Patent ID: 12200337

DETAILED DESCRIPTION

Example methods, devices, and systems are described herein. It should be understood that the words “example” and “exemplary” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as being an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or features. Other embodiments can be utilized, and other changes can be made, without departing from the scope of the subject matter presented herein.

Thus, the example embodiments described herein are not meant to be limiting. Aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are contemplated herein.

Further, unless context suggests otherwise, the features illustrated in each of the figures may be used in combination with one another. Thus, the figures should be generally viewed as component aspects of one or more overall embodiments, with the understanding that not all illustrated features are necessary for each embodiment.

I. OVERVIEW

The present disclosure generally relates to a camera focus adjustment device formed from a piezoelectric material wedged into a flexure structure. According to the methods and techniques described herein, the camera focus adjustment device can be used to move an image sensor of a camera (attached to an autonomous vehicle) relative to a lens of the camera to provide a range of focus capability.

The flexure structure as described herein includes structural members that are interconnected using flexure notch hinges. For example, an outer framework of the flexure structure includes two horizontal structural members (e.g., a top and bottom horizontal structural member) oriented in parallel and two vertical structural members (e.g., a left and right vertical structural member) oriented perpendicularly to the horizontal structural members. To complete the outer framework of the flexure structure, the top horizontal structural member is connected to the vertical structural members using a pair of corresponding upper structural members, and the bottom horizontal structural member is connected to the vertical structural members using a pair of corresponding lower structural members. Thus, the outer framework of the flexure structure can include eight structural members that are interconnected using flexure notch hinges.

The piezoelectric material (e.g., a piezoelectric stack or a piezoelectric actuator) can be loaded between two inner structural members of the flexure structure. For example, a first inner structural member extends from the left vertical structural member and is oriented in parallel to the horizontal structural members, and a second inner structural member extends from the right vertical structural member and is oriented in parallel to the horizontal structural members. The piezoelectric material may be placed in a gap between the two inner structural members in a zero stress state. After placing the piezoelectric material in the gap, a first wedge and a second wedge are loaded between the first inner structural member and the piezoelectric material to add a compressive stress pressure to the piezoelectric material. As a non-limiting example, the wedges can be loaded such that the piezoelectric material has a compressive stress pressure of approximately fifteen (15) Megapascal (MPa). The wedges are constructed (e.g., designed) such that wedges are affixed at an angle, such as an 85 degree angle, that holds the wedges in place.

Contraction of the piezoelectric material, based on an increased temperature, can cause displacement (e.g., expansion in the vertical direction) of the flexure structure. As a non-limiting example, if the piezoelectric material is exposed to a relatively warm environment, the piezoelectric material may contract by a particular distance, such as by approximately 15 micrometers (μm). Contraction of the piezoelectric material may cause the flexure notch hinges of the flexure structure to displace (e.g., raise) the flexure structure in such a manner that the top horizontal structural member is raised by 105 μm (e.g., approximately seven times the contraction distance of the piezoelectric material). Thus, if the image sensor of the camera is coupled to the top horizontal structural member, the image sensor can be raised by the flexure structure in response to exposure of the piezoelectric material to the relatively warm environment. Raising the image sensor can substantially offset any distance fluctuations between the image sensor and the lens due to exposure to the relatively warm environment. As a non-limiting example, if the distance between the image sensor and the lens expands by approximately 105 μm due to an increase in environmental temperature, the expansion can be offset by flexure structure raising the image sensor by 105 μm.

Conversely, expansion of the piezoelectric material, based on a decreased temperature, can cause displacement (e.g., contraction in the vertical direction) of the flexure structure. As a non-limiting example, if the piezoelectric material is exposed to a relatively cool environment, the piezoelectric material may expand by a particular distance, such as by approximately 15 μm. Expansion of the piezoelectric material may cause the flexure notch hinges of the flexure structure to displace (e.g., lower) the flexure structure in such a manner that the top horizontal structural member is lowered by 105 μm (e.g., approximately seven times the expansion distance of the piezoelectric material). Thus, if the image sensor of the camera is coupled to the top horizontal structural member, the image sensor can be lowered by the flexure structure in response to exposure of the piezoelectric material to the relatively cool environment. Lowering the image sensor can substantially offset any distance changes between the image sensor and the lens due to exposure to the relatively cool environment. As a non-limiting example, if the distance between the image sensor and the lens is shortened by approximately 105 μm due to a decrease in environmental temperature, the shortened distance can be offset by flexure structure lowering the image sensor by 105 μm.

Thus, the camera focus adjustment device can move the image sensor to compensate for temperature-based distance fluctuations between the image sensor and the lens. As a result, the camera can experience a relatively large range of focus capability. It should be appreciated that the piezoelectric material may also contract or expand in response to an input voltage, such as a 100 volt (V) signal.

II. EXAMPLE EMBODIMENTS

Particular implementations are described herein with reference to the drawings. In the description, common features are designated by common reference numbers throughout the drawings. In some drawings, multiple instances of a particular type of feature are used. Although these features are physically and/or logically distinct, the same reference number is used for each, and the different instances are distinguished by addition of a letter to the reference number. When the features as a group or a type are referred to herein (e.g., when no particular one of the features is being referenced), the reference number is used without a distinguishing letter. However, when one particular feature of multiple features of the same type is referred to herein, the reference number is used with the distinguishing letter. For example, referring toFIG.1, the multiple flexure notch hinges are illustrated and associated with reference numbers150A,150B,150C, etc. When referring to a particular one of the flexure notch hinges, such as the flexure notch hinge150A, the distinguishing letter “A” is used. However, when referring to any arbitrary one of these flexure notch hinges or to these flexure notch hinges as a group, the reference number150is used without a distinguishing letter.

FIG.1is a cross-sectional diagram of a camera focus adjustment device100, in accordance with an example embodiment. As described in greater detail with respect toFIG.6, the camera focus adjustment device100is operable to reposition (e.g., move in the z-direction) an image sensor of a camera with respect to a lens of the camera to improve an image focus capability of the camera. As a non-limiting example, the camera focus adjustment device100is operable to move the image sensor in such a manner to ensure that the distance between the image sensor and the lens is within a threshold distance (e.g., ten (10) micrometers (μm)) over a relatively large temperature range. Keeping the image sensor and the lens within the threshold distance may ensure the camera has relatively high focus capabilities.

The camera focus adjustment device100includes a flexure structure102. The flexure structure102includes a plurality of structural members continuously interconnected by flexure notch hinges150A-150H. The flexure notch hinges150can be manufactured using a conventional machining process as opposed to an electrical discharge machining (EDM) process to improve a cost of manufacturing. As illustrated inFIG.1, the plurality of structural members includes a first horizontal structural member110, a second horizontal structural member112, a first vertical structural member114, a second vertical structural member116, a third horizontal structural member118, a fourth horizontal structural member120, a first upper structural member122, a second upper structural member124, a first lower structural member126, and a second lower structural member128. The structural members110,112,114,116,122,124,126,128form an outer framework of the flexure structure102, and the structural members118,120are inner structural members of the flexure structure102.

As shown inFIG.1, the second horizontal structural member112(e.g., the bottom horizontal structural member) is oriented in parallel to the first horizontal structural member110(e.g., the top horizontal structural member). The first vertical structural member114(e.g., the left vertical structural member) is oriented perpendicularly to the horizontal structural members110,112, and the second vertical structural member116(e.g., the right vertical structural member) is oriented perpendicularly to the horizontal structural members110,112. The first upper structural member122is connected to the first horizontal structural member110via a flexure notch hinge150A, and the first upper structural member122is connected to the first vertical structural member114via a flexure notch hinge150C. The second upper structural member124is connected to the first horizontal structural member110via a flexure notch hinge150B, and the second upper structural member124is connected to the second vertical structural member116via a flexure notch hinge150D. The first lower structural member126is connected to the second horizontal structural member112via a flexure notch hinge150E, and the first lower structural member126is connected to the first vertical structural member114via a flexure notch hinge114. The second lower structural member128is connected to the second horizontal structural member112via a flexure notch hinge150F, and the second lower structural member128is connected to the second vertical structural member114via a flexure notch hinge150H. As illustrated inFIG.1, the structural members110,112,114,116,122,124,126,128form an outer framework of the flexure structure102.

The third horizontal structural member118extends from the first vertical structural member114and is oriented in parallel to the first horizontal structural member110. The fourth horizontal structural member120extends from the second vertical structural member116and is oriented in parallel to the first horizontal structural member110. A gap between the third horizontal structural member118and the fourth horizontal structural member120is used to load a piezoelectric material134(e.g., a piezo stack or a piezoelectric actuator) using a pair of wedges130,132. The gap is shown in greater detail with respect to the three-dimensional illustration of the flexure structure102inFIG.2.

The piezoelectric material134is placed in the gap in a zero stress state. After placing the piezoelectric material134in the gap, the pair of wedges130,132is loaded between the third horizontal structural member118and the piezoelectric material134to add a compressive stress pressure to the piezoelectric material134. As a non-limiting example, the wedges130,132can be loaded such that the piezoelectric material134has a compressive stress pressure of approximately fifteen (15) Megapascals (MPa).

According to some implementations, the flexure structure102is comprised of a high carbon martensitic stainless steel, such as a 440C stainless steel or a 440F stainless steel. In some scenarios, the material of the flexure structure102is selected to reduce a difference between a coefficient of thermal expansion (CTE) of the flexure structure102and a CTE of the piezoelectric material134. As a non-limiting example, if 440F stainless steel is selected for the flexure structure102, the CTE in the x-direction for the flexure structure102may be approximately ten (10) parts per million (ppm) and the CTE for the piezoelectric material134along the actuation axis may be approximately negative five (−5) ppm due to the pyroelectric effect. The CTE in the z-direction for the flexure structure102may be substantially less than the CTE in the x-direction because, as described below, expansion of the flexure structure102x-direction causes the contraction of the flexure structure102in the z-direction.

The dimensions of the camera focus adjustment device100can vary based on implementation. According to one implementation, the length of the flexure structure102is approximately forty (40) millimeters (mm), the height of the flexure structure102is approximately ten (10) mm, and the width of the flexure structure is approximately five (5) mm. According to one implementation, the length of the piezoelectric material134is approximately eighteen (18) mm, the height of the piezoelectric material134is approximately three (3) mm, and the width of the piezoelectric material134is approximately two (2) mm. It should be understood that these dimensions are merely illustrative and should not be construed as limiting.

If the flexure structure102is in a zero stress state, as illustrated inFIG.1, the upper structural members122,124and the lower structural members126,128may be oriented along a similar absolute angle with respect to the x-direction (e.g., the directional orientation of the horizontal structural members110,112). According to one example, the flexure notch hinges150may be designed such that the upper structural members122,124and the lower structural members126,128are oriented along an absolute angle of three (3) degrees with respect to the x-direction. In this embodiment, the orientation angle (θ) of the first upper structural member122with respect to the x-direction is approximately three (3) degrees. In this scenario, the absolute orientation angles of the second upper structural member124and the lower structural members126,128may be substantially similar.

During operation, contraction of the piezoelectric material134, based on an increased temperature, can cause displacement (e.g., expansion in the z-direction) of the flexure structure102. As a non-limiting example, if the piezoelectric material134is exposed to a relatively warm environment, the piezoelectric material134may contract by a particular distance in the x-direction, such as by approximately 15 micrometers (μm). Contraction of the piezoelectric material134may cause the flexure notch hinges150of the flexure structure102to displace (e.g., raise) the flexure structure102in such a manner that the first horizontal structural member110is raised by 105 μm (e.g., approximately seven times the contraction distance of the piezoelectric material134). Thus, if an image sensor of a camera is coupled to the first horizontal structural member110, as described below with respect toFIG.6, the image sensor can be raised (in the z-direction) by the flexure structure102in response to exposure of the piezoelectric material134to the relatively warm environment. Raising the image sensor can substantially offset any distance changes between the image sensor and a lens due to exposure to the relatively warm environment. As a non-limiting example, if the distance between the image sensor and the lens expands by approximately 105 μm due to an increase in environmental temperature, the expansion can be offset by flexure structure102raising the image sensor by 105 μm.

Expansion of the piezoelectric material134, based on a decreased temperature, can cause displacement (e.g., contraction in the z-direction) of the flexure structure102. As a non-limiting example, if the piezoelectric material134is exposed to a relatively cool environment, the piezoelectric material134may expand by a particular distance x-direction, such as by approximately 15 μm. Expansion of the piezoelectric material134may cause the flexure notch hinges150of the flexure structure102to displace (e.g., lower) the flexure structure102in such a manner that the first horizontal structural member110is lowered by 105 μm (e.g., approximately seven times the expansion distance of the piezoelectric material134). Thus, if the image sensor of the camera is coupled to the first horizontal structural member110, the image sensor can be lowered by the flexure structure102in response to exposure of the piezoelectric material134to the relatively cool environment. Lowering the image sensor can substantially offset any distance changes between the image sensor and the lens due to exposure to the relatively cool environment. As a non-limiting example, if the distance between the image sensor and the lens is shortened by approximately 105 μm due to a decrease in environmental temperature, the shortened distance can be offset by flexure structure102lowering the image sensor by 105 μm.

Thus, the camera focus adjustment device100can move the image sensor to compensate for temperature-based distance fluctuations between the image sensor and the lens. As a result, the camera can experience a relatively large range of focus capability.

It should be appreciated that the flexure structure102experiences a substantial expansion in the z-direction based on a relatively small of amount of piezoelectric material134contraction in the x-direction. For example, the flexure structure102can be designed to amplify the motion of the piezoelectric material134by at least a factor of seven. Because the flexure structure102is designed to produce a relatively pure translation in the z-direction, it should be appreciated that translation and rotation in the x-direction and the y-direction is substantially reduced, which improves camera focus capabilities.

FIGS.2-5illustrate a process for manufacturing the camera focus adjustment device100ofFIG.1. In particular, the process for loading the piezoelectric material134into the flexure structure102is described with respect toFIGS.2-5.

FIG.2is a three-dimensional diagram of the flexure structure102, in accordance with an example embodiment. The flexure structure102includes the outer framework comprised of the structural members110,112,114,116,122,124,126,128. The flexure structure102also includes the horizontal structural members118,120extending from the vertical structural members114,116, respectively. As illustrated inFIG.2, the flexure structure102includes a gap200between the horizontal structural members118,120. The gap200is used to load the piezoelectric material134using the pair of wedges130,132, as described with respect toFIGS.3-5.

FIG.3is a three-dimensional diagram of the flexure structure102with the piezoelectric material134, in accordance with an example embodiment. For example, as illustrated inFIG.3, the piezoelectric material134is placed in the gap200in a zero stress state. That is, the piezoelectric material134is positioned between the horizontal structural members118,120with little to approximately no stress applied to the piezoelectric material134.

FIG.4is a three-dimensional diagram of the camera focus adjustment device100, in accordance with an example embodiment. For example, as illustrated inFIG.4, the wedge130and the wedge132are loaded between the third horizontal structural member118and the piezoelectric material134to add the compressive stress pressure to the piezoelectric material134.

FIG.5is a diagram illustrating the process of loading the piezoelectric material134with the wedges130,132, in accordance with an example embodiment. For example,FIG.5illustrates the third horizontal structural member118, the wedge130, the wedge132, and the piezoelectric material134.

As illustrated inFIG.5, the wedge130is coupled (e.g., affixed) to the wedge132at a particular angle (α). According to one implementation, the wedges130,132are designed such that the particular angle (α) is equal to 85 degrees. In some non-limiting scenarios, the particular angle (α) can range from 84.5 degrees to 85.5 degrees. It should be understood that in different implementations, the range of the particular angle (α) may vary. It should also be understood that in some implementations, the wedges130,132may be coupled at a 90 degree angle and held in place via an adhesive. However, coupling or affixing the wedges130,132at the particular angle (α) may ensure that friction holds the wedges130,132in place when a force, such as a particular load force (Fz), is removed.

As illustrated inFIG.5, the wedge132is positioned (e.g., wedged) between the third horizontal structural member118and the piezoelectric material134. After the wedge132is positioned, the wedge130is positioned (e.g., wedged) between the wedge132and the third horizontal structural member118using a particular load force (Fz). According to one implementation, the particular load force (Fz) can be 26 Newtons (N) applied to the wedge130along the z-direction to load the piezoelectric material134with a compressive stress pressure of approximately 15 MPa. That is, the particular load force (Fz) of 26 N can create an axial force of 90 N in the x-direction using the 85 degree wedges130,132to load (e.g., pre-load) the piezoelectric material134with the compressive stress pressure of approximately 15 MPa. Pre-loading the piezoelectric material134with the wedges130,132may cause the flexure structure102to contract by approximately 75 μm in the z-direction and may cause the piezoelectric material134to contract by approximately 6 μm in the x-direction.

By pre-loading the piezoelectric material134with the wedges130,132, an external pre-load spring may be unnecessary. Once the piezoelectric material134is loaded and the particular load force (Fz) is removed, it will be appreciated that friction may hold the wedges130,132in place. Thus, the friction between the wedges130,132is used to maintain the compressive stress pressure of the piezoelectric material134. However, in certain implementations, an adhesive500(e.g., an ultraviolet-curable adhesive) may be used between the flexure structure102, the wedges130,132, and the piezoelectric material134.

FIG.6is a diagram of a camera600that includes the camera focus adjustment device100, in accordance with an example embodiment. As shown inFIG.6, the camera600includes a fixed surface602, the camera focus adjustment device100, an image sensor board604, an image sensor606, and a lens608. It should be understood that the camera600can include other components that are not illustrated inFIG.6. As non-limiting examples, the camera600can also include a lens mount, a flash, a shutter, a mirror, a filter, etc.

The second horizontal structural member112of the camera focus adjustment device100can be rigidly affixed to the fixed surface602. Rigidly affixing the second horizontal structural member112to the fixed surface602may prevent movement of the second horizontal structural member112when the piezoelectric material134expands or contracts. That is, the camera focus adjustment device100can collapse to the second horizontal structural member112or raise from the second horizontal structural member112, but the position of the second horizontal structural member112is fixed.

As illustrated inFIG.6, the first horizontal structural member110of the camera focus adjustment device100can be affixed (e.g., coupled) to the image sensor board604, and the image sensor606is coupled to the image sensor board604. According to one implementation, the image sensor606is positioned within a threshold distance from the lens608of the camera600to provide the camera600a range of image focus capability. As a non-limiting example, the image sensor606can be positioned within ten (10) micrometers (μm) of the lens608to provide the camera600a range of image focus capability.

However, in some scenarios, the distance between the image sensor606and the lens608can fluctuate based on temperature. For example, the distance between the image sensor606and the lens608may expand in warmer temperatures, and the distance between the image sensor606and the lens608may contract in cooler temperatures.

To adjust for distance fluctuations between the image sensor606and the lens608, the camera focus adjustment device100is operable to vertically translate (e.g., translate in the z-direction) based on temperature-based piezoelectric activity associated with piezoelectric material134. For example, contraction of the piezoelectric material134in warm environments can cause the flexure notch hinges150of the camera focus adjustment device100to displace (e.g., raise) the camera focus adjustment device100in the z-direction. To illustrate, when the piezoelectric material134contracts in the x-direction, the flexure notch hinges150raise the camera focus adjustment device100. As a result, the image sensor board604coupled to the first horizontal structural member110, and thus the image sensor606, is raised such that the image sensor606is vertically translated (in the z-direction) to be closer to the lens608. Thus, in warmer temperatures where the distance between the image sensor606and the lens608expands to a point whereby the focus capability of the camera600is potentially compromised, the camera focus adjustment device100can raise the image sensor606closer to the lens608to improve the focus capability of the camera600.

Alternatively, expansion of the piezoelectric material134in cool environments can cause the flexure notch hinges150of the camera focus adjustment device100to displace (e.g., lower) the camera focus adjustment device100in the z-direction. To illustrate, when the piezoelectric material134expands in the x-direction, the flexure notch hinges150lower the camera focus adjustment device100. As a result, the image sensor board604coupled to the first horizontal structural member110, and thus the image sensor606, is lowered such that the image sensor606is vertically translated (in the z-direction) to be further from the lens608. Thus, in cooler temperatures where the distance between the image sensor606and the lens608contracts to a point whereby the focus capability of the camera600is potentially compromised, the camera focus adjustment device100can lower the image sensor606from the lens608to improve the focus capability of the camera600.

Thus, the camera focus adjustment device100is operable to control the distance between the image sensor606and the lens608over a relatively large temperature range to ensure the camera600has relatively high focus capabilities. For example, the camera focus adjustment device100can move the image sensor606to compensate for fluctuations in the distance between the image sensor606and the lens608based on temperature.

The camera focus adjustment device100provides additional benefits to the camera600. For example, because the camera focus adjustment device100does not include any sliding elements, such as bearing or lead screws, the camera600may not be subject to backlash or particle generation that is associated with sliding elements. Additionally, the camera focus adjustment device100can maintain or hold the image sensor606at a constant distance from the lens608without using power, which may result in increased power savings.

By moving the image sensor606, the camera focus adjustment device100can adjust the distance between the image sensor606and the lens608while keeping the camera600sealed from external elements that the camera600may otherwise be exposed to if the lens608is moved. Additionally, the camera focus adjustment device100is subject to a reduced load compared to conventional devices that move the lens608because the lens608is heavier than the image sensor606.

FIG.7is a three-dimensional diagram of the camera focus adjustment device100coupled to the image sensor606of the camera606, in accordance with an example embodiment. As illustrated inFIG.7, the image sensor board604is positioned on top of the camera focus adjustment device100, and the image sensor606is coupled to the image sensor board604. The camera focus adjustment device100is configured to raise the image sensor board604, and thus the image sensor606, in the z-direction in response to the piezoelectric material134contracting. For example, contraction of the piezoelectric material134may cause the flexure structure102to expand in the z-direction, which in turn, raises the image sensor606.

Because the flexure structure102is designed to produce a relatively pure translation in the z-direction, it should be appreciated that flexure structure102reduces translation and rotation in the x-direction and the y-direction.

FIG.8is a diagram of an autonomous vehicle800, in accordance with an example embodiment. Although the autonomous vehicle800is illustrated as a car, in other implementations, the autonomous vehicle800may take the form of a truck, motorcycle, bus, boat, airplane, helicopter, lawn mower, earth mover, snowmobile, aircraft, recreational vehicle, amusement park vehicle, farm equipment, construction equipment, tram, golf cart, train, and trolley, for example. Other vehicles are possible as well. The autonomous vehicle100may be configured to operate fully or partially in an autonomous mode. For example, the autonomous vehicle100may control itself while in the autonomous mode, and may be operable to determine a current state of the autonomous vehicle100and its environment, determine a predicted behavior of at least one other vehicle in the environment, determine a confidence level that may correspond to a likelihood of the at least one other vehicle to perform the predicted behavior, and control the autonomous vehicle100based on the determined information. While in the autonomous mode, the autonomous vehicle100may be configured to operate without human interaction.

InFIG.8, the camera600is coupled to a roof802of the autonomous vehicle800. Although illustrated as coupled to the roof802, in other implementations, the camera600can be coupled to other components of the autonomous vehicle800. The camera600includes the components illustrated inFIG.6, such as the fixed surface602, the camera focus adjustment device100, the image sensor board604, the image sensor606, and the lens608. The camera600may be a high-resolution camera operable to capture high-resolution images of the environment surrounding the autonomous vehicle800.

The flexure structure102of the camera focus adjustment device100can have a stiffness quality that passively rejects vibrations, such as automotive vibration of the autonomous vehicle800. For example, the design and material of the flexure structure102may result in the flexure structure102remaining substantially steady despite external vibrations of surfaces coupled to the flexure structure102. Thus, the flexure structure102experiences little to no movement based on external vibrations.

III. EXAMPLE METHODS

FIG.9is a flowchart of a method900, according to an example embodiment. The method900can be performed by manufacturing equipment.

The method900includes inserting piezoelectric material in a gap between two inner structural members of a flexure structure of a camera focus adjustment device, at902. The flexure structure includes an outer framework of structural members continuously interconnected by flexure notch hinges and the two inner structural members. The two inner structural members are oriented in parallel and extending from the outer framework of the structural members. For example, referring toFIGS.2-3, the piezoelectric material134is inserted, in a zero stress state, in the gap200between the horizontal structural members118,120. The flexure structure112includes the outer framework of structural members110,112,114,116,122,124,126,128continuously interconnected by the flexure notch hinges150. The flexure structure102also includes the two inner structural members118,120.

The method900also includes applying a compressive stress pressure to the piezoelectric material by loading a first wedge between a first inner structural member of the two inner structural members and the piezoelectric material, at904. For example, referring toFIGS.4-5, compressive stress pressure is applied to the piezoelectric material134by loading the wedge132between the structural member118and the piezoelectric material134.

The method900further includes applying additional compressive stress pressure to the piezoelectric material by loading a second wedge between the first inner structural member and the first wedge, at906. In some implementations, the first wedge and the second wedge are affixed at an angle to ensure friction holds the wedges in place when a force is removed. For example, referring toFIGS.4-5, additional compressive stress pressure is applied to the piezoelectric material by loading the wedge130between the structural member118and the wedge132. According to one non-limiting implementation, the wedges130,132may be affixed at an 85 degree angle. However, it should be understood that the wedges130,132may be affixed at different angles in other implementations. As illustrated inFIG.5, according to one implementation, a particular load force (Fz) of 26 Newtons (N) can be applied to the wedge130along the z-direction to load the piezoelectric material134with a compressive stress pressure of approximately 15 MPa. That is, the particular load force (Fz) of 26 N can create an axial force of 90 N in the x-direction using the 85 degree wedges130,132to load (e.g., pre-load) the piezoelectric material134with the compressive stress pressure of approximately 15 MPa. Pre-loading the piezoelectric material134with the wedges130,132may cause the flexure structure102to contract by approximately 75 μm in the z-direction and may cause the piezoelectric material134to contract by approximately 6 μm in the x-direction.

By pre-loading the piezoelectric material134with the wedges130,132, the use of an external pre-load spring can be bypassed. Once the piezoelectric material134is loaded and the particular load force (Fz) is removed, it will be appreciated that friction may hold the wedges130,132in place. Thus, the friction between the wedges130,132is used to maintain the compressive stress pressure. However, in certain implementations, an adhesive500may be used between the flexure structure102, the wedges130,132, and the piezoelectric material134.

IV. CONCLUSION

The particular arrangements shown in the Figures should not be viewed as limiting. It should be understood that other embodiments may include more or less of each element shown in a given Figure. Further, some of the illustrated elements may be combined or omitted. Yet further, an illustrative embodiment may include elements that are not illustrated in the Figures.

A step or block that represents a processing of information can correspond to circuitry that can be configured to perform the specific logical functions of a herein-described method or technique. Alternatively or additionally, a step or block that represents a processing of information can correspond to a module, a segment, or a portion of program code (including related data). The program code can include one or more instructions executable by a processor for implementing specific logical functions or actions in the method or technique. The program code and/or related data can be stored on any type of computer readable medium such as a storage device including a disk, hard drive, or other storage medium.

The computer readable medium can also include non-transitory computer readable media such as computer-readable media that store data for short periods of time like register memory, processor cache, and random access memory (RAM). The computer readable media can also include non-transitory computer readable media that store program code and/or data for longer periods of time. Thus, the computer readable media may include secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media can also be any other volatile or non-volatile storage systems. A computer readable medium can be considered a computer readable storage medium, for example, or a tangible storage device.

While various examples and embodiments have been disclosed, other examples and embodiments will be apparent to those skilled in the art. The various disclosed examples and embodiments are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims.