Patent ID: 12196776

DESCRIPTION OF EXEMPLARY EMBODIMENTS

First Embodiment

Outline of Inertial Sensor Device

FIG.1is a perspective view showing an outline of an inertial sensor device.FIG.2is a transparent plan view of the inertial sensor device.FIG.3is an exploded perspective view of an internal configuration of the inertial sensor device.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Each embodiment exemplifies a device and method for embodying the technical idea of the present disclosure. The technical idea of the present disclosure does not specify the materials, shapes, structures, arrangements, and the like of components to those described below. In the drawings, the same or similar elements are denoted by the same or similar reference numerals, and redundant description thereof will be omitted. The drawings are schematic and may be different from actual dimensions, relative ratios of dimensions, arrangements, structures, and the like.

As shown inFIGS.1to3, an inertial sensor device1according to the embodiment includes, for example, a substrate10, a first sensor module2A, a second sensor module2B, and a third sensor module2C, which are mounted on the substrate10, a processing circuit100, and a container9. The inertial sensor device1is a composite sensor module including a plurality of inertial sensors that detect accelerations in three axis directions and angular velocities around three axes. The inertial sensor device1detects, for example, motion states of a moving body such as a vehicle, a robot, or a drone, an electronic device such as a smartphone or a tablet terminal, and various other targets. The motion state includes a position, a posture, a speed, an acceleration, an angular velocity, and the like.

As shown inFIGS.1and2, the container9includes a base91having a recess911opening upward, and a lid92fixed to the base91so as to close an opening of the recess911. The container9has a substantially rectangular flat plate shape. The base91and the lid92define an accommodating space S inside the recess911sealed by the lid92. The accommodating space S is a space for accommodating components such as the substrate10, the first sensor module2A, the second sensor module2B, the third sensor module2C, and the processing circuit100. The container9protects the components accommodated in the accommodating space S from dust, moisture, ultraviolet light, impact, and the like.

The base91and the lid92may be made of aluminum (Al). In addition, for example, a metal material such as an Al alloy, zinc (Zn), and stainless steel, various ceramics, various resin materials, and a composite material thereof can be adopted as a material of each of the base91and the lid92.

The inertial sensor device1includes a connector93attached to a side wall of the base91, and a communication board931disposed in the accommodating space S. The connector93is a receptacle for electrical coupling between inside and outside of the container9. The communication board931includes a circuit that processes communication between the inertial sensor device1and an external device.

The substrate10is a circuit board including various elements and wirings. The first sensor module2A, the second sensor module2B, the third sensor module2C, the processing circuit100, an internal connector110, and the like are mounted on the substrate10. The substrate10is fixed relative to, for example, the base91.

As shown inFIGS.2and3, the first sensor module2A and the second sensor module2B are arranged along an X axis on a lower surface of the substrate10. The third sensor module2C is disposed on an upper surface of the substrate10so as to overlap the first sensor module2A when viewed from a direction along a Z axis. The processing circuit100and the internal connector110are disposed on the upper surface of the substrate10so as to overlap the second sensor module2B when viewed from the direction along the Z axis. In this way, a size of the inertial sensor device1can be reduced by efficiently disposing various components with respect to an area of the substrate10and the accommodating space S.

The first sensor module2A, the second sensor module2B, and the third sensor module2C are coupled to the processing circuit100via the substrate10. The processing circuit100controls driving of the first sensor module2A, the second sensor module2B, and the third sensor module2C. The processing circuit100is coupled to the communication board931via the internal connector110and a wiring (not shown) coupled to the internal connector110.

The first sensor module2A, the second sensor module2B, and the third sensor module2C have the same structure, for example. Hereinafter, any one of the first sensor module2A, the second sensor module2B, and the third sensor module2C will be simply referred to as a “sensor module2”, and redundant description thereof will be omitted. The sensor module is also referred to as an inertial measurement module. The number of sensor modules2is not limited to three, and may be two or four or more.

Configuration of Sensor Module

FIG.4is an exploded perspective view of the sensor module.FIG.5is a front view of the circuit board.FIG.6is a rear view of the circuit board.

As shown inFIG.4, the sensor module2includes an outer case21, an inner case22, a joining member23, and a circuit board24. The outer case21has a recess into which the inner case22is inserted. The outer case21and the inner case22are joined to each other by the joining member23while accommodating and holding the circuit board24. The sensor module2has a square shape when viewed from above, that is, from a direction along a c axis shown inFIG.4. The outer case21has, for example, screw holes211,212provided in a pair of corner portions located diagonally on an upper surface, respectively. The sensor module2can be fixed to the substrate10by being screwed using the screw holes211,212.

As shown inFIGS.5and6, a module connector25, a first angular velocity sensor26a, a second angular velocity sensor26b, a third angular velocity sensor26c, an acceleration sensor27, a signal processing unit28, and the like are mounted on the circuit board24. The module connector25couples the sensor module2to the substrate10. The module connector25is exposed to the substrate10through, for example, an opening221provided in the inner case22. The first angular velocity sensor26adetects an angular velocity ωa around an a axis. The second angular velocity sensor26bdetects an angular velocity ωb around a b axis. The third angular velocity sensor26cdetects an angular velocity ωc around a c axis. The acceleration sensor27detects an acceleration Aa in a direction along the a axis, an acceleration Ab in a direction along the b axis, and an acceleration Ac in a direction along the c axis. Three detection axes, namely a, b, c axes are defined for each sensor module2.

The signal processing unit28includes, for example, an integrated circuit (IC). The signal processing unit28is coupled to each of the first angular velocity sensor26a, the second angular velocity sensor26b, the third angular velocity sensor26c, and the acceleration sensor27via the circuit board24. The signal processing unit28is coupled to the processing circuit100via the circuit board24, the module connector25, the substrate10, and the like.

The circuit board24has, for example, a square shape when viewed from the direction along the c axis. When four quadrants defined around a center O of the circuit board24are a first quadrant Q1, a second quadrant Q2, a third quadrant Q3, and a fourth quadrant Q4, the acceleration sensor27is disposed in the first quadrant Q1. As shown inFIG.3, the first sensor module2A, the second sensor module2B, and the third sensor module2C are disposed such that first quadrants Q1thereof are close to each other.

That is, in an example shown inFIG.3, an acceleration sensor27A of the first sensor module2A and an acceleration sensor27C of the third sensor module2C are disposed so as to overlap each other when viewed from the direction along the Z axis. The acceleration sensor27A of the first sensor module2A and an acceleration sensor27B of the second sensor module2B are disposed so as to overlap each other when viewed from a direction along the X axis. This can reduce a difference in acceleration received by each of the acceleration sensor27A, the acceleration sensor27B, and the acceleration sensor27C.

The module connector25is disposed on an upper surface241of the circuit board24in the second quadrant Q2and the third quadrant Q3. The first angular velocity sensor26ais disposed on a side surface of the circuit board24in the fourth quadrant Q4. The second angular velocity sensor26bis disposed on a side surface of the circuit board24in the first quadrant Q1. The third angular velocity sensor26cis disposed on the upper surface241of the circuit board24in the fourth quadrant Q4. The acceleration sensor27is disposed on the upper surface241of the circuit board24in the first quadrant Q1. The signal processing unit28is disposed on a lower surface242of the circuit board24in the third quadrant Q3. The screw hole211is formed in the second quadrant Q2, and the screw hole212is formed in the fourth quadrant Q4.

Configuration of Sensor Module

FIG.7is a block diagram showing a circuit configuration of the sensor module.

As shown inFIG.7, the sensor module2includes an inertial sensor20including at least one of the first angular velocity sensor26a, the second angular velocity sensor26b, the third angular velocity sensor26c, and the acceleration sensor27, the signal processing unit28, a clocking unit32, a communication unit31, and a storage unit30. The communication unit31includes the module connector25(FIG.5). The storage unit30stores various parameters and the like used for correction in the signal processing unit28.

The inertial sensor20outputs a signal related to a plurality of detection axes to the signal processing unit28. The signal processing unit28corrects the signal output from the inertial sensor20such that the plurality of detection axes are orthogonal to each other. For example, the plurality of detection axes forming a three-dimensional orthogonal coordinate system are set for each sensor module2. In addition, the signal processing unit28corrects an offset error and a scale factor error included in the signal received from the inertial sensor20.

Then, corrected inertial data is read to the processing circuit100of the inertial sensor device1(FIG.10) at a timing synchronized with an output synchronization signal to be described later.

The clocking unit32is a timer circuit including a resonator such as a crystal resonator, and supplies a clock signal to the signal processing unit28.

The communication unit31is a digital interface circuit, and enables bidirectional communication with the processing circuit100of the inertial sensor device1(FIG.3) via the module connector25(FIG.5).

Problems in Related Art

FIG.8is a timing chart showing a relationship between detection data and output data.

The uppermost part ofFIG.8shows timings when reading inertial data in the first sensor module2A.

First, the first sensor module2A acquires inertial data at a timing of a clock in the own clocking unit32. A sampling period is, for example, 2 kHz, but is not limited thereto, and may be, for example, 20 kHz. Next, an output synchronization signal (data ready) is output at a timing when the inertial data in one sampling is acquired. A data ready signal is synchronized with the sampling period.

Here, since each sensor module2includes its own clocking unit32, the output synchronization signal is transmitted based on a clock of each sensor module2. Specifically, the first sensor module2A outputs the output synchronization signal at a timing of the clock in the own clocking unit32. The same applies to the second sensor module2B and the third sensor module2C.

When receiving the output synchronization signal, the processing circuit100of the inertial sensor device1reads the inertial data from the first sensor module2A in synchronization with the output synchronization signal, and stores the read inertial data as detection data Da[1] in a first storage unit41(FIG.10). At this time, the detection data Da[1] and a read time point Ta[1] of the data are stored as a pair. The time point Ta[1] is a time point when reading the detection data Da[1] based on a clock of a clocking unit40of the processing circuit100(FIG.10).

The same applies to the second sensor module2B, and an output synchronization signal (data ready) is output at a timing of a clock in the clocking unit32of the second sensor module2B. Then, inertial data is read in synchronization with the output synchronization signal, and detection data Db[1] and a time point Tb[1] are stored as a pair.

The same applies to the third sensor module2C, and an output synchronization signal (data ready) is output at a timing of a clock in the clocking unit32of the third sensor module2C. Then, inertial data is read in synchronization with the output synchronization signal, and detection data Dc[1] and a time point Tc[1] are stored as a pair.

Here, as shown inFIG.8, the read time point Ta[1] of the detection data Da[1] from the first sensor module2A and the read time point Tb[1] of the detection data Db[1] from the second sensor module2B slightly deviate from each other. In other words, it can be seen that a deviation occurs on the time axis between the read time point Ta[1] and the read time point Tb[1]. Similarly, jitter also occurs between the read time point Ta[1] and the read time point Tc[1] and between the read time point Tb[1] and the read time point Tc[1]. This is because each sensor module2includes its own clocking unit32and outputs the output synchronization signal based on the time point.

Here, when output data at Ts[1] is simply generated from Da[1], Db[1], and Dc[1], a deviation from the time point Ts[1] occurs on the time axis, in other words, data having a jitter error is used, resulting in an error in the output data.

As an example, a difference between the detection data Da[1] from the first sensor module2A and the detection data Db[1] from the second sensor module2B, that is, a jitter error will be considered.

FIG.9is a waveform diagram showing detection data70from the first sensor module2A and detection data71from the second sensor module2B when the same sine wave of 100 Hz is input to the first sensor module2A and the second sensor module2B, and a difference between the detection data70and the detection data71(error waveform72of jitter error), in a case where there is a frequency difference between the clock of the first sensor module2A and the clock of the second sensor module2B. A horizontal axis represents time (sec), and a vertical axis represents a signal level.

The waveform diagram inFIG.9is based on a simulation result, and the simulation is performed using a program on a personal computer (PC).

The error waveform72shows a beat waveform that gradually increases while oscillating with time, then returns to zero, and increases while oscillating with time, reaching a maximum value of about 25%.

In a case where there is a frequency difference between the clock of the second sensor module2B and the clock of the third sensor module2C, a jitter error similarly occurs between detection data from the second sensor module2B and detection data from the third sensor module2C when the same sine wave of 100 Hz is input to the second sensor module2B and the third sensor module2C.

Therefore, it is obvious that an error occurs by simply synthesizing the detection data Da[1] from the first sensor module2A, the detection data Db[1] from the second sensor module2B, and the detection data Dc[1] from the third sensor module2C.

Circuit Block Configuration of Processing Circuit in Inertial Sensor Device

FIG.10is a circuit block diagram of the processing circuit in the inertial sensor device.

As shown inFIG.10, the processing circuit100of the inertial sensor device1includes the clocking unit40, the first storage unit41, a second storage unit42, a synthesis processing unit43, a communication unit44, and the like.

The clocking unit40is a timer circuit including a resonator such as a crystal resonator, and supplies a clock signal and time point data to the synthesis processing unit43, the first storage unit41, and the like.

The first storage unit41is a buffer memory including a random access memory (RAM), and includes three storage areas41a,41b,41cfor each sensor module2. The storage area41ais a storage area for detection data Da[n] from the first sensor module2A, and a read time point Ta[n] thereof, and stores the detection data Da[n] and the read time point Ta[n] as a detection data pair (Ta[1], Da[1]) in which both are linked. The storage area41aensures a storage area capable of storing a plurality of sets of detection data pairs in time series. For example, five sets of detection data pairs can be stored. The number of sets is not limited to five, and may be any number necessary for interpolation processing to be described later. The same applies to the storage areas41b,41c. In other words, the first storage unit41stores the detection data from each of the plurality of sensor modules2in association with a time point of the clocking unit40.

The second storage unit42is a main memory including a read only memory (ROM) and a RAM, and stores a program to be executed by the synthesis processing unit43, related data, and the like. The program includes an interpolation processing program and the like to be described later. The first storage unit41may be provided as a part of the second storage unit42.

The synthesis processing unit43is a control unit of the processing circuit100, and includes one or more processors. The synthesis processing unit43executes interpolation processing on the detection data from each sensor module2for synchronization, and synthesizes a plurality of pieces of interpolated detection data to generate output data. Details of the interpolation processing will be described later.

The communication unit44is an interface circuit, and outputs the output data from the synthesis processing unit43to an external device from the connector93via the internal connector110(FIG.2) and the communication board931.

Interpolation Processing-1on Detection Data (Past Linear Interpolation)

Here, the interpolation processing on the detection data and a method for generating the output data by the synthesis processing unit43will be described with reference toFIGS.8and10. Main sync inFIG.8indicates a reference signal Ts[n] at a reference clock (2 kHz) in the clocking unit40of the processing circuit100.

In the present embodiment, the synthesis processing unit43obtains, using the latest two detection data pairs before a timing of a reference signal Ts[3], interpolation data at a timing of a previous reference signal Ts[2] by linear interpolation, for detection data from each sensor module2. The timing of the reference signal Ts[3] corresponds to a predetermined time point.

Specifically, for a detection data pair (Ta[n], Da[n]) from the first sensor module2A, linear interpolation calculation is performed using Equation (1) to obtain interpolation data DaTs[2] at the timing of the reference signal Ts[2]. Similarly, for the second sensor module2B, interpolation data DbTs[2] is obtained using Equation (2), and for the third sensor module2C, interpolation data DcTs[2] is obtained using Equation (3).
DaTs[2]=Da[2]+{(Da[3]−Da[2])/(Ta[3]−Ta[2])}*(Ts[2]−Ta[2])  Equation (1)
DbTs[2]=Db[2]+{(Db[3]−Db[2])/(Tb[3]−Tb[2])}*(Ts[2]−Tb[2])  Equation (2)
DcTs[2]=Dc[2]+{(Dc[3]−Dc[2])/(Tc[3]−Tc[2])}*(Ts[2]−Tc[2])  Equation (3)

In Equation (1), a change amount is acquired from a difference between the detection data Da[3] and the previous detection data Da[2], and a slope is calculated by dividing the change amount by a difference between the read time point Ta[3] and the read time point Ta[2]. An error change amount on the time axis is derived by multiplying the slope by a difference between a time point of the reference signal Ts[2] and the read time point Ta[2]. Then, Da[2], which is a base value of the detection data, is added.

Accordingly, the interpolation data DaTs[2] at the timing of the reference signal Ts[2] is derived. The same applies to Equations (2) and (3). In other words, the synthesis processing unit43calculates the interpolation data by interpolating the detection data at two time points using Equations (1) to (3) that are linear function equations. The timing of the reference signal Ts[3] as the predetermined time point is a time point after the read time point Ta[2] and the read time point Ta[3] as the two time points.

Next, a method for synthesizing the interpolation data DaTs[2], the interpolation data DbTs[2], and the interpolation data DcTs[2] that are obtained by Equations (1) to (3) will be described.

The synthesis processing unit43synthesizes the three pieces of interpolation data using Equation (4) to generate output data DsTs[3].
DsTs[3]=(DaTs[2]+DbTs[2]+DcTs[2])/3  Equation (4)

According to Equation (4), the synthesis processing unit43averages the interpolation data DaTs[2], the interpolation data DbTs[2], and the interpolation data DcTs[2] to generate the output data DsTs[3]. In other words, the synthesis processing unit43calculates interpolation data at a predetermined time point based on detection data from the first sensor module2A at at least two time points, and synthesizes, using interpolation data for each of the plurality of sensor modules2including the interpolation data, output data at the predetermined time point.

As described above, according to the inertial sensor device1of the present embodiment, the following effects can be attained.

The inertial sensor device1is an inertial sensor device including a plurality of sensor modules2having a first sensor module2A as a first inertial measurement module, and includes: the clocking unit40; the first storage unit41as a storage unit that stores detection data from each of the plurality of sensor modules2in association with a time point of the clocking unit40; and the synthesis processing unit43that calculates interpolation data at a predetermined time point based on detection data from the first sensor module2A at at least two time points, and synthesizes, using interpolation data for each of the plurality of sensor modules2including the interpolation data, output data at the predetermined time point.

According to this, the interpolation data synchronized at the predetermined time point is calculated for each inertial measurement module. Then, the synthesis processing unit43obtains and synthesizes an average value of the plurality of pieces of interpolation data whose time axes are matched to generate output data. Therefore, by executing the interpolation processing on the plurality of pieces of detection data discrete due to digital output, matching in a time axis direction can be performed, and thus jitter noise that changes with time can be reduced. When N pieces of detection data are synthesized, random noise can be reduced to 1/√ N, and thus detection accuracy can be improved.

Therefore, it is possible to provide the inertial sensor device1capable of appropriately synthesizing the detection data from the plurality of inertial measurement modules and having high detection accuracy.

The synthesis processing unit43calculates the interpolation data by interpolating the detection data at the two time points using Equations (1) to (3) that are linear function equations.

According to this, since the interpolation data can be calculated by a simple linear function equation, a storage capacity of the second storage unit42related to the interpolation processing can be reduced, and a load of arithmetic processing in the synthesis processing unit43can also be reduced.

The timing of the reference signal Ts[3] as the predetermined time point is the time point after the read time point Ta[2] and the read time point Ta[3] as the two time points.

According to this, the interpolation data can be obtained by linear interpolation using two detection data pairs before the predetermined time point.

Second Embodiment

Interpolation Processing-2on Detection Data (Past Secondary Interpolation)

In the above-described embodiment, the interpolation data is calculated by linearly interpolating the detection data at the two time points using the linear function equation, but the present disclosure is not limited to this method, and the interpolation data may be calculated by interpolating the detection data at n+1 or more time points using an n-th order function. Hereinafter, the same portions as those of the above-described embodiment are denoted by the same reference numerals, and redundant description thereof will be omitted.

In the present embodiment, the synthesis processing unit43obtains, using the latest three detection data pairs before a timing of the reference signal Ts[3], interpolation data at a timing of the previous reference signal Ts[2] by secondary interpolation, for detection data from each sensor module2.

First, a basic equation for secondary interpolation is Equation (5).
Dn[y]=a1*(Tn[x])2+b1*(Tn[x])+c1  Equation (5)

Specifically, for the first sensor module2A, the latest three detection data pairs (Ta[1], Da[1]), (Ta[2], Da[2]), and (Ta[3], Da[3]) in the past are substituted into Equation (5) to obtain Equations (6) to (8).
Da[1]=a1*(Ta[1])*(Ta[1])+b1*(Ta[1])+c1   Equation (6)
Da[2]=a1*(Ta[2])*(Ta[2])+b1*(Ta[2])+c1   Equation (7)
Da[3]=a1*(Ta[3])*(Ta[3])+b1*(Ta[3])+c1   Equation (8)

Then, simultaneous equations, namely Equations (6) to (8) are solved to obtain coefficients a1, b1, c1.

Similarly, for the second sensor module2B and the third sensor module2C, the latest three detection data pairs in the past are substituted into Equation (5) to obtain Equations (9) to (11) and Equations (12) to (14).
Db[1]=a2*(Tb[1])*(Tb[1])+b2*(Tb[1])+c2   Equation (9)
Db[2]=a2*(Tb[2])*(Tb[2])+b2*(Tb[2])+c2   Equation (10)
Db[3]=a2*(Tb[3])*(Tb[3])+b2*(Tb[3])+c2   Equation (11)

Then, simultaneous equations, namely Equations (9) to (11) are solved to obtain coefficients a2, b2, c2.
Dc[1]=a3*(Tc[1])*(Tc[1])+b3*(Tc[1])+c3   Equation (12)
Dc[2]=a3*(Tc[2])*(Tc[2])+b3*(Tc[2])+c3   Equation (13)
Dc[3]=a3*(Tc[3])*(Tc[3])+b3*(Tc[3])+c3   Equation (14)

Then, simultaneous equations, namely Equations (12) to (14) are solved to obtain coefficients a3, b3, c3.

Next, the interpolation data DaTs[2], DbTs[2], DcTs[2] at the timing of the reference signal Ts[2] are obtained by the secondary interpolation using Equations (15) to (16). In other words, the synthesis processing unit43calculates the interpolation data by interpolating the detection data at three time points using a quadratic function.
DaTs[2]=a1*Ts[2]2+b1*Ts[2]+c1  Equation (15)
DbTs[2]=a2*Ts[2]2+b2*Ts[2]+c2  Equation (16)
DcTs[2]=a3*Ts[2]2+b3*Ts[2]+c3  Equation (17)

Next, a method for synthesizing the interpolation data DaTs[2], DbTs[2], DcTs[2] that are obtained by Equations (15) to (17) will be described.

The synthesis processing unit43synthesizes the three pieces of interpolation data using Equation (18) to generate output data.
DsTs[3]=(DaTs[2]+DbTs[2]+DcTs[2])/3  Equation (18)

According to Equation (18), the synthesis processing unit43averages the interpolation data DaTs[2], the interpolation data DbTs[2], and the interpolation data DcTs[2] to generate the output data DsTs[3].

As described above, according to the inertial sensor device1of the present embodiment, the following effects can be attained in addition to the effects of the above-described embodiment.

The synthesis processing unit43calculates the interpolation data by interpolating the detection data at the three time points using the quadratic function. Specifically, the latest three detection data pairs in the past are substituted into Equation (5) to establish three simultaneous equations, the simultaneous equations are solved to obtain coefficients, and then the interpolation data at a timing of a reference signal immediately before a predetermined time point is calculated.

According to this, since the interpolation data is calculated by the secondary interpolation using a quadratic function equation, interpolation accuracy can be further improved. Therefore, jitter noise can be further reduced.

Therefore, it is possible to provide the inertial sensor device1capable of appropriately synthesizing the detection data from the plurality of inertial measurement modules and having high detection accuracy.

The synthesis processing unit43calculates the interpolation data by interpolating the detection data at n+1 or more time points using the n-th order function.

According to this, since the interpolation data is calculated by n-th order interpolation using an n-th order function equation, the interpolation accuracy can be further improved. Therefore, jitter noise can be further reduced.

Third Embodiment

Interpolation Processing-3on Detection Data (Future Linear Interpolation)

In the first embodiment, the interpolation data at the timing of the reference signal Ts[2] immediately before the predetermined time point is obtained by the linear interpolation, and interpolation data at a timing of the predetermined time point may be obtained. Hereinafter, the same portions as those of the above-described embodiment are denoted by the same reference numerals, and redundant description thereof will be omitted.

In the present embodiment, the synthesis processing unit43obtains, using the latest two pieces of data in the past at the timing Ts[3] as a predetermined time point, interpolation data at the timing Ts[3] by linear interpolation.

Specifically, for the detection data pair (Ta[n], Da[n]) from the first sensor module2A, linear interpolation calculation is performed using Equation (19) to obtain interpolation data DaTs[3] at the timing of the reference signal Ts[3]. Similarly, for the second sensor module2B, interpolation data DbTs[3] is obtained using Equation (20), and for the third sensor module2C, interpolation data DcTs[3] is obtained using Equation (21).
DaTs[3]=Da[3]+{(Da[3]−Da[2])/(Ta[3]−Ta[2])}*(Ts[3]−Ta[3])  Equation (19)
DbTs[3]=Db[3]+{(Db[3]−Db[2])/(Tb[3]−Tb[2])}*(Ts[3]−Tb[3])  Equation (20)
DcTs[3]=Dc[3]+{(Dc[3]−Dc[2])/(Tc[3]−Tc[2])}*(Ts[3]−Tc[3])  Equation (21)

In Equation (19), a change amount is acquired from a difference between the detection data Da[3] and the previous detection data Da[2], and a slope is calculated by dividing the change amount by a difference between the read time point Ta[3] and the read time point Ta[2]. An error change amount on the time axis is derived by multiplying the slope by a difference between a time point of the reference signal Ts[3] and the read time point Ta[3]. Then, Da[3], which is a base value of the detection data, is added.

Accordingly, the interpolation data DaTs[3] at the timing of the reference signal Ts[3] is derived. The same applies to Equations (20) and (21).

Then, the three pieces of interpolation data obtained from Equations (19) to (21) are synthesized using Equation (22). Specifically, the synthesis processing unit43averages the three pieces of interpolation data to generate the output data DsTs[3].
DsTs[3]=(DaTs[3]+DbTs[3]+DcTs[3])/3  Equation (22)

As described above, according to the inertial sensor device1of the present embodiment, the following effects can be attained in addition to the effects of the first embodiment.

The synthesis processing unit43obtains, using the latest two pieces of data in the past at the timing Ts[3] as the predetermined time point, the interpolation data at the timing Ts[3] by the linear interpolation.

According to this, the interpolation data at the timing Ts[3] as the predetermined time point can be derived without delay. Therefore, jitter noise can be reduced without delay.

Fourth Embodiment

Interpolation Processing-4on Detection Data (Future Secondary Interpolation)

In the second embodiment, the interpolation data at the timing of the reference signal Ts[2] immediately before the predetermined time point is obtained by the secondary interpolation, and interpolation data at a timing of the predetermined time point may be obtained. Hereinafter, the same portions as those of the above-described embodiment are denoted by the same reference numerals, and redundant description thereof will be omitted.

In the present embodiment, the synthesis processing unit43obtains, using the latest three detection data pairs before a timing of the reference signal Ts[3], interpolation data at a timing of the reference signal Ts[3], which is a predetermined time point, by secondary interpolation. The above Equation (5) is used as a basic equation of the secondary interpolation.

First, processing from Equation (6) to Equation (14) is the same as that described in the second embodiment. Specifically, for each sensor module2, the latest three detection data pairs in the past are substituted into Equation (5) to establish three simultaneous equations, and the simultaneous equations are solved to obtain three coefficients for each sensor module2.

The present embodiment is different from the second embodiment in that the interpolation data DaTs[3], DbTs[3], DcTs[3] at the timing of the reference signal Ts[3] are obtained by the secondary interpolation using Equations (23) to (25).
DaTs[3]=a1*Ts[3]2+b1*Ts[3]+c1  Equation (23)
DbTs[3]=a2*Ts[3]2+b2*Ts[3]+c2  Equation (24)
DcTs[3]=a3*Ts[3]2+b3*Ts[3]+c3  Equation (25)

Next, the interpolation data DaTs[3], DbTs[3], DcTs[3] obtained by Equations (23) to (25) are synthesized using Equation (26) to generate the output data DsTs[3].
DsTs[3]=(DaTs[3]+DbTs[3]+DcTs[3])/3  Equation (26)

According to Equation (26), the synthesis processing unit43averages the interpolation data DaTs[3], the interpolation data DbTs[3], and the interpolation data DcTs[3] to generate the output data DsTs[3].

As described above, according to the inertial sensor device1of the present embodiment, the following effects can be attained in addition to the effects of the second embodiment.

The synthesis processing unit43obtains, using the latest three pieces of data in the past at the timing Ts[3] as the predetermined time point, the interpolation data at the timing Ts[3] by the secondary interpolation.

According to this, the interpolation data at the timing Ts[3] as the predetermined time point can be derived without delay. Therefore, jitter noise can be reduced without delay.

Fifth Embodiment

Different Aspects of Inertial Sensor Device

FIG.11is a perspective view showing a different aspect of the inertial sensor device, corresponding toFIG.3.FIG.12is a perspective view showing a different aspect of the inertial sensor device, corresponding toFIG.3.FIG.13is a perspective view showing a different aspect of the inertial sensor device, corresponding toFIG.3.

The inertial sensor device1is not limited to the aspect shown with reference toFIGS.1to3, and may be a different aspect.

For example, as shown inFIG.11, an inertial sensor device1A according to the present embodiment includes the first sensor module2A, the second sensor module2B, and the third sensor module2C, which are stacked in one direction, that is, a direction along the Z axis. The inertial sensor device1A further includes four substrates10A,10B,10C,10D, and the processing circuit100and the internal connector110that are mounted on the substrate10D. The substrates10A to10D are fixed relative to each other. The first sensor module2A is mounted on the substrate10A. The second sensor module2B is mounted on the substrate10B. The third sensor module2C is mounted on the substrate10C.

The first sensor module2A, the second sensor module2B, and the third sensor module2C are coupled to the processing circuit100in a daisy chain by a plurality of cables4a,4b,4c. The cables4a,4b,4ccouple the first sensor module2A, the second sensor module2B, the third sensor module2C to the processing circuit100via connectors mounted on the substrates10A,10B,10C, for example. In this way, coupling of the sensor modules2in series can improve a degree of freedom in design and easily increase the number of sensor modules. This can further improve an S/N ratio of an output signal.

As shown inFIG.12, an inertial sensor device1B according to the present embodiment includes the first sensor module2A, the second sensor module2B, and the third sensor module2C, which are arranged on the same plane. The inertial sensor device1B includes the substrates10A to10D arranged on one plane along an X-Y plane. As in the example shown inFIG.11, the first sensor module2A, the second sensor module2B, and the third sensor module2C are coupled to the processing circuit100in a daisy chain by the plurality of cables4a,4b,4c. Therefore, a degree of freedom in design can be improved, and the number of sensor modules can be easily increased.

As shown inFIG.13, an inertial sensor device1C according to the present embodiment includes one substrate10E instead of the plurality of substrates10A to10D arranged on the same plane. The first sensor module2A, the second sensor module2B, the third sensor module2C, the processing circuit100, and the internal connector110are mounted on the substrate10E. The substrate10E includes a wiring that couples the first sensor module2A, the second sensor module2B, and the third sensor module2C to the processing circuit100. The processing circuit100is coupled in parallel to each sensor module2, for example. Accordingly, a communication capacity can be used more efficiently than in a case of serial wiring.

The inertial sensor devices LA,1B,1C, can also attain the same operational effects as those of the above-described embodiments.