Magnetofluidic accelerometer with capacitive sensing of inertial body position
View Patent ↗An accelerometer includes an inertial body; a magnetized fluid holding the inertial body in suspension; and a plurality of capacitive elements, each forming a capacitor with the inertial body. A displacement of the inertial body produces a change of capacitance of the capacitive elements that is indicative of acceleration. The capacitive elements include at least two capacitive elements per side of the accelerometer. A housing encloses the inertial body and the magnetized fluid, and the plurality of capacitive elements are mounted on the housing. The housing can be cylindrical shaped, rectangular shaped and tetrahedral-shaped. The inertial body can include a disk-shaped magnet, an annular-shaped magnet, or be non-magnetic, or be weakly magnetic. The acceleration can be linear acceleration, angular acceleration, or three components of angular acceleration and three components of linear acceleration. A plurality of magnets magnetize the magnetic fluid.
1. A method of measuring acceleration comprising:
suspending an inertial body using a magnetized magnetic fluid, wherein the inertial body is disk-shaped and includes two electrodes that cover substantially the entire upper and lower surfaces of the disk respectively, and additional electrodes on a curved side surface of the disk that have the shape of a curved surface,
wherein the magnetic fluid is magnetized using a plurality of magnets oriented generally along an axis of symmetry of the inertial body;
measuring a change in capacitance generated by displacement of the inertial body due to acceleration; and
calculating the acceleration based on the capacitive voltage change between the two electrodes and the additional electrodes, and external electrodes.
2. The method of claim 1 , wherein the calculating step calculates linear acceleration.
3. The method of claim 1 , wherein the calculating step calculates angular acceleration.
4. The method of claim 1 , wherein the calculating step calculates three components of angular acceleration and three components of linear acceleration.
5. The method of claim 1 , further comprising driving current through a plurality of magnets for generating a magnetic field for magnetizing the magnetic fluid.
6. The method of claim 1 , wherein the inertial body is non-magnetic.
7. The method of claim 1 , wherein the inertial body is weakly magnetic.
8. The method of claim 1 , wherein the two electrodes and the additional electrodes are formed by a conductive coating on portions of a surface of the inertial body.
9. The method of claim 1 , wherein the inertial body is annular shaped.
10. A method of measuring acceleration comprising:
suspending a non-magnetic object using a fluid, wherein the non-magnetic object is disk-shaped and includes two electrodes that cover substantially the entire upper and lower surfaces of the non-magnetic object respectively, and additional electrodes on a curved side surface of the non-magnetic object that have the shape of a curved surface;
generating a magnetic field within the fluid using a plurality of magnets oriented generally along an axis of symmetry of the non-magnetic object;
detecting a capacitance change between the two electrodes and the additional electrodes and external electrodes due to a change in position of the object as a result of acceleration; and
calculating the acceleration as a function of the control of the magnetic field.
11. An accelerometer comprising:
an inertial body that is disk-shaped and includes two electrodes that cover substantially the entire upper and lower surfaces of the disk respectively, and additional electrodes on a curved side surface of the disk that have the shape of a curved surface;
a magnetized fluid holding the inertial body in suspension, wherein the fluid is magnetized using a plurality of magnets oriented generally along an axis of symmetry of the inertial body; and
a plurality of external electrodes, each forming a capacitor with the electrodes of the inertial body,
wherein a displacement of the inertial body produces a change in capacitance of the capacitors, the change being indicative of acceleration.
12. The accelerometer of claim 11 , wherein the plurality of capacitors comprises at least three capacitive elements per side of the accelerometer.
13. The accelerometer of claim 11 , further comprising a housing enclosing the inertial body and the magnetized fluid, wherein the plurality of external electrodes are mounted on the housing.
14. The accelerometer of claim 13 , wherein the housing is any of cylindrical shaped, rectangular shaped and tetrahedral-shaped.
15. The accelerometer of claim 11 , wherein the inertial body comprises a disk-shaped magnet.
16. The accelerometer of claim 11 , wherein the inertial body comprises an annular-shaped magnet.
17. The accelerometer of claim 11 , wherein the acceleration comprises linear acceleration.
18. The accelerometer of claim 11 , wherein the acceleration comprises angular acceleration.
19. The accelerometer of claim 11 , wherein the acceleration comprises three components of angular acceleration and three components of linear acceleration.
20. The accelerometer of claim 11 , wherein the inertial body is non-magnetic.
21. The accelerometer of claim 11 , wherein the inertial body is weakly magnetic.
22. The accelerometer of claim 11 , further comprising a plurality of magnets that magnetize the magnetic fluid.
23. The accelerometer of claim 11 , further comprising a housing enclosing the magnetic fluid and the inertial body, wherein the housing includes a stretchable membrane.
24. The accelerometer of claim 11 , further comprising a housing enclosing the magnetic fluid and the inertial body, wherein the magnetic fluid partially fills the housing.
25. The accelerometer of claim 11 , wherein the inertial body is annular shaped.
26. An accelerometer comprising:
a magnetic inertial body that is disk-shaped and includes conductive coatings that cover substantially the entire upper and lower surfaces of the disk respectively, and additional separate conductive coatings on a curved side surface of the disk that have the shape of a curved surface;
a magnetic fluid in contact with the inertial body, wherein the magnetic fluid is magnetized using a plurality of magnets oriented generally along an axis of symmetry of the inertial body; and
a plurality of external electrodes arranged around the inertial body, each forming a capacitor with the respective conductive coating on the inertial body,
wherein a displacement of the inertial body changes a capacitive reactance of the capacitors, the change being indicative of acceleration.
27. An accelerometer comprising:
a housing incorporating a stretchable membrane;
an inertial body within the housing, the inertial body being disk-shaped and includes conductive coatings that cover substantially the entire upper and lower surfaces of the disk respectively, and additional separate conductive coatings on a curved side surface of the disk that have the shape of a curved surface;
a magnetic fluid in contact with the inertial body, wherein the magnetic fluid is magnetized using a plurality of magnets positioned generally around an axis of symmetry of the inertial body;
a plurality of sensors sensing a change in position of the inertial body due to acceleration, the sensors sensing a change in capacitance of capacitors formed by the conductive coatings and external electrodes.