Unmanned aerial vehicle radar, unmanned aerial vehicle, and unmanned aerial vehicle radar control method

Abstract

The application provides a UAV radar, a UAV and a UAV radar control method, the UAV radar comprising a measurement host, a monopole beam antenna group, a wide-beam transmitting antenna, a wide-beam receiving antenna, a narrow-beam transmitting antenna and a narrow-beam receiving antenna. The narrow-beam antenna has a narrow beam, and the distance between the UAV and the ground can be measured accurately. The wide-beam antenna has a wide beam, and the measurement range is wide, which can assist in measuring whether there is an obstacle below the UAV, so that the UAV can avoid the obstacle below when the terrain changes. The monopole beam antenna group has the widest beam, and when the terrain is steep, the obstacle on the side and below can be quickly measured, so that the UAV can quickly avoid the obstacle or stop. In this way, the UAV radar has rich functions, is suitable for various states such as UAV ascending, descending, hovering and ground following, the measurement result is accurate, and the UAV radar does not need to use a rotating radar, has high structural stability and a long service life.

Description

Technical Field

[0001] This invention belongs to the field of radar technology, and more specifically, relates to a UAV radar, a UAV, and a UAV radar control method. Background Technology

[0002] With the development of science and technology and the improvement of scientific and technological levels in my country, drones are being used more and more widely in various fields. In the drone industry, the complex environment causes many uncertainties in drone flight. To ensure stable flight, radar needs to be installed beneath the drone to enable it to perceive its environment. The radar beneath the drone plays a crucial role in the drone's terrain following, altitude measurement, stable hovering, and obstacle avoidance functions. Therefore, the radar beneath the drone is a vital component for stable flight. The design and installation of the radar beneath the drone is currently a key focus and also a major challenge in drone design. Compared to lidar and ultrasonic radar, millimeter-wave radar has the inherent advantage of being unaffected by weather and environmental interference. Furthermore, millimeter-wave radar is easy to integrate, small in size, and low in cost, easily meeting the needs of drones to provide stable measurement data in changing environments.

[0003] Currently, the two most commonly used radars are as follows:

[0004] 1. The NRA15 altimeter radar from Nare Technology has a major drawback: its single-beam radiation range is narrow and its functionality is limited. In reality, a single beam is insufficient for applications in complex environments. When encountering two obstacles with a significant distance between them, the insufficient beamwidth and number of beams often lead to inadequate terrain awareness and an inability to make advance judgments.

[0005] 2. Phased Array Digital Radar. This radar is the bottom-mounted radar used in DJI drones. The specific implementation of this bottom-mounted radar measurement method utilizes mechanical scanning. A motor rotates the radar board periodically at a certain speed, achieving 360-degree target detection. It receives data from all directions and fuses the data to achieve altitude hold and terrain following capabilities. The main drawbacks are: due to the motor's 360-degree rotation, the radar refresh rate is not high, and it cannot quickly detect obstacles in all directions around the drone. Consequently, the radar's radiation time in a specific direction is very short, and the radar's radiation time in a specific direction is directly proportional to its detection capability. Furthermore, the mechanical high-speed rotation limits the radar's lifespan and affects its stability. It cannot adjust the detection direction according to the drone's tilt, limiting its applicability. Summary of the Invention

[0006] The purpose of this invention is to provide a UAV radar, a UAV, and a UAV radar control method to solve the technical problems existing in the prior art, such as the limited function of altimeter radar, the low detection capability of phased array digital radar for specific azimuth, and the short service life.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a UAV radar, comprising:

[0008] A monopole beam antenna array is used to measure the distance between the UAV and obstacles and to measure the echo angle of the echo signal to provide obstacle avoidance information. The beamwidth of the monopole beam antenna array is greater than 85°.

[0009] Wide-beam transmitting antenna, used to transmit beams with a width greater than 25° and less than 80°;

[0010] A wide-beam receiving antenna is used to receive the beam emitted by the wide-beam transmitting antenna;

[0011] Narrow beam transmitting antenna, used to transmit beams with a width of less than 25°;

[0012] A narrow beam receiving antenna is used to receive the beam emitted by the narrow beam transmitting antenna;

[0013] The measurement host is used to process the transmitted and received beams of the antenna, and the measurement host has a control switch that enables the transmitting antenna, the wide-beam transmitting antenna and the narrow-beam transmitting antenna in the monopole antenna group to operate selectively;

[0014] The wide-beam transmitting antenna and the wide-beam receiving antenna are used to measure the distance between the UAV and obstacles to determine whether the UAV needs to avoid obstacles; the narrow-beam transmitting antenna and the narrow-beam receiving antenna are used to measure the distance between the UAV and the ground.

[0015] Optionally, the monopole beam antenna group includes a first transmitting monopole antenna, a second transmitting monopole antenna, a first receiving monopole antenna, and a second receiving monopole antenna. The line connecting the first transmitting monopole antenna and the second transmitting monopole antenna is a first reference line, and the line connecting the first receiving monopole antenna and the second receiving monopole antenna is a second reference line. The first reference line and the second reference line are set at an angle. The transmitted beam of the first transmitting monopole antenna or the second transmitting monopole antenna is received by the first receiving monopole antenna and the second receiving monopole antenna to measure the angle between the echo signal and the second reference line. The transmitted beams of the first transmitting monopole antenna and the second transmitting monopole antenna are simultaneously received by the first receiving monopole antenna or the second receiving monopole antenna to measure the angle between the echo signal and the first reference line.

[0016] Optionally, the measurement host includes a signal transmission module and a signal processing module. The signal transmission module includes the control switch, which is a single-pole four-throw switch. The monopole beam antenna group includes a first transmitting monopole antenna, a second transmitting monopole antenna, a first receiving monopole antenna, and a second receiving monopole antenna. The four contacts of the single-pole four-throw switch are respectively connected to the wide-beam transmitting antenna, the narrow-beam transmitting antenna, the first transmitting monopole antenna, and the second transmitting monopole antenna.

[0017] Optionally, the signal transmitting module further includes a signal modulation circuit, a voltage-controlled oscillator, a power divider, and four radio frequency amplifiers connected in sequence. The four radio frequency amplifiers are electrically connected to the wide-beam transmitting antenna, the narrow-beam transmitting antenna, the first transmitting monopole antenna, and the second transmitting monopole antenna, respectively. The power divider and the four radio frequency amplifiers are electrically connected through the single-pole four-throw switch. The voltage-controlled oscillator is driven by the signal modulation circuit, and the power divider is used to transmit the transmitted signal to the radio frequency amplifiers and the signal processing module, respectively.

[0018] Optionally, the signal processing module includes four signal processing units, each of which includes a low-noise amplifier, a mixer, a filter amplifier, and an analog-to-digital converter connected in sequence. The wide-beam receiving antenna, the narrow-beam receiving antenna, the first receiving monopole antenna, and the second receiving monopole antenna are electrically connected to the four low-noise amplifiers, and the mixer is electrically connected to the power divider of the signal transmitting module.

[0019] The present invention also provides a drone, including the aforementioned drone radar.

[0020] The present invention also provides a UAV radar control method for use in the aforementioned UAV radar, the UAV radar control method comprising:

[0021] When the drone hovers or ascends, a control switch activates the narrow-beam transmitting antenna to measure the distance between the drone and the ground.

[0022] When the UAV is horizontally following the terrain, the control switch selectively activates the wide-beam transmitting antenna, the narrow-beam transmitting antenna, and the monopole beam antenna group.

[0023] As the drone descends, the control switch selectively activates the narrow beam transmitting antenna and the transmitting antenna of the monopole beam antenna group.

[0024] Optionally, in the step of selectively operating the wide-beam transmitting antenna, the narrow-beam transmitting antenna, and the monopole beam antenna group when the UAV is horizontally following the terrain, the control switch...

[0025] The narrow-beam transmitting antenna and the narrow-beam receiving antenna measure the distance between the UAV and the obstacle as l1, the wide-beam transmitting antenna and the wide-beam receiving antenna measure the distance between the UAV and the obstacle as l2, the monopole beam antenna group measures the distance between the UAV and the obstacle as l3, and the obstacle avoidance threshold is R.

[0026] When l1 > l2 > R, the UAV ascends.

[0027] When l1 > l2 and l2 < R, or when l1 > l2 and l3 < R, the UAV performs obstacle avoidance or braking.

[0028] Optionally, when the UAV descends, in the step of making the transmitting antennas of the narrow-beam transmitting antenna and the monopole beam antenna group selectively operate by the control switch,

[0029] The narrow-beam transmitting antenna and the narrow-beam receiving antenna measure the distance between the UAV and the obstacle as l1, the monopole beam antenna group measures the distance between the UAV and the obstacle as l3, the obstacle avoidance threshold is R, and when l3 < R, the UAV performs obstacle avoidance or braking.

[0030] Optionally, the step of the UAV performing obstacle avoidance includes: the monopole beam antenna group measures the distance l3 between the UAV and the obstacle and measures the echo angle of the echo signal, and transmits the measured obstacle avoidance data to the emergency braking module of the UAV.

[0031] The beneficial effects of the UAV radar, UAV and UAV radar control method provided by the present invention are as follows: Compared with the prior art, the UAV radar of the present invention includes a measurement host, a monopole beam antenna group, a wide-beam transmitting antenna, a wide-beam receiving antenna, a narrow-beam transmitting antenna and a narrow-beam receiving antenna. The beam widths of the monopole beam antenna group, the wide-beam antenna and the narrow-beam antenna decrease in sequence. The beam of the narrow-beam antenna is narrow, and the measurement of the distance between the UAV and the ground is relatively accurate. Therefore, the angle between the UAV and the ground can be measured in the states of the UAV ascending, descending, hovering, following the ground, etc. The beam of the wide-beam antenna is wide, and the measurement range is wide, which can assist in measuring whether there are obstacles obliquely below the UAV, enabling the UAV to avoid obstacles obliquely below when the terrain changes. The beam of the monopole beam antenna group is the widest. In the case of steep terrain, obstacles on the side and obliquely below can be quickly measured, enabling the UAV to quickly perform obstacle avoidance or braking. Thus, the UAV radar has rich functions, is applicable to various states such as the UAV ascending, descending, hovering, following the ground, etc., the measurement results are relatively accurate, and there is no need to use a rotating radar, and the structural stability is strong and the service life is long. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a structural framework diagram of an unmanned aerial vehicle (UAV) radar provided in an embodiment of the present invention.

[0034] Figure 2 A schematic diagram of the lower beam of a UAV radar provided in an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the structure of each antenna of the UAV radar provided in an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the beam when a drone ascends or hovers, provided in an embodiment of the present invention.

[0037] Figure 5 This is a drone-based map simulation provided by an embodiment of the present invention when the terrain does not trigger the obstacle avoidance threshold;

[0038] Figure 6 This invention provides a UAV map simulation method based on the terrain-triggered obstacle avoidance threshold provided in this embodiment.

[0039] Figure 7 This is a schematic diagram of the beam during the descent of a drone provided in an embodiment of the present invention;

[0040] Figure 8 An internal structural framework diagram of a drone provided in an embodiment of the present invention;

[0041] Figure 9 This is a flowchart illustrating the UAV radar control method provided in an embodiment of the present invention.

[0042] Figure 10 A schematic diagram of the time and frequency domains of a frequency-modulated continuous wave provided in an embodiment of the present invention;

[0043] Figure 11 A frequency-time relationship diagram of the transmitted and received signals provided in an embodiment of the present invention;

[0044] Figure 12 The phase difference-based angle measurement principle provided in this embodiment of the invention;

[0045] Figure 13 This is a schematic diagram of the angle measurement process for a monopole beam antenna group provided in an embodiment of the present invention. Detailed Implementation

[0046] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0047] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0048] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0050] Radar is a core component of unmanned aerial vehicles (UAVs), working in conjunction with the flight control system to enable obstacle avoidance. The radar in this embodiment is a millimeter-wave radar, meaning all antennas in the radar are millimeter-wave antennas. Millimeter-wave radar has the inherent advantage of being unaffected by weather and environmental interference. Furthermore, it is easy to integrate, small in size, and low in cost, readily providing stable measurement data for UAVs in variable environments.

[0051] The drone radar provided in this embodiment of the invention will now be described. The drone radar is installed below the drone and can measure the terrain below the drone for obstacle avoidance.

[0052] Please see Figures 1 to 3 The UAV radar includes a measurement host, a monopole beam antenna group, a wide beam antenna, and a narrow beam antenna.

[0053] The transmitting antenna in a monopole beamforming antenna array transmits the monopole beam, while the receiving antenna receives it. The beamwidth of the monopole beamforming antenna array is greater than 85°, allowing it to measure the presence of obstacles diagonally below the drone. Furthermore, the monopole beamforming antenna array can measure the distance between the drone and obstacles, and also measure the echo angle of the echo signal. The echo angle can be used to calculate the obstacle's position relative to the drone. The echo angle is the beam emitted by the transmitting antenna of the monopole beamforming antenna array, reflected by the obstacle, and received by the receiving antenna. Therefore, the distance and echo angle measured by the monopole beamforming antenna are obstacle avoidance information. Transmitting this obstacle avoidance information to the drone's flight control system prevents the drone from colliding with obstacles.

[0054] The wide-beam antenna includes a wide-beam transmitting antenna (TX2) and a wide-beam receiving antenna (RX2). The beamwidth of the wide-beam antenna is greater than 25° and less than 80°. Specifically, the wide-beam transmitting antenna transmits a beam with a width greater than 25° and less than 80°, and the wide-beam receiving antenna receives the beam transmitted by the wide-beam transmitting antenna. The wide-beam antenna can be used to measure the distance between the drone and obstacles. Because the beam of the wide-beam antenna is relatively wide, it can measure obstacles diagonally below the drone, allowing the drone to pull up in advance to avoid obstacles. In other words, it can provide information on whether obstacle avoidance is necessary.

[0055] A narrow-beam antenna consists of a narrow-beam transmitting antenna (TX1) and a narrow-beam receiving antenna (RX1), with a beamwidth of less than 25°. Specifically, the narrow-beam transmitting antenna transmits a beam with a width of less than 25°, and the narrow-beam receiving antenna receives the beam emitted by the transmitting antenna. Because a narrower beam provides higher ranging accuracy, narrow-beam antennas can be used to measure the distance between a drone and the ground. Here, the ground is defined as objects directly below the drone, and obstacles are defined as objects in the area diagonally below the drone.

[0056] The monopole beam antenna group, wide-beam antenna, and narrow-beam antenna are all located below the UAV, and the center symmetry lines of the beams emitted by the monopole beam antenna group, wide-beam antenna, and narrow-beam antenna are all vertically aligned. In other words, the monopole beam antenna group covers the widest measurement area, followed by the wide-beam antenna, and the narrow-beam antenna covers the smallest.

[0057] It should be noted that the distances between the drone and the ground or obstacles measured by each antenna in this drone radar are the minimum distances of the measured data. This is because there are multiple transmission paths between the drone and the ground or obstacles (such as signal refraction and return), and only the distance corresponding to the shortest transmission path is the actual distance between the drone and the ground or obstacle. The ranging principle of the antennas can be found in the embodiments provided in the drone radar control method, and will not be repeated here.

[0058] The measurement host is used to process the transmitted and received beams of each antenna. The monopole beam antenna group, wide-beam antenna, and narrow-beam antenna are all electrically connected to the measurement host. The measurement host includes a control switch, which is used to selectively operate the transmitting antenna, wide-beam transmitting antenna, and narrow-beam transmitting antenna in the monopole beam antenna group, thereby adapting to different operating states of the UAV.

[0059] Please see Figure 4 In this operating mode, when the drone is ascending or hovering, it moves vertically upwards, unaffected by obstacles. The narrow-beam antenna measures the distance between the drone and the ground, allowing for real-time monitoring of its altitude. Specifically, the narrow-beam transmitting antenna emits a signal, which is reflected off the ground and received by the narrow-beam receiving antenna, which then calculates the distance between the ground and the drone.

[0060] Please see Figure 5 and Figure 6 When the drone is operating in a horizontal, terrain-following mode, it needs to acquire information about changes in obstacles and terrain below it. A control switch allows the wide-beam transmitting antenna, narrow-beam transmitting antenna, and monopole antenna array to selectively operate. The narrow-beam transmitting and receiving antennas measure the distance between the drone and the ground as l1, the wide-beam transmitting and receiving antennas measure the distance between the drone and obstacles as l2, and the monopole antenna array measures the distance between the drone and obstacles as l3. The obstacle avoidance threshold is R, which can be set based on parameters such as the drone's flight speed. The obstacle avoidance threshold should not be too high or too low; it must ensure the drone's safety while minimizing the number of ineffective obstacle avoidance attempts.

[0061] Please see Figure 5, the beam of the wide-beam antenna is wider than that of the narrow-beam antenna, and it can detect the terrain obliquely below the UAV in a wider range. When l1>l2, it means that the distance between the UAV and the terrain obliquely below the UAV is less than the distance between the ground directly below the UAV and the UAV, that is, it represents that there is a terrain elevation area obliquely below the UAV. If at the same time l2>R, it means that the distance between the terrain elevation area and the UAV is greater than the avoidance threshold. At this time, the UAV ascends to increase the distance between it and the terrain elevation area to prevent the UAV from colliding with the terrain elevation area.

[0062] Please refer to Figure 6 , when l1>l2, it means that the distance between the UAV and the terrain obliquely below the UAV is less than the distance between the ground directly below the UAV and the UAV, that is, it represents that there is a terrain elevation area obliquely below the UAV. If at the same time l2<R, or when l3<R, it means that the slope of the terrain elevation area is steep, and the UAV needs to avoid obstacles or brake. The obstacle avoidance can be an obstacle avoidance program preset for the UAV, such as vertically lifting the UAV, or lifting the UAV obliquely upward at a certain slope, or directly braking, etc.

[0063] When the UAV performs obstacle avoidance, the monopole beam antenna measures the distance l3 between the UAV and the obstacle, and measures the echo angle of the echo signal. Due to its wider beam, the monopole beam antenna group can detect the terrain obliquely below the UAV in a wider range. Especially when the slope is large, the monopole beam antenna can measure the distance between the obstacle near the side of the UAV and the UAV and the slope of the obstacle. The slope of the obstacle can be obtained through the echo angle. The distance between the UAV and the obstacle measured by the monopole beam antenna and the echo angle of the echo signal are both input into the emergency braking module of the UAV, and then obstacle avoidance or braking is performed.

[0064] Please refer to Figure 7 , when the UAV is descending, in this working mode, it is necessary to judge the obstacles below the UAV and the height of the UAV from the ground. The control switch makes the transmitting antennas of the narrow-beam transmitting antenna and the monopole beam antenna group work selectively. The narrow-beam transmitting antenna and the narrow-beam receiving antenna measure the distance l1 between the UAV and the ground, the monopole beam antenna group measures the distance l3 between the UAV and the obstacle, the obstacle avoidance threshold is R, and when l3<R, the UAV performs obstacle avoidance or braking. The steps and principles of the UAV's avoidance are as described in the previous paragraph and will not be repeated here.

[0065] The UAV radar in the above embodiment includes a measurement host, a monopole beam antenna group, a wide-beam transmitting antenna, a wide-beam receiving antenna, a narrow-beam transmitting antenna, and a narrow-beam receiving antenna. The beamwidths of the monopole beam antenna group, the wide-beam antenna, and the narrow-beam antenna decrease sequentially. The narrow-beam antenna has a narrower beam, making it more accurate in measuring the distance between the UAV and the ground. Therefore, it can measure the angle between the UAV and the ground in various states such as ascent, descent, hovering, and terrain following. The wide-beam antenna has a wider beam, providing a wider measurement range. It can assist in measuring whether there are obstacles diagonally below the UAV, enabling the UAV to avoid obstacles diagonally below when the terrain changes. The monopole beam antenna group has the widest beamwidth, allowing for rapid measurement of obstacles to the side and diagonally below in steep terrain, enabling the UAV to quickly avoid obstacles or stop. Thus, this UAV radar is feature-rich, suitable for various states such as ascent, descent, hovering, and terrain following, provides relatively accurate measurement results, and does not require the use of rotating radar, exhibiting strong structural stability and a long service life.

[0066] In one embodiment of the present invention, please refer to Figure 1 and Figure 3 The monopole beam antenna array includes a first transmitting monopole antenna, a second transmitting monopole antenna, a first receiving monopole antenna, and a second receiving monopole antenna. The line connecting the first and second transmitting monopole antennas is a first reference line, and the line connecting the first and second receiving monopole antennas is a second reference line. The first and second reference lines are set at an angle, thereby allowing the measurement of the echo angle of the echo signal.

[0067] In some embodiments, the transmitted beam of the first monopole antenna is received by a first receiving monopole antenna and a second receiving monopole antenna to facilitate the measurement of the angle between the echo signal and the second reference line. Specifically, since the first receiving monopole antenna and the second receiving monopole antenna are spaced apart, they receive the same signal at different times. This time difference can be used to calculate the distance difference between the two transmission paths. Since the distance between the first receiving monopole antenna and the second receiving monopole antenna is known, the angle between the echo signal and the second reference line can be calculated.

[0068] In some embodiments, the transmit beam of the second monopole antenna is received by the first and second receiving monopole antennas to facilitate the measurement of the angle between the echo signal and the second reference line. The measurement principle is similar to that described above and will not be repeated here.

[0069] In some embodiments, the beams emitted by the first transmitting monopole antenna and the second transmitting monopole antenna are both received by the first receiving monopole antenna to facilitate the measurement of the angle between the echo signal and the first reference line. The measurement principle is similar to that described above and will not be repeated here.

[0070] In some embodiments, the beams emitted by the first transmitting monopole antenna and the second transmitting monopole antenna are both received by the second receiving monopole antenna to facilitate the measurement of the angle between the echo signal and the first reference line. The measurement principle is similar to that described above and will not be repeated here.

[0071] In some embodiments of the present invention, the first reference line and the second reference line are perpendicular to each other. In three-dimensional space, the direction of any received signal can be defined by the angle between the incoming wave direction and the first reference line, and the angle between the incoming wave direction and the second reference line.

[0072] Optionally, the distance between the first transmitting monopole antenna and the second transmitting monopole antenna is half a wavelength, and the distance between the first receiving monopole antenna and the second receiving monopole antenna is also half a wavelength. Setting the distance to half a wavelength serves two purposes: first, it minimizes the distance between the two receiving antennas and the two transmitting antennas, ensuring that the time difference between the received signal reaching the two different receiving antennas does not exceed one cycle, thus guaranteeing the accuracy of the direction of arrival calculation; second, it reduces the computational burden related to the direction of arrival.

[0073] It should be noted that the principle of measuring the echo angle can be found in the embodiment provided in the UAV radar control method, and will not be repeated here.

[0074] In one embodiment of the present invention, please refer to Figure 1 The measurement host includes a signal transmission module and a signal processing module. The signal transmission module is used to process the transmitted signal so that the transmitted signal is emitted through each transmitting antenna. The signal processing module is used to process the received signal from each receiving antenna.

[0075] In some embodiments, the signal transmission module includes a control switch, which is a single-pole four-throw switch. The four contacts of the single-pole four-throw switch are respectively connected to a wide-beam transmitting antenna, a narrow-beam transmitting antenna, a first transmitting monopole antenna, and a second transmitting monopole antenna. When the drone is hovering or ascending, the single-pole four-throw switch keeps the narrow-beam transmitting antenna always connected to the signal transmission module. When the drone is horizontally following the terrain, the single-pole four-throw switch keeps the wide-beam transmitting antenna, narrow-beam transmitting antenna, first transmitting monopole antenna, and second transmitting monopole antenna connected to the signal transmission module alternately. When the drone is descending, the single-pole four-throw switch keeps the narrow-beam transmitting antenna, first transmitting monopole antenna, and second transmitting monopole antenna connected to the signal transmission module alternately.

[0076] In some embodiments, the signal transmission module includes a control switch comprising four single-pole single-throw (SPS) switches. One end of each of the four SPS switches is connected to a wide-beam transmitting antenna, a narrow-beam transmitting antenna, a first transmitting monopole antenna, and a second transmitting monopole antenna, respectively. Thus, in various operating modes of the UAV, each SPS switch can be selectively turned on and off.

[0077] In some embodiments, the signal transmitting module further includes a signal modulation circuit, a voltage-controlled oscillator, a power divider, and four radio frequency (RF) amplifiers connected in sequence. The four RF amplifiers are electrically connected to a wide-beam transmitting antenna, a narrow-beam transmitting antenna, a first transmitting monopole antenna, and a second transmitting monopole antenna, respectively. The power divider and the four RF amplifiers are electrically connected via control switches. The control switches are single-pole four-throw switches, with their four stationary contacts electrically connected to the four RF amplifiers, and one moving contact electrically connected to the power divider. Alternatively, four single-pole single-throw switches can be used, with their moving contacts all connected to the power divider, and their stationary contacts electrically connected to the four RF amplifiers. The signal modulation circuit generates a voltage waveform (e.g., ...) for modulating the signal. Figure 10 (See the schematic diagram in the upper left corner). This voltage waveform drives a voltage-controlled oscillator (VCO), thereby generating a signal whose frequency increases linearly with time, i.e., a linearly modulated continuous wave (LFMCW). This part of the circuit typically uses a phase-locked loop (PLL) in conjunction with the VCO to achieve a low-distortion LFMCW signal. Part of this LFMCW signal is amplified by an RF amplifier (PA) and transmitted through a transmitting antenna; the other part is distributed to the mixer through a power divider.

[0078] In some embodiments, the signal processing module includes four signal processing units. Each of the four signal processing units includes a low-noise amplifier, a mixer, a filter amplifier, and an analog-to-digital converter, all electrically connected in sequence. A wide-beam receiving antenna, a narrow-beam receiving antenna, a first receiving monopole antenna, and a second receiving monopole antenna are electrically connected to the four low-noise amplifiers, respectively. The mixer is electrically connected to the power divider of the signal transmitting module. The transmitted signal, after passing through multiple transmission paths to the corresponding receiving antenna, enters the low-noise amplifier (LNA). After mixing and filtering, an intermediate frequency (IF) signal is obtained, which is then converted by the analog-to-digital converter (ADC).

[0079] Please see Figure 8 The present invention also provides a drone, which includes the drone radar in any of the above embodiments.

[0080] The UAV provided by this invention employs the aforementioned UAV radar, which includes a measurement host, a monopole beam antenna group, a wide-beam transmitting antenna, a wide-beam receiving antenna, a narrow-beam transmitting antenna, and a narrow-beam receiving antenna. The beamwidths of the monopole beam antenna group, the wide-beam antenna, and the narrow-beam antenna decrease sequentially. The narrow-beam antenna has a narrower beam, providing more accurate measurement of the distance between the UAV and the ground, thus enabling the measurement of the angle between the UAV and the ground during ascent, descent, hovering, and terrain-following maneuvers. The wide-beam antenna has a wider beam, providing a broader measurement range, and can assist in measuring the presence of obstacles diagonally below the UAV, allowing the UAV to avoid obstacles diagonally below when the terrain changes. The monopole beam antenna group has the widest beam velocity, enabling rapid measurement of obstacles to the side and diagonally below on steep terrain, allowing the UAV to quickly avoid obstacles or stop. Therefore, this UAV radar is feature-rich, suitable for various UAV states such as ascent, descent, hovering, and terrain-following, provides relatively accurate measurement results, eliminates the need for rotating radar, has strong structural stability, and a long service life.

[0081] In some embodiments of the present invention, please refer to Figure 8 The drone also includes a flight control system, which is electrically connected to the drone's radar. The flight control system includes an attitude control module, a drive module, a flight data module, and an emergency braking module. The drone's radar transmits data to the flight control system via a data cable. The drone radar sends the collected data to the drive module of the flight control system via the data cable. After receiving the data, the drive module transmits it to the attitude control module to control the drone's altitude. The drive module transmits obstacle avoidance data to the emergency braking system, enabling the drone to avoid obstacles or stop in time when it encounters them. The flight control system collects flight data and transmits the radar mode selection to the radar via the drive module, thereby controlling the radar's operating mode.

[0082] This invention also provides a method for controlling a drone radar; please refer to [link / reference]. Figure 9 The method used in the UAV radar of any of the above embodiments includes the following steps:

[0083] When the drone hovers or ascends, a control switch activates the narrow-beam transmitting antenna to measure the distance between the drone and the ground.

[0084] When the UAV is following the terrain horizontally, the control switch enables the transmitting antennas of the wide-beam transmitting antenna, narrow-beam transmitting antenna, and monopole beam antenna group to operate selectively;

[0085] As the drone descends, the control switch selectively activates the narrow-beam transmitting antenna and the monopole beam antenna array.

[0086] Through the above embodiments, the UAV radar control method is applicable to various states of UAVs such as ascent, descent, hovering, and terrain following. The measurement results are relatively accurate, and there is no need to use rotating radar. The structure is highly stable and has a long service life.

[0087] In some embodiments of the present invention, please refer to Figure 4 In this operating mode, when the drone is ascending or hovering, it moves vertically upwards, unaffected by obstacles. The narrow-beam antenna measures the distance between the drone and the ground, allowing for real-time monitoring of its altitude. Specifically, the narrow-beam transmitting antenna emits a signal, which is reflected off the ground and received by the narrow-beam receiving antenna, which then calculates the distance between the ground and the drone.

[0088] In some embodiments of the present invention, please refer to Figure 5 and Figure 6 When the drone is operating in a horizontal, terrain-following mode, it needs to acquire information about changes in obstacles and terrain below it. A control switch allows the wide-beam transmitting antenna, narrow-beam transmitting antenna, and monopole antenna array to selectively operate. The narrow-beam transmitting and receiving antennas measure the distance between the drone and the obstacle as l1, the wide-beam transmitting and receiving antennas measure the distance as l2, and the monopole antenna array measures the distance as l3. The obstacle avoidance threshold is R, which can be set based on parameters such as the drone's flight speed. The obstacle avoidance threshold should not be too high or too low; it must ensure the drone's safety while minimizing the number of ineffective obstacle avoidance attempts.

[0089] Please see Figure 5 Wide-beam antennas have a wider beam than narrow-beam antennas, enabling them to detect terrain diagonally below the drone over a wider area. When l1 > l2, it indicates that the distance between the drone and the diagonally below it is less than the distance between the drone and the ground directly below it, meaning there is a terrain elevation area diagonally below the drone. If l2 > R at the same time, it means that the distance between the terrain elevation area and the drone is greater than the avoidance threshold. In this case, the drone rises to increase the distance between itself and the terrain elevation area, preventing a collision.

[0090] Please see Figure 6When l1 > l2, it indicates that the distance between the lower oblique side of the UAV and the UAV is less than the distance between the bottom surface directly below the UAV and the UAV, which means there is a terrain elevation area below the lower oblique side of the UAV. If at the same time l2 < R, or when l3 < R, it means the slope of the terrain elevation area is steep, and the UAV needs to avoid obstacles or brake. The obstacle avoidance can be an obstacle avoidance program preset for the UAV, such as vertically lifting the UAV, or lifting the UAV obliquely upward at a certain slope, or directly braking, etc.

[0091] When the UAV performs obstacle avoidance, the monopole beam antenna measures the distance l3 between the UAV and the obstacle, and measures the echo angle of the echo signal. Due to the relatively wide beam of the monopole beam antenna group, it can detect the terrain below the lower oblique side of the UAV in a wider range. Especially when the slope is large, the monopole beam antenna can measure the distance between the obstacle near the side of the UAV and the UAV, as well as the slope of the obstacle. The slope of the obstacle can be obtained through the echo angle. Both the distance between the UAV and the obstacle measured by the monopole beam antenna and the echo angle of the echo signal are input into the emergency braking module of the UAV, and then obstacle avoidance or braking is performed.

[0092] In some embodiments of the present invention, please refer to Figure 7 , when the UAV is descending, in this working mode, it is necessary to judge the obstacles below the UAV and the height of the UAV from the ground. The control switch makes the transmitting antennas of the narrow beam transmitting antenna and the monopole beam antenna group work selectively. The narrow beam transmitting antenna and the narrow beam receiving antenna measure the distance between the UAV and the obstacle as l1, the monopole beam antenna group measures the distance l3 between the UAV and the obstacle, and the obstacle avoidance threshold is R. When l3 < R, the UAV performs obstacle avoidance or braking. The steps and principles of the UAV's avoidance are as described in the previous paragraph and will not be elaborated here.

[0093] The steps of ranging with the narrow beam antenna, wide beam antenna, and monopole beam antenna are the same. Taking the narrow beam antenna as an example, the ranging steps include:

[0094] 1) The narrow beam transmitting antenna emits electromagnetic waves, which are received by the narrow beam receiving antenna, and windowing is performed on the time-domain waveform data of the receiving channel. The window function can be a Hanning window, Hamming window, etc. The purpose of windowing is to reduce the truncation effect of the time-domain to frequency-domain conversion. 2) Perform FFT transformation on the received new signal, that is, perform time-frequency domain conversion. 3) Perform peak search on the amplitude spectrum of the FFT to obtain a list of the positions of the signal peak points. 4) Perform spectrum subdivision based on the above list positions, and obtain the spectrum peak position index list and amplitude value list after subdivision. 5) Find the frequency value corresponding to the spectrum peak position index list, and thus obtain the distance according to formula (9), where f is the frequency of the intermediate frequency signal, μ is the slope of the frequency-modulated continuous wave, and c is the speed of light

[0095]

[0096] It should be noted that the distances between the drone and the ground or obstacles measured by each antenna in the drone radar are the minimum distances of the measured data. Please refer to [link / reference]. Figure 10 and Figure 11 The transmitting antenna transmits a frequency-modulated continuous wave signal, a linear frequency-modulated continuous wave (LFMCW). The frequency of the received echo changes in the same way as the transmitted frequency, both following a triangular wave pattern. There is a time difference between the received and transmitted signals. Figure 10 The lower left corner shows the relationship between time and frequency (frequency domain) of a linear frequency modulated continuous wave signal. Specifically, time and frequency change linearly, with the longer the time, the higher the frequency. Figure 10 The right-hand figure shows the time-amplitude relationship (time domain) of a linear frequency modulated (LFM) continuous wave (LCW) signal, with the amplitude exhibiting a sinusoidal waveform over time. The LFM LW signal emitted is called the transmitted signal, and the signal reaching the three receiving antennas after reflection or direct propagation through the air is called the received signal. Please refer to [link / reference]. Figure 11 The received signal is equivalent to the transmitted signal shifted to the right by a distance τ, where τ is the time difference (delay) between the transmitted and received signals.

[0097] Of the transmitted signal, a portion may reach the receiving antenna directly; this portion is called the line-of-sight (LOS) signal. The signal that arrives after being reflected from the environment is called the non-line-of-sight (NLOS) signal. Regardless of the type, when the signal reaches the receiving antenna, it has undergone a certain time delay and signal attenuation. In UAV radar ranging, it is necessary to measure the transmission distance of the line-of-sight signal.

[0098] The following example demonstrates distance measurement calculations using a line-of-sight signal.

[0099] A linear frequency modulated continuous wave transmitted signal can be described as:

[0100]

[0101] Where f0 is the starting frequency. A0 represents the initial phase of the signal, A0 represents the amplitude of the transmitted power, and μ is the frequency modulation slope, which is the rate of change of the transmitted signal frequency over time.

[0102] Assume the signal reaches the receiving antenna after time τ. And assume the distance between the transmitting and receiving antennas is R. Where c represents the speed of light. There is a frequency difference Δf = μt between the received signal and the corresponding transmitted signal.

[0103] The corresponding received signal can be described as:

[0104]

[0105] Where K r This is the attenuation factor.

[0106] The transmitted signal and the received signal from the receiving antenna are mixed, that is, S... r (t) and S t (t) Mixing (multiplying formula (1) and formula (2)) yields:

[0107]

[0108] The above equation contains two frequency components: a high-frequency component with a dominant frequency of 2f0 in the first half, and a low-frequency component with a frequency of μt. The high-frequency component is easily filtered out by a low-pass filter, thus yielding the intermediate frequency signal:

[0109]

[0110] Generally, after adopting standard dimensions, τ is typically on the order of nanoseconds, therefore τ 2 The value of is extremely small and can be ignored, so the above formula simplifies to:

[0111]

[0112] Here, f0τ represents a distance-dependent phase, and μτ is a distance-dependent frequency.

[0113] Finally, formula (5) is used.

[0114]

[0115] Solve for the value of τ, and then according to Calculate the distance.

[0116] In one embodiment of the present invention, please refer to Figure 1 and Figure 3 The monopole beam antenna array includes a first transmitting monopole antenna, a second transmitting monopole antenna, a first receiving monopole antenna, and a second receiving monopole antenna. The line connecting the first and second transmitting monopole antennas is a first reference line, and the line connecting the first and second receiving monopole antennas is a second reference line. The first and second reference lines are set at an angle, thereby allowing the measurement of the echo angle of the echo signal.

[0117] In some embodiments, the transmitted beam of the first transmitting monopole antenna is received by a first receiving monopole antenna and a second receiving monopole antenna to facilitate the measurement of the angle between the echo signal and the second reference line. The transmitted beams of both the first and second transmitting monopole antennas are received by the first receiving monopole antenna. The first and second reference lines are perpendicular to each other, and the distance between the first and second transmitting monopole antennas is half a wavelength, as is the distance between the first and second receiving monopole antennas.

[0118] The specific procedures for distance and angle measurement are as follows: Figure 13 As shown. The transmitted beam of the first transmitting monopole antenna (TX3) is received by the first receiving monopole antenna (RX3) and the second receiving monopole antenna (RX4) to facilitate the measurement of the angle between the echo signal and the second reference line. The transmitted beams of the first transmitting monopole antenna (TX3) and the second transmitting monopole antenna (TX4) are simultaneously received by the first receiving monopole antenna (RX3).

[0119] Windowing is applied to the time-domain waveform data of the receiving channel. Window functions can include Hanning windows, Hamming windows, etc. The purpose of windowing is to reduce the truncation effect during the time-to-frequency domain conversion. An FFT transform is performed on the receiving channel to perform a time-to-frequency domain conversion. A peak search is performed on the amplitude spectrum of the FFT to obtain a list of signal peak locations. The spectrum is subdivided based on these locations, and a list of peak location indices and amplitude values ​​is obtained. Based on the index list locations, a single-point time-to-frequency domain transformation is performed on the corresponding spectra of the two receiving channels to obtain the phase information of these points. The phase difference between the two receiving channels at the corresponding index locations is calculated, and thus a list of signal incident angles is derived.

[0120] Taking the example of a first transmitting monopole antenna emitting a beam, which is received by a first receiving monopole antenna and a second receiving monopole antenna, this section explains how to measure and calculate the echo angle. For examples of embodiments where the first and second transmitting monopole antennas emit beams, and the first monopole antenna receives them, please refer to the following explanation; it will not be repeated here.

[0121] Please see Figure 12 When an incident plane wave (received signal) reaches the first and second receiving monopole antennas at an incident angle θ1, the tilt of the incident angle relative to the first reference line results in a distance difference l between the two antennas. The relationship between this distance difference l and the angle θ1 is as follows:

[0122]

[0123] Assuming the first receiving monopole antenna is the primary channel, meaning the intermediate frequency (IF) signal received by the first receiving monopole antenna is described in the form of formula (7), then the IF signals received by the first and second receiving monopole antennas can be described as follows:

[0124]

[0125]

[0126] Where Δτ is the time difference caused by the distance difference l, and obviously Δτ = 1 / c. Furthermore, for μ(τ + Δτ)t, since Δτ is very small relative to τ, its change in frequency is generally negligible. Therefore, we can approximate IF2(t) as:

[0127]

[0128] Assume that IF1(t) and IF2(t) have phase angles at frequency μτ, respectively. and So

[0129]

[0130] Thus, the angle θ1 between the received signal and the first reference line can be obtained. Similarly, the angle θ2 between the received signal and the second reference line can be obtained using the same method, thereby obtaining the angle of arrival of the received signal.

[0131] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An unmanned mine radar characterized by, The application relates to an unmanned aerial vehicle obstacle avoidance system. The application comprises: a monopole beam antenna group for measuring the distance between the unmanned aerial vehicle and an obstacle and measuring the echo angle of an echo signal to provide obstacle avoidance information, the beam width of the monopole beam antenna group being greater than 85 degrees; a wide-beam transmitting antenna for transmitting a beam with a width greater than 25 degrees and less than 80 degrees; a wide-beam receiving antenna for receiving the beam transmitted by the wide-beam transmitting antenna; a narrow-beam transmitting antenna for transmitting a beam with a width less than 25 degrees; a narrow-beam receiving antenna for receiving the beam transmitted by the narrow-beam transmitting antenna; a measurement host for processing the transmitted and received beams of the antennas, the measurement host having a control switch for selectively operating the transmitting antennas in the monopole beam antenna group, the wide-beam transmitting antenna and the narrow-beam transmitting antenna; the wide-beam transmitting antenna and the wide-beam receiving antenna are used for measuring the distance between the unmanned aerial vehicle and an obstacle to determine whether the unmanned aerial vehicle needs to avoid the obstacle; the narrow-beam transmitting antenna and the narrow-beam receiving antenna are used for measuring the distance between the unmanned aerial vehicle and the ground; 2. The drone radar of claim 1, wherein, the monopole beam antenna group comprises a first transmitting monopole antenna, a second transmitting monopole antenna, a first receiving monopole antenna and a second receiving monopole antenna, the connecting line of the first transmitting monopole antenna and the second transmitting monopole antenna is a first reference line, the connecting line of the first receiving monopole antenna and the second receiving monopole antenna is a second reference line, the first reference line and the second reference line are arranged at an angle, the transmitting beam of the first transmitting monopole antenna or the second transmitting monopole antenna is received by the first receiving monopole antenna and the second receiving monopole antenna to measure the angle between the echo signal and the second reference line, and the transmitting beams of the first transmitting monopole antenna and the second transmitting monopole antenna are simultaneously received by the first receiving monopole antenna or the second receiving monopole antenna to measure the angle between the echo signal and the first reference line.

3. The drone radar of claim 2, wherein, The measurement host comprises a signal transmitting module and a signal processing module, the signal transmitting module comprises the control switch, and the control switch is a single-pole four-throw switch; the monopole beam antenna group comprises a first transmitting monopole antenna, a second transmitting monopole antenna, a first receiving monopole antenna and a second receiving monopole antenna, and the four contacts of the single-pole four-throw switch are connected with the wide-beam transmitting antenna, the narrow-beam transmitting antenna, the first transmitting monopole antenna and the second transmitting monopole antenna respectively. The signal transmitting module further comprises a signal modulation circuit, a voltage-controlled oscillator, a power divider and four radio frequency amplifiers which are sequentially and electrically connected, the four radio frequency amplifiers are electrically connected with the wide-beam transmitting antenna, the narrow-beam transmitting antenna, the first transmitting monopole antenna and the second transmitting monopole antenna respectively, the power divider and the four radio frequency amplifiers are electrically connected through the single-pole four-throw switch, the voltage-controlled oscillator is driven by the signal modulation circuit, and the power divider is used for transmitting the transmitting signals to the radio frequency amplifiers and the signal processing module respectively.

4. The drone radar of claim 2, wherein, The signal processing module comprises four signal processing units, each of which comprises a low noise amplifier, a mixer, a filter amplifier and an analog-digital converter connected in sequence, the wide-beam receiving antenna, the narrow-beam receiving antenna, the first receiving monopole antenna and the second receiving monopole antenna are electrically connected with the four low noise amplifiers respectively, and the mixer is electrically connected with the power divider of the signal transmitting module.

5. The drone of claim 1, wherein, The unmanned aerial vehicle radar comprises the unmanned aerial vehicle and the unmanned aerial vehicle radar.

6. A method for controlling a drone radar according to any one of claims 1-4, c h a r a c t e r i s e d i n that The unmanned aerial vehicle radar comprises the unmanned aerial vehicle and the unmanned aerial vehicle radar. When the unmanned aerial vehicle hovers or ascends, the control switch is controlled to make the narrow-beam transmitting antenna work, and the distance between the unmanned aerial vehicle and the ground is measured; When the unmanned aerial vehicle hovers horizontally, the control switch is controlled to make the wide-beam transmitting antenna, the narrow-beam transmitting antenna and the transmitting antennas of the monopole antenna group work selectively; When the unmanned aerial vehicle descends, the control switch is controlled to make the narrow-beam transmitting antenna and the transmitting antennas of the monopole antenna group work selectively.

7. The unmanned mine radar control method of claim 6, wherein, When the unmanned aerial vehicle hovers horizontally, the control switch is controlled to make the wide-beam transmitting antenna, the narrow-beam transmitting antenna and the transmitting antennas of the monopole antenna group work selectively, The narrow-beam transmitting antenna and the narrow-beam receiving antenna measure the distance between the UAV and the obstacle as l 1, the wide-beam transmitting antenna and the wide-beam receiving antenna measure the distance between the UAV and the obstacle as l 2, the monopole beam antenna group measures the distance between the UAV and the obstacle as l 3, the obstacle avoidance threshold is R, l 1> l 2>R, the UAV performs a pull-up; l 1> l 2 and l 2 < R, or l 1> l 2 and l 3 < R, the unmanned aerial vehicle avoids obstacles or stops. 8.The unmanned mine radar control method of claim 6, wherein, When the unmanned aerial vehicle descends, the control switch is controlled to make the narrow-beam transmitting antenna and the transmitting antennas of the monopole antenna group work selectively, The narrow-beam transmitting antenna and the narrow-beam receiving antenna measure the distance between the UAV and the obstacle l 1, the monopole beam antenna group measures the distance between the UAV and the obstacle l 3, the obstacle avoidance threshold is R, l When 3 < R, the UAV performs obstacle avoidance or stops.

9. The unmanned mine radar control method of claim 7 or 8, wherein, The step of obstacle avoidance of the unmanned aerial vehicle comprises: the monopole beam antenna group measures the distance between the unmanned aerial vehicle and the obstacle l 3, and measures the echo angle of the echo signal, and transmits the measured obstacle avoidance data to the emergency braking module of the unmanned aerial vehicle.

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