Micromachined accelerometer

Claim 2

A multi-axis hydrostatic accelerometer, comprising: (a) a substrate having first and second substantially planar outer surfaces; (b) first, second, third, and fourth spaced-apart fluid coupled cavities positioned within said substrate between said first and second outer surfaces; (c) first, second, third, fourth, fifth, sixth, seventh and eighth resilient membranes integrally formed in said substrate, said first, second, third and fourth membranes respectively positioned between said first, second, third and fourth cavities and said first outer surface of said substrate, said third, fourth, fifth and sixth membranes respectively positioned between said first, second, third and fourth cavities and said second outer surface of said substrate; and (d) first, second, third, fourth, fifth, sixth, seventh and eighth pressure sensing means for respectively sensing pressure exerted on said first, second, third, fourth, fifth, sixth, seventh and eighth membranes by displacement of a fluid sealed within said cavities during acceleration of said substrate; (e) wherein said membranes are deflected due to pressure exerted on said membranes by displacement of said fluid during axial acceleration of said substrate, said axial acceleration including translational acceleration and rotational acceleration; (f) wherein said pressure sensing means provide electronic output signals for determining acceleration along at least three independent translational axes and at least two rotational axes.

Claim 3

A multi-axis hydrostatic accelerometer as recited in claim 1, wherein acceleration is determined according to a.sub.x =1/4sk.sub.x,y [(P.sub.1 +P.sub.2 +P.sub.7 +P.sub.8)-(P.sub.3 +P.sub.4 +P.sub.5 +P.sub.6)] a.sub.y =1/4sk.sub.x,y [(P.sub.1 +P.sub.2 +P.sub.3 +P.sub.4)-(P.sub.5 +P.sub.6 +P.sub.7 +P.sub.8)] a.sub.z =1/4sk.sub.z [(P.sub.1 +P.sub.3 +P.sub.5 +P.sub.7)-(P.sub.2 +P.sub.4 +P.sub.6 +P.sub.8)] α.sub.x =1/4sk.sub.z [(P.sub.1 +P.sub.3 +P.sub.6 +P.sub.8)-(P.sub.2 +P.sub.4 +P.sub.5 +P.sub.7)] α.sub.y =1/4sk.sub.z [(P.sub.3 +P.sub.5 +P.sub.2 +P.sub.8)-(P.sub.1 +P.sub.7 +P.sub.4 +P.sub.6)] k.sub.x,y =Lρ k.sub.z =Hρ where a represents translational acceleration along a denoted axis, α represents rotational acceleration around a denoted axis, P 1 , P 2 , P 3 , P 4 , P 5 , P 6 , P 7 , P 8 , are pressure output signals from the respective pressure sensing means, s is the sensitivity of the pressure sensing means, ρ is the density of the fluid, L is the center-to-center distance between cavities, and H is the separation between the membranes bounding a cavity.

Claim 4

A multi-axis hydrostatic accelerometer as recited in claim 1, further comprising pressure relief means for absorbing thermal expansion of said fluid, said pressure relief means integrally formed in said substrate and coupled to said cavities by said fluid.

Claim 5

A multi-axis hydrostatic accelerometer, comprising: (a) a substrate having substantially planar first and second outer surfaces; (b) first, second, third, and fourth spaced-apart cavities positioned within said substrate between said first and second outer surfaces; (c) first, second, third, fourth, fifth, sixth, seventh and eighth resilient membranes integrally formed in said substrate, said first, second, third and fourth membranes respectively positioned between said first, second, third and fourth cavities and said first outer surface of said substrate, said third, fourth, fifth and sixth membranes respectively positioned between said first, second, third and fourth cavities and said second outer surface of said substrate; and (d) a first channel connecting said first and second cavities; (e) a second channel connecting said third and fourth cavities; (f) a fluid sealed within said channels and said cavities wherein said channels and said cavities are coupled by said fluid; and (g) first, second, third, fourth, fifth, sixth, seventh and eighth pressure sensing means for respectively sensing pressure exerted on said first, second, third, fourth, fifth, sixth, seventh and eighth membranes by displacement of said fluid during acceleration of said substrate; (h) wherein said membranes are deflected due to pressure exerted on said membranes by displacement of said fluid during axial acceleration of said substrate, said axial acceleration including translational acceleration and rotational acceleration; (I) wherein said pressure sensing means provide electronic output signals for determining acceleration along at least three independent translational axes and at least two rotational axes.

Claim 6

A multi-axis hydrostatic accelerometer, comprising: (a) a substrate having substantially planar first and second outer surfaces; (b) first, second, third, and fourth spaced-apart cavities positioned within said substrate between said first and second outer surfaces; (c) first, second, third, fourth, fifth, sixth, seventh and eighth resilient membranes integrally formed in said substrate, said first, second, third and fourth membranes respectively positioned between said first, second, third and fourth cavities and said first outer surface of said substrate, said third, fourth, fifth and sixth membranes respectively positioned between said first, second, third and fourth cavities and said second outer surface of said substrate; and (d) a first channel connecting said first and second cavities; (e) a second channel connecting said third and fourth cavities; (f) a fluid sealed within said channels and said cavities wherein said channels and said cavities are coupled by said fluid; and (g) first, second, third, fourth, fifth, sixth, seventh and eighth pressure sensing means for respectively sensing pressure exerted on said first, second, third, fourth, fifth, sixth, seventh and eighth membranes by displacement of said fluid during acceleration of said substrate; (h) wherein said membranes are deflected due to pressure exerted on said membranes by displacement of said fluid during axial acceleration of said substrate, said axial acceleration including translational acceleration and rotational acceleration; (I) wherein said pressure sensing means provide electronic output signals for determining acceleration along at least three independent translational axes and at least two rotational axes.

Claim 7

A multi-axis hydrostatic accelerometer as recited in claim 4, wherein acceleration is determined according to a.sub.x =1/4sk.sub.x,y [(P.sub.1 +P.sub.2 +P.sub.7 +P.sub.8)-(P.sub.3 +P.sub.4 +P.sub.5 +P.sub.6)] a.sub.y =1/4sk.sub.x,y [(P.sub.1 +P.sub.2 +P.sub.3 +P.sub.4)-(P.sub.5 +P.sub.6 +P.sub.7 +P.sub.8)] a.sub.z =1/4sk.sub.z [(P.sub.1 +P.sub.3 +P.sub.5 +P.sub.7)-(P.sub.2 +P.sub.4 +P.sub.6 +P.sub.8)] α.sub.x =1/4sk.sub.z [(P.sub.1 +P.sub.3 +P.sub.6 +P.sub.8)-(P.sub.2 +P.sub.4 +P.sub.5 +P.sub.7)] α.sub.y =1/4sk.sub.z [(P.sub.3 +P.sub.5 +P.sub.2 +P.sub.8)-(P.sub.1 +P.sub.7 +P.sub.4 +P.sub.6)] k.sub.x,y =Lρ k.sub.z =Hρ where a represents translational acceleration along a denoted axis, α represents rotational acceleration around a denoted axis, P 1 , P 2 , P 3 , P 4 , P 5 , P 6 , P 7 , P 8 , are pressure output signals from the respective pressure sensing means, s is the sensitivity of the pressure sensing means, ρ is the density of the fluid, L is the center-to-center distance between cavities, and H is the separation between the membranes bounding a cavity.

Claim 8

A multi-axis hydrostatic accelerometer as recited in claim 4, further comprising pressure relief means for absorbing thermal expansion of said fluid, said pressure relief means integrally formed in said substrate and coupled to said cavities and said channels by said fluid.

Claim 9

A multi-axis hydrostatic accelerometer as recited in claim 4, further comprising: (a) a third channel connecting said second and third cavities; and (b) a fourth channel connecting said first and fourth cavities.

Claim 10

A multi-axis hydrostatic accelerometer as recited in claim 4, wherein said first and second channels are elongated, wherein said first and second channels have midpoints at which said first and second channels intersect, and wherein said first channel is substantially perpendicular to said second channel.

Claim 11

A multi-axis hydrostatic accelerometer, comprising: (a) a first substantially planar substrate layer; (b) a second substantially planar substrate layer; (c) said first and second substrate layers having opposing bonded inner surfaces, said first and second substrate layers having outer surfaces; (d) first, second, third, and fourth spaced apart cavities extending from the bonded inner surface of the first substrate layer toward the outer surface of said first substrate layer; (e) fifth, sixth, seventh, and eighth spaced apart cavities extending from the bonded inner surface of the second substrate layer toward the outer surface of said second substrate layer; (f) first, second, third and fourth resilient membranes integrally formed in said first substrate layer, said first, second, third and fourth membranes respectively positioned between said first, second, third and fourth cavities and said outer surface of said first substrate layer; (g) fifth, sixth, seventh and eighth resilient membranes integrally formed in said second substrate layer, said fifth, sixth, seventh and eighth membranes respectively positioned between said fifth, sixth, seventh and eighth cavities and said outer surface of said second substrate layer; and (h) a first channel connecting said first, second, fifth and sixth cavities; (i) a second channel connecting said third, fourth, seventh and eighth cavities; (j) a fluid sealed within said first channel and said first, second, fifth and sixth cavities wherein said first channel and said first, second, fifth and sixth cavities are coupled by said fluid; (k) said fluid sealed within said second channel and said third, fourth, seventh and eighth cavities wherein said second channel and said third, fourth, seventh and eighth cavities are fluidly coupled; and (l) first, second, third, fourth, fifth, sixth, seventh and eighth pressure sensing means for respectively sensing pressure exerted on said first, second, third, fourth, fifth, sixth, seventh and eighth membranes by displacement of said fluid during acceleration; (m) wherein said membranes are deflected due to pressure exerted on said membranes by displacement of said fluid during axial acceleration of said substrate, said axial acceleration including translational acceleration and rotational acceleration; (n) wherein said pressure sensing means provide electronic output signals for determining acceleration along at least three independent translational axes and at least two rotational axes.

Claim 12

A multi-axis hydrostatic accelerometer, comprising: (a) a first substantially planar substrate layer; (b) a second substantially planar substrate layer; (c) said first and second substrate layers having opposing bonded inner surfaces, said first and second substrate layers having outer surfaces; (d) first, second, third, and fourth spaced apart cavities extending from the bonded inner surface of the first substrate layer toward the outer surface of said first substrate layer; (e) fifth, sixth, seventh, and eighth spaced apart cavities extending from the bonded inner surface of the second substrate layer toward the outer surface of said second substrate layer; (f) first, second, third and fourth resilient membranes integrally formed in said first substrate layer, said first, second, third and fourth membranes respectively positioned between said first, second, third and fourth cavities and said outer surface of said first substrate layer; (g) fifth, sixth, seventh and eighth resilient membranes integrally formed in said second substrate layer, said fifth, sixth, seventh and eighth membranes respectively positioned between said fifth, sixth, seventh and eighth cavities and said outer surface of said second substrate layer; and (h) a first channel connecting said first, second, fifth and sixth cavities; (i) a second channel connecting said third, fourth, seventh and eighth cavities; (j) a fluid sealed within said first channel and said first, second, fifth and sixth cavities wherein said first channel and said first, second, fifth and sixth cavities are coupled by said fluid; (k) said fluid sealed within said second channel and said third, fourth, seventh and eighth cavities wherein said second channel and said third, fourth, seventh and eighth cavities are fluidly coupled; and (l) first, second, third, fourth, fifth, sixth, seventh and eighth pressure sensing means for respectively sensing pressure exerted on said first, second, third, fourth, fifth, sixth, seventh and eighth membranes by displacement of said fluid during acceleration; (m) wherein said membranes are deflected due to pressure exerted on said membranes by displacement of said fluid during axial acceleration of said substrate, said axial acceleration including translational acceleration and rotational acceleration; (n) wherein said pressure sensing means provide electronic output signals for determining acceleration along at least three independent translational axes and at least two rotational axes.

Claim 13

A multi-axis hydrostatic accelerometer as recited in claim 9, wherein acceleration is determined according to a.sub.x =1/4sk.sub.x,y [(P.sub.1 +P.sub.2 +P.sub.7 +P.sub.8)-(P.sub.3 +P.sub.4 +P.sub.5 +P.sub.6)] a.sub.y =1/4sk.sub.x,y [(P.sub.1 +P.sub.2 +P.sub.3 +P.sub.4)-(P.sub.5 +P.sub.6 +P.sub.7 +P.sub.8)] a.sub.z =1/4sk.sub.z [(P.sub.1 +P.sub.3 +P.sub.5 +P.sub.7)-(P.sub.2 +P.sub.4 +P.sub.6 +P.sub.8)] α.sub.x =1/4sk.sub.z [(P.sub.1 +P.sub.3 +P.sub.6 +P.sub.8)-(P.sub.2 +P.sub.4 +P.sub.5 +P.sub.7)] α.sub.y =1/4sk.sub.z [(P.sub.3 +P.sub.5 +P.sub.2 +P.sub.8)-(P.sub.1 +P.sub.7 +P.sub.4 +P.sub.6)] k.sub.x,y =Lρ k.sub.z =Hρ where a represents translational acceleration along a denoted axis, α represents rotational acceleration around a denoted axis, P 1 , P 2 , P 3 , P 4 , P 5 , P 6 , P 7 , P 8 , are pressure output signals from the respective pressure sensing means, s is the sensitivity of the pressure sensing means, ρ is the density of the fluid, L is the center-to-center distance between cavities, and H is the separation between the membranes bounding a cavity.

Claim 14

A multi-axis hydrostatic accelerometer as recited in claim 9, further comprising pressure relief means for absorbing thermal expansion of said fluid, said pressure relief means integrally formed in said substrate and coupled to said cavities and said channels by said fluid.

Claim 15

A multi-axis hydrostatic accelerometer as recited in claim 9, further comprising: (a) a third channel connecting said second, third, sixth and seventh cavities; and (b) a fourth channel connecting said first, fourth, fifth and eighth cavities.

Claim 16

A multi-axis hydrostatic accelerometer as recited in claim 9, wherein said first and second channels are elongated, wherein said first and second channels have midpoints at which said first and second channels intersect, and wherein said first channel is substantially perpendicular to said second channel.