Vibratory digital integrating accelerometer

An accelerometer transducer for sensing acceleration along an input axis, comprising:

• a base;
• a first spring element;
• a first sheet member having a nominal plane and mounted by the first spring element to the base for reciprocating angular motion about a first axis lying in the plane at a natural frequency of motion, said base and first spring element determining an orientation of the first sheet member orthogonal to the input axis;
• a second member, mounted to the first member by a second spring element for movement responsive to acceleration along the input axis, such movement causing a change of moment of inertia about the first axis, whereby an acceleration along the input axis causes the natural frequency to change by a quantity representative of the acceleration;
• and
• means for sensing said natural frequency.

A planar intertial sensor for manifesting acceleration along an input (Z) axis, comprising a sheet member and associated base member, said base member including means for supporting the peripheral region of said sheet member in a plane perpendicular to said input (Z) axis, said plane including a first (X) reference axis and a second (Y) reference axis, said first and second reference axes being mutually perpendicular and intersecting said input axis at a common point,

• wherein said sheet member encloses a first pair of opposed C-shaped void regions and at least one second pair of opposed C-shaped void regions, the void regions of said first pair being larger that the void regions of said second pair, and said first pair of void regions being disposed symmetrically about said second axis and said common point, and said second pair of void regions being interior to the void regions of said first pair and being disposed symmetrically about axes parallel to said first axis when said sheet member lies in said plane,
• wherein the portions of said sheet member interior to said first pair of void regions are spaced apart from said base member,
• wherein the portion of said sheet member between opposed ends of the first pair of void regions is flexible about said second axis,
• wherein the portion of said sheet member between opposed ends of the second pair of void regions is imbalanced about said first axis such that acceleration along the input axis changes the moment of inertia of the said portion of the sheet member about said second axis, and further including means for sensing changes in the moment of inertia.