CN117032278A - Unmanned aerial vehicle inspection obstacle avoidance method and system based on saw-tooth millimeter wave radar - Google Patents
Unmanned aerial vehicle inspection obstacle avoidance method and system based on saw-tooth millimeter wave radar Download PDFInfo
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Abstract
The invention discloses an unmanned aerial vehicle inspection obstacle avoidance method based on a zigzag millimeter wave radar, which is characterized in that the ranging of an unmanned aerial vehicle and an obstacle is realized by utilizing the zigzag millimeter wave radar, a detection result is transmitted to a control system as a flight instruction, the flight direction and the gesture of the unmanned aerial vehicle are adjusted, the flight monitoring of the unmanned aerial vehicle on a power transmission line is completed, the safe distance between the unmanned aerial vehicle and the obstacle is kept, the stability of the shooting picture of the unmanned aerial vehicle is further ensured, and the unmanned aerial vehicle inspection obstacle avoidance method has the characteristics of high inspection efficiency, high universality, high safety and the like.
Description
Technical Field
The invention relates to the technical field of radar communication and the technical field of unmanned aerial vehicle remote real-time monitoring, in particular to an unmanned aerial vehicle inspection obstacle avoidance method and system based on a saw-tooth millimeter wave radar.
Background
At present, an unmanned aerial vehicle detects an obstacle, and most of unmanned aerial vehicles detect the obstacle by adopting a single sensor, or detect the obstacle in daily use by adopting a few sensors, and the obstacle detection method and the obstacle avoidance strategy are too simple without comprehensively considering the complex environment of the power line inspection site.
Because the unmanned aerial vehicle has limited carrying capacity, in order to maximally execute tasks, the occupied volume and weight of airborne equipment should be as small as possible, and the millimeter wave radar obstacle avoidance technology just meets the requirement. In the flying process of the unmanned plane, the obstacle avoidance power line is a very typical loop, because the radar scattering cross section area of the power line is very small, and quite high requirements are imposed on the detection angle and the distance resolution. The millimeter wave radar has the advantages of large bandwidth, narrow beam, small wavelength and low power consumption, completely meets the requirements, can work normally in severe weather such as rain and snow, haze, sand dust and the like, has strong ground clutter resistance, and enables an unmanned aerial vehicle to work in all weather. However, millimeter wave-based radar ranging has a problem of poor azimuth judging ability. In order to solve the problem, the project adopts coupling binocular vision and a laser radar, and further improves the accuracy and azimuth angle of ranging. The unmanned aerial vehicle autonomous obstacle avoidance system designed by the scheme has the advantages of small size, low power consumption and the like, and has great application potential in the aspect that the unmanned aerial vehicle autonomously avoids obstacles in the environment.
Millimeter waves are a segment of radio waves, and electromagnetic waves having a wavelength of 1 to 10 mm are called millimeter waves, and millimeter wave radars are radars of millimeter wave band. The ranging principle is the same as that of a general radar, i.e., a radar wave is transmitted and then an echo is received, and position data of a target is measured according to a time difference between a transmitter and a receiver. Common millimeter wave radar signal modulation forms include saw-tooth wave modulation, triangular wave modulation, sine wave, and the like. Millimeter wave radar in the form of triangular wave modulation is mainly used in complex applications where it is necessary to measure both the distance and the speed of an object. However, in the commonly used unmanned aerial vehicle obstacle avoidance application, the obstacle on the unmanned aerial vehicle flight path is generally a transmission wire or a tree obstacle, most of the obstacle is a static obstacle, the monitoring of the object speed is not necessary, and the millimeter wave radar in the form of triangular wave modulation generates larger calculation amount and data redundancy and is not suitable for unmanned aerial vehicle inspection obstacle avoidance application.
Disclosure of Invention
Aiming at the problems in the background technology, a brand-new unmanned aerial vehicle inspection obstacle avoidance method based on a saw-tooth millimeter wave radar is provided. Through the characteristic of the zigzag millimeter wave radar, the distance between the obstacle and the radar is related through beat signals, the obstacle on the unmanned aerial vehicle flight route is monitored in real time, and the unmanned aerial vehicle operation safety autonomous obstacle avoidance is ensured while the precision and all-weather operation are ensured.
According to the invention, the distance measurement of the unmanned aerial vehicle and the obstacle is realized by utilizing the zigzag millimeter wave radar, the detection result is transmitted to the control system as a flight instruction, the flight direction and the gesture of the unmanned aerial vehicle are adjusted, the flight monitoring of the unmanned aerial vehicle on the power transmission line is completed, the safety distance between the unmanned aerial vehicle and the obstacle is kept, the stability of the shooting picture of the unmanned aerial vehicle is further ensured, and the unmanned aerial vehicle has the characteristics of high inspection efficiency, high universality, high safety and the like.
The invention relates to an unmanned aerial vehicle inspection obstacle avoidance method based on a zigzag millimeter wave radar, which comprises the following steps:
s1, obtaining a sawtooth wave modulation signal generated by a sawtooth wave generator and transmitting the sawtooth wave modulation signal to a voltage-controlled oscillator;
s2, the voltage-controlled oscillator generates a frequency-modulated continuous wave with zigzag frequency, one path of frequency-modulated continuous wave is amplified by the power amplifier and then transmitted into space, and the other path of frequency-modulated continuous wave is input into the mixer to serve as a local oscillation signal;
s3, receiving echo signals returned by the obstacle encountered by the frequency modulation continuous wave through a receiving antenna, and sending the echo signals into a mixer;
s4, mixing the echo signal and the local oscillation signal to form a beat signal;
s5, the frequency of the beat signal is in direct proportion to the distance between the obstacle and the radar, and the frequency of the beat signal is calculated to obtain the relative distance between the obstacle distance and the unmanned plane;
s6, judging whether the relative distance between the obstacle and the unmanned aerial vehicle is smaller than a set threshold distance;
and if the distance is smaller than the set threshold distance, adjusting the movement direction of the unmanned aerial vehicle to enable the unmanned aerial vehicle to move in a direction away from the obstacle.
According to the invention, the distance measurement of the unmanned aerial vehicle and the obstacle is realized by utilizing the zigzag millimeter wave radar, the detection result is transmitted to the control system as a flight instruction, the flight direction and the gesture of the unmanned aerial vehicle are adjusted, the flight monitoring of the unmanned aerial vehicle on the power transmission line is completed, the safety distance between the unmanned aerial vehicle and the obstacle is kept, the stability of the shooting picture of the unmanned aerial vehicle is further ensured, and the unmanned aerial vehicle has the characteristics of high inspection efficiency, high universality, high safety and the like.
Specifically, when the zigzag millimeter wave radar works, two separate transmitting antennas and receiving antennas are adopted, the millimeter wave is transmitted and received separately, and when the transmitting antennas do not transmit millimeter waves of one period, the receiving antennas start to receive echoes reflected by obstacles.
Further, the voltage-controlled oscillator generates a frequency-modulated continuous wave with a zigzag frequency, one path of the frequency-modulated continuous wave is amplified by the power amplifier and then transmitted into space, the other path of the frequency-modulated continuous wave is input into the mixer to serve as a local oscillation signal, and the frequency-modulated continuous wave is different from a carrier wave for a common radar serving as the local oscillation signal, and a low-frequency signal with a very low frequency is output after mixing.
Further, the frequency solving of the beat signal includes the steps of:
setting the time domain pulse width of the transmitted frequency modulation continuous wave as Tp, the initial frequency as fo and the bandwidth as B, and setting the modulation frequency of the signal as K=B/Tp; the frequency modulation continuous wave is reflected by an obstacle with the distance R and is received by a receiving antenna, and compared with a transmitting signal, an echo signal received by the receiving antenna has a delay tau=2r/c; based on the delay, the frequency of the beat signal generated after mixing is fτ=kτ.
Further, the transmission signal is:
S(t)＝cos(ω o t+Kπt 2 )
the echo signal is:
S r (t)＝cos[ω o (t-τ)+Kπ(t-τ) 2 ]
the multiplication of the first echo and the local oscillation 90-degree phase shift is as follows:
output result Q of the multiplication 0 (t) low pass filtering to obtain:
the second echo is directly multiplied by the local oscillator to be I 0 (t)
Output result I of the multiplication 0 (t) low pass filtering to obtain
Combining baseband signals I and Q into a complex signal Z (t)
Fourier transforming the complex signal Z (t) to obtain
The frequency of the beat signal can thus be determined as long as the location in the frequency spectrum where the impact function delta (omega) is located is determined.
Further, the relationship between the frequency of the beat and the obstacle distance is:
when the parameters B and Tp are fixed, the beat frequency fτ is proportional to the distance R of the obstacle; in the millimeter wave radar system, the delay of the echo signal is negligible compared with the pulse width Tp of the transmission signal, and therefore the output beat signal is considered to contain only the frequency fτ.
The invention also provides an unmanned aerial vehicle inspection obstacle avoidance system based on the saw-tooth millimeter wave radar, which comprises the following steps:
the device comprises a sawtooth wave transmitting module, a receiving module, a calculating module and a control module;
the sawtooth wave transmitting module comprises a sawtooth wave generator, a voltage-controlled oscillator, a power divider, a power amplifier and a transmitting antenna;
the receiving module comprises a receiving antenna, a mixer and an operational amplifier;
the calculation module obtains the frequency of the beat signal through quadrature demodulation, so as to obtain the relative distance between the obstacle and the unmanned aerial vehicle;
the control module is used for judging whether the relative distance between the obstacle and the unmanned aerial vehicle is smaller than a preset safety distance, and if the relative distance is smaller than the preset safety distance, the unmanned aerial vehicle is controlled to adjust the flight direction to be away from the obstacle.
Further, the present invention provides a readable storage medium having stored thereon a control program, characterized in that: the control program is executed by the processor to realize the unmanned aerial vehicle inspection obstacle avoidance method based on the saw-tooth millimeter wave radar.
Further, the present invention also provides a computer control system including a memory, a processor, and a control program stored in the memory and executable by the processor, characterized in that: the unmanned aerial vehicle inspection obstacle avoidance method based on the saw-tooth millimeter wave radar is realized when the processor executes the control program.
In order that the invention may be more clearly understood, specific embodiments thereof will be described below with reference to the accompanying drawings.
Drawings
FIG. 1 is a flowchart of a method for inspecting a saw-tooth millimeter wave radar in an embodiment of the invention;
fig. 2 is a block diagram of a millimeter wave radar system according to an embodiment of the present invention;
fig. 3 is a time-frequency diagram of a saw-tooth millimeter wave radar according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a millimeter wave quadrature demodulation process according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an autonomous obstacle avoidance system of an unmanned aerial vehicle according to an embodiment of the present invention.
Detailed Description
Referring to fig. 1, a flowchart of a method for inspecting a saw-tooth millimeter wave radar according to an embodiment of the present invention is shown;
the invention relates to an unmanned aerial vehicle inspection obstacle avoidance method based on a zigzag millimeter wave radar, which comprises the following steps:
s1, obtaining a sawtooth wave modulation signal generated by a sawtooth wave generator and transmitting the sawtooth wave modulation signal to a voltage-controlled oscillator;
s2, the voltage-controlled oscillator generates a frequency-modulated continuous wave with zigzag frequency, one path of frequency-modulated continuous wave is amplified by the power amplifier and then transmitted into space, and the other path of frequency-modulated continuous wave is input into the mixer to serve as a local oscillation signal;
s3, receiving echo signals returned by the obstacle encountered by the frequency modulation continuous wave through a receiving antenna, and sending the echo signals into a mixer;
s4, mixing the echo signal and the local oscillation signal to form a beat signal;
s5, the frequency of the beat signal is in direct proportion to the distance between the obstacle and the radar, and the frequency of the beat signal is calculated to obtain the relative distance between the obstacle distance and the unmanned plane;
s6, judging whether the relative distance between the obstacle and the unmanned aerial vehicle is smaller than a set threshold distance;
and if the distance is smaller than the set threshold distance, adjusting the movement direction of the unmanned aerial vehicle to enable the unmanned aerial vehicle to move in a direction away from the obstacle.
In the embodiment of the invention, in order to ensure the data transmission effect of the laser radar carried by the unmanned aerial vehicle, a near-field infinite communication technology is adopted, and the communication frequencies of 2.4GHz and 5.8GHz are adopted, so that the data transmission distance and the signal transmission are ensured. According to the embodiment of the invention, the saw-tooth millimeter wave radar is adopted to mount the unmanned aerial vehicle, and the obstacle detection research is carried out through the saw-tooth millimeter wave radar unmanned aerial vehicle obstacle avoidance system, so that the real-time tracking of autonomous obstacle avoidance and lead and the real-time detection of tree obstacle are realized.
When the zigzag millimeter wave radar works, two separate transmitting antennas and two separate receiving antennas are adopted, the transmitting antennas and the receiving antennas transmit millimeter waves separately, and when the transmitting antennas do not transmit millimeter waves of one period, the receiving antennas start to receive echoes reflected by obstacles.
Further, the voltage-controlled oscillator generates a frequency-modulated continuous wave with a zigzag frequency, one path of the frequency-modulated continuous wave is amplified by the power amplifier and then transmitted into space, the other path of the frequency-modulated continuous wave is input into the mixer to serve as a local oscillation signal, and the frequency-modulated continuous wave is different from a carrier wave for a common radar serving as the local oscillation signal, and a low-frequency signal with a very low frequency is output after mixing.
Referring to fig. 2, a block diagram of a millimeter wave radar system according to an embodiment of the present invention is shown;
when the millimeter wave radar works, two separate transmitting antennas and receiving antennas are adopted, and when the transmitting antennas do not transmit millimeter waves for one period, the receiving antennas start to receive echoes reflected by obstacles. Structurally millimeter wave radar is mainly composed of four parts: the device comprises a rear end part consisting of a sawtooth wave generator and a VCO, an antenna part consisting of a transmitting antenna and a receiving antenna, a radio frequency front end part consisting of a power divider and a mixer, and a low-frequency signal conditioning part consisting of an operational amplifier.
The sawtooth wave generator is used for generating sawtooth wave modulation signals required by the VCO, and the VCO generates Frequency Modulation Continuous Wave (FMCW) signals with sawtooth-shaped changes in frequency under the action of the modulation signals. The frequency modulation continuous wave signal is divided into two paths for use, one path is amplified by a power amplifier and then transmitted to a space by a transmitting antenna, and part of the frequency modulation continuous wave signal is directly transmitted to a mixer to be used as a local oscillation signal, which is greatly different from a carrier wave which is generally used as the local oscillation signal by a common radar, and the frequency modulation continuous wave signal is output after mixing. The continuous wave signal transmitted by the transmitting antenna encounters an obstacle object and returns to the receiving antenna, and at the moment, the echo signal is delayed in time compared with the transmitting signal, and the echo signal is mixed with the local oscillation signal sent into the mixer to obtain a beat signal. The frequency of the beat signal is proportional to the distance between the obstacle target and the radar, and the distance between the obstacle target and the radar can be obtained by trying to obtain the frequency of the beat signal.
In an embodiment of the present invention, a time-frequency diagram of a saw-tooth millimeter wave radar is shown in fig. 3.
As can be seen from fig. 3, the frequency solving of the beat signal includes the following steps:
setting the time domain pulse width of the transmitted frequency modulation continuous wave as Tp, the initial frequency as fo and the bandwidth as B, and setting the modulation frequency of the signal as K=B/Tp; the frequency modulation continuous wave is reflected by an obstacle with the distance R and is received by a receiving antenna, and compared with a transmitting signal, an echo signal received by the receiving antenna has a delay tau=2r/c; based on the delay, the frequency of the beat signal generated after mixing is fτ=kτ.
The relationship between the frequency of the beat and the obstacle distance is as follows:
when the parameters B and Tp are fixed, the beat frequency fτ is proportional to the distance R of the obstacle; in the millimeter wave radar system, the delay of the echo signal is negligible compared with the pulse width Tp of the transmission signal, and therefore the output beat signal is considered to contain only the frequency fτ.
Please refer to fig. 4, which is a schematic diagram illustrating a millimeter wave quadrature demodulation process according to an embodiment of the present invention;
echo signals received by the receiving antenna are divided into an upper path and a lower path and enter the demodulator. The upper path is multiplied by the local oscillation signal to obtain a baseband signal I through a low-pass filter, and the lower path is multiplied by the 90-degree phase-shift signal of the local oscillation to obtain a baseband signal Q through the low-pass filter. The quadrature demodulated baseband signals I and Q may constitute real and imaginary parts of a certain complex signal.
Let the emission signal be:
S(t)＝cos(ω o t+Kπt 2 )
the echo signal is:
S r (t)＝cos[ω o (t-τ)+Kπ(t-τ) 2 ]
the multiplication of the first echo and the local oscillation 90-degree phase shift is as follows:
output result Q of the multiplication 0 (t) after low pass filtering:
the second echo is directly multiplied by the local oscillator to be I 0 (t)
Output result I of the multiplication 0 (t) can be obtained by subsequent low-pass filtering
Combining baseband signals I and Q into a complex signal Z (t)
Fourier transforming the complex signal Z (t) to obtain
From the above equation, it can be derived that the beat signal can be determined by determining the position of the impact function delta (omega) in the frequency spectrumA frequency; and quadrature-demodulates the frequency f of the output beat signal τ Has a simple proportional relation f with the obstacle echo time delay tau τ =kτ. The frequency point where the impact function is determined from the frequency spectrum is the key for determining the frequency of the beat signal, and further, the existence of an obstacle target at the frequency point is also indicated.
The unmanned aerial vehicle inspection obstacle avoidance system based on the zigzag millimeter wave radar in the embodiment of the invention comprises:
the device comprises a sawtooth wave transmitting module, a receiving module, a calculating module and a control module;
the sawtooth wave transmitting module comprises a sawtooth wave generator, a voltage-controlled oscillator, a power divider, a power amplifier and a transmitting antenna;
the receiving module comprises a receiving antenna, a mixer and an operational amplifier;
the calculation module obtains the frequency of the beat signal through quadrature demodulation, so as to obtain the relative distance between the obstacle and the unmanned aerial vehicle;
the control module is used for judging whether the relative distance between the obstacle and the unmanned aerial vehicle is smaller than a preset safety distance, and if the relative distance is smaller than the preset safety distance, the unmanned aerial vehicle is controlled to adjust the flight direction to be away from the obstacle.
In the embodiment of the invention, the method mainly comprises the following modules: millimeter wave radar module, binocular vision module, laser radar module, collection and transmission module, information fusion processing module, remote control receiving module, control module, wherein remote control receiving module and control module are the functional module that originally had on the unmanned aerial vehicle in the large area, do not need redesign in the system. The unmanned aerial vehicle autonomous obstacle avoidance system is shown in fig. 5.
The millimeter wave radar module transmits and receives millimeter waves and outputs beat signals; the binocular vision module is used for shooting a visual image of the obstacle; the laser radar is used for transmitting and receiving laser beams and outputting distance and angle information; the acquisition and transmission module is used for acquiring beat signals output by the millimeter wave radar module and distance and angle information of the laser radar, and transmitting the signals to the information fusion processing module; the flight parameter measurement module is used for acquiring the gesture and the height of the unmanned aerial vehicle at the current position of the unmanned aerial vehicle; the information fusion processing module is used for fusing radar ranging and binocular vision angle measurement information to make three-dimensional positioning of the obstacle and an obstacle plane distribution map; the remote control receiving module is used for receiving and decoding control signals sent by a remote control; the control module sends a flight action control signal to the unmanned aerial vehicle flight control system after the information fusion processing module finishes calculation.
The system operation process is as follows: the autonomous obstacle avoidance system firstly performs initialization work after starting up, and enters an autonomous flight state according to a flight path planned in advance after initialization; the laser radar module detects the distance of the obstacle in real time, the system does not react when the distance is larger than a set value, the binocular vision module is started to acquire visual images when the distance is smaller than a set threshold value, the information fusion processing module fuses radar information and binocular visual information to obtain three-dimensional information of the obstacle, and obstacle avoidance flight is executed according to obstacle distribution in unmanned aerial vehicle flight.
According to the invention, the distance measurement of the unmanned aerial vehicle and the obstacle is realized by utilizing the zigzag millimeter wave radar, the detection result is transmitted to the control system as a flight instruction, the flight direction and the gesture of the unmanned aerial vehicle are adjusted, the flight monitoring of the unmanned aerial vehicle on the power transmission line is completed, the safety distance between the unmanned aerial vehicle and the obstacle is kept, the stability of the shooting picture of the unmanned aerial vehicle is further ensured, and the unmanned aerial vehicle has the characteristics of high inspection efficiency, high universality, high safety and the like. Meanwhile, a certain safety distance can be set for flying obstacle avoidance, so that the operation safety of the unmanned aerial vehicle is ensured. The inspection efficiency is improved, the labor cost is greatly reduced, the delay caused by multiple connection in the data returning process and the data analysis and processing process are avoided, the information processing amount and the useless information storage and transmission are reduced, the occupation and the storage expense of the data to the network bandwidth in the transmission process are saved, and the real-time performance is good. In addition, the invention can realize data transmission in the return link as few times as possible, thus greatly reducing the consumption of funds, time and manpower in the unmanned aerial vehicle monitoring process, having important and far-reaching application prospects in the specific fields of medical treatment, military, remote sensing, navigation and the like, and having important theoretical research significance and practical application value in the fields of video monitoring, virtual reality, human-computer interaction, intelligent control and the like.
The present invention is not limited to the above-described embodiments, and if various modifications or variations of the present invention are not departing from the spirit and scope of the present invention, the present invention also includes such modifications and variations provided they fall within the scope of the claims and the equivalents thereof.
Claims (9)
1. An unmanned aerial vehicle inspection obstacle avoidance method based on a saw-tooth millimeter wave radar comprises the following steps:
obtaining a sawtooth wave modulation signal generated by a sawtooth wave generator and transmitting the sawtooth wave modulation signal to a voltage-controlled oscillator;
the voltage-controlled oscillator generates frequency-modulated continuous waves with zigzag frequency, one path of frequency-modulated continuous waves is amplified by the power amplifier and then transmitted into space, and the other path of frequency-modulated continuous waves is input into the mixer to serve as local oscillation signals;
receiving an echo signal returned by the obstacle encountered by the frequency modulation continuous wave through a receiving antenna, and sending the echo signal into a mixer;
mixing the echo signal and the local oscillation signal to form a beat signal;
the frequency of the beat signal is in direct proportion to the distance between the obstacle and the radar, and the frequency of the beat signal is calculated to obtain the relative distance between the obstacle distance and the unmanned plane;
judging whether the relative distance between the obstacle and the unmanned aerial vehicle is smaller than a set threshold distance;
and if the distance is smaller than the set threshold distance, adjusting the movement direction of the unmanned aerial vehicle to enable the unmanned aerial vehicle to move in a direction away from the obstacle.
2. The unmanned aerial vehicle inspection obstacle avoidance method based on the saw-tooth millimeter wave radar according to claim 1, wherein the unmanned aerial vehicle inspection obstacle avoidance method is characterized in that: when the saw-tooth millimeter wave radar works, two separate transmitting antennas and receiving antennas are adopted, the transmitting and receiving of millimeter waves are performed separately, and when the transmitting antennas do not transmit millimeter waves of one period, the receiving antennas start to receive echoes reflected by obstacles.
3. The unmanned aerial vehicle inspection obstacle avoidance method based on the saw-tooth millimeter wave radar according to claim 1, wherein the voltage-controlled oscillator generates a frequency modulation continuous wave with saw-tooth frequency variation, one path of frequency modulation continuous wave is amplified by the power amplifier and then transmitted into space, the other path of frequency modulation continuous wave is input into the mixer to serve as a local oscillation signal, and the frequency modulation continuous wave is different from a carrier wave for a common radar serving as the local oscillation signal, and a low-frequency signal is output after frequency mixing.
4. The unmanned aerial vehicle inspection obstacle avoidance method based on the saw-tooth millimeter wave radar according to claim 1, wherein the unmanned aerial vehicle inspection obstacle avoidance method is characterized in that: the frequency solving of the beat signal comprises the following steps:
setting the time domain pulse width of the transmitted frequency modulation continuous wave as Tp, the initial frequency as fo and the bandwidth as B, and setting the modulation frequency of the signal as K=B/Tp; the frequency modulation continuous wave is reflected by an obstacle with the distance R and is received by a receiving antenna, and compared with a transmitting signal, an echo signal received by the receiving antenna has a delay tau=2r/c; based on the delay, the frequency of the beat signal generated after mixing is fτ=kτ.
5. The unmanned aerial vehicle inspection obstacle avoidance method based on the saw-tooth millimeter wave radar, which is disclosed in claim 4, is characterized in that: the transmission signal is:
S(t)＝cos(ω o t+Kπr 2 )
the echo signal is:
S r (t)＝cos[ω o (t-τ)+Kπ(t-τ) 2 ]
the multiplication of the first echo and the local oscillation 90-degree phase shift is as follows:
output result Q of the multiplication 0 (t) low pass filtering to obtain:
the second echo is directly multiplied by the local oscillator to be I 0 (t)
Output result I of the multiplication 0 (t) low pass filtering to obtain
Combining baseband signals I and Q into a complex signal Z (t)
Fourier transforming the complex signal Z (t) to obtain
The frequency of the beat signal can thus be determined as long as the location in the frequency spectrum where the impact function delta (omega) is located is determined.
6. The unmanned aerial vehicle inspection obstacle avoidance method based on the saw-tooth millimeter wave radar according to claim 4, wherein the relationship between the frequency of the beat and the obstacle distance is:
when the parameters B and Tp are fixed, the beat frequency fτ is proportional to the distance R of the obstacle; in the millimeter wave radar system, the delay of the echo signal is negligible compared with the pulse width Tp of the transmission signal, and therefore the output beat signal is considered to contain only the frequency fτ.
7. Unmanned aerial vehicle inspection obstacle avoidance system based on zigzag millimeter wave radar, include:
the device comprises a sawtooth wave transmitting module, a receiving module, a calculating module and a control module;
the sawtooth wave transmitting module comprises a sawtooth wave generator, a voltage-controlled oscillator, a power divider, a power amplifier and a transmitting antenna;
the receiving module comprises a receiving antenna, a mixer and an operational amplifier;
the calculation module obtains the frequency of the beat signal through quadrature demodulation, so as to obtain the relative distance between the obstacle and the unmanned aerial vehicle;
the control module is used for judging whether the relative distance between the obstacle and the unmanned aerial vehicle is smaller than a preset safety distance, and if the relative distance is smaller than the preset safety distance, the unmanned aerial vehicle is controlled to adjust the flight direction to be away from the obstacle.
8. A readable storage medium having a control program stored thereon, characterized in that: the control program, when executed by the processor, implements the unmanned aerial vehicle inspection obstacle avoidance method based on the saw-tooth millimeter wave radar as set forth in any one of claims 1 to 6.
9. A computer control system comprising a memory, a processor, and a control program stored in the memory and executable by the processor, characterized in that: the unmanned aerial vehicle inspection obstacle avoidance method based on the saw-tooth millimeter wave radar according to any one of claims 1 to 6 is realized when the processor executes the control program.
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