Physical quantity sensor components, inclinometers, and structure monitoring devices

Abstract

A physical quantity sensor assembly, an inclinometer, and a structure monitoring device are provided, offering a technique for correcting nonlinearity in the output signal of the physical quantity sensor without increasing the size of the physical quantity sensor assembly. The physical quantity sensor assembly (1) comprises: a frequency-varying physical quantity sensor (3) whose frequency varies according to the change of the physical quantity; a reference signal oscillation unit (5) that outputs a reference signal; a frequency Δ-Σ modulation unit (10) that generates a frequency Δ-Σ modulated signal by frequency Δ-Σ modulation of the reference signal using an action signal based on the measured signal output by the frequency-varying physical quantity sensor (3); a first low-pass filter (20) disposed on the output side of the frequency Δ-Σ modulation unit (10) and operating synchronously with the measured signal output by the frequency-varying physical quantity sensor (3); and a second low-pass filter (60) disposed on the output side of the first low-pass filter (20) and operating synchronously with the reference signal.

Description

[0001] This application is a divisional application of patent application filed on April 19, 2019, with application number 201910316383.6 and entitled "Physical Quantity Sensor Assembly, Inclinometer and Structure Monitoring Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to physical quantity sensor components, etc. Background Technology

[0003] In physical quantity sensors that constitute a physical quantity sensor assembly for detecting physical quantities such as acceleration, there is a nonlinearity problem where the output value is not linear with respect to the physical quantity. To correct this nonlinearity, for example, a known structure is provided in a type of physical quantity sensor, namely a capacitive physical quantity sensor used for detecting acceleration, which includes a nonlinearity correction circuit for switching the amplification of the output (for example, see Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Publication No. 9-33563

[0005] However, when a dedicated circuit or mechanism such as a nonlinear correction circuit is set up, there are technical problems such as the increased circuit size and cost of the physical quantity sensor components. Summary of the Invention

[0006] The present invention is proposed to solve at least a part of the above-mentioned problems and can be implemented in the following ways or in the following applications.

[0007] A first approach to address the aforementioned problem is a physical quantity sensor assembly, comprising: a frequency-varying physical quantity sensor whose frequency changes according to a change in a physical quantity; a reference signal oscillation unit that outputs a reference signal; a frequency Δ-Σ modulation unit that uses an action signal based on an action signal from the measured signal output from the frequency-varying physical quantity sensor to perform frequency Δ-Σ modulation on the reference signal to generate a frequency Δ-Σ modulated signal; a first filter disposed on the output side of the frequency Δ-Σ modulation unit and operating synchronously with the measured signal; a second filter disposed on the output side of the first filter and operating synchronously with the reference signal; and a latch disposed between the first filter and the second filter and operating synchronously with the reference signal, wherein the output signal characteristics of the frequency-varying physical quantity sensor for the physical quantity are nonlinear.

[0008] According to the first method, by combining a first filter that operates synchronously with the measured signal and a second filter that operates synchronously with a reference signal at the output of the frequency Δ-Σ modulation section, the nonlinearity of the measured signal, which is the output of a frequency-varying physical quantity sensor, can be corrected. Therefore, it eliminates the need for a dedicated circuit or mechanism with a nonlinearity correction circuit, enabling low-cost correction of the nonlinearity of the measured signal output from the physical quantity sensor without increasing the size of the physical quantity sensor assembly.

[0009] The second type of physical quantity sensor assembly, in the first type, achieves a cutoff frequency as a filter characteristic that is lower than the structural resonant frequency of the frequency-varying physical quantity sensor by means of the combination of the first filter and the second filter.

[0010] According to the second approach, by using the first filter and the second filter, the noise component caused by the structural resonant frequency, which significantly exhibits vibration rectification error, can be reduced.

[0011] In the third approach to the physical quantity sensor assembly, the structural resonant frequency in the second approach is a frequency determined based on the structure of the frequency-varying physical quantity sensor.

[0012] According to the third method, the structural resonant frequency can be determined by the structure of the frequency-varying physical quantity sensor.

[0013] The fourth type of physical quantity sensor assembly, wherein the input-output characteristics of the first filter are set to make the nonlinearity of the measured signal approach linearity.

[0014] According to the fourth method, the measured signal, which is the output of a frequency-varying physical quantity sensor, is passed through a first filter so that the nonlinearity of the measured signal is corrected to be close to linear, and then used as the output of the physical quantity sensor assembly.

[0015] In the fifth embodiment of the physical quantity sensor assembly, in the fourth embodiment, the first filter is a smoothing filter that can change the smoothing timing by adjusting the number of filter taps, the number of filter taps being set to reduce the vibration rectification error of the measured signal due to the nonlinearity.

[0016] According to the fifth method, by changing the smoothing timing of the first filter, which serves as a smoothing filter, based on the number of filter taps, the vibration rectification error of the measured signal, which is the output of a frequency-varying physical quantity sensor, is reduced, thereby correcting the nonlinearity of the measured signal.

[0017] The sixth type of physical quantity sensor assembly, in the fifth type, allows the number of filter taps to be set and changed externally.

[0018] According to the sixth method, since the number of filter taps of the first filter can be changed from an external setting, the number of filter taps of the first filter can be appropriately set or reset according to the characteristics of the frequency-varying physical quantity sensor for each physical quantity sensor assembly.

[0019] In the seventh embodiment of the physical quantity sensor assembly, in the fifth or sixth embodiment, the first filter can change the smoothing timing by varying the density of multiple filter taps.

[0020] According to the seventh method, by adjusting the degree of correction of the nonlinearity of the measured signal output as a frequency-varying physical quantity sensor based on the number of multiple filter taps with different density of smoothing timing changes, it becomes easy to adjust the nonlinearity of the measured signal.

[0021] The physical quantity sensor assembly of the eighth method, in any one of the first to fifth methods, wherein the physical quantity is acceleration.

[0022] According to the eighth method, the physical quantity sensor assembly for detecting acceleration can have the effects of the first to fifth methods mentioned above.

[0023] The ninth type of inclinometer includes: a physical quantity sensor assembly of the eighth type; and a calculation unit that calculates the tilt angle based on the output of the physical quantity sensor assembly.

[0024] According to the ninth method, a tiltmeter can achieve a higher accuracy in calculating the tilt angle than before.

[0025] The tenth type of inertial measurement device is an inertial measurement device installed on a moving body, comprising: a physical quantity sensor assembly of the eighth type; an angular velocity physical quantity sensor assembly; and a circuit section, which calculates the attitude of the moving body based on the output of the physical quantity sensor assembly and the output of the angular velocity physical quantity sensor assembly.

[0026] According to the tenth method, an inertial measurement device can achieve a higher accuracy in calculating the posture of a moving body than before.

[0027] The eleventh type of structure monitoring device includes: a physical quantity sensor assembly of the eighth type installed on the structure; a transmitting unit installed on the structure and transmitting the output of the physical quantity sensor assembly; a receiving unit receiving the transmitted signal from the transmitting unit; and a calculation unit calculating the tilt angle of the structure based on the received signal from the receiving unit.

[0028] According to the eleventh method, a structure monitoring device is able to achieve a higher accuracy in calculating the tilt angle of a structure than before.

[0029] The twelfth type of mobile body includes: a physical quantity sensor assembly of the eighth type; and a control unit that controls at least one of acceleration, braking, and steering based on the output signal of the physical quantity sensor assembly, and switches between implementing or not implementing automatic operation based on the output of the physical quantity sensor assembly.

[0030] According to the twelfth method, the quality of the mobile body that can operate automatically is improved compared to the past. Attached Figure Description

[0031] Figure 1 This is a block diagram of the physical quantity sensor assembly according to the first embodiment.

[0032] Figure 2 This is an explanatory diagram of vibration rectification error.

[0033] Figure 3 This is an illustration of the structural resonant frequency.

[0034] Figure 4 This is a block diagram of the first low-pass filter in the first embodiment.

[0035] Figure 5 This is a block diagram of the second low-pass filter in the first embodiment.

[0036] Figure 6 This is an explanatory diagram illustrating the nonlinearity of the first embodiment.

[0037] Figure 7 This is an example of the experimental results of the first implementation method.

[0038] Figure 8 This is a cross-sectional schematic diagram of the physical quantity detector according to the second embodiment.

[0039] Figure 9 This is a three-dimensional schematic diagram of the physical quantity detection device according to the second embodiment.

[0040] Figure 10 This is a three-dimensional schematic diagram of the physical quantity detection device according to the second embodiment.

[0041] Figure 11 This is a top view of the physical quantity detection device according to the second embodiment.

[0042] Figure 12 This is a structural diagram of the acceleration physical quantity sensor according to the third embodiment.

[0043] Figure 13 This is a cross-sectional schematic diagram of the tilter according to the fourth embodiment.

[0044] Figure 14 This is a cross-sectional schematic diagram of the inertial measurement device according to the fifth embodiment.

[0045] Figure 15 This is a schematic structural diagram of the structure monitoring device according to the sixth embodiment.

[0046] Figure 16 This is a schematic structural diagram of the mobile body according to the seventh embodiment.

[0047] Explanation of reference numerals in the attached figures

[0048] 1…Physical quantity sensor assembly; 3…Frequency-varying physical quantity sensor; 5…Reference signal oscillation unit; 7…Frequency ratio measuring device; 10…Frequency Δ-Σ modulation unit; 20…First low-pass filter; 50…Third latch; 60…Second low-pass filter; 100…Physical quantity detector; 200…Physical quantity detection device; 300…Acceleration physical quantity sensor; 400…Inclinometer; 500…Inertial navigation device; 600…Structure monitoring device; 700…Moving body. Detailed Implementation

[0049] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Furthermore, the present invention is not limited by the embodiments described below, nor are the ways in which the present invention can be applied limited to the following embodiments.

[0050] [First Implementation Method]

[0051] <Composition>

[0052] Figure 1 This is a block diagram of the physical quantity sensor assembly 1 according to the first embodiment. Figure 1 The physical quantity sensor assembly 1 includes a frequency-varying physical quantity sensor 3, a reference signal oscillation unit 5, and a frequency ratio measuring device 7. The frequency-varying physical quantity sensor 3 is a physical quantity sensor whose frequency changes according to the change in the physical quantity of the object being detected, and outputs a periodic signal corresponding to the frequency as the measured signal. The frequency-varying physical quantity sensor 3 can be, for example, a quartz acceleration physical quantity sensor that measures acceleration as a physical quantity, or a quartz angular velocity physical quantity sensor that measures angular velocity as a physical quantity. The reference signal oscillation unit 5 outputs a reference signal based on a predetermined frequency. The frequency of this reference signal is higher than the frequency of the measured signal.

[0053] The frequency ratio measuring device 7 is a device that measures the frequency ratio between a measured signal and a reference signal based on a measured signal and a reference signal. Furthermore, the frequency ratio measuring device 7 measures the frequency ratio by a reciprocal counting method. Alternatively, it can be an action signal based on the measured signal, rather than the measured signal itself. The action signal based on the measured signal is a signal related to the measured signal and also includes the measured signal itself. The frequency ratio measuring device 7 includes a frequency Δ-Σ modulation unit 10, a first low-pass filter 20, a third latch 50, and a second low-pass filter 60.

[0054] The frequency Δ-Σ modulation unit 10 uses the measured signal output from the frequency-varying physical quantity sensor 3 to perform frequency Δ-Σ modulation on the reference signal output from the reference signal oscillation unit 5, generating a frequency Δ-Σ modulated signal. The frequency Δ-Σ modulation unit 10 includes a counter 12, a first latch 14, a second latch 16, and a subtractor 18. The counter 12 counts the rising edge of the reference signal and outputs count data representing the count value. The first latch 14 is synchronized with the rising edge of the measured signal, latches the count data, and outputs first data. The second latch 16 is synchronized with the rising edge of the measured signal, latches the first data, and outputs second data. The subtractor 18 subtracts the second data from the first data to generate output data. This output is the frequency Δ-Σ modulated signal generated by the frequency Δ-Σ modulation unit 10.

[0055] This frequency Δ-Σ modulation unit 10, also known as a first-order frequency Δ-Σ modulator, latches the count value of the reference signal twice using the measured signal as a trigger, and sequentially holds the count value of the reference signal by using the rising edge of the measured signal as a trigger. Although the latching operation is assumed to be performed on the rising edge in this example, the latching operation can also be performed on the falling edge or both the rising and falling edges. In addition, the subtractor 18 calculates the difference between the two held count values ​​and outputs the increment of the count value of the reference signal observed during one cycle of the measured signal without any insensitive period as time passes. When the frequency of the measured signal is set to fx and the frequency of the reference signal is set to fc, the frequency ratio is fc / fx. The frequency Δ-Σ modulation unit 10 outputs the frequency Δ-Σ modulated signal representing the frequency ratio as a digital signal train.

[0056] The first low-pass filter 20 is an example of a first filter. It is disposed on the output side of the frequency Δ-Σ modulation unit 10 and operates synchronously with the measured signal output by the frequency-varying physical quantity sensor 3, thereby removing or reducing the noise component contained in the frequency Δ-Σ modulation signal output by the frequency ratio measuring device 7.

[0057] The third latch 50 is synchronized with the rising edge of the reference signal, latches and outputs the output of the first low-pass filter 20.

[0058] The second low-pass filter 60 is an example of a second filter. It is disposed on the output side of the first low-pass filter 20, which is an example of a first filter. It operates synchronously with the reference signal to remove or reduce the noise component contained in the frequency Δ-Σ modulated signal output by the frequency ratio measuring device 7.

[0059] <Principles>

[0060] The frequency ratio measuring device 7 of this embodiment has the characteristic of correcting the nonlinearity of the measured signal, which is the output of the frequency-varying physical quantity sensor 3. For example, taking a quartz acceleration physical quantity sensor as an example, the frequency-varying physical quantity sensor 3 is a physical quantity sensor in which the oscillation frequency (vibration frequency) of the crystal oscillator changes according to the change of the force acting in the direction of the detection axis, and outputs a pulse-like signal corresponding to the oscillation frequency. The relationship between the applied acceleration and the oscillation frequency of the crystal oscillator is not a completely linear relationship (nonlinear), and there are individual differences in this relationship.

[0061] Figure 2 This diagram illustrates how a drift occurs in the DC component of the output value when a vibrational component is input into a system with a nonlinear input-output relationship. Conversely, if a sinusoidal signal is input into a system with a linear input-output relationship, the result is... Figure 2 The output value is represented by a solid curve. The DC component (solid line) obtained by rectifying this output value does not drift. On the other hand, if a sinusoidal signal is input to a system with a non-linear input-output relationship, a signal is obtained using... Figure 2 The output value is shown by a dotted curve. The DC component (dash line) obtained by rectifying this output value causes a distortion in the output waveform, resulting in drift. The component that causes drift in the output when a vibration component is input into a system with a nonlinear input-output relationship is called vibration rectification error (VRE). Typically, VRE is a function of the frequency of the input vibration component. It is known that if the frequency of the input vibration component is constant, the magnitude of VRE is proportional to the square of the amplitude of the input vibration component.

[0062] Figure 3In the physical quantity sensor assembly 1 configured for acceleration detection before adjustment, the applied acceleration is plotted as a function of the applied frequency of the applied vibration rectification error constant (VRC). The magnitude of VRE is proportional to the square of the amplitude of the input vibration component, and the unit of VRC for the physical quantity sensor assembly for acceleration detection is provided as [G / G^2]. The peak value of VRC observed near 820Hz represents a value 4 to 5 bits larger than other frequency regions. In the structural resonance determined by the structure of the physical quantity sensor assembly, its structural resonance frequency is around 820Hz. If the input vibration component contains a frequency of around 820Hz, it causes structural resonance of the physical quantity sensor assembly. In practice, this is due to the frequency component corresponding to the structural resonance frequency being amplified and output. As a result, the drift caused by structural resonance becomes the biggest factor affecting VRE, requiring special countermeasures.

[0063] The frequency ratio measuring device 7 corrects the measured signal, which is the output of the frequency-varying physical quantity sensor 3 with nonlinearity. In particular, by reducing the VRE caused by structural resonance, the nonlinearity of the acceleration acting on the frequency-varying physical quantity sensor 3 and the output of the frequency ratio measuring device 7 can be reduced.

[0064] Figure 4 This is a block diagram of the first low-pass filter 20. According to... Figure 4 The first low-pass filter 20 includes a first adder 22, a first delay element 24, a first subtractor 26, a second adder 28, a third adder 30, a decimation filter 32, a second delay element 34, a second subtractor 36, a third delay element 38, and a third subtractor 40. Each part of the first low-pass filter 20 operates synchronously with the measured signal. The delay numbers n1 to n3 of each of the first delay element 24, the second delay element 34, and the third delay element 38, which are the filter taps, can be set by changing them externally to the physical quantity sensor assembly 1. In the components of the first low-pass filter 20, the first adder 22, the first delay element 24, and the first subtractor 26 form the initial portion that functions as a moving average filter. In addition, the latter part of the components of the first low-pass filter 20, including the second adder 28, the third adder 30, the decimation filter 32, the second delay element 34, the second subtractor 36, the third delay element 38, and the third subtractor 40, functions as a CIC (Cascaded Integrator Comb) filter.

[0065] Figure 5 This is a block diagram of the second low-pass filter 60. According to... Figure 4The second low-pass filter 60 includes a fourth adder 62, a fourth delay element 64, and a fourth subtractor 66. Each part of the second low-pass filter 60 operates synchronously with the reference signal. The delay number n4 of the fourth delay element 64, which serves as the filter tap number, can be set and changed externally from the physical quantity sensor assembly 1. Furthermore, the second low-pass filter 60 functions as a moving average filter.

[0066] By setting the number of filter taps n1 to n3 of the first low-pass filter 20 and the number of filter taps n4 of the second low-pass filter 60, the nonlinearity of the input-output characteristics of the frequency ratio measuring device 7 is achieved. Specifically, when the sampling ratio of the CIC filter is set to R, the output phase is delayed by (n1-1+R·(n2+n3-1)) / 2 clock cycles according to the input of the first low-pass filter 20, which operates according to the measured signal. The nonlinearity of the input-output characteristics is achieved by the second low-pass filter 60, which operates according to the reference signal, taking only the output of the first low-pass filter 20 with a sampling number n4 and smoothing it. The first low-pass filter 20 functions as a multi-segment moving average filter, and the second low-pass filter 60 functions as a moving average filter, smoothing the input signal and outputting it. In the first low-pass filter 20 and the second low-pass filter 60, the cutoff frequency (cutoff frequency) and smoothing timing can be adjusted by changing the delay number n1 to n4 of each delay element. Furthermore, the cutoff frequency achieved by the combination of the first low-pass filter and the second low-pass filter 60 of the frequency-varying physical quantity sensor 3 is fixed to be lower than the structural resonant frequency of the frequency-varying physical quantity sensor 3, thus reducing the influence of output modulation caused by structural resonance.

[0067] Figure 6 This is a schematic diagram illustrating the principle by which the frequency ratio measuring device 7 detects nonlinearity (vibration rectification error) relative to the vibration input through the input-output characteristics of the first low-pass filter 20 and the second low-pass filter 60. (Frequency-related information is missing.) Figure 6 (1) through (3) use the rightward direction facing the paper as the elapsed time, and the reference signal, the measured signal, and the sampled signal are shown sequentially from top to bottom. The reference signal and the measured signal are represented by short vertical lines indicating the timing of the rising edge. Regarding the measured signal, the output signal value of the first low-pass filter 20, representing the timing action of the rising edge of the measured signal, is recorded together between the timings of each rising edge. For ease of qualitative explanation, the frequencies (periods) of the reference signal, the measured signal, and the sampled signal are plotted in a simple ratio manner. It should be noted that although only the input value with a phase difference is shown as the output value of the first low-pass filter, the same explanation can be given below using any first low-pass filter output value at any frequency ratio.

[0068] The sampled signal is the signal output from the second low-pass filter 60. At the rising edge of the reference signal, the second low-pass filter 60, through a third latch 50 that operates synchronously with the same reference signal, takes in the output signal of the first low-pass filter 20 and outputs the smoothed result. Figure 6 In the diagram, focusing on the timing t1 of a specific action, the start and end times of the smoothing period are indicated by short vertical lines. As the smoothing process progresses, the numerical values ​​representing the output signal are shown. Furthermore, the length of this smoothing period is determined by the clock period based on the reference signal and the delay number n4 of the fourth delay element 64 of the second low-pass filter 60.

[0069] The first low-pass filter 20, at the rising edge of the measured signal, takes in the output signal of the frequency Δ-Σ modulation unit 10 and outputs the result of smoothing processing. As the frequency Δ-Σ modulation signal of the output signal of the frequency Δ-Σ modulation unit 10, the frequency ratio of the measured signal frequency fx to the reference signal frequency fc is fc / fx. That is, the first low-pass filter 20 performs smoothing processing on the frequency ratio fc / fx between the measured signal and the reference signal. Furthermore, the length and delay of this smoothing period are determined by the clock period of the measured signal and the delay numbers n1, n2, and n3 of the first delay element 24, the second delay element 34, and the third delay element 38 of the first low-pass filter 20.

[0070] Figure 6 Example (1) shows an example where the ratio (reciprocal count value) of the frequency fc of the reference signal input to the frequency fx of the measured signal in the frequency ratio measuring device 7 is a fixed integer value. If the ratio of fc and fx is a fixed integer value, then the smoothing process of the first low-pass filter 20 is also fixed, becoming a value corresponding to the frequency fx of the measured signal. For ease of explanation, in Figure 6 In (1), the number of rising edges of the reference signal included between the timing of the rising edge of the measured signal is “4” as a value representing the output signal.

[0071] Furthermore, the second low-pass filter 60, at the rising timing of the reference signal, takes in the output signal of the first low-pass filter 20 and outputs the smoothed result. Figure 6 In the example, as a result of the smoothing process of the second low-pass filter 60, the value of the product of the values ​​taken during smoothing is shown; in this example, the sampled signal is "64".

[0072] Figure 6 (2) relative to Figure 6(1) illustrates an example where, while maintaining the sum of the reciprocal counts of the repetition intervals of the measured signal, FM (Frequency Modulation) modulation is performed, and the delay numbers n1, n2, and n3 of the first delay element 24, the second delay element 34, and the third delay element 38 of the first low-pass filter 20 are adjusted so that the input and output phases are in phase. Through FM modulation, the timing of the rising edge of the measured signal varies periodically, and as a result of smoothing processing, the output value of the first low-pass filter 20 also varies periodically. Figure 6 In (2), the countdown value also changes to "5" or "3". This is because the second low-pass filter 60 multiplies the reference signal by "5" or "3", thereby weighting the countdown value according to timing. Figure 6 In (2), the phase of the input and the phase of the output are adjusted to be in phase, so the larger the reciprocal count value, the greater the weighting. In this example, the sampled signal is "68".

[0073] Figure 6 (3) shows that when the measured signal is such as Figure 6 The example shown in (2) is an example of adjusting the delay numbers n1, n2 and n3 of the first delay element 24, the second delay element 34 and the third delay element 38 of the first low-pass filter 20 in such a way that the phase of the input and the phase of the output are inverse phase.

[0074] Through FM modulation, the timing of the rising edge of the measured signal varies periodically, and the output value of the first low-pass filter 20, as a result of smoothing processing, also varies periodically. Figure 6 The situation is the same as in (2), in Figure 6 In (3), the countdown value also changes to "5" or "3", but becomes the same as... Figure 6 (2) The phase is opposite. The second low-pass filter 60 is multiplied by "5" or "3" according to the reference signal, and therefore the reciprocal count value is also weighted according to the timing, but in Figure 6 In (3), the phase of the input and the phase of the output are adjusted to be opposite, so the smaller the reciprocal count value, the greater the weighting. The sampled signal in this example is "60".

[0075] Typically, by applying FM (Frequency Modulation) modulation to the measured signal, the drift of the DC component in the sampled signal, which serves as the output of a second low-pass filter, can be controlled by adjusting the input and output phases. Figure 6In the example, the sampled signal "64" without drift can be adjusted to the sampled signal "68" (with a maximum drift of "+4") by setting the input-output relationship with the first low-pass filter to be in phase, and to the sampled signal "60" (with a minimum drift of "-4") by setting the input-output relationship of the first low-pass filter to be out of phase. In addition, the drift amount of these intermediate values ​​can also be controlled by adjusting the phase relationship of the first low-pass filter.

[0076] Furthermore, through the aforementioned mechanism, even if a mechanism for adjusting the output timing of the first low-pass filter is provided, the output signal of the second low-pass filter 60 can still change, thus enabling control of the drift amount without altering the cutoff frequency.

[0077] In addition, in such Figure 6 If the frequency (also known as period) of the measured signal shown in (1) does not change, even if the output timing of the first low-pass filter 20 is delayed, the length of the smoothing period of the first low-pass filter 20 or its processing result will not change due to the output timing, so the output of the second low-pass filter 60 does not change.

[0078] In this way, by setting and changing the second delay element 34 of the first low-pass filter 20, and the delay numbers n2 and n3 of the second delay element 34, the timing of the output of the first low-pass filter 20 can be delayed. As a result, the input-output characteristics of the relationship between the frequency of the output signal input to the frequency ratio measuring device 7 and the frequency of the measured signal can exhibit nonlinearity, and the drift amount can be controlled.

[0079] In the above example, the drift amount (0→±4) based on FM (Frequency Modulation) modulation (reciprocal count: 4, 4, 4, 4→5, 5, 3, 3) while maintaining the sum of the reciprocal counts of the repeated intervals of the measured signal. However, if we consider the case where the FM modulation amount is doubled (reciprocal count: 4, 4, 4, 4→6, 6, 2, 2), then the drift amount is 0→±16, and the drift amount is proportional to the square of the FM modulation amount. On the other hand, in the output of the frequency-varying physical quantity sensor 3, if the frequency of the input vibration component is constant, the magnitude of the vibration rectification error is proportional to the square of the amplitude of the input vibration component. Therefore, by adjusting the drift amount in a way that eliminates the vibration rectification error, the input-output relationship of the physical quantity sensor component 1 can be made close to linear.

[0080] <Experimental Results>

[0081] Next, the experimental results of physical quantity sensor component 1 will be explained. Figure 7 This is an example of experimental results. In Figure 7In the diagram, with the horizontal axis representing time and the vertical axis representing acceleration, the output of the frequency ratio measuring device 7 is shown when acceleration is instantaneously applied by exciting the frequency-varying physical quantity sensor 3. When acceleration is applied to the frequency-varying physical quantity sensor 3, the oscillation frequency of the sensor changes, and the frequency ratio measuring device 7 outputs a signal representing this oscillation frequency. This output corresponds to the detected acceleration value of the physical quantity sensor assembly 1.

[0082] In addition, Figure 7 The diagram shows two cases where the input and output characteristics of the frequency ratio measuring device 7 differ. Figure 7 The upper side shows the output measurement results of the physical quantity sensor assembly 1 before adjusting the input and output characteristics of the first low-pass filter, and the lower side shows the output measurement results of the physical quantity sensor assembly 1 after adjusting the input and output characteristics of the first low-pass filter.

[0083] Each impact is applied in a pulse-like manner with a timing interval of approximately 0.05 seconds. If acceleration is applied to the frequency-varying physical quantity sensor 3, the acceleration detected by the physical quantity sensor assembly 1 changes. In either case, as a change in acceleration (detected value), although the amplitude gradually stabilizes after a large change, the pulse waveform contains a wide range of frequency components, thus exciting structural resonance. The central value of the vibration differs after the timing of the applied acceleration (after excitation). That is, in... Figure 7 In the output of the physical quantity sensor assembly 1 shown on the upper side before adjusting the input-output characteristics of the first low-pass filter, the center value of the vibration after excitation drifts from the initial value. This drift portion Δ (in Figure 7 In the figure, approximately 200 mG represents the vibration rectification error. As time passes, the central value of the vibration approaches the initial value, and the drift is mitigated. However, it is observed that at 0.4 seconds, which is the right end of the graph, the initial value has not yet been returned.

[0084] On the other hand, Figure 7 As shown on the lower side, in the output of the physical quantity sensor assembly 1 after adjusting the input-output characteristics of the first low-pass filter, the central value of the excited vibration immediately converges to the initial value, and the drift component is reduced. That is, the input-output characteristics of the relationship between the frequency of the output signal and the frequency of the input signal compared to the frequency of the measured signal of the measuring device 7 are nonlinear, and the vibration rectification error is corrected by controlling the amount of drift.

[0085] <Effects>

[0086] According to the first embodiment, by changing the delay number n1 to n4 of the filter taps of the first low-pass filter 20 and the second low-pass filter 60, the input-output characteristics of the frequency ratio measuring device 7 can be made to have a so-called "inverse (axisymmetric)" nonlinearity relative to the applied acceleration and oscillation frequency of the frequency-varying physical quantity sensor 3. Thus, by canceling the nonlinearity of the measured signal, which is the output of the frequency-varying physical quantity sensor 3, through the "inverse" nonlinearity of the input-output characteristics of the frequency ratio measuring device 7, the relationship between the acceleration acting on the frequency-varying physical quantity sensor 3 and the output can be made approximately linear as a whole, for the physical quantity sensor assembly 1.

[0087] The first low-pass filter 20 and the second low-pass filter 60 are filters located on the output side of the frequency Δ-Σ modulation unit 10, and are not dedicated circuits or mechanisms for correcting nonlinearity. Therefore, the nonlinearity of the physical quantity sensor can be corrected without increasing the size of the physical quantity sensor assembly 1.

[0088] <Variation Example>

[0089] Furthermore, in the first embodiment, the setting of the delay numbers n2 and n3 of the filter taps serving as the first low-pass filter 20 was described, but the setting of the delay number n1 and the delay number n4 of the filter taps serving as the second low-pass filter 60 can also be changed. In the first low-pass filter 20, the input signal is downsampled by the decimation filter 32. Therefore, compared with the adjustment of the delay numbers n2 and n3 of the second delay element 34 and the third delay element 38 after the decimation filter 32, the adjustment of the delay number n1 of the first delay element 24 at the beginning, even if the delay number is the same, results in a smaller delay amount (delay time) in the smoothing timing. That is, the first low-pass filter 20 has a first delay element 24 formed in a way that allows for a smaller (more detailed) adjustment of the number of filter taps in the smoothing timing, a second delay element 34 formed in a way that allows for a larger (more coarse) adjustment of the number of filter taps, thereby enabling the smoothing timing to be changed with multiple filter taps of different densities. Therefore, the degree of correction of the measured signal, which is the output of the frequency-varying physical quantity sensor 3, can be easily adjusted.

[0090] [Second Implementation]

[0091] Next, the second embodiment will be described. In the following text, the differences from the first embodiment will be mainly described; for components identical to those in the first embodiment, the same symbols will be used, and repeated descriptions will be omitted. The second embodiment is an embodiment of the physical quantity detector of the physical quantity sensor assembly 1 of the first embodiment.

[0092] Figure 8 This is a schematic cross-sectional view showing the internal structure of the physical quantity detector 100 according to the second embodiment. The physical quantity detector 100 includes a physical quantity detection device 200, which is a frequency-varying physical quantity sensor 3 according to the first embodiment, an electronic circuit 140, and a package 102 that houses the physical quantity detection device 200 and the electronic circuit 140.

[0093] The package 102 has a package base 104 and a cover plate 106. The package 102 is connected to the package base 104 via a cover plate bonding material 108, covering the upper part of the package base 104 which has recesses, thereby defining an internal space and supporting a fixed physical quantity detection device 200 and electronic circuitry 140 within this internal space. The package base 104 can be made of materials such as ceramic, quartz, glass, or silicon. The cover plate 106 can be made of the same material as the package base 104, or a metal such as an alloy of iron (Fe) and nickel (Ni), or stainless steel. The cover plate bonding material 108 can be, for example, a weld ring, low-melting-point glass, or an inorganic adhesive.

[0094] Inside the encapsulation base 104, a stepped portion 110 is provided along the inner wall for supporting and fixing the physical quantity detection device 200 on its upper surface. In addition, an internal terminal 114 is provided on the upper surface of the stepped portion 110, which is electrically connected to the fixing portion connection terminal of the physical quantity detection device 200.

[0095] An external terminal 116 for use when mounting external components is provided on the outer bottom surface of the package base 104. The external terminal 116 is electrically connected to the internal terminal 114 via internal wiring (not shown). The internal terminal 114 and the external terminal 116 are made of a metal film, for example, a film of nickel (Ni), gold (Au), etc., laminated on a metallization film layer of tungsten (W) or the like by electroplating.

[0096] A through hole 120 is formed at the bottom of the packaging base 104, extending from the outer bottom surface to the inner bottom surface. Figure 8 In the example shown, the through-hole 120 is formed as a step with an outer diameter larger than the inner diameter. A sealing portion 122 is provided within this through-hole 120 to hermetically seal the interior (cavity) of the package 102. The sealing portion 122 is formed by depositing a sealing material, such as an alloy of gold (Au) and germanium (Ge), solder, etc., into the through-hole 120, which is then melted by heating and solidified. After the cover plate 106 is joined to the package base 104, the sealing material is placed within the through-hole 120 under a depressurized state (high vacuum state) inside the package 102, melted by heating, and then solidified to form the sealing portion 122, thereby achieving a hermetically sealed interior of the package 102. The interior of the package 102 can be filled with an inert gas such as nitrogen, helium, or argon.

[0097] The electronic circuit 140 provides a drive signal to the physical quantity detection device 200 via internal terminals 114, amplifies the supply frequency output from the physical quantity detection device 200, which varies according to the applied physical quantity such as acceleration, and outputs it to the outside of the physical quantity detector 100 via external terminals 116. Furthermore, the frequency ratio measuring device 7 or the reference signal oscillation unit 5 of the first embodiment is installed in this electronic circuit 140.

[0098] Figure 9 , Figure 10 This is a schematic three-dimensional view of the physical quantity detection device 200. Figure 10 For the sake of simplicity, the illustration of the mass part 210 has been omitted. Additionally, Figure 11 This is a top view of the physical quantity detection device 200. The physical quantity detection device 200 has a base 202 supported at its four corners by a support portion, a movable portion 206 connected by a connector portion 204 extending from the base 202 and bending due to acceleration in the detection direction, and a physical quantity detection element 208.

[0099] The physical quantity sensing element 208 is a double tuning fork type vibrating element formed, for example, by patterning a crystal substrate cut from a raw crystal at a predetermined angle using photolithography and etching techniques. Of course, the material of this element is not limited to crystal; piezoelectric materials such as lithium tantalate, lithium tetraborate, lithium niobate, lead zirconate titanate, zinc oxide, and aluminum nitride can also be used. Furthermore, semiconductor materials such as silicon with a piezoelectric material film of zinc oxide or aluminum nitride can also be used.

[0100] The physical quantity detection element 208 is formed as a beam spanning the connector portion 204. One end of the beam is fixed to the base portion 202, and the other end is fixed to the movable portion 206. It is configured such that signal lines (not shown) are connected to both ends of the physical quantity detection element 208, a predetermined current and voltage are applied, and the physical quantity detection element 208 vibrates at a predetermined frequency. Furthermore, if the movable portion 206 bends due to acceleration generated in the measurement direction, stress is applied to the beam portion of the physical quantity detection element 208, causing a change in the vibration frequency of the physical quantity detection element 208. A signal corresponding to the acceleration is generated based on this change in vibration frequency and output as the output signal of the physical quantity detection element 208.

[0101] [Third Implementation Method]

[0102] Next, the third embodiment will be described. In the following text, the differences from the first and second embodiments will be mainly described; for components identical to those in the first and second embodiments, the same symbols will be used and repeated descriptions will be omitted. The third embodiment is an embodiment of an acceleration physical quantity sensor using the physical quantity detector 100 of the second embodiment.

[0103] Figure 12 This is a schematic cross-sectional view illustrating the internal structure of the acceleration physical quantity sensor 300 according to the third embodiment. The acceleration physical quantity sensor 300 includes an electronic circuit board 310 and a receiving portion 320 for accommodating the electronic circuit board 310.

[0104] The receiving portion 320 divides the internal space by covering and sealing the lower outer casing 322 with an upper outer casing 324 that opens downwards. Moreover, the receiving portion 320 supports and fixes the electronic circuit board 310 in this internal space via an inner casing 326 or a pad 328.

[0105] The electronic circuit board 310 is equipped with three physical quantity detectors 100 (100x, 100y, 100z) of the same specifications according to the second embodiment, or an amplifier circuit for amplifying the output signals of each physical quantity detector 100 (100x, 100y, 100z).

[0106] The three physical quantity detectors 100x, 100y, and 100z mounted on the electronic circuit board 310 are physical quantity sensors that detect acceleration as a physical quantity, and output a signal corresponding to the acceleration detected in the detection direction. Furthermore, the three physical quantity detectors 100x, 100y, and 100z are mounted orthogonally to each other in their detection directions, and the acceleration physical quantity sensor 300 detects acceleration in the orthogonal three-axis directions, thus becoming a so-called triaxial acceleration physical quantity sensor.

[0107] [Fourth Implementation Method]

[0108] Next, the fourth embodiment will be described. In the following text, the differences from the first to third embodiments will be mainly described; for components identical to those in the first to third embodiments, the same symbols will be used and repeated descriptions will be omitted. The fourth embodiment is an embodiment of a tiltmeter using the acceleration physical quantity sensor 300 of the third embodiment.

[0109] Figure 13 This diagram illustrates a configuration example of the inclinometer 400 according to the fourth embodiment, and is a side view showing a partial cross-section. The inclinometer 400 is a device that outputs a signal corresponding to the tilt angle of the set position. The inclinometer 400 includes, within an internal space divided by a bottom housing 402 and an upper housing 404: an acceleration physical quantity sensor 300 according to the third embodiment; a calculation unit 410 that calculates the tilt angle based on the output signal of the acceleration physical quantity sensor 300; and an external output terminal 412 that outputs a signal corresponding to the tilt angle calculated by the calculation unit 410 to the outside. Of course, other elements may also be appropriately included. For example, a built-in battery, power supply circuit, wireless device, etc., may be included.

[0110] The calculation unit 410 is a circuit that calculates the tilt angle from the output signal of the acceleration physical quantity sensor 300 and outputs a signal corresponding to the tilt angle. For example, it can be implemented using a common IC (Integrated Circuit) or FPGA (Field Programmable Gate Array).

[0111] According to the inclinometer 400 of the fourth embodiment, by using the acceleration physical quantity sensor 300 of the physical quantity sensor assembly 1 of the first embodiment, the inclinometer can improve the inclinometer measurement accuracy compared to existing inclinometers.

[0112] [Fifth Implementation]

[0113] Next, the fifth embodiment will be described. In the following text, the differences from the first to fourth embodiments will be mainly described; for components identical to those in the first to fourth embodiments, the same symbols will be used and repeated descriptions will be omitted. The fifth embodiment is an embodiment of an inertial measurement device using the acceleration physical quantity sensor 300 of the third embodiment.

[0114] Figure 14 This diagram illustrates a configuration example of the inertial measurement unit 500 according to the fifth embodiment, and is a side view showing a partial cross-section. The inertial measurement unit 500 is a device mounted on a moving body. Within an internal space divided by a bottom housing 502 and an upper housing 504, it includes: an acceleration physical quantity sensor 300 according to the third embodiment; an angular velocity physical quantity sensor 510; a circuit unit 512 that calculates the posture of the moving body based on the output signals of the acceleration physical quantity sensor 300 and the angular velocity physical quantity sensor 510; and an external output terminal 514 that outputs a signal corresponding to the posture calculated by the circuit unit 512 to the outside. Of course, other elements can be appropriately included. For example, a built-in battery, a power supply circuit, a wireless device, etc., can be included.

[0115] The angular velocity physical quantity sensor 510 has basically the same structure as the acceleration physical quantity sensor 300, and is a so-called triaxial angular velocity physical quantity sensor that detects the angular velocities about the X-axis, Y-axis and Z-axis.

[0116] The circuit section 512 is implemented, for example, by a common IC (Integrated Circuit) or FPGA (Field Programmable Gate Array). It calculates the posture of the moving body equipped with the inertial measurement device 500 based on the output signals of the acceleration physical quantity sensor 300 and the angular velocity physical quantity sensor 510, and outputs a signal corresponding to the posture.

[0117] [Sixth Implementation Method]

[0118] Next, the sixth embodiment will be described. In the following text, the differences from the first to fifth embodiments will be mainly described; for components identical to those in the first to fifth embodiments, the same symbols will be used and repeated descriptions will be omitted. The sixth embodiment is an embodiment of a structure monitoring device using the acceleration physical quantity sensor 300 of the third embodiment.

[0119] Figure 15 This diagram illustrates a configuration example of the structure monitoring device 600 according to the sixth embodiment. The structure monitoring device 600 includes: an acceleration physical quantity sensor 300 of the third embodiment, installed on the structure 690 to be monitored; a transmitting unit 620 that transmits the detection signal from the acceleration physical quantity sensor 300; a receiving unit 636 that receives the transmitted signal from the transmitting unit 620 via a communication network 650; and a calculation unit 632 that calculates the tilt angle of the structure 690 based on the received signal from the receiving unit 636. The communication network 650 can be either wired or wireless.

[0120] The acceleration physical quantity sensor unit 610 is configured to house the acceleration physical quantity sensor 300 of the third embodiment, and a transmitter 620 including a communication component 622 and an antenna 644, which functions as a small communication terminal, within an internal space divided by the bottom housing 612 and the upper housing 614. Of course, the transmitter 620 can also be implemented as a communication component and antenna separate from the acceleration physical quantity sensor 300.

[0121] In this embodiment, the computing unit 632 is implemented using an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array) mounted on the monitoring computer 630. However, the computing unit 632 may also be configured as a processor such as a CPU (Central Processing Unit), which may be implemented in software by performing calculations on the program stored in the IC memory 634. The monitoring computer 630 accepts various operation inputs from the operator via the keyboard 638 and can display the results of the calculations on the touch panel 640.

[0122] The receiving unit 636 is implemented via a wired communication device or a wireless communication device connected to the communication network 650. In this embodiment, it is implemented via a communication component and antenna that communicates wirelessly with the transmitting unit 620, but it can also be implemented as a communication component and antenna that are separate from the monitoring computer 630.

[0123] [Seventh Implementation Method]

[0124] Next, the seventh embodiment will be described. In the following text, the differences from the first to sixth embodiments will be mainly described; for components identical to those in the first to sixth embodiments, the same symbols will be used and repeated descriptions will be omitted. The seventh embodiment is an embodiment of a moving body using the acceleration physical quantity sensor 300 of the third embodiment.

[0125] Figure 16 This diagram illustrates a configuration example of the mobile body 700 according to the seventh embodiment. In this embodiment, the mobile body 700 is shown as a passenger vehicle, but the type of vehicle can be appropriately changed. Alternatively, the mobile body 700 could also be a small boat, an automated guided vehicle, a factory transport vehicle, a forklift, etc.

[0126] The mobile body 700 includes: an acceleration physical quantity sensor 300 according to the third embodiment; and a control unit 710, which controls at least one of acceleration, braking and steering according to the detection signal of the acceleration physical quantity sensor 300, and can switch between automatic operation and non-automatic operation according to the detection signal of the acceleration physical quantity sensor 300.

[0127] The control unit 710 is implemented via an onboard computer. The control unit 710 is connected to various physical quantity sensors and controllers, such as the acceleration physical quantity sensor 300, throttle controller 712, brake controller 716, and steering wheel controller 720, via a communication network such as an in-vehicle LAN (Local Area Network), in a manner capable of receiving or transmitting signals. Here, the throttle controller 712 is a device that controls the output of the engine 714. The brake controller 716 is a device that controls the operation of the brake 718. The steering wheel controller 720 is a device that controls the operation of the power steering wheel 722. Furthermore, the types of physical quantity sensor controllers connected to the control unit 710 can be appropriately set, and are not limited to this.

[0128] Furthermore, the control unit 710 uses a built-in computing device to perform calculations based on the detection signal from the acceleration physical quantity sensor 300 to determine whether automatic operation should be implemented or not. When automatic operation is implemented, it sends control command signals to at least one of the throttle controller 712, brake controller 716, and steering wheel controller 720 to control at least one of acceleration, braking, and steering.

[0129] The automatic control parameters can be appropriately set. For example, during cornering, control can be implemented to prevent skidding or cornering when the acceleration detected by the acceleration sensor 300 reaches a threshold indicating a high risk of slippage or cornering out. Furthermore, during stopping, control can be implemented to forcibly engage emergency braking by fully closing the throttle valve when the acceleration detected by the acceleration sensor 300 reaches a threshold indicating a high risk of sudden forward or backward movement due to misoperation.

[0130] Furthermore, the embodiments applicable to this invention are not limited to those described above, and appropriate modifications can of course be made without departing from the spirit of this invention.

Claims

1. A frequency ratio measuring device, characterized in that, include: The frequency Δ-Σ modulation unit receives a first periodic signal and a second periodic signal with a period different from that of the first periodic signal, and uses a signal that is correlated with the first periodic signal to perform frequency Δ-Σ modulation on the second periodic signal to generate a frequency Δ-Σ modulated signal. The first filter is disposed on the output side of the frequency Δ-Σ modulation section and operates synchronously with the first periodic signal; A second filter is disposed on the output side of the first filter and operates synchronously with the second periodic signal; and A latch, positioned between the first filter and the second filter, operates synchronously with the second periodic signal. The frequency ratio measuring device measures the frequency ratio between the first periodic signal and the second periodic signal. The cutoff frequencies of the first filter, the latch, and the second filter are lower than the frequencies contained in the first periodic signal.

2. The frequency ratio measuring device according to claim 1, characterized in that, The first filter includes an adder, a delay element, and a subtractor, and the delay amount can be adjusted according to the number of taps of the delay element.

3. The frequency ratio measuring device according to claim 2, characterized in that, The first filter includes a decimation filter. The delay elements are respectively disposed on the input side and the output side of the decimation filter.

4. The frequency ratio measuring device according to claim 2 or 3, characterized in that, The second filter includes an adder, a delay element, and a subtractor, and the delay amount can be adjusted according to the number of taps of the delay element.

5. The frequency ratio measuring device according to claim 4, characterized in that, The nonlinearity of the input-output characteristics can be adjusted by changing the number of taps of the delay element in at least one of the first and second filters.

6. The frequency ratio measuring device according to claim 2 or 3, characterized in that, The first filter is a smoothing filter whose smoothing timing can be changed by adjusting the number of taps in the first filter. The number of taps of the first filter is set at a smoothing timing that reduces the rectification error of the first periodic signal.

7. The frequency ratio measuring device according to claim 2 or 3, characterized in that, The number of taps of the delay element in at least one of the first and second filters can be changed externally.

8. The frequency ratio measuring device according to claim 6, characterized in that, The first filter can change the smoothing timing by varying the density of multiple taps in the smoothing timing.

9. The frequency ratio measuring device according to any one of claims 1 to 3, characterized in that, The frequency of the second periodic signal is higher than the frequency of the first periodic signal.

10. A physical quantity sensor assembly, characterized in that, include: The frequency ratio measuring device according to any one of claims 1 to 9; as well as Physical quantity sensor, The first periodic signal is the signal output by the physical quantity sensor.

11. A mobile body, characterized in that, include: The frequency ratio measuring device according to any one of claims 1 to 9.

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