Magnetic velocity and position sensors
A system includes at least one sensing unit, the sensing unit including a sensing element. The system includes at least one spatial Lorentz filter coupled to the sensing element. The spatial Lorentz filter (SLF) includes an input coupled to the sensing element and an analog to digital converter (ADC) providing a filtered output signal. The sensing unit is connected to a processor configured for determining velocity or position with respect to a magnetic field and/or a geographic position by processing SLF output signals.
1. A system comprising:
at least one sensing unit comprising a sensing element and at least one spatial Lorentz filter (SLF) coupled to the sensing element, the at least one SLF comprising an input and an output, wherein an analog to digital converter (ADC) is connected between the input and the output for providing a digital output signal; and
wherein the at least one sensing unit is connected to a processor configured for determining a velocity or a position with respect to a magnetic field and/or a geographic position by processing the digital output signal, wherein the processor is configured to process the digital output signal by normalizing the digital output signal using a value for a strength of the magnetic field.
2. The system of claim 1 , wherein the at least one sensing unit is of a current-deflection sensing type, wherein the sensing element is connected at a first end to a current source and at a second end to a current sink, wherein the at least one SLF is connected between a first side and a second side of the sensing element for detecting a cross-element potential proportional to a velocity dependent Lorentz force due to coupling of the magnetic field with the sensing element.
3. The system of claim 1 , wherein a potential is induced between a first end and a second end of the sensing element by a Lorentz force, wherein the first end is connected to the at least one SLF and the second end is connected to a ground.
4. The system of claim 3 , further comprising at least one charge retaining switch coupled to the sensing element at the first end and/or the second end.
5. The system of claim 3 , wherein the at least one SLF includes a first SLF and a second SLF, wherein the second end of the first SLF is connected to the second SLF.
6. The system of claim 1 , wherein the at least one SLF comprises a signal conditioner connected between the input and the ADC, wherein the signal conditioner comprises a frequency-selector and/or an amplifier.
7. The system of claim 1 , wherein an orientation and/or a spatial extent is selected to reduce coupling of the at least one SLF with the magnetic field.
8. The system of claim 1 , wherein the at least one SLF includes at least two SLFs, wherein each of the at least two SLFs is electrically grounded.
9. The system of claim 1 , wherein the sensing element is formed of a conductor material or a semiconductor material.
10. The system of claim 1 , wherein the sensing element comprises a disc, a slab, a deposited layer, or a filament geometry.
11. The system of claim 1 , comprising a plurality of non-parallel sensing units comprising an array for measuring the velocity in more than one direction.
12. The system of claim 1 , further comprising a magnetometer and/or a tilt sensor connected to the processor and configured for determining and/or compensating for orientation of the system to Earth's magnetic field and/or to Earth's surface.
13. The system of claim 1 , further comprising a gimbal configured to adjust an orientation of the at least one sensing unit, wherein the gimbal is passive or active.
14. The system of claim 1 , further comprising a position tracking system configured for integrating a measurement of the velocity over time to determine a change in position and updating a previously recorded position with the change in position to determine a current position.
15. The system of claim 1 , further comprising a Global Positioning System (GPS) receiver connected to the processor for detecting GPS spoofing by comparing the position determined by the processor and a GPS position determined by the GPS receiver.
16. The system of claim 1 , wherein the value for the strength of the magnetic field includes a concurrent measure of the Earth's magnetic field.
17. A method comprising:
detecting a sensing element signal induced by a spatial Lorentz force with at least sensing unit, wherein the at least one sensing unit comprises a sensing element and at least one spatial Lorentz filter (SLF) coupled to the sensing element, wherein the at least one SLF comprises an input and an output, wherein an analog to digital converter (ADC) is connected between the input and the output;
providing the sensing element signal to the at least one SLF;
modifying the sensing element signal by digital conversion to a digital SLF output signal using the ADC; and
providing the digital SLF output signal to a processor configured to process the digital SLF output signal to determine a velocity or a position with respect to a magnetic field and/or a geographic position, wherein processing the digital SLF output signal comprises normalizing the digital SLF output signal using a value for a strength of the magnetic field.
18. The method of claim 17 , wherein modifying the sensing element signal comprises signal conditioning prior to the digital conversion.
19. The method of claim 17 , wherein the value for a strength of the magnetic field includes a concurrent measure of the Earth's magnetic field.
20. The method of claim 19 , wherein the normalized velocity signal is further normalized for sensor tilt with respect to a direction of gravity.
21. The method of claim 19 , wherein the position is determined by integrating the normalized velocity signal over time to determine a change in position and adding the change in position to an initial position to determine an updated position.
22. The method of claim 17 , wherein the digital conversion is preceded by signal conditioning comprising amplifying and/or frequency selecting.