Linear accelerometer with improved magnetic rebalance system
First Claim
1. In acceleration responsive apparatus of the type including magnet means for producing a magnetic field in which is located a coil forming at least a portion of a sensing mass suspended for movement along an input axis fixed relative to the magnet means, a servo system for supplying current to the coil to maintain the sensing mass in a predetermined position along the input axis and pickoff means for supplying a signal indicative of displacement of the sensing mass from the predetermined position, improved force rebalance means for minimizing errors resulting from current in the coil, comprising:
- a permanent magnet aligned with the input axis;
a magnetically permeable sleeve concentric with said permanent magnet and substantially coextensive therewith along the input axis, said permanent magnet and said sleeve cooperating to define a first annular gap containing a substantially radial inwardly directed magnetic field and a second annular gap containing a substantially radial outwardly directed magnetic field;
a tubular bobbin carrying first and second circumferential coils wound in opposite directions and connected in series;
first and second torsion hinge means respectively located along first and second parallel hinge axes perpendicular to the input axis on opposite sides thereof, said first torsion hinge means being fixed relative to said permanent magnet and said second torsion hinge means being fixed relative to said tubular bobbin;
first intermediate arm means joining said first and second torsion hinge means;
third and fourth torsion hinge means respectively located along third and fourth parallel hinge axes on opposite sides of the input axis and parallel with the first and second hinge axes, said third torsion hinge means being fixed relative to said permanent magnet means and said fourth torsion hinge means being fixed relative to said tubular bobbin;
second intermediate arm means joining said third and fourth torsion hinge means, whereby said tubular bobbin is constrained from movement transverse to the input axis;
a servo system for producing a positioning current; and
conductor means, including said first and second torsion hinge means and said first intermediate arm means, for carrying the positioning current to the first and second coils, the positioning current having no net effect on the magnetic flux in the first and second gaps because of the oppositely directed magnetic fluxes produced by current in the first and second coils.
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Abstract
Linear acceleration responsive apparatus is disclosed wherein a sensing mass or bobbin is suspended so that a pair of series connected, oppositely wound circumferential coils thereon are positioned in oppositely directed radial magnetic fields produced by permanent magnet means. The bobbin is supported by hinge assemblies which also serve as flex leads and variable capacitance position pickoff means. A rebalance current is supplied to the coils by a servo amplifier in response to the pickoff signal. The magnetic flux components resulting from the rebalance current are equal and oppositely directed, thereby precluding any effect on the radial magnetic fields.
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Citations
20 Claims
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1. In acceleration responsive apparatus of the type including magnet means for producing a magnetic field in which is located a coil forming at least a portion of a sensing mass suspended for movement along an input axis fixed relative to the magnet means, a servo system for supplying current to the coil to maintain the sensing mass in a predetermined position along the input axis and pickoff means for supplying a signal indicative of displacement of the sensing mass from the predetermined position, improved force rebalance means for minimizing errors resulting from current in the coil, comprising:
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a permanent magnet aligned with the input axis; a magnetically permeable sleeve concentric with said permanent magnet and substantially coextensive therewith along the input axis, said permanent magnet and said sleeve cooperating to define a first annular gap containing a substantially radial inwardly directed magnetic field and a second annular gap containing a substantially radial outwardly directed magnetic field; a tubular bobbin carrying first and second circumferential coils wound in opposite directions and connected in series; first and second torsion hinge means respectively located along first and second parallel hinge axes perpendicular to the input axis on opposite sides thereof, said first torsion hinge means being fixed relative to said permanent magnet and said second torsion hinge means being fixed relative to said tubular bobbin; first intermediate arm means joining said first and second torsion hinge means; third and fourth torsion hinge means respectively located along third and fourth parallel hinge axes on opposite sides of the input axis and parallel with the first and second hinge axes, said third torsion hinge means being fixed relative to said permanent magnet means and said fourth torsion hinge means being fixed relative to said tubular bobbin; second intermediate arm means joining said third and fourth torsion hinge means, whereby said tubular bobbin is constrained from movement transverse to the input axis; a servo system for producing a positioning current; and conductor means, including said first and second torsion hinge means and said first intermediate arm means, for carrying the positioning current to the first and second coils, the positioning current having no net effect on the magnetic flux in the first and second gaps because of the oppositely directed magnetic fluxes produced by current in the first and second coils. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An accelerometer with improved force rebalance means for sensing acceleration along an input axis, comprising:
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a housing; permanent magnet means mounted in said housing for producing a pair of oppositely directed radial magnetic fields in separated annular regions centered about and perpendicular to the input axis; a bobbin having a pair of series connected oppositely wound circumferential coils centered on parallel planes having substantially the same separation as the annular regions of magnetic field produced by said permanent magnetic means; a first disk separated by arcuate slits into outer, intermediate and inner rings, and further separated into two symmetrical portions, each portion of the outer ring being joined with the adjacent portion of the intermediate ring by a first torsion member aligned with a first hinge axis perpendicular to the input axis, each portion of the intermediate ring being joined with the adjacent portion of the inner ring by means of a second torsion member aligned with a second hinge axis parallel to the first hinge axis and on the opposite side of the input axis therefrom, the first and second hinge axes lying in a first plane perpendicular to the input axis; a second disk separated by arcuate slits into outer, intermediate and inner rings, and further split into two symmetrical portions, each portion of the outer ring being joined with the adjacent portion of the intermediate ring by a third torsion member aligned with a third hinge axis parallel to the first hinge axis and lying in a second plane parallel to and spaced from the first plane, each portion of the intermediate ring being joined with the adjacent portion of the inner ring by a fourth torsion member aligned with a fourth hinge axis lying in the second plane, parallel to the third hinge axis and on the opposite side of the input axis therefrom; clamping means for connecting said first disk between said housing and said bobbin at one end thereof and for connecting said second disk between said housing and said bobbin at the other end thereof so that said bobbin is centered about the input axis and the coils on the bobbin are positioned in the annular regions of magnetic field, said first and second disks permitting movement of said bobbin along the input axis; pickoff means for producing a position signal indicative of displacement of said bobbin from a predetermined position within said housing; servo amplifier means for producing a rebalance current in response to the position signal; and electrical conductor means including portions of said first disk for supplying the rebalance current to the coils of said bobbin, whereby said bobbin is maintained at the predetermined position. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification