Systems, methods, apparatus, and programs

Abstract

This non-contact, simple configuration allows for highly accurate estimation of the viscosity of the object being measured. [Solution] A system comprising: a mixing means for mixing a first object and a second object having different specific gravities; a sound wave transmitting means for transmitting sound waves to the first object, the second object, or a mixture thereof; a sound wave receiving means for receiving sound waves transmitted from the sound wave transmitting means; and an estimation means for estimating the viscosity of the first object based on changes in the received signal received by the sound wave receiving means.

Description

Technical Field

[0001] The present disclosure relates to a system, a method, an apparatus, and a program.

Background Art

[0002] In Patent Document 1, a technique using an acoustic wave device (AWD) sensor to simultaneously determine physical properties (density, viscosity, elasticity, etc.) of a fluid is described.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [[ID=3 >5]]Conventional viscosity sensors as described in Patent Document 1 need to bring the sensor element into contact with the fluid, resulting in maintenance trouble due to dirt.

[0005] <000002 >An object of the present disclosure is to estimate the viscosity of a measurement object with high accuracy by a non-contact and simple configuration.

Means for Solving the Problems

[0006] A system including a mixing means for mixing a first object and a second object having different specific gravities, a sound wave transmitting means for transmitting a sound wave to the first object, the second object, or a mixture thereof, a sound wave receiving means for receiving the sound wave transmitted from the sound wave transmitting means, and an estimating means for estimating the viscosity of the first object based on a change in a received signal received by the sound wave receiving means.

Effects of the Invention

[0007] According to the present disclosure, the viscosity of a measurement object can be estimated with high accuracy by a non-contact and simple configuration.

Brief Description of the Drawings

[0008] [Figure 1] This is a schematic diagram showing an example of the overall configuration of the viscosity estimation system 1 according to this embodiment. [Figure 2] Figure 1 is a block diagram showing an example of the functional configuration of the viscosity estimation device 100. [Figure 3] Figure 2 is a block diagram showing an example of the functional configuration of the control unit. [Figure 4] This figure shows an example of a calibration curve data table under specified temperature conditions. [Figure 5] This figure shows an example of a measurement conditions table. [Figure 6] This flowchart shows an example of the procedure for viscosity estimation according to this embodiment. [Figure 7] This is a flowchart of a subroutine that shows the procedure for detailed signal analysis (calculation of settling time) in the viscosity estimation process. [Figure 8] This is a schematic diagram showing the time-series changes in the state of bubbles in the tank (T0~T3) after bubble generation has stopped. [Figure 9] This is a conceptual diagram showing the transmitted and received signals in the absence of air bubbles. [Figure 10] This is a conceptual diagram illustrating the mechanism of signal cancellation due to phase shift of sound waves caused by bubbles. [Figure 11] This is a schematic diagram showing the relationship between the vibration mode of the tank (third mode) and the opposing arrangement (180-degree arrangement) of the speaker and microphone. [Figure 12] This is a schematic diagram showing the relationship between the tank's vibration mode (secondary mode) and the 90-degree arrangement of the speaker and microphone. [Figure 13] This waveform diagram illustrates the amplitude change of the received signal after bubble generation stops, and the timing for detecting the settling time. [Figure 14] This graph shows the differences in signal recovery behavior when the viscosity of the liquids differs. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with reference to the drawings. In all the drawings illustrating the embodiments, common components are denoted by the same reference numerals, and repeated explanations are omitted. The following embodiments are not intended to unduly limit the content of this disclosure as described in the claims. Not all components shown in the embodiments are necessarily essential components of this disclosure. Also, each drawing is a schematic diagram and is not necessarily a strict illustration.

[0010] Furthermore, in the following description, "processor" refers to one or more processors. A processor may be expressed, for example, as processing circuitry. At least one processor is typically a microprocessor such as a CPU (Central Processing Unit), but may be other types of processors such as a GPU (Graphics Processing Unit). At least one processor may be single-core or multi-core. Also, at least one processor may be a general-purpose processor or a purpose-specific processor.

[0011] Furthermore, at least one processor may be a broad-sense processor, such as a hardware circuit that performs some or all of the processing (e.g., an FPGA (Field-Programmable Gate Array), an ASIC (Application Specific Integrated Circuit)).

[0012] Furthermore, in the following explanation, we may use expressions such as "xxx table" to describe information that yields an output for a given input. This information can be data with any structure, or it can be a learning model such as a neural network that generates an output for a given input. Therefore, "xxx table" can be referred to as "xxx information."

[0013] In the following description, the configuration of each table is an example. One table may be divided into two or more tables, or all or part of two or more tables may be combined into one table.

[0014] The program may be pre-installed in the information processing device described below. Alternatively, for example, the program may be stored in a record medium (e.g., non-transitory) readable by the information processing device, and this program may be installed in the information processing device. Further, the program may be transmitted from a program distribution server to the information processing device and installed. In the following description, two or more programs may be realized as one program, or one program may be realized as two or more programs.

[0015] In the following description, identification information for various objects is used. The identification information may be any information indicating a predetermined object, and the specific data is not limited to the embodiments. The identification information may be an identification number or an identifier including letters or symbols.

[0016] <Overview> The system according to this embodiment estimates the viscosity of a liquid with high accuracy only by acoustic measurement from the outside without contacting the liquid in the container. The system intentionally generates "bubbles" in the liquid contained in the container. After the generation of the bubbles stops, sound waves are transmitted from a speaker on the outer wall of the container and received by a microphone during the process of the bubbles disappearing. The system estimates the viscosity of the liquid based on the time until the received signal returns to a stable state (state without bubbles).

[0017] <Overall Configuration of the System> Figure 1 is a schematic diagram showing an example of the overall configuration of the viscosity estimation system 1 according to this embodiment. The viscosity estimation system 1 according to this embodiment is installed outside a container, such as a tank or pipe, containing at least a first object to be measured, and has the function of non-contact estimation of the viscosity of the liquid. The viscosity estimation system 1 shown in Figure 1 is configured as, for example, a standalone system and is attached to a tank 200 containing the first object. The viscosity estimation system 1 includes, for example, a viscosity estimation device 100, a speaker 106, a microphone 107, and a mixing device 108. The speaker 106 transmits sound waves based on the control of the viscosity estimation device 100. The microphone 107 receives sound waves. The mixing device 108 mixes the substance contained in the tank 200 based on the control of the viscosity estimation device 100.

[0018] The viscosity estimation device 100 controls the mixing device 108 to mix a first substance and a second substance, for example, having different specific gravities, which are contained in the tank 200. In this embodiment, "mixing" broadly includes the process of dispersing the second substance in the first substance. For example, it is not limited to cases where the second substance (gas) is injected from the outside into the first substance (liquid) (e.g., aeration). For example, when the second substance (steam bubbles, cavitation bubbles, gas bubbles) is generated inside the first substance by ultrasonic vibration, heating, electrolysis, or reduced pressure, this is also included in the mixing of the first and second substances (bubble generation). In this case, the mixing device 108 functions as a bubble generation means. When the first substance is a liquid and the second substance is a gas, the second substance dispersed in the first substance becomes bubbles. Also, when the first substance is a liquid and the second substance is a liquid, the second substance dispersed in the first substance becomes droplets (mist, emulsion, etc.). Furthermore, if the first substance is a liquid and the second substance is a solid, the second substance dispersed in the first substance becomes fine particles (dust, etc.). Also, if the first substance is a gas and the second substance is a liquid, the second substance dispersed in the first substance becomes droplets. Furthermore, if the first substance is a gas and the second substance is a solid, the second substance dispersed in the first substance becomes fine particles. In this embodiment, the state in which the first substance and the second substance are mixed is referred to as a mixture, for example.

[0019] The viscosity estimation device 100 stops mixing after a predetermined time has elapsed and controls the speaker 106 to transmit sound waves. The viscosity estimation device 100 receives, via the microphone 107, the sound waves output from the speaker 106 that propagate through the first target, the second target, or a mixture thereof in the tank 200, and the sound waves that propagate through the tank 200. The viscosity estimation device 100 estimates the viscosity of the first target based on the received sound waves. The following explanation will use the case where the first target is a liquid and the second target is a gas as an example.

[0020] <Configuration of the viscosity estimation device> Figure 2 is a block diagram showing an example of the functional configuration of the viscosity estimation device 100 shown in Figure 1. As shown in Figure 2, the viscosity estimation device 100 comprises a control unit 101, a storage unit 102, a communication unit 103, an input unit 104, an output unit 105, a speaker 106, a microphone 107, and a mixing device 108. These components are electrically connected to each other, for example, via an internal bus.

[0021] The control unit 101 comprehensively controls the operation of the entire device, for example. The control unit 101 is composed of one or more processors, such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit). The processor is composed of, for example, an arithmetic unit, registers, peripheral circuits, etc. The processor implements various functions described later by executing the application program 1021 stored in the memory unit 102. The control unit 101 may also be a dedicated hardware circuit such as an FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit) designed to perform a specific process.

[0022] The memory unit 102 is a volatile or non-volatile storage medium such as ROM (Read Only Memory), RAM (Random Access Memory), flash memory, or a hard disk drive. The memory unit 102 has an area for storing the operating system executed by the control unit 101, the application program 1021, and various data tables used in the viscosity estimation process. The memory unit 102 holds information used in the viscosity estimation process, such as the calibration curve data table 1022 and the measurement condition table 1023.

[0023] The input unit 104 is an interface for the user to give instructions to the viscosity estimation device 100. The input unit 104 is composed of, for example, a physical push button, switch, keyboard, or touch panel display. The output unit 105 is an interface for notifying the user of the viscosity estimation results or the operating status of the device. The output unit 105 is composed of, for example, a liquid crystal display that displays the estimated viscosity value, an LED lamp that indicates the status of the device by color or flashing, or a buzzer or speaker that emits a warning sound.

[0024] Speaker 106 corresponds to a sound wave transmitting means for transmitting sound waves. Speaker 106 is positioned in contact with or close to the outer wall of the container so as to be acoustically coupled. Based on a drive signal from the control unit 101, speaker 106 generates sound waves (e.g., continuous waves) having a specific frequency and amplitude and transmits them through the container wall toward the liquid inside. The sound waves may also be referred to as the transmitted signal. As speaker 106, a general-purpose dynamic speaker, piezoelectric speaker, or contact-type vibration speaker (exciter) can be used.

[0025] Microphone 107 corresponds to a sound wave receiving means for receiving sound waves. Like speaker 106, microphone 107 is positioned in contact with or close to the outer wall of the container. Microphone 107 detects sound waves that have passed through the liquid or mixture inside the container or propagated along the container wall, converts them into electrical signals, and outputs them to control unit 101. The received sound waves may also be called received signals. As microphone 107, a highly sensitive condenser microphone, a piezoelectric element (pickup) for directly detecting vibrations, or an acceleration sensor can be used.

[0026] The relative positions of the speaker 106 and microphone 107 are determined, for example, according to the shape of the container (tank 200) or the vibration mode to be used. When the cross-sectional shape of the tank 200 is circular, it is known that a significant signal change can be obtained in certain arrangements. For example, when the third mode is used as the vibration mode of the tank 200, the microphone 107 is positioned opposite the speaker 106 across the center of the container (180-degree positional relationship). With this arrangement, the control unit 101 can most clearly detect the phase shift due to bubbles as a signal cancellation effect. Also, when the second mode vibration is used in a tank 200 with a circular cross-section, it is effective to position the microphone 107 at a 90-degree positional relationship with the speaker 106. Note that when the cross-sectional shape of the tank 200 is other than circular (for example, square, elliptical, or irregular shape), the specific vibration mode that is excited and the positions of its antinodes and nodes will differ from those in the case of a circular shape. Therefore, depending on the shape of the container, the optimal arrangement that maximizes the signal change (phase difference, amplitude change) due to the presence or absence of air bubbles is appropriately selected. Furthermore, the system according to this embodiment may be equipped with multiple speakers 106. Also, the system according to this embodiment may be equipped with multiple microphones 107. Also, the system according to this embodiment may be equipped with multiple speakers 106 and multiple microphones 107. By using multiple transmitting and receiving means, multifaceted measurements using information from different propagation paths become possible. Also, by using multiple transmitting and receiving means, selective excitation and detection of specific vibration modes becomes possible.

[0027] The mixing device 108 corresponds to a mixing means for generating bubbles in the liquid to be measured. The mixing device 108 can take various forms, such as an aeration device that blows air from the bottom of the tank 200 using a compressor or blower, a motor-driven agitator (mixer) that physically agitates the liquid in the tank 200, or an ultrasonic transducer that generates cavitation in the liquid by applying ultrasonic vibrations from outside the tank 200. It is also possible to repurpose an aeration device already installed in a water treatment facility, etc., as the mixing device 108 of this system.

[0028] Figure 3 is a block diagram showing an example of the functional configuration of the control unit shown in Figure 2. Functionally, the control unit 101 comprises an operation reception unit 1011, a transmission / reception unit 1012, a presentation control unit 1013, a measurement control unit 1014, and an estimation control unit 1015.

[0029] The operation reception unit 1011 has an interface function for receiving operation input from the user to instruct the start of measurement via the input unit 104. The operation reception unit 1011 also has an interface function for receiving operation input to instruct the stop of operation via the input unit 104. Furthermore, the operation reception unit 1011 has an interface function for receiving operation input for selecting measurement conditions via the input unit 104. Furthermore, the operation reception unit 1011 has an interface function for receiving operation input for changing various settings via the input unit 104. The operation reception unit 1011 may have a combination of the above functions.

[0030] The transmitting / receiving unit 1012 has a communication interface function for communicating with external devices via wired or wireless connection.

[0031] The display control unit 1013 has the function of controlling the output unit 105 and presenting the estimated viscosity value to the user visually or audibly. The display control unit 1013 also has the function of controlling the output unit 105 and presenting the waveform graph of the received signal being measured to the user visually or audibly. Furthermore, the display control unit 1013 has the function of controlling the output unit 105 and presenting the current operating mode of the device to the user visually or audibly. Finally, the display control unit 1013 has the function of controlling the output unit 105 and presenting error messages to the user visually or audibly. The display control unit 1013 may have a combination of the above functions.

[0032] The measurement control unit 1014 has a series of control functions for measuring physical quantities that are the basis for viscosity estimation. Specifically, the measurement control unit 1014 has the function of controlling the drive timing and drive time of the mixing device 108. In addition, the measurement control unit 1014 has the function of controlling the frequency, amplitude, and transmission pattern of the sound waves transmitted from the speaker 106.

[0033] Specifically, for example, the measurement control unit 1014 controls the frequency of the sound wave transmitted from the speaker 106 to change in a sweep or step manner within a preset sweep range. The measurement control unit 1014 sequentially acquires the amplitude value of the received signal at each frequency and identifies the frequency at which the amplitude value is maximum (peak) as the optimal resonant frequency in the measurement environment. This enables highly sensitive bubble detection regardless of physical conditions such as liquid pressure, temperature, density, or changes in surface tension due to surfactants or other components, as well as the composition of the object being measured.

[0034] Furthermore, the measurement control unit 1014 has the function of acquiring time-series data of the signal received by the microphone 107 and measuring an index related to the temporal change in the process in which the amplitude or phase of the received signal recovers to a predetermined stable state after the bubble generation stops. The "index related to temporal change" is, for example, the settling time, which is the time it takes for the signal to recover to a stable state. The "index related to temporal change" may also be, for example, the time it takes for the signal level to reach a predetermined amount of change after the bubble generation stops, the time rate of change (slope) of the signal level, the time constant when approximating the signal recovery curve, or the instantaneous value of the amplitude value or phase difference of the signal at a predetermined time after the bubble generation stops. The higher the viscosity of the liquid, the slower the bubble disappears, so the signal recovery speed (slope) becomes gentler, and the signal level after a predetermined time becomes lower. Therefore, these parameters can also be used as surrogate indicators of viscosity. The measurement control unit 1014 may have a combination of the above functions.

[0035] The measurement control unit 1014 intentionally generates bubbles in the tank 200 containing the liquid to be measured using the mixing device 108, and then stops the generation of bubbles. Subsequently, the measurement control unit 1014 non-contactively monitors the process by which the bubbles remaining in the liquid disappear over time according to the viscosity of the liquid, using acoustic signals. Specifically, the measurement control unit 1014 captures the changes in the signal characteristics of the sound waves transmitted from the speaker 106 as they propagate through the liquid containing the bubbles and the tank 200 and reach the microphone 107.

[0036] The estimation control unit 1015 has a function (estimation means) for estimating the viscosity of a liquid based on the settling time measured by the measurement control unit 1014. This estimation function is realized, for example, by referring to the correlation between settling time and viscosity stored in the calibration curve data table 1022, which will be described later. The estimation control unit 1015 also has a function for monitoring the amplitude difference between the transmitted signal and the received signal and detecting the occurrence and disappearance of phase shifts caused by the presence of bubbles. Furthermore, the estimation control unit 1015 may also function as a second estimation means for estimating the presence or absence of solid matter in the liquid based on the characteristics of the signal received by the microphone 107 in a specific arrangement (e.g., 90-degree arrangement).

[0037] The presence of bubbles affects the propagation of sound waves by causing attenuation and phase shift. For example, if many bubbles are present in a dense liquid, the received signal received by microphone 107 through the liquid becomes unstable. The higher the viscosity of the liquid, the slower the bubbles move through it, and the longer the time (setup time) it takes for the lighter bubbles to rise and separate from the liquid. When the bubbles disappear from the liquid, the received signal received by microphone 107 through the liquid becomes stable. The estimation control unit 1015 estimates the viscosity of the liquid by referring to the correlation between the viscosity and the regular changes in strength or distance of the received signal caused by the movement of bubbles. The estimation control unit 1015 also estimates the viscosity of the liquid by referring to the correlation between the viscosity and the setup time (the time it takes for the received signal to stabilize as the bubbles rise and separate from the liquid). Information showing correlations is stored, for example, in the calibration curve data table 1022, and the estimation control unit 1015 estimates the viscosity of the liquid by comparing the measurement results with the correlations stored in the calibration curve data table 1022.

[0038] <Data structure> Figure 4 shows an example of a calibration curve data table under a predetermined temperature. The calibration curve data table 1022 stores reference information for converting viscosity values ​​from measured settling times, for example. The calibration curve data table 1022 consists of columns for "Settling Time (seconds)" and "Viscosity (Pa·s)", and has a data structure that defines the correspondence between the two. For example, information that a settling time of "3.0 seconds" corresponds to a viscosity of "0.100 Pa·s" is experimentally determined and recorded in advance. Furthermore, these values ​​stored in the calibration curve data table 1022 are not limited to experimental values, but may also be calculated by calculations based on mathematical formulas such as Wood's formula ((1)), Minnaert's formula ((2)), and Clay and Medwin's formula ((3)), which will be described later. Note that the information stored in this calibration curve data table 1022 was acquired under predetermined temperature conditions (e.g., 25°C). Since the viscosity of a liquid changes depending on the temperature, if the temperature conditions during measurement differ from the predetermined temperature conditions, information corresponding to those temperature conditions (for example, other calibration curve data acquired at a different temperature) is referenced. Alternatively, the derived viscosity value may be corrected using a predetermined correction coefficient corresponding to the temperature difference. The estimation control unit 1015 derives the corresponding viscosity value by comparing the measured set values ​​with this table. Note that this correlation information is not limited to a table format and may be stored as an approximation formula. Furthermore, the correlation information may be stored in the form of a trained model such as a neural network. In addition, the viscosity may be corrected according to the frictional resistance of the gas and liquid during mixing.

[0039] Figure 5 shows an example of a measurement conditions table. The measurement conditions table 1023 stores information for defining optimal measurement parameters according to, for example, the type of liquid to be measured and the measurement environment. The measurement conditions table 1023 stores various parameters such as "recommended transmission frequency" and "judgment threshold" associated with, for example, "liquid type" as the key. The estimation control unit 1015 reads appropriate measurement parameters from the measurement conditions table 1023 according to the type of liquid selected by the user or the type of liquid automatically determined by a separately provided sensor, and reflects them in the measurement control.

[0040] The "Liquid Type" category includes, for example, "Water-based liquid," "Low-viscosity oil," and "High-molecular-weight solution." The "Recommended Transmission Frequency" is a frequency for obtaining an efficient acoustic response to bubbles contained in a specific object (liquid). In this embodiment, the frequency is not fixed to a specific frequency, but rather a predetermined frequency range is swept (continuously swept) or applied in steps to select the frequency at which the measured amplitude is maximized. This selection process appropriately determines the optimal frequency near the Minert frequency, which is the resonant frequency of the bubbles, depending on the physical conditions of the liquid, such as the pressure, temperature, density, or presence or absence of surfactants that change the surface tension, and the combination of the mixing of the first and second objects. The "Decision Threshold" is a reference value for determining that the received signal has recovered to a stable state. For example, it is defined as the ratio of the received signal to the steady-state value in the absence of bubbles (e.g., 0.98).

[0041] Here, we will explain the theoretical background of viscosity estimation according to this embodiment. This system utilizes the change in acoustic properties that accompanies the mixing of gas bubbles into a liquid. Specifically, as shown by Wood's equation ((1)), the speed of sound in a medium decreases as the volume occupied by gas (gas bubbles) in a mixture increases.

number

[0042] Furthermore, the "recommended transmission frequency" in the measurement conditions table 1023 is preferably derived from the measured amplitude peak frequency based on theories such as Minnaert's equation ((2)). Bubbles resonate at frequencies that depend on their size and the system conditions (pressure, density, etc.) (Minnaert resonance).

number

[0043] Furthermore, in estimating viscosity, the damping characteristics shown by the Clay-Medwin equation (equation (3)), etc., are taken into consideration. Acoustic damping tends to be proportional to the bubble diameter, while viscosity acts to suppress this damping.

number

[0044] <Operation> The operation of the viscosity estimation device 100 in this embodiment will be described below with reference to the flowcharts in Figures 6 and 7, and Figures 8 to 14.

[0045] Figure 6 is a flowchart showing an example of the procedure for viscosity estimation processing according to this embodiment. Viscosity estimation processing according to this embodiment is started, for example, when a user performs a measurement start operation via the input unit 104. Prior to the start of processing, for example, the user selects the type of liquid. Based on the selection of the liquid type, the measurement control unit 1014 reads the recommended frequency, judgment threshold, etc. from the measurement condition table 1023. Also, a predetermined amount of the liquid to be measured is filled in the tank 200, and the speaker 106, microphone 107, and mixing device 108 are installed in predetermined positions in the tank 200. Note that viscosity estimation processing is not limited to being started based on a start operation from the user. Viscosity estimation processing may also be started by instructions from the control unit 101, or by autonomous instructions from a predetermined trained model or generating AI.

[0046] S11: Bubble generation treatment When processing begins, the measurement control unit 1014 turns on the mixing device 108 (S11). Specifically, the measurement control unit 1014 outputs an operation signal to the mixing device 108, which generates bubbles in the liquid to be measured in the tank 200. This process is continued for a predetermined time to ensure that a sufficient amount of bubbles are dispersed throughout the liquid.

[0047] S12: Bubble generation cessation process Once a predetermined time has elapsed, the measurement control unit 1014 stops the bubble generator 108 (S12). The estimation control unit 1015 sets the moment when bubble generation stops as the temporal reference point (T=0) for viscosity estimation and starts timing using the internal timer.

[0048] S13: Start processing for measuring sound wave transmission and reception signals. After bubble generation stops, the measurement control unit 1014 starts measuring the sound wave transmission (transmitted signal) from the speaker 106 and the received signal from the microphone 107 (S13). The speaker 106 transmits a sound wave (continuous wave) with a frequency corresponding to the expected bubble size, preferably near the Minart frequency, which is the resonant frequency of the bubble. In parallel with this, the measurement control unit 1014 continuously acquires the signal received by the microphone 107 as digital data.

[0049] Referring to Figures 8 to 12, the changes in the state inside tank 200 after bubble generation stops, and the principle of signal propagation will be explained. As shown in Figure 8, at time T0 immediately after the stoppage, there are many bubbles in the liquid, and the liquid is cloudy. As time passes (times T1 and T2), the larger bubbles rise to the liquid surface and disappear due to buoyancy, leaving only fine bubbles in the liquid. At time T3, after further time has passed, the bubbles disappear, and the liquid becomes a clear, stable state (steady state).

[0050] In this embodiment, the change in acoustic characteristics due to the presence or absence of bubbles is detected using the phase difference of the signals. As shown in Figure 11, when the third mode is used as the vibration mode for a tank with a circular cross-section, the speaker 106 and microphone 107 are placed opposite each other (180 degrees apart). In this state, the sound waves propagating through the tank 200 experience a phase shift (phase delay) of approximately 180 degrees due to the influence of the third mode. As shown in Figure 9, in a stable state without bubbles, the sound waves transmitted from speaker 106 reach microphone 107. At this time, when the estimation control unit 1015 calculates the difference in amplitude between the transmitted signal and the received signal, the amplitude of the difference signal is maximized because the phase difference between the two is approximately 180 degrees (opposite phase). Furthermore, if a microphone is placed adjacent to speaker 106, and the difference between the amplitude of the received signal received by the microphone and the amplitude of the received signal received by microphone 107 is calculated, the amplitude of the difference signal is maximized.

[0051] On the other hand, as shown in Figure 10, when many bubbles are present in a liquid, acoustic phase shifts occur due to changes in the bubbles, viscosity, solid matter, and density of the medium. Specifically, near the Minart frequency, the generation of bubbles causes a phase delay of approximately 180 degrees between the transmitted and received signals. As a result, the phase delay of the received signal relative to the transmitted signal is the sum of the 180-degree delay due to the vibration mode and the 180-degree delay due to the generation of bubbles, resulting in a total phase shift of 360 degrees (i.e., in phase with 0 degrees). Consequently, the transmitted and received signals become in phase, and when the difference between them is calculated, the signals cancel each other out. Therefore, the amplitude of the calculated difference signal becomes significantly smaller (approaching zero) while bubbles are present. The measurement control unit 1014 monitors the process by which the signal amplitude recovers from this signal cancellation state as the bubbles disappear.

[0052] S14: Settling time calculation process Next, the estimation control unit 1015 analyzes the time-series data of the received signal and calculates the "settlement time (t_settle)," which is the time it takes for the signal to recover to a stable state (S14). This detailed procedure will be explained with reference to the subroutine in Figure 7 and the waveform diagram in Figure 13.

[0053] Figure 7 is a flowchart of a subroutine showing the procedure for detailed signal analysis (calculation of settling time) in the viscosity estimation process. S21: Amplitude value acquisition process When the subroutine starts, the estimation control unit 1015 acquires the difference in amplitude between the transmitted signal and the received signal based on the measurement data (S21). In the initial state with many bubbles, the amplitude value is small due to cancellation by in-phase signals, and in the stable state where the bubbles have disappeared, the amplitude value becomes large due to addition by out-of-phase signals.

[0054] S22: Stability determination process Next, the estimation control unit 1015 determines whether the current amplitude value of the difference signal has come close enough to the reference value indicating a stable state (the maximum amplitude value in a bubble-free state). Specifically, it calculates the difference (deviation) between the stable reference value and the current value and checks whether that value is below a predetermined threshold (S22). If the amplitude value is still in the process of recovery and far from the stable reference value (greater than the threshold) (S22: No), the process returns to step S21 and monitoring continues.

[0055] S23: Duration determination process If the difference from the stable reference value falls below the threshold (S22: Yes), the estimation control unit 1015 determines whether that state has continued for a predetermined time (S23). This is to prevent false determination due to temporary noise. If it has not continued (S23: No), the estimation control unit 1015 returns to step S21.

[0056] S24: Settling time determination process If the estimation control unit 1015 determines that the state below the threshold has continued for a predetermined time (S23: Yes), it determines the time at which the stability determination was made, or the first time the stable state was entered, as the "settlement time (t_settle)" for the measurement (S24). After making the determination, the estimation control unit 1015 terminates the subroutine and returns to the main flow in Figure 6.

[0057] Figure 13 is a waveform diagram showing the time evolution of the signal (amplitude of the difference signal) in the above process. Immediately after bubble generation stops (T=0), the signal amplitude is at a low level due to the aforementioned signal cancellation effect (360-degree phase shift). As time passes and the bubbles disappear, the signal cancellation effect weakens, and the signal amplitude gradually increases. The point at which the amplitude converges to the "stable state level (no bubbles)" and the deviation falls within the range of the "stability judgment threshold" is detected as the settling time (t_settle).

[0058] (Continuation of the main flow in Figure 6) S15: Viscosity estimation process Once the settling time is calculated, the estimation control unit 1015 estimates the viscosity of the liquid based on the calculated settling time and the calibration curve data table 1022 in the storage unit 102 (S15). Figure 14 is a graph showing the differences in signal recovery behavior when the liquid viscosity is different. In the case of a low-viscosity liquid (A), the rate at which bubbles rise is fast, so the received signal amplitude recovers in a short time, and the settling time (t_settle_A) is short. In the case of a medium-viscosity liquid (B), the recovery is gradual, and the settling time (t_settle_B) is moderate. In the case of a high-viscosity liquid (C), the residence time of bubbles is long, so the signal recovery is slow, and the settling time (t_settle_C) is long. The estimation control unit 1015 uses this correlation to calculate the viscosity.

[0059] S16: Output and display processing Finally, the presentation control unit 1013 presents the viscosity value estimated in step S15 to the user (S16). Specifically, for example, the presentation control unit 1013 outputs the estimated viscosity value to the output unit 105. This allows the user to visually or as data to confirm the viscosity of the liquid being measured. This completes the series of viscosity estimation processes.

[0060] <Summary> As described above, in the system according to the above embodiment, the mixing means 108 mixes a first object and a second object having different specific gravities, and then stops mixing. The sound wave transmitting means 106 transmits sound waves. The sound wave receiving means 107 receives sound waves that have passed through the first object, the second object, or a mixture thereof, as well as sound waves that have been transmitted through the containers of the first object and the second object. After mixing stops, the estimation means 1015 measures the time until the phase difference between the transmitted sound waves and the received sound waves recovers to a stable state, and estimates the viscosity of the first object based on this time. This makes it possible to quantitatively evaluate the viscosity of a substance by utilizing the temporal change in acoustic characteristics (phase difference) associated with the change in the state of the mixture, without contacting the substance inside the container.

[0061] Therefore, according to this embodiment, the viscosity of the object to be measured can be estimated with high accuracy using a non-contact and simple configuration.

[0062] Furthermore, in the above embodiment, the sound wave receiving means 107 is positioned opposite the sound wave transmitting means 106, or at a predetermined angle. This makes it possible to construct a positional relationship that allows for the appropriate detection of sound wave propagation characteristics depending on the shape of the container, the vibration mode, or a combination thereof.

[0063] Furthermore, in the above embodiment, the viscosity estimation system 1 has multiple sound wave transmission means 106. This makes it possible to perform multifaceted measurements using multiple propagation paths or different frequencies, thereby improving measurement accuracy and expanding the range of application.

[0064] Furthermore, in the above embodiment, the estimation means 1015 detects the occurrence and disappearance of phase shifts caused by bubbles by monitoring the difference in amplitude between the sound waves transmitted by the sound wave transmitting means 106 and the sound waves received by the sound wave receiving means 107. This makes it possible to clearly capture the cancellation of signals due to phase shifts when bubbles are present and the recovery of signals due to the disappearance of bubbles as amplitude changes, and to accurately measure the settling time.

[0065] Furthermore, in the above embodiment, the sound wave receiving means 107 is positioned such that, in a specific vibration mode of the container, the difference in amplitude between the sound wave transmitted by the sound wave transmitting means 106 and the sound wave received by the sound wave receiving means 107 is maximized. This maximizes the signal-to-noise ratio of the signal in a stable state without bubbles and enables sensitive detection of signal changes when bubbles are generated.

[0066] Furthermore, in the above embodiment, when the vibration mode is a third-order mode, the sound wave receiving means 107 is positioned opposite the sound wave transmitting means 106. This makes it possible to perform highly accurate measurements by utilizing the phase relationship unique to the third-order mode.

[0067] Furthermore, in the above embodiment, when the vibration mode is a secondary mode, the sound wave receiving means 107 is positioned at a 90-degree angle to the sound wave transmitting means 106. This makes it possible to ensure an appropriate phase difference relationship between the transmitted wave and the received wave, even when using a secondary mode. <Variation> This disclosure is not limited to the embodiments described above, and various modifications are possible without departing from its essence. Some modifications are described below.

[0068] (Variations in system configuration) In the above embodiment, a standalone configuration in which the viscosity estimation device 100 performs processing independently was described, but the disclosure is not limited thereto. For example, the viscosity estimation system 1 may be configured as a client / server system including a measurement terminal (client) installed in the tank 200 and a server device connected via a network. In this case, the measurement terminal controls the speaker 106, microphone 107, and mixing device 108, and acquires and transmits data of the received signal. On the other hand, the server device stores a calibration curve data table 1022 and a measurement condition table 1023, which are held in the storage unit 102. The server device analyzes the signal data received from the measurement terminal, calculates the settling time by referring to the calibration curve data table 1022 and the measurement condition table 1023, and estimates the viscosity. With this configuration, it is possible to centrally manage viscosity information of tanks 200 located in multiple locations and to perform more advanced analysis by utilizing the computing power of the server side.

[0069] (Estimation of the presence or absence of solid matter) Furthermore, the viscosity estimation device 100 according to the above embodiment may also have a function to estimate the presence or absence of solid matter (sludge, foreign matter, etc.) contained in the liquid, in addition to the viscosity of the liquid. By focusing on a specific vibration mode of the tank 200, it may be possible to detect the influence of solid matter.

[0070] Specifically, the estimation control unit 1015 (or a separately provided second estimation means) analyzes the received signal from a microphone (microphone 107, or a separately added second microphone) positioned at a 90-degree angle to the speaker 106. As shown in Figure 12, when the vibration mode of the circular cross-sectional tank 200 is the second mode (n=2), the microphone positioned at 90 degrees has the characteristic of obtaining a phase shift of -180 degrees relative to the signal from the speaker 106. Here, if solid matter is mixed in the liquid, in addition to the effect of phase shift due to viscosity, the effects of absorption and scattering of sound waves by the solid matter appear. In particular, because solid matter has the effect of absorbing acoustic energy, attenuation occurs in the "amplitude" of the received signal. The estimation control unit 1015 monitors the amplitude level (sound absorption characteristics) of the received signal in parallel with or independently of monitoring the phase information. Based on the amount of amplitude attenuation, the amount of shift of the resonance peak in a specific frequency band, or a combination thereof, the estimation control unit 1015 estimates the presence or absence of solid matter in the liquid, or the concentration of solid matter. Furthermore, solid matter in a liquid may be referred to as the third object, following the first and second objects. This makes it possible to evaluate the state of the liquid from multiple perspectives, either in conjunction with or independently of viscosity estimation.

[0071] (Estimated based on signal recovery behavior) Furthermore, the viscosity estimation method is not limited to measuring the time it takes for the signal to completely return to a stable state. The estimation control unit 1015 may estimate the viscosity of the first target based on the temporal progression (recovery behavior) of the relationship (phase difference or amplitude difference) between the transmitted sound wave and the received sound wave after mixing has stopped. This may include using the recovery speed, fitting parameters to the recovery curve, or signal values ​​at specific timings in the transient state.

[0072] (Variations regarding the selection of transmission frequency) In the above embodiment, an example was described in which the frequency at which the second object (bubble) itself resonates (such as the Minert frequency) was selected as the recommended transmission frequency, but the method of selecting the frequency is not limited to this. For example, a frequency may be selected that maximizes the difference (amount of change) between the "unmixed state" in which only the first object (liquid) exists and the "mixed state" in which the first object and the second object are mixed.

[0073] Specifically, for example, the inherent resonant frequency of the first object contained in tank 200 is identified in advance. Then, when the second object is mixed in, the frequency at which the largest shift (change) occurs in the phase, amplitude, or combination thereof of the received signal is selected as the transmission frequency for measurement. This method makes it possible to sensitively detect the effect of changes in sound velocity due to mixing on the resonant mode of the entire system, including tank 200.

[0074] (Application to water treatment processes and storage facilities) The viscosity estimation system 1 according to the above embodiment may be applied to a water treatment device for purifying wastewater, etc., or to a storage tank for temporarily storing liquid. The water treatment device is not limited to a circulating system, but may also be a unidirectional (one-way) treatment system. The water treatment device may include, for example, a wastewater adjustment tank, a biological treatment tank, a treated water storage tank, etc. The water treatment device may also include a chemical reaction tank. As a mixing device 108, for example, an aeration device (blower, etc.) originally installed in each tank can be reused. The viscosity estimation device 100 estimates the viscosity of the treated water by utilizing the period when aeration in the water treatment process is stopped (when intermittent operation is stopped, etc.). The estimated viscosity can be used, for example, for sludge concentration management or condition management (detection of decreased microbial activity when the sludge is low viscosity, or detection of biological treatment failure and the resulting putrefaction when the sludge is high viscosity, etc.), detection of liquid putrefaction in the storage tank, determination of the progress of the treatment process, or evaluation of the risk of membrane clogging in the filtration membrane.

[0075] (Applications to food, chemical, and hygiene equipment) The viscosity estimation system 1 according to the above embodiment can be used to understand and control the state of various liquids in food factories, chemical plants, or sanitary equipment. For example, in a reaction tank between food and chemicals, changes in liquid properties (polymerization, decomposition, fermentation, etc.) associated with biological or chemical reactions can be monitored in real time or intermittently as changes in viscosity, and can be used to detect the endpoint of the reaction or for quality control. It can also be applied to portable handwashing devices that purify and reuse used water, as well as to stationary handwashing facilities or water supply and drainage equipment. The viscosity estimation device 100 monitors the viscosity of water in a tank or pipe to detect the degree of impurity contamination or the residual concentration of detergents and chemicals. For example, if the viscosity deviates from a predetermined range, the control unit 101 determines that liquid replacement, replenishment, or wastewater treatment is necessary, and notifies the user via the output unit 105 or performs automatic control of the device.

[0076] (Variations regarding the shape of the container) The cross-sectional shape of the container in the above embodiment is not limited to a circle, but may be a polygon such as a square, or an ellipse. Furthermore, the container is not limited to a tank, but may be a container of various shapes such as piping in a plant. The shape, dimensions, and material of the container will determine the specific vibration mode excited when sound waves are applied.

[0077] Therefore, in order to maximize measurement sensitivity, it is desirable that the speaker 106 and microphone 107 be positioned in a location that efficiently utilizes the vibration mode in which the signal change due to the presence or absence of bubbles is most pronounced. For example, when utilizing the third-order mode vibration in a particular cylindrical tank, positioning the speaker 106 and microphone 107 opposite each other (180-degree arrangement) allows for clear detection of the phase shift caused by bubbles as a signal cancellation effect. Also, when utilizing the second-order mode vibration, a 90-degree arrangement may be effective. Information on these optimal arrangements and the corresponding transmission frequencies may be included and stored in the measurement condition table 1023.

[0078] (Variations obtained by optical measurement) Although the above embodiment describes a configuration for estimating viscosity using sound waves, this disclosure is not limited thereto. The viscosity estimation system 1 may also be configured to estimate viscosity using light instead of, or in addition to, sound waves.

[0079] In this case, a light source (light irradiation means) is provided instead of the speaker 106 (sound wave transmitting means), and an optical sensor (light receiving means) is provided instead of the microphone 107 (sound wave receiving means) to detect the intensity or spectrum of light. After the mixing (bubble generation) by the mixing device 108 is stopped, the control unit 101 irradiates the first target (liquid), the second target (bubbles), or a mixture thereof with light from the light source and measures the transmitted or reflected light with the optical sensor.

[0080] If a second object (such as bubbles) is mixed in with the first object, its behavior (optical properties) in relation to incident light will be different from that of the first object alone. After mixing stops, the estimation control unit 1015 measures the time (settlement time) until this change in optical properties disappears and the mixture returns to a stable state, and estimates the viscosity of the first object based on this time.

[0081] Here, examples of optical phenomena that can be used to detect the presence of a second object (such as bubbles) include the following: • Light absorption: Changes in intensity due to light absorption by bubbles. • Phase shift: A shift in the phase of light due to differences in the refractive index of the medium. • Scattering: Reduction in transmitted light or generation of scattered light due to the scattering of light at the surface of the bubble (Mie scattering, Rayleigh scattering, etc.). • Change in refractive index: Change in the average refractive index of the mixture. • Fluorescence: The change in the intensity of fluorescence emitted when a particular substance is excited. • Raman scattering: A change in scattered light originating from the molecular vibrations inherent to the material. • Light dispersion: Spectral changes due to differences in the speed of light propagation at different wavelengths. • Photoacoustic effect: Detection of sound waves (pressure waves) generated when light is converted into heat.

[0082] The estimation control unit 1015 monitors the temporal changes in the detected values ​​(light intensity, spectral distribution, or phase difference, etc.) obtained from any or a combination of these phenomena. Similar to the acoustic method, by measuring the time it takes for the detected values ​​to return to a steady state as the bubbles disappear, it becomes possible to estimate the viscosity of the liquid with high accuracy.

[0083] (Viscosity estimation under continuous mixing) In the above embodiment, an example was described in which viscosity is estimated based on the settling time after mixing is stopped, but the disclosure is not limited thereto. The viscosity estimation device 100 may estimate viscosity in real time while mixing (e.g., aeration) by the mixing device 108 is continuing.

[0084] For example, if the mixing device 108 is configured to inject air into the tank 200 at an angle, or to generate an agitated flow within the tank, bubbles in the liquid may move in a spiral or swirling motion. Such regular bubble motion manifests in the acoustic signal as periodic changes in amplitude, phase, frequency, or combinations thereof (e.g., sinusoidal signal characteristics). The estimation control unit 1015 analyzes the periodic fluctuation characteristics contained in the amplitude, phase, frequency, or combinations thereof of the received signal during continuous mixing, and estimates the viscosity based on these fluctuation characteristics.

[0085] Specifically, under conditions where the mixing intensity is constant, as the viscosity of the liquid increases, the swirling speed of the bubbles decreases due to the resistance of the liquid (viscous resistance), and the frequency of the periodic fluctuations appearing in the acoustic signal decreases. The estimation control unit 1015 can dynamically estimate the current viscosity of the liquid without stopping the mixing by referring to the correlation between the "frequency of periodic fluctuations" and "viscosity" (second calibration curve data) stored in the memory unit 102 beforehand. With this configuration, continuous monitoring is possible without interruption even while the process is running.

[0086] (others) In the embodiments described above, the cases in which the units and means are implemented by a processor have been explained, but the invention is not limited thereto. The units and means may be any hardware known to perform the operation.

[0087] Furthermore, although the above embodiment describes an example in which the server 20 provides each function, the configuration is not limited to this. Some or all of the functions provided by the server 20 in this embodiment may be provided by the terminal device 10 instead of the server 20.

[0088] Although several embodiments of this disclosure have been described above, these embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, configurations and processes in one embodiment may be combined with configurations and processes in another embodiment, or a modification of one embodiment may be applied to another embodiment. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0089] (Note) The details described in each of the above embodiments are noted below.

[0090] (Note 1) A system comprising: a mixing means for mixing a first object and a second object having different specific gravities; a sound wave transmitting means for transmitting sound waves to the first object, the second object, or a mixture thereof; a sound wave receiving means for receiving sound waves transmitted from the sound wave transmitting means and propagated through the first object, the second object, or a mixture thereof; and an estimation means for estimating the viscosity of the first object based on changes in the received signal received by the sound wave receiving means. (Note 2) The system as described in Appendix 1, wherein the sound wave receiving means receives sound waves transmitted from the sound wave transmitting means during mixing by the mixing means, and the estimation means estimates the viscosity of the first object based on the periodic fluctuation characteristics contained in the received signal received by the sound wave receiving means. (Note 3) The system as described in (Note 1) or (Note 2), wherein the mixing means mixes the first object and the second object and then stops the mixing; the sound wave receiving means receives sound waves transmitted from the sound wave transmitting means after the mixing by the mixing means has stopped; and the estimation means measures the time until the phase difference between the transmitted sound waves and the received sound waves recovers to a stable state after the mixing has stopped, and estimates the viscosity of the first object based on that time. (Note 4) The estimation means is a system according to any one of (Appendix 1) to (Appendix 3) that detects the occurrence and disappearance of a phase shift due to bubbles by monitoring the difference in amplitude between the sound wave transmitted by the sound wave transmitting means and the sound wave received by the sound wave receiving means. (Note 5) The sound wave receiving means is arranged in a positional relationship such that the difference in amplitude between the sound wave transmitted by the sound wave transmitting means and the sound wave received by the sound wave receiving means is maximized in a specific vibration mode of the container, as described in any of the systems described in (Appendix 1) to (Appendix 4). (Note 6) A method to be performed on a computer equipped with a processor, wherein the processor performs a mixing step of mixing a first object and a second object having different specific gravities; a sound wave transmission step of transmitting sound waves to the first object, the second object, or a mixture thereof; a sound wave reception step of receiving the transmitted sound waves that have propagated through the first object, the second object, or a mixture thereof; and an estimation step of estimating the viscosity of the first object based on changes in the received signal. (Note 7) A program to be executed by a computer equipped with a processor, the program causing the processor to perform a mixing step of mixing a first object and a second object having different specific gravities; a sound wave transmission step of transmitting sound waves to the first object, the second object, or a mixture thereof; a sound wave reception step of receiving the transmitted sound waves that have propagated through the first object, the second object, or a mixture thereof; and an estimation step of estimating the viscosity of the first object based on the changes in the received signal. (Note 8) An apparatus comprising a processor, wherein the processor performs a mixing step of mixing a first object and a second object having different specific gravities; a sound wave transmission step of transmitting sound waves to the first object, the second object, or a mixture thereof; a sound wave reception step of receiving the transmitted sound waves that have propagated through the first object, the second object, or a mixture thereof; and an estimation step of estimating the viscosity of the first object based on changes in the received signal. [Explanation of Symbols]

[0091] 1…Viscosity estimation system 100...Viscosity estimation device 101... Control Unit 102...Storage section 103... Communications Department 104...Input section 105...Output section 106...Speaker 107... Mike 108…Mixing device 200... tank

Claims

1. A mixing means for mixing a first object and a second object having different specific gravities, During mixing by the mixing means, a sound wave transmitting means transmits sound waves to the mixture of the first object and the second object. A sound wave receiving means that receives sound waves transmitted from the sound wave transmitting means and propagated by the mixture, Estimation means for estimating the viscosity of the first target based on the periodic fluctuation characteristics contained in the received signal received by the sound wave receiving means, A system equipped with these features.

2. A mixing means for mixing a first object and a second object having different specific gravities, and then stopping the mixing, After the mixing is stopped, a sound wave transmitting means transmits sound waves to the first object, the second object, or a mixture thereof. Sound wave receiving means for receiving the sound waves transmitted from the sound wave transmitting means and propagating through the first object, the second object, or a mixture thereof, After the mixing stops, the time required for the phase difference between the transmitted sound wave and the received sound wave to recover to a stable state is measured, and the viscosity of the first target is estimated based on this time. A system equipped with these features.

3. The system according to claim 2, wherein the estimation means monitors the difference in amplitude between the sound wave transmitted by the sound wave transmitting means and the sound wave received by the sound wave receiving means to detect the occurrence and disappearance of a phase shift caused by the second object.

4. A container comprising the first object and the second object, The sound wave transmitting means and the sound wave receiving means are arranged on the outer surface of the container. The sound wave transmitting means transmits sound waves through the container toward the first object, the second object, or a mixture thereof. The system according to claim 2, wherein the sound wave transmitting means and the sound wave receiving means are arranged in a positional relationship such that the difference in amplitude between the sound wave transmitted by the sound wave transmitting means and the sound wave received by the sound wave receiving means is maximized in the vibration mode excited in the container.

5. A method to be performed on a computer equipped with a processor, The aforementioned processor, A mixing step in which a first substance and a second substance having different specific gravities are mixed, During the mixing step, a sound wave transmission step is performed in which sound waves are transmitted to the mixture of the first object and the second object. A sound wave receiving step of receiving the sound waves transmitted and propagating the mixture, An estimation step of estimating the viscosity of the first target based on the periodic fluctuation characteristics contained in the received signal; How to do it.

6. A program to be executed on a computer equipped with a processor, The aforementioned processor, A mixing step in which a first substance and a second substance having different specific gravities are mixed, During the mixing step, a sound wave transmission step is performed in which sound waves are transmitted to the mixture of the first object and the second object. A sound wave receiving step of receiving the sound waves transmitted and propagating the mixture, An estimation step of estimating the viscosity of the first target based on the periodic fluctuation characteristics contained in the received signal; A program that executes the command.

7. A device equipped with a processor, The aforementioned processor, A mixing step in which a first substance and a second substance having different specific gravities are mixed, During the mixing step, a sound wave transmission step is performed in which sound waves are transmitted to the mixture of the first object and the second object. A sound wave receiving step of receiving the sound waves transmitted and propagating the mixture, An estimation step of estimating the viscosity of the first target based on the periodic fluctuation characteristics contained in the received signal; A device that performs this task.

8. A method to be performed on a computer having a processor, The aforementioned processor, A mixing step in which a first substance and a second substance having different specific gravities are mixed, and then the mixing is stopped. After the mixing is stopped, a sound wave transmission step is performed to transmit sound waves to the first object, the second object, or a mixture thereof. A sound wave receiving step of receiving the sound waves transmitted and propagating through the first target, the second target, or a mixture thereof, After the mixing is stopped, the time until the phase difference between the transmitted sound wave and the received sound wave returns to a stable state is measured, and the viscosity of the first target is estimated based on this time. How to do it.

9. A program to be executed by a computer equipped with a processor, The aforementioned processor, A mixing step in which a first substance and a second substance having different specific gravities are mixed, and then the mixing is stopped. After the mixing is stopped, a sound wave transmission step is performed to transmit sound waves to the first object, the second object, or a mixture thereof. A sound wave receiving step of receiving the sound waves transmitted and propagating through the first target, the second target, or a mixture thereof, After the mixing is stopped, the time until the phase difference between the transmitted sound wave and the received sound wave returns to a stable state is measured, and the viscosity of the first target is estimated based on this time. A program that executes the command.

10. A device comprising a processor, The aforementioned processor, A mixing step in which a first substance and a second substance having different specific gravities are mixed, and then the mixing is stopped. After the mixing is stopped, a sound wave transmission step is performed to transmit sound waves to the first object, the second object, or a mixture thereof. A sound wave receiving step of receiving the sound waves transmitted and propagating through the first target, the second target, or a mixture thereof, After the mixing is stopped, the time until the phase difference between the transmitted sound wave and the received sound wave returns to a stable state is measured, and the viscosity of the first target is estimated based on this time. A device that performs this task.

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