demonstrate the effectiveness of the presented fuzzy logic controller. Index Terms: Magnetic Levitation (MAGLEV) train, Fuzzy logic, PID, MRAS DOI: 10.7176/JIEA/10-2-01 Publication date: March 31 st 2020

Design and Modeling of an Integrated Flywheel Magnetic Suspension for Kinetic Energy Storage Systems

The paper presents a novel configuration of an axial hybrid magnetic bearing (AHMB) for the suspension of steel flywheels applied in power-intensive energy storage systems. The combination of a permanent magnet (PM) with excited coil enables one to reduce the power consumption, to limit the system volume, and to apply an effective control in the presence of several types of disturbances. The electromagnetic design of the AHMB parts is carried out by parametric finite element analyses with the purpose to optimize the force performances as well as the winding inductance affecting the electrical supply rating and control capability. Such investigation considers both the temperature dependence of the PM properties and the magnetic saturation effects. The electrical parameters and the force characteristics are then implemented in a control scheme, reproducing the electromechanical behavior of the AHMB-flywheel system. The parameter tuning of the controllers is executed by a Matlab/Simulink code, examining the instantaneous profiles of both the air-gap length and the winding ampere-turns. The results of different dynamic tests are presented, evidencing the smooth air-gap changes and the optimized coil utilization, which are desirable features for a safe and efficient flywheel energy storage.

Air-Gap-Insensitive IPT Pad With Ferromagnetic and Conductive Plates

A new conductive-plate-integrated inductive power transfer (IPT) system for automated guided vehicles with little output power variation according to air-gap changes between the transmitter (Tx) and receiver (Rx) is proposed. The inductance change of the ferrite core due to variations in the air gap is nullified by a corresponding change in an aluminum plate. Compared to conventional ferrite IPT systems, self-inductance of the proposed Tx coil is little changed against air-gap variations, which results in robust resonant frequency and output voltage. The self-inductance was experimentally verified to remain within 0.45% even when the air gap changes by fivefold from 10 to 50 mm. The output power variation became a twelfth of that of the conventional ferrite IPT for air-gap variations of 30 ∼ 50 mm, where the efficiency was found to be 96.0% when the output power was 1 kW.

Load Segment Tracking Control of IPT System Based on Power Efficiency Optimization

In the induction electric energy transmission system applied to fix point charging of vehicles, the mutual inductance change caused by position deviation or air gap change, and the equivalent load change caused by power demand change will make the output power and efficiency fluctuate, thus affecting the output stability of the system. In order to ensure the reliability of the charging process of the system and at the same time have a strong power output capacity, this paper proposes a load segmental tracking control strategy based on the optimal power efficiency. This control strategy adjusts the equivalent load to track different power efficiency indicator curves according to different mutual inductance states of the system and power demand when the vehicle is static charging, so that it can always maintain the optimal power efficiency state according to different charging conditions and improve the system performance. Finally, simulation and experimental verification are carried out under different states of mutual inductance. The results show that this method can achieve the equivalent load segmental tracking under different mutual inductance states, and always maintain the optimal power efficiency output.

Characterization of multilayered structures by swept-frequency eddy current testing

The signals of the electromagnetic non-destructive testing of a multilayered structure are functions of the dimension and the electromagnetic properties of each layer in this structure. The signals of the to-be-characterized layer should be ‘extracted’ from the composite signals. This paper proposes of separating signals of different layers by frequency band, and characterizing the layer of interest by using the correspondent signals. An analytical solution derived in terms of transmission and reflection of electromagnetic waves was used to conduct simulation of swept-frequency eddy current testing of a multilayered structure. A couple of characteristic parameters were extracted from the analysis of the signals and the differences of the signal series in the frequency series. It was found that the thicknesses of the top and lower layers can be determined respectively by using high frequency and low frequency signals. The differences of the signal series in the frequency series are insensitive to the variation of air gap between two conductive layers. The maximum difference of resistance in the frequency series can be used to characterize the lower layer regardless the change of conductivity and air gap.

In-vivo EPID dosimetry for IMRT and VMAT based on through-air predicted portal dose algorithm

We have adapted the methodology of Berry et al. (2012) for Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) treatments at a fixed source to imager distance (SID) based on the manufacturer’s through-air portal dose image prediction algorithm. In order to fix the SID a correction factor was introduced to account for the change in air gap between patient and imager. Commissioning data, collected with multiple field sizes, solid water thicknesses and air gaps, were acquired at 150 cm SID on the Varian aS1200 EPID. The method was verified using six IMRT and seven VMAT plans on up to three different phantoms. The method’s sensitivity and accuracy were investigated by introducing errors. A global 3%/3 mm gamma was used to assess the differences between the predicted and measured portal dose images. The effect of a varying air gap on EPID signal was found to be significant – varying by up to 30% with field size, phantom thickness, and air gap. All IMRT plans passed the 3%/3 mm gamma criteria by more than 95% on the three phantoms. 23 of 24 arcs from the VMAT plans passed the 3%/3 mm gamma criteria by more than 95%. This method was found to be sensitive to a range of potential errors. The presented approach provides fast and accurate in-vivo EPID dosimetry for IMRT and VMAT treatments and can potentially replace many pre-treatment verifications.

Research on Effect Factors of Millinewton Electromagnetic Force for Calibrating Force Source

It’s an important guarantee for calibrating the thrust measuring device of micro thruster to have stable and controllable millinewton force. In this paper, a device generating millinewton force is designed based on current magnetic effect and mutual conversion principle between magnetic field energy and electromagnetic force. According to electrical theory and magnetic theory, the theoretical mathematical models about electromagnetic force over current and electromagnetic force over air gap are established, respectively. When the air gap between electromagnetic coil and magnetic block is 9mm and current ranges from 0mA to 163mA, the material of magnetic block is 2Gr13 and 45 carbon steel, the generated electromagnetic force is 0-34.83mN and 0-34.82mN, respectively, whose nonlinearity and repeatability error are less than 1%. Aiming at two materials of magnetic blocks being 2Gr13 and 45 carbon steel, the generated force values are 1.53-31.81 mN and 1.48-31.35mN when the air gap changes from 17mm to 7mm and the current keeps 110mA, respectively, whose nonlinearity are less than 5% and the repeatability error are less than 1%. The results show that the main influence factors of electromagnetic force are current and air gap, and material has a less influence on electromagnetic force.