CN109444889B - Bistatic SAR image aided driving system and method based on starry front view - Google Patents
Bistatic SAR image aided driving system and method based on starry front view Download PDFInfo
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- CN109444889B CN109444889B CN201811651712.4A CN201811651712A CN109444889B CN 109444889 B CN109444889 B CN 109444889B CN 201811651712 A CN201811651712 A CN 201811651712A CN 109444889 B CN109444889 B CN 109444889B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/904—SAR modes
- G01S13/9058—Bistatic or multistatic SAR
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
- G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/45—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement
Abstract
The invention provides an auxiliary driving system and method based on a star front view bistatic SAR image, wherein the system comprises: the satellite irradiation source launching device, the vehicle-mounted auxiliary driving device and a transmission link for communication between the satellite and the vehicle-mounted auxiliary driving device; the satellite irradiation source transmitting device flies along a satellite orbit and continuously transmits radio frequency signals to realize irradiation on a ground area, and the vehicle-mounted auxiliary driving device is used for aiming at a set area according to a preset beam direction and receiving a reflected echo of a preset target area; and the vehicle-mounted auxiliary driving device outputs auxiliary driving information according to the acquired high-resolution bistatic SAR image and the distance information of the peripheral obstacles. The invention solves the problem of road condition observation in driving under severe weather conditions, ensures that a driver can see images of roads such as mountain roads and the like under severe weather conditions, assists the driver and improves the driving safety.
Description
Technical Field
The invention belongs to the field of intelligent transportation, relates to a detection reconnaissance technology, and particularly relates to a satellite front view bistatic SAR image auxiliary driving system and method
Background
The image of the existing vehicle driving assisting device mainly depends on a camera to obtain information of the front, the side and the back of the vehicle, and is assisted with a ranging radar to monitor whether obstacles exist around the vehicle or not so as to form driving assisting information. The image obtained by the current camera has the advantages of clear image, high resolution and the like.
However, the driving assistance device based on the camera and the range radar has many disadvantages while having the advantages described above and being widely used, and under severe weather conditions such as cloudy or rainy days, clear images of the front, the side, and the rear of the vehicle cannot be obtained, so that the amount of information for assisting driving is greatly reduced.
Disclosure of Invention
In order to overcome the technical defects of the conventional driving assisting device and method, the invention provides a driving assisting system and method for a front view bistatic SAR image of a planet vehicle.
The invention provides an auxiliary driving system based on a star front view bistatic SAR image, which is characterized by comprising: the satellite irradiation source launching device, the vehicle-mounted auxiliary driving device and a transmission link for communication between the satellite and the vehicle-mounted auxiliary driving device;
the satellite irradiation source transmitting device flies along a satellite orbit and continuously transmits radio frequency signals to realize irradiation on a ground area, and the vehicle-mounted auxiliary driving device is used for aiming at a set area according to a preset beam direction and receiving a reflected echo of a preset target area;
the vehicle-mounted auxiliary driving device carries out AD sampling, digital orthogonal demodulation and pulse compression on the reflected echo, carries out motion compensation and correction and outputs a high-resolution bistatic SAR image;
and the vehicle-mounted auxiliary driving device outputs auxiliary driving information according to the acquired high-resolution bistatic SAR image and the distance information of the peripheral obstacles.
According to the system of the present invention, preferably, the satellite irradiation source transmitting device includes a first GPS module, a signal processing module, a transceiver module, a first signal source, a first synchronization system, a first attitude and heading module, and a power amplifier module;
the signal processing module is used for receiving the pulse trigger signal sent by the first synchronous system, generating a baseband signal and sending the baseband signal to a first signal source in a differential mode; the first signal source is used for generating a single-frequency signal as a carrier, carrying out IQ modulation on a received baseband signal to obtain a radio-frequency signal, and sending the radio-frequency signal to the power amplifier module; the power amplification module is used for amplifying the radio frequency signal power under the action of the switching signal and sending the amplified signal to the receiving and sending module; the receiving and transmitting module is used for receiving the radio frequency signal from the power amplification module and transmitting the radio frequency signal to the natural space according to a certain pointing angle; the first synchronous system is used for receiving the clock coherent signal from the signal processing module to realize clock coherent, and frequency division is carried out on the signal to generate a trigger pulse and the trigger pulse is returned to the signal processing module; the first attitude and heading module is used for receiving GPS signals, outputting relevant parameter data and transmitting the relevant parameter data to the first synchronization system.
According to the system of the invention, preferably, the vehicle-mounted auxiliary driving device comprises a second GPS module, a vehicle-mounted signal processing module, a vehicle-mounted transceiver module, a vehicle-mounted signal source, a second synchronization system, a second navigation attitude module and a data acquisition processing module;
the vehicle-mounted transceiver module is used for receiving radio frequency signals reflected by a target area and transmitting the radio frequency signals to the vehicle-mounted signal processing module, the vehicle-mounted signal processing module is used for processing the received radio frequency signals, the data acquisition processing module is used for sampling the processed radio frequency signals, acquiring echo signals and storing the echo signals, the data acquisition processing module is used for reading parameter data acquired by the second navigation attitude module through the two GPS modules from the second synchronization system and correspondingly inserting the parameter data into each frame of echo.
According to the system of the present invention, preferably, the satellite irradiation source emitting device and the vehicle-mounted auxiliary driving device are aligned in time/frequency by the first synchronization system and the second synchronization system, so as to ensure time-frequency synchronization.
According to the system of the invention, preferably, the satellite irradiation source transmitting device and the vehicle-mounted auxiliary driving device transmit respective position positioning information and preset target area position positioning information according to the transmission link, antenna values are resolved in a first servo module of the satellite irradiation source transmitting device and a second servo module of the vehicle-mounted auxiliary driving device, and the antennas are adjusted in real time according to a resolving result, so that space synchronization is realized.
According to the system of the invention, preferably, the vehicle-mounted auxiliary driving device further comprises a vehicle-mounted high-resolution image signal processing and auxiliary driving module, an obstacle detection module and an identification module;
the vehicle-mounted high-resolution image signal processing and driving assistance module is used for carrying out AD sampling, digital orthogonal demodulation and pulse compression on a received echo signal, carrying out motion compensation and correction and outputting a high-resolution bistatic SAR image, the obstacle detection module is used for acquiring position information of obstacles around the vehicle-mounted driving assistance device according to the SAR image, and the identification module is used for carrying out image identification according to the SAR image, judging the danger degree of the detected obstacles and carrying out real-time safety control on a vehicle where the vehicle-mounted driving assistance device is located.
According to the system of the present invention, preferably, the parameter data includes longitude and latitude, altitude, speed, heading angle, pitch angle, and GPS second pulse information.
In order to solve the technical problem, the invention discloses an auxiliary driving method based on a star-front view bistatic SAR image, which comprises the following steps:
s1, the satellite irradiation source transmitting device flies along the satellite orbit and continuously transmits radio frequency signals to realize irradiation on the ground area;
s2, the vehicle-mounted auxiliary driving device is aligned to a set area according to a preset beam direction, and a reflected echo of a preset target area is received;
and S3, outputting driving assistance information according to the acquired high-resolution bistatic SAR image and the distance information of the peripheral obstacles.
According to the method of the present invention, preferably, the step S1 is preceded by aligning the satellite illumination source emitting device and the vehicle-mounted auxiliary driving device in terms of time/frequency through respective synchronization systems, so as to ensure time-frequency synchronization.
According to the method, preferably, after time/frequency alignment is carried out and time synchronization is ensured, the satellite irradiation source transmitting device and the vehicle-mounted auxiliary driving device transmit respective position positioning information and preset target area position positioning information according to the transmission link, antenna value calculation is carried out, the antenna is adjusted in real time according to a calculation result, and space synchronization of the satellite and the automobile is achieved.
According to the method of the present invention, preferably, the satellite illumination source emitting device in step S1 further includes, before emitting the radio frequency signal,
s1.1, generating a baseband signal according to a pulse trigger signal;
s1.2, carrying out IQ modulation on the received baseband signal to obtain a radio frequency signal;
s1.3, amplifying the power of the radio frequency signal under the action of the switching signal, and sending the amplified radio frequency signal to a ground area to realize irradiation on the ground area.
According to the method of the present invention, preferably, the step S2 further includes, when receiving the transmission echo,
s2.1, receiving the radio frequency signal reflected by the target area in real time,
and S2.2, processing the received radio frequency signal to obtain a relatively pure intermediate frequency signal, and accurately acquiring an echo digital signal by triggering control signal delay and sampling.
According to the method of the present invention, preferably, the step S3 of obtaining the high resolution bistatic SAR image according to the echo signal includes performing AD sampling, digital quadrature demodulation, pulse compression, motion compensation and correction on the received echo signal, and outputting the high resolution bistatic SAR image.
According to the method of the present invention, after the step S3, the method preferably further includes acquiring position information of a vehicle-mounted driving assistance device according to the SAR image, detecting information of a risk level of an obstacle, and performing safety control on a vehicle where the vehicle-mounted driving assistance device is located.
By adopting the satellite front view bistatic SAR image auxiliary driving system and method, the all-weather front view imaging of the automobile is realized in a transceiving split mode, the all-weather, all-day and whole-course high-resolution imaging navigation capability is formed, the problem that the front road condition cannot be clearly seen in driving under severe weather conditions such as severe haze, cloudy or rainy days is solved, particularly the problem of road condition observation in driving on a mountain road is solved, the driver can be ensured to see the images of roads such as the mountain road under the severe weather conditions, the driver is assisted, and the driving safety is improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram of driving assistance work of a satellite front view bistatic SAR image;
FIG. 2 is a block diagram of a satellite front view bistatic SAR image assisted driving device;
fig. 3 is a flow chart of a star front view bistatic SAR image assisted driving method.
Detailed Description
The preferred embodiments of the present invention will be described below with reference to the accompanying drawings of the specification, it being understood that the preferred embodiments described herein are merely for illustrating and explaining the present invention, and are not intended to limit the present invention, and that the embodiments and features of the embodiments in the present invention may be combined with each other without conflict.
According to an embodiment of the invention, as shown in fig. 1 and fig. 2, the invention provides a driving assistance system based on a spaceship forward-looking bistatic SAR image, which comprises a satellite radiation source transmitting device, an on-board driving assistance device positioned on an automobile and a transmission link for communication between a satellite and the on-board driving assistance device.
The satellite irradiation source transmitting device provided by the invention can be a specially designed cooperative signal source with ideal transmitting power, large signal bandwidth and synchronous characteristics as a transmitting end of a signal irradiation source, and can also be a non-cooperative signal source such as a broadcast television satellite, a data communication satellite or a navigation satellite. It can be known from the current development of bistatic systems that the current GPS navigation is still the key technology for the current research of bistatic SAR technology, so the satellite irradiation source transmitting device of the present invention uses a GPS navigation system, and further comprises a signal processing module, a transceiver module, a first signal source, a first synchronization system, a first attitude module, and a power amplifier module. The vehicle-mounted auxiliary driving device comprises a second GPS module, a vehicle-mounted signal processing module, a vehicle-mounted receiving and transmitting module, a vehicle-mounted signal source, a second synchronization system, a second navigation attitude module, a data acquisition and processing module, a vehicle-mounted high-resolution image signal processing and auxiliary driving module, an obstacle detection module, an identification module and a display module.
The signal processing module is used for receiving the pulse trigger signal sent by the first synchronization system, generating a baseband signal with a certain specification, dividing the baseband signal into I, Q two paths of signals, performing resolution modulation, and sending the signals to the first signal source in a differential mode. Meanwhile, in order to realize clock coherence, the signal processing module is also used for transmitting a high-precision coherent clock signal from a first signal source to a first synchronous system, so that the clock coherence of the signal processing module is realized, and in addition, according to the characteristic of time delay of the system, the pulse trigger signal is delayed to generate a MARKER signal which is used as a power amplifier switch signal.
The first signal source generates a single-frequency signal as a carrier, the received baseband signal is subjected to IQ modulation to obtain a radio-frequency signal, and the radio-frequency signal is sent to the power amplifier module; the power amplifier only needs to amplify signals in a short time due to small signal time width and duty ratio, and when the switching signal is at a high level, the power amplifier amplifies the signals, otherwise the power amplifier stops working, so that the power amplifier module is used for amplifying the radio frequency signal power under the action of the switching signal and sending the amplified signals to the transceiver module.
In the invention, the bistatic SAR technology needs to calibrate time frequency and realize time synchronization, and simultaneously needs to carry out space synchronization, so the satellite irradiation source device comprises a first synchronization system, and a second synchronization system is arranged in an auxiliary driving device of an automobile.
In order to realize the synchronization of a transmitting end and a receiving end, a first attitude heading module and a second attitude heading module are respectively arranged in a satellite irradiation device and an auxiliary driving device, the first attitude heading module and the second attitude heading module play roles of receiving GPS signals and outputting respective information such as longitude, latitude, altitude, platform speed, course angle, pitch angle, GPS second pulse and the like, a first synchronization system and a second synchronization system respectively receive respective data of the first attitude heading module and the second attitude heading module, and after calculation, the space synchronization and time-frequency synchronization between the two devices are realized through a control antenna.
In the invention, the purpose of the invention is to obtain a clear image of a target area around an automobile, therefore, a vehicle-mounted high-resolution image signal processing and driving assisting module is arranged in a driving assisting device, in the content, the time-frequency synchronization and the space synchronization of a satellite irradiation device and the automobile are realized, the satellite irradiation device transmits radio-frequency signals to the ground in real time, and the automobile forms an image according to echo signals reflected by the target area.
In the actual automobile operation, on one hand, image information of a target area is grasped in real time, and meanwhile, as the automobile operation belongs to an automatic driving state and has no real-time control on peripheral obstacles during artificial control, an obstacle detection module is further arranged in the invention and is used for acquiring position information of the obstacles according to an SAR image, judging the danger degree of the obstacles according to an identification module arranged on the obstacle detection module, and setting different avoidance strategies according to different danger degree information.
According to an embodiment of the invention, as shown in fig. 3, the invention provides a region sensing identification method based on a spaceship forward-looking bistatic SAR image, which comprises the following steps:
s1, the satellite irradiation source transmitting device flies along the satellite orbit and continuously transmits radio frequency signals to realize irradiation on the ground area;
s2, the driving assistance device of the automobile aims at the set area according to the preset beam direction and receives the reflected echo of the preset target area;
and S3, acquiring a high-resolution bistatic SAR image according to the echo signal.
In the invention, the problem to be solved in the process of realizing the method is how to realize the stable and effective operation of the bistatic SAR system. Because the radar of the transmitting end and the receiving end of the bistatic SAR are respectively arranged on different carrier platforms and respectively use independent frequency sources, on one hand, the transmitting end and the receiving end adopt respective trigger pulses to trigger to generate transmitting and receiving time sequences, so that the received and sent signals cannot be strictly aligned in the time sequences, and the problem of time synchronization is generated; on the other hand, the carrier frequency signal of the transmitter is not related to the local oscillation signal of the receiver, and any frequency deviation between the frequency sources of the receiving end and the transmitting end and instability of the output frequency will cause phase error of the demodulated echo signal, thereby affecting the focusing effect. In addition, the difference between the flight speed of the satellite and the operation speed of the vehicle will limit the coverage area, so it is necessary to take measures to improve the overlapping time of the beams at the receiving end and the transmitting end as much as possible, and further improve the length of the imaging scene.
In the invention, the synchronization of the satellite and the automobile is realized, and the synchronization comprises three parts, namely time frequency synchronization and space synchronization, wherein the time frequency synchronization is time synchronization and frequency synchronization.
Step S1 is preceded by aligning the satellite illumination source emitting device with the driving assistance device of the automobile by respective synchronization systems to ensure time and frequency synchronization.
In time synchronization, three parameters, a reference time point, a distance between a receiving end and a transmitting end corresponding to the reference time point, and a pulse repetition period of a transmitting device need to be accurately estimated, so that one-dimensional echo data are converted into a two-dimensional echo matrix. In the invention, the shortest distance time from the satellite to the automobile is used as reference time, and the distance between the receiving end and the transmitting end is calculated by utilizing the track signal and the position information of the automobile receiving end. According to the satellite orbit and the ephemeris data, the predicted zero reference time point is taken as a time zero point to obtain the linear distance from the satellite to the automobile receiving end, and the distances between the satellite and the automobile receiving end at different time points are obtained based on different time points. The method comprises the following steps: (1) performing pulse compression on the direct wave, and extracting peak phase information; (2) eliminating phase information introduced by an ideal distance process in the extracted peak phase;
(3) estimating and eliminating a linear phase in the residual phase, and mainly retaining a low-frequency component in the residual phase;
(4) and on the basis of the third step, block phase entanglement is carried out on the residual phase, M-order polynomial fitting is carried out on the phase after unwrapping, phase derivative values corresponding to the central moments of all lobes are calculated, the real direct wave distance process is estimated, Doppler time is estimated according to the difference between the actual distance process and the ideal distance process, the time is taken as a time reference point, and finally the distance between the satellite and the automobile is calculated.
In video synchronization, namely a high-precision local frequency source is adopted, a remote time reference signal is used for calibrating the local frequency source in a period of time, the error is ensured to be within an allowable range in a time interval, time-frequency synchronization is divided into three parts, and a local clock source, a standard clock signal and a clock source are calibrated.
SAR processing is a coherent processing process, and frequency synchronization is the basis for realizing SAR coherent processing. Because the local oscillation signals of the transmitting and receiving systems are different due to the separate arrangement of the transmitting and receiving systems, a phase error is introduced in the demodulation process of the receiving end, so that the coherence of the echo signals is difficult to ensure. The frequency synchronization technology can eliminate phase errors introduced by different local oscillator signals of the receiving and transmitting system as much as possible, thereby achieving the purpose of coherent processing. Which comprises the following steps: performing distance compression on the direct wave data matrix; providing a peak signal with the strongest sampling pulse amplitude in the direct wave matrix to form a peak signal vector; the direct wave distance process can be accurately reconstructed by utilizing the accurate estimation of the zero Doppler time in the time synchronization and combining with the satellite orbit data, so that the phase of the direct wave distance process is obtained; and extracting the phase of the 'peak signal' vector, and eliminating the phase introduced by the direct wave distance process to obtain the required frequency synchronization error. And compensating the frequency synchronization errors in the direct wave matrix and the echo matrix.
After time/frequency alignment is carried out and time synchronization is ensured, the satellite irradiation source transmitting device and the auxiliary driving device of the automobile transmit respective position positioning information and preset target area position positioning information according to the transmission link, antenna value calculation is carried out, an antenna is adjusted in real time according to a calculation result, and space synchronization of the satellite and the automobile is achieved.
The satellite illumination source transmitting device in the step S1 further includes before transmitting the radio frequency signal,
s1.1, generating a baseband signal according to a pulse trigger signal;
s1.2, carrying out IQ modulation on the received baseband signal to obtain a radio frequency signal;
s1.3, amplifying the power of the radio frequency signal under the action of the switching signal, and sending the amplified radio frequency signal to a ground area to realize irradiation on the ground area.
The step S2 further includes when receiving the transmission echo,
s2.1, receiving the radio frequency signal reflected by the target area in real time,
and S2.2, processing the received radio frequency signal to obtain a relatively pure intermediate frequency signal, and accurately acquiring an echo digital signal by triggering control signal delay and sampling.
In the present invention, the target area includes a stationary target area and a moving target area.
If the target area is moving, the slope distance history R (t) of the system is expressed as follows:
wherein R ist0Synthetic aperture center time satellite launch device slope distance, Rr0For the moment of the centre of the synthetic aperture of the slope, v, of the car receivertIs the satellite velocity, vrAs the speed of the vehicle, thetatIn order to obtain an oblique view of the satellite launch device,
the front view angle of the receiving end of the automobile is shown, and t is the azimuth time.
The expression of the acquired echo signal is:
wherein c is the speed of light, ωr(τ) and ωa(t) respectively, a range-wise signal envelope and an azimuth-wise signal envelope, Krτ is the distance versus time to tune the frequency of the signal.
For a stationary object, the moving object may be set to zero.
The step S3 of obtaining the high resolution bistatic SAR image according to the echo signal includes performing AD sampling, digital orthogonal demodulation, pulse compression on the received echo signal, performing motion compensation and correction, and outputting the high resolution bistatic SAR image.
The algorithm process for obtaining the image in the step 3 is that in the bistatic forward-looking SAR system, the algorithm process is generally used for small-area detection imaging, and during imaging processing, the reference distance R is firstly takenrefThe compensation function of the focus lens compensates the dual-base additional term and then performs focusing processing
At this time, the echo signal has a frequency spectrum of
In the formula (f)aIs the directional frequency, frIs the range frequency.
And performing range direction and azimuth direction Fourier transformation on the received echo signals, performing double-base phase and high-order coupled phase compensation, range compression and secondary compression, performing range direction Fourier transformation and range migration correction again, and finally performing direction position compression and direction Fourier transformation to obtain an imaging result.
And after the step S3, acquiring position information of obstacles around the vehicle according to the SAR image, detecting information of a risk degree of the obstacles, and performing safety control.
In the invention, the content before the third step is the process of obtaining the image, and the image needs to be analyzed and processed after being obtained, which includes the detection of the peripheral state of the automobile, whether an obstacle exists, the position information of the obstacle and whether the obstacle forms a threat or a danger, if the obstacle exists, the danger information needs to be analyzed, what the danger degree is, and the automobile is controlled in real time. This improves the safety of the vehicle during its actual operation.
By adopting the device and the method for sensing and identifying the forward-looking bistatic SAR image of the spaceship, all-weather forward-looking imaging of the automobile can be realized in a transceiving split mode, all-weather, all-time and whole-course high-resolution imaging sensing and identifying capabilities are formed, the problem that the front ground of the automobile cannot be seen clearly under severe weather conditions such as a ground environment, cloudy days or rainy days is solved, the automobile can sense peripheral images and identify peripheral dangerous obstacles under the severe weather conditions, and the safety of automobile operation is improved.
It will be evident to those skilled in the art that the embodiments of the present invention are not limited to the details of the foregoing illustrative embodiments, and that the embodiments of the present invention are capable of being embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the embodiments being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it is obvious that the word "comprising" does not exclude other elements or steps, and the singular does not exclude the plural. Several units, modules or means recited in the system, apparatus or terminal claims may also be implemented by one and the same unit, module or means in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the embodiments of the present invention and not for limiting, and although the embodiments of the present invention are described in detail with reference to the above preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the embodiments of the present invention without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A driving assistance system based on a starcar front view bistatic SAR image, the system comprising: the satellite irradiation source launching device, the vehicle-mounted auxiliary driving device and a transmission link for communication between the satellite and the vehicle-mounted auxiliary driving device;
the satellite irradiation source transmitting device flies along a satellite orbit and continuously transmits radio frequency signals to realize irradiation on a ground area, and the vehicle-mounted auxiliary driving device is used for aiming at a set area according to a preset beam direction and receiving a reflected echo of a preset target area;
the satellite irradiation source transmitting device comprises a first GPS module, a signal processing module, a transceiving module, a first signal source, a first synchronization system, a first attitude navigation module and a power amplification module;
the signal processing module is used for receiving the pulse trigger signal sent by the first synchronous system, generating a baseband signal and sending the baseband signal to a first signal source in a differential mode; the first signal source is used for generating a single-frequency signal as a carrier, carrying out IQ modulation on a received baseband signal to obtain a radio-frequency signal, and sending the radio-frequency signal to the power amplifier module; the power amplification module is used for amplifying the radio frequency signal power under the action of the switching signal and sending the amplified signal to the receiving and sending module; the receiving and transmitting module is used for receiving the radio frequency signal from the power amplification module and transmitting the radio frequency signal to the natural space according to a certain pointing angle; the first synchronous system is used for receiving the clock coherent signal from the signal processing module to realize clock coherent, and frequency division is carried out on the signal to generate a trigger pulse and the trigger pulse is returned to the signal processing module; the first attitude and heading module is used for receiving GPS signals, outputting related parameter data and transmitting the related parameter data to the first synchronization system;
the parameter data comprises longitude and latitude, altitude, speed, course angle, pitch angle and GPS second pulse information;
the vehicle-mounted auxiliary driving device comprises a second GPS module, a vehicle-mounted signal processing module, a vehicle-mounted receiving and transmitting module, a vehicle-mounted signal source, a second synchronization system, a second attitude and heading module and a data acquisition and processing module;
the vehicle-mounted transceiver module is used for receiving radio frequency signals reflected by a target area and transmitting the radio frequency signals to the vehicle-mounted signal processing module, the vehicle-mounted signal processing module is used for processing the received radio frequency signals, the data acquisition processing module is used for sampling the processed radio frequency signals to acquire echo signals and then storing the echo signals, the data acquisition processing module is used for reading parameter data acquired by the second attitude and heading module through the two GPS modules from the second synchronous system and correspondingly inserting the parameter data into each frame of echo;
the satellite irradiation source launching device and the vehicle-mounted auxiliary driving device align time/frequency through the first synchronization system and the second synchronization system to ensure time-frequency synchronization;
the target area comprises a static target area and a moving target area;
for the moving target area, the slope distance history R (t) of the driving assistance system is as follows:
wherein R ist0For the slant range, R, of the synthetic aperture central time satellite transmitterr0For the moment of the centre of the synthetic aperture of the slope, v, of the car receivertIs the satellite velocity, vrAs the speed of the vehicle, thetatIn order to obtain an oblique view of the satellite launch device,
the front view angle of the automobile receiving end is shown, and t is the azimuth time;
for a static target area, setting the moving target to zero;
the expression for the echo is:
whereinC is the speed of light, omegar(τ) and ωa(t) respectively, a range-wise signal envelope and an azimuth-wise signal envelope, KrAdjusting the frequency of the signal, wherein tau is the distance time, and lambda is the wavelength of the signal;
the vehicle-mounted auxiliary driving device carries out AD sampling, digital orthogonal demodulation and pulse compression on the reflected echo, carries out motion compensation and correction and outputs a high-resolution bistatic SAR image;
and the vehicle-mounted auxiliary driving device outputs auxiliary driving information according to the acquired high-resolution bistatic SAR image and the distance information of the peripheral obstacles.
2. The system according to claim 1, wherein the satellite irradiation source transmitting device and the vehicle-mounted auxiliary driving device transmit respective position positioning information and preset target area position positioning information according to the transmission link, antenna value calculation is performed in a first servo module of the satellite irradiation source transmitting device and a second servo module of the vehicle-mounted auxiliary driving device, and an antenna is adjusted in real time according to a calculation result to achieve spatial synchronization.
3. The system according to claim 2, wherein the vehicle-mounted driving assistance device further comprises a vehicle-mounted high-resolution image signal processing and driving assistance module, an obstacle detection module and an identification module;
the vehicle-mounted high-resolution image signal processing and driving assistance module is used for carrying out AD sampling, digital orthogonal demodulation and pulse compression on a received echo signal, carrying out motion compensation and correction and outputting a high-resolution bistatic SAR image, the obstacle detection module is used for acquiring position information of obstacles around the vehicle-mounted driving assistance device according to the SAR image, and the identification module is used for carrying out image identification according to the SAR image, judging the danger degree of the detected obstacles and carrying out real-time safety control on a vehicle where the vehicle-mounted driving assistance device is located.
4. A method of assisted driving based on bistatic SAR images, using an assisted driving system according to one of claims 1 to 3, characterized in that it comprises the following steps:
s1, the satellite irradiation source transmitting device flies along the satellite orbit and continuously transmits radio frequency signals to realize irradiation on the ground area;
s2, the vehicle-mounted auxiliary driving device is aligned to a set area according to a preset beam direction, and a reflected echo of a preset target area is received;
the target area comprises a static target area and a moving target area;
for the moving target area, the slope distance history R (t) of the driving assistance system is as follows:
wherein R ist0For the slant range, R, of the synthetic aperture central time satellite transmitterr0For the moment of the centre of the synthetic aperture of the slope, v, of the car receivertIs the satellite velocity, vrAs the speed of the vehicle, thetatIn order to obtain an oblique view of the satellite launch device,
the front view angle of the automobile receiving end is shown, and t is the azimuth time;
for a static target area, setting the moving target to zero;
the expression for the echo is:
wherein c is the speed of light, ωr(τ) and ωa(t) respectively, a range-wise signal envelope and an azimuth-wise signal envelope, KrAdjusting the frequency of the signal, wherein tau is the distance time, and lambda is the wavelength of the signal;
s3, outputting driving assistance information according to the acquired high-resolution bistatic SAR image and distance information of surrounding obstacles;
before the step S1, the method further includes: the satellite irradiation source launching device and the vehicle-mounted auxiliary driving device align time/frequency through respective synchronization systems to ensure time-frequency synchronization.
5. The method according to claim 4, wherein after time/frequency alignment and time synchronization is ensured, the satellite irradiation source transmitting device and the vehicle-mounted auxiliary driving device transmit respective position positioning information and preset target area position positioning information according to a transmission link for communication therebetween, and perform antenna value calculation, and adjust an antenna in real time according to a calculation result to realize space synchronization between the satellite and the vehicle.
6. The method according to claim 5, wherein the satellite illumination source emitting device in step S1 further comprises, before emitting the radio frequency signal,
s1.1, generating a baseband signal according to a pulse trigger signal;
s1.2, carrying out IQ modulation on the received baseband signal to obtain a radio frequency signal;
s1.3, amplifying the power of the radio frequency signal under the action of the switching signal, and sending the amplified radio frequency signal to a ground area to realize irradiation on the ground area.
7. The method according to claim 6, wherein the step S2 further comprises, when receiving the transmission echo,
s2.1, receiving the radio frequency signal reflected by the target area in real time,
and S2.2, processing the received radio frequency signal to obtain a relatively pure intermediate frequency signal, and accurately acquiring an echo digital signal by triggering control signal delay and sampling.
8. The method as claimed in claim 7, wherein the step S3 of obtaining the high resolution bistatic SAR image according to the echo signal comprises performing AD sampling, digital quadrature demodulation, pulse compression, motion compensation and correction on the received echo signal, and outputting the high resolution bistatic SAR image.
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