# Patent

## Title
Sensor systems

## Abstract

A sensor assembly includes a frame defining a sensor axis having opposing endplates with axially extending supports, wherein the opposing endplates are connected by a pair of axially extending side beams. A suspended mass is within an interior of the frame suspended from the supports of the frame. A plurality of spacers are operatively connected to the endplates and supports of the frame. A plurality of piezoelectric material layers are operatively connected to sides of respective spacers opposite the frame to damp vibrations.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present disclosure relates to sensor systems, and more particularly to sensor assemblies such as those used in imaging devices.
2. Description of Related Art
A variety of devices and methods are known in the art for sensor systems on aircraft. One parameter that directly affects the quality of many of the images collected by the sensor systems is line-of-sight (LOS) stabilization. One source of sensor LOS destabilization is vibration within the sensor system. Vibrations can be created by environmental influences on the sensor system (e.g. wind drag and turbulence), by operational factors, by platform sources (e.g. aircraft vibrations) and by components within the sensor itself (e.g. fans, heaters, etc.). By reducing or damping vibrations acting on the sensor system, LOS stabilization can be improved, resulting in improved quality of images and other data captured by the sensor.
Current sensor systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved sensor systems. The present disclosure provides a solution for this need.
SUMMARY OF THE INVENTION
A sensor assembly includes a frame, a suspended mass within an interior of the frame defining a sensor axis, and a piezoelectric material layer operatively connected to the frame. The piezoelectric material layer is connected to the frame through a spacer with the piezoelectric material layer mounted to a side of the spacer opposite of the frame to damp vibrations of the suspended mass.
In accordance with some embodiments, the piezoelectric material layer is a macro-fiber composite (MFC) piezoelectric material layer. The frame can include inwardly extending supports to which the suspended mass is suspended from. The spacer can be operatively connected to one of the supports of the frame. The spacer can be a non-piezoelectric material spacer and/or can be a MFC piezoelectric material spacer. The spacer can be a wedge shaped spacer that includes a spacer surface at an angle with respect to a frame surface to which it is operatively connected. The angle of the spacer surface with respect to the frame surface can range from 1 degree to 45 degrees. The frame can include a pair of endplates spaced apart from one another along the sensor axis. A pair of axially extending side beams can connect the pair of endplates. The spacer can be operatively connected to an outer surface and/or an inner surface of one of the endplates of the frame.
A sensor assembly includes a frame defining a sensor axis having opposing endplates with axially extending supports, wherein the opposing endplates are connected by a pair of axially extending side beams. A suspended mass is suspended within an interior of the frame from the supports of the frame. A plurality of piezoelectric material layers are operatively connected to the endplates and supports of the frame through respective spacers. Each piezoelectric material layer is mounted to a side of the respective spacer opposite of the frame to damp vibrations of the suspended mass. An outer surface of each of the endplates can include a respective one of the spacers operatively connected thereto.
These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
FIG. 1 is a perspective view of an exemplary embodiment of a sensor system constructed in accordance with the present disclosure, showing the frame and the suspended mass;
FIG. 2 is a top plan view of the sensor system of FIG. 1, showing the supports;
FIG. 3 is a perspective view of another exemplary embodiment of a sensor system constructed in accordance with the present disclosure, showing the frame and the suspended mass;
FIG. 4 is a top plan view of the sensor system of FIG. 3, showing the supports and the endplates having a piezoelectric material layer;
FIG. 5 is a side elevation view of a portion of the sensor system of FIG. 3, showing the surface of the spacer at an angle with respect to a surface of the frame; and
FIG. 6 is a cross-sectional end view of the sensor system of FIG. 3, showing the supports with a spacer between a side of the stub beam and the piezoelectric material layer.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a sensor assembly constructed in accordance with the disclosure is shown in FIG. 1 and is designated generally by reference character 100. Other embodiments of sensor assemblies in accordance with this disclosure, or aspects thereof, are provided in FIGS. 2-6, as will be described. The systems and methods described herein can be used to reduce vibration experienced by sensor assemblies and reduce the weight of sensor assemblies.
As shown in FIG. 1, a sensor assembly 100 includes a frame 102, a suspended mass 104 within an interior of frame 102 defining a sensor axis A, and a spacer 106 operatively connected to frame 102. A piezoelectric material layer 114 is operatively connected to a side of spacer 106 opposite of frame 102 to damp vibrations. Those skilled in the art will readily appreciate that suspended mass 104 can include a variety of electrical, optical and/or mechanical sensor components, and/or accessories therefor. It is contemplated that piezoelectric material layer 114 can be a macro-fiber composite (MFC) piezoelectric material layer, such as an MFC piezoelectric material available from Smart Material Corp., Sarasota, Fla. A MFC piezoelectric material includes piezoelectric ceramic fibers arranged in a specific sequence that results in an electro-mechanical response either when exposed to strains created by vibration-induced material deformation or when commanded to exert mechanical force that creates material deformation by applying a specifically controlled electrical signal to the MFC. This electro-mechanical response can be commanded to elongate or contract the structure to counteract unwanted measured vibrational strains, providing a lightweight alternative to traditional damping systems.
With continued reference to FIG. 1, spacer 106 acts as a moment arm to increase the damping effect of piezoelectric material layers 114. Those skilled in the art will readily appreciate that spacer 106 can be a non-piezoelectric material spacer and/or can be a MFC piezoelectric material spacer. It is contemplated that if spacer 106 is a piezoelectric material electrically connected in a similar manner as piezoelectric material layer 114, the overall damping force applied at a given location can be doubled. Even if not electrically charged, a spacer 106 that is a piezoelectric material would act to increase the moment arm but would not impart any damping force itself. Those skilled in the art will readily appreciate that one or more spacers 106 can be used, and/or piezoelectric material layer 114 can be laminated onto a surface of spacer 106. Additionally, it is contemplated that the shape and thickness of spacer 106 can vary as needed for a given application.
In use, piezoelectric material layer 114 can be actively or proactively controlled. For example, for active control in accordance with some embodiments, piezoelectric material layers 114 are operatively connected to a digital signal processor. The digital signal processor can provide instructions to piezoelectric material layers 114 based on real-time vibration data received from vibration sensors arranged throughout sensor assembly 100 to actively damp vibrations in assembly 100 via a closed-loop arrangement. For proactive control, an electric signal can be used to actuate piezoelectric material layers 114 based upon characteristic information of vibration causing influences measured prior to the real-time events that cause the vibration, such as turbulence, to proactively damp vibrations in the frame.
Now with reference to FIG. 2, frame 102 includes inwardly extending supports 108 to which suspended mass 104 is suspended from, and a pair of endplates 110 spaced apart from one another along sensor axis A. A pair of axially extending side beams 112 connect endplates 110. Spacers 106 and piezoelectric material layers 114 are arranged in a mirrored configuration with respect to an axis T transverse to longitudinal axis A. This mirrored configuration permits piezoelectric material layers 114 to apply equal and opposite damping forces, therein providing even damping to the frame.
As shown in FIG. 3, a sensor assembly 200, similar to sensor assembly 100, includes a frame 202, a suspended mass 204 defining a sensor axis A, and a spacer 206 operatively connected to frame 202. A piezoelectric material layer 214 is operatively connected to a side of spacer 206 opposite of frame 202 to damp vibrations. Spacers 206 on endplate 210 of sensor assembly 200 are wedged shaped. Each wedged shaped spacer 206 permits its respective piezoelectric material layer 214 to apply force in two directions. For example, piezoelectric material layers 214 on endplates 210 apply force in an z direction and a y direction, while piezoelectric material layers 214 on supports 208 apply force in an x direction and a y direction. It is contemplated that the wedge shape can be altered to provide damping forces in the desired directions.
With reference now to FIGS. 4-6, spacers 206 are operatively connected to endplates 210 and supports 208 of frame 202. While spacers 206 and their corresponding piezoelectric material layers 214 are described herein as being placed on supports 208 and endplates 210 of frame 202, it is contemplated that spacers 206 and piezoelectric material layers 214 can be can be placed in a variety of locations on frame 202 that experience or are expected to experience vibration induced displacement or deflection. For example, a 3-dimensional arrangement of piezoelectric devices, as shown in FIGS. 3-6, would be required to cancel 3-dimensional vibrational influences. Wedged shaped spacers 206 include a spacer surface 216 at an angle with respect to which ever frame surface to which it is operatively connected. For example, spacer surface 216 is at an angle with respect to endplate outer surface 218. This is shown by an axis X extending perpendicularly from surface 216 being at an angle with respect to longitudinal axis A, which is perpendicular to endplate outer surface 218. Spacer surface 216 is also at an angle with respect to a surface 220 of one of supports 208. The angle of spacer surface 216 with respect to whichever frame surface it is operatively connected to ranges from 1 degree to 45 degrees, for example from 5 degrees to 20 degrees, or more particularly from 10 degrees to 15 degrees.
The methods and systems of the present disclosure, as described above and shown in the drawings, provide for sensor assemblies with superior properties including enhanced sensor imaging and/or data collecting capabilities due to reduced vibration and reduced weight. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject disclosure.

## Claims

1. A sensor assembly comprising:
a frame;
a suspended mass within an interior of the frame defining a sensor axis; and
a piezoelectric material layer operatively connected to the frame through a spacer with the piezoelectric material layer mounted to a side of the spacer opposite of the frame to damp vibrations of the suspended mass.

2. A sensor assembly as recited in claim 1, wherein the piezoelectric material layer is a macro-fiber composite (MFC) piezoelectric material layer.

3. A sensor assembly as recited in claim 1, wherein the frame includes inwardly extending supports to which the suspended mass is suspended from.

4. A sensor assembly as recited in claim 3, wherein the spacer is operatively connected to one of the supports of the frame.

5. A sensor assembly as recited in claim 1, wherein the frame includes a pair of endplates spaced apart from one another along the sensor axis, and a pair of axially extending side beams connecting the pair of endplates.

6. A sensor assembly as recited in claim 5, wherein the spacer is operatively connected to an outer surface of one of the endplates of the frame.

7. A sensor assembly as recited in claim 5, wherein the spacer is operatively connected to an inner surface of one of the endplates of the frame.

8. A sensor assembly as recited in claim 1, wherein the spacer is a non-piezoelectric material spacer.

9. A sensor assembly as recited in claim 1, wherein the spacer is a MFC piezoelectric material spacer.

10. A sensor assembly as recited in claim 1, wherein the spacer is a wedge shaped spacer that includes a spacer surface at an angle with respect to a frame surface to which it is operatively connected.

11. A sensor assembly as recited in claim 10, wherein the angle of the spacer surface with respect to the frame surface ranges from 1 degree to 45 degrees.

12. A sensor assembly comprising:
a frame defining a sensor axis having opposing endplates with axially extending supports, wherein the opposing endplates are connected by a pair of axially extending side beams;
a suspended mass suspended within an interior of the frame from the supports of the frame; and
a plurality of piezoelectric material layers operatively connected to the endplates and supports of the frame through respective spacers with each piezoelectric material layer mounted to a side of the respective spacer opposite of the frame to damp vibrations of the suspended mass.

13. A sensor assembly as recited in claim 12, wherein the piezoelectric material layer is a macro-fiber composite (MFC) piezoelectric material layer.

14. A sensor assembly as recited in claim 12, wherein each spacer is a wedge shaped spacer that includes a spacer surface at an angle with respect to a frame surface to which it is operatively connected.

15. A sensor assembly as recited in claim 12, wherein an outer surface of each of the endplates includes a respective one of the spacers operatively connected thereto.