Jean-Paul Yonnet

Analytical calculation of permanent magnet couplings

An analytical method adapted to calculating the forces between permanent magnets is developed, and applied to the torque calculation of synchronous couplings. The method is based on the forces exerted between two elementary barshaped magnets. The curvature effect is taken into account by a corrective coefficient, and the yokes by magnetic images. The method is relatively simple and gives accurate results which are very useful for optimization of the coupling shape. >

Stacked structures of passive magnetic bearings

The stiffness of magnetic bearings composed of only two permanent magnet rings is limited. To increase this stiffness, stacked structures are used. Conventional stacking is obtained by placement of the magnetizations in opposition. This article presents another type of stacking with rotating magnetization direction (RMD), which improves the stiffness by about a factor of 2 in comparison with the conventional stack.

Contactless position sensor using magnetic saturation

This paper describes different structures for the realization of a contactless position sensor when restricting to a magnet as the target and an inductance as the sensing element. The principle of measurement is the local saturation of an inductance core by a magnet. A sensor model is explained using Maxwell equations on the magnetic circuit. Some response curves are also presented in order to validate the model. The experimental results obtained on a prototype of linear position sensor are given.

Interaction between ring-shaped permanent magnets with symbolic gradients: application to magnetic bearing system optimization

This paper presents a semi-analytical calculation of the interaction between magnetic bodies with ring shapes. It leads to fast and accurate evaluation of forces and torques but also to the symbolic expression of their gradients. Our method can be used to compute partial derivatives to address optimization needs. It has been implemented into CADES environment in order to be automatically available for end users. A very efficient optimization of a magnetic bearing system is demonstrated.

Analytical Calculation of Magnet Systems: Magnetic Field Created by Charged Triangles and Polyhedra

An analytical method for the calculation of the magnetostatic scalar potential and the magnetic field created by a polyhedron-shaped permanent magnet is presented in this paper. The magnet is supposed to be uniformly magnetized. The magnetization is equivalent to distributions of magnetic charges: it is the coulombian approach. The analytical calculation is made by a surface integration on all the polygons that composes the polyhedron. For each polygonal surface, we have shown that it can be decomposed in a series of right triangles. An analytical solution in the particular case of the right triangle has been developed. By this way, the magnetostatic potential and the magnetic field of any polyhedral-shaped magnet can be analytically calculated.

Coil and Magnet Design for Nuclear Magnetic Resonance in Inhomogeneous Field

High-resolution nuclear magnetic resonance (NMR) spectrometry is possible in nonhomogeneous magnetic fields-such as those in portable equipment-if the static and the radio-frequency (RF) magnetic fields are perpendicular and correlated in the measurement volume. From the easy-axis rotation theorem and the Amperian currents model, it is possible to exactly match two magnetic fields in two-dimensional systems. We derive a basic probe element that fulfills these conditions. Then we present a portable NMR probe design. The static and RF magnetic fields of the probe are matched on a large volume

A design methodology for permanent magnet microbearings

A 2D analytical calculation method for permanent magnet bearings is proposed and used with a novel computer-aided constrained-design methodology. This methodology uses symbolic computation and automatic programming to generate the optimization software, based on an analytical model of the device. The methodology, implemented in experimental software, Pascosma, is applied to miniaturize passive bearings using bonded and thin-film magnets.

A differential magnetic position sensor

This paper presents a new structure of a magnetic sensor. The output signal is proportional to the angular position. The originality of the structure comes from its design that permits the measurement of the sum of two magnetic inductions which is a constant. This allows the output signal to be insensitive to some external parameters such as the temperature.

Optimization of a linear permanent magnet actuator

Abstract The principle of the actuator is the force applied on a magnet located in a gradient of magnetic field. An original force expression has been developed and used to optimize the structure in order to obtain a force which is constant along a given displacement. The penalty method is applied.

The use of local magnetic saturation for position sensor

More and more automotive applications require exact position sensing. Magnetic position sensors are very low-cost products, and operate without mechanical contact in order to obtain very long-life systems with a high reliability. The principle of measurement of our sensor is the local saturation of the inductance core by a permanent magnet.