Yinxi Jin

Modeling and Analysis of a New Cylindrical Magnetic Levitation Gravity Compensator With Low Stiffness for the 6-DOF Fine Stage

A novel cylindrical magnetic levitation gravity compensator (MLGC) with low-stiffness and vacuum-compatible characteristics is proposed in this paper. This compensator can be used as the out-of-plane electromagnetic actuator for the 6-DOF fine stage in certain high-precision positioning applications, for example, the wafer stage in a lithography machine. Compared with conventional actuators such as the electromagnet and voice coil motor, the heat and the resulting temperature rise that degrade the stage positioning accuracy can be reduced by using passive magnetic gravity compensation. Based on the equivalent current method, the analytical equations for the magnetic field, static levitation force, vertical stiffness, and dynamic levitation force are derived. However, the static levitation force-vertical displacement characteristic from the traditional analytical model is not sufficiently accurate for the low-stiffness applications when compared with the finite-element model. Therefore, the main reason for the model error is analyzed, and an improved semianalytical method based on a single-point magnetostatic field simulation is proposed. This method offers a theoretical basis for the analysis and design of the low-stiffness MLGC.

A Three-Degree-of-Freedom Short-Stroke Lorentz-Force-Driven Planar Motor Using a Halbach Permanent-Magnet Array With Unequal Thickness

This paper presents a three-degree-of-freedom (3-DOF) Lorentz-force-driven planar motor for a nanopositioning system. The short-stroke planar motor consists of three Lorentz-force-driven units equally spaced by 120

Analysis and Design of Hybrid Excitation Linear Eddy Current Brake

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An improved control scheme for single-phase auxiliary resonant snubber inverter

around the mass center. To increase the force and decrease the force variation with horizontal displacement, a Halbach permanent-magnet array with unequal thickness is used. First, the basic structure and 3-DOF kinematics of the planar motor are introduced. Second, the magnetic field and force expressions are derived based on the charge model and the image method. Third, four typical Lorentz-force-driven units are compared in the aspect of magnetic field, force, force density, and force variation within the effective stroke. Fourth, a suitable cooling structure is designed for the planar motor. Finally, a prototype of the planar motor is constructed and tested. The measured values are in good agreement with results from analysis and finite element model.

Modeling and analysis of a novel planar eddy current damper

This paper presents a novel parallel magnetic path hybrid excitation linear eddy current brake. The eddy current brake using parallel magnetic path scheme with the presence of the PMs, whose flux lines in the primary are oppositely directed with respect to the flux lines by the excitation windings, has the effect of mitigating the saturation of the iron in the teeth of the primary. This allows the brake to be fed with more intense currents improving the braking force. The structure and working principle are introduced. The analytical model was found using the equivalent magnetic circuit method and the layer theory approach. The design method of the eddy current brake was studied using the finite element method. Compared with traditional induction motors and synchronous motors, the design method of the eddy current brake has not been proposed. Therefore, in this paper, the design parameters of the hybrid excitation linear eddy current brake were gradually determined by consulting the design method of the linear induction motor and linear synchronous motor, and a design flowchart was proposed. Finally, a prototype of hybrid excitation linear eddy current brake was created and an experimental study of the eddy current brake was conducted.

Modeling and Analysis of Force Characteristics for Hybrid Excitation Linear Eddy Current Brake

The traditional variable-timing control of auxiliary resonant snubber inverter (ARSI) realize natural zero-voltage-switching (ZVS) of main switches in every switching period to reduce the conduction loss. However, this method leads to failure of ZVS in the light load condition. Therefore, this paper proposes an improved control scheme with two modes for single-phase ARSI to achieve ZVS from zero load to full load. In heavy load mode (HLM), half of main switches are turned on at ZVS condition by using the output current to reduce the conduction loss. In light load mode (LLM), all the main switches achieve ZVS with the conduction of resonant branch to solve the problem of the failure of ZVS near zero load current. Besides, the auxiliary switches can operate at zero-current-switching (ZCS) condition. The proposed control scheme was first verified in the simulation and then validated in the experiment with an inverter prototype. The results show that the proposed control scheme can make main switches achieve ZVS from zero load to full load.

Analysis of MOSFETs switching performance in auxiliary resonant snubber inverter

In this paper, a novel 2-DOF permanent magnet planar eddy current damper is proposed, of which the stator is made of a copper plate and the mover is composed of two orthogonal 1-D permanent magnet arrays with a double sided structure. The main objective of the planar eddy current damper is to provide two orthogonal damping forces for dynamic systems like the 2-DOF high precision positioning system. Firstly, the basic structure and the operating principle of the planar damper are introduced. Secondly, the analytical model of the planar damper is established where the magnetic flux density distribution of the permanent magnet arrays is obtained by using the equivalent magnetic charge method and the image method. Then, the analytical expressions of the damping force and damping coefficient are derived. Lastly, to verify the analytical model, the finite element method (FEM) is adopted for calculating the flux density and a planar damper prototype is manufactured and thoroughly tested. The results from FEM and...

Thrust characteristic analysis and test of the synchronous permanent magnet linear motor

In this paper, a novel parallel magnetic path hybrid excitation linear eddy current brake is presented. The parallel magnetic path scheme is adopted in the proposed eddy current brake. Flux lines of permanent magnets are opposite to the ones from the excitation windings, which have the effect of mitigating the saturation of the primary teeth. This allows the brake to be fed with more intense currents improving the braking force. The structure and the working principle are introduced. The analytical model of the hybrid excitation linear eddy current brake is built based on the magnetic circuit method and the layer theory approach. The relationship between the force characteristics and the design parameters are analyzed. The finite element analysis is employed to confirm the validity of the analysis and compare it with the experimental results obtained from the prototype of hybrid excitation linear eddy current brake.

A new inductance measurement method for permanent magnet synchronous linear motor

In auxiliary resonant snubber inverter (ARSI), the main switches work at zero voltage switching (ZVS) condition and the auxiliary switches operate at zero current switching (ZCS) condition. This is different from working in hard-switching inverter. In this paper, the MOSFETs switching behavior in ARSI is analyzed. The model of MOSFETs considering the junction capacitors is built. The zero-voltage turn-on of main MOSFETs and zero-current turn-off of auxiliary MOSFETs eliminate the Miller plateau. Due to the resonant capacitors reducing the voltage rise rate, the Miller effect is attenuated in the turn-off transition period of main switches. The theory was validated in the experiment with an inverter prototype. The results show that effectiveness of the theoretical analysis.

Research on a Low Stiffness Passive Magnetic Levitation Gravity Compensation System with Opposite Stiffness Cancellation

This paper deal with thrust characteristic analysis and test of the synchronous permanent magnet linear motor. Thrust characteristics such as thrust ripples and detent force of the synchronous permanent magnet linear motor are analyzed and compared with simulation results. A platform is established, and these characteristics were tested with the platform. The experiment results are compared with the simulation results and they coincide with each other very well.