A millimeter-wave radar algorithm for determining the dryness of clothes in a dryer

Abstract

This invention discloses a millimeter-wave radar algorithm suitable for determining the dryness of clothes in a dryer, including the following steps: S1: using FMCW millimeter-wave radar to collect echo signals from clothes in the dryer and calculating the target distance sequence; S2: calculating the variance or standard deviation of the target distance sequence using a time window; S3: determining the dryness of the clothes based on the range of variance or standard deviation. This invention provides a millimeter-wave radar algorithm suitable for determining the dryness of clothes in a dryer, solving the problems of inaccurate measurement, slow response, and over-drying in traditional drying detection methods.

Description

Technical Field

[0001] This invention belongs to the field of dryer control technology, specifically relating to a millimeter-wave radar algorithm suitable for dryers to determine the dryness or wetness of clothes. Background Technology

[0002] Traditional dryers primarily use weight sensors or temperature and humidity sensors to determine the dryness or wetness of clothes.

[0003] Weight sensors determine dryness by comparing the weight of clothing at different times, but this leads to large weighing errors when clothing is tangled or misaligned, and they cannot detect localized dampness. Temperature and humidity sensors indirectly determine dryness by detecting the temperature and humidity of exhaust air, but this is significantly affected by ambient temperature and is prone to problems such as delayed judgment and over-drying, resulting in energy waste and damage to clothing.

[0004] Existing technologies generally suffer from inaccurate measurements, slow response, and a tendency to over-dry, making it difficult to achieve precise, energy-saving, and garment-friendly drying control. Summary of the Invention

[0005] The main objective of this invention is to provide a millimeter-wave radar algorithm suitable for determining the dryness of clothes in a dryer, solving the problems of inaccurate measurement, slow response, and over-drying in traditional drying detection methods.

[0006] To achieve the above objectives, this invention provides a millimeter-wave radar algorithm suitable for determining the dryness of clothes in a dryer, comprising the following steps: Step S1: Use FMCW millimeter-wave radar to collect echo signals of underwear in the dryer and calculate the target distance sequence; Step S2: Calculate the variance or standard deviation of the target distance sequence using a time window; Step S3: Determine the dryness or wetness of the clothing based on the range of variance or standard deviation values.

[0007] As a further preferred technical solution to the above technical solution, in step S1, the FMCW millimeter-wave radar transmits a continuous wave with a linearly changing frequency during the frequency sweep period. The echo reflected by the object has a certain frequency difference from the transmitted signal. The distance information between the target and the radar is obtained by measuring the frequency difference. Specifically, the implementation is as follows: Let the transmitted signal frequency be Tx, the received signal frequency be Rx, and the frequency sweep period be... The sweep bandwidth is The transmitted signal passes through the target, and the echo signal has a delay. During the sawtooth-shaped frequency variation, frequency measurements are performed on both the rising and falling edges. The formula is: ; The delay between signal transmission and reception. , The distance from the target to the radar. Since the speed of light is given, the formula for calculating the target distance is: ; The transmitted signal of an FMCW millimeter-wave radar is a sine wave with a linearly varying frequency. Expressed mathematically, the transmitted signal of an FMCW millimeter-wave radar is: ; in, The strength of the transmitted signal, For frequency modulation slope, The initial phase of the transmitted signal, at any time It can be expressed as , The number of modulation periods; When the transmitted signal hits a range radar The speed of movement is After reaching the target, the signal delay after reflection by the target and reception by the radar is: ; The echo signal is: ; The signal received by the radar is amplified through a series of steps and then mixed with the local oscillator signal to obtain the intermediate frequency signal. ; After removing the smallest terms, the intermediate frequency signal is approximately: ; in The beat frequency contains distance information, with a distance resolution of [missing information]. , For bandwidth; The frequency is the Doppler frequency, which contains the target's velocity information, with a velocity resolution of [missing value]. That is, to calculate the distance to the target: .

[0008] As a further preferred technical solution to the above technical solution, in step S3, the dry / wet determination logic is as follows: If the variance or standard deviation is below threshold A, the clothes are determined to be damp, and drying continues. If the variance or standard deviation is higher than the threshold B, it is determined that the clothes have begun to dry and have entered the semi-drying state. If the variance or standard deviation remains high and exceeds a preset time threshold, the clothes are determined to be completely dry, and the dryer is stopped.

[0009] As a further preferred technical solution of the above technical solution, when the clothes are wet, the high dielectric constant of the moisture causes the millimeter wave to penetrate shallowly and the echo to be stable, resulting in a target distance sequence with low variance and high stability; when the clothes are dry, the increased penetration depth of the millimeter wave forms a volume scattering effect, resulting in a target distance sequence with high variance and low stability.

[0010] The beneficial effects of this invention are as follows: 1. Directly detects the garment itself, unaffected by tangling, uneven loading, or ambient temperature and humidity, ensuring accurate judgment; 2. Fast response, no lag, avoids over-drying, saves energy and protects clothes; 3. The algorithm is simple and reliable, requires no complex calibration, and is compatible with various types of dryers; 4. Supports dryness / wetness detection for clothing made of various materials such as cotton, synthetic fibers, and anti-static clothing. Attached Figure Description

[0011] Figure 1 This is a flowchart illustrating the present invention.

[0012] Figure 2 This is a schematic diagram of the transmit / receive signal frequencies of the FMCW millimeter-wave radar of the present invention.

[0013] Figure 3 This is a waveform diagram of the present invention.

[0014] Figure 4 This is a waveform diagram of SPQ and SPIQ of the present invention.

[0015] Figure 5 This is a schematic diagram of the waveforms of SPQ and SPIQ after CZT transformation according to the present invention.

[0016] Figure 6 This is a schematic diagram showing the distance and amplitude results of millimeter-wave radar detection of targets during the process of different garments changing from wet to dry in the dryer. Detailed Implementation

[0017] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0018] In the preferred embodiments of the present invention, those skilled in the art should note that the dryer, FMCW millimeter-wave radar, etc. involved in the present invention can be regarded as prior art.

[0019] Preferred embodiment.

[0020] A key phenomenon was observed during the experiment: when clothing is damp, due to the high dielectric constant of water, the electromagnetic waves from millimeter-wave radar penetrate to a shallow depth. The echo signal mainly originates from the abrupt change in the medium between the clothing surface and the air. At this time, the equivalent scattering center is stable, and the target distance value calculated by the radar exhibits low variance and high stability. As the drying process progresses, the moisture content of the clothing decreases, and the penetration depth of the electromagnetic waves increases. At this point, the echo signal is composed of scattering from multiple layers of fibers within the clothing, forming a volume scattering effect. Due to the mechanical movement of the drum causing continuous changes in the clothing's posture, the interference and superposition of these internal scattering points cause the equivalent scattering center to drift rapidly in the radial direction, resulting in the distance value calculated by the radar exhibiting high variance and low stability. Based on this, this scheme proposes a method for determining the drying endpoint based on distance fluctuation analysis. By calculating the variance or standard deviation of the distance sequence per unit time, when the statistic is detected to jump from a low value region to a high value region and remain there for more than a preset time threshold, it can be determined that the clothing is basically dry. Compared with traditional temperature and humidity detection, this method has the advantages of clear physical mechanism, strong anti-interference ability and no need for complicated calibration.

[0021] like Figure 1 As shown, this invention discloses a millimeter-wave radar algorithm suitable for determining the dryness of clothes in a dryer, comprising the following steps: Step S1: Use FMCW millimeter-wave radar to collect echo signals of underwear in the dryer and calculate the target distance sequence; In step S1, the FMCW millimeter-wave radar transmits a continuous wave with a linearly changing frequency during the frequency sweep period. The echo reflected by the object has a certain frequency difference from the transmitted signal. The distance information between the target and the radar is obtained by measuring the frequency difference. Specifically, this is implemented as follows (e.g., Figure 2 As shown, using sawtooth frequency-modulated continuous wave as an example, we can briefly introduce the ranging principle of radar. Let the transmitted signal frequency (green) be Tx, the received signal frequency (red) be Rx, and the frequency sweep period be... The sweep bandwidth is The transmitted signal passes through the target, and the echo signal has a delay. During the sawtooth-shaped frequency variation, frequency measurements are performed on both the rising and falling edges. The formula is: ; The delay between signal transmission and reception. , The distance from the target to the radar. Since the speed of light is given, the formula for calculating the target distance is: ; The transmitted signal of an FMCW millimeter-wave radar is a sine wave with a linearly varying frequency. Expressed mathematically, the transmitted signal of an FMCW millimeter-wave radar is: ; in, The strength of the transmitted signal, For frequency modulation slope, The initial phase of the transmitted signal, at any time It can be expressed as , The number of modulation periods; When the transmitted signal hits a range radar The speed of movement is After reaching the target, the signal delay after reflection by the target and reception by the radar is: ; The echo signal is: ; The signal received by the radar is amplified and mixed with the local oscillator signal (in our radar, this local oscillator signal is the transmitted signal) to obtain the intermediate frequency signal: ; After removing the smallest terms, the intermediate frequency signal is approximately: ; in The beat frequency contains distance information, with a distance resolution of [missing information]. , For bandwidth; The frequency is the Doppler frequency, which contains the target's velocity information, with a velocity resolution of [missing value]. (If FMCW is simply used for ranging, the Doppler frequency) Compared to Since the impact is relatively small and can be ignored, the beat frequency is obtained by sampling and calculating the intermediate frequency signal. That is, to calculate the distance to the target: .

[0022] Example: carrier frequency ,bandwidth Distance to Target 1 The speed of movement is Distance to target 2 The speed of movement is .by The intermediate frequency signal is sampled at a sampling frequency of 128 points, ignoring signal amplitude and phase. IQ sampling signal (MATLAB code): ; ; in The number of modulation periods. When , , The waveforms of the IQ signals are as follows: Figure 3 As shown in the figure, relatively Lag / 2.

[0023] In practical calculations, the Fast Fourier Transform (FFT) is typically used to calculate the signal spectrum. Here, the spectrum refinement algorithm CZT is used to calculate the signal spectrum and obtain the distance to the moving target. Compared to FFT, CZT has the advantage of allowing the study of only any frequency band within the FFT frequency range, facilitating narrowband high-resolution analysis. A comparison of FFT and CZT calculations is as follows: By analyzing the above Time signal and The waveforms of amplitude spectra SPI, SPQ, and SPIQ were obtained by performing FFT respectively, as shown below. Figure 4 As shown.

[0024] The target distance is calculated based on the spectrum after FFT transformation: ; ; By analyzing the above Time signal and The waveforms of amplitude spectra SPI, SPQ, and SPIQ obtained by performing CZT respectively are as follows: Figure 5 As shown in the figure. The selected frequency range is from 0Hz to 50kHz.

[0025] The target distance is calculated based on the spectrum after CZT transformation: ; ; The results above show that the target distance calculated by CZT is closer to the actual set value.

[0026] Step S2: Calculate the variance or standard deviation of the target distance sequence using a time window, specifically: Step S2.1: Set a fixed-length time window of N=2000, corresponding to approximately 20 seconds of data, with a radar refresh rate of 100. Hz Create a storage array Buffer [ N Used to temporarily store data for the current time window, defining a counter. count =0; Step S2.2: In each ranging cycle, obtain the current target distance value. d : buffer [ count ]= d ; count = count +1; Step S2.3: When count = M When the buffer is full of 2000 data points, statistical calculations are triggered.

[0027] Step S2.4: Let the distance sequence within the current time window be: d 1, d 2, d 3,..., d M ( M =2000); Calculate the mean : ; Calculate variance : .

[0028] Step S3: Determine the dryness or wetness of the clothing based on the range of variance or standard deviation values.

[0029] In step S3, the logic for determining whether a substance is dry or wet is as follows: If the variance or standard deviation is below threshold A (the value is very small), the clothes are determined to be damp, and drying continues. If the variance or standard deviation is higher than the threshold B (the value begins to increase sharply), it is determined that the clothes are starting to dry and have entered the semi-drying state. If the variance or standard deviation remains high (and the mean may increase (because the signal penetrates deeper)) and exceeds the preset time threshold, it is determined that the clothes are completely dry and the dryer is stopped.

[0030] Preferably, when the clothing is damp, the high dielectric constant of the moisture causes the millimeter wave to penetrate shallowly and the echo to be stable, resulting in a target range sequence with low variance and high stability; when the clothing is dry, the increased penetration depth of the millimeter wave leads to a volume scattering effect, resulting in a target range sequence with high variance and low stability.

[0031] The distance and amplitude of targets detected by millimeter-wave radar during the process of different clothes changing from wet to dry in a dryer were recorded as follows: Figure 6 As shown, extracting distance and amplitude features can help distinguish between dry and wet clothing.

[0032] It is worth mentioning that the technical features of the dryer, FMCW millimeter-wave radar and other technologies involved in this patent application should be regarded as prior art. The specific structure, working principle and possible control methods and spatial arrangement of these technical features can be adopted using conventional choices in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0033] For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A millimeter wave radar algorithm suitable for a dryer to determine dryness of laundry, characterized by, Includes the following steps: Step S1: Use FMCW millimeter-wave radar to collect echo signals of underwear in the dryer and calculate the target distance sequence; Step S2: Calculate the variance or standard deviation of the target distance sequence using a time window; Step S3: Determine the dryness or wetness of the clothing based on the range of variance or standard deviation values.

2. The millimeter wave radar algorithm for determining the dryness of laundry in a dryer according to claim 1, characterized in that, In step S1, the FMCW millimeter-wave radar transmits a continuous wave with a linearly changing frequency during the frequency sweep period. The echo reflected by the object has a certain frequency difference from the transmitted signal. The distance information between the target and the radar is obtained by measuring the frequency difference. Specifically, the implementation is as follows: Let the transmit signal frequency be Tx, the receive signal frequency be Rx, the sweep period be , and the sweep bandwidth be . The transmit signal is transmitted through the target, and the echo signal has a delay. In the sawtooth frequency change, the frequency measurement is performed on both rising edges, and the formula is: ; the delay of signal transmission to reception, , the distance of target to radar, the speed of light, thus the target distance calculation formula is: ； The transmitted signal of an FMCW millimeter-wave radar is a sine wave with a linearly varying frequency. Expressed mathematically, the transmitted signal of an FMCW millimeter-wave radar is: ； in, The strength of the transmitted signal, For frequency modulation slope, The initial phase of the transmitted signal, at any time It can be expressed as , The number of modulation periods; When the transmitted signal hits a range radar The speed of movement is After reaching the target, the signal delay after reflection by the target and reception by the radar is: ； The echo signal is: ； The signal received by the radar is amplified through a series of steps and then mixed with the local oscillator signal to obtain the intermediate frequency signal. ； After removing the smallest terms, the intermediate frequency signal is approximately: ； in The beat frequency contains distance information, with a distance resolution of [missing information]. , For bandwidth; The frequency is the Doppler frequency, which contains the target's velocity information, with a velocity resolution of [missing value]. That is, to calculate the distance to the target: .

3. The millimeter wave radar algorithm for determining the dryness of laundry in a dryer according to claim 2, characterized in that, In step S3, the logic for determining whether a substance is dry or wet is as follows: If the variance or standard deviation is below threshold A, the clothes are determined to be damp, and drying continues. If the variance or standard deviation is higher than the threshold B, it is determined that the clothes have begun to dry and have entered the semi-drying state. If the variance or standard deviation remains high and exceeds a preset time threshold, the clothes are determined to be completely dry, and the dryer is stopped.

4. The millimeter wave radar algorithm for determining the dryness of laundry in a dryer according to claim 1, wherein, When clothing is damp, the high dielectric constant of moisture causes millimeter waves to penetrate shallowly and the echo to be stable, resulting in a target range sequence with low variance and high stability. When clothing is dry, the increased penetration depth of millimeter waves leads to volume scattering, resulting in a target range sequence with high variance and low stability.

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