Multi-anchor high frequency accelerometer

Abstract

A single-axis pendulum accelerometer having a plurality of anchors is disclosed. The plurality of anchors may be arranged around a rotation axis of a pendulum proof mass. Each of the plurality of anchors may be coupled to the proof mass by two torsion springs each extending along the rotation axis. The plurality of anchors allows an increased number of torsion springs coupled to the proof mass, and thus a greater torsional stiffness of the proof mass may be achieved. Due to the higher torsional stiffness, the disclosed single-axis pendulum accelerometer may be deployed in high frequency environments, such as about 20 kHz and above, where increased torsional stiffness is desired.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. patent application Ser. No. 16 / 457,849, filed on Jun. 28, 2019, Attorney Docket No. G0766.70277US00, and entitled “Multi-Anchor High Frequency Accelerometer,” under 35 U.S.C. §120, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to a micro-electromechanical system (MEMS) single-axis accelerometer. Background Art

[0004] A single-axis accelerometer (eg, A) may include a "teeter-totter" proof mass that rotates about an axis of rotation in response to acceleration along the single axis. Accelerometers can operate over a wide frequency range. Summary of the invention

[0005] A single-axis pendulum accelerometer having a plurality of anchors is disclosed. The plurality of anchors may be arranged around a rotation axis of a pendulum proof mass. Each of the plurality of anchors may be coupled to the proof mass by two torsion springs each extending along the rotation axis. The plurality of anchors allows an increased number of torsion springs coupled to the proof mass, and thus a greater torsional stiffness of the proof mass may be achieved. Due to the higher torsional stiffness, the disclosed single-axis pendulum accelerometer may be deployed in high frequency environments, such as about 20 kHz and above, where increased torsional stiffness is desired.

[0006] According to an aspect of the present application, a single-axis oscillating MEMS accelerometer is provided, comprising: a substrate; a proof mass suspended above the substrate; and a plurality of anchors arranged in a straight line parallel to the rotation axis of the proof mass and coupling the proof mass to the substrate. Each of at least two anchors of the plurality of anchors is coupled to an inner edge of the proof mass by two respective in-line torsion springs.

[0007] According to aspects of the present application, a single-axis oscillating MEMS accelerometer is provided, comprising: a substrate; a detection mass suspended above the substrate; a plurality of anchors coupling the detection mass to the substrate; and at least three torsion springs coupling the plurality of anchors to the detection mass. The plurality of anchors and the at least three torsion springs are arranged in a row along the rotation axis of the detection mass.

[0008] According to aspects of the present application, a single-axis swing-type MEMS accelerometer is provided, comprising: a substrate; a detection mass suspended above the substrate; and a plurality of anchors arranged along the rotation axis of the detection mass, disposed within the circumference of the detection mass, and coupling the detection mass to the substrate, wherein the plurality of anchors include a first anchor and a second anchor. The single-axis swing-type MEMS accelerometer comprises: a first torsion spring extending along the rotation axis and coupling the detection mass to the first anchor, wherein the first torsion spring is arranged on a first side of the first anchor; a second torsion spring extending along the rotation axis and coupling the detection mass to the first anchor, wherein the second torsion spring is arranged on a second side of the first anchor different from the first side of the first anchor; a third torsion spring extending along the rotation axis and coupling the detection mass to the second anchor, wherein the third torsion spring is arranged on a first side of the second anchor; and a fourth torsion spring extending along the rotation axis and coupling the detection mass to the second anchor, wherein the fourth torsion spring is arranged on a second side of the second anchor different from the first side of the second anchor. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Various aspects and embodiments of the present application will be described with reference to the following drawings. It should be understood that these drawings are not necessarily drawn to scale. Items appearing in multiple drawings are represented by the same reference numerals in all drawings in which they appear.

[0010] Figure 1A is a side view of a single-axis accelerometer having at least two anchors according to a non-limiting embodiment of the present application.

[0011] Figure 1B According to a non-limiting embodiment Figure 1A Top view of a single-axis accelerometer.

[0012] Figure 1C According to a non-limiting embodiment Figure 1B A top detailed plan view of the proof mass and anchor of a single-axis accelerometer;

[0013] Figure 2 is a top view of a single-axis accelerometer having at least two anchors according to a non-limiting embodiment of the present application.

[0014] Figure 3 An automobile is shown which may include a single-axis accelerometer of one of the types described herein, according to a non-limiting embodiment of the present application.

[0015] Figure 4 A piece of industrial equipment is shown on which three single-axis accelerometers of the type described herein are provided according to a non-limiting embodiment of the present application. DETAILED DESCRIPTION

[0016] Aspects of the present application relate to a microelectromechanical system (MEMS) single-axis accelerometer having a proof mass or beam configured to pivot about an axis of rotation. In various embodiments, a plurality of anchors are coupled to an inner edge of the proof mass, arranged within the perimeter of the proof mass, and / or embedded within the proof mass. The anchors may be arranged on or offset from the axis of rotation. In some embodiments, each anchor is coupled to the proof mass by at least two torsion springs. Each of the two torsion springs may be arranged to extend along the axis of rotation and may be arranged on or offset from the axis. The overall stiffness of a single-axis accelerometer having multiple anchors along the axis of rotation disclosed herein may be greater than the overall stiffness of a conventional single-axis accelerometer, particularly at higher frequencies, such as greater than about 20 kHz. In various embodiments, the target operating frequency of the increased stiffness accelerometer may include a range greater than about 10 kHz, greater than about 15 KHz, greater than about 20 kHz, greater than about 30 kHz, greater than about 39 kHz, or greater than about 43 kHz, although other frequency ranges are possible and the various aspects described herein are not limited to these specific frequencies.

[0017] The inventors have recognized that accelerometers including an increased number of anchors (e.g., at least two anchors) may be suitable for higher target frequency environments. The inventors have recognized that at higher frequencies, it may be necessary for the accelerometer's pivoting proof mass to have greater overall stiffness to avoid proof mass contact with the substrate and other high-frequency effects. High-frequency devices may also enable applications based on condition monitoring, which is a method that uses vibration measurements to assess the prediction of failures over time. Early failure prediction of machines and equipment can be important to predict possible future downtime, improve system reliability, reduce maintenance costs (which can be in the millions of dollars range for large companies), and reduce the number of maintenance operations.

[0018] In conventional accelerometers, when increased torsional stiffness is desired, the cross-sectional area of ​​the accelerometer's torsion spring is increased, and the length of the accelerometer's torsion spring is decreased to achieve the increased stiffness. However, the inventors have recognized that as the cross-sectional area increases and the length decreases, the torsion spring continues to function as a spring, as opposed to a rigid rod, with a maximum functional cross-sectional area and a minimum functional length. At a certain point, the cross-sectional area can no longer be increased, the length can no longer be decreased, and the stiffness of the spring reaches a maximum. Furthermore, these conventional high cross-sectional, low length springs are stiff and prone to breaking.

[0019] The inventors have recognized that the conventional configuration of a single anchor and two springs may not provide sufficient stiffness for certain frequencies and environments. By using a configuration of at least two anchors, each anchor may be configured with two torsion springs. It may be considered to place the additional springs in parallel and increase the overall stiffness of the accelerometer. Thus, by increasing the number of anchors and therefore also the number of springs in the accelerometer, while increasing the overall stiffness of the accelerometer, the accelerometer may be more suitable for high target operating frequency environments.

[0020] The above aspects and embodiments, as well as additional aspects and embodiments, are further described below. These aspects and / or embodiments may be used alone, together, or in any combination of two or more, as application is not limited in this regard.

[0021] Figure 1A A side view of a uniaxial accelerometer 100 according to an exemplary embodiment of the present application is shown. The uniaxial accelerometer 100 is arranged on a substrate 102 having an upper surface 104 and includes a proof mass 106, at least a first anchor 108a, a first proof mass portion 110, a second proof mass portion 112, a first electrode 114, a second electrode 116, a third electrode 126, and a fourth electrode 128. The proof mass 106 is configured to pivot about a rotation axis 118 and may be coupled to the anchor by at least one torsion spring (not shown). A distance D1 represents a distance between the first proof mass portion 110 and the first electrode 114, a distance D2 represents a distance between the second proof mass portion 112 and the second electrode 116, a distance D3 represents a distance between the first proof mass portion 110 and the third electrode 126, and a distance D4 represents a distance between the second proof mass portion 112 and the fourth electrode 128.

[0022] In some embodiments, the uniaxial accelerometer is configured to sense acceleration in the z direction. Figure 1A In the embodiment of the present invention, the single-axis accelerometer 100 is configured to sense acceleration in the z-direction. Therefore, the single-axis accelerometer 100 may also be referred to as a z-axis accelerometer.

[0023] In some embodiments, the proof mass is suspended above the substrate 102. The proof mass 106 can be configured to move relative to the substrate 102 in response to acceleration along a single axis (in this example, the z-direction). In some embodiments, the proof mass substrate 106 pivots about the rotation axis 118 in response to the acceleration to be measured. Figure 1AIn the illustrative embodiment of , the rotation axis 118 is substantially arranged in the xy plane. Typically, the xy plane is formed by the upper surface 104 of the substrate 102. Therefore, the rotation axis 118 can be arranged substantially parallel to the upper surface 104 of the substrate 102. Other arrangements are also possible depending on the definition of the coordinate system and the acceleration direction to be sensed.

[0024] According to aspects of the present application, proof mass 106 pivots in response to acceleration along a single axis due to the unbalanced mass of proof mass 106. In at least one aspect, proof mass 106 can be asymmetric with respect to rotation axis 118. For example, proof mass 106 can be disposed in or include one or more solutions that may have different masses. In some embodiments, proof mass 106 includes a first proof mass portion 110 and a second proof mass portion 112. Figure 1A In the embodiment of the present invention, the first proof mass portion 110 is arranged on one side of the rotation axis 118 and the second proof mass portion is arranged on the opposite side of the rotation axis 118 .

[0025] In some embodiments, proof mass 106 is arranged such that there is a mass imbalance about rotation axis 118. Figure 1A In the illustrative embodiment of , second proof mass portion 112 has a greater mass than first proof mass portion 110. In various other embodiments, proof mass 106 is asymmetric with respect to shape in the xy plane and / or asymmetric with respect to mass distribution. In various embodiments, proof mass 106 also includes openings or other structures arranged to distribute the mass of proof mass 106. Thus, the mass of first proof mass portion 110 and the mass of second proof mass portion 112 are configured such that proof mass 106 pivots in response to acceleration in the z-direction.

[0026] In some embodiments, an asymmetric proof mass may include a non-rectangular shape. Figure 1BThe detection mass 106 shown in the figure can be considered to be arranged in a rectangular shape with a mass imbalance due to the offset of the rotation axis, but other arrangements are also possible. The detection mass may have a mass imbalance due to the asymmetric shape. For example, the detection mass can be arranged in an "L" shape. The "L" shaped detection mass may have a mass imbalance due to the shape of the detection mass. For example, a portion of the detection mass may have an "L" shape, so even if the rotation axis is centered relative to the end of the "L" shaped detection mass, the mass of the "L" shaped detection mass is unbalanced because one side of the detection mass includes an additional portion. Even so, the "L" shaped or any other shaped detection mass may still have an offset rotation axis. In some embodiments, at least one accelerometer including two "L" shaped detection masses may be provided. The two "L" shaped detection masses may be arranged so that their portions have an "L" shape opposite to each other. In this case, as an example, the two opposing "L" shaped detection masses may form a pair, providing a fully differential accelerometer.

[0027] The additional portion of the "L" shaped proof mass may have various arrangements relative to the rotation axis of the proof mass. In some embodiments, the additional portion of the "L" shaped proof mass protrudes from the main portion of the proof mass in a direction parallel to the rotation axis of the proof mass. Alternatively, the additional portion may protrude from the main portion in a direction perpendicular to the rotation axis. The main portion may be rectangular and may be reflection symmetric across the rotation axis. The main portion may surround all anchors of the proof mass.

[0028] In some embodiments, a uniaxial accelerometer includes a sensing and actuating structure. Figure 1A In the illustrative embodiment of the invention, the accelerometer includes a first electrode 114, a second electrode 116, a third electrode 126, and a fourth electrode 128. The third electrode 126 is disposed between the first anchor 108a and the first electrode 114. The fourth electrode 128 is disposed between the first anchor 108a and the second electrode 116. The third electrode 126 and the fourth electrode 128 may be used to create an imbalance of force to at least partially cause the beam to pivot.

[0029] exist Figure 1AIn the illustrative embodiment of , each electrode is coupled to a portion of the proof mass 106. For example, the first electrode 114 is arranged at a variable distance D1 from the first proof mass portion 110, the second electrode 116 is arranged at a variable distance D2 from the second proof mass portion 112, the third electrode 126 is arranged at a variable distance D3 from the first proof mass portion 110, and the fourth electrode 128 is arranged at a variable distance D4 from the second proof mass portion 112. In some embodiments, when the proof mass is stationary, the distances D1, D2, D3, and D4 are the same, but in other embodiments, they can be different. However, the present application is not limited thereto, and the electrodes can be configured in other arrangements, such as on the proof mass 106, or arranged on a different substrate.

[0030] The third electrode 126 and the fourth electrode 128 may include sensing and / or driving electrodes. In some embodiments, the third electrode 126 and the fourth electrode 128 provide a driving function. The third electrode 126 and the fourth electrode 128 may provide a driving signal to the detection mass 106. In some embodiments, the driving signal includes an AC signal and is applied to the detection mass 106 by each of the third and fourth electrodes.

[0031] In some embodiments, the third electrode 126 and the fourth electrode 128 provide a sensing function. For example, the third electrode 126 and the fourth electrode 128 can be configured to provide a sensing signal derived from the displacement of the proof mass 106 relative to the substrate. In some embodiments, the third electrode 126 and the fourth electrode 128 are configured to provide a sensing signal indicating at least one of the distances D3 and D4.

[0032] The single-axis accelerometer 100 may form at least one sensing capacitor. Figure 1A In the illustrative embodiment of , the third electrode 126 faces the first proof mass portion 110 and forms a first sensing capacitor. The fourth electrode 128 faces the second proof mass portion 112 and forms a second sensing capacitor. The portions of the proof mass may be configured such that they include substantially equal sensing areas facing the electrodes.

[0033] When the proof mass 106 is pivoted about the rotation axis, the capacitance of the sensing capacitor can be used to measure the acceleration of the single-axis accelerometer 100. The capacitance of the first sensing capacitor can change as the distance D3 between the first proof mass portion 110 of the pivoting proof mass 106 and the third electrode 126 disposed on the substrate 102 changes. The capacitance of the second sensing capacitor can change as the distance D4 between the second proof mass portion 112 of the pivoting proof mass 106 and the fourth electrode 128 disposed on the substrate 102 changes. The signal derived from the displacement of the proof mass 106 can be used to find the acceleration of the accelerometer along the single axis.

[0034] In some embodiments, the sensing capacitor provides an output signal indicating a change in capacitance due to pivoting of the proof mass 106. In some embodiments, the output signal can be used to determine the acceleration of the uniaxial accelerometer 100. The first and second sensing capacitors can provide a differential signal. Therefore, the third electrode 126 and the fourth electrode 128 can be referred to as differential electrodes. The first sensing capacitor can provide a first capacitance and the second sensing capacitor can provide a second capacitance. The first capacitance and the second capacitance can provide and / or can be compared to provide a differential or pseudo differential signal. That is, as one capacitance increases, the other capacitance may decrease.

[0035] A differential output signal may be obtained from the components of the single-axis accelerometer 100. In some embodiments, the signal may be obtained from the third electrode 126 and the fourth electrode 128. In some embodiments, the detection mass 106 forms an electrode including a first detection mass portion 110 facing the third electrode 126 and a second detection mass portion 112 facing the fourth electrode 128. The first anchor 108a may be electrically coupled to the detection mass. The first anchor 108a may in turn be electrically coupled to a conductive trace or other structure disposed on the substrate 102. Thus, the first anchor 108a may provide an output signal from the detection mass 106 to the trace. The first anchor 108a may be electrically coupled to the conductive trace or other structure disposed on the substrate 102. Figure 1A The first anchor 108a is disposed between a first proof mass portion 110 forming part of a first sensing capacitor and a second proof mass portion 112 forming part of a second sensing capacitor (in the x direction). The first anchor 108a can thus provide a differential signal indicative of a comparison of the signals provided by the first and second sensing capacitors, respectively.

[0036] The signal may be provided to a device disposed on the substrate or to a device external to the substrate. The device may include circuitry configured to process the output signal to determine the acceleration. For example, the device may perform at least one operation on the signal to calculate the acceleration applied to the accelerometer along a single axis. For example, a suitable algorithm may be employed in the logic or processor to calculate the acceleration.

[0037] The substrate 102 has an upper surface 104. The upper surface 104 may be substantially planar. The upper surface 104 of the substrate 102 is disposed between the substrate 102 and the Figure 1A Among the other components of the single-axis accelerometer 100 shown.

[0038] According to aspects of the present application, a substrate such as substrate 102 may include various materials. In some embodiments, the substrate may include a semiconductor material. For example, the substrate may include a bulk or single crystal semiconductor substrate, such as a bulk or single crystal silicon substrate. In some embodiments, the substrate may include a deposited semiconductor substrate, such as polycrystalline silicon. In some embodiments, the substrate may include a silicon-on-insulator substrate or may include a buried oxide layer. Other semiconductor materials may be used as substrates. In some embodiments, a substrate such as substrate 102 may include a printed circuit board (PCB), or a semiconductor material substrate may be mounted to a PCB.

[0039] In some embodiments, the uniaxial accelerometer 100 is a MEMS device. Therefore, various MEMS manufacturing techniques can be used to form the uniaxial accelerometer 100. In addition, in some embodiments, the substrate 102, the proof mass 106, the first anchor 108a, the first electrode 112, the second electrode 114, the third electrode 126 and the fourth electrode 128, any torsion springs, and other components such as the MEMS device can be formed. Figure 1A Other components, such as any components not depicted in the drawings, may be formed of conductor and / or semiconductor materials (e.g., polysilicon, silicon, or metal conductors). If a semiconductor material is used, the material may be appropriately doped to exhibit the desired conductivity. The components may be formed by any suitable manufacturing process.

[0040] Figure 1B A top view of a single-axis accelerometer 100 is shown according to an exemplary embodiment. Figure 1B Elements of the uniaxial accelerometer 100 are depicted, including a proof mass 106, a first anchor 108a, a second anchor 108b, a first proof mass portion 110, a second proof mass portion 112, a first torsion spring 120a, a second torsion spring 120b, a third torsion spring 120c, a fourth torsion spring 120d, a first stress relief structure 122a, a second stress relief structure 122b, and a plurality of high aspect ratio beams 124. The proof mass 106 is configured to pivot about a rotation axis 118 and may be disposed on an upper surface of a substrate (not depicted) including sense and / or drive electrodes (not depicted).

[0041] Proof mass 106 can be configured to accommodate at least two anchors. In some embodiments, the anchors are arranged within the perimeter of proof mass 106 in the xy plane. At least two anchors can also be arranged to be embedded within proof mass 106. For example, proof mass 106 can have a shape formed around the anchors so that the proof mass and the anchors do not overlap in the xy plane. In some embodiments, the proof mass is coupled to the anchors at the inner edge of the proof mass.

[0042] In some embodiments, a single-axis accelerometer includes at least two anchors. For example, Figure 1B A single-axis accelerometer 100 is depicted with two anchors, a first anchor 108a and a second anchor 108b. However, in various embodiments, the single-axis accelerometer can be configured with a different number of anchors, for example, one anchor, two anchors, three anchors, four anchors, five anchors, at least one anchor, at least two anchors, at least three anchor points, at least four anchor points, at least five anchor points, an even number of anchor points, or an odd number of anchor points.

[0043] The increased number of at least two anchors of the uniaxial accelerometer 100 allows for an increased number of torsion springs as compared to conventional single-anchor accelerometers. Thus, increased overall torsional stiffness can be achieved relative to a single anchor accelerometer. Similarly, torsional stiffness can be increased beyond the previously described torsional stiffness limitations caused by the cross-sectional and length limitations of the torsion springs.

[0044] The anchors may be arranged in various arrangements relative to the axis of rotation. Multiple anchors may be arranged in a row along the axis of rotation of the proof mass. Within a row, there may be some offset from the axis of rotation. In some embodiments, there may be multiple rows of anchors, such as two rows of anchors. When the anchors are in multiple rows, there may be two or more anchors at the same coordinate along the axis of rotation, offset from each other in a direction perpendicular to the axis of rotation.

[0045] In some embodiments, the anchors may be arranged along the axis of rotation. The anchors may be arranged, for example, collinearly or in a straight line along the axis. Collinear anchors are less sensitive to environmental stresses and / or shear. In some embodiments, the anchors are arranged to be symmetrical in at least one manner. In some embodiments, the anchors are arranged to be reflectively symmetrical across the axis of rotation. The anchors may be arranged to be reflectively symmetrical across an axis that bisects the proof mass in a direction perpendicular to the axis of rotation. In some embodiments, the bisector axis may bisect the proof mass at equal distances from two opposing outer edges along the axis of rotation. In some embodiments, the bisector axis may bisect the proof mass with equal masses on either side of the bisector. Alternatively or additionally, a bisector axis may be equidistant from the two outermost anchors of the proof mass, regardless of the outer edges or the arrangement of the proof mass. In some embodiments, the anchors are arranged to be rotationally symmetrical about a point where the axis of rotation intersects an axis that bisects the proof mass in a direction perpendicular to the axis of rotation. For example, the anchors may be rotationally symmetrical 180 degrees about the point.

[0046] In some embodiments, an anchor may be provided on the axis of rotation. For a z-axis accelerometer, an anchor disposed on the axis of rotation may coincide with the axis of rotation and / or may be disposed to overlap the axis of rotation in the xy plane.

[0047] In some embodiments, the anchor may be offset from the axis of rotation. For example, in the plane of the upper surface of the substrate, the anchor may be offset from the axis of rotation in a direction perpendicular to the axis of rotation. For a z-axis accelerometer, the anchor disposed offset from the axis of rotation may not coincide with the axis of rotation and / or may be disposed not to overlap with the axis of rotation in the xy plane.

[0048] The anchors in the plurality of anchors may be arranged at different distances from each other. For example, each anchor may be arranged at the same center-to-center distance along the axis of rotation. In some embodiments, the center-to-center distance of the anchors is less than the distance from the center of the outermost anchor to the perimeter of the proof mass along the axis of rotation. However, other arrangements are possible, and the center-to-center distance and the distance to the perimeter of the proof mass may vary.

[0049] exist Figure 1B In the illustrative embodiment of , the first anchor 108a and the second anchor 108b are arranged to be co-linear with each other and on the rotation axis 118. Figure 1B In , the first anchor 108a and the second anchor 108b are arranged together to be reflection symmetric across the rotation axis, reflection symmetric along an axis bisecting the proof mass in a direction perpendicular to the rotation axis, and 180 degrees rotationally symmetric about a point at the intersection of the rotation axis and the axis bisecting the proof mass in a direction perpendicular to the rotation axis. Figure 1B , the bisector axis bisects the proof mass 106 along the axis of rotation at an equal distance from the two opposing outer edges and at equal masses on either side of the bisector, and is also equidistant from the outermost anchors of the proof mass 106 .

[0050] In some embodiments, each anchor is coupled to the proof mass 106 via at least one torsion spring. Figure 1B In the illustrative embodiment of , the first anchor 108a and the second anchor 108b are each coupled to the proof mass by two respective torsion springs. Other arrangements are possible, and each anchor may also be coupled to the proof mass 106 by at least two torsion springs, such as three or four torsion springs.

[0051] In some embodiments, each of the plurality of springs is disposed extending along the rotation axis 118. For example, Figure 1BIn the embodiment of the present invention, each of the first torsion spring 120a, the second torsion spring 120b, the third torsion spring 120c and the fourth torsion spring 120d includes at least one section extending along the rotation axis 118. The torsion spring can be a spring that is configured to allow relative rotational motion around the rotation axis between elements coupled to the ends of the torsion spring in response to a torque applied around the rotation axis and / or can be substantially rigidly rotated around other axes or other types of motion. Typically, the torsion spring in the accelerometer has a specifically designed torsional stiffness. The torsional stiffness may depend on factors such as the material properties of the torsion spring, the cross-section of the torsion spring, and the length of the torsion spring.

[0052] The torsion springs may be arranged in various arrangements relative to the axis of rotation. Multiple torsion springs may be arranged in a row along the axis of rotation of the proof mass. Within a row, there may be some offset from the axis of rotation. In some embodiments, there may be multiple rows of torsion springs, for example, two rows of torsion springs.

[0053] In some embodiments, the torsion springs may be arranged along the axis of rotation. The torsion springs may be arranged, for example, co-linearly or in a straight line along the axis. In some embodiments, the torsion springs are arranged symmetrically in at least one manner. In some embodiments, the torsion springs are arranged to be reflectively symmetrical across the axis of rotation. The torsion springs may be arranged to be reflectively symmetrical across an axis that bisects the proof mass in a direction perpendicular to the axis of rotation. In some embodiments, the torsion springs are arranged to be rotationally symmetrical about a point at the intersection of the axis of rotation and an axis that bisects the proof mass in a direction perpendicular to the axis of rotation. For example, the torsion springs may be rotationally symmetrical 180 degrees around the point. A symmetrical spring may symmetrically distribute impact stresses to the spring.

[0054] In some embodiments, the torsion spring includes a torsion spring segment that extends along the axis of rotation and can be arranged substantially parallel to the axis of rotation. At least one torsion spring segment of the torsion spring can be straight and can be configured to twist around its own elongated axis, which can be aligned with the axis of rotation. When the torsion spring includes at least one straight torsion spring segment configured to twist around its elongated axis, particularly when the straight segment comprises a major portion of the torsion spring, the torsion spring can be considered a straight torsion spring. In some embodiments, the torsion spring segment extending along the axis can be configured to allow relative rotational movement between the ends of the torsion spring along the axis in response to a torque applied around the axis.

[0055] The torsion spring may include other types of torsion springs. In some embodiments, the torsion spring may include a folding spring configured to allow rotation around an axis of rotation. The torsion spring may also include a serpentine structure and / or may include at least one element having an "S" shape.

[0056] In some embodiments, at least one torsion spring segment of a torsion spring extending along the rotation axis may be arranged on the rotation axis. The torsion spring segment arranged on the rotation axis may coincide with the rotation axis and / or may be arranged to overlap with the rotation axis of the z-axis accelerometer in the xy plane. The torsion spring including the torsion spring segment may be considered to be arranged on the axis.

[0057] In some embodiments, the torsion spring includes a torsion spring segment that extends along the rotation axis and can be offset from the rotation axis. For example, the torsion spring can be offset from the rotation axis in a plane of the upper surface of the substrate in a direction perpendicular to the rotation axis. For a z-axis accelerometer, the torsion spring segment that is arranged offset from the rotation axis can not coincide with the rotation axis and / or can be arranged not to overlap with the rotation axis in the xy plane. It can be considered that the torsion spring including the torsion spring segment is arranged offset from the axis.

[0058] exist Figure 1B In the illustrative embodiment of , the first torsion spring 120a, the second torsion spring 120b, the third torsion spring 120c, and the fourth torsion spring 120d are arranged to be colinear with each other and on the rotation axis. Figure 1B , the first torsion spring 120a, the second torsion spring 120b, the third torsion spring 120c and the fourth torsion spring 120d are arranged together to be reflection symmetric about the rotation axis, reflection symmetric through an axis that bisects the detection mass block in a direction perpendicular to the rotation axis, and 180 degrees rotationally symmetric about a point at the intersection of the rotation axis and the axis that bisects the detection mass block in a direction perpendicular to the rotation axis.

[0059] In some embodiments, a single-axis accelerometer may include at least one stress relief structure. Figure 1B , the proof mass 106 includes a first stress relief structure 122a and a second stress relief structure 122b, each including a plurality of high aspect ratio beams 124. Each stress relief structure can be configured to relieve stress that occurs in the proof mass 106 due to twisting or bending of the torsion spring when the proof mass 106 is bent, rotated, or twisted. The stress relief structures can be formed by etching the proof mass. The stress relief structures, including the high aspect ratio beams, can extend all or part of the way through the proof mass in which they are formed.

[0060] The stress relief structure can be arranged in various configurations relative to the anchors and torsion springs. In some embodiments, the stress relief structure is arranged adjacent to the outermost torsion spring along the rotation axis. The stress relief structure can be arranged between the outermost anchor and / or the outermost torsion spring and the periphery of the proof mass. In some embodiments, multiple anchors and / or multiple torsion springs are arranged between the first stress relief structure and the second stress relief structure.

[0061] The stress relief structure can extend at various distances in a direction perpendicular to the axis of rotation. Figure 1B In the embodiment, the first stress relief structure 122a and the second stress relief structure 122b extend in the x-direction to substantially the same distance from the rotation axis 118 as the plurality of anchors and the plurality of torsion springs. However, the stress relief structures may extend beyond or not to the extent that the plurality of anchors and / or torsion springs extend. When the anchors and / or torsion springs are arranged in multiple rows, each row may have a separate corresponding pair of stress relief structures, or a pair of stress relief structures may extend to substantially the same distance from the rotation axis of the outermost row.

[0062] In some embodiments, each stress relief structure can include a plurality of high aspect ratio beams. Figure 1B In the illustrative embodiment of the present invention, the first stress relief structure 122a and the second stress relief structure 122b each include a plurality of high aspect ratio beams 124 arranged to extend along the rotation axis 112. The high aspect ratio beams 124 may have a smaller cross-section than the torsion springs and a greater length than the torsion springs. Therefore, the individual high aspect ratio beams 124 may have a lower torsional stiffness than the torsion springs. The length of the high aspect ratio beams 124 may increase as the number of anchors and torsion springs decreases, and may decrease as the number of anchors and torsion springs increases.

[0063] Figure 1C 1 shows a top detailed plan view of the proof mass 106 and anchor 108a of the uniaxial accelerometer 100 according to an exemplary embodiment. However, similar Figure 1C 108b or 109b. Figure 2 Anchors in the following) and other proof masses (e.g., Figure 2 detection mass as described above). Figure 1C The illustrative embodiment of FIG. 1 additionally shows a first torsion spring 120 a and a second torsion spring 120 b. Although the torsion spring is shown as part of the uniaxial accelerometer 100 , other torsion springs described below (eg, in connection with the uniaxial accelerometer 200 ) may be used in conjunction with the uniaxial accelerometer 100 . Figure 1C The arrangement of the first torsion spring 120a and the second torsion spring 120b in FIG. 1 is similarly arranged. The first torsion spring 120a couples the first anchor 108a to the proof mass 106. The first torsion spring is arranged on a first side of the anchor 108a. The second torsion spring 120b couples the first anchor 108a to the proof mass 106. The second torsion spring 120b is arranged on a second side of the first anchor 108a. In various embodiments, the torsion springs may be arranged on a first side and a second side of the anchor. In some embodiments, the first side and the second side may be different sides, or may be opposite sides of the anchor.

[0064] In some embodiments, at least three torsion springs can be coupled to a single anchor. For example, two torsion springs can be arranged on opposite sides of a first anchor, for a total of four springs for the first anchor. A first torsion spring on a first side of the first anchor can be collinear with a second torsion spring on a second side of the first anchor, and a third torsion spring on a first side of the first anchor can be collinear with a fourth torsion spring on a second side of the first anchor. This pattern of at least three torsion springs is applied to additional anchors, whose corresponding springs can also be collinear with the springs of the first anchor. Thus, there can be two sets of collinear torsion springs arranged along a set of anchors, each anchor having four springs.

[0065] The torsion springs can have various sizes depending on the number of anchors in the accelerometer and the target operating frequency of the accelerometer. For example, an accelerometer with a target operating frequency of about 20 kHz may include two anchors, each with two torsion springs. Each torsion spring has a length L of 32 micrometers (um) in the y direction, a width W of 12 um in the x direction, and a thickness T of 16 um in the z direction (into and / or out of the page). The accelerometer may have a proof mass length of 920 um in the y direction, a proof mass width of 740 um in the x direction, and a stress relief length of 250 um in the y direction.

[0066] As another example, an accelerometer with a target operating frequency of about 30 kHz may include three anchors, each with two torsion springs. Each torsion spring has a length L of 25 um in the y direction, a width W of 15 um in the x direction, and a thickness T of 16 um in the z direction. The accelerometer may have a proof mass width of 920 um in the y direction, a proof mass width of 740 um in the x direction, and a stress relief length of 200 um in the y direction.

[0067] As yet another example, an accelerometer with a target operating frequency of about 39 kHz may include four anchors, each anchor having two torsion springs. Each torsion spring has a length L of 17 um in the y direction, a width W of 21 um in the x direction, and a thickness T of 16 um in the z direction. The accelerometer may have a proof mass width of 920 um in the y direction, a proof mass width of 740 um in the x direction, and a stress relief length of 160 um in the y direction.

[0068] As a final example, an accelerometer with a target operating frequency of about 43 kHz may include five anchors, each with two torsion springs. Each torsion spring has a length L of 17 um in the y direction, a width W of 23 um in the x direction, and a thickness T of 16 um in the z direction. The accelerometer may have a proof mass width of 920 um in the y direction, a proof mass width of 740 um in the x direction, and a stress relief length of 120 um in the y direction.

[0069] Figure 2 A top view of a single-axis accelerometer 200 according to an exemplary embodiment is shown. The single-axis accelerometer 200 includes a proof mass 206, a first anchor 208a, a second anchor 208b, a third anchor 208c, a fourth anchor 208d, a fifth anchor 208e, a first proof mass portion 210, a second proof mass portion 212, a first torsion spring 220a, a second torsion spring 220b, a third torsion spring 220c, a fourth torsion spring 220d, a fifth torsion spring 220e, a sixth torsion spring 220f, a seventh torsion spring 220g, an eighth torsion spring 220h, a ninth torsion spring 220i, a tenth torsion spring 220j, a first stress relief structure 222a, a second stress relief structure 222b, and a plurality of high aspect ratio beams 224. The proof mass 206 is configured to pivot about a rotation axis 218 and may be disposed on an upper surface of a substrate (not depicted) including sensing and / or drive electrodes (not depicted).

[0070] Proof mass 206 differs from proof mass 106 in that proof mass 206 is configured to accommodate five anchors and corresponding torsion spring pairs instead of two anchors and corresponding torsion spring pairs. Similarly, first proof mass portion 210 and second proof mass portion 212 differ from first proof mass portion 110 and second proof mass portion 112, respectively, in that first proof mass portion 210 and second proof mass portion 212 are configured to accommodate five anchors and corresponding torsion spring pairs instead of two anchors and corresponding torsion spring pairs.

[0071] exist Figure 2 In the illustrative embodiment of FIG. 1 , the first anchor 208 a, the second anchor 208 b, the third anchor 208 c, the fourth anchor 208 d, and the fifth anchor 208 e are arranged in a row along the rotation axis 218 of the proof mass 206. Figure 2In the embodiment of the present invention, the first anchor 208a, the third anchor 208c and the fifth anchor 208e are arranged on one side of the rotation axis 218, while the second anchor 208b and the fourth anchor 208d are arranged on the opposite side of the rotation axis 218. In this way, the anchors and their respective springs can be alternately arranged on both sides of the rotation axis. However, the arrangement of the anchors is not limited in this regard, and various other patterns can be utilized. For example, a pair of continuous anchors can be arranged on one side, while another pair of continuous anchors can be arranged on the opposite side.

[0072] The uniaxial accelerometer 200 having an increased number of five anchors and corresponding torsion springs compared to the two anchors and corresponding torsion springs of the uniaxial accelerometer 100 may be adapted for target operating frequencies higher than the target operating frequency of the uniaxial accelerometer 100 .

[0073] exist Figure 2 In , the anchors are arranged to have an offset from the rotation axis 218. For example, the first anchor 208a and its corresponding spring are arranged to have an offset F1 from the rotation axis in the x direction. Since the anchor points are offset from each other in the x direction, the rotation axis may fall between the anchor points in the x direction. Figure 2 In , the anchors are arranged together in reflection symmetry across an axis that bisects the proof mass in a direction perpendicular to the rotation axis.

[0074] exist Figure 2 In the illustrative embodiment of , each anchor is coupled to the proof mass by two corresponding torsion springs arranged extending along the rotation axis. Similar to the anchors, the torsion springs are arranged offset from the rotation axis 218. The first torsion spring 220a, the second torsion spring 220b, the fifth torsion spring 220e, the sixth torsion spring 220f, the ninth torsion spring 220i and the tenth torsion spring 220j are arranged on one side of the rotation axis 218, while the third torsion spring 220c, the fourth torsion spring 220d, the seventh torsion spring 220g and the eighth torsion spring 220h are arranged on the other side of the rotation axis.

[0075] exist Figure 2 In the illustrative embodiment of the present invention, the first stress relief structure 222a and the second stress relief structure 222b include a plurality of high aspect ratio beams 224 and form a single pair of stress relief structures that extend in the x-direction to a distance substantially the same as the extension distance of the outermost anchors and torsion springs. The first stress relief structure 222a and the second stress relief structure 222b differ from the first stress relief structure 122a and the second stress relief structure 122b in that they extend a shorter distance in the y-direction to accommodate the five anchor points and extend a greater distance in the x-direction to accommodate the offset of the anchor points. Similarly, the high aspect ratio beams 224 differ from the high aspect ratio beams 124 in that they extend a smaller distance in the y-direction.

[0076] In some embodiments, a system can include at least two detection masses. For example, a single accelerometer can include at least two detection masses. Alternatively, a system can include at least two accelerometers, each of which includes a detection mass disposed on the same substrate. For example, such a system can include six detection masses. Each detection mass can be configured as described above. In some embodiments, at least two detection masses can be configured to pivot around at least two different rotation axes. In some embodiments, at least two different rotation axes can be arranged to be non-parallel to each other, such as perpendicular to each other.

[0077] Figure 3 A non-limiting example is shown in which at least one accelerometer of the type described herein is employed in a car. Figure 3 In an example of a vehicle 300, a car 300 includes a control unit 302 coupled to an onboard computer 304 of the car via a wired or wireless connection. The control unit 302 may include at least one accelerometer of the type described herein. As a non-limiting example, at least one accelerometer may sense acceleration in a driving direction and / or perpendicular to the driving direction. At least one accelerometer may also be configured to sense vertical acceleration, which may be useful, for example, for monitoring a suspension state of the car 300. The control unit 302 may receive power and control signals from the onboard computer 304 and may provide output signals of the type described herein to the onboard computer 304.

[0078] Figure 4 A system 400 is illustrated, which includes three uniaxial MEMS accelerometers 402a, 402b, and 402c coupled to a piece of industrial equipment 404, one or more of which are of the type described herein. Equipment 404 may be a motor, although this is a non-limiting example. Accelerometers 402a, 402b, and 402c may be coupled to the equipment and configured to monitor the vibration of the equipment relative to the corresponding axis. For example, accelerometer 402a may be oriented to detect z-axis acceleration, y-axis acceleration accelerometer 402b, and x-axis acceleration accelerometer 402c. In an alternative embodiment, in contrast to the illustrated configuration of three different housings, two or more of accelerometers 402a, 402b, and 402c may be combined into a single package or housing. The system may wirelessly transmit acceleration data generated by the corresponding accelerometers. Energy for powering the accelerometer circuit may be collected from the vibration of equipment 404. Other configurations are also possible.

[0079] Various aspects of the present application may provide one or more benefits. Some examples are now listed. It should be understood that not all aspects necessarily provide all benefits, and benefits other than those listed may be provided by one or more aspects. According to some aspects of the present application, increased stiffness of a single-axis swing accelerometer is provided. The increased stiffness may be particularly significant or beneficial at high operating frequencies. For example, a swing accelerometer operating at frequencies between 2kHz and 100kHz, but particularly above about 20kHz (or any value within these ranges, as non-limiting examples), may exhibit increased stiffness compared to conventional designs.

[0080] Having thus described several aspects and embodiments of the technology of the present application, it will be appreciated that a person of ordinary skill in the art will readily conceive of various changes, modifications, and improvements. Such changes, modifications, and improvements are intended to be within the spirit and scope of the technology described in the present application. Therefore, it will be appreciated that the foregoing embodiments are presented only by way of example, and within the scope of the appended claims and their equivalents, embodiments of the present invention may be practiced in a manner other than that specifically described. In addition, any combination of two or more features, systems, articles, materials, and / or methods described herein, if such features, systems, articles, materials, and / or methods are not mutually contradictory, is included within the scope of the present disclosure.

[0081] Moreover, as described, some aspects may be embodied as one or more methods. The actions performed as part of the method may be ordered in any suitable manner. Thus, embodiments may be configured to perform actions in a different order than shown, which may include performing some actions simultaneously, even though shown as sequential actions in the illustrative embodiments.

[0082] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0083] The terms "approximately," "substantially," and "roughly" may be used in some embodiments to mean within ±20% of a target value, in some embodiments to mean within ±10% of a target value, in some embodiments to mean within ±5% of a target value, and in some embodiments to mean within ±2% of a target value. The terms "approximately" and "roughly" may include the target value.

Claims

1. A single-axis swing MEMS accelerometer, comprising: substrate; a proof mass suspended above the substrate; and a plurality of anchors coupling the proof mass to the substrate, wherein each of at least two anchors of the plurality of anchors is coupled to an inner edge of the proof mass by two respective in-line torsion springs, The plurality of anchors include a plurality of first anchors and at least one second anchor, the plurality of first anchors are arranged in a straight line with each other on the rotation axis of the detection mass block, and the at least one second anchor is arranged to deviate from the rotation axis of the detection mass block.

2. A single-axis swing MEMS accelerometer, comprising: substrate; a proof mass suspended above the substrate; and a plurality of anchors coupling the proof mass to the substrate, wherein each of at least two anchors of the plurality of anchors is coupled to an inner edge of the proof mass by two respective in-line torsion springs, The plurality of anchors include a plurality of first anchors and at least one second anchor, the plurality of first anchors are arranged in a straight line with each other and offset from the rotation axis of the detection mass block, and the at least one second anchor is arranged offset from the rotation axis of the detection mass block.

3. The single-axis oscillating MEMS accelerometer of claim 1 or 2, wherein the plurality of anchors comprises three anchors, and wherein each of the three anchors is coupled to an inner edge of the proof mass by two corresponding in-line torsion springs.

4. The single-axis oscillating MEMS accelerometer of claim 1 or 2, wherein the at least one second anchor comprises a plurality of second anchors.

5. The single-axis oscillating MEMS accelerometer of claim 1 or 2, wherein the plurality of anchors and the torsion spring are reflection symmetric across an axis that bisects the proof mass in a direction perpendicular to the rotation axis.

6. The single-axis oscillating MEMS accelerometer of claim 1 or 2, wherein each of at least two anchors of the plurality of anchors is coupled to an inner edge of the proof mass by at least three corresponding in-line torsion springs.

7. The single-axis oscillating MEMS accelerometer of claim 1 or 2, wherein the detection mass is a first detection mass, and the single-axis oscillating MEMS accelerometer further comprises a second detection mass suspended above the substrate.

8. The single-axis oscillating MEMS accelerometer of claim 7, wherein the rotational axis is a first rotational axis; and The second proof mass has a second rotation axis perpendicular to the first rotation axis.

9. A single-axis swing MEMS accelerometer, comprising: substrate; a proof mass suspended above the substrate; a plurality of anchors coupling the proof mass to the substrate; and a plurality of torsion springs coupling the plurality of anchors to the proof mass, each anchor of the plurality of anchors being coupled to the proof mass by at least two corresponding torsion springs; Wherein at least one anchor of the plurality of anchors is offset from the rotation axis of the proof mass in a direction perpendicular to the rotation axis of the proof mass.

10. The single-axis oscillating MEMS accelerometer of claim 9, wherein the plurality of anchors comprises three anchors and the plurality of torsion springs comprises six in-line torsion springs.

11. The single-axis oscillating MEMS accelerometer of claim 9, wherein the plurality of anchors and the torsion spring are reflection symmetric across an axis that bisects the proof mass in a direction perpendicular to the rotational axis.

12. The single-axis oscillating MEMS accelerometer of claim 9, further comprising a stress relief structure disposed on the rotation axis between a first anchor of the plurality of anchors and a periphery of the proof mass.

13. The uniaxial oscillating MEMS accelerometer of claim 9, further comprising a first stress relief structure and a second stress relief structure; Each of the plurality of anchors is disposed between the first stress relief structure and the second stress relief structure.

14. A single-axis swing MEMS accelerometer, comprising: substrate; a proof mass suspended above the substrate; a plurality of anchors arranged along the rotational axis of the proof mass, disposed within a perimeter of the proof mass, and coupling the proof mass to the substrate, the plurality of anchors comprising a first anchor and a second anchor; a first torsion spring extending along the rotational axis and coupling the proof mass to the first anchor, the first torsion spring being disposed on a first side of the first anchor; a second torsion spring extending along the rotational axis and coupling the proof mass to the first anchor, the second torsion spring being disposed on a second side of the first anchor different from the first side of the first anchor; a third torsion spring extending along the rotational axis and coupling the proof mass to the second anchor, the third torsion spring being disposed on a first side of the second anchor; a fourth torsion spring extending along the rotational axis and coupling the proof mass to the second anchor, the fourth torsion spring being disposed on a second side of the second anchor different from the first side of the second anchor, At least one anchor of the plurality of anchors is offset from the rotational axis of the proof mass in a direction perpendicular to the rotational axis.

15. The single-axis oscillating MEMS accelerometer of claim 14, wherein the plurality of anchors and the torsion springs coupled thereto are reflection symmetric across an axis that bisects the proof mass in a direction perpendicular to the rotational axis.

16. The single-axis oscillating MEMS accelerometer of claim 14, wherein the plurality of anchors are embedded in the proof mass.

17. The single-axis oscillating MEMS accelerometer of claim 14, wherein the at least one anchor comprises a plurality of second anchors aligned with one another parallel to the rotational axis of the proof mass.

18. The single-axis oscillating MEMS accelerometer of claim 14, wherein the plurality of anchors comprises a plurality of first anchors, the plurality of first anchors being aligned with one another on the rotation axis of the proof mass.

19. The single-axis pendulum MEMS accelerometer of claim 14, wherein the proof mass is a first proof mass, the single-axis pendulum MEMS accelerometer further comprising a second proof mass suspended above the substrate.

20. The single-axis oscillating MEMS accelerometer of claim 19, wherein the rotational axis is a first rotational axis; and The second proof mass has a second rotational axis that is non-parallel to the first rotational axis.

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