Device and arrangement for measuring load on a test object, in particular a chassis component
The invention relates to a load measurement device ( 12 ) for accurately measuring a load in a test object ( 14 ) such as, in particular, a chassis component, comprising a magnetic field generating device ( 18 ), a first magnetic field detecting device ( 20 ), a second magnetic field detecting device ( 22 ), and a measurement environment parameter acquisition device ( 80 ) for acquiring at least one measurement environment parameter in the test object ( 14 ), wherein an evaluation device ( 42 ) is configured to generate a measurement signal obtained on the basis of outputs of the first and second magnetic field detection devices ( 20, 22 ) in dependence on the at least one measurement environment parameter detected by the measurement environment parameter acquisition device ( 80 ).
1. A load measurement device ( 12 ) for measuring a load in a test object ( 14 ), comprising:
a sensor head;
a magnetic field generating device ( 18 ) for generating a magnetic field in the test object ( 14 ), the magnetic field generating device ( 18 ) comprising a magnetic field generating coil (Lg) arranged on the sensor head and a current source for supplying the magnetic field generating coil (Lg) with a periodically alternating current;
a first magnetic field detecting device ( 20 ) for detecting a first magnetic field parameter which changes on the basis of a load in the test object ( 14 ) and for generating a first magnetic field parameter signal which changes periodically on the basis of the periodically generated magnetic field, said first magnetic field detecting device ( 20 ) comprising at least one first magnetic field sensor ( 26 - 1 ) arranged on the sensor head ( 10 );
a second magnetic field detecting device ( 22 ) for detecting a second magnetic field parameter which changes on the basis of a load in the test object ( 14 ) and for generating a second magnetic field parameter signal which changes periodically on the basis of the periodically generated magnetic field, said second magnetic field detecting device ( 22 ) comprising at least one second magnetic field sensor ( 26 - 2 ) arranged on the sensor head ( 10 );
an evaluation device ( 42 ) for generating a measurement signal from the first and the second magnetic field parameter signal; and
a measurement environment parameter acquisition device ( 80 ) for acquiring at least one measurement environment parameter in the test object ( 14 ),
said evaluation device ( 42 ) being configured to generate the measurement signal corrected based on said at least one measurement environment parameter acquired by the measurement environment parameter acquisition device ( 80 ),
characterized in that the measurement environment parameter acquisition device ( 80 ) comprises:
an acceleration sensor ( 82 ) for detecting an acceleration applied to the sensor head ( 10 ) and/or to the test object ( 14 ).
2. The load measurement device according to claim 1 , characterized in that the evaluation device ( 42 ) is configured to:
detect shocks or dynamic loads from outside on the basis of the acceleration detected by the acceleration sensor ( 82 ) and to correct the measurement signal on the basis of that.
3. The load measurement device according to claim 1 , characterized in that the measurement environment parameter acquisition device ( 80 ) comprises:
at least one magnetic sensor ( 86 ) for detecting a static magnetic field or a magnetic field that changes at a lower frequency compared to the periodically generated magnetic field, and/or
at least one temperature sensor ( 84 ) for detecting the temperature of the test object,
wherein the evaluation device ( 42 ) is configured to:
detect a change in ambient magnetic fields on the basis of a magnetic sensor signal of the magnetic sensor ( 86 ) and to correct the measurement signal on the basis of this change in the ambient magnetic fields; and/or
correct the measurement signal on the basis of the temperature of the test object ( 14 ) measured by the temperature sensor ( 84 ).
4. The load measurement device according to any of the preceding claims , characterized in that a first pair (A 1 , B 1 ) of a first magnetic field sensor ( 26 - 1 ) and second magnetic field sensor ( 26 - 2 ), and a second pair (A 2 , B 2 ) of a second magnetic field sensor ( 26 - 1 ) and a second magnetic field sensor ( 26 - 2 ) are provided, the first and the second magnetic field sensors ( 26 - 1 , 26 - 2 ) being provided in an X-shaped arrangement in such a manner that the first magnetic field sensors ( 26 - 1 ) are opposite each other and the second magnetic field sensors ( 26 - 2 ) are opposite each other, wherein each of the magnetic field sensors ( 26 - 1 , 26 - 2 ) is associated with an analog-digital converter ( 44 a , 44 b , 44 c , 44 d ) so that a first to fourth digital magnetic field detection signal are supplied to the evaluation device ( 42 ), wherein the evaluation device ( 42 ) is configured to produce therefrom a first measurement signal and a different second measurement signal.
5. The load measurement device according to claim 4 , characterized in that the evaluation device ( 42 ) is configured to evaluate the first pair (A 1 , B 1 ) and the second pair (A 2 , B 2 ) separately to produce the first and the second measurement signal.
6. The load measurement device according to claim 5 , characterized in that the evaluation device ( 42 ) is configured to evaluate the first pair by measuring a difference of the signals of its magnetic field sensors ( 26 - 1 , 26 - 2 ) and by measuring the signal of the first magnetic field sensor ( 26 - 1 ) of the first pair and to evaluate the second pair by measuring a difference of the signals of its magnetic field sensors ( 26 - 1 , 26 - 2 ) and by measuring the signal of the first magnetic field sensor ( 26 - 1 ) of the second pair.
7. The load measurement device according to claim 1 , characterized in that the sensor head ( 10 ) comprises a shield ( 60 ) against electromagnetic interference in the environment.
8. A load measurement arrangement ( 16 ), comprising a test object ( 14 ) and the load measurement device ( 12 ) according to claim 1 for non-contact load measurement in the test object ( 14 ).
9. The load measurement arrangement according to claim 8 , characterized in that several sensor heads ( 10 ) are disposed in diametrically opposed positions on the test object and/or annularly around the test object.
10. The load measurement arrangement according to claim 8 or 9 , characterized in that the test object has a cavity at least one measuring area, the at least one sensor head being arranged in said cavity, surrounded by the test object.
11. The load measurement device according to claim 1 , wherein the measurement environment parameter acquisition device ( 80 ) further comprises:
a temperature sensor ( 84 ) for detecting a temperature difference between the test object and the sensor head.
12. The load measurement device according to claim 11 , wherein the evaluation device ( 42 ) is configured to correct the measurement signal on the basis of the temperature difference between the test object ( 14 ) and the sensor head ( 10 ) or a sensor housing measured by the temperature sensor ( 84 ).
13. The load measurement device according to claim 1 , wherein the measurement environment parameter acquisition device ( 80 ) further comprises:
a current sensor ( 88 ) for detecting the amperage of the current flowing in the magnetic field generating coil (Lg), wherein the evaluation unit is configured to detect a change in the inductance of the magnetic field generating coil (Lg) on the basis of a change in the amperage measured by the current sensor ( 88 ) and/or a change in the permeability of the test object ( 14 ) and to correct the measurement signal on the basis of the change in the amperage measured by the current sensor ( 88 );
and/or an inductance sensor ( 90 ) for detecting the inductance of the magnetic field generating coil (Lg).
14. The load measurement device according to claim 13 , characterized in that the evaluation device ( 42 ) is configured to:
correct the measurement signal on the basis of a change in the inductance of the magnetic field generating coil (Lg) measured by the inductance sensor ( 90 ); and/or
detect a change in the permeability of the test object ( 14 ) on the basis of a change in the inductance of the magnetic field generating coil (Lg) measured by the inductance sensor ( 90 ) and to correct the measurement signal on the basis of this change.