Microelectromechanical strain gauge with frequency detector
AssigneeRockwell Automation Technologies, Inc.
InventorsPatrick C. Herbert, Richard D. Harris, Frederick M. Discenzo, Michael J. Knieser, Robert J. Kretschmann, Mark A. Lucak, Robert J. Pond, Louis F. Szabo
Life of this patent
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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.
Claims36
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.
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 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.
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 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.
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:
- 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.
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:
- 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.
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;
- 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.
Dependencies are inferred from the claim text.