Sensor system, vehicle equipped with same, and radio wave transmitting / receiving method

Abstract

Provided are: a sensor system for controlling a sampling frequency of an electromagnetic wave emitted by a radio wave sensor to reduce power consumption; a vehicle provided with the same; and a radio wave transmission / reception method in the sensor system. A sensor system (1) is configured by including a radio wave sensor (2), a vibration sensor (3), and a signal processing device (4). The radio wave sensor (2) emits a radio wave toward a measurement target (5), receives a reflected wave, and outputs reflected-wave data to the signal processing device (4). The vibration sensor (3) detects vibration superimposed as noise on the reflected wave received by the radio wave sensor (2) and outputs detected vibration data to the signal processing device (4). A sampling frequency setting unit (4a) of the signal processing device (4) recognizes a frequency range of vibration to be detected by the vibration sensor (3) to specify an upper limit of the frequency range, and sets a sampling frequency of the radio wave to be emitted by the radio wave sensor (2) to the sampling frequency having the specified upper-limit frequency as a Nyquist frequency.

Description

[Technical field]

[0001] The present invention relates to a sensor system that emits electromagnetic waves from a radio wave sensor and receives reflected waves returning from an object to be measured, a vehicle equipped with the sensor system, and a radio wave transmitting and receiving method. [Background technology]

[0002] Conventionally, an example of this type of sensor system is disclosed in Patent Document 1.

[0003] This sensor system includes a radio wave sensor, a vibration sensor, and a signal processing device. The radio wave sensor transmits radio waves within a detection area, receives radio waves reflected by an object, and outputs a radio wave sensor signal according to the state of the object to the signal processing device. The vibration sensor detects vibrations of at least one of the radio wave sensor and the object, and outputs a vibration sensor signal according to the detected vibrations to the signal processing device. The signal processing device attenuates the vibration component detected in the vibration sensor signal from the radio wave sensor signal to generate a signal mainly including components of the object. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-71326 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional sensor system disclosed in Patent Document 1, the upper limit of the frequency of the vibration sensor signal detected by the vibration sensor is empirically determined. The radio wave sensor is operated by setting the sampling frequency of the radio waves emitted from the radio wave sensor to a sampling frequency that can adequately obtain the vibration sensor signal of the empirically determined frequency. For this reason, in the conventional sensor system, depending on the vibration component superimposed on the radio wave sensor signal, the sampling frequency of the radio waves emitted from the radio wave sensor may be excessively high, resulting in unnecessary power consumption. [Means for solving the problem]

[0006] The present invention has been made to solve such problems, a radio wave sensor that emits electromagnetic waves toward a measurement target and receives reflected waves that are generated when the electromagnetic waves hit the measurement target and are reflected; a vibration sensor that detects vibrations that are superimposed on the reflected wave as noise; a sampling frequency setting unit that recognizes a frequency range of a vibration, specifies an upper limit of the frequency of the vibration, determines a sampling frequency of an electromagnetic wave emitted by the radio wave sensor to be a sampling frequency at which the specified upper limit frequency becomes a Nyquist frequency, and sets the determined sampling frequency as the sampling frequency of the electromagnetic wave emitted by the radio wave sensor; A sensor system comprising the above components was constructed.

[0007] The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: a vibration detection step of emitting an electromagnetic wave from the radio wave sensor toward a measurement target and detecting, by a vibration sensor, vibration superimposed as noise on a reflected wave of the electromagnetic wave that is reflected by the measurement target; a vibration frequency upper limit identification step of identifying an upper limit of the vibration frequency by recognizing a frequency range of the vibration; a sampling frequency determination step of determining a sampling frequency of the electromagnetic wave emitted by the radio wave sensor to a sampling frequency at which the specified upper limit frequency becomes the Nyquist frequency; a sampling frequency setting step of setting the sampling frequency of the electromagnetic wave to the sampling frequency determined in the sampling frequency determination step; The radio wave transmitting and receiving method includes the steps of:

[0008] According to these configurations, the sampling frequency setting unit or the vibration frequency upper limit specifying step recognizes the frequency range of vibrations that are superimposed as noise on the reflected waves of the electromagnetic waves received by the radio wave sensor, and specifies the upper limit of the frequency of the vibrations that are superimposed as noise. Then, the sampling frequency setting unit or the sampling frequency determination step determines the sampling frequency of the electromagnetic waves emitted by the radio wave sensor to be a sampling frequency at which the specified upper limit frequency is the Nyquist frequency. The sampling frequency of the electromagnetic waves emitted from the radio wave sensor is set to the determined sampling frequency by the sampling frequency setting unit or the sampling frequency setting step.

[0009] Therefore, the radio wave sensor emits electromagnetic waves at a sampling frequency determined based on the vibrations actually detected by the vibration sensor, which eliminates the needless power consumption caused by the conventional electromagnetic wave sensor emitting electromagnetic waves at an excessively high sampling frequency, thereby reducing the power consumption of the sensor system.

[0010] The present invention also provides a vehicle equipped with the sensor system described above.

[0011] According to this configuration, a vehicle equipped with a sensor system capable of reducing power consumption can be provided. Effect of the Invention

[0012] According to the present invention, it is possible to provide a sensor system in which the sampling frequency of the electromagnetic waves emitted by a radio wave sensor is suppressed to reduce power consumption, a vehicle equipped with the sensor system, and a radio wave transmission and reception method. [Brief description of the drawings]

[0013] [Figure 1] 1 is a block diagram showing a schematic configuration of a sensor system according to a first embodiment of the present invention. [Diagram 2] 4 is a flowchart showing the process of a radio wave transmitting and receiving method according to an embodiment of the present invention. [Diagram 3] 2 is a diagram showing an example of the relationship between the frequency of vibrations measured by the sensor system shown in FIG. 1 and the frequency of a vital sign. [Figure 4] FIG. 2 is a perspective view showing the interior of a vehicle equipped with the sensor system shown in FIG. 1 as a driver monitoring system. [Diagram 5] FIG. 11 is a block diagram showing a schematic configuration of a sensor system and a configuration of a vibration component removing unit according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a block diagram showing a schematic configuration of a sensor system according to a third embodiment of the present invention. [Figure 7] FIG. 13 is a block diagram showing a schematic configuration of a sensor system according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Next, a sensor system, a vehicle including the same, and a radio wave transmitting and receiving method according to an embodiment of the present invention will be described.

[0015] 1 is a block diagram showing a schematic configuration of a sensor system 1 according to a first embodiment of the present invention. The sensor system 1 includes a radio wave sensor 2, a vibration sensor 3, and a signal processing device 4.

[0016] The radio wave sensor 2 emits electromagnetic waves towards the measurement object 5, receives reflected waves that hit the measurement object 5 and are reflected (reflection is incident), and outputs the received reflected wave data to the signal processing device 4. The radio wave sensor 2 detects the state of the measurement object 5, for example, body surface displacement of the human body, from the reflected waves. The radio wave sensor 2 is configured by, for example, a Doppler radar, an FMCW (Frequency Modulated Continuous Wave radar), a pulse radar, or the like. In this embodiment, the electromagnetic waves emitted by the radio wave sensor 2 will be described as radio waves, but electromagnetic waves widely include sound waves, light waves, and the like.

[0017] The vibration sensor 3 detects vibrations superimposed as noise on the reflected waves received by the radio wave sensor 2, and outputs the detected vibration data to the signal processing device 4. The vibration sensor 3 is configured by, for example, a six-axis inertial sensor or a three-axis acceleration sensor.

[0018] The signal processing device 4 includes a sampling frequency setting unit 4a. The sampling frequency setting unit 4a recognizes the frequency range of the vibration detected by the vibration sensor 3 and specifies the upper limit of the vibration frequency as described below. Then, the sampling frequency of the electromagnetic waves emitted by the radio wave sensor 3 is determined to be the sampling frequency at which the specified upper limit frequency becomes the Nyquist frequency. Then, the determined sampling frequency is set as the sampling frequency of the radio waves emitted by the radio wave sensor 2. Note that, instead of calculating the sampling frequency each time, if the target to which the sensor system 1 is applied is determined, a value measured in advance according to the target may be stored in advance.

[0019] 2 is a schematic flowchart of a radio wave transmission and reception method according to an embodiment of the present invention when the method is applied to the above-mentioned sensor system 1. Each of steps S101 to S104 performed in this radio wave transmission and reception method is performed by a CPU (Central Processing Unit) included in the signal processing device 4 in accordance with a computer program stored in a memory included in the signal processing device 4.

[0020] In the radio wave transmission and reception method in the sensor system 1, first, a vibration detection step S101 is performed in which vibration is detected by the vibration sensor 3. That is, the vibration sensor 3 detects vibration that is superimposed as noise on the reflected wave received by the radio wave sensor 2 when the electromagnetic wave emitted from the radio wave sensor 2 hits the measurement target 5. The detected vibration data is output by the vibration sensor 3 to the sampling frequency setting unit 4a.

[0021] Next, a vibration frequency upper limit specification step S102 is performed in which the frequency of the vibration is recognized and an upper limit of the frequency is specified. That is, the frequency range of the vibration detected by the vibration sensor 3 is recognized by the sampling frequency setting unit 4a, and an upper limit of the frequency of the vibration superimposed as noise on the reflected wave received by the radio wave sensor 2 is specified.

[0022] Next, a sampling frequency determination step S103 is performed in which a sampling frequency fs of the radio wave sensor 2 is determined from the identified upper frequency limit. That is, the sampling frequency fs of the radio wave emitted by the radio wave sensor 2 is determined to be the sampling frequency fs at which the upper limit frequency fupper identified in the vibration frequency upper limit identification step S102 becomes the Nyquist frequency fn.

[0023] Next, a sampling frequency setting step S104 is performed in which the determined sampling frequency fs is set in the radio wave sensor 2. That is, the sampling frequency fs of the radio waves emitted by the radio wave sensor 2 is set to the sampling frequency fs determined in the sampling frequency determination step S103. This causes the radio wave sensor 2 to emit radio waves to the measurement target 5 at the sampling frequency fs.

[0024] Thereafter, radio waves are emitted from the radio wave sensor 2 towards the measurement target 5, and the radio waves that hit the measurement target 5 and are reflected are received by the radio wave sensor 2. The received reflected wave data is output by the radio wave sensor 2 to the sampling frequency setting unit 4a.

[0025] In the vibration frequency upper limit specifying step S102, the upper limit of the vibration frequency is specified, for example, by analyzing frequency information obtained by Fourier transforming the vibration data and the intensity of the vibration data at each frequency. When the measurement object 5 is a human body and the body surface displacement of the human body is measured to detect vital signs such as breathing and heart rate of the human body, the frequency of the vital sign component detected by the radio wave sensor 2 is approximately 0 to 10 Hz, as shown in Fig. 3. In other words, the frequency of the measurement object 5, for example the frequency of the body surface displacement, is often lower than the vibration frequency, such as 0 to several hundreds Hz or several thousand Hz.

[0026] In such a case, the frequency components of approximately 0 to 10 Hz, which are the measurement target 5, are extracted from the reflected wave data through a low-pass filter, and the reflected wave data is analyzed. At that time, the vibration components are removed or attenuated from the reflected wave data containing vibration as noise to an extent that body surface displacement data and the like can be sufficiently extracted. Signal processing is performed in such a reduced state of the vibration data. For this reason, in the frequency range of the vibration recognized by the vibration sensor 3, the highest vibration frequency is found among the frequency components exceeding the threshold value Pth of the intensity at which body surface displacement data and the like can be sufficiently extracted by the signal processing, among the frequency information obtained by Fourier transform. Then, the highest vibration frequency is identified as the upper limit of the vibration frequency.

[0027] For example, in the relationship between the vibration frequency and the vital sign frequency shown as an example in Fig. 3, if the frequencies above 200 Hz do not include a vibration frequency with an intensity exceeding the threshold value Pth, 200 Hz is specified as the upper limit frequency fupper in vibration frequency upper limit specification step S102. Therefore, in this case, in sampling frequency determination step S103, the sampling frequency fs of the radio wave emitted by the radio wave sensor 2 is determined to be 400 Hz (= 200 Hz × 2), which is the sampling frequency fs at which the specified upper limit frequency fupper, 200 Hz, becomes the Nyquist frequency fn.

[0028] According to the sensor system 1 according to the first embodiment shown in Fig. 1 and the radio wave transmission / reception method in the sensor system 1 according to the embodiment shown in the flowchart of Fig. 2, as described above, the sampling frequency setting unit 4a and the vibration frequency upper limit specifying step S102 recognize the frequency range of vibrations that are superimposed as noise on the reflected wave of the radio wave received by the radio wave sensor 2, and specify the upper limit of the frequency of the vibrations that are superimposed as noise. Then, the sampling frequency setting unit 4a and the sampling frequency determination step S103 determine the sampling frequency fs of the radio wave emitted by the radio wave sensor 2 to be the sampling frequency fs at which the specified upper limit frequency fupper becomes the Nyquist frequency fn. The sampling frequency fs of the radio wave emitted from the radio wave sensor 2 is set to the determined sampling frequency fs by the sampling frequency setting unit 4a and the sampling frequency setting step S104.

[0029] Therefore, the radio wave sensor 2 emits radio waves at a sampling frequency fs that is determined based on the vibrations actually detected by the vibration sensor 3. This makes it possible to restrict the frequency range of the radio waves emitted from the radio wave sensor 2. This makes it possible to shorten the time during which the radio wave sensor 2 emits radio waves and the operation time of an analog-to-digital conversion (ADC) circuit in the signal processing device 4 and the like. As a result, the radio wave sensor 2 no longer emits radio waves at an excessively high sampling frequency fs as in the past. This prevents unnecessary power consumption and allows the power consumption of the sensor system 1 to be reduced.

[0030] FIG. 4 is a perspective view showing the interior of a vehicle 11 equipped with such a sensor system 1 as a driver monitoring system (DMS).

[0031] When the sensor system 1 is thus provided in the vehicle 11, the radio wave sensor 2 is installed on the seat backrest 11a, seat portion 11b, dashboard 11c, ceiling 11d of the vehicle cabin, etc., and the human body sitting in the seat is treated as the measurement object 5, and radio waves are irradiated (emitted) to the human body. In addition, the vibration sensor 3 is installed on the seat backrest 11a, seat portion 11b, floor 11e of the vehicle cabin, etc. When the vibration sensor 3 is installed on the seat backrest 11a or seat portion 11b, the body movement of the human body and the vibration of the vehicle are detected as vibrations, and when installed on the floor 11e of the vehicle cabin, the vibration of the vehicle is detected.

[0032] According to this configuration, it is possible to provide a vehicle 11 equipped with a sensor system 1 capable of reducing power consumption.

[0033] The sensor system 1 can also be configured with a radio wave sensor, a vibration sensor, and a CPU provided in a wearable device such as a smartwatch or a smartphone. In this case, the radio wave sensor, the vibration sensor, and the CPU provided in the wearable device or smartphone function as the radio wave sensor 2, the vibration sensor 3, and the signal processing device 4 shown in Fig. 1. The program of the flowchart shown in Fig. 2 is downloaded as an application from the Internet or the like and installed in the wearable device or smartphone.

[0034] 5(a) is a block diagram showing a schematic configuration of a sensor system 1A according to a second embodiment of the present invention. The sensor system 1A differs from the sensor system 1 according to the first embodiment in that the signal processing device 4 is provided with a vibration component removing unit 4b and a communication unit 4c, but is otherwise similar to the sensor system 1 according to the first embodiment.

[0035] The vibration component removal unit 4b removes or attenuates components of vibration data detected by the vibration sensor 3 as noise from the reflected wave data received by the radio wave sensor 2. When the measurement target 5 is, for example, a human body and the reflected wave data includes body surface displacement of the human body, this removal or attenuation allows the body surface displacement of the human body to be extracted. The communication unit 4c transmits the extracted body surface displacement data wirelessly or via cable to an external device such as a personal computer or an ECU (Electronic Control Unit) in a vehicle. The external device performs a predetermined process using the received body surface displacement data, etc.

[0036] The vibration component removal unit 4b uses blind source separation techniques such as Independent Component Analysis (ICA) and Independent Vector Analysis (IVA) to separate the vibration data input from the vibration sensor 3 from the reflected wave data input from the radio wave sensor 2. In this case, the dimension of the reflected wave data is m in SI units, and the dimension of the vibration data is m / s in SI units. 2 Therefore, the calculation process in the vibration component removing unit 4b involves integrating the vibration data twice, and then performing independent component analysis and independent vector analysis.

[0037] The vibration component removal unit 4b may be an adaptive filter using an algorithm such as LMS (Least Mean Square). The adaptive filter can separate the vibration data input from the vibration sensor 3 from the reflected wave data input from the radio wave sensor 2. Fig. 5(b) is a block diagram showing a circuit configuration of the vibration component removal unit 4b configured using such an adaptive filter 4b1.

[0038] The noise (vibration data) superimposed on the reflected wave data input from the radio wave sensor 2 propagates a distance away from its source and is therefore affected by the transfer characteristics along that distance. Therefore, the vibration component removal unit 4b obtains the difference between the reflected wave data and the vibration data using a subtractor 4b2, and feeds back the difference from the output of the subtractor 4b2 to the adaptive filter 4b1. The adaptive filter 4b1 then adjusts the magnitude of the transfer coefficient W1 to separate the vibration data from the reflected wave data and extract the body surface displacement, etc.

[0039] The vibration component remover 4b may use a machine learning method such as Demucs, Sepformer, Conv-TasNet, or a modified version thereof, which is used for voice separation. By using these methods, it is possible to separate the vibration data input from the vibration sensor 3 from the reflected wave data input from the radio wave sensor 2.

[0040] According to the sensor system 1A of the second embodiment, it is possible to remove or attenuate the components of the vibration data detected by the vibration sensor 3 from the reflected wave data received by the radio wave sensor 2 with reduced power consumption and without changing the performance of removing the vibration components. Moreover, the sensor system 1A of the second embodiment can also be applied to a driver monitoring system by appropriately arranging the radio wave sensor 2 and the vibration sensor 3 in the passenger compartment of the vehicle 11 as described with reference to Fig. 4. In this case, it is possible to provide a vehicle 11 equipped with the sensor system 1A that can reduce power consumption and does not change the performance of removing the vibration components.

[0041] 6 is a block diagram showing a schematic configuration of a sensor system 1B according to a third embodiment of the present invention. The sensor system 1B differs from the sensor system 1A according to the second embodiment in that the signal processing device 4 is provided with a vital sign detection unit 4d and the measurement target 5 is a human body, but is otherwise similar to the sensor system 1A according to the second embodiment.

[0042] The vital sign detector 4d detects the vital signs of the human body from the reflected wave data from which the vibration data components have been removed or attenuated by the vibration component remover 4b. The vital signs include the heart rate, heart rate variability, respiratory rate, and respiratory depth of the human body that is the measurement target 5. Based on the reflected wave data input from the radio wave sensor 2, the vital signs are detected from the body surface displacement of the human body that is measured as the change in the distance from the radio wave sensor 2 to the point on the human body where the radio waves are irradiated.

[0043] According to the sensor system 1B of the third embodiment, the vital signs of the human body can be detected with reduced power consumption from the reflected wave data from which the vibration components have been removed or attenuated by the vibration component removing unit 4b, without changing the performance of removing the vibration components from the vital signs. The sensor system 1B of the third embodiment can also be applied to a driver monitoring system by appropriately arranging the radio wave sensor 2 and the vibration sensor 3 in the passenger compartment of the vehicle 11 as described with reference to FIG. 4. In this case, it is possible to provide a vehicle 11 equipped with the sensor system 1B that can reduce power consumption and does not change the performance of removing the vibration components from the vital signs.

[0044] 7 is a block diagram showing a schematic configuration of a sensor system 1C according to a fourth embodiment of the present invention. The sensor system 1C differs from the sensor system 1 according to the first embodiment in that the vibration sensor 3 is configured by a vibration sensor built into a wearable device such as a smartwatch or a smartphone 6. The other points are similar to the sensor system 1 according to the first embodiment. The wearable device or smartphone 6 is not limited to these and may be any portable device having a communication function with the vibration sensor 3. In this configuration, communication between the vibration sensor 3 and the signal processing device 4 is performed wirelessly, such as by Bluetooth (registered trademark), or by wire.

[0045] According to the sensor system 1C of the fourth embodiment, radio waves having a sampling frequency fs based on vibrations actually detected by a vibration sensor built into a wearable device or a smartphone 6 are emitted from the radio wave sensor 2. Therefore, it is possible to provide a sensor system 1C that can reduce power consumption by restricting the frequency range of the radio waves emitted from the radio wave sensor 2 while simplifying the configuration of the sensor system 1C and reducing the product price.

[0046] In the sensor system 1A according to the second embodiment and the sensor system 1B according to the third embodiment, the vibration sensor 3 can be configured by a vibration sensor built into a wearable device such as a smart watch or a smartphone 6, as in the sensor system 1C according to the fourth embodiment. In this case, the same effects as those of the sensor system 1C according to the fourth embodiment can be achieved. In addition, the sensor system 1C according to the fourth embodiment can also be applied to a driver monitoring system by appropriately arranging the radio wave sensor 2 and the wearable device or smartphone 6 serving as the vibration sensor 3 in the passenger compartment of the vehicle 11, as described with reference to FIG. 4. In this case, the vehicle 11 equipped with the sensor system 1C capable of reducing power consumption can also be provided. [Explanation of symbols]

[0047] 1, 1A, 1B, 1C...Sensor system 2. Radio wave sensor 3. Vibration sensor 4. Signal processing device 4a…Sampling frequency setting section 4b...Vibration component removal section 4c…Communications Department 4d…Vital signs detector 5. Measurement target 6. Wearable devices or smartphones

Claims

1. a radio wave sensor that emits electromagnetic waves toward a measurement target and receives reflected waves that are generated when the electromagnetic waves hit the measurement target and are reflected; a vibration sensor that detects vibrations superimposed as noise on the reflected wave; a sampling frequency setting unit that recognizes a frequency range of the vibration, specifies an upper limit of the frequency of the vibration, determines a sampling frequency of the electromagnetic wave emitted by the radio wave sensor to a sampling frequency at which the specified upper limit frequency becomes a Nyquist frequency, and sets the determined sampling frequency as the sampling frequency of the electromagnetic wave emitted by the radio wave sensor; A sensor system comprising:

2. a vibration detection step of emitting an electromagnetic wave from a radio wave sensor toward a measurement target and detecting, by a vibration sensor, vibration superimposed as noise on a reflected wave of the electromagnetic wave reflected by the measurement target; a vibration frequency upper limit specifying step of recognizing a frequency range of the vibration and specifying an upper limit of the frequency of the vibration; a sampling frequency determination step of determining a sampling frequency of the electromagnetic wave emitted by the radio wave sensor to a sampling frequency at which the specified upper limit frequency is a Nyquist frequency; a sampling frequency setting step of setting a sampling frequency of the electromagnetic wave to the sampling frequency determined in the sampling frequency determination step; A radio wave transmitting and receiving method comprising:

3. The sensor system according to claim 1 , further comprising a vibration component removing unit that removes or attenuates a component of the vibration detected by the vibration sensor from the reflected wave.

4. The measurement object is a human body, 4. The sensor system according to claim 3, further comprising a vital sign detection unit that detects a vital sign of the human body from the reflected wave from which the vibration component has been removed or attenuated by the vibration component removal unit.

5. 5. The sensor system according to claim 1, wherein the vibration sensor is a vibration sensor built into a wearable device.

6. 5. The sensor system according to claim 1, wherein the vibration sensor is a vibration sensor built into a smartphone.

7. A vehicle comprising the sensor system according to claim 1, 3 or 4.

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