Novel Magnetic Sensing Approach with Improved Linearity

Abstract

This paper introduces a novel contactless sensing principle conceived for measuring the rotation angle of a shaft. The sensor is based on a smart combination of low-cost components that can be effectively integrated in a mechanical assembly of a rotary joint. The working principle is based on the relative rotation of a small diametrically magnetized cylindrical or annular magnet and at least one Hall effect sensor. One of the main strengths of the new sensing principle is to be adaptable to any assigned dimensions and encumbrances without typical design limitations given by the use of standard components. A numerical model is developed for predicting the sensor output characteristic on the base of the concept of magnetic charge. Such a model is validated against results from laboratory experiments. The parameters that define the geometry and layout of the sensor are optimized in order to maximize linearity over an assigned angular range of measurement. Two examples of mechatronic systems that employ the new sensing principle are presented in order to show the possibility of obtaining with the new principle a compact/integrated sensor-design.

Analytical Expression of the Magnetic Field Created by a Permanent Magnet With Diametrical Magnetization

“…(2)) took 0.33 seconds, the double integration of the azimuthal component took 0.045 seconds and the double integration of the radial component took 0.24 seconds (Table 4). This can demonstrate that the analytical model derived in this study outperforms the double integration expression [29] in terms of the computational cost but very close in terms of the calculated results in most of the randomly selected points (Tables 5, 6 and 7).…”

“…on the radial, azimuthal and axial directions ( ⃗ i r , ⃗ i α and ⃗ i z are the unit vectors respectively), with the consideration that the volume charge has no contribution to the magnetic field, Eq. (1) can be rewritten in the double integration form as follows [29]:…”

“…This error is demonstrated in this paper under Section 3, Finite Element verification and discussion. Fontana et al [29] presented the double integration expression, which can be used to calculate the magnetic field created by a permanent magnet with diametrical magnetization at any point of interest in 3D space. However, the double integration expression can be solved only numerically that can be time-consuming when high accuracy needs to be achieved.…”

“…Comparison of the azimuthal component of the magnetic field computed by the analytical model derived in this paper and those of double integration form[29]. Comparison of the radial component of the magnetic field computed by the analytical model derived in this paper and those of double integration form[29].…”

“…Computational times. Comparison of the axial component of the magnetic field computed by the analytical model derived in this paper and those of double integration form[29].…”