A frequency conversion control method and system based on millimeter wave radar human perception

Abstract

The application provides a variable frequency control method and system based on millimeter wave radar human perception, belonging to the technical field of air water production, to solve the problem that the existing air water production machine cannot simultaneously achieve indoor noise reduction and efficient water production. The method collects indoor echo signals through the millimeter wave radar deployed on the equipment, extracts the radar scattering cross-section value and the micro-Doppler feature caused by breathing and heartbeat, judges the presence of human based on the combination of the two, and directly dynamically adjusts the compressor operating frequency and fan speed accordingly, to realize water production at maximum efficiency when there is no one, and automatic speed reduction to silent operation with noise lower than 40 decibels when there is someone. The method fundamentally solves the long-term contradiction between the water production efficiency of the variable frequency air water production machine and indoor noise reduction, and realizes all-weather, dead-angle-free and non-inductive switching control.

Description

Technical Field

[0001] This application belongs to the field of air-to-water technology, specifically relating to a frequency conversion control method and system based on millimeter-wave radar human perception. Background Technology

[0002] An air-to-water generator is a device that extracts moisture from the air. Its basic principle is to condense water vapor in the air into liquid water using a refrigeration system. However, air-to-water generators face a long-standing technical dilemma in practical household applications: the conflict between water production efficiency and operating noise. Specifically, the higher the compressor frequency and the faster the fan speed, the stronger the water production capacity, but the louder the noise. Conversely, reducing the frequency and speed reduces noise but significantly sacrifices water production efficiency. For household environments such as bedrooms and living rooms, users want a sufficient supply of water in a short time while ensuring the device's operation does not interfere with normal life and rest.

[0003] To address the aforementioned contradictions, existing technologies primarily attempt to address them from the following directions. First, passive noise reduction technology employs physical means such as sound insulation cotton, soundproof covers, and vibration damping pads to reduce noise propagation. While this technology has some effect, it has significant drawbacks, including increased equipment cost and size, reduced heat dissipation efficiency, and limited noise reduction (typically only reducing noise by three to five decibels). Furthermore, it cannot fundamentally resolve the inherent contradiction between high-efficiency water production and low noise. Second, fixed-time mode switching is used, with some devices offering timed switching between a high-efficiency daytime mode and a silent nighttime mode. However, this mode cannot adapt to users' actual activity patterns, potentially resulting in the device running at high speed and generating noise when users are resting at home during the day, or running at low speed at night when no one is present, leading to insufficient water production. Third, infrared human body sensing technology is being explored, with some solutions attempting to apply infrared pyroelectric sensors to air-to-water generators to detect the presence of people and adjust the operating status accordingly. However, infrared sensing technology has serious limitations in indoor environments. It is greatly affected by lighting conditions, and direct sunlight or high temperature environments can cause it to malfunction completely. It is also affected by dust and smog, and it cannot penetrate any opaque objects such as clothing and furniture. There are many blind spots in detection, and it cannot detect stationary people such as sleeping people, causing the device to run at high speed and generate noise when the user is stationary.

[0004] Therefore, there is an urgent need for a human body sensing frequency conversion control method that can reliably detect stationary human bodies, penetrate obstacles, and is unaffected by light and temperature in complex indoor environments. Summary of the Invention

[0005] In view of this, this application provides a variable frequency control method and system based on millimeter-wave radar human perception to solve the problem that existing air-to-water generators cannot simultaneously achieve indoor noise reduction and high-efficiency water production.

[0006] To solve the above problems, the technical solution adopted in this application is as follows: Firstly, this application proposes a variable frequency control method based on millimeter-wave radar human body perception, comprising the following steps: Step 1: Collecting radar echo signals of targets within a predetermined detection range using at least one millimeter-wave radar sensor installed on the air-to-water generator; Step 2: Extracting the RCS value and micro-Doppler features of the target from the radar echo signals, and determining whether a human body exists within the predetermined detection range based on the joint judgment of the RCS value and micro-Doppler features; wherein, the micro-Doppler features include the periodic undulation frequency of the chest cavity caused by human respiration and the frequency of minute vibrations on the body surface caused by heartbeat; Step 3: Based on the determination result of the presence of a human body, combined with ambient temperature data, dynamically adjusting the compressor operating frequency and fan speed of the air-to-water generator, so that the air-to-water generator operates at maximum water production efficiency when unattended and operates in a noise reduction mode when present.

[0007] Furthermore, the joint judgment based on RCS value and micro-Doppler features in step 2 includes: when the RCS value is within the preset human RCS range and the micro-Doppler features conform to human vital signs, it is determined that a human body exists; when the RCS value exceeds the preset human RCS range, or the micro-Doppler features do not conform to human vital signs, it is determined that a human body does not exist.

[0008] Furthermore, the preset human RCS range is -8 dBsm to -3 dBsm; when the micro-Doppler characteristics conform to human vital signs, the respiratory rate is in the corresponding frequency band of 12-20 breaths / min and the heart rate is in the corresponding frequency band of 60-100 beats / min.

[0009] Furthermore, in step 1, there are three millimeter-wave radar sensors, which are respectively installed on the front and both sides of the air-to-water generator. The horizontal and vertical coverage angles of the millimeter-wave radar sensors are both 270°. The three millimeter-wave radar sensors overlap in space through fan-shaped beams, and the overlapping areas of adjacent beam edges in the horizontal direction form complementary coverage. The total effective coverage range after the overlap is 320° in the horizontal direction.

[0010] Furthermore, the dynamic adjustment in step 3 includes: if it is determined that there is no human body, the compressor operates according to the maximum compressor frequency and the highest fan speed allowed by the ambient temperature data to ensure the maximum water production; if it is determined that there is a human body, the compressor operating frequency is uniformly adjusted to the first preset frequency value and the fan speed is uniformly adjusted to the first preset speed value to ensure that the equipment operating noise is below 40dB.

[0011] Furthermore, the first preset frequency value is 60% of the maximum frequency value, and the first preset rotational speed value is 23% of the maximum rotational speed value.

[0012] Secondly, this application proposes a system for the variable frequency control method based on millimeter-wave radar human perception described in the first aspect, comprising: a sensing module, including at least one millimeter-wave radar sensor mounted on an air-to-water generator, for collecting radar echo signals of targets within a predetermined detection range; a control processing module, communicatively connected to the sensing module, for extracting the radar cross section value and micro-Doppler characteristics of the target from the radar echo signals, determining whether a human body exists within the predetermined detection range based on a joint judgment of the radar cross section value and micro-Doppler characteristics, and directly generating compressor frequency adjustment commands and fan speed adjustment commands based on the human body presence determination result combined with ambient temperature data; and an execution module, for receiving the adjustment commands and executing corresponding actions, so that the air-to-water generator operates at maximum water production efficiency in an unmanned state and operates in a noise reduction mode in a manned state.

[0013] Furthermore, the control processing module includes: an RCS value extraction unit for extracting the RCS value of the target from the radar echo signal; a micro-Doppler feature extraction unit for extracting micro-Doppler features caused by human breathing and heartbeat from the radar echo signal; a joint judgment unit for determining the presence of a human body when the RCS value is in the range of -8 dBsm to -3 dBsm and the micro-Doppler features match human vital signs; and a control unit for generating adjustment commands based on the maximum compressor frequency and maximum fan speed allowed by the ambient temperature data when no human body is determined to be present, and generating commands to adjust the compressor operating frequency to a first preset frequency value and the fan speed to a first preset speed value when a human body is determined to be present, to ensure that the equipment operating noise is below 40 dB.

[0014] Furthermore, the execution module includes a variable frequency compressor and a variable frequency fan. The variable frequency compressor is configured to adjust its operating frequency according to the compressor frequency adjustment command output by the control unit, and the variable frequency fan is configured to adjust its speed according to the fan speed adjustment command output by the control unit.

[0015] Furthermore, the sensing module includes three 77GHz millimeter-wave radar sensors, which are respectively located on the front and sides of the air-to-water generator.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of this application are: This application achieves an automatic balance between maximum water production efficiency in unmanned mode and noise levels below 40dB in manned mode, requiring no manual user intervention and significantly improving the user experience in home indoor environments. Through the overlapping layout of three millimeter-wave radars, effective coverage of 320° horizontally and vertically is achieved, with blind spots only in the area behind the wall, essentially eliminating detection blind spots found in traditional infrared solutions. Signal processing techniques such as multi-frame accumulation, constant false alarm rate (CFAR) detection, and adaptive clutter cancellation effectively suppress indoor multipath interference and static clutter, improving detection reliability. The integrated design of the control and processing module simplifies the system architecture and reduces hardware costs and failure rates.

[0017] The millimeter-wave radar's penetration detection capability synergizes with the typical indoor wall-mounted installation scenario of the air-to-water generator, solving the problem of traditional line-of-sight sensors failing due to furniture obstruction. The joint judgment of static radar cross-section characteristics and micro-Doppler dynamic characteristics works synergistically; the former filters out interference from highly reflective objects like metal plates and low-reflective objects like wood panels and paper, while the latter eliminates false targets such as human models. This complementary verification minimizes false alarm and false negative rates. Human presence sensing synergizes with the closed-loop control of the frequency converter, transforming detection results from mere status indications into direct equipment operating parameters, achieving zero-delay conversion from information to action. The spatial diversity of the three radars synergizes with the multi-radar data fusion of the signal processing auxiliary unit. Through beam cross-overlap and complementary coverage, the detection range is expanded, and the impact of single-radar multipath fading is reduced through data fusion. Ambient temperature compensation and a dual-mode control strategy work synergistically; during deceleration and noise reduction, the minimum feasible operating frequency is determined based on ambient temperature, preventing excessive deceleration from causing a complete loss of water production capacity. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 A schematic diagram of the structure of the frequency conversion control system based on millimeter-wave radar human perception provided in an embodiment of this application; Figure 2 This is a block diagram of a frequency conversion control system based on millimeter-wave radar human perception provided in an embodiment of this application; Figure 3 This is a schematic diagram of the frequency conversion control method based on millimeter-wave radar human perception provided in the embodiments of this application.

[0019] Among them, 10 is the sensing module; 100 is the millimeter-wave radar sensor; and 110 is the signal line. 20. Control and processing module; 210. RCS numerical extraction unit; 220. Micro-Doppler feature extraction unit; 230. Joint judgment unit; 240. Control unit; 30. Execution module; 310. Variable frequency compressor; 320. Variable frequency fan. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The components of the embodiments of this application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0023] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] In this application, unless otherwise expressly specified and limited, "above" or "below" a second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of a second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" a second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and do not limit the number of objects; for example, a first object can be one or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0025] Existing air-to-water generators are devices that extract moisture from the air. Their basic principle is to condense water vapor in the air into liquid water using a refrigeration system. However, air-to-water generators face a long-standing technical contradiction in practical household applications: the conflict between water production efficiency and operating noise. Specifically, the higher the compressor operating frequency and the faster the fan speed, the stronger the water production capacity, but the greater the noise; conversely, reducing the frequency and speed reduces noise but significantly sacrifices water production efficiency. For household indoor environments such as bedrooms and living rooms, users want to obtain sufficient water production in a short time while ensuring the device does not interfere with normal life and rest. To resolve this contradiction, existing technologies mainly attempt to address the following issues. Firstly, passive noise reduction technology uses physical means such as sound insulation cotton, soundproof covers, and vibration damping pads to reduce noise transmission. While this technology has some effect, it has significant drawbacks, including increased equipment cost and size, reduced heat dissipation efficiency, and limited noise reduction effect (typically only reducing noise by three to five decibels). Furthermore, it cannot fundamentally resolve the inherent contradiction between high-efficiency water production and low noise. Secondly, there's the issue of fixed-time mode switching. Some devices offer a timed switching function between a high-efficiency daytime mode and a silent nighttime mode. However, this mode cannot adapt to users' actual activity patterns. It may result in the device running at high speed and generating noise when users are resting at home during the day, or running at low speed and producing insufficient water at night when no one is around. Thirdly, there's infrared human body sensing technology. Some solutions attempt to apply infrared pyroelectric sensors to air-to-water generators to detect the presence of people and adjust the operating status accordingly. However, infrared sensing technology has serious limitations in indoor environments. It is greatly affected by lighting conditions; direct sunlight or high temperatures can cause it to completely malfunction. It is also affected by dust and smog, and cannot penetrate any opaque objects such as clothing and furniture, resulting in numerous detection blind spots. Furthermore, it cannot detect stationary people, such as sleeping individuals, causing the device to continue running at high speed and generating noise even when the user is stationary.

[0026] This application integrates the human body detection capabilities of millimeter-wave radar with the actuators of a variable frequency air-to-water generator to construct a noise reduction control system with a closed-loop perception and execution mechanism. Specifically, millimeter-wave radar sensors deployed on the air-to-water generator collect radar echo signals from indoor targets. Two complementary pieces of information are simultaneously extracted from the echo signals: radar cross-section values ​​and micro-Doppler characteristics. Static radar cross-section characteristics are used to distinguish the material differences between the human body and common indoor objects, while dynamic micro-Doppler characteristics are used to confirm the unique respiratory and cardiac vital signs of the human body. The combined judgment of these two factors achieves highly reliable detection of human presence, and based on this, directly generates adjustment commands for the compressor frequency and fan speed. This allows the air-to-water generator to produce water at maximum efficiency when unoccupied and automatically switch to silent mode when someone is present, thus fundamentally resolving the long-standing contradiction between water production efficiency and operating noise.

[0027] Existing technologies primarily rely on infrared pyroelectric sensors for human detection, which are greatly affected by light, temperature, and dust, cannot penetrate obstacles, and cannot detect stationary human bodies, resulting in extremely high false alarm and false negative rates in indoor environments. This application employs millimeter-wave radar technology, utilizing its ability to penetrate common indoor items such as clothing, plastic, glass, and wood, as well as its ability to detect micro-Doppler characteristics of breathing and heartbeat, achieving all-weather, all-posture, and blind-spot-free human presence detection. Existing technologies lack radar cross-section differentiation standards for indoor environments and do not jointly verify static reflection characteristics with dynamic vital signs. This application establishes a multi-dimensional differentiation mechanism between human bodies and indoor items such as electrical appliances, ceramics, glass, wood, and paper by calibrating the human body radar cross-section range and integrating micro-Doppler spectrum analysis. Existing variable frequency air-to-water generators' control logic is based on temperature feedback or fixed-time modes, unable to dynamically adjust according to the real-time presence of people. This application directly maps human detection results to specific control parameters for compressor frequency and fan speed, achieving a millisecond-level closed-loop response from perception to execution.

[0028] The following is in conjunction with the appendix Figures 1 to 3 The technical solutions provided in this application will be described in detail through specific embodiments and application scenarios.

[0029] Example 1

[0030] like Figures 1-3As shown, the sensing module 10 includes at least one millimeter-wave radar sensor 100. In this embodiment, three 77GHz millimeter-wave radar sensors are used, installed on the front and sides of the air-to-water generator respectively, and communicated with the control processing module 20 via signal line 110. Each millimeter-wave radar sensor 100 has a horizontal and vertical coverage angle of 270°. The three sensors overlap spatially through fan-shaped beams. The overlapping areas of adjacent beam edges in the horizontal direction form complementary coverage, resulting in a total effective coverage range of 320° in the horizontal direction. Vertical coverage is also achieved through beam overlap. When the air-to-water generator is placed against a wall, the back area is a scanning blind spot, while other directions have virtually no scanning blind spots. The millimeter-wave radar sensor 100 uses a frequency-modulated continuous wave system, transmitting a continuous wave with a frequency that changes linearly with time. The center frequency is 77GHz, the bandwidth is 4GHz, and the speed resolution depends on the coherent accumulation time. The radar echo signal is captured by the receiving antenna after being reflected by the target. After being mixed with the transmitted signal, an intermediate frequency (IF) signal is generated. This IF signal contains the target's range, velocity, and phase information. It is transmitted to the control processing module 20 in digital or analog form via signal line 110. The layout design of the three radars fully considers the typical installation scenario of the air-to-water generator. The front radar is responsible for detecting the area directly in front, while the two side radars are responsible for detecting the areas to the left and right front, respectively. The overlapping areas of the three radars enhance the detection reliability, and the non-overlapping areas expand the coverage range, thus forming a complete indoor human body sensing network.

[0031] The control processing module 20, as the core decision-making unit of the system, is communicatively connected to the perception module 10 and is responsible for signal processing, feature extraction, human detection, and control command generation. This module includes a radar cross section (RCS) value extraction unit 210, a micro-Doppler feature extraction unit 220, a joint judgment unit 230, and a control unit 240. The RCS value extraction unit 210 receives intermediate frequency signals from three millimeter-wave radar sensors 100 and calculates the RCS value for each target. The radar cross section (RCS) values ​​of common indoor items exhibit significant differences: The human body, with its high water content (approximately 70%) and dielectric constant of approximately 40-50, has a stable RCS value between -8 and -3 dBsm; electrical and electronic devices, containing numerous metal components, typically have an RCS value between -5 and -10 dBsm; porcelain and ceramic products, with a dielectric constant of approximately 6-10, have an RCS value between -15 and -5 dBsm; glass, with a dielectric constant of approximately 4-6, has an RCS value between -25 and -10 dBsm; wooden boards and furniture, with a dielectric constant of approximately 2-3, have an RCS value between -30 and -20 dBsm; and paper and cardboard boxes, with a dielectric constant of approximately 1.5-2, have an RCS value between -35 and -25 dBsm. The RCS value extraction unit 210 compares the calculated RCS values ​​of each target with the preset human body RCS range, filtering out candidate targets within the -8 to -3 dBsm range. The above statistics are shown in Table 1.

[0032] Table 1. RCS range for distinguishing between human bodies and common indoor items in a human presence detection system for variable frequency air-to-water generators.

[0033] The micro-Doppler feature extraction unit 220 simultaneously receives intermediate frequency signals from three millimeter-wave radar sensors 100, focusing on extracting minute vibration features caused by human vital signs. Since the amplitude of chest cavity rise and fall caused by human respiration is approximately four to twelve millimeters, and the amplitude of body surface vibration caused by heartbeat is approximately 0.1 to 0.5 millimeters, these minute movements produce detectable phase changes. Bandpass filtering is applied to this phase curve, with the respiratory frequency band corresponding to 12-20 breaths / min and the heartbeat frequency band corresponding to 60-100 heartbeats / min.

[0034] The joint judgment unit 230 receives the candidate target radar cross section (RCS) values ​​output by the radar cross section value extraction unit 210 and the vital sign detection results output by the micro-Doppler feature extraction unit 220, and performs a comprehensive judgment. The logic of the joint judgment is as follows: if and only if the target's RCS value is in the range of -8 to -3 dBsm, and the micro-Doppler features simultaneously contain periodic components of a respiratory rate in the frequency band corresponding to 12-20 breaths / min and a heart rate in the frequency band corresponding to 60-100 beats / min, then a human body is determined to exist. If the target's RCS value exceeds the above range, or if either the respiratory rate or heart rate in the micro-Doppler features does not conform to the physiological range of the human body, then a human body is determined not to exist. This joint judgment mechanism fully utilizes the complementarity of static RCS features and dynamic micro-Doppler features: RCS features can effectively distinguish targets of different materials and sizes, but cannot distinguish between a human body and a human body model with the same RCS; micro-Doppler features can confirm the existence of living beings, but may miss detections when the signal-to-noise ratio is low. Combining the two can minimize false alarm and false negative rates, enabling highly reliable detection of human presence in complex indoor environments.

[0035] The control unit 240 receives the human presence determination result output by the joint judgment unit 230, and simultaneously receives ambient temperature data collected by the ambient temperature sensor, generating compressor frequency adjustment commands and fan speed adjustment commands. When no human presence is determined, the control unit 240 queries a preset temperature-frequency mapping table based on the ambient temperature data to determine the maximum compressor frequency and maximum fan speed allowed by the current ambient temperature, generating corresponding adjustment commands to enable the air-to-water generator to operate at maximum water production efficiency. When a human presence is determined, the control unit 240 generates frequency and speed reduction commands, uniformly adjusting the compressor operating frequency to a first preset frequency value and the fan speed to a first preset speed value. In this embodiment, the first preset frequency value is 60% of the maximum frequency value, and the first preset speed value is 23% of the maximum speed value. Under these operating parameters, the equipment noise can be lower than 40dB.

[0036] The execution module 30 includes a variable frequency compressor 310 and a variable frequency fan 320. It receives adjustment commands output by the control unit 240 and executes corresponding actions. The variable frequency compressor 310 uses variable frequency drive technology, changing its operating frequency according to the compressor frequency adjustment command. The frequency adjustment range is from zero to the maximum frequency. In this embodiment, the maximum frequency corresponds to 500 analog units, and the operating frequency in occupant mode is 300 analog units. The variable frequency fan 320 also uses variable frequency drive, changing its speed according to the fan speed adjustment command. The speed adjustment range is from zero to the maximum speed. In this embodiment, the maximum speed corresponds to 1000 analog units, and the operating speed in occupant mode is 230 analog units. The coordinated operation of the variable frequency compressor 310 and the variable frequency fan 320 ensures the coordinated operation of the refrigeration system. The variable frequency compressor 310 is responsible for providing cooling capacity to condense water vapor in the air, while the variable frequency fan 320 is responsible for driving airflow to improve heat exchange efficiency. In unmanned mode, both operate at maximum efficiency to achieve maximum water production; in manned mode, both reduce speed simultaneously to maintain basic water production capacity while keeping noise levels within a comfortable range.

[0037] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0038] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0039] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0040] Furthermore, it should be noted that the scope of the methods and apparatus in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

Claims

1. A frequency conversion control method based on millimeter-wave radar human perception, characterized in that, Includes the following steps: Step 1: Collect radar echo signals of targets within a predetermined detection range using at least one millimeter-wave radar sensor (100) installed on the air-to-water generator; Step 2: Extract the RCS value and micro-Doppler features of the target from the radar echo signal. Based on the joint judgment of the RCS value and micro-Doppler features, determine whether there is a human body within the predetermined detection range. The micro-Doppler features include the periodic undulation frequency of the chest cavity caused by human respiration and the frequency of minute vibrations on the body surface caused by heartbeat. Step 3: Based on the determination of the presence of a human body and combined with the ambient temperature data, dynamically adjust the compressor operating frequency and fan speed of the air-to-water generator so that the air-to-water generator operates at maximum water production efficiency when no one is present and operates in a noise reduction mode when someone is present.

2. The frequency conversion control method based on millimeter-wave radar human perception according to claim 1, characterized in that, The joint judgment based on RCS value and micro-Doppler features in step 2 includes: When the RCS value is within the preset human RCS range and the micro-Doppler feature matches the characteristics of human vital signs, it is determined that a human body is present. When the RCS value exceeds the preset human body RCS range, or when the micro-Doppler feature does not conform to the characteristics of human vital signs, it is determined that there is no human body.

3. The frequency conversion control method based on millimeter-wave radar human perception according to claim 2, characterized in that, The preset human body RCS range is -8 dBsm to -3 dBsm; When the micro-Doppler characteristics match the characteristics of human vital signs, the respiratory rate is in the corresponding frequency band of 12-20 breaths / min and the heart rate is in the corresponding frequency band of 60-100 beats / min.

4. The frequency conversion control method based on millimeter-wave radar human perception according to claim 1, characterized in that, In step 1, there are three millimeter-wave radar sensors (100), which are installed on the front and sides of the air-to-water generator respectively. The horizontal and vertical coverage angles of the millimeter-wave radar sensors (100) are both 270°. The three millimeter-wave radar sensors (100) overlap in space through fan-shaped beams, and the overlapping areas of adjacent beam edges in the horizontal direction form complementary coverage. The total effective coverage range after the cross-overlap is 320° in the horizontal direction.

5. The frequency conversion control method based on millimeter-wave radar human perception according to any one of claims 1-4, characterized in that, The dynamic adjustment mentioned in step 3 includes: If it is determined that there is no human body, the compressor will operate according to the maximum compressor frequency and the highest fan speed allowed by the ambient temperature data to ensure the maximum water production. If a human body is detected, the compressor operating frequency and the fan speed will be uniformly adjusted to the first preset frequency value and the fan speed will be uniformly adjusted to the first preset speed value to ensure that the equipment operating noise is below 40dB.

6. The frequency conversion control method based on millimeter-wave radar human perception according to claim 5, characterized in that, The first preset frequency value is 60% of the maximum frequency value, and the first preset speed value is 23% of the maximum speed value.

7. A system applied to the frequency conversion control method based on millimeter-wave radar human perception as described in any one of claims 1-6, characterized in that, include: The sensing module (10) includes at least one millimeter-wave radar sensor (100) mounted on the air-to-water generator, used to collect radar echo signals of targets within a predetermined detection range; The control processing module (20) is communicatively connected to the sensing module (10) and is used to extract the radar cross section value and micro-Doppler characteristics of the target from the radar echo signal. Based on the joint judgment of the radar cross section value and micro-Doppler characteristics, it determines whether there is a human body in the predetermined detection range, and directly generates compressor frequency adjustment command and fan speed adjustment command based on the human body existence determination result and ambient temperature data. The execution module (30) is used to receive the adjustment command and perform the corresponding action, so that the air-to-water generator operates at maximum water production efficiency when no one is present and operates in a noise reduction mode when someone is present.

8. The system according to claim 7, characterized in that, The control processing module (20) includes: RCS value extraction unit (210) is used to extract the RCS value of the target from the radar echo signal; A micro-Doppler feature extraction unit (220) is used to extract micro-Doppler features caused by human breathing and heartbeat from radar echo signals; The joint judgment unit (230) is used to determine the presence of a human body when the RCS value is in the range of -8 dBsm to -3 dBsm and the micro-Doppler feature is consistent with the human vital signs. The control unit (240) is used to generate adjustment commands based on the maximum compressor frequency and the maximum fan speed allowed by the ambient temperature data when it is determined that no human body is present, and to generate commands to adjust the compressor operating frequency to a first preset frequency value and the fan speed to a first preset speed value when it is determined that a human body is present, so as to ensure that the equipment operating noise is below 40dB.

9. The system according to claim 8, characterized in that, The execution module (30) includes a variable frequency compressor (310) and a variable frequency fan (320). The variable frequency compressor (310) is configured to adjust the operating frequency according to the compressor frequency adjustment command output by the control unit (240), and the variable frequency fan (320) is configured to adjust the speed according to the fan speed adjustment command output by the control unit (240).

10. The system according to any one of claims 7-9, characterized in that, The sensing module (10) includes three 77GHz millimeter-wave radar sensors (100), which are respectively located on the front and sides of the air-to-water generator.

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