Measurement system of the relative position between two separate structural parts
A measurement system ( 1 ) of the relative position between two structural parts ( 2 a, 2 b ) of a building, that have separated for example following the formation of a crack, comprising a cylindrical permanent magnet ( 3 ) adapted to generate a magnetic field (B) and a sensor ( 5 ), the sensor ( 5 ) being fixed and the magnet ( 3 ) being moveable according to a direction perpendicular to its axis of symmetry (h) so as to vary the direction of the lines of force of the magnetic field B which cross the sensor 5.
1. A measurement system ( 1 ) of the relative position between two separate structural parts ( 2 a , 2 b ), comprising:
a body ( 3 ) adapted to generate a magnetic field (B), said body ( 3 ) being applicable to one of said parts ( 2 a );
at least one sensor ( 5 ) applicable to the other of said parts ( 2 b ), said at least one sensor ( 5 ) being a triaxial Hall-effect sensor, said sensor ( 5 ) and said body ( 3 ) being relatively movable according to a direction perpendicular to the axis of symmetry (h) of the magnetic field (B) so that the direction of the lines of force of the magnetic field (B) that cross the sensor ( 5 ) varies, said sensor ( 5 ) being configured in order to detect three vector components (Bx, By, Bz) of the intensity of the magnetic field (B),
characterised in that the system ( 1 ) further comprises a processing block of said three vector components (Bx, By, Bz) detected by said at least one sensor ( 5 ), said processing block being configured to calculate at least one radial component (Br) of the magnetic field (B) defined as follows:
Br= √{square root over ( Bx 2 +By 2 )}
and to calculate the distance (r) from the axis of symmetry (h) from the formula:
r
=
{
f
1
(
Br
Bz
)
if
Br
Bz
∈
[
0
,
1
]
f
2
(
Br
Bz
)
otherwise
}
wherein f1 and f2 are polynomials whose coefficients can be derived from the fitting of experimental data or potentially obtained through finite element simulations; the measurement system ( 1 ) further comprising a box-like casing ( 6 ) housing said at least one sensor ( 5 ), and a further box-like casing ( 9 ) having a first portion ( 10 ) adapted to be fixed to one of the structural parts ( 2 a ) and a second portion ( 11 ) free and adapted to slide with respect to the box-like casing ( 6 ) housing the sensor ( 5 ).
2. The measurement system ( 1 ) according to claim 1 , wherein said at least one sensor ( 5 ) is fixed and the body ( 3 ) is movable with respect to it.
3. The measurement system ( 1 ) according to claim 2 , wherein said magnet ( 3 ) can be moved according to a direction perpendicular to said axis of symmetry (h), while the sensor ( 5 ) is located on a plane (α 2 ) perpendicular to said axis of symmetry (h) and not passing through the centre (C) of the magnet ( 3 ).
4. The measurement system ( 1 ) according to claim 1 , wherein said magnetic field (B) has cylindrical symmetry.
5. The measurement system ( 1 ) according to claim 1 , wherein said body ( 3 ) is a permanent magnet.
6. The measurement system ( 1 ) according to claim 1 , further comprising a processing block of the three vector components (Bx, By, Bz) detected by said at least one sensor ( 5 ), said processing block being configured to calculate at least one radial component (Br) defined as follows:
Br= √{square root over ( Bx 2 +By 2 )}
and to calculate the relative position from the arctan function
(
Br
Bz
)
.
7. The measurement system ( 1 ) according to claim 1 , wherein said first portion ( 10 ) and said second portion ( 11 ) consist of two arms having a rectilinear development and connected to each other, said second portion ( 11 ) being configured to be inserted and slide within a cavity ( 13 ) afforded in the box-like casing ( 6 ) housing the sensor ( 5 ).
8. The measurement system ( 1 ) according to claim 7 , wherein said second portion ( 11 ) of the further box-like casing ( 9 ) has a first section ( 11 a) substantially having a parallelepiped shape and a second section ( 11 b ) having an undulated progression.
9. The measurement system ( 1 ) according to claim 8 , wherein said second portion ( 11 b ) has a lower thicknes with respect to the thickness of the first section ( 11 a ).
10. The measurement system ( 1 ) according to claim 9 , further comprising a deformation sensor ( 12 ) placed at said second section ( 11 b ) or said first section ( 11 a ).
11. The measurement system ( 1 ) according to claim 1 , wherein said box-like casing ( 6 ) is provided with a magnetic deflector ( 7 ) positioned to cover the sensor ( 5 ) to shield it from undesired magnetic fields.
12. The measurement system ( 1 ) according to claim 1 , wherein said box-like casing ( 6 ) is equipped with a transparent plate ( 8 ) on which a grid is printed for reading the measurement.
13. The measurement system ( 1 ) according to claim 1 , wherein said box-like casing ( 6 ) contains an accelerometer which can read the vibrations to which said casing ( 6 ) is subject.
14. The measurement system ( 1 ) according to claim 13 , wherein said accelerometer is of the triaxial type.