# US 12,000,740 B2 · Sensor apparatus

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- Number: US 12,000,740 B2
- Document ID: US12000740B2
- Status: Granted
- Kind: B2
- Application number: 17/527,478
- Filed: 2021-11-16
- Published: 2022-05-19
- Granted: 2024-06-04
- Earliest claimed: 2020-11-17
- Assignees: Board of Trustees of Michigan State University
- Applicants: Board of Trustees of Michigan State University
- Inventors: Yunqi Cao; Nelson Sepulveda-Alancastro; Henry D'Souza
- Web page: https://patentgrep.com/patent/US12000740B2

## CPC

- G01L 1/16: using properties of piezoelectric devices
- G01L 1/26: Auxiliary measures taken, or devices used, in connection with the measurement of force, e.g. for preventing influence of transverse components of force, for preventing overload
- G01L 5/0052: {measuring forces due to impact (G01L5/0061, G01L5/14 take precedence; impact testing of structures G01M7/08; impact testing of material G01N3/00)}
- G01M 5/0025: {of elongated objects, e.g. pipes, masts, towers or railways (G01M5/0058 takes precedence)}
- G01M 5/0058: {of elongated objects, e.g. pipes, masts, towers or railways}
- G01N 3/066: {with electrical indicating or recording means}
- G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G)
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A sensor apparatus is provided. Multiple opposite and self-powered sensors are provided in another aspect of the present apparatus. A further aspect employs a sensor apparatus including a first pair of flexible piezoelectric sensors attached to opposite sides of an exterior surface of a workpiece and at least a second pair of flexible piezoelectric sensors attached to opposite sides of the exterior surface of the workpiece. Another aspect of the present apparatus uses pairs of thin film piezoelectric sensors which are configured to detect bending curvature of a workpiece in at least two dimensions by sending voltage output signals from both of the sensors of a first pair and/or both of the sensors of at least a second pair to a controller and/or electrical circuit.

## Claims

### Claim 1

A sensor apparatus comprising:
(a) an elongated workpiece having an exterior sidewall surface;
(b) at least a first pair of flexible piezoelectric sensors attached to opposite sides of the exterior surface of the workpiece, wherein:
each sensor of the first pair of flexible piezoelectric sensors is configured to experience a same type of stress in both direction and magnitude; and
the first pair of flexile piezoelectric sensors being electrically connected to a first electrical terminal;
(c) at least a second pair of flexible piezoelectric sensors attached to opposite sides of the exterior surface of the workpiece, all of the sensors being peripherally spaced apart from each other, wherein:
each of the second pair of flexible piezoelectric sensors is configured to experience a same type of stress in both direction and magnitude; and
the second pair of flexile piezoelectric sensors being electrically connected to a second electrical terminal;
(d) one of the first pair of the sensors being under compressive stress and another of the first pair of the sensors being under tensile stress when the workpiece bends in the first direction;
(e) one of the second pair of the sensors being under compressive stress and another of the second pair of the sensors being under tensile stress when the workpiece bends in the second direction;
(f) the sensors being configured to detect bending curvature of the workpiece in at least two dimensions by sending voltage output signals from both of the sensors of the first pair and/or both of the sensors of the second pair; and
(g) a controller configured to receive the output signals from the sensors and automatically perform (i) determining the direction of the bending of the workpiece, (ii) determining a distance of the bending, (iii) determining structural deformation of the workpiece, and (iv) determining whether any structural damage has occurred to the workpiece.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein each of the sensors is:
longitudinally elongated along a longitudinal length of the workpiece;
a flexible piezoelectric film; and
a thickness of 0.08-2.0 mm; and
wherein one of the pairs of the sensors assists to reduce the undesired noise in the output signals from the other of the pair of the sensors.

### Claim 3 (depends on 1)

The apparatus of claim 1, wherein each of the sensors comprises a sandwich of overlapping layers, including a middle ferroelectret polymeric layer between conductive metallic layers, and the middle layer includes a cellular internal structure with distributed trapped charges.

### Claim 4 (depends on 1)

The apparatus of claim 1, wherein a transverse piezoelectric effect is observed by changing permanent macro-scaled dipole moments of the sensors upon their bending, and the voltage output signals for each of the sensors is linearly related to the bending curvature.

### Claim 5 (depends on 1)

The apparatus of claim 1, wherein the controller obtains information on angular applied pressure, by monitoring the voltage output signals generated by each of the pairs of the sensors and mapping measurements to a calibration curve via the controller which is remotely located from and wirelessly in communication with the pairs of the sensors.

### Claim 6 (depends on 1)

The apparatus of claim 1, wherein the pairs of the sensors operably sense the bending curvature and also a stress type applied to the workpiece.

### Claim 7 (depends on 1)

The apparatus of claim 1, wherein the workpiece is located below ground and the controller is remotely located above the ground.

### Claim 8 (depends on 1)

The apparatus of claim 1, further comprising:
a first unit gain buffer comprising an amplifier and a diode;
a second unit gain buffer;
the first pair of the sensors providing a bending output signal to the first unit gain buffer which provides impedance matching;
the second pair of the sensors providing a bending output signal to the second unit gain buffer;
the buffers passing along the bending output signals to an on-site electronic component which translates the signals to a real time data array; and
an on-site transmitter sending a signal from the on-site electronic component to the controller which is remotely located.

### Claim 9 (depends on 1)

The apparatus of claim 1, further comprising:
a radio frequency identification tag connected to an electrical circuit to which the pairs of the sensors are also connected;
the controller categorizing the sensor output signals as bending direction, angle and/or distance;
the controller determining a voltage modulus and comparing sensed real-time values to pre-stored maximum and minimum threshold values;
when the controller determines that the sensed values exceed the threshold values, the controller sending a notifying output signal to a visual display; and
at least a portion of the electrical circuit being triggered remotely through the tag to the pairs of the sensors.

### Claim 10 (depends on 1)

The apparatus of claim 1, further comprising at least one removable and flexible fastener securing the sensors and the controller to the exterior surface of the workpiece, which including a rotatable human joint, while the workpiece moves, the fastener comprising at least one of: a pressure sensitive adhesive tape, an elongated bandage or an elongated elastic wrap.

### Claim 11

A sensor apparatus comprising:
(a) a workpiece having an exterior sidewall surface;
(b) flexible and self-powered sensors attached to opposite sides of the exterior surface of the workpiece, the sensors being peripherally spaced apart from each other;
(c) one of the sensors being under compressive stress and another of the sensors being under tensile stress when the workpiece bends in a first direction;
(d) an electrical circuit, the sensors being configured to detect a characteristic associated with bending or impact of the workpiece by sending voltage output signals from the sensors to the electrical circuit; and
(e) a controller configured to receive the output signals from the sensors and automatically perform: (i) determining the direction of the bending of the workpiece, (ii) determining a distance of the bending, (iii) determining an impact force, reconstructing a bending curvature based on the characteristic, and (v) determining structural health and/or damage of the workpiece based on the bending curvature.

### Claim 12 (depends on 11)

The apparatus of claim 11, further comprising at least a second pair of flexible and self-powered sensors attached to opposite sides of the exterior surface of the workpiece, and one of the second pair of sensors being under compressive stress and another of the second pair of sensors being under tensile stress when the workpiece bends in a second direction.

### Claim 13 (depends on 11)

The apparatus of claim 11, wherein the sensors are piezoelectric sensors, and a first pair of the sensors assists to reduce undesired noise in output signals from a second pair of the sensors.

### Claim 14 (depends on 11)

The apparatus of claim 11, wherein the sensors are triboelectric sensors.

### Claim 15 (depends on 11)

The apparatus of claim 11, wherein the sensors are ferroelectret sensors.

### Claim 16 (depends on 11)

The apparatus of claim 11, wherein the workpiece includes an elongated structural support.

### Claim 17 (depends on 11)

The apparatus of claim 11, wherein the workpiece includes an elongated and hollow conduit.

### Claim 18 (depends on 11)

The apparatus of claim 11, wherein the characteristic is head or neck impact.

### Claim 19 (depends on 11)

The apparatus of claim 11, wherein the characteristic is associated with movement of a leg or neck joint.

### Claim 20 (depends on 11)

The apparatus of claim 11, further comprising at least one removable and flexible fastener securing the sensors and the controller to the exterior surface of the workpiece while the workpiece moves, the fastener comprising at least one of: a pressure sensitive adhesive tape, an elongated bandage or an elongated elastic wrap.

### Claim 21 (depends on 11)

The apparatus of claim 11, wherein a transverse piezoelectric effect is observed by changing permanent macro-scaled dipole moments of the sensors upon their bending, and the voltage output signals for each of the sensors is linearly related to the bending curvature.

### Claim 22

A sensor apparatus comprising:
(a) flexible and self-powered sensors located on opposite sides of a longitudinal centerline, and the sensors being spaced apart from each other, wherein the sensors include a pair of sensors and each sensor of the pair of sensors is configured to experience a same type of stress in both direction and magnitude; and the pair of sensors being electrically connected to an electrical terminal;
(b) each of the sensors having a thickness of 0.08-2.0 mm and including overlapping polymeric and metallic layers;
(c) the sensors being configured to detect a bending or impact characteristic; and
(d) an electrical circuit, comprising gain buffers, connected to the sensors, wherein the buffers pass along the bending or impact characteristics to an on-site electronic component which translates the signals to a real time data array; and
(e) a controller configured to receive the bending or impact characteristics from the sensors and determine a bending curvature and a direction of the bending curvature based on the bending or impact characteristics and a bending algorithm including:
K(θ)=k/hdrV(θ)
and θ=arctan(Vy/Vz) where Vθ=√{square root over (Vy2+Vz2)}
wherein the bending curvature k(θ), with its bending curve θ, Vz measures a bending output of the first pair of sensors, Vy measures a bending output of the second pair of sensors.

### Claim 23 (depends on 22)

The apparatus of claim 22, further comprising the controller configured to receive output signals from the sensors and being configured to automatically perform at least one of: (i) determining a direction of workpiece bending, (ii) determining a distance of the workpiece bending, (iii) determining an impact force, (iv) determining if an undesired condition is present in a workpiece joint, or (v) reducing undesired noise in the output signals.

### Claim 24 (depends on 22)

The apparatus of claim 22, further comprising:
a transmitter connected to the circuit; and
a controller remotely located away from the sensors and the transmitter, the controller receiving wireless signals from the transmitter;
the controller being configured to receive output signals from the sensors and being configured to automatically perform at least one of: (i) determining a direction of bending, or (ii) determining a distance of the bending.

### Claim 25 (depends on 22)

The apparatus of claim 22, further comprising:
(a) an elongated workpiece having an exterior sidewall surface;
(b) a first pair of the sensors attached to opposite sides of the exterior surface of the workpiece;
(c) at least a second pair of the sensors attached to opposite sides of the exterior surface of the workpiece;
(d) one of the first pair of the sensors being under compressive stress and another of the first pair of the sensors being under tensile stress when the workpiece bends in a first direction;
(e) one of the second pair of the sensors being under compressive stress and another of the second pair of the sensors being under tensile stress when the workpiece bends in a second direction;
(f) the sensors being configured to detect bending curvature of the workpiece in at least two dimensions by sending voltage output signals from both of the sensors of the first pair and/or both of the sensors of the second pair; and
(g) a controller configured to receive the output signals from the sensors and automatically reduce undesired noise in the output signals.

### Claim 26 (depends on 22)

The apparatus of claim 22, wherein the sensors are piezoelectric sensors, and a first pair of the sensors assists to reduce undesired noise in output signals from a second pair of the sensors.

### Claim 27 (depends on 22)

The apparatus of claim 22, wherein the sensors are ferroelectret nano-generator sensors each of a longitudinally elongated shape.

### Claim 28 (depends on 22)

The apparatus of claim 22, further comprising at least one removable and flexible fastener being configured to secure the sensors and a controller to an exterior surface of a human body part, the fastener comprising at least one of: a pressure sensitive adhesive tape, an elongated bandage or an elongated elastic wrap.

### Claim 29 (depends on 22)

The apparatus of claim 22, wherein a transverse piezoelectric effect is observed by changing permanent macro-scaled dipole moments of the sensors upon their bending, and voltage output signals for each of the sensors is linearly related to the bending curvature.

### Claim 30 (depends on 22)

The apparatus of claim 22, further comprising:
a radio frequency identification tag connected to the electrical circuit;
a programmable controller categorizing output signals of the sensors as bending direction, angle and/or distance;
the controller determining a voltage modulus and comparing sensed real-time values to pre-stored maximum and minimum threshold values;
when the controller determines that the sensed values exceed the threshold values, the controller sending a notifying output signal to a visual display; and
at least a portion of the electrical circuit being triggered remotely through the tag.

### Claim 31 (depends on 1)

The apparatus of claim 1, wherein the controller is further configured to reconstruct the bending curvature of the workpiece and the direction of the bending curvature, wherein the bending curvature and the direction is determined based on a bending algorithm as determined in:
κ(θ)=k/hdrVθ
and
θ=arctan(Vy/Vz)
where Vθ=Vθ=√{square root over (Vy2+Vz2)},
wherein the bending curvature k(θ), with it bending curve θ, Vz measures a bending output of the first pair of sensors, Vy measure a bending output of the second pair of sensors.

### Claim 32 (depends on 11)

The apparatus of claim 11, wherein the bending curvature and the direction is determined based on a bending algorithm as determined in:
κ(θ)=k/hdrVθ
and
θ=arctan(Vy/Vz)
where Vθ=Vθ=√{square root over (Vy2+Vz2)},
wherein the bending curvature k(θ), with it bending curve θ, Vz measures a bending output of the first pair of sensors, Vy measure a bending output of the second pair of sensors.