RESONANT INERTIAL FORCE GENERATOR HAVING STABLE NATURAL FREQUENCY
A resonant inertial force generator for controlling vibrations of a structure includes a compliant spring comprising a stack of flexures and elastomeric shims in alternating arrangement, a driven inertial mass coupled to the compliant spring to generate a vibration controlling force.
1 . A resonant inertial force generator for controlling vibrations of a structure, comprising:
a compliant spring comprising a stack of flexures and elastomeric shims in alternating arrangement;
an inertial mass coupled to the compliant spring; and
an actuator for moving said inertial mass.
2 . The resonant inertial force generator of claim 1 , wherein said flexures have flexure surfaces adjacent to said elastomeric shims, said elastomeric shims being bonded to said flexure surfaces.
3 . The resonant inertial force generator of claim 1 , wherein the number of flexures in the stack is at least 2.
4 . The resonant inertial force generator of claim 1 , which has a natural frequency with a decay less than 0.1 Hz over 3,000 hours of operation.
5 . The resonant inertial force generator of claim 1 , wherein the actuator is an electromagnetic actuator.
6 . The resonant inertial force generator of claim 1 , wherein said flexures are comprised of composite beam plates.
7 . The resonant inertial force generator of claim 1 , wherein said stack is sandwiched between a pair of end plates.
8 . The resonant inertial force generator of claim 7 , wherein the elastomeric shims at distal ends of the stack are bonded to the end plates.
9 . The resonant inertial actuator of claim 1 , wherein at least one of the elastomeric shims in the stack has a shape factor greater than 10.
10 . A resonant inertial force generator, comprising:
an inertial mass supported by a plurality of flexures; and
a plurality of intermediate elastomeric shims interleaved with said plurality of flexures.
11 . The resonant inertial force generator of claim 10 , wherein said flexures are comprised of composite plate members.
12 . The resonant inertial force generator of claim 11 , wherein said flexures have flexure surfaces adjacent to said intermediate elastomeric shims, said intermediate elastomeric shims being bonded to said flexure surfaces.
13 . The resonant inertial force generator of claim 11 , wherein each of said intermediate elastomeric shims has a shape factor greater than 10.
14 . A compliant spring, comprising:
a plurality of composite flexure plates layered in a stack; and
an elastomeric shim disposed between each adjacent pair of the composite flexure plates.
15 . The compliant spring of claim 14 , wherein the elastomeric shim is bonded to the adjacent pair of the composite flexure plates.
16 . The compliant spring of claim 14 , wherein said elastomeric shim has a shape factor greater than 10.
17 . A method of making an inertial force generator, comprising:
providing an inertial mass;
providing n composite flexures, wherein n is an integer and is greater than 1;
providing at least n+1 elastomeric shims;
interleaving the at least n+1 elastomeric shims with the n composite flexures to form a compliant spring comprising an alternating arrangement of flexures and elastomeric shims;
coupling said inertial mass to the compliant spring; and
coupling to the inertial mass an actuator capable of moving the inertial mass.
18 . A method of making an inertial force generator, comprising:
providing an inertial mass;
providing a plurality composite flexures;
providing a plurality of elastomeric shims;
stacking the composite flexures and elastomeric shims alternately to form a compliant spring, the elastomeric shims being arranged adjacent to load bearing areas of the composite flexures;
coupling said inertial mass to said compliant spring; and
coupling to the inertial mass an actuator capable of moving the inertial mass.
19 . The method of claim 18 , wherein stacking the composite flexures and elastomeric shims alternately to form a compliant spring comprises stacking the composite flexures and elastomeric shims to form a plurality of compliant springs.
20 . The method of claim 18 wherein stacking the composite flexures and elastomeric shims alternately to form a compliant spring comprises.
21 . A method of making an inertial force generator spring, comprising:
providing a plurality of composite flexure plates;
providing an intermediate elastomer;
layering said composite flexure plates with said intermediate elastomer between said composite flexure plates to provide a spring assembly of layered composite flexure plates and intermediate elastomer between adjacent composite flexure plates, with said intermediate elastomer bonded to said composite flexure plates.
22 . A resonant inertial force generator, comprising:
an inertial mass supported by a plurality of composite flexures arranged in a stack; and
compliant means for separating said composite flexures.
23 . A resonant inertial force generator for controlling vibrations, comprising:
an inertial mass on a spring assembly;
a motor for moving said inertial mass on said spring assembly, said spring assembly including at least a first non-elastomeric flexure and at least a first intermediate elastomer, said intermediate elastomer bonded with said first non-elastomeric flexure.
24 . The resonant inertial force generator of claim 23 , wherein said at least a first intermediate elastomer has a shape factor greater than 10.
25 . The resonant inertial force generator of claim 23 , wherein said non-elastomeric flexure is a composite non-elastomeric flexure, said composite non-elastomeric flexure being comprised of a plurality of reinforcing fibers in a cured matrix.
26 . The resonant inertial force generator of claim 23 , wherein said non-elastomeric flexure is a non-metallic composite flexure.
27 . An apparatus for controlling aircraft vibrations, comprising:
an inertial mass on a spring assembly having a natural frequency NF, an electrically driven motor for moving said inertial mass on said spring assembly, said spring assembly including at least a first composite flexure and a means for inhibiting a decay in said natural frequency NF.
28 . An apparatus for controlling aircraft vibrations, comprising:
a driven inertial mass on a spring assembly having a natural frequency NF with the spring assembly including a plurality of nonhomogeneous composite flexures having first ends and distal second ends with a plurality of elastomeric spacers bonded between the composite flexures proximate the first ends and the distal second ends.