Vibration rectification error correction device, sensor module and method thereof

Abstract

A vibration rectification error correction device, a sensor module, and a method thereof, in order to generate data synchronized with a signal that is not synchronized with a reference signal, do not require a large circuit size synchronization circuit or a heavy load operation. The vibration rectification error correction device includes a reference signal generation circuit that outputs a reference signal; a frequency delta sigma modulation circuit that frequency delta sigma modulates the reference signal using a measured signal to generate a frequency delta sigma modulation signal; a first filter that is provided at a subsequent stage of the frequency delta sigma modulation circuit and that operates in synchronization with the measured signal; and a second filter that is provided at a subsequent stage of the first filter and that operates in synchronization with a first frequency signal that is not synchronized with the reference signal.

Description

Technical Field

[0001] This invention relates to a vibration rectification error correction device, a sensor module, and a vibration rectification error correction method. Background Technology

[0002] Patent Document 1 describes a sensor module configured to synchronize the operation of a first low-pass filter with the output signal of a physical quantity sensor, and to perform resampling synchronized with a reference clock via a subsequent second low-pass filter. According to this sensor module, nonlinear characteristics are generated in the overall input and output of the low-pass filter, and the vibration rectification error caused by these nonlinear characteristics is adjusted to be in opposite phase to the vibration rectification error generated by the cantilever resonance of the physical quantity sensor. This cancels out the vibration rectification errors and reduces the vibration rectification error in the final output.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-190897

[0004] In the sensor module described in Patent Document 1, since the second low-pass filter operates synchronously with the reference clock, for example, in order to obtain data that is synchronized with a signal that is not synchronized with the reference clock such as an external trigger signal, a large-scale synchronization circuit or a heavy-load post-processing operation is required after the second low-pass filter. Summary of the Invention

[0005] One aspect of the vibration rectification error correction device according to the present invention comprises:

[0006] The reference signal generation circuit outputs a reference signal;

[0007] A frequency ΔΣ modulation circuit uses the measured signal to modulate the reference signal at a frequency ΔΣ to generate a frequency ΔΣ modulated signal.

[0008] A first filter, disposed after the frequency ΔΣ modulation circuit, operates synchronously with the signal being measured; and

[0009] The second filter, located after the first filter, operates synchronously with a first frequency signal that is not synchronized with the reference signal.

[0010] One embodiment of the sensor module involved in this invention comprises:

[0011] One method of the vibration rectification error correction device; and

[0012] Physical quantity sensor.

[0013] One aspect of the vibration rectification error correction method involved in this invention includes:

[0014] The process of using the measured signal to modulate the reference signal at a frequency ΔΣ to generate a frequency ΔΣ modulated signal.

[0015] The step of performing a first filtering process on the signal based on the frequency ΔΣ modulation signal synchronously with the measured signal; and

[0016] The process of performing a second filtering process on a signal based on the signal obtained through the first filtering process, in sync with a first frequency signal that is not synchronized with the reference signal. Attached Figure Description

[0017] Figure 1 This is a 3D view of the sensor module.

[0018] Figure 2 This is an exploded 3D view of the sensor module.

[0019] Figure 3 It is a 3D view of a physical quantity sensor.

[0020] Figure 4 This is a top view of a physical quantity sensor.

[0021] Figure 5 yes Figure 4 A cross-sectional view of line P1-P1.

[0022] Figure 6 This is an explanatory diagram of the operation of a physical quantity sensor.

[0023] Figure 7 This is an explanatory diagram of the operation of a physical quantity sensor.

[0024] Figure 8 This is a functional block diagram of the sensor module in the first embodiment.

[0025] Figure 9 This diagram illustrates, in principle, the vibration rectification error caused by the distortion of the output waveform.

[0026] Figure 10 It is a graph representing the nonlinear characteristics of the applied acceleration versus the reciprocal count value.

[0027] Figure 11 It is a graph representing the nonlinear characteristics of the applied acceleration and the oscillation frequency of the physical quantity sensor.

[0028] Figure 12 This is a graph representing the nonlinear characteristics of the oscillation frequency and reciprocal count value of a physical quantity sensor.

[0029] Figure 13 This is a diagram illustrating an example of the configuration of the frequency ratio measuring circuit in the first embodiment.

[0030] Figure 14 This is a diagram illustrating an example of the configuration of a first low-pass filter.

[0031] Figure 15 This is a diagram showing other configuration examples of the first low-pass filter.

[0032] Figure 16 This is a diagram illustrating an example of the construction of a second low-pass filter.

[0033] Figure 17 This is a diagram used to illustrate the vibration rectification error caused by the nonlinear characteristics of the input and output of the frequency ratio measuring circuit.

[0034] Figure 18 This is a graph showing the dependence of the vibration rectification error included in the measurement value on the number of taps.

[0035] Figure 19 This is a diagram illustrating other configuration examples of the frequency ratio measuring circuit in the first embodiment.

[0036] Figure 20 This is a diagram showing other configuration examples of the first low-pass filter.

[0037] Figure 21 This is a timing diagram of the input and output count values ​​of the FIFO register.

[0038] Figure 22 This is a flowchart illustrating an example of the sequence of the vibration rectification error correction method in the first embodiment.

[0039] Figure 23 This is a functional block diagram of the sensor module in the second embodiment.

[0040] Figure 24 This is a diagram illustrating an example of the configuration of the frequency ratio measuring circuit in the second embodiment.

[0041] Figure 25 This is a diagram illustrating other configuration examples of the frequency ratio measuring circuit in the second embodiment.

[0042] Figure 26 This is a flowchart illustrating an example of the sequence of the vibration rectification error correction method in the second embodiment.

[0043] Figure 27 This is a functional block diagram of the sensor module in a modified example.

[0044] Figure 28 This is a functional block diagram of the sensor module for other variations.

[0045] Explanation of reference numerals in the attached figures

[0046] 1…Sensor module; 2…Vibration rectification error correction device; 3…Processing device; 5…Base plate; 10…Base; 12…Connecting part; 13…Modible part; 30a, 30b…Support part; 34…Encapsulation joint; 36a, 36b…Joint; 38a, 38b…Extension; 40…Physical quantity detection element; 50, 52, 54, 56…Counterweight; 62…Jointing component; 101…Container; 102…Lid; 103…Threaded hole; 104…Fixing protrusion; 111…Side wall; 112…Bottom wall; 115…Circuit Substrate; 115f…first surface; 115r…second surface; 116…connector; 121…opening; 122…inner surface; 123…opening face; 125…second base; 127…first base; 129…protrusion; 130…fixing component; 133, 134…neck; 141…sealing component; 172…screw; 174…internal thread; 176…through hole; 200, 200X, 200Y, 200Z…physical quantity sensor; 201X, 201Y, 201Z…oscillation circuit; 202, 202 X, 202Y, 202Z… Frequency ratio measurement circuit; 203… Reference signal generation circuit; 210… Microcontroller unit; 220… Storage unit; 230… Interface circuit; 240… Multiplier circuit; 250… Frequency signal generation circuit; 300… Frequency ΔΣ modulation circuit; 301… Counter; 302… Latch circuit; 303… Latch circuit; 304… Subtractor; 310… First low-pass filter; 311… Delay element; 312… Integrator; 313… Integrator; 314… Decimator; 315… Delay element; 316… Differentiator; 317… Delay element; 318… Differentiator; 320… Latch circuit; 330… Second low-pass filter; 331… Integrator; 332… Delay element; 333… Differentiator; 334… Decimator; 340… FIFO register; 350… Latch circuit; 401… Integrator; 402… Delay element; 403… Differentiator; 404… Integrator; 405… Integrator; 406… Decimator; 407… Delay element; 408… Differentiator; 409… Delay element; 410… Differentiator. Detailed Implementation

[0047] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the embodiments described below are not intended to unduly limit the scope of the invention as defined in the claims. Additionally, not all of the components described below are essential elements of the present invention.

[0048] 1. First Implementation Method

[0049] 1-1. Structure of the sensor module

[0050] First, an example of the structure of the sensor module in this embodiment will be described.

[0051] Figure 1 This is a perspective view of the sensor module 1 as seen from the mounting surface where it is fixed. In the following description, the direction along the long side of the rectangular sensor module 1 when viewed from above is defined as the X-axis, the direction orthogonal to the X-axis when viewed from above is defined as the Y-axis, and the thickness direction of the sensor module 1 is defined as the Z-axis.

[0052] The sensor module 1 is a rectangular cuboid with a long side along the X-axis and a short side along the Y-axis, which is orthogonal to the X-axis. Threaded holes 103 are formed at two locations near each end of one long side and at one location in the center of the other long side. It is used to fix the sensor to the mounting surface of a structure, such as a building, bulletin board, or various devices, by inserting fixing screws into the threaded holes 103 at these three locations.

[0053] like Figure 1 As shown, an opening 121 is provided on the surface of the sensor unit 1 as viewed from the mounting surface. A plug-type connector 116 is disposed inside the opening 121. The connector 116 has multiple pins arranged in two rows, with the pins in each row arranged along the Y-axis. The connector 116 connects to a socket-type connector (not shown) from the mounting body to transmit and receive electrical signals such as drive voltage and detection data of the sensor module 1.

[0054] Figure 2 This is an exploded 3D view of sensor module 1. (See image below.) Figure 2 As shown, the sensor module 1 consists of a container 101, a cover 102, a sealing member 141, and a circuit board 115. In detail, the sensor module 1 is configured such that the circuit board 115 is mounted inside the container 101 by means of a fixing member 130, and the opening of the container 101 is covered by the cover 102, which is separated by a cushioning sealing member 141.

[0055] Container 101 is, for example, a container for a box-shaped circuit board 115 formed from aluminum with an internal space. The shape of container 101 is similar to the overall shape of the sensor module 1 described above; it is a planar, approximately rectangular cuboid. Fixing protrusions 104 are provided at two locations near the ends of one long side and at one location in the center of the other long side. Threaded holes 103 are formed in each of these fixing protrusions 104.

[0056] Container 101 is a box-shaped container with a cuboid shape and an opening on one side. The interior of container 101 is an internal space enclosed by a bottom wall 112 and a side wall 111. In other words, container 101 is box-shaped with the side opposite to the bottom wall 112 serving as the opening surface 123. The outer edge of the circuit board 115 is arranged along the inner surface 122 of the side wall 111, and a cover 102 is fixed to cover the opening. On the opening surface 123, at two locations near the two ends of one long side of container 101 and at one location in the center of the other long side, a fixing protrusion 104 is erected. Moreover, the upper surface of the fixing protrusion 104, that is, the surface exposed in the -Z direction, protrudes from the upper surface of container 101.

[0057] Additionally, within the interior space of container 101, at the center of one of the long sides opposite to the fixing protrusion 104 located at the center of the other long side, a protrusion 129 is provided, protruding from the side wall 111 toward the interior space between the bottom wall 112 and the opening surface 123. The upper surface of the protrusion 129 is provided with an internal thread 174. The cover 102 is fixed to container 101 via the sealing member 141 by screws 172 inserted into the through hole 176 and the internal thread 174. Furthermore, the protrusion 129 and the fixing protrusion 104 are positioned opposite to the necks 133 and 134 of the circuit board 115, which will be described later.

[0058] Inside the container 101, a first base 127 and a second base 125 are provided, both protruding in a stepped manner from the bottom wall 112 toward the opening surface 123. The first base 127 is positioned opposite the configuration area of ​​a plug-type connector 116 mounted on the circuit board 115. The first base 127 is provided with... Figure 1 The opening 121 shown is into which a plug-type connector 116 is inserted. The first base 127 functions as a base for fixing the circuit board 115 to the container 101.

[0059] The second base 125 is located on the opposite side of the first base 127 relative to the fixing protrusions 104 and 129 located at the center of the long side, and is disposed near the fixing protrusions 104 and 129. The second base 125, located on the opposite side of the first base 127 relative to the fixing protrusions 104 and 129, functions as a base for fixing the circuit board 115 to the container 101.

[0060] Furthermore, while the case where the container 101 has a roughly rectangular, box-like shape without a lid has been described, it is not limited to this. The planar shape of the container 101 can also be a square, hexagon, octagon, etc. Additionally, in the planar shape of the container 101's exterior, the corners of the vertices of the polygons can be chamfered, and furthermore, it can be a planar shape where any one side is formed by a curve. Furthermore, the planar shape of the interior of the container 101 is not limited to the shapes described above and can also be other shapes. Moreover, the planar shapes of the exterior and interior of the container 101 can be similar or dissimilar.

[0061] The circuit board 115 is a multilayer substrate with multiple through holes, etc., and uses materials such as glass epoxy board, composite substrate, and ceramic substrate.

[0062] The circuit board 115 has a second surface 115r on the bottom wall 112 side and a first surface 115f opposite to the second surface 115r. On the first surface 115f of the circuit board 115, a vibration rectification error correction device 2, three physical quantity sensors 200, and other electronic components not shown are mounted. Additionally, a connector 116 is mounted on the second surface 115r of the circuit board 115. Furthermore, although figures and descriptions are omitted, other wiring or terminal electrodes may also be provided on the circuit board 115.

[0063] The circuit board 115 has necks 133 and 134 that taper at the center of the circuit board 115 along the X-axis direction of the long side of the container 101 when viewed from above. The necks 133 and 134 are located on both sides of the circuit board 115 in the Y-axis direction when viewed from above, tapering from the outer edge of the circuit board 115 towards the center. Furthermore, the necks 133 and 134 are disposed opposite to the protrusion 129 and the fixing protrusion 104 of the container 101.

[0064] The circuit board 115 is inserted into the interior space of the container 1 with its second surface 115r facing the first base 127 and the second base 125. Moreover, the circuit board 115 is supported by the container 101 by the first base 127 and the second base 125.

[0065] The three physical quantity sensors 200 are frequency-inverting sensors whose output signal frequency varies according to the applied physical quantity. Physical quantity sensor 200X detects physical quantities in the X-axis direction, physical quantity sensor 200Y detects physical quantities in the Y-axis direction, and physical quantity sensor 200Z detects physical quantities in the Z-axis direction. Specifically, physical quantity sensor 200X is erected with the back surface of its package facing the X-axis direction and its side facing the first surface 115f of the circuit board 115. Furthermore, physical quantity sensor 200X outputs a signal corresponding to the detected physical quantity in the X-axis direction. Physical quantity sensor 200Y is erected with the back surface of its package facing the Y-axis direction and its side facing the first surface 115f of the circuit board 115. Furthermore, physical quantity sensor 200Y outputs a signal corresponding to the detected physical quantity in the Y-axis direction. The physical quantity sensor 200Z is positioned such that the back surface of the package faces the Z-axis direction, that is, the back surface of the package is directly opposite the first surface 115f of the circuit board 115. Furthermore, the physical quantity sensor 200Z outputs a signal corresponding to the detected physical quantity in the Z-axis direction.

[0066] The vibration rectification error correction device 2 is electrically connected to physical quantity sensors 200X, 200Y, and 200Z via wiring or electronic components not shown. Furthermore, the vibration rectification error correction device 2 generates physical quantity data that reduces vibration rectification error based on the output signals of the physical quantity sensors 200X, 200Y, and 200Z.

[0067] 1-2. Structure of Physical Quantity Sensors

[0068] Next, taking the case where the physical quantity sensor 200 is an acceleration sensor as an example, an example of the structure of the physical quantity sensor 200 will be explained. Figure 2 The three physical quantity sensors 200 shown, namely physical quantity sensors 200X, 200Y, and 200Z, can also have the same structure.

[0069] Figure 3 This is a 3D view of the physical quantity sensor 200. Figure 4 This is a top view of the physical quantity sensor 200. Figure 5 yes Figure 4 A cross-sectional view at line P1-P1. Furthermore... Figures 3 to 5 Only the interior of the physical quantity sensor 200's package is shown. In the following figures, for ease of explanation, the x-axis, y-axis, and z-axis are shown as three mutually orthogonal axes. Furthermore, in the following description, for ease of explanation, the top view viewed from the thickness direction of the extensions 38a and 38b, i.e., the z-axis direction, will be simply referred to as the "top view".

[0070] like Figures 3 to 5As shown, the physical quantity sensor 200 has a base plate 5 and four counterweights 50, 52, 54, and 56.

[0071] The substrate 5 includes: a plate-shaped base 10 extending along the x-axis and having main surfaces 10a and 10b facing opposite directions; a connecting portion 12 extending from the base 10 toward the y-axis; a movable portion 13 extending rectangularly from the connecting portion 12 toward the opposite direction to the base 10; two support portions 30a and 30b extending from both ends of the base 10 along the outer edge of the movable portion 13 in the x-axis direction; and a physical quantity sensing element 40 mounted on the movable portion 13 from the base 10 and engaging with the base 10 and the movable portion 13.

[0072] In the two support portions 30a and 30b, support portion 30a extends along the y-axis, separated from movable portion 13 by a gap 32a, and is provided with a joint portion 36a that fixes support portion 30a, and an extension portion 38a that extends along the x-axis, separated from movable portion 13 by a gap 32c. In other words, support portion 30a extends along the y-axis, separated from movable portion 13 by a gap 32a, and is provided with an extension portion 38a that extends along the x-axis, separated from movable portion 13 by a gap 32c, and a joint portion 36a is provided in the extension portion 38a portion starting from support portion 30a. Similarly, support portion 30b extends along the y-axis, separated from movable portion 13 by a gap 32b, and is provided with a joint portion 36b that fixes support portion 30b, and an extension portion 38b that extends along the x-axis, separated from movable portion 13 by a gap 32c. In other words, the support portion 30b extends along the y-axis, separated from the movable portion 13 by a gap 32b, and is provided with an extension portion 38b extending along the x-axis, separated from the movable portion 13 by a gap 32c, and a connecting portion 36b is provided in the extension portion 38b from the support portion 30b.

[0073] Furthermore, the joining portions 36a and 36b provided on the support portions 30a and 30b are used to mount the substrate portion 5 of the physical quantity sensor 200 to external components such as the package. In addition, the base portion 10, the connecting portion 12, the movable portion 13, the support portions 30a and 30b, and the extension portions 38a and 38b can also be integrally formed.

[0074] The movable part 13 is surrounded by support parts 30a and 30b and base 10, and is connected to base 10 via connecting part 12, and is supported by a single arm. Furthermore, the movable part 13 has main surfaces 13a and 13b facing opposite directions, and side surfaces 13c along support part 30a and 13d along support part 30b. Main surface 13a faces the same side as main surface 10a of base 10, and main surface 13b faces the same side as main surface 10b of base 10.

[0075] A connecting portion 12 is disposed between the base 10 and the movable portion 13, connecting the base 10 and the movable portion 13. The thickness of the connecting portion 12 is thinner than the thickness of the base 10 and the movable portion 13. The connecting portion 12 has grooves 12a and 12b. These grooves 12a and 12b are formed along the X-axis, and the connecting portion 12 functions as a fulcrum, i.e., an intermediate hinge, when the movable portion 13 is displaced relative to the base 10. Such a connecting portion 12 and movable portion 13 function as a cantilever.

[0076] Furthermore, a physical quantity detection element 40 is fixed to the surface from the main surface 10a of the base 10 to the main surface 13a of the movable part 13 by a bonding agent 60. The fixed positions of the physical quantity detection element 40 are two locations at the center of the main surface 10a and the main surface 13a in the x-axis direction, respectively.

[0077] The physical quantity detection element 40 includes: a base portion 42a, fixed to the main surface 10a of the base 10 by a bonding agent 60; a base portion 42b, fixed to the main surface 13a of the movable portion 13 by a bonding agent 60; and vibration beams 41a and 41b, located between the base portions 42a and 42b and used for detecting physical quantities. In this case, the vibration beams 41a and 41b are prismatic in shape, and when an AC voltage drive signal is applied to the excitation electrodes (not shown) provided on the vibration beams 41a and 41b, they undergo bending vibrations that are either separated from or close to each other along the x-axis. That is, the physical quantity detection element 40 is a tuning fork type vibrating plate.

[0078] The base portion 42a of the physical quantity sensing element 40 is provided with lead-out electrodes 44a and 44b. These lead-out electrodes 44a and 44b are electrically connected to excitation electrodes (not shown) provided on the vibration beams 41a and 41b. The lead-out electrodes 44a and 44b are electrically connected to connection terminals 46a and 46b provided on the main surface 10a of the base 10 via metal wires 48. The connection terminals 46a and 46b are electrically connected to external connection terminals 49a and 49b via wiring (not shown). The external connection terminals 49a and 49b are provided on the side of the physical quantity sensor 200 on which the package is mounted, i.e., the main surface 10b side of the base 10, so as to overlap with the encapsulation joint 34 when viewed from above. The encapsulation joint 34 is used to mount the substrate portion 5 of the physical quantity sensor 200 to external components such as the package, and has two portions at the ends of both sides in the x-axis direction of the base 10.

[0079] The physical quantity sensing element 40 is formed by patterning a crystal substrate cut from a raw crystal at a predetermined angle using photolithography and etching techniques. In this case, considering the reduction of the difference in the coefficient of linear expansion between the base 10 and the movable part 13, the physical quantity sensing element 40 is preferably made of the same material as the base 10 and the movable part 13.

[0080] The counterweights 50, 52, 54, and 56 are rectangular in shape when viewed from above and are disposed on the movable part 13. The counterweights 50 and 52 are fixed to the main surface 13a of the movable part 13 by means of a connecting member 62, and the counterweights 54 and 56 are fixed to the main surface 13b of the movable part 13 by means of a connecting member 62. Here, the counterweight 50 fixed to the main surface 13a, when viewed from above, has one side of its rectangular edge aligned with the direction of the side surface 13c of the movable part 13, and the other side aligned with the direction of the side surface 31d of the extension 38a. By aligning the directions in this way, it is disposed on the side surface 13c of the movable part 13, and is configured such that the counterweight 50 overlaps with the extension 38a when viewed from above. Similarly, when viewed from above, the counterweight 52, which is fixed to the main surface 13a, has one side of its rectangular edge aligned with the direction of the side surface 13d of the movable part 13, and the other side aligned with the direction of the side surface 31e of the extension 38b. Therefore, it is positioned on the side surface 13d of the movable part 13, and is arranged such that the counterweight 52 overlaps with the extension 38b when viewed from above. Similarly, when viewed from above, the counterweight 54, which is fixed to the main surface 13b, has one side of its rectangular edge aligned with the direction of the side surface 13c of the movable part 13, and the other side aligned with the direction of the side surface 31d of the extension 38a. Therefore, it is positioned on the side surface 13c of the movable part 13, and is arranged such that the counterweight 54 overlaps with the extension 38a when viewed from above. Similarly, when viewed from above, the counterweight 56 ​​fixed to the main surface 13b has one side aligned with the direction of the side surface 13d of the movable part 13 and the other side aligned with the direction of the side surface 31e of the extension 38b. Thus, it is positioned on the side surface 13d of the movable part 13 and is configured such that the counterweight 56 ​​overlaps with the extension 38b when viewed from above.

[0081] In this configuration of counterweights 50, 52, 54, and 56, counterweights 50 and 52 are arranged symmetrically around the physical quantity detection element 40, while counterweights 54 and 56 are arranged to overlap with counterweights 50 and 52 respectively when viewed from above. These counterweights 50, 52, 54, and 56 are fixed to the movable part 13 by engaging members 62 respectively located at the center of gravity of counterweights 50, 52, 54, and 56. Furthermore, since counterweights 50 and 54 overlap with extension 38a and counterweights 52 and 56 overlap with extension 38b when viewed from above, when an excessive physical quantity is applied, counterweights 50, 52, 54, and 56 abut against extensions 38a and 38b, thereby suppressing the displacement of counterweights 50, 52, 54, and 56.

[0082] The joining component 62 is made of a silicone-based thermosetting adhesive or the like. Two coatings are applied to each of the main surfaces 13a and 13b of the movable part 13. After the weights 50, 52, 54, and 56 are placed on it, the coating is cured by heating, thereby fixing the weights 50, 52, 54, and 56 to the movable part 13. Furthermore, the mating surfaces of the weights 50, 52, 54, and 56 opposite to the main surfaces 13a and 13b of the movable part 13 are rough surfaces. Therefore, when the weights 50, 52, 54, and 56 are fixed to the movable part 13, the mating area in the mating surfaces increases, thereby improving the bonding strength.

[0083] like Figure 6 As shown, when an acceleration in the +Z direction, indicated by arrow α1, is applied to the physical quantity sensor 200 configured as described above, a force in the -Z direction acts on the movable part 13, causing the movable part 13 to displace in the -Z direction with the connecting part 12 as the fulcrum. Consequently, a force is applied along the Y-axis to the physical quantity detection element 40 in a direction that separates the base part 42a and the base part 42b from each other, generating tensile stress in the vibrating beams 41a and 41b. Therefore, the vibration frequency of the vibrating beams 41a and 41b increases.

[0084] On the other hand, such as Figure 7 As shown, when an acceleration in the -Z direction, indicated by arrow α2, is applied to the physical quantity sensor 200, a force in the +Z direction acts on the movable part 13, causing the movable part 13 to displace in the +Z direction with the connecting part 12 as the fulcrum. Consequently, a force is applied along the Y-axis to the physical quantity detection element 40 in a direction that brings the base part 42a and base part 42b closer together, generating compressive stress in the vibrating beams 41a and 41b. Therefore, the vibration frequency of the vibrating beams 41a and 41b decreases.

[0085] When the vibration frequency of the vibrating beams 41a and 41b changes according to the acceleration, the frequency of the signal output from the external connection terminals 49a and 49b of the physical quantity sensor 200 changes. The sensor module 1 can calculate the value of the acceleration applied to the physical quantity sensor 200 based on the change in the frequency of the output signal of the physical quantity sensor 200.

[0086] Furthermore, in order to improve the detection accuracy of acceleration as a physical quantity, the connecting portion 12 that connects the base 10, which is a fixed part, and the movable part 13 is preferably made of crystal, which is a component with a high Q value. For example, the base 10, the support portions 30a and 30b, and the movable part 13 may also be formed of crystal plate, and the grooves 12a and 12b of the connecting portion 12 are formed from both sides of the crystal plate by half-etching.

[0087] 1-3. Functional Composition of the Sensor Module

[0088] Figure 8This is a functional block diagram of the sensor module 1 according to the first embodiment. As described above, the sensor module 1 includes physical quantity sensors 200X, 200Y, and 200Z, and a vibration rectification error correction device 2.

[0089] The vibration rectification error correction device 2 includes oscillation circuits 201X, 201Y, and 201Z, frequency ratio measuring circuits 202X, 202Y, and 202Z, a microcontroller unit 210, a storage unit 220, and an interface circuit 230.

[0090] The oscillation circuit 201X amplifies the output signal of the physical quantity sensor 200X to generate a drive signal, and applies this drive signal to the physical quantity sensor 200X. With this drive signal, the vibrating beams 41a and 41b of the physical quantity sensor 200X vibrate at a frequency corresponding to the acceleration in the X-axis direction, and a signal at this frequency is output from the physical quantity sensor 200X. Additionally, the oscillation circuit 201X outputs a measured signal SIN_X, which is a rectangular wave signal amplified from the output signal of the physical quantity sensor 200X, to the frequency ratio measurement circuit 202X. The measured signal SIN_X is a signal based on the output signal of the physical quantity sensor 200X.

[0091] Similarly, the oscillation circuit 201Y amplifies the output signal of the physical quantity sensor 200Y to generate a drive signal, and applies this drive signal to the physical quantity sensor 200Y. With this drive signal, the vibration beams 41a and 41b of the physical quantity sensor 200Y vibrate at a frequency corresponding to the acceleration in the Y-axis direction, and a signal at this frequency is output from the physical quantity sensor 200Y. Furthermore, the oscillation circuit 201Y outputs the measured signal SIN_Y, which is a rectangular wave signal amplified from the output signal of the physical quantity sensor 200Y, to the frequency ratio measurement circuit 202Y. The measured signal SIN_Y is a signal based on the output signal of the physical quantity sensor 200Y.

[0092] Similarly, the oscillation circuit 201Z amplifies the output signal of the physical quantity sensor 200Z to generate a drive signal, and applies this drive signal to the physical quantity sensor 200Z. With this drive signal, the vibration beams 41a and 41b of the physical quantity sensor 200Z vibrate at a frequency corresponding to the acceleration in the Z-axis direction, and a signal at this frequency is output from the physical quantity sensor 200Z. Furthermore, the oscillation circuit 201Z outputs the measured signal SIN_Z, which is a rectangular wave signal amplified from the output signal of the physical quantity sensor 200Z, to the frequency ratio measurement circuit 202Z. The measured signal SIN_Z is a signal based on the output signal of the physical quantity sensor 200Z.

[0093] The reference signal generation circuit 203 generates and outputs a reference signal CLK with a constant frequency. In this embodiment, the frequency of the reference signal CLK is higher than the frequencies of the measured signals SIN_X, SIN_Y, and SIN_Z. Preferably, the reference signal CLK has high frequency accuracy, and the reference signal generation circuit 203 may be, for example, a temperature-compensated crystal oscillator.

[0094] The frequency ratio measuring circuit 202X counts the number of pulses of the reference signal CLK contained within a specified period of the signal SIN_X, which is the signal being measured, based on the signal output from the oscillation circuit 201X, and outputs a count value CNT_X. The count value CNT_X is the reciprocal of the frequency ratio between the measured signal SIN_X and the reference signal CLK.

[0095] The frequency ratio measuring circuit 202Y counts the number of pulses of the reference signal CLK contained in a specified period of the measured signal SIN_Y output from the oscillation circuit 201Y, and outputs a count value CNT_Y. The count value CNT_Y is the reciprocal count value corresponding to the frequency ratio of the measured signal SIN_Y and the reference signal CLK.

[0096] The frequency ratio measuring circuit 202Z counts the number of pulses of the reference signal CLK contained in a specified period of the measured signal SIN_Z output from the oscillation circuit 201Z, and outputs a count value CNT_Z. The count value CNT_Z is the reciprocal count value corresponding to the frequency ratio of the measured signal SIN_Z and the reference signal CLK.

[0097] Frequency ratio measuring circuits 202X, 202Y, and 202Z are each input with a first frequency signal CLK1 that is asynchronous with the reference signal CLK. The first frequency signal CLK1 is based on an external trigger signal EXTRG input from outside the sensor module 1. The external trigger signal EXTRG is, for example, output from a processing device 3 outside the sensor module 1. The first frequency signal CLK1 can be, for example, the external trigger signal EXTRG itself, or a buffered version of the external trigger signal EXTRG. Furthermore, the frequency ratio measuring circuits 202X, 202Y, and 202Z synchronously output count values ​​CNT_X, CNT_Y, and CNT_Z, respectively, in sync with the first frequency signal CLK1.

[0098] Storage unit 220 stores programs and data, and may include volatile memory such as SRAM or DRAM. SRAM is an abbreviation for Static Random Access Memory, and DRAM is an abbreviation for Dynamic Random Access Memory. Alternatively, storage unit 220 may also include non-volatile memory such as semiconductor memory like EEPROM or flash memory, magnetic storage devices like hard disk drives, and optical storage devices like optical disc drives. EEPROM is an abbreviation for Electrically Erasable Programmable Read Only Memory.

[0099] The microcontroller unit 210 operates synchronously with the reference signal CLK, performing prescribed computational and control processing by executing a program (not shown) stored in the storage unit 220. For example, the microcontroller unit 210 measures the physical quantities detected by the physical quantity sensors 200X, 200Y, and 200Z based on the count value CNT_X output from the frequency ratio measuring circuit 202X, the count value CNT_Y output from the frequency ratio measuring circuit 202Y, and the count value CNT_Z output from the frequency ratio measuring circuit 202Z. Specifically, the microcontroller unit 210 converts the count values ​​CNT_X, CNT_Y, and CNT_Z into measured values ​​of the physical quantity in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively. For example, the storage unit 220 may also store table information specifying the correspondence between count values ​​and measured values ​​of physical quantities, or information on the relationship between count values ​​and measured values ​​of physical quantities, and the microcontroller unit 210 refers to this information to convert each count value into a measured value of the physical quantity.

[0100] The microcontroller unit 210 can also send the measured values ​​of physical quantities in the X-axis direction, Y-axis direction, and Z-axis direction to the processing device 3 via the interface circuit 230. Alternatively, the microcontroller unit 210 can write the measured values ​​of physical quantities in the X-axis direction, Y-axis direction, and Z-axis direction to the storage unit 220 respectively, and the processing device 3 can read each measured value via the interface circuit 230.

[0101] Furthermore, since the frequency ratio measuring circuits 202X, 202Y, and 202Z have the same configuration and operation, any one of them will be referred to as frequency ratio measuring circuit 202. Additionally, any one of the measured signals SIN_X, SIN_Y, and SIN_Z input to frequency ratio measuring circuit 202 will be referred to as the measured signal SIN, and any one of the count values ​​CNT_X, CNT_Y, and CNT_Z output from frequency ratio measuring circuit 202 will be referred to as the count value CNT.

[0102] 1-4. Vibration rectification error

[0103] Vibration rectification error corresponds to the DC offset generated during rectification due to the nonlinear characteristics of the sensor module 1's response to vibration. The abnormal displacement of the sensor module 1's output offset is observed. In applications such as inclinometers that use the sensor module 1, where the DC output of the sensor module 1 is directly used as the measurement object, it becomes a major cause of serious measurement error. The main mechanisms that generate vibration rectification error can be cited as: [1] caused by asymmetric track, [2] caused by the nonlinear characteristics of the scaling factor, and [3] caused by the structural resonance of the physical quantity sensor 200.

[0104] [1] Due to the vibration rectification error caused by the asymmetric track

[0105] When the sensitivity axis of the physical quantity sensor 200 is located in the direction of gravitational acceleration, the measured value in the sensor module 1 corresponds to the gravitational acceleration of 1g = 9.8 m / s². 2 The corresponding offset. For example, if the dynamic range of the physical quantity sensor 200 is 2g, then vibrations up to 1g can be measured with unlimited amplitude. If a vibration exceeding 1g is applied under this condition, asymmetrical amplitude limiting occurs, thus including vibration rectification error in the measured value.

[0106] For example, when the dynamic range is wide, such as 15g, there is almost no issue with amplitude limiting under normal operating conditions. On the other hand, the physical quantity sensor 200 has a built-in physical protection mechanism to prevent damage to the physical quantity detection element 40. When the vibration level exceeds a certain threshold, the protection mechanism activates, thus limiting the amplitude. To prevent this, it is necessary to study the accessories used to set the sensor module 1 and implement countermeasures such as damping vibrations in the resonant frequency band.

[0107] [2] Vibration rectification error caused by the nonlinear characteristics of the scaling factor

[0108] Figure 9 This diagram illustrates, in principle, the vibration rectification error caused by output waveform distortion. Figure 9 In the diagram, the solid line represents the sine wave vibration waveform and the smoothed waveform, while the dashed line represents the asymmetrical vibration waveform above and below the vibration center and the smoothed waveform. The smoothed waveform shown by the solid line is 0, while the smoothed waveform shown by the dashed line is negative and exhibits an offset during smoothing.

[0109] The physical quantity sensor 200 is a frequency conversion sensor, and the count value CNT corresponding to the frequency ratio of the measured signal SIN and the reference signal CLK is the reciprocal count value. The relationship between the acceleration applied to the physical quantity sensor 200 and the reciprocal count value has non-linear characteristics. Figure 10 The dashed line represents the nonlinear relationship between the applied acceleration and the reciprocal count value. Additionally, Figure 11 The dashed line represents the nonlinear characteristic of the applied acceleration and the oscillation frequency of the physical quantity sensor 200. Additionally, Figure 12 The dashed line represents the nonlinear characteristics of the oscillation frequency and reciprocal count value of the physical quantity sensor 200. Figure 10 The dashed line passes through Figure 11 The dashed lines and Figure 12 It is obtained by combining the dashed lines.

[0110] Here, the relationship between the oscillation frequency and the reciprocal count value is shown as follows: Figure 12 Correcting the relationship between acceleration and the reciprocal count value, as shown by the solid line, allows the relationship between acceleration and the reciprocal count value to be as follows: Figure 10 The solid line is close to linear. Specifically, the microcontroller unit 210 described above can use the correction function represented by equation (1) to correct the count value CNT.

[0111] [Mathematical Expression 1]

[0112] Y = {cd} 2 (1)

[0113] In equation (1), c is the... Figure 10 The dashed line corresponds to the count value before correction, and Y is the value before correction. Figure 10 The solid line corresponds to the corrected count value, and d is the value that determines... Figure 12 The coefficient indicating the degree of correction. For example, the coefficient d is stored in the storage unit 220 or set by the processing device 3.

[0114] [3] Vibration rectification error caused by cantilever resonance

[0115] As an acceleration detection principle, the physical quantity sensor 200 transmits the deflection of the counterweighted cantilever caused by acceleration to the physical quantity detection element 40, which is a double tuning fork oscillator, thereby changing the tension acting on the physical quantity detection element 40 and thus changing the oscillation frequency. Therefore, the physical quantity detection element 40 has a resonant frequency caused by the cantilever structure, and when the cantilever resonance is excited, an inherent vibration rectification error is generated. The cantilever resonance is a frequency higher than the frequency band corresponding to the range of detectable acceleration. Its vibration component is removed by the low-pass filter inside the vibration rectification error correction device 2, but a vibration rectification error is generated as a bias offset reflecting the asymmetry of the vibration. As the amplitude of the cantilever resonance increases, the asymmetry of the output waveform of the physical quantity sensor 200 increases, thereby increasing the vibration rectification error. Therefore, reducing the vibration rectification error caused by the cantilever resonance becomes an important issue.

[0116] In this embodiment, the frequency ratio measuring circuit 202 uses a reciprocal counting method to count the number of pulses of the reference signal CLK contained within a specified period of the measured signal SIN. Therefore, the timing for acquiring this count value is synchronized with the measured signal SIN. On the other hand, the count value CNT output from the frequency ratio measuring circuit 202 needs to be synchronized with the first frequency signal CLK1. Since the timing for acquiring the count value of the pulse count of the reference signal CLK is not synchronized with the first frequency signal CLK1, resampling is required. In the frequency ratio measuring circuit 202, by designing the configuration required for resampling, a count value CNT that is corrected for the vibration rectification error caused by cantilever resonance can be generated.

[0117] 1-5. Composition of the frequency ratio measuring circuit

[0118] The frequency ratio measuring circuit 202 measures the frequency ratio of the measured signal SIN to the reference signal CLK by a reciprocal counting method. Figure 13 This is a diagram illustrating an example configuration of the frequency ratio measuring circuit 202 in the first embodiment. (See diagram for example.) Figure 13 As shown, the frequency ratio measurement circuit 202 includes a frequency ΔΣ modulation circuit 300, a first low-pass filter 310, a latch circuit 320, and a second low-pass filter 330.

[0119] The frequency ΔΣ modulation circuit 300 uses the measured signal SIN to perform frequency ΔΣ modulation on the reference signal CLK, generating a frequency ΔΣ modulated signal. The frequency ΔΣ modulation circuit 300 includes a counter 301, a latch circuit 302, a latch circuit 303, and a subtractor 304. The counter 301 counts the rising edge of the reference signal CLK and outputs a count value CT0. The latch circuit 302 latches and holds the count value CT0 synchronously with the rising edge of the measured signal SIN. The latch circuit 303 latches and holds the count value held by the latch circuit 302 synchronously with the rising edge of the measured signal SIN. The subtractor 304 subtracts the count value held by the latch circuit 303 from the count value held by the latch circuit 302, generating a count value CT1 and outputting it. This count value CT1 is the frequency ΔΣ modulated signal generated by the frequency ΔΣ modulation circuit 300.

[0120] The frequency ΔΣ modulation circuit 300, also known as a single-pass frequency ΔΣ modulator, latches the pulse count of the reference signal CLK twice using the measured signal SIN. The rising edge of the measured signal SIN is used as a trigger to sequentially maintain the pulse count of the reference signal CLK. Here, the frequency ΔΣ modulation circuit 300 is described as performing latching operation at the rising edge of the measured signal SIN, but latching can also be performed at the falling edge, or both the rising and falling edges. Furthermore, the subtractor 304 calculates the difference between the two counts held in latching circuits 302 and 303, and outputs the increment of the pulse count of the reference signal CLK observed during one cycle of the measured signal SIN along with the time elapsed, without dead-zone. When the frequency of the measured signal SIN is set to fx and the frequency of the reference signal CLK is set to fc, the frequency ratio is fc / fx. The frequency ΔΣ modulation circuit 300 outputs a frequency ΔΣ modulated signal representing the frequency ratio as a digital signal string.

[0121] The first low-pass filter 310 is disposed after the frequency ΔΣ modulation circuit 300 and operates synchronously with the signal SIN being measured. The output of the first low-pass filter 310 is a count value CT2 that removes or reduces the noise component contained in the count value CT1 of the frequency ΔΣ modulation signal. Figure 13 In this circuit, the first low-pass filter 310 is immediately placed after the frequency ΔΣ modulation circuit 300, but it can be placed on the signal path from the output of the frequency ΔΣ modulation circuit 300 to the input of the second low-pass filter 330.

[0122] The latch circuit 320 is located after the first low-pass filter 310 and latches the count value CT2 output from the first low-pass filter 310 synchronously with the first frequency signal CLK1, and keeps it as the count value CT3.

[0123] The second low-pass filter 330 is disposed after the first low-pass filter 310 and operates synchronously with the first frequency signal CLK1, which is not synchronized with the reference signal CLK. The output of the second low-pass filter 330 is a count value that removes or reduces the noise component contained in the count value CT3 held by the latch circuit 320. The count value output from the second low-pass filter 330 is output as the count value CNT to the microcontroller unit 210. The first frequency signal CLK1 is a signal based on the external trigger signal EXTRG, therefore the count value CNT is a count value synchronized with the external trigger signal EXTRG.

[0124] In this way, the frequency ratio measuring circuit 202 measures the frequency ratio of the measured signal SIN to the reference signal CLK. However, since the reciprocal of the frequency is the period, it can also be called measuring the period ratio of the measured signal SIN to the reference signal CLK.

[0125] Figure 14 This is a diagram illustrating an example of the configuration of the first low-pass filter 310. Figure 14 In the example, the first low-pass filter 310 includes a delay element 311, an integrator 312, an integrator 313, a decimator 314, a delay element 315, a differentiator 316, a delay element 317, and a differentiator 318. Each part of the first low-pass filter 310 operates synchronously with the signal SIN being measured.

[0126] The delay element 311 outputs a count value that delays the count value CT1, synchronously with the measured signal SIN. The delay element 311 has n1 taps. For example, the delay element 311 can be implemented using a shift register with n1 registers connected in series.

[0127] The integrator 312 outputs a count value that is accumulated from the count value output from the delay element 311, in sync with the measured signal SIN.

[0128] Integrator 313 outputs a count value that is accumulated from the count value output from integrator 312, synchronously with the measured signal SIN.

[0129] Extractor 314 outputs a count value that has been extracted from the count value output from integrator 313 at a ratio of 1 / R, in sync with the measured signal SIN.

[0130] The delay element 315 outputs a count value that is synchronous with the measured signal SIN, delaying the count value output from the extractor 314. The delay element 315 has n² taps. For example, the delay element 315 can be implemented using a shift register with n² registers connected in series.

[0131] The output of differentiator 316 is the count value of the output of extractor 314 minus the count value of delay element 315.

[0132] The delay element 317 outputs a count value that is synchronous with the measured signal SIN, delaying the count value output from the differentiator 316. The delay element 317 has n3 taps. For example, the delay element 317 can be implemented using a shift register with n3 registers connected in series.

[0133] The output of differentiator 318 is the count value CT2 obtained by subtracting the count value output by delay element 317 from the count value output by differentiator 316.

[0134] Figure 15 This is a diagram illustrating other configuration examples of the first low-pass filter 310. In Figure 15 In the example, the first low-pass filter 310 includes an integrator 401, a delay element 402, a differentiator 403, an integrator 404, an integrator 405, a decimator 406, a delay element 407, a differentiator 408, a delay element 409, and a differentiator 410. Each part of the first low-pass filter 310 operates synchronously with the signal SIN being measured.

[0135] The integrator 401 outputs the accumulated count value of the count value CT1 synchronously with the measured signal SIN.

[0136] The delay element 402 outputs a count value that is delayed from the count value output from the integrator 401, synchronously with the measured signal SIN. The delay element 402 has n1 taps. For example, the delay element 402 can be implemented using a shift register with n1 registers connected in series.

[0137] The output of differentiator 403 is the count value obtained by subtracting the count value from the output of integrator 401 from the count value obtained by delay element 402.

[0138] The integrator 404 outputs a count value that is accumulated from the count value output from the differentiator 403, in sync with the measured signal SIN.

[0139] Integrator 405 outputs a count value that is accumulated from the count value output from integrator 404, synchronously with the measured signal SIN.

[0140] Extractor 406 outputs a count value that has been extracted from the count value output from integrator 405 at a ratio of 1 / R, in sync with the measured signal SIN.

[0141] The delay element 407 outputs a count value that is delayed from the count value output from the extractor 406, synchronously with the measured signal SIN. The delay element 407 has n² taps. For example, the delay element 407 can be implemented using a shift register with n² registers connected in series.

[0142] The output of differentiator 408 is the count value of the output of extractor 406 minus the count value of delay element 407.

[0143] The delay element 409 outputs a count value that is delayed from the count value output from the differentiator 408, synchronously with the measured signal SIN. The delay element 409 has n3 taps. For example, the delay element 409 can be implemented using a shift register with n3 registers connected in series.

[0144] The output of differentiator 410 is the count value CT2 obtained by subtracting the count value output by delay element 409 from the count value output by differentiator 408.

[0145] exist Figure 14 or Figure 15 In this example, the extraction ratio R is fixed, while the number of taps n1, n2, and n3 is variable. The number of taps n1, n2, and n3 is stored in the storage unit 220 or set by the processing device 3.

[0146] like Figure 14 or Figure 15 The first low-pass filter 310 thus constructed functions as a CIC filter with a group delay that varies according to the number of taps n1, n2, and n3. CIC is an abbreviation for Cascaded Integrator Comb.

[0147] Figure 16 This is a diagram illustrating an example of the configuration of the second low-pass filter 330. Figure 16 In this example, the second low-pass filter 330 includes an integrator 331, a delay element 332, a differentiator 333, and a decimator 334. Each part of the second low-pass filter 330 operates synchronously with the first frequency signal CLK1.

[0148] The integrator 331 outputs the accumulated count value of the count value CT3 synchronously with the first frequency signal CLK1.

[0149] The delay element 332 outputs a count value that delays the count value output from the integrator 331, synchronously with the first frequency signal CLK1. The delay element 332 has n4 taps. For example, the delay element 332 can be implemented using a shift register with n4 registers connected in series. The number of taps n4 is variable. The number of taps n4 is stored in the storage unit 220 or set by the processing device 3.

[0150] The output of the differentiator 333 is the count value obtained by subtracting the count value from the output of the integrator 331 from the count value obtained by the delay element 332.

[0151] The extractor 334 outputs a count value CNT, which is extracted from the count value output by the differentiator 333 at a ratio of 1 / n4, in sync with the first frequency signal CLK1.

[0152] Since the second low-pass filter 330 configured in this way accumulates the count value CT3 while resampling it using the first frequency signal CLK1, it functions as a weighted moving average filter that weights the count value CT3 over its duration.

[0153] Thus, the first low-pass filter 310 operates synchronously with the measured signal SIN, and the second low-pass filter 330 performs resampling synchronously with the first frequency signal CLK1. Therefore, nonlinear characteristics are generated in the input and output of the frequency ratio measuring circuit 202. Consequently, the count value CNT output from the frequency ratio measuring circuit 202 includes a vibration rectification error caused by this nonlinear characteristic. Furthermore, this vibration rectification error can be adjusted by adjusting at least one of the following: the number of taps n1 of the delay element 311 or delay element 402 in the first low-pass filter 310; the number of taps n2 of the delay element 315 or delay element 407; the number of taps n3 of the delay element 317 or delay element 409 in the second low-pass filter 330; and the number of taps n4 of the delay element 332 in the second low-pass filter 330.

[0154] Figure 17 This diagram illustrates how the vibration rectification error caused by the nonlinear characteristics of the input and output of the frequency ratio measuring circuit 202 can be adjusted. Figure 17 The diagram illustrates an example where the period of the measured signal SIN is longer than the period of the reference signal CLK, and the update period of the count value CNT is longer than the period of the measured signal SIN. The horizontal axis corresponds to the passage of time. Figure 17 In the diagram, the rising edge timing is represented by a short vertical line for the reference signal CLK. Similarly, the timing of value changes for the count values ​​CT1 and CT2 is represented by short vertical lines. Furthermore, Figure 17 For the purpose of explaining the adjustment mechanism of vibration rectification error, simplified values ​​are used for ease of understanding. In addition, although it is recorded that the count value CT2 is determined only after the count value CT1 is determined, the actual calculation of the count value CT2 is performed after the count value CT1 is determined.

[0155] exist Figure 17In the examples, (A) shows the case where the period of the measured signal SIN is constant, and (B), (C), and (D) show the case where the measured signal SIN is frequency-modulated. In (B), (C), and (D), the group delay of the first low-pass filter 310 is different for each of them. For simplicity, the period of the reference signal CLK and the period of the measured signal SIN are set to a simple integer ratio, and the count value CT1 input to the first low-pass filter 310 is directly output with a certain group delay. The second low-pass filter 330, in sync with the first frequency signal CLK1, accumulates the count value CT3 latched by the count value CT2 output from the first low-pass filter 310, and outputs the accumulated value of the four counts as the count value CNT.

[0156] In example (A), the count value CT2 is always 4, and the count value CNT is 4 × 4 = 16. In example (B), the measured signal SIN is frequency modulated, and the group delay of the first low-pass filter 310 is set to 0, so the count value CT2 repeats 5, 5, 3, 3. Since the accumulation is time-weighted, the count value CNT is 5 × 3 + 3 × 1 = 18, which is larger than the count value CNT in (A). In example (C), the case of the count value CT2 repeating 5, 5, 3, 3 is the same as in example (B), but a group delay is generated in the first low-pass filter 310. The accumulation is time-weighted, and the result is a count value CNT of 5 × 2 + 3 × 2 = 16, which is the same as the count value CNT in (A). In example (D), the case of the count value CT2 repeating 5, 5, 3, 3 is the same as in examples (B) and (C), but the group delay generated in the first low-pass filter 310 is larger compared to example (C). In example (D), the count value CNT is 5×1+3×3=14, which is smaller than the count value CNT in (A).

[0157] According to usage Figure 17 The examination can be qualitatively understood as follows: the vibration rectification error caused by the nonlinear characteristics of the input and output of the frequency ratio measuring circuit 202 varies according to the group delay of the first low-pass filter 310. Similarly, the vibration rectification error caused by the nonlinear characteristics of the input and output of the frequency ratio measuring circuit 202 varies according to the group delay of the second low-pass filter 330. Therefore, by controlling the group delay of the first low-pass filter 310 and the second low-pass filter 330, the vibration rectification error caused by the nonlinear characteristics of the input and output of the frequency ratio measuring circuit 202 is made to be in opposite phase with the vibration rectification error generated by the cantilever resonance, thereby eliminating their respective vibration rectification errors. The group delay of the first low-pass filter 310 can be controlled by... Figure 14 or Figure 15 The tap numbers n1, n2, and n3 are set to control the output. Additionally, the group delay of the second low-pass filter 330 can be controlled by... Figure 16The setting of the number of taps n4 is controlled. Therefore, in this embodiment, the storage unit 220 stores the number of taps n1, n2, n3, and n4, which are information used to control the group delay of the first low-pass filter 310 and the group delay of the second low-pass filter 330.

[0158] As an example, in Figure 18 The diagram shows the dependence of the vibration rectification error in the measured values ​​of the vibration rectification error correction device 2 on the number of taps n1, with tap numbers n2, n3, and n4 fixed. Figure 18 In the graph, the horizontal axis represents the number of taps n1, and the vertical axis represents the vibration rectification error. Furthermore, VRE on the vertical axis is an abbreviation for Vibration Rectification Error. According to... Figure 18 For example, if the number of taps n1 is set appropriately, the vibration rectification error can be corrected to be close to 0.

[0159] exist Figure 14 In the first low-pass filter 310, the delay element 311 is implemented by a FIFO register using a shift register. Therefore, when this FIFO register is taken outside the first low-pass filter 310, Figure 13 The frequency ratio of the constructed measuring circuit 202 becomes Figure 19 The structure shown is as follows: Figure 14 The first low-pass filter 310 constitutes the Figure 20 The structure shown is as follows. FIFO is an abbreviation for First In First Out.

[0160] exist Figure 21 The image shows an example of a timing diagram for the count value CT1 input to FIFO register 340 and the count value CT1′ output by FIFO register 340. Figure 21 In the example, the count values ​​CT1 and CT1′ change synchronously with the two edges of the measured signal SIN. That is, in Figure 21 In the example, the frequency ΔΣ modulation circuit 300 and the FIFO register 340 operate synchronously with the two edges of the measured signal SIN. Case 1 is the case where the FIFO register 340 has two stages, and Case 2 is the case where the FIFO register 340 has four stages.

[0161] exist Figure 19 In the frequency ratio measurement circuit 202, if the number of stages of the FIFO register 340, the group delay of the first low-pass filter 310, and the group delay of the second low-pass filter 330, which are equivalent to the number of taps n1 of the delay element 311, are appropriately set, the vibration rectification error can also be corrected to be close to 0.

[0162] On the other hand, when the vibration component input to the physical quantity sensor 200 includes the frequency of the structural resonance determined by the structure of the physical quantity sensor 200, structural resonance of the physical quantity sensor 200 occurs. As a result, the output signal of the physical quantity sensor 200 includes a signal component caused by this structural resonance. The signal component caused by the structural resonance is not the signal that the physical quantity sensor 200 is designed to detect, and therefore it is desirable that it is not included in the count value CNT output from the frequency ratio measuring circuit 202. Therefore, in this embodiment, the cutoff frequencies of the first low-pass filter 310 and the second low-pass filter 330 are lower than the frequency involved in the structural resonance of the physical quantity sensor 200. For example, the cutoff frequency of the first low-pass filter 310 may also be higher than the frequency involved in the structural resonance of the physical quantity sensor 200, and the cutoff frequency of the second low-pass filter 330 may also be lower than the frequency involved in the structural resonance of the physical quantity sensor 200. Alternatively, both the cutoff frequencies of the first low-pass filter 310 and the second low-pass filter 330 may be lower than the frequency involved in the structural resonance of the physical quantity sensor 200. In this embodiment, the structural resonance of the physical quantity sensor 200 is a cantilever resonance. Furthermore, the first low-pass filter 310 is an example of a "first filter", and the second low-pass filter 330 is an example of a "second filter".

[0163] 1-6. Vibration Rectification Error Correction Method

[0164] Figure 22 It means possessing Figure 13 or Figure 19 A flowchart illustrating an example of the sequence of vibration rectification error correction methods executed by the vibration rectification error correction device 2, which is composed of a frequency ratio measuring circuit 202.

[0165] like Figure 22 As shown, firstly, in process S10, the vibration rectification error correction device 2 uses the measured signal SIN to perform frequency ΔΣ modulation on the reference signal CLK to generate a frequency ΔΣ modulated signal.

[0166] Next, in step S20, the vibration rectification error correction device 2 synchronously performs a first filtering process on the signal based on the frequency ΔΣ modulation signal, i.e., the count value CT1, generated in step S10, in conjunction with the measured signal SIN. Specifically, it has... Figure 13 The vibration rectification error correction device 2 of the frequency ratio measurement circuit 202 performs a first filtering process on the count value CT1 synchronously with the measured signal SIN. Additionally, it has... Figure 19 The vibration rectification error correction device 2 of the frequency ratio measuring circuit 202 performs a first filtering process on the count value CT1′ synchronously with the measured signal SIN. For example, the first filtering process is a low-pass filtering process.

[0167] Next, in step S30, the vibration rectification error correction device 2 performs a second filtering process on the signal CT3, which is the count value CT2 obtained through the first filtering process in step S20, in sync with the first frequency signal CLK1, which is asynchronous with the reference signal CLK. The first frequency signal CLK1 is based on the external trigger signal EXTRG input from outside the sensor module 1. For example, the second filtering process is a low-pass filtering process.

[0168] Then, in process S40, the vibration rectification error correction device 2 repeatedly performs processes S10, S20, and S30 until the measurement is completed.

[0169] 1-7. Effects

[0170] As explained above, in the sensor module 1 of the first embodiment, in the vibration rectification error correction device 2, the frequency ΔΣ modulation circuit 300 uses the measured signal SIN, which is based on the output signal of the physical quantity sensor 200, to perform frequency ΔΣ modulation on the reference signal CLK, thereby generating a frequency ΔΣ modulated signal, i.e., a count value CT1, which shows the frequency ratio of the measured signal SIN to the reference signal CLK. Furthermore, in the vibration rectification error correction device 2, the first low-pass filter 310, located after the frequency ΔΣ modulation circuit 300, operates synchronously with the measured signal SIN, and the second low-pass filter 330, located after the first low-pass filter 310, operates synchronously with a first frequency signal CLK1, which is different from the measured signal SIN. As a result, a nonlinear characteristic is generated in the relationship between the count value CT1 and the count value CNT output from the second low-pass filter 330. Furthermore, the vibration rectification error caused by this nonlinear characteristic varies according to the group delay of the first low-pass filter 310 and the delay of the second low-pass filter 330. Therefore, according to the sensor module 1 of the first embodiment, in the vibration rectification error correction device 2, by setting the group delay of the first low-pass filter 310 and the delay of the second low-pass filter 330 to appropriate values, the vibration rectification error caused by the nonlinear characteristic and the vibration rectification error caused by the asymmetry of the measured signal SIN cancel each other out, and the vibration rectification error contained in the measured data, i.e., the count value CNT, based on the output signal of the physical quantity sensor 200 is reduced. In particular, in the vibration rectification error correction device 2, the storage unit 220 stores information for controlling the group delay of the first low-pass filter 310 and the group delay of the second low-pass filter 330, so by appropriately setting this information, the vibration rectification error contained in the count value CNT is reduced.

[0171] Furthermore, in the sensor module 1 of the first embodiment, the count value CNT output from the second low-pass filter 330 in the vibration rectification error correction device 2 is synchronized with the first frequency signal CLK1. Therefore, in order to obtain data synchronized with the first frequency signal CLK1, a large-scale synchronization circuit or a heavy-load post-processing operation is not required after the second low-pass filter 330. Thus, according to the sensor module 1 of the first embodiment, in the vibration rectification error correction device 2, in order to generate the count value CNT synchronized with the first frequency signal CLK1 which is not synchronized with the reference signal CLK, a large-scale synchronization circuit or a heavy-load operation is not required.

[0172] Furthermore, in the sensor module 1 of the first embodiment, in the vibration rectification error correction device 2, the first frequency signal CLK1 is a signal based on the external trigger signal EXTRG. Therefore, the count value CNT output from the second low-pass filter 330 is synchronized with the external trigger signal EXTRG. Thus, according to the sensor module 1 of the first embodiment, in the vibration rectification error correction device 2, in order to generate the count value CNT synchronized with the external trigger signal EXTRG, a large-scale synchronization circuit or a heavy-load operation is not required.

[0173] Furthermore, in the sensor module 1 of the first embodiment, the vibration rectification error correction device 2 can generate a count value CNT that reduces the significant noise component caused by the structural resonance of the physical quantity sensor 200 by making the cutoff frequency based on the first low-pass filter 310 and the second low-pass filter 330 lower than the frequency involved in the structural resonance of the physical quantity sensor 200.

[0174] 2. Second Implementation Method

[0175] Hereinafter, regarding the sensor module of the second embodiment, the same reference numerals are used for the same constituent elements as in the first embodiment, and descriptions that are repeated in the first embodiment are omitted or simplified. The description mainly focuses on the contents that are different from those in the first embodiment.

[0176] In the first embodiment, the adjustment resolution of the group delay of the first low-pass filter 310 is determined by the period of the measured signal SIN, and the adjustment resolution of the group delay of the second low-pass filter 330 is determined by the period of the first frequency signal CLK1 based on the external trigger signal EXTRG. Therefore, the correction resolution of the vibration rectification error is determined by the shorter of the periods of the measured signal SIN and the external trigger signal EXTRG. Thus, when the period of the external trigger signal EXTRG is longer than the period of the measured signal SIN, the correction resolution of the vibration rectification error is limited because it is determined by the period of the measured signal SIN. Therefore, in the second embodiment, to improve the correction resolution of the vibration rectification error, the period of the first frequency signal CLK1 that activates the second low-pass filter 330 is shortened, thereby improving the correction resolution of the vibration rectification error.

[0177] Figure 23 This is a functional block diagram of sensor module 1 in the second embodiment. Figure 23 In China, targeting and Figure 8 The same components are labeled with the same reference numerals. Similar to the first embodiment, the sensor module 1 of the second embodiment includes physical quantity sensors 200X, 200Y, and 200Z, and a vibration rectification error correction device 2. The functions and configurations of the physical quantity sensors 200X, 200Y, and 200Z are the same as in the first embodiment, therefore their description is omitted.

[0178] The vibration rectification error correction device 2 includes oscillation circuits 201X, 201Y, and 201Z, frequency ratio measuring circuits 202X, 202Y, and 202Z, a microcontroller unit 210, a storage unit 220, an interface circuit 230, and a multiplier circuit 240. The functions and configurations of the oscillation circuits 201X, 201Y, and 201Z, the microcontroller unit 210, the storage unit 220, and the interface circuit 230 are the same as in the first embodiment, and therefore their description is omitted.

[0179] The multiplier circuit 240 multiplies a second frequency signal CLK2 that is out of sync with the reference signal CLK. The second frequency signal CLK2 is based on an external trigger signal EXTRG input from outside the sensor module 1. The second frequency signal CLK2 can be, for example, the external trigger signal EXTRG itself, or a buffered version of the external trigger signal EXTRG. The multiplication rate of the multiplier circuit 240 can be an integer greater than or equal to 2. The multiplication rate of the multiplier circuit 240 can also be fixed. Alternatively, the multiplication rate of the multiplier circuit 240 can be variable, stored in the storage unit 220, or set by the processing device 3.

[0180] Frequency ratio measuring circuits 202X, 202Y, and 202Z are each input with a first frequency signal CLK1 that is asynchronous with the reference signal CLK. The first frequency signal CLK1 is based on the output signal of the multiplier circuit 240. The first frequency signal CLK1 can be, for example, the output signal of the multiplier circuit 240 itself, or a buffered output signal of the multiplier circuit 240. Furthermore, the frequency ratio measuring circuits 202X, 202Y, and 202Z are synchronized with the first frequency signal CLK1, outputting count values ​​CNT_X, CNT_Y, and CNT_Z respectively.

[0181] Figure 24 This is a diagram illustrating an example of the configuration of the frequency ratio measuring circuit 202 in the second embodiment. Figure 24 In China, targeting and Figure 13 The same constituent elements are labeled with the same reference numerals. Figure 24 The frequency ratio measurement circuit 202 shown includes a frequency ΔΣ modulation circuit 300, a first low-pass filter 310, a latch circuit 320, a second low-pass filter 330, and a latch circuit 350. The functions of the frequency ΔΣ modulation circuit 300, the first low-pass filter 310, the latch circuit 320, and the second low-pass filter 330 are the same as in the first embodiment, therefore their description is omitted. Furthermore, the configuration and function of the first low-pass filter 310 are the same as in the first embodiment. Figure 14 or Figure 15 The configuration and function of the second low-pass filter 330 are the same if the count value output from the decimator 334 is changed from CNT to CT4. Figure 16 The same applies, therefore its illustration and description are omitted. However, the first frequency signal CLK1 input to the latch circuit 320 and the second low-pass filter 330 is based on the output signal of the multiplier circuit 240, which differs from the first embodiment where the first frequency signal CLK1 is based on the external trigger signal EXTRG.

[0182] The latch circuit 350 is located after the second low-pass filter 330 and operates synchronously with the second frequency signal CLK2. Specifically, the latch circuit 350 latches the count value CT4 output from the second low-pass filter 330 synchronously with the second frequency signal CLK2, and holds it as the count value CNT. The count value CNT held by the latch circuit 350 is output to the microcontroller unit 210. The second frequency signal CLK2 is a signal based on the external trigger signal EXTRG, therefore the count value CNT is a count value synchronized with the external trigger signal EXTRG.

[0183] exist Figure 14In the first low-pass filter 310, the delay element 311 can be implemented using a FIFO register with a shift register. Therefore, when this FIFO register is taken outside the first low-pass filter 310, Figure 24 The frequency ratio of the constructed measuring circuit 202 becomes Figure 25 The structure shown is as follows: Figure 14 The first low-pass filter 310 constitutes the Figure 20 The structure shown.

[0184] In the second embodiment, the adjustment resolution of the group delay of the first low-pass filter 310 is determined by the period of the measured signal SIN, and the adjustment resolution of the group delay of the second low-pass filter 330 is determined by the period of the first frequency signal CLK1 based on the output signal of the multiplier circuit 240. Therefore, by making the period of the first frequency signal CLK1 shorter than the period of the measured signal SIN, the correction resolution of the vibration rectification error is determined by the period of the first frequency signal CLK1, thus achieving a higher correction resolution than in the first embodiment. Therefore, in the second embodiment, the low multiplier of the multiplier circuit 240 is set such that the frequency of the first frequency signal CLK1 is higher than the frequency of the measured signal SIN. Furthermore, since the frequency of the reference signal CLK is higher than the frequency of the measured signal SIN, it is preferable that the frequency of the first frequency signal CLK1 is higher than the frequency of the reference signal CLK in order to further improve the correction resolution of the vibration rectification error.

[0185] Figure 26 It means that by possessing Figure 24 or Figure 25 A flowchart illustrating an example of the sequence of vibration rectification error correction methods executed by the vibration rectification error correction device 2, which is composed of a frequency ratio measuring circuit 202.

[0186] like Figure 26 As shown, firstly, in process S110, the vibration rectification error correction device 2 uses the measured signal SIN to perform frequency ΔΣ modulation on the reference signal CLK to generate a frequency ΔΣ modulated signal.

[0187] Next, in step S120, the vibration rectification error correction device 2, synchronously with the measured signal SIN, performs a first filtering process on the signal based on the frequency ΔΣ modulation signal, i.e., the count value CT1, generated in step S110. Specifically, it has... Figure 24 The vibration rectification error correction device 2 of the frequency ratio measurement circuit 202 performs a first filtering process on the count value CT1 synchronously with the measured signal SIN. Additionally, it has... Figure 25 The vibration rectification error correction device 2 of the frequency ratio measuring circuit 202 performs a first filtering process on the count value CT1′ synchronously with the measured signal SIN. For example, the first filtering process is a low-pass filtering process.

[0188] Additionally, in process S130, the vibration rectification error correction device 2 performs multiplication processing on the second frequency signal CLK2, which is out of sync with the reference signal CLK. The second frequency signal CLK2 is based on the external trigger signal EXTRG, which is input from outside the sensor module 1.

[0189] Next, in step S140, the vibration rectification error correction device 2 performs a second filtering process on the signal (count value CT3) based on the signal (count value CT2) obtained through the first filtering process in step S120, synchronously with the first frequency signal CLK1, which is asynchronous with the reference signal CLK. The first frequency signal CLK1 is based on the signal obtained through the multiplication process in step S130. The frequency of the first frequency signal CLK1 is preferably higher than the frequency of the reference signal CLK. For example, the second filtering process is a low-pass filtering process.

[0190] Next, in step S150, the vibration rectification error correction device 2 synchronously latches the signal based on the count value CT4 obtained through the second filtering process in step S140, in sync with the second frequency signal CLK2.

[0191] Then, in process S160, the vibration rectification error correction device 2 repeatedly performs processes S110, S120, S130, S140, and S150 until the measurement is completed.

[0192] As explained above, in the sensor module 1 of the second embodiment, in the vibration rectification error correction device 2, the frequency ΔΣ modulation circuit 300 uses the measured signal SIN, which is based on the output signal of the physical quantity sensor 200, to perform frequency ΔΣ modulation on the reference signal CLK, thereby generating a frequency ΔΣ modulated signal, i.e., a count value CT1, which shows the frequency ratio of the measured signal SIN to the reference signal CLK. Furthermore, in the vibration rectification error correction device 2, the first low-pass filter 310, located after the frequency ΔΣ modulation circuit 300, operates synchronously with the measured signal SIN, and the second low-pass filter 330, located after the first low-pass filter 310, operates synchronously with a first frequency signal CLK1, which is different from the measured signal SIN. This generates a nonlinear characteristic in the relationship between the count value CT1, the count value CT4 output from the second low-pass filter 330, and the count value CNT output from the latch circuit 350. Furthermore, the vibration rectification error generated by this nonlinear characteristic varies according to the group delay of the first low-pass filter 310 and the delay of the second low-pass filter 330. Therefore, according to the sensor module 1 of the second embodiment, in the vibration rectification error correction device 2, by setting the group delay of the first low-pass filter 310 and the delay of the second low-pass filter 330 to appropriate values, the vibration rectification error caused by the nonlinear characteristic cancels out the vibration rectification error caused by the asymmetry of the measured signal SIN, thereby reducing the vibration rectification error contained in the measured data, i.e., the count value CNT, based on the output signal of the physical quantity sensor 200. In particular, in the vibration rectification error correction device 2, the storage unit 220 stores information for controlling the group delay of the first low-pass filter 310 and the group delay of the second low-pass filter 330, so by appropriately setting this information, the vibration rectification error contained in the count value CNT can be reduced.

[0193] In particular, in the sensor module 1 of the second embodiment, in the vibration rectification error correction device 2, by making the frequency of the first frequency signal CLK1 based on the output signal of the multiplier circuit 240 higher than the frequency of the reference signal CLK, the adjustment resolution of the group delay of the second low-pass filter is increased, thereby improving the correction resolution of the vibration rectification error. Therefore, according to the sensor module 1 of the second embodiment, in the vibration rectification error correction device 2, by setting the group delay of the first low-pass filter 310 and the delay of the second low-pass filter 330 to appropriate values, the vibration rectification error contained in the count value CNT can be further reduced.

[0194] Furthermore, in the sensor module 1 of the second embodiment, the count value CNT output from the latch circuit 350 in the vibration rectification error correction device 2 is synchronized with the second frequency signal CLK2. Therefore, in order to obtain data synchronized with the second frequency signal CLK2, a large-scale synchronization circuit or a heavy-load post-processing operation is not required after the second low-pass filter 330. Thus, according to the sensor module 1 of the second embodiment, in the vibration rectification error correction device 2, in order to generate the count value CNT synchronized with the second frequency signal CLK2 which is not synchronized with the reference signal CLK, a large-scale synchronization circuit or a heavy-load operation is not required.

[0195] Furthermore, in the sensor module 1 of the second embodiment, in the vibration rectification error correction device 2, the second frequency signal CLK2 is a signal based on the external trigger signal EXTRG, therefore the count value CNT output from the latch circuit 350 is synchronized with the external trigger signal EXTRG. Thus, according to the sensor module 1 of the second embodiment, in the vibration rectification error correction device 2, in order to generate the count value CNT synchronized with the external trigger signal EXTRG, a large-scale synchronization circuit or a heavy-load operation is not required.

[0196] Furthermore, in the sensor module 1 of the second embodiment, the vibration rectification error correction device 2 can generate a count value CNT that reduces the significant noise component caused by the structural resonance of the physical quantity sensor 200 by making the cutoff frequency based on the first low-pass filter 310 and the second low-pass filter 330 lower than the frequency involved in the structural resonance of the physical quantity sensor 200.

[0197] 3. Variations

[0198] This invention is not limited to this embodiment, and various modifications can be implemented within the scope of the spirit of this invention.

[0199] For example, in the above embodiments, the first frequency signal CLK1 is a signal based on the external trigger signal EXTRG, but it may not be a signal based on the external trigger signal EXTRG. For example, as Figure 27 As shown, the vibration rectification error correction device 2 may also include a frequency signal generation circuit 250 for generating the first frequency signal CLK1. Additionally, for example, as... Figure 28 As shown, the vibration rectification error correction device 2 may also include a frequency signal generating circuit 250 that generates a second frequency signal CLK2, and the multiplier circuit 240 may also output a first frequency signal CLK1 that multiplies the second frequency signal CLK2 generated by the frequency signal generating circuit 250.

[0200] Additionally, for example, in the second embodiment described above, when the update period of the count value CT4 output from the second low-pass filter 330 coincides with the period of the second frequency signal CLK2, the latch circuit 350 may be omitted. Similarly, in Figure 26 In the flowchart, if the update period of the signal obtained by the second filtering process of step S140 is consistent with the period of the second frequency signal CLK2, step S150 may be omitted.

[0201] In addition, for example, in the above embodiments, the sensor module 1 has three physical quantity sensors 200 and a frequency ratio measuring circuit 202, but the number of physical quantity sensors 200 and the number of frequency ratio measuring circuits 202 in the sensor module 1 can be one, two or more, respectively.

[0202] Furthermore, in the above embodiments, sensor module 1, which includes an acceleration sensor, is cited as an example of physical quantity sensor 200. However, sensor module 1, as physical quantity sensor 200, may also include sensors such as angular velocity sensors, pressure sensors, and optical sensors. In addition, sensor module 1 may also include two or more physical quantity sensors among various physical quantity sensors such as acceleration sensors, angular velocity sensors, pressure sensors, and optical sensors.

[0203] Furthermore, in the above embodiments, the physical quantity detection element 40 of the physical quantity sensor 200 is exemplified by an element made of crystal. However, the physical quantity detection element 40 may also be made of piezoelectric elements other than crystal, or it may be a capacitive MEMS element. MEMS is an abbreviation for Micro Electro Mechanical Systems.

[0204] Furthermore, in the above embodiments, a first low-pass filter 310 is cited as an example of a first filter, and a second low-pass filter 330 is cited as an example of a second filter. However, the first filter and the second filter can also be high-pass filters, band-pass filters, or smoothing filters. Similarly, the first filtering process and the second filtering process can be high-pass filtering process, band-pass filtering process, or smoothing filtering process, in addition to low-pass filtering process.

[0205] The above embodiments and modifications are examples and are not limited thereto. For example, the various embodiments and modifications can also be appropriately combined.

[0206] This invention includes configurations that are substantially identical to those described in the embodiments, such as configurations with the same function, method, and result, or configurations with the same purpose and effect. Additionally, this invention includes configurations obtained by replacing non-essential parts of the configurations described in the embodiments. Furthermore, this invention includes configurations that achieve the same function and effect as those described in the embodiments, or configurations that can achieve the same purpose. Additionally, this invention includes configurations formed by adding known techniques to the configurations described in the embodiments.

[0207] The following can be derived from the above implementation methods and variations.

[0208] One method of vibration rectification error correction device includes:

[0209] The reference signal generation circuit outputs a reference signal;

[0210] A frequency ΔΣ modulation circuit uses the measured signal to modulate the reference signal at a frequency ΔΣ to generate a frequency ΔΣ modulated signal.

[0211] A first filter, disposed after the frequency ΔΣ modulation circuit, operates synchronously with the signal being measured; and

[0212] The second filter, located after the first filter, operates synchronously with a first frequency signal that is not synchronized with the reference signal.

[0213] In this vibration rectification error correction device, a reference signal is frequency-modulated using a frequency ΔΣ modulation circuit with the measured signal, thereby generating a frequency ΔΣ modulated signal showing the frequency ratio between the measured signal and the reference signal. Furthermore, in this device, a first filter located after the frequency ΔΣ modulation circuit operates synchronously with the measured signal, while a second filter located after the first filter operates synchronously with a first frequency signal different from the measured signal. This generates a nonlinear characteristic in the relationship between the frequency ΔΣ modulated signal and the output signal of the second filter. The vibration rectification error caused by this nonlinear characteristic varies depending on the group delay of the first filter and the delay of the second filter. Therefore, according to this vibration rectification error correction device, by setting the group delay of the first filter and the delay of the second filter to appropriate values, the vibration rectification error caused by this nonlinear characteristic cancels out the vibration rectification error caused by the asymmetry of the measured signal, thereby reducing the vibration rectification error contained in the output data of the second filter.

[0214] Furthermore, in this vibration rectification error correction device, the output data of the second filter is synchronized with the first frequency signal. Therefore, in order to obtain data synchronized with the first frequency signal, a large-scale synchronization circuit or a heavy-load post-processing operation is not required after the second filter. Thus, according to this vibration rectification error correction device, in order to generate data synchronized with the first frequency signal which is not synchronized with the reference signal, a large-scale synchronization circuit or a heavy-load operation is not required.

[0215] In one embodiment of the vibration rectification error correction device, it is also possible that...

[0216] The first frequency signal is a signal based on an external trigger signal.

[0217] According to the vibration rectification error correction device, the output data of the second filter is synchronized with the external trigger signal. Therefore, in order to generate data synchronized with the external trigger signal, a large-scale synchronization circuit or a heavy-load operation is not required.

[0218] Another method for the vibration rectification error correction device is...

[0219] It includes a multiplier circuit that amplifies a second frequency signal that is out of sync with the reference signal.

[0220] The first frequency signal is a signal based on the output signal of the multiplier circuit.

[0221] The frequency of the first frequency signal is higher than the frequency of the reference signal.

[0222] In this vibration rectification error correction device, the frequency of the first frequency signal based on the output signal of the multiplier circuit is higher than the frequency of the reference signal. Therefore, the adjustment resolution of the group delay of the second filter is increased, thereby improving the correction resolution of the vibration rectification error. Thus, according to this vibration rectification error correction device, by setting the group delay of the first filter and the delay of the second filter to appropriate values, the vibration rectification error contained in the output data of the second filter can be further reduced.

[0223] Another method for the vibration rectification error correction device is...

[0224] It includes a latching circuit, which is located after the second filter and operates synchronously with the second frequency signal.

[0225] According to this vibration rectification error correction device, it is possible to generate data synchronized with a second frequency signal that is not synchronized with the reference signal without the need for a large-scale synchronization circuit or a heavy-load operation.

[0226] In one embodiment of the vibration rectification error correction device, it is also possible that...

[0227] The second frequency signal is a signal based on an external trigger signal.

[0228] According to this vibration rectification error correction device, the output data of the latch circuit is synchronized with the external trigger signal. Therefore, in order to generate data synchronized with the external trigger signal, a large-scale synchronization circuit or a heavy-load operation is not required.

[0229] Another method for the vibration rectification error correction device is...

[0230] It includes a storage unit that stores information for controlling the group delay of the first filter and the group delay of the second filter.

[0231] According to this vibration rectification error correction device, by appropriately setting information for controlling the group delay of the first filter and the group delay of the second filter stored in the storage unit, the vibration rectification error contained in the output data can be reduced.

[0232] In one embodiment of the vibration rectification error correction device, it is also possible that...

[0233] The measured signal is the output signal based on the physical quantity sensor.

[0234] According to this vibration rectification error correction device, the vibration rectification error of the measurement data based on the output signal of the physical quantity sensor can be reduced.

[0235] In one embodiment of the vibration rectification error correction device, it is also possible that...

[0236] The cutoff frequencies of the first and second filters are lower than the frequencies involved in the structural resonance of the physical quantity sensor.

[0237] According to this vibration rectification error correction device, the significant noise component generated by the structural resonance of the physical quantity sensor can be reduced by the first filter and the second filter.

[0238] One approach to sensor modules is to include:

[0239] One method of the vibration rectification error correction device; and

[0240] The physical quantity sensor.

[0241] According to this sensor module, by having a vibration rectification error correction device, it is possible to generate measurement data in which the vibration rectification error is reduced.

[0242] One method for correcting vibration rectification errors includes:

[0243] The process of using the measured signal to modulate the reference signal at a frequency ΔΣ and generating a frequency ΔΣ modulated signal.

[0244] The step of performing a first filtering process on the signal based on the frequency ΔΣ modulation signal synchronously with the measured signal; and

[0245] The process of performing a second filtering process on a signal based on the signal obtained through the first filtering process, in sync with a first frequency signal that is not synchronized with the reference signal.

[0246] In this vibration rectification error correction method, a reference signal is frequency-modulated using the measured signal (ΔΣ) to generate a frequency-modulated signal (ΔΣ) showing the frequency ratio between the measured signal and the reference signal. Furthermore, this method performs a first filtering process synchronously with the measured signal and a second filtering process synchronously with a first frequency signal different from the measured signal, thereby generating nonlinear characteristics in the relationship between the frequency-modulated signal (ΔΣ) and the signal obtained through the second filtering process. The vibration rectification error generated by this nonlinear characteristic varies according to the group delay of the first filtering process and the delay of the second filtering process. Therefore, according to this vibration rectification error correction method, by setting the group delay of the first filtering process and the delay of the second filtering process to appropriate values, the vibration rectification error generated by the nonlinear characteristic cancels out the vibration rectification error generated by the asymmetry of the measured signal, thereby reducing the vibration rectification error contained in the signal obtained through the second filtering process.

[0247] Furthermore, in this vibration rectification error correction method, the signal obtained through the second filtering process is synchronized with the first frequency signal. Therefore, in order to obtain data synchronized with the first frequency signal, no computationally intensive post-processing is required after the second low-pass filtering process. Consequently, according to this vibration rectification error correction method, no computationally intensive processing is required to generate data synchronized with the first frequency signal, which is not synchronized with the reference signal.

[0248] Another approach to the vibration rectification error correction method is...

[0249] It includes a step of multiplying a second frequency signal that is out of sync with the reference signal.

[0250] The first frequency signal is a signal based on the signal obtained through the multiplication process.

[0251] The frequency of the first frequency signal is higher than the frequency of the reference signal.

[0252] In this vibration rectification error correction method, since the frequency of the first frequency signal obtained through the multiplication process is higher than the frequency of the reference signal, the adjustment resolution of the group delay amount of the second filtering process is increased, thereby improving the correction resolution of the vibration rectification error. Therefore, according to this vibration rectification error correction method, by setting the group delay amount of the first filtering process and the delay amount of the second filtering process to appropriate values, the vibration rectification error contained in the signal obtained through the second filtering process is further reduced.

Claims

1. A vibration rectification error correction device, characterized in that, have: The reference signal generation circuit outputs a reference signal; A frequency ΔΣ modulation circuit uses the measured signal to modulate the reference signal at a frequency ΔΣ to generate a frequency ΔΣ modulated signal. The first filter is located after the frequency ΔΣ modulation circuit. It is input with the frequency ΔΣ modulation signal and the signal to be measured. It performs a first filtering process on the frequency ΔΣ modulation signal synchronously with the signal to be measured, and outputs a first signal obtained by the first filtering process. as well as The second filter, located after the first filter, is input to the first signal and the first frequency signal, and performs a second filtering process on the first signal in sync with the first frequency signal, which is not synchronized with the reference signal.

2. The vibration rectification error correction device according to claim 1, wherein, The first frequency signal is a signal based on an external trigger signal.

3. The vibration rectification error correction device according to claim 1, wherein, The vibration rectification error correction device includes a multiplier circuit that amplifies a second frequency signal that is out of sync with the reference signal. The first frequency signal is a signal based on the output signal of the multiplier circuit. The frequency of the first frequency signal is higher than the frequency of the reference signal.

4. The vibration rectification error correction device according to claim 3, wherein, The vibration rectification error correction device includes a latching circuit, which is located after the second filter and operates synchronously with the second frequency signal.

5. The vibration rectification error correction device according to claim 3 or 4, wherein, The second frequency signal is a signal based on an external trigger signal.

6. The vibration rectification error correction device according to any one of claims 1 to 4, wherein, The vibration rectification error correction device includes a storage unit that stores information for controlling the group delay of the first filter and the group delay of the second filter.

7. The vibration rectification error correction device according to any one of claims 1 to 4, wherein, The measured signal is the output signal based on the physical quantity sensor.

8. The vibration rectification error correction device according to claim 7, wherein, The cutoff frequencies of the first and second filters are lower than the frequencies involved in the structural resonance of the physical quantity sensor.

9. A sensor module, characterized in that, have: The vibration rectification error correction device as described in claim 7 or 8; and The physical quantity sensor.

10. A method for correcting vibration rectification error, characterized in that, include: The process of using the measured signal to modulate the reference signal at a frequency ΔΣ to generate a frequency ΔΣ modulated signal. The steps of performing a first filtering process on a signal based on the frequency ΔΣ modulation signal synchronously with the measured signal and outputting a first signal obtained through the first filtering process; and The process of performing a second filtering process on the first signal in sync with a first frequency signal that is not synchronized with the reference signal.

11. The vibration rectification error correction method according to claim 10, wherein, The vibration rectification error correction method includes a step of multiplying a second frequency signal that is out of sync with the reference signal. The first frequency signal is a signal based on the signal obtained through the multiplication process. The frequency of the first frequency signal is higher than the frequency of the reference signal.

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