WO2020080544A1

WO2020080544A1 - Measuring device, component for measuring device, and operation processing device for measuring device

Info

Publication number: WO2020080544A1
Application number: PCT/JP2019/041213
Authority: WO
Inventors: 浩司藪野; 山本　泰之; 壮平松本
Original assignee: 国立大学法人筑波大学; 国立研究開発法人産業技術総合研究所
Priority date: 2018-10-19
Filing date: 2019-10-18
Publication date: 2020-04-23
Also published as: JP7362060B2; JPWO2020080544A1

Abstract

The present invention addresses the problem of improving sensitivity of a measuring device. In order to solve the problem, provided is a measuring device that detects a value that is equivalent to the physical quantity of a measurement target by the amplitudes of two vibrators, the measuring device comprising: a real cantilever (1B) as one of the two vibrators; an actuator (22) that applies a force in a preset displacement direction to the cantilever (1B); a vibration displacement detection unit that includes a displacement meter (23) of the cantilever (1B); and an operation processing device that simulates a cantilever (1A) that is virtually bonded with the cantilever (1B) so as to be capable of coupling with the cantilever (1B) as the other one of the two vibrators and that executes coupled control processing for driving and controlling the actuator (22) on the basis of the cantilever (1A) and the vibration displacement of the cantilever (1B) detected by the vibration displacement detection unit.

Description

Measuring device, parts for measuring device, and arithmetic processing unit for measuring device

The present invention relates to a measuring device for measuring mass, elasticity, and the like from the vibration behavior of a vibrating body such as a cantilever, a component for the measuring device, and a processing device for the measuring device.

Conventionally, as a technique for measuring mass and elasticity, two cantilevers of the same shape are provided on the same support member so that they can perform coupled vibration, and the measurement target added to the cantilever based on the shape of the natural vibration mode of the two cantilevers. A technique for measuring the minute mass of an object is disclosed (for example, refer to Patent Document 1). It is said that by coupling two cantilevers, it is possible to detect minute changes in mass and elasticity with high sensitivity as compared with the case of using one cantilever. The term "coupling" as used herein means that a part of the two cantilevers is connected by a very weak spring, and the displacement of one affects the displacement of the other.

JP, 2014-190771, A

In the above-mentioned prior art, it is known that the sensitivity is improved when the coupling effect of the two cantilevers is lower, and the sensitivity is improved as the physical characteristics of the two cantilevers are closer to each other. However, producing a cantilever that satisfies these two conditions is limited in terms of mechanical design and production. Therefore, it was difficult to realize higher sensitivity.
In addition, manufacturing two cantilevers that can be coupled is technically more difficult than manufacturing one cantilever, and has disadvantages such as deterioration of manufacturing yield, deterioration of complexity, and cost increase. It was happening.

Therefore, the present invention has been made by paying attention to the above-mentioned unsolved problems of the related art, and an object thereof is to provide a measuring device having higher sensitivity, a component for the measuring device, and an arithmetic processing device for the measuring device. There is.

In order to solve the above problems, in the present invention, one of the two coupled cantilevers is removed. Then, instead of the removed cantilever, the force that should be applied to the other cantilever when two cantilevers are coupled is theoretically calculated in real time and applied to the actuator attached to the other cantilever. As a result, only the other cantilever is vibrated as if the two cantilevers are coupled and vibrating. By doing this, only one cantilever needs to be manufactured, and it becomes possible to ideally approximate the physical characteristics of the cantilever, and it is also possible to ideally reduce the coupling effect. It becomes possible to solve the above problems.

That is, according to one aspect of the present invention, a measurement device that detects a value corresponding to a physical quantity of a measurement target by using the amplitudes of two vibrating bodies, and is used as one of the two vibrating bodies. The actual vibrating body, an actuator that applies a force in a preset displacement direction to the actual vibrating body, a vibration displacement detection unit that detects the vibrating displacement of the actual vibrating body, and a virtual vibrating body that can be coupled to each other. Coupling control that simulates the virtual vibrating body as one of the two vibrating bodies and drives and controls the actuator based on the vibrating displacement of the real vibrating body detected by the virtual vibrating body and the vibration displacement detection unit. Provided is a measuring device including an arithmetic processing device that executes a process.

According to another aspect of the present invention, there are provided a component for the measuring device according to the above aspect, which is an actual vibration body, an actuator that applies a force in a preset displacement direction to the real vibration body, and an actual vibration. Provided is a component for a measuring device, which includes a vibration displacement detection unit that detects a vibration displacement of a body.
Further, according to another aspect of the present invention, there is provided the arithmetic processing device for the measuring device according to the above aspect, which is virtually coupled to the actual vibrating body by using the vibration displacement of the actual vibrating body. There is provided an arithmetic processing device for a measuring device that simulates a virtual vibrating body and generates a signal for driving and controlling an actuator.

According to one aspect of the present invention, it is possible to easily realize a measuring device having higher sensitivity.

It is explanatory drawing for demonstrating the mass measuring method in the measuring device to which this invention is applied. It is a figure which shows an example of the equivalent model of the dynamic system of a vibration part. It is a schematic structure figure showing an example of a measuring device. It is a top view which shows an example of an actual vibrating body part. It is a front view which shows an example of an actual vibrating body part. It is a block diagram showing an example of dynamics of the whole measuring device. It is a figure for demonstrating a verification result. It is a figure for demonstrating a verification result. It is explanatory drawing for demonstrating the modification of the measuring device to which this invention is applied. It is a figure which shows an example of the equivalent model of the dynamic system of the vibration part in a modification.

Embodiments of the present invention will be described below with reference to the drawings.
It should be noted that in the following detailed description, numerous specific specific configurations are set forth in order to provide a thorough understanding of the embodiments of the invention. However, it is obvious that other embodiments can be implemented without being limited to such a specific specific configuration. Further, the following embodiments do not limit the invention according to the claims. In addition, not all of the combinations of features described in the embodiments are essential to the solving means of the invention.
In the present embodiment, a case will be described in which the measuring device measures the mass of a measurement target.

<Prior art mass measurement method>
First, a mass measuring method using a vibrating section having two vibrating bodies (for example, a cantilever) having the same spring rigidity and mass and provided on the same supporting member so as to be capable of coupled vibration is described. explain.

First, of the two vibrating bodies, a feedback value proportional to the vibration speed (displacement speed) of one of the vibrating bodies is positively fed back to give an equal excitation input to the two vibrating bodies. As a result, self-excited vibration is generated in the two vibrating bodies. Here, in order to generate self-excited vibration, the feedback gain is gradually increased (or decreased) from a preset value. Then, first, self-excited vibration occurs only in the low-order natural vibration mode. The amplitude ratio of the two vibrating bodies at this time strictly corresponds to the low-order natural vibration mode.
On the other hand, the measurement target is added to one of the two vibrating bodies, and the amplitude ratio when the self-excited vibration occurs is measured. Then, for example, the mass of the measurement target is measured from the change in the amplitude ratio when the measurement target is added to the amplitude ratio when the measurement target is not added.

FIG. 1A is a diagram showing a configuration example of the vibrating unit 1 when measuring the mass of a measurement object using such a mass measuring method.
As shown in FIG. 1A, the vibrating section 1 includes a cantilever 1A, a cantilever 1B, a support member 1C, and an overhang portion 1D.
The

cantilevers

1A and 1B are both made of the same material and have the same shape, and are arranged in parallel (coupled) with the support member 1C in a cantilever state in which one end is fixed to the support member 1C and the other end is a free end. There is. That is, the

cantilevers

1A and 1B have the same spring rigidity and mass.

Further, the root portions of the

cantilevers

1A and 1B on the fixed end side are connected by an overhang portion 1D formed so as to project from the support member 1C. The overhang portion 1D plays a role of a vibration transmitting portion for transmitting vibration between the

cantilevers

1A and 1B, and the overhang portion 1D has a structure in which the

cantilevers

1A and 1B are coupled and vibrated.
In FIG. 1A, an object to be measured is attached to the cantilever 1B, and the

cantilevers

1A and 1B are externally displaced as velocity feedback to generate self-excited vibrations in the

cantilevers

1A and 1B.

<Mass measuring method in the present embodiment>
When measuring the mass of an object to be measured using such a mass measuring method, the measuring device according to the present embodiment, as shown in FIG. 1B, cantilever 1A and overhang portion 1D (support member 1C). Is implemented as a virtual model on an arithmetic processing unit including a digital signal processor (DSP) or the like.

[Equivalent model]
FIG. 2 is a diagram showing an example of an equivalent model of the dynamic system of the vibrating section 1 included in the measuring device according to the present embodiment.
As shown in FIG. 2, the vibrating section 1 is an equivalent model of a “spring-mass (mass) -damper” system (hereinafter also referred to as a coupled model) in which two coupled

cantilevers

1A and 1B are taken into consideration. .) Think as.
In the coupled model shown in FIG. 2, the cantilever 1A includes a first spring a1 having a spring constant k whose one end is supported by a supporting member 1C and a first damper a2 having a damping constant c whose one end is supported by the supporting member 1C. , The first spring a1 and the first object a3 having a mass m supported by the other end of the first damper a2.

Similarly, as shown in FIG. 2, the cantilever 1B includes a second spring b1 having a spring constant k supported at one end by a supporting member 1C and a second damper b2 having a damping constant c supported at one end by the supporting member 1C. And a second object b3 having a mass m supported by the other end of the second spring and the second damper, and a model in which a measurement object having a mass Δm is added to the second object b3 having a mass m. Becomes That is, each of the

cantilevers

1A and 1B has the same mass as the first spring a1 or the second spring b1 having the same spring constant k and the first damper a2 or the second damper b2 having the same damping constant c. The model is provided with each of the first object a3 and the second object b3 that it has.

Further, in the coupled model shown in FIG. 2, as shown in FIG. 2, the first object a3 and the second object b3 are connected by the third spring c1 having the spring constant kc. The third spring c1 having the spring constant kc corresponds to the overhang portion 1D in FIG. 1 and represents the coupled effect of the two

cantilevers

1A and 1B.
Then, in the measuring device according to the present embodiment, a portion surrounded by a broken line in FIG. 2 is simulated as a virtual model.

Here, in the equivalent model shown in FIG. 2, an exciting force F is further applied from the outside to the support points of the cantilevers (virtual vibrating body) 1A and the cantilevers (actual vibrating body) 1B. At this time, the equation of motion of the system (coupling model of FIG. 2) is as shown in the following equations (1) and (2). The equation (1) shows the equation of motion of the virtual model including the cantilever 1A, and the equation (2) shows the equation of motion of the existing cantilever 1B.
m ・ (d ² x1 / dt ² ) + c ・ (dx1 / dt)
+ (K + kc) * x1-kc * x2 = F
… (1)
(m + Δm) ・ (d ² x2 / dt ² ) + c ・ (dx2 / dt)
-Kc · x1 + (k + kc) · x2 = F
… (2)

In the equations (1) and (2), x1 is the displacement of the cantilever 1A, dx1 / dt is the first-order differential value of the displacement of the cantilever 1A, and d ² x1 / dt ² is the second-order differential value of the displacement of the cantilever 1A. x2 displacement of the cantilever 1B, dx2 / dt is the first derivative value of the cantilever ^1B, d ² x2 / dt 2 is the second order differential value of the cantilever 1B.

Here, an external excitation force F applied to the

cantilevers

1A and 1B so as to generate self-excited oscillation is given by the following equation (3) using the displacement x2 of the cantilever 1B. It should be noted that b in the equation (3) is a feedback gain set to generate self-excited oscillation. The feedback gain b is set to the value of the feedback gain when the self-excited oscillation occurs in the actual measurement environment. This feedback gain b does not need to be updated unless the measurement environment changes, and may be updated when measurement is performed in a different measurement environment.
F = b · dx2 / dt (3)

The expressions (1) and (2) can be rewritten into the following expressions (4) and (5) using the expression (3).
m ・ (d ² x1 / dt ² ) + c ・ (dx1 / dt)
+ (K + kc) * x1-kc * x2 = b * (dx2 / dt)
… (4)
(m + Δm) ・ (d ² x2 / dt ² ) + c ・ (dx2 / dt)
-Kc · x1 + (k + kc) · x2 = b · (dx2 / dt)
… (5)

The expressions (4) and (5) can be replaced with the following expressions (6) and (7).
m ・ (d ² x1 / dt ² ) + c ・ (dx1 / dt)
+ (K + kc) * x1-kc * x2-b * (dx2 / dt) = 0
… (6)
(m + Δm) ・ (d ² x2 / dt ² ) + c ・ (dx2 / dt)
+ K · x2 = kc · (x1-x2) + b · (dx2 / dt)
… (7)

In the present embodiment, the equation of motion of equation (6) is virtually simulated using the fourth-order Runge-Kutta method in the arithmetic processing device. Further, the right side of the equation (7) is applied to the existing cantilever 1B as the exciting force F.
Here, in order to virtually simulate the equation (6) by the arithmetic processing device, the state variable X is set to the following equation (8), the equation (6) is converted into a state equation, and then the fourth-order Runge- It is solved using the Kutta method, and the state quantity (equation (10)) is derived from the state quantity (equation (9)) at time t after a unit step time, that is, at time t + h. At this time, the virtual displacement of the cantilever 1A is calculated as x1 (t + h), and the speed is calculated as dx1 (t + h).

The numerical calculation result is used for x1 (t) and dx1 (t) / dt in the expression (9). Further, x2 (t) and dx2 (t) / dt use the displacement measurement result of the existing cantilever 1B.
Next, in the equation of motion of equation (7), that is, the equation of motion of the existing cantilever 1B, the term on the right side is represented by the excitation force F.
That is, the equation of motion (7) is expressed by the following equation (11), where F is the excitation force.
(m + Δm) ・ (d ² x2 / dt ² ) + c ・ (dx2 / dt)
+ K · x2 = F
… (11)

Therefore, the exciting force F required to reproduce the expression (7) is expressed by the following expression (12).
F = kc · (x1-x2) + b · (dx2 / dt)
… (12)
That is, the exciting force F required to realize the equation (7) is the velocity feedback component (linear velocity feedback component) for self-oscillation and the displacement feedback (linear displacement feedback component) for simulating the coupling effect. Ingredient) and the sum.
From the above, the calculation necessary for simulating the coupled cantilever and the information to be fed back are known.

[Example of verification of equivalent model]
Next, in order to verify whether the simulation method of the virtual coupled model shown in FIG. 2 is correct, measurement was performed using a macro cantilever. This measurement was performed by the measuring device 100 shown in FIGS. 3 to 5, which simulates the virtual coupled model shown in FIG. In the measuring device 100, an additional mass as a measurement object was attached at a position 10 mm from the tip of the macro cantilever where the fixed end of the existing cantilever 1B was joined to the piezo actuator, and measurement was performed.

[Configuration of measuring device]
FIG. 3 is a schematic configuration diagram showing an example of the measuring device 100.
The measuring apparatus 100 uses an actual vibrating body portion 11 including an existing cantilever 1B, a displacement meter 23 that detects the amplitude of the cantilever 1B, and an actuator that vibrates the cantilever 1B, and a detection signal from the displacement meter 23 to generate a virtual signal. An arithmetic processing unit 12 configured by a digital signal processor (DSP) or the like for performing a coupled control process for simulating the motion of the cantilever 1A and controlling the actuator, and an actuator 22 according to a command signal from the arithmetic processing unit 12. A drive circuit 13 for driving the display device and a display device 14 are included.

As shown in the top view of FIG. 4 and the front view of FIG. 5, the actual vibrating body section 11 includes an existing cantilever 1B, a support member 21 that supports one end of the cantilever 1B, and an actuator 22 that vibrates the support member 21. A displacement gauge (vibration displacement detector) 23 including a laser displacement sensor for detecting displacement of the tip of the cantilever 1B. The parts described in FIGS. 4 and 5 correspond to parts for the measuring device.
As shown in FIG. 5, the support member 21 supports one end of the elongated plate-shaped cantilever 1B so that the width direction of the cantilever 1B is vertical to the vertical direction.
The support member 21 also includes a holding portion 21a that holds the cantilever 1B, and a guide portion 21b that slidably supports the holding portion 21a in a direction orthogonal to the longitudinal direction of the cantilever 1B. The holding portion 21a and the guide portion 21b are slidably supported via a linear bearing or the like.

The actuator 22 is configured to include, for example, a uniaxial piezo actuator, includes a shaft portion 22a that expands and contracts, and a support portion 22b that supports one end of the shaft portion 22a. The holding portion 21a is provided at the other end of the shaft portion 22a. Is fixed. The expansion / contraction direction of the shaft portion 22a and the guide direction of the holding portion 21a in the guide portion 21b are arranged so as to coincide with each other, and the actuator 22 expands / contracts the shaft portion 22a in response to a drive signal from the drive circuit 13 to hold the holding portion. 21a moves with the guide portion 21b as a guide, and the cantilever 1B held by the holding portion 21a moves. As a result, the actuator 22 is moved so as to alternately expand and contract the shaft portion 22a, whereby the holding portion 21a vibrates, and as a result, the cantilever 1B vibrates.

The displacement meter 23 is arranged at a position where the distance to the tip of the cantilever 1B can be measured, and measures the distance to the tip of the cantilever 1B. The amplitude of the cantilever 1B can be detected by calculating the displacement of the distance to the tip of the cantilever 1B detected by the displacement meter 23.

[Block diagram showing the dynamics of the measuring device]
FIG. 6 is a block diagram showing an example of the dynamics of the entire measuring device 100.
Here, the equations (1) to (12), which have been described as being dimensionally in terms of calculation in the arithmetic processing unit 12 configured by a DSP or the like, need to be converted into a dimensionless amount. When the equations (6) and (7) are made dimensionless, they can be expressed by the following equations (13) and (14).
(d ² x1 ^* / dt ^{* 2} ) + γ · (dx1 ^* / dt ^* )
+ (1 + kc ^* ) ^* x1 ^* -kc ^** x2 ^*
-Β · (dx2 ^* / dt ^* ) = 0
… (13)

(1 + δ) ・ (d ² x2 ^* / dt ^{* 2} )
+ Γ ・ (dx2 ^* / dt ^* ) + x2 ^*
= Kc ^* · (x1 ^* −x2 ^* ) + β · (dx2 ^* / dt ^* )
… (14)
The symbol “*” in the equation (14) represents a dimensionless quantity, and x1 ^* and x2 ^* correspond to x1 and x2, respectively. Further, t ^* = (k / m) ^1/2 · t, γ = c / (m · k) ^1/2 , kc ^* = kc / k, β = b / (m · k) ^1/2 , δ = Δm / m.

FIG. 6 is a block diagram showing the equations (13) and (14).
As shown in FIG. 6, the displacement x2 of the cantilever 1B is detected by the displacement meter 23, multiplied by the gain G1 of the displacement meter 23 by the calculator 31, and then converted into a digital signal by the AD converter (ADC) 32, and calculated. It is processed by the processing device 12. That is, the output of the AD converter 32 is multiplied by the gain G2 in the calculator 33, and then passed through the LPF (low-pass filter) unit 34 and the differentiator (vibration velocity detecting unit) 35, and the first-order differential value dx2 of the displacement x2. ^It is converted into ^* / dt ^* and input to the multiplier 36, and β · (dx2 ^* / dt ^* ) is output from the multiplier 36. A feedback component for self-sustained pulsation is created by multiplying the first-order differential value dx2 ^* / dt ^* of the displacement x2 ^{* by} the velocity feedback gain β. This feedback component is input to the adder 37.

The output x2 ^* of the computing unit 33 is further input to the computing unit 38 and also to the computing unit 39 directly or via the differentiator 40.
The calculator 39 obtains the displacement x1 ^* of the virtual cantilever 1A using the Runge-Kutta method based on the output x2 ^* of the calculator 33 and the output dx2 ^* / dt ^* of the differentiator 40. The displacement x1 ^* is input to the calculator 39, and the difference between the displacement x1 ^* and the displacement x2 ^* is output from the calculator 39. This difference is multiplied by the displacement feedback gain kc ^* for coupling the virtual cantilever 1A and the existing cantilever 1B by the multiplier 41 to generate a feedback component for simulating the coupling rigidity. This feedback component is input to the adder 37. The output β · (dx2 ^* / dt ^* ) of the multiplier 36 as the velocity feedback component and the output kc · (x1 ^* −x2 ^* ) of the multiplier 41 as the displacement feedback component are added by the adder 37 to generate the vibration. It is output as the input displacement Δx. The vibration input displacement Δx is input to the calculator 42, multiplied by the gain G3, and then output to the actuator 22 via the DA converter (DAC) 43. That is, the output of the DA converter 43 is multiplied by the piezoelectric constant d33 of the actuator 22 (piezoactuator) by the multiplier (feedback control unit) 44 and input to the cantilever 1B as the vibration input displacement Δx. As a result, a feedback loop simulating the coupled effect of the virtual vibrator is constructed.
The gains G2 and G3 are set, for example, based on the representative length and the representative time for converting the dimensionless quantity into the dimensional quantity.

[Characteristics of cantilever 1B used in verification experiment]
Next, the characteristics of the existing cantilever 1B used in the measuring device 100 will be described.
The material of the cantilever 1B is C5191P (phosphor bronze plate). The shape of the cantilever 1B is 210 [mm] in length from the fixed end, 15 [mm] in width, and 0.3 [mm] in thickness. The natural frequency f1 of the cantilever 1B is 3.964 Hz, and the dimensionless damping coefficient γ is 1.770 × 10 ⁻³ .

〔inspection result〕
In the measuring device 100 having the above configuration, by setting the displacement feedback gain kc ^* to an arbitrary value, the coupled rigidity between the virtual cantilever 1A and the existing cantilever 1B can be set to a desired value. I checked if it was. Specifically, the confirmation was performed by utilizing the change situation of the secondary mode natural frequency f2 of the existing cantilever 1B when the displacement feedback gain kc ^* for simulating the virtual coupled stiffness is changed.
FIG. 7A shows the value set as the displacement feedback gain kc ^* and the measured value of the secondary mode natural frequency f2 of the existing cantilever 1B at that time. The secondary mode natural frequency f2 of the cantilever 1B can be obtained from the frequency analysis of free vibration of the cantilever 1B detected from the detection value of the displacement meter 23, for example.

Further, FIG. 7B shows the correspondence between the set value set as the displacement feedback gain kc ^* and the experimental value kce ^* of the coupled stiffness calculated from the secondary mode natural frequency f2. In FIG. 7B, the horizontal axis is the set value set as the displacement feedback gain kc ^* , and the vertical axis is the experimental value kce ^* of the coupled rigidity. The experimental value kce ^* of the coupled rigidity was calculated from the following equation (15). The equation (15) is derived from the equations (13) and (14) with the velocity feedback gain β = 0, and is an experiment of the coupled stiffness when the velocity feedback gain β = 0. The value kce ^* can theoretically be expressed by equation (15). Δ and γ in the equations (13) and (14) are coefficients representing the characteristics of the existing cantilever 1B, and both δ and γ are zero here.
kce ^* = (1/2) × {(f2 / f1) ² −1}
… (15)

As shown in FIG. 7B, the displacement feedback gain kc ^* and the experimental value kce ^* of the coupled rigidity, that is, the natural frequency f1 of the cantilever 1B obtained from the free vibration experiment when the displacement feedback gain kc ^* is given. Also, it was confirmed that the relationship with the experimental value kce ^* of the coupled rigidity obtained from the equation (15) using the eigenfrequency f2 of the secondary mode of the cantilever 1B is almost located on the straight line with the inclination “1”. That is, it was confirmed that by adjusting the displacement feedback gain kc ^* , the virtual cantilever 1A connected to the cantilever 1B can be simulated at the desired experimental value kce ^* of the coupled rigidity.

FIG. 8 shows the measurement device 100 when the displacement feedback gain kc ^* is kc ^* = 0.01 (FIG. 8A) and when kc ^* = 0.005 (FIG. 8B). It shows the relationship between the amplitude ratio and the mass ratio of the

cantilevers

1A and 1B.
8A and 8B, the horizontal axis represents the mass ratio and the vertical axis represents the amplitude ratio (x1 / x2).
From FIGS. 8A and 8B, it can be seen that the amplitude ratio monotonically decreases as the mass ratio increases. That is, it was confirmed that mass measurement can be performed from the amplitude ratio.
Further, it is understood from FIGS. 8A and 8B that the smaller the displacement feedback gain kc ^{*, the} larger the amount of change in the amplitude ratio with respect to the change in mass ratio. In other words, by changing the displacement feedback gain kc ^*, it is possible to adjust the mass of the measuring sensitivity of the measuring object, the more the displacement feedback gain kc ^* is small, it was confirmed that the measurement sensitivity is further improved.

From the above, the measurement applied to the cantilever 1B using the virtual cantilever 1A and the real cantilever 1B coupled by coupling by simulating the equivalent model shown in FIG. 2 by the arithmetic processing unit 12 of the measuring device 100. It is understood that the mass measurement of the object can be performed.
Further, in the measuring device 100, since the displacement feedback proportional to the difference in displacement between the existing cantilever 1B and the virtual cantilever 1A is given to the cantilever 1B, the coupled rigidity can be simulated. Further, by adjusting the displacement feedback gain kc ^* , it is possible to simulate arbitrary coupled rigidity.

Then, by using the Runge-Kutta method, the coupled

cantilevers

1A and 1B can be simulated in real time. Therefore, the mass of the measuring object can be measured from the ratio of the amplitude of the cantilever 1B to which the measuring object is attached and the amplitude of the virtual cantilever 1A.
Further, the sensitivity of measuring the mass of the object to be measured can be adjusted by arbitrarily changing the coupled rigidity. Further, the coupling rigidity can be arbitrarily changed, that is, the coupling rigidity can be made smaller than that in the case where two existing cantilevers are mechanically connected to form a coupling connection. . That is, it is possible to realize the measuring device 100 with higher accuracy.

Further, as described above, since the cantilever 1A and the overhang portion 1D are virtually simulated by the arithmetic processing device 12, in the measuring device that measures the mass of the measuring object using one existing cantilever. It can be realized only by mounting the simulation device 100a including the arithmetic processing unit 12, the drive circuit 13, and the display device 14 shown in FIG. Therefore, the accuracy of the measurement device can be easily improved by adding the simulation device 100a to the existing measurement device.

<Modification>
[1] In the above embodiment, the measuring device 100 may be configured so that the amplitude of self-excited oscillation can be suppressed to a smaller value.
That is, the value expressed by the following equation (16) is used with F as the excitation force.
F = kc · (x1-x2) + b · (dx2 / dt)
+ F (x, (dx / dt)) (16)

Note that f (x, (dx / dt)) in the equation (16) is a nonlinear velocity feedback component, and its phase needs to be antiphase or in-phase with dx2 / dt. For example, if f (x, (dx / dt)) is set as shown in the following equation (17) and bn in the equation (17) is adjusted, the amplitude of the virtual cantilever 1A and the existing cantilever 1B can be reduced. Can be suppressed. As a result, the divergence of vibrations of the

cantilevers

1A and 1B can be suppressed, and the divergence can be suppressed, so that the linear mode can be accurately measured.

In this case, the equations of motion shown in the equations (1) and (2) can be expressed by the following equations (18) and (19).
f (x, (dx / dt)) = bn · (dx2 / dt) ³
… (17)
m ・ (d ² x1 / dt ² ) + c ・ (dx1 / dt)
+ (K + kc) · x1-kc · x2
= B · (dx2 / dt) + bn · (dx2 / dt) ³
… (18)
(m + Δm) ・ (d ² x2 / dt ² ) + c ・ (dx2 / dt)
-Kc x1 + (k + kc) x2
= B · (dx2 / dt) + bn · (dx2 / dt) ³
… (19)

[2] In the above embodiment, the case where the virtual cantilever 1A is assumed to have the same shape and the same characteristics as the existing cantilever 1B has been described, but the present invention is not limited to this. The virtual cantilever 1A and the existing cantilever 1B may have the same natural frequency, and may not have the same shape as long as the natural frequencies are the same. The higher the accuracy of matching the natural frequencies of the

cantilevers

1A and 1B, the higher the accuracy of measurement by the measuring device 100. The term “identical” here includes not only the case where they are exactly the same but also the case where there is a difference (for example, a deviation of 1% to 2%) that can be regarded as substantially the same. When the natural frequency of the cantilever 1B that could be actually measured within the measurable range is used and the natural frequencies of the

cantilevers

1A and 1B are adjusted to be the same, the difference between the natural frequencies of the two is the minimum. Including cases where

[3] In the above embodiment, the arithmetic processing unit 12 may further execute initial processing. For example, the actuator 22 is driven to drive only the existing cantilever 1B, and the frequency at which self-excited oscillation occurs is acquired. Specifically, while observing the vibration state of the cantilever 1B, the feedback gain is changed to obtain the frequency at the time when the vibration starts, that is, the resonance frequency. This is set as a natural frequency, and information based on the acquired natural frequency is set as information necessary for simulating the virtual cantilever 1A. After that, the cantilever 1A is simulated using the set information. This initial processing may be performed at a preset timing, for example, at the start of measurement of a series of measurement objects or periodically. The natural frequency is a theoretical value, and the frequency that actually resonates is the resonance frequency. Unless the effect of viscosity is strong, the resonance frequency is almost equal to the natural frequency.
The initial process may include the process of setting the feedback gain b.

[4] In the above embodiment, the case where the arithmetic processing device 12 performs the arithmetic processing has been described, but the present invention is not limited to this. For example, an analog circuit for performing the above arithmetic processing may be configured and the arithmetic processing may be performed by this analog circuit. That is, as the length of the cantilever 1B becomes shorter, the vibration frequency of the cantilever 1B becomes higher, and higher-speed calculation is required. Therefore, it is necessary to use a higher performance digital signal processor or the like as the processing unit 12. Will increase costs. In this case, by configuring the arithmetic processing unit 12 shown in FIG. 3 with an analog circuit, it can be realized without using a high-performance digital signal processor or the like, that is, an increase in cost can be suppressed. .

When the function of the arithmetic processing unit 12 is realized by an analog circuit, it is preferable to form an analog resonance circuit that outputs an electric signal equivalent to that of the equation (1). For example, by forming a spring-mass model in the LCR circuit, the model can be formed as if the displacement signal of the real cantilever 1B is input to the fixed end of the virtual cantilever 1A, and the model is coupled with the real cantilever 1B. The combined virtual cantilever 1A can be realized with higher accuracy.

[5] In the above embodiment, the case where the uniaxial piezo actuator is used as the actuator 22 has been described, but the present invention is not limited to this.
For example, an actuator that can reciprocate the fixed end of the cantilever 1B, such as a magnet, can be applied.
In the above embodiment, the tip side of the cantilever 1B may be vibrated. For example, any actuator that can vibrate the tip of the cantilever 1B, such as a magnet or a piezo actuator, can be applied.

[6] In the above embodiment, the case where the present invention is applied to the cantilever 1B that measures the mass of the measurement object has been described, but the present invention is not limited to this.
For example, it may be applied to a probe used in an AFM (Atomic Force Microscope) or the like to simulate a virtual model in which a real probe and a virtual probe are coupled and coupled.
The physical quantity to be measured is not limited to mass, and may be any of the surface shape, elastic modulus, viscoelasticity, and force field. The force field here includes an electric field in space, a magnetic field in space, a spatial distribution of gravitational force, and the like.

For example, when measuring the electric field of the measurement target, in the method of measuring using two existing cantilevers, both of the two cantilevers may be affected by the electric field.
In the measuring device 100 according to the present embodiment, since one cantilever 1A is a virtual cantilever, a situation equivalent to a case in which the two cantilevers are separated to a position where one cantilever is not affected by the electric field is assumed to be virtual. Can be realized in real time. Therefore, it is possible to prevent both the two cantilevers from being affected by the electric field, and the measurement accuracy can be improved accordingly.
Further, by measuring the spatial distribution of universal gravitational force, for example, the mass of the moving body can be detected. That is, since the gravitational force changes with the movement of the mass on the ground, the mass of the moving body can be detected by detecting the change in the gravitational force.

[7] In the above embodiment, the case where the laser displacement meter is used as the displacement meter 23 has been described, but the invention is not limited to this. For example, a capacitance displacement sensor, an encoder, an optical displacement gauge (for example, a displacement sensor using the optical lever method), a strain gauge, or the like can be used. Further, the eddy current may be measured, and the displacement of the cantilever 1B may be detected from the displacement amount. In short, any method may be used as long as the displacement of the cantilever 1B can be detected.

[8] In the above embodiment, the case where the cantilever is used as the vibrating body has been described, but the present invention is not limited to this. It is also possible to apply a coil spring as the vibrating body.

[9] In the above embodiment, the case where the cantilever 1A and the overhang portion 1D are virtually simulated by the arithmetic processing unit 12 has been described, but the present invention is not limited to this. For example, the cantilever 1A and the cantilever 1B may be actually provided, and the existing cantilever 1A and the cantilever 1B may be virtually coupled by the arithmetic processing unit 12. In this case, for example, the amplitude of the cantilever 1A and the amplitude of the cantilever 1B are detected, and based on these, the equivalent model in which the cantilever 1A and the cantilever 1B are virtually coupled to each other is used to obtain the cantilever. It suffices to control the actuators that drive 1A and 1B.

[10] In the above embodiment, a plurality of cantilevers for improving sensitivity may be further provided between the

cantilevers

1A and 1B.

FIG. 9 shows a virtual cantilever CL1 corresponding to the virtual cantilever 1A, a real cantilever CLn (n is an integer of n ≧ 3) corresponding to the real cantilever 1B, and existing between the cantilevers CL1 and CLn. FIG. 6 is an explanatory diagram for explaining a method of measuring an atomic force using the vibrating unit 1 having one or a plurality of cantilevers CLi (i is 2 ≦ i ≦ n−1) for improving sensitivity. The atomic force to be measured is applied to the existing cantilever CLn, and this atomic force is measured.
In FIG. 9, the virtual cantilever CL1 and the real cantilever CLn have the same natural frequency. As a method of matching the natural frequencies, the virtual cantilever CL1, the sensitivity improving cantilevers CL2 to CLn-1 and the existing cantilever CLn are made of the same material and shape, and have the same spring rigidity and mass. And a method of making the ratio of spring rigidity and mass match.

The cantilevers CL2 to CLn-1 for improving sensitivity are formed in the same manner as the cantilevers CL1 and CLn. That is, in the state of a cantilever having one end fixed to the support member 1C and the other end being a free end, the cantilevers are juxtaposed side by side, and the root portions of the adjacent cantilevers on the fixed end side are formed on the support member 1C. The virtual cantilever CL1, the cantilevers CL2 to CLn-1 for improving the sensitivity, and the existing cantilever CLn are coupled and vibrated by being connected by the overhang portion 1D.
The virtual cantilevers CL2 to CLn-1 for improving the sensitivity are realized as virtual models on the arithmetic processing device, like the virtual cantilever CL1. If the virtual cantilever CL1 and the real cantilever CLn have the same natural frequency, the natural frequencies of the sensitivity-improving virtual cantilevers CL2 to CLn-1 are the natural frequencies of the virtual cantilever CL1 and the real cantilever CLn. It need not be the same as the frequency.

FIG. 10 is a diagram showing an example of an equivalent model (coupling model) of the dynamic system of the vibrating section 1. In the coupled model shown in FIG. 10, the virtual cantilever CL1 includes a first spring K1 having a spring constant k1 whose one end is supported by the support member 1C and a first mass K1 which is supported at the other end of the first spring K1. The model is provided with the object M1.
Similarly, the existing cantilever CLn includes an n-th spring Kn having a spring constant kn, one end of which is supported by the support member 1C, and an n-th spring Kn, as shown by a cantilever in a frame of a dashed-dotted line at the right end of FIG. An n-th body Mn having a mass mn supported at the other end is provided, and the n-th spring Kn is a model in which the spring constant kn is added with the spring rigidity Δk according to the atomic force of the measurement target. .

The virtual cantilever CLi (2 ≦ i ≦ n−1) for improving sensitivity has an i-th spring Ki having a spring constant ki whose one end is supported by the support member 1C and a mass supported by the other end of the i-th spring Ki. It becomes a model including the i-th object Mi of mi.
Further, in the coupled model shown in FIG. 10, the first object M1 and the second object M2 are connected by the spring Kc1 having the spring constant kc, and similarly, the adjacent objects are connected by the spring having the spring constant kc, and the real objects exist. The nth object Mn corresponding to the cantilever CLn of No. 1 and the (n-1) th object Mn-1 corresponding to the sensitivity improving cantilever CLn-1 are connected by the spring Kcn-1 having the spring constant kc. The springs Kc1 to Kcn-1 having the spring constant kc correspond to the overhang portion 1D in FIG. 9 and generate the coupled effect of the cantilevers CL1 to CLn. In FIG. 10, a portion surrounded by a broken line is simulated as a virtual model.

In a measuring device having such a vibrating portion 1, when performing measurement, of the cantilevers supported by the supporting member 1C, an existing atomic force of the cantilever CLn, for example, an atomic force of the measurement target is applied to the supporting member 1C. A vibration input is given to the cantilever CL1, which is a virtual cantilever that is a cantilever located at the end of the supported cantilevers.
Here, in Non-Patent Document 1 and Non-Patent Document 2, in a measuring device using a resonator (cantilever), if a large number of resonators are weakly coupled, the measuring device becomes highly sensitive as the number of resonators increases. It is described that it is possible.

As described in Non-Patent Document 2, when the rigidity decreases (Δk <0), the amplitude ratio of the secondary mode is measured. On the contrary, when the rigidity increases (Δk> 0), the amplitude ratio of the primary mode is measured. Here, the case where the rigidity decreases in the coupled model shown in FIG. 9 will be described according to Non-Patent Document 1.
From Equation (13) of Non-Patent Document 1, with respect to the dimensionless rigidity change δ = Δk / k1 of the nth cantilever CLn, the amplitude ratio an2 between the first cantilever CL1 and the nth cantilever CLn in the secondary mode ( The change rate S2 of the deviation from the amplitude ratio 1) is given by the following equation (20) (corresponding to equation (13) of Non-Patent Document 1). In the equation (20), αi has αi = mi / m1 (i = 2, ..., N), δ = Δk / k1, κ = kc / k1, and λp has n cantilevers CL1 to CLn. It is an eigenvalue of the p-th order in a measuring device equipped with a vibrating section.

When there are two weakly coupled cantilevers, equation (20) can be expressed by the following equation (21).

Therefore, from the equation (20), it is understood that the change rate, that is, the sensitivity S2 is significantly improved when the following condition is satisfied.
Condition 1 Increase the number of cantilevers n as much as possible. That is, a large number of cantilevers for improving sensitivity are provided.
Condition 2 αn = mn / m1 is made as small as possible.
Condition 3 The masses m2 to mn-1 of the sensitivity improving cantilevers CL2 to CLn-1 are made larger than the mass m1 of the cantilever CL1.
Condition 4 The spring rigidity of each of the cantilevers CL2 to CLn-1, that is, the spring constant k2 to kn-1 is set to be larger than the spring rigidity of each of the cantilevers CL1 or the spring constant of k1.

From the above, as shown in FIGS. 9 and 10, between the virtual cantilever CL1 and the real cantilever CLn, virtual cantilevers CL2 to CLn-1 for sensitivity improvement are provided, and cantilevers CL1 to CLn for coupled vibration are provided. It can be seen that the sensitivity is improved by increasing the number of.

Then, as shown in FIGS. 9 and 10, in the vibrating section 1 according to the present embodiment, the virtual cantilever CL1 and the sensitivity improving cantilevers CL2 to CLn-1 are realized as virtual cantilevers instead of existing cantilevers. is doing. Therefore, even if it is difficult to actually manufacture a plurality of cantilevers, in the measuring apparatus 100 according to the present embodiment, a virtual cantilever CL1 that is another cantilever other than the existing cantilever CLn and a cantilever for sensitivity improvement. Since CL2 to CLn-1 are virtually simulated, by manufacturing only the existing cantilevers CLn, it is possible to easily manufacture a high-sensitivity cantilever coupled with many cantilevers for improving sensitivity. it can. This is the most different point between this embodiment and Non-Patent Documents 1 and 2. That is, in Non-Patent Document 1 and Non-Patent Document 2, since it is assumed that a large number of existing cantilevers are coupled, it is technically difficult to manufacture, whereas in the present embodiment, the existing cantilevers are present. Since only one is required, it is technically easy to manufacture. In the present embodiment, the virtual cantilever CL1 and a large number of cantilevers CL2 to CLn-1 for sensitivity improvement are created "simulated", but in the present invention, existing cantilevers exist, and further, the coupled By combining an arithmetic processing unit capable of executing the above with an existing cantilever, a performance superior to that of the known technology is realized, and therefore, it does not correspond to an abstract concept.

In the vibrating section 1 according to the present embodiment, the sensitivity improving cantilevers CL2 to CLn-1 are realized as virtual cantilevers instead of existing cantilevers. Therefore, it is easy to increase the number of simulated cantilevers for improving sensitivity, and the sensitivity can be further improved as the number of coupled cantilevers increases. In the techniques described in Non-Patent Document 1 and Non-Patent Document 2, the number of cantilevers for improving sensitivity is limited by physical size, strength, cost, etc., and thus cannot be increased indefinitely.
Since the sensitivity can be easily improved in this way, even physical quantities that could not be measured due to low sensitivity can be measured by improving the sensitivity as described above, and the usability is improved. It can be improved and versatility can be improved.

In addition, since the sensitivity can be easily improved in this way, even a light-weight substance or the like that could not be measured until now can be easily measured.
Further, as in the condition 2, the sensitivity is increased by making αn = mn / m1 as small as possible. Here, m1 is the mass of the first object M1 that the virtual cantilever CL1 has, so in the present embodiment, the sensitivity can be improved as the mass m1 is increased virtually, and the sensitivity can be easily improved. be able to. The techniques described in Non-Patent Document 1 and Non-Patent Document 2 have a limit because increasing the mass m1 is limited by physical size, strength, cost, and the like.

In the above embodiment, at least the natural frequencies of the virtual cantilever CL1 and the existing cantilever CLn may match, but preferably, the spring rigidity of the sensitivity improving cantilevers CL2 to CLn-1 is It is preferably higher than the spring rigidity of the cantilevers CL1 and CLn. Further, the sensitivity improving cantilevers CL2 to CLn-1 are not necessarily required to be provided that the sensitivity improving cantilevers CL2 to CLn-1 have a spring rigidity higher than that of the cantilevers CL1 and CLn. CLn-1 do not have to be the same material and shape, and may have different spring stiffness and mass.

It should be noted that the scope of the present invention is not limited to the illustrated and described exemplary embodiments, but includes all embodiments that bring about an effect equivalent to that intended by the present invention. Furthermore, the scope of the present invention may be delineated by any desired combination of specific features of each disclosed feature.

1 Vibration part 1A Cantilever (virtual vibration body)
1B cantilever (actual vibrator)

1C Supporting member

1D Overhang part 11 Actual vibrating body part 12 Arithmetic processing device 13 Driving circuit 14 Display device 21 Supporting member

21a Holding part

21b Guide part 22 Actuator

22a Shaft part

22b Supporting part 23 Displacement meter 100 Measuring device 100a Simulation device CL1 Virtual Cantilevers CL2-CLn-1 Cantilevers CLn for improving sensitivity Real-life cantilevers

Claims

A measuring device for detecting a value corresponding to a physical quantity to be measured by using the amplitudes of two vibrating bodies,
An actual real vibrating body as one of the two vibrating bodies,
An actuator that applies a force in a preset displacement direction to the actual vibrating body,
A vibration displacement detection unit that detects the vibration displacement of the actual vibrating body,
The virtual vibrating body that is virtually coupled to the real vibrating body is simulated as another one of the two vibrating bodies, and the virtual vibrating body and the vibration displacement detection unit detect the virtual vibrating body. An arithmetic processing unit that executes a coupled control process for driving and controlling the actuator based on the vibration displacement of the actual vibrating body,
A measuring device comprising:
The measuring device according to claim 1, wherein the virtual vibrating body is represented by numerical information that simulates a physical model of a vibrating body coupled to the real vibrating body by a theoretical mathematical formula.
3. The measurement according to claim 1, wherein the arithmetic processing device simulates the virtual vibration body so that the natural frequency of the virtual vibration body matches the natural frequency of the actual vibration body. apparatus.
The arithmetic processing unit,
A vibration speed detection unit that detects the vibration speed of the actual vibrating body,
A feedback control unit for driving the actuator by a feedback control signal,
Equipped with
The feedback control signal is
A linear displacement feedback component based on the difference between the vibration displacement of the actual vibration body detected by the vibration displacement detection unit and the vibration displacement of the virtual vibration body simulated by the arithmetic processing device, and the vibration velocity detection unit detected. The linear velocity feedback component based on the said vibration velocity is included, The measuring device as described in any one of Claim 1 to 3 characterized by the above-mentioned.
The measuring device according to claim 4, wherein the feedback control signal includes a non-linear velocity feedback component in-phase or anti-phase with respect to the vibration velocity in order to suppress the amplitude of the actual vibration body.
The arithmetic processing device drives and controls the actuator, vibrates the actual vibrating body to acquire a resonance frequency at a resonance point, and sets information necessary for simulating the virtual vibrating body based on the acquired resonance frequency. The measuring device according to any one of claims 1 to 5, which is adapted to perform an initial process.
The measuring device according to any one of claims 1 to 6, wherein the physical quantity is at least one of mass, surface shape, elastic modulus, viscoelasticity, and force field. .
The arithmetic processing device, in addition to the virtual vibrating body, simulates another virtual vibrating body for sensitivity improvement that is virtually coupled between the virtual vibrating body and the actual vibrating body, 8. The coupled control process for driving and controlling the actuator based on the virtual vibration body, another virtual vibration body for improving the sensitivity, and the vibration displacement, according to claim 1 to claim 7. The measuring device according to any one of claims.
A component for a measuring device according to any one of claims 1 to 8,
With a real vibration body,
An actuator that applies a force in a preset displacement direction to the actual vibrating body,
A vibration displacement detection unit that detects the vibration displacement of the actual vibrating body,
A component for a measuring device, characterized by comprising:
An arithmetic processing device for a measuring device according to any one of claims 1 to 7,
A measuring device characterized by using a vibration displacement of the actual vibrating body to simulate a virtual vibrating body that is virtually coupled to the actual vibrating body and to generate a signal for driving and controlling the actuator. Processor for computer.