T. T. Overboom

Comparison of Position-Independent Contactless Energy Transfer Systems

This paper presents a comparison of position-independent contactless energy transfer systems by means of an inductive coupling, as a solution to overcome moving cables in emerging mechatronic applications with a linear moving load. A 2-D electromagnetic model of the contactless energy transfer system is derived and applied to six different topologies, which have either air-cored coils or a combination of salient or nonsalient magnetic cores. A parametric sweep is performed to obtain an optimal parameter set for each topology, suited for a power transfer of 1 kW with a position-independent mutual inductance between the primary and secondary coils. Comparison among the topologies shows that slotted topologies are less suited for a constant power transfer and that the geometry can be optimized for a mutual inductance variation below 3% along the linear movement.

Overview of Analytical Models for the Design of Linear and Planar Motors

In this paper, an overview of analytical techniques for the modeling of linear and planar permanent-magnet motors is given. These models can be used complementary to finite element analysis for fast evaluations of topologies, but they are indispensable for the design of magnetically levitated planar motors and other coreless multi-degrees of freedom motors, which are applied in (ultra) high-precision applications. The analytical methods describe the magnetic fields based on magnetic surface charges and Fourier series in 2-D and 3-D.

Design and Optimization of a Rotary Actuator for a Two-Degree-of-Freedom

This paper concerns the design and optimization of a rotary actuator of which the rotor is attached to a linear actuator inside a two-degree-of-freedom zφ-module, which is part of a pick-and-place robot. The rotary actuator provides ±180° rotation while the linear actuator offers a z-motion of ±5 mm. In this paper, the optimal combinations of magnet poles and coils are determined for this slotless actuator with concentrated windings. Based on this analysis, the rotary actuator is optimized using a multiphysical framework, which contains coupled electromagnetic, mechanical, and thermal models. Because the rotation angle is limited, both a moving-coil design with a double mechanical clearance and a moving-magnet design with a single mechanical clearance have been investigated and compared. Additionally, the influence of the edge effects of the magnets on the performance of the rotary actuator has been investigated with both 3-D finite-element modeling simulations and measurements.

z\phi

This paper presents a semianalytical modeling framework to evaluate the performance of a contactless energy transfer system which consists of multiple primary windings and a linear moving secondary winding. The modeling framework combines steady-state and electromagnetic analyses and is able to deal with different winding configurations, consisting of combinations of nonmagnetic materials, iron plates, and slotted structures. In this paper, the modeling framework is used to compare the geometrical dimensions of the six different winding configurations under the condition of a constant magnetic coupling. The analysis shows that flat and thin primary windings and a flat and wide secondary winding are favorable for a constant magnetic coupling.

-Module

This paper presents a method for the calculation of the self- and mutual inductance of coils surrounded by air, positioned on top of a ferromagnetic plate and placed in a cavity inside a ferromagnetic plate. The magnetic fields around an array of air-cored coils are obtained by means of the three-dimensional magnetic vector potential using Fourier analysis. The current density distribution of a coil is modeled by four straight bars; three different configurations to position these bars against each other are presented as an alternative to model the round corners of a coil. An error of maximum 5% has been obtained in the analytically calculated flux density distribution compared to the values obtained from 3-D finite element simulations. Self- and mutual inductances are calculated for each current density description and compared with finite element simulations and measurements. A good agreement has been found for coils modeled by four overlapping or four trapezoidal bars.

Modeling Framework for Contactless Energy Transfer Systems for Linear Actuators

In this paper, a semianalytical model for the calculation of the torque produced by an iron-cored linear permanent-magnet motor is presented. The torque is calculated by means of the Maxwell stress tensor, which requires a description of the magnetic flux density distribution. The two-dimensional distribution is obtained from a semianalytical harmonic model, which accounts for the slotting and finite length of the iron yoke. An analytical expression for the thrust and normal force is obtained by evaluating the Maxwell stress tensor over a line through the air gap. For the torque calculation, the Maxwell stress tensor is numerically integrated along a contour that closely follows the structure of the yoke. The resulting torque and forces show good agreement with finite-element (FE) results.

Three-Dimensional Analytical Modeling Technique of Electromagnetic Fields of Air-Cored Coils Surrounded by Different Ferromagnetic Boundaries

A semianalytical model is derived for the description of the three-dimensional magnetic field of an array of air-cored rectangular coils. The model describes the magnetic field with Fourier series and is obtained by solving the Maxwell equations using a combination of the magnetic vector and scalar potential. The model avoids the necessity of finite element analysis and allows three-dimensional analysis between air-cored rectangular coils in contactless energy transfer systems. As an example, the model is used to calculate the magnetic coupling between an array of primary and one secondary air-cored coil.

Semianalytical Calculation of the Torque in a Linear Permanent-Magnet Motor With Finite Yoke Length

A semianalytical model is derived for the description of the three-dimensional magnetic fields, generated by an array of air-cored rectangular coils above a ferromagnetic plate with cavities, or bounded slots, in the xy-plane. The magnetic fields are described with a double Fourier series and are obtained by solving the Maxwell equations using a combination of the magnetic vector and scalar potentials. Mode-matching of the double Fourier series is applied to obtain the description of the magnetic fields inside the cavities. Therefore, the mode-matching technique is extended for two dimensions. The semianalytical model is compared with three-dimensional finite element analysis and a good agreement has been found.

Three-Dimensional Magnetic Field Modeling for Coupling Calculation Between Air-Cored Rectangular Coils

In the paper a novel actuator is presented for a magnetically suspended ceiling actuator. The actuator consists of several stator segments which contain the coils and the magnets. The armature, therefore, has a totally passive design. Because of its salient structure, a translational force can be produced for motion of the armature. The magnets create a passive attraction force for failsafe operation, which can be controlled for magnetically suspending the armature. Decoupling of the attraction and translational force, however, is complex, because they are strongly coupled. Therefore, position and current dependent force models are created based on curve fitting of inductances. It is shown that using these models, decoupling of the attraction and translational force in the ceiling actuator is possible.

Mode-Matching Technique Applied to Three-Dimensional Magnetic Field Modeling

This paper presents the modeling of inductances nearby conducting material. A 3-D magnetic model is derived based on Fourier analysis in which the diffusion equation is incorporated. The model is applied to calculate the mutual inductance in a contactless energy transfer system between four primary coils and a single secondary coil for different positions of the secondary coil. The calculated values are compared with finite element simulations and measurements. A difference of maximum 7% is obtained among the different methods.