Microelectromechanical strain gauge with frequency detector
First Claim
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1. A microelectromechanical system (MEMS) strain gauge providing measurement of strain of an object, the strain gauge comprising:
- a substrate having a surface attachable to the object;
a longitudinally extending beam;
at least one flexible arm having first and second ends attached to the substrate and having a middle portion supporting the beam above the substrate;
a first actuator connected to the beam to apply a force to the beam;
a detector connected to the beam for detecting a frequency of vibration of the beam to provide a measure of strain of the object; and
an insulating bridge defined in the beam between the first actuator and the detector.
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Abstract
A microelectromechanical system (MEMS) strain gauge includes at least one flexible arm that can be caused to oscillate. Transverse strain on the arm changes the resonant frequency of the arm. A detector communicating with the flexible arm may detect the frequency of oscillation to provide, an indication of the transverse strain of the substrate.
29 Citations
36 Claims
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1. A microelectromechanical system (MEMS) strain gauge providing measurement of strain of an object, the strain gauge comprising:
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a substrate having a surface attachable to the object; a longitudinally extending beam; at least one flexible arm having first and second ends attached to the substrate and having a middle portion supporting the beam above the substrate;
a first actuator connected to the beam to apply a force to the beam;a detector connected to the beam for detecting a frequency of vibration of the beam to provide a measure of strain of the object; and an insulating bridge defined in the beam between the first actuator and the detector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, 19, 20, 21)
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13. A microelectromechanical system (MEMS) strain gauge providing measurement of strain of an object, the strain gauge comprising:
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a substrate having a surface attachable to the object; a longitudinally extending beam; at least one flexible arm having first and second ends attached to the substrate and having a middle portion supporting the beam above the substrate; a first actuator communicating with the beam to apply a force to the beam, the applied force inducing vibration in the beam, the first actuator comprising; a set of movable capacitor plates connected to the beam and a set of stationary capacitor plates in opposition to the movable capacitor plates; and an AC oscillator connected across the movable and stationary capacitor plates and operable to maintain oscillation at a predetermined frequency of the transverse arm; a detector communicating with the beam for detecting a frequency of vibration of the beam to provide a measure of strain of the object; and a microprocessor coupled to the detector to calculate the strain at the arm as a function of the amplitude of motion of the beam as it vibrates at the predetermined frequency.
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14. A microelectromechanical system (MEMS) strain gauge providing measurement of strain of an object, the strain gauge comprising:
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a substrate having a surface attachable to the object; a longitudinally extending beam; at least one flexible arm having first and second ends attached to the substrate and having a middle portion supporting the beam above the substrate; a detector communicating with the beam for detecting a resonant frequency of vibration of the beam to provide a measure of strain of the object; and microprocessor coupled to the detector to calculate the strain at the arm as a function of the resonant frequency of the arm. - View Dependent Claims (15, 16, 17)
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22. A method for sensing the strain of an object using a MEMS strain gauge including a longitudinally extending beam suspended over a substrate by an arm connected at two separated ends to the substrate along a transverse axis, the method comprising the steps of:
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A) attaching the substrate to the object with the transverse axis aligned with a direction of strain measurement in the object so that strain of the object causes strain in the substrate; B) providing a momentary force to the beam with an actuator connected at a first point along the beam, thereby causing the beam to vibrate at a frequency, wherein the frequency of vibration is dependent upon the strain of the substrate and object; C) measuring the frequency of vibration with a detector connected at a second point along the beam, the second point being electrically isolated from the first point; and D) based on the measured frequency of vibration, determining the strain of the object. - View Dependent Claims (23, 24, 25)
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26. A method for sensing the strain of an object using a MEMS strain gauge including a longitudinally extending beam suspended over a substrate by an arm connected at two separated ends to the substrate along a transverse axis, the method comprising the steps of:
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A) attaching the substrate to the object with the transverse axis aligned with a direction of strain measurement in the object so that strain of the object causes strain in the substrate; B) providing a momentary force to the arm, thereby causing the arm to vibrate at a frequency, wherein the frequency of vibration is dependent upon the strain of the substrate and object; C) measuring the frequency of vibration; and D) based on the measured frequency of vibration, determining the strain of the object by adjusting a displacement of the arm to maintain the vibration at a predetermined frequency, and determining the strain based on the amount of displacement.
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27. A microelectromechanical system (MEMS) strain gauge providing measurement of strain of an object, the strain gauge comprising:
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a substrate having a surface attachable to the object; at least one flexible arm having first and second ends attached to the substrate, wherein the arm oscillates in response to a stimulus; a detector communicating with the arm for detecting a resonant frequency of oscillation of the arm; and a microprocessor coupled to the detector to determine a measure of strain of the object as a function of the resonant frequency of the arm; and
wherein the detector comprising a capacitor plate interfacing with the arm. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification