CN109031307A - Vehicle-mounted millimeter wave anti-collision radar system and obstacle detection method - Google Patents
Vehicle-mounted millimeter wave anti-collision radar system and obstacle detection method Download PDFInfo
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- 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
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- 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
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Abstract
The present invention provides a kind of vehicle-mounted millimeter wave anti-collision radar systems characterized by comprising transmitting radar portion emits radar signal to target area；Direction-finding signal control unit, control transmitting radar cell issue direction-finding signal；First receives radar portion, receives first echo signal caused by direction-finding signal；Reflection coefficient analysis portion, analyzes first echo signal, obtains the reflection coefficient distribution in target area；Barrier judgment portion, according to whether there are obstacles in all directions of reflection coefficient distribution and scheduled reflection coefficient threshold decision target area in target area；Distance measuring signal control unit, control transmitting radar cell issue distance measuring signal；Second receives radar portion, receives second echo signal caused by distance measuring signal；And distance analysis portion, analysis is carried out to second echo signal and obtains the distance between barrier and car body.The present invention also provides corresponding barrier measurement methods.
Description
Technical Field
The invention relates to a radar system, in particular to a vehicle-mounted millimeter wave anti-collision radar system and an obstacle detection method.
Background
The vehicle-mounted anti-collision radar is used for measuring the obstacles in the area around the vehicle body to obtain the existence direction and distance of the obstacles, so that the vehicle control system can perform corresponding operation or give related prompts to a driver according to the existence condition of the obstacles.
The angle measurement of the vehicle-mounted anti-collision radar refers to direction finding of a target field around a vehicle body to obtain the position of an obstacle, and common methods of the angle measurement include an amplitude method, a phase method, a Doppler method and the like. The direction finding by the amplitude method is more common, the direction finding by the amplitude method is in a form that the direction characteristic of an antenna is utilized, the direction of an incoming wave is determined by measuring the amplitude of an incoming wave signal, and the method is simple and easy to implement but has larger error; the phase method direction finding adopts two separated antenna units to have wave path difference on incoming wave signals receiving the same radiation source, so that phase difference is generated, direction finding is carried out based on the phase difference, the precision is high, but the direction finding range is narrow due to the phase ambiguity problem; the doppler direction finding is performed based on the doppler change rate, and has a small error and high sensitivity, but it is impossible to perform multi-beam direction finding, and the means for measuring the doppler change rate is limited, and it is still difficult to achieve ideal accuracy.
The direction finding process of radar also involves sampling the signal. In the conventional sampling theory, the signal is considered to be continuously generated and infinite in length, data acquisition needs to be performed by sampling at a specified time point, and meanwhile, the reconstruction of the measurement signal is usually realized by interpolation by using a sinc function. Therefore, the direction-finding method based on the traditional sampling theory has a good processing effect on single-point transceiving measurement, and multi-point transmission is easy to be incapable of accurately reconstructing due to the fact that data is large, complex and irregular. Since the general radar direction finding resolution is limited by the rayleigh limit, which mainly depends on the antenna aperture, and the direction finding method of the single-point transceiving type cannot achieve high resolution, it is difficult for the conventional direction finding method to simultaneously achieve high-precision and wide-range measurement both from the measurement theory and from the calculation theory.
Disclosure of Invention
In order to solve the problems, the invention provides a vehicle-mounted millimeter wave anti-collision radar system and a corresponding obstacle detection method, wherein the vehicle-mounted millimeter wave anti-collision radar system can realize high precision, wide range obstacle direction finding and obstacle distance measurement, and adopts the following technical scheme:
the invention provides a vehicle-mounted millimeter wave anti-collision radar system which is arranged on an automobile and used for direction finding and distance measuring of obstacles in a target area around an automobile body, and is characterized by comprising the following components: the radar transmitting part is provided with Q radar transmitting units which are arranged in an array manner and used for transmitting radar signals to a target area; a direction-finding signal control part which controls the transmitting radar unit to send out a direction-finding signal for direction-finding of the obstacle according to a preset direction-finding signal control mode; a first receiving radar unit having R first receiving radar units for receiving a first echo signal generated by the direction-finding signal; a reflection coefficient analysis unit for analyzing the first echo signal to obtain a reflection coefficient distribution in the target region; an obstacle determination unit that determines whether an obstacle exists in each direction of the target area based on the reflection coefficient distribution in the target area and a predetermined reflection coefficient threshold; a ranging signal control part for controlling the transmitting radar unit to transmit a ranging signal for ranging the obstacle according to a predetermined ranging signal control mode; a second receiving radar unit that receives a second echo signal generated by the ranging signal; and a distance analysis unit for analyzing the second echo signal to obtain a distance between the obstacle and the vehicle body, wherein the control matrix a is calculated according to the following formula:in the formula,is an amplitude modulation matrix containing Q random amplitude control functions corresponding to Q radar transmitting units, f is a frequency modulation matrix containing Q random frequency control functions corresponding to Q radar transmitting units, and p is a phase modulation matrix containing Q random phase control functions corresponding to Q radar transmitting units.
The invention provides a vehicle-mounted millimeter wave anti-collision radarThe system may further include a feature in which the direction-finding signal control unit includes: a mesh dividing unit dividing the target area into M × N meshes; a function storage unit for storing a propagation function H reflecting intensity variation of the signal emitted by the radar emission unit projected to each grid of the direction finding area1And an echo function H reflecting the intensity variation of the first echo signal generated by each grid propagating to the R receiving radar units2(ii) a A control matrix setting unit which sets a control matrix A containing Q control functions corresponding to the Q radar transmitting units and respectively enabling the Q radar transmitting units to transmit random amplitude-phase transmitting signals; and a signal control unit for controlling the radar emission unit to emit direction-finding signals according to the control matrix A, respectively, the reflection coefficient analysis unit being based on the propagation function H1And echo function H2And the control matrix A analyzes the first echo signal to obtain a reflection matrix x containing reflection coefficients corresponding to the grids respectively as the distribution of the reflection coefficients.
The vehicle-mounted millimeter wave anti-collision radar system provided by the invention can also have the technical characteristics that the range of Q is 4-16, and the range of R is 1-8.
The vehicle-mounted millimeter wave anti-collision radar system provided by the invention can also have the technical characteristics that the amplitude modulation matrix isAs shown in the following formula:
wherein,to satisfy a pseudo-random sequence of a gaussian distribution, τ is the sequence index in the time dimension.
The vehicle-mounted millimeter wave anti-collision radar system provided by the invention can also have the technical characteristics that: and the control part controls the direction-finding signal control part to control the transmitting radar part to send n frames of direction-finding signals, and further controls the ranging signal control part to control the ranging signal control part to send 1 frame of ranging signals.
The vehicle-mounted millimeter wave anti-collision radar system provided by the invention can also have the technical characteristics that: and a control part for controlling the ranging signal control part when the obstacle judgment part judges that the obstacle exists in the target area, so that the ranging signal control part controls the transmitting radar part to send out 1 frame of ranging signals.
The invention also provides a method for detecting the obstacles in the vehicle-mounted millimeter wave anti-collision radar system, which is used for carrying out direction finding and distance measuring on the obstacles in the target area around the vehicle body, and is characterized by comprising the following steps:
step S1, dividing the direction-finding area into N parts in the horizontal direction and M parts in the vertical direction by adopting a grid dividing unit to obtain M multiplied by N grids;
step S2, adopting a direction-finding signal control part to control Q transmitting radar units arranged in a matrix form to transmit direction-finding signals to a target area according to a control matrix A;
step S3, a first echo signal formed after the direction-finding signal is projected to the target area is received by the first receiving radar part;
step S4, analyzing the reflection coefficient distribution of the target area according to the first echo signal by using a reflection coefficient analysis part;
step S5, judging whether there is an obstacle in each direction of the target area by the obstacle judging part according to the reflection coefficient distribution and the preset reflection coefficient threshold;
step S6, a ranging signal control part is adopted to control the transmitting radar part to transmit ranging signals;
step S7, a second receiving radar part is adopted to receive a second echo signal formed after the ranging signal is projected to the target area;
step S8, adopting the distance analysis part to analyze the distance of the obstacle,
wherein, the control matrix A is calculated according to the following formula:
in the above formula, the first and second carbon atoms are,is an amplitude modulation matrix containing Q random amplitude control functions corresponding to Q radar transmitting units, f is a frequency modulation matrix containing Q random frequency control functions corresponding to Q radar transmitting units, and p is a phase modulation matrix containing Q random phase control functions corresponding to Q radar transmitting units.
Action and Effect of the invention
According to the vehicle-mounted millimeter wave anti-collision radar system and the obstacle detection method provided by the invention, the direction-finding signal control part adopts the matrix which corresponds to Q transmitting radar units and contains random amplitude modulationThe random frequency modulation matrix f and the control matrix A of the random phase modulation matrix p control signals transmitted by the transmitting radar unit, so that the transmitting radar unit transmits pseudo-hot signals, the correlation between the control matrix A and received signals is reduced, and further, a compressed sensing algorithm can be applied to direction finding of the millimeter wave radar, therefore, after corresponding echo signals are measured, a reflection coefficient matrix of a direction finding area can be obtained through a reconstruction method based on compressed sensing, and whether obstacles exist in the corresponding direction is further judged according to reflection coefficients corresponding to grids in the reflection coefficient matrix.
Drawings
FIG. 1 is a schematic diagram of the position relationship of a transmitting radar and a direction finding area of the present invention;
fig. 2 is a configuration diagram of a vehicle-mounted millimeter wave collision avoidance radar system of the embodiment of the present invention;
FIG. 3 is a schematic diagram of a direction-finding signal control section according to an embodiment of the present invention;
fig. 4 is a flow chart of obstacle detection of the vehicle-mounted millimeter wave collision avoidance radar system according to the embodiment of the present invention.
Detailed Description
The following describes embodiments of the present invention with reference to the drawings.
< example >
The inventor of the invention finds that in the vehicle-mounted anti-collision millimeter wave radar, the direction finding with high precision and wide range can be realized by combining the multipoint emission type radar with the compressed sensing, and the theoretical basis is as follows.
Firstly, the compressed sensing utilizes the phenomenon that a natural signal can be expanded under an appropriate base Ψ to obtain a compact and sparse representation, and the original signal is compressed during sampling or sensing and reconstructed by using the base Ψ. Therefore, the implementation of compressed sensing relies mainly on two points: firstly, the signals needing to be processed have sparseness, and secondly, the perception form and the expression form have irrelevancy. Where for a discrete-time signal sparsity implies that the degrees of freedom on which it depends are much smaller than its (finite) length, while non-correlation requires that the sampled or perceived signal waveform has a dense representation at the basis Ψ.
Secondly, the inventor finds that in the multi-point emission type radar direction finding process, the combination of all the emission radar units is regarded as a matrix, the signals of the emission radar units are modulated according to the form of a random phase matrix, pseudo-thermal emission signals can be obtained, the return signals generated by the emission signals on a target are received by at least one receiving radar unit to obtain the return signals which satisfy sparsity, and the random phase matrix and the received return signals also satisfy non-correlation. The method comprises the following specific steps:
the transmitting radar antennas (i.e., transmitting radar units) are arranged in an array. The transmitting radar antenna is assumed to be composed of Q antenna sub-array units, and the directional diagram of each sub-array unit is Ft(. cndot.). The transmission of the Q antenna subarray units is controlled by a control matrix, signals with pseudo-random distribution of amplitude, phase and frequency are generated, the signals are projected onto an object plane, and field distribution signals with random distribution are generated on the object plane, as shown in the following formula (1):
wherein, FtDenotes the single antenna radiation field function, each array antenna position is defined as ri' (i is 1 to Q), A is a signal modulation system, and f0Is the signal transmission frequency.
FIG. 1 is a schematic diagram of the position relationship of the transmitting radar and the direction finding area of the present invention.
The rectangular coordinate system ozxyz shown in fig. 1 shows the positional relationship between the transmitting radar and the direction-finding region (object plane).
The Q radiation sources (i.e. transmitting radar units) generate control signals of random amplitude and phase under random amplitude, phase and frequency control. Let the ith cell be located at the emission plane as (x)i,yi,zi) And the radiation signal of the ith cell at time t is as shown in the following formula (2):
Si(t)＝Aiexp(jωit+φi) (2)
the direction of the sub-array unit is shown as F (theta)α,θβ) Shown, wherein:
at this time, the unit i pair is located on the object plane (x)i,yi,zi) The incident signal at the position is shown in the following equation (3):
on the object plane (x)i,yi,zi) The position space radiation function is shown in the following equation (4):
when the direction-finding region S is divided into grids, i.e., the equal-interval distribution of M grids in the horizontal direction and N grids in the vertical direction, the incident signal of any grid on the direction-finding region S can be represented by a two-dimensional matrix of M × N or converted into a one-dimensional vector of MN × 1 in time t. The time dimension is increased, and the matrix can be represented by an M multiplied by N multiplied by K matrix or an MN multiplied by K matrix.
According to the approximate representation of the radiation field and the scattering field after the target acts on, and through the mapping of a Green function, the target backscattering field is obtained as shown in the following formula (5):
where S denotes the measurement area, σrTaking a backscattering coefficient at an arbitrary position r in the measurement region, wherein G (r) is a Green function of free space; finally, assume that the random noise in the received echo signal is enTaking into account the distribution function F of the radiation field of the receiving elementsr(. a), and an objectMotion-generated coupling influence factor K (v)t) The finally received radar incident field characterization based on the space-time two-dimensional randomness characterization can be characterized in a form shown in the following formula (6):
En＝K(vt)Ercs(t,r0')Fr(t,r-ri')+en(6)
wherein v istRepresenting three-dimensional velocity vectors of object motion, v for objects in a stationary scenet＝[0,0,0]. That is, for a typical application scenario, such as the above-mentioned on-board millimeter wave collision avoidance radar, the three-dimensional velocity vector of the target motion may not be considered because the obstacle is stationary or relatively stationary.
Describing the target scene in a discrete spatial domain, the target scene can be regarded as scattering points on a grid, the finer the grid is, the finer the scene is, and the specific grid division number can be set according to actual requirements (for example, the approximate size of an obstacle). Accordingly, the reflection coefficient on the grid can be represented by a two-dimensional matrix as shown in the following equation (7):
the matrix is an M × N matrix, M, N are the number of lattice points on the X axis and Y axis of the target, respectively, and can also be represented as an MN × 1 vector by a one-dimensional column vector.
After the transmission signal is received, the back scattering echo from each discrete point position in the direction-finding area is expressed by an echo vector as the product of each point on the reflection coefficient matrix and the echo path of the receiver (i.e. the receiving radar unit), as shown in the following formula (8):
h (j, k) is (x) at spatial position rj，yj，zj) Is propagated to the receiving radar location r1(xk，yk，zk) Is of the form (9):
in the formula (9), Fr(αr,βr) Is the receive unit pattern.
The echo of the direction-finding region received by the receiver is the sum of the echo vectors, as shown in the following formula (10):
the equivalent transformation of formula (10) can be represented by the following formula (11):
the received echo signal is represented by x instead of SIGMA, y, and the system represented by the above equation (11) can be represented in the form of the following equation (12):
y＝Ax (12)
considering the noise effect, the echo model is expressed in the form of the following equation (13):
y＝Ax+n (13)
in the formula (13), n is white Gaussian noise with dimensions of MN × K. In the practical application process, the influence of the white gaussian noise is usually small and can be ignored.
In the practical application process, the obstacles cannot be fully distributed in the direction-finding area. Therefore, in an M × N matrix representing a direction-finding region, only a few grids are usually provided with reflection coefficients, and the reflection coefficients on the other grids are all 0 or close to 0. Thus, the echo signals received by the corresponding receiving radar units have sparseness.
Furthermore, it can be seen from the above discussion that when a multi-point transmitting radar is used for detection, if the signals of the transmitting radar units are in pseudo-thermal form, the set of control functions controlling the respective transmitting radar units can be represented by a control matrix a having low correlation with the received signals.
Meanwhile, as can be seen from the above discussion, the control matrix a, the received echo signal y, and the reflection coefficient matrix SIGMA of the direction finding area have a specific mathematical relationship (see equations (11) to (13)), and therefore, when two of the control matrix a, the echo signal y, and the reflection coefficient matrix SIGMA are known, the other can be calculated by an inversion method.
In addition, the above equation relates the spatial radiation function (i.e., the radiation function from the transmitting radar unit to the target area) and the distribution function Fr(. i.e. the signal distribution function from the target area to the receiving radar unit) are all incorporated into the control matrix a for calculation, but in practice, due to the spatial radiation function and the distribution function FrThe control matrix A should be calculated separately from the two functions in practical application because (-) may be different due to different conditions of propagation medium and the like and is not influenced by the control mode of the transmitting radar.
Therefore, as described above, when a multipoint transmitting radar is used for direction finding, the received echo signal y has sparsity, and there is an uncorrelated relationship between the control matrix a of the multipoint transmitting radar and the echo signal y. Meanwhile, when the control matrix A and the echo signal y are known, a reflection coefficient matrix SIGMA of the direction-finding area can be obtained through inversion.
When an obstacle is present in the direction finding area, the obstacle will reflect the transmission signal, and thus the reflection coefficient at the corresponding grid will not be 0. According to whether the reflection coefficient of each grid in the reflection coefficient matrix SIGMA is 0 (or whether the reflection coefficient is greater than a set threshold), whether an obstacle exists in the corresponding grid can be judged, and whether the obstacle exists in the corresponding direction or not can be known.
Based on the above, the inventor proposes the vehicle-mounted millimeter wave anti-collision radar system based on compressed sensing and multipoint transmission and the obstacle detection method thereof.
Fig. 2 is a configuration diagram of a vehicle-mounted millimeter wave collision avoidance radar system of the embodiment of the present invention.
As shown in fig. 2, the in-vehicle millimeter wave collision avoidance radar system 100 is installed in an automobile, and includes a transmitting radar unit 1, a direction finding signal control unit 2, a first receiving radar unit 3, a reflection coefficient analysis unit 4, an obstacle determination unit 5, a distance measuring signal control unit 6, a second receiving radar unit 7, a distance analysis unit 8, and a control unit 9.
The control unit 9 is configured to control operations of the respective components of the in-vehicle millimeter wave collision avoidance radar system 100. In this embodiment, the control unit 9 further has a data transmission module for transmitting the detection result of the obstacle to the control system of the vehicle or receiving an instruction from the control system of the vehicle.
The transmitting radar part 1 is used for sending detection signals (including direction finding signals and distance measuring signals) and is provided with Q transmitting radar units which are arranged in an array mode. That is, the transmitting radar section 1 has Q transmitting radar units arranged in a matrix form. In the present embodiment, Q ranges from 4 to 16.
The first receiving radar unit 3 and the second receiving radar unit 7 are configured to receive a first echo signal generated by a direction finding signal and a second echo signal generated by a distance measuring signal, respectively. In this embodiment, the first receiving radar unit 3 and the second receiving radar unit 7 are the same radar receiving unit and each have R receiving radar units. In the present embodiment, R ranges from 1 to 8. The receiving radar unit may or may not be configured in a matrix form.
The direction-finding signal control section 2 is configured to control each transmitting radar unit to transmit a direction-finding signal for direction-finding of an obstacle according to a predetermined direction-finding signal control method.
The direction-finding signal control mode is a mode of controlling by using a control matrix A obtained according to the compressed sensing theory.
Fig. 3 is a schematic configuration diagram of a direction-finding signal control section according to an embodiment of the present invention.
As shown in fig. 3, the direction-finding signal control section 2 includes a mesh division unit 21, a function storage unit 22, a control matrix setting unit 23, a signal control unit 24, and a control unit 25.
The control unit 25 is used to control the operations of the respective components of the direction-finding signal control section 2.
The mesh dividing unit 21 is for dividing the target area into M × N meshes. When dividing, the specific value of mxn may be set by the vehicle control system according to the direction finding accuracy, or may be preset when the vehicle-mounted millimeter wave collision avoidance radar system 100 is shipped from the factory.
The function storage unit 22 stores a propagation function H1And echo function H2. Propagation function H1Reflecting the intensity variation of the signal emitted by the emitting radar unit projected to each grid of the direction-finding area, and the echo function H2Reflecting the variation in the strength of the first echo signal generated by each mesh propagating to each receiving radar unit.
Wherein the propagation function H1Obtained in advance by full-wave analysis or analytical deduction, the echo function H2Can be obtained by the same method or according to the propagation function H1And deducing to obtain the product.
The full-wave analysis method is a method for obtaining a corresponding propagation function by analyzing the intensity change in the propagation process of each transmitting radar unit directly according to the propagation characteristics of the transmitting radar unit in a propagation medium.
Analytical deduction is a method that combines actual measurements with analysis. In this embodiment, the analysis deduction method includes the following steps:
and step S1-1, setting a simulated object plane parallel to the matrix plane where the transmitting radar unit is located between the direction-finding area and the transmitting radar unit, and dividing the simulated object plane into M multiplied by N grids. Since the plane of the transmitting radar unit is parallel to the direction-finding area, the analog object plane is also parallel to the direction-finding area, and the M × N grids in the analog object plane are in one-to-one correspondence with the M × N grids in the direction-finding area.
And step S1-2, a test signal is transmitted to the simulated object surface by the transmitting radar unit, and the test signal is respectively received by the simulated object surface by the simulated signal receiving radar, so that an actual signal transmitted by the test signal and propagated to the simulated object surface is obtained.
Step S1-3, carrying out simulation deduction according to the strength relation of the test signal and the actual signal to obtain a propagation function H1. That is, the strength of the signal reaching the grid of the direction-finding area is derived according to the actual strength of the signal transmitted by the transmitting radar unit reaching the grid of the simulated object plane, and is expressed by corresponding functions respectively.
Further, the full-wave analysis method may be combined to perform analysis correction to obtain a corresponding propagation function. For example, a function is obtained by a full-wave analysis method, and then the function obtained by the full-wave analysis method is subjected to parameter correction according to the intensity of an actual signal at a simulated object plane.
In other embodiments, when the requirement for accuracy is slightly low, the above analysis deduction method may not be used, but the full-wave analysis method may be directly used to obtain the above corresponding function.
Meanwhile, the echo function H of the present embodiment2Using a propagation function H1And performing reverse deduction to obtain the target.
The control matrix setting unit 23 is configured to set a control matrix a, which includes Q control functions corresponding to the Q transmitting radar units and respectively causing the Q transmitting radar units to emit transmitting signals of random amplitude and phase.
As described above, when the signals emitted by the respective transmitting radar units are in pseudo-thermal form, the control matrix a for controlling the transmitted signals has low correlation with the echo signals and thus meets the basic requirements of the compressed sensing algorithm. For this reason, the control matrix a needs to make the signals of each transmitting radar unit take pseudo-thermal form, i.e. form of random radiation phase.
In this embodiment, the control matrix a is calculated according to the following formula:
is an amplitude modulation matrix containing Q random amplitude control functions corresponding to Q transmitting radar units, f is a frequency modulation matrix containing Q random frequency control functions corresponding to Q transmitting radar units, and p is a phase modulation matrix containing Q random phase control functions corresponding to Q transmitting radar units.
That is, in the present embodiment, the control matrix a is set only in accordance with the control manner of the transmitting radar unit, without considering the echo function H2And a propagation function H1Such parameters are associated with signal propagation characteristics.
Amplitude modulation matrixAs shown in the following formula:
in the formula,to satisfyA pseudo-random sequence of gaussian distributions, τ being the sequence index in the time dimension.
Similarly, the frequency modulation matrix f and the phase modulation matrix p can be used in combination with the amplitude modulation matrixSimilar forms are shown and will not be described in detail herein.
The signal control unit 24 is configured to control the direction-finding signal sent by the transmitting radar unit according to the control matrix a. Namely, each transmitting radar unit is controlled to transmit signals according to the control function of the corresponding position in the control matrix A, so that each transmitting radar unit independently transmits pseudo-thermal direction-finding signals to the target area.
After the direction-finding signal is transmitted to the target area, a corresponding first echo signal is generated and received by the first radar receiving part 3. The reflection coefficient analysis unit 4 is configured to analyze the first echo signal to obtain a reflection coefficient distribution in the target region.
Specifically, the reflection coefficient analysis section 4 analyzes the propagation function H1Echo function H2And calculating the reflection coefficient matrix x of the direction-finding area by using the control matrix A and the echo matrix y, wherein the reflection coefficient matrix x is the distribution of the reflection coefficients at the target area. The reflection coefficient analysis section 4 calculates a reflection coefficient matrix x of the target region according to the following equation:
y＝H1·H2·A·x
during calculation, the reflection coefficient of each grid of the target area can be calculated in a matrix solving mode, and then each reflection coefficient is subjected to reverse estimation to obtain a reflection coefficient matrix x represented by an M multiplied by N matrix.
The obstacle determination unit 5 is configured to determine whether or not an obstacle exists in each direction of the target area based on the reflectance distribution in the target area and a predetermined reflectance threshold.
The reflection coefficient threshold is a preset value, and when the reflection coefficient of a certain grid at a corresponding position in the reflection coefficient matrix x is higher than the threshold, it can be considered that an obstacle exists at the position corresponding to the grid.
The distance measurement signal control unit 6 controls the transmitting radar unit 1 to transmit a distance measurement signal for measuring the distance to an obstacle.
In this embodiment, the manner in which the ranging signal control unit 6 controls the sending of the ranging signal is: when the obstacle judging section 5 judges that an obstacle exists in a certain direction, the ranging signal control section 6 controls the transmitting radar section 1 to transmit a ranging signal.
Generally, a direction-finding signal needs to be kept for several frames (i.e. for a certain time) to be able to obtain a direction-finding result. In the present embodiment, ranging is performed in the form of n +1 frames, that is, the direction-finding signal control unit 2 controls the transmitting radar unit 1 to send out a direction-finding signal in n frames, and the ranging signal control unit 6 controls the transmitting radar unit 2 to send out a frame of ranging signal in the (n + 1) th frame. In another embodiment, the direction-finding signal control unit 2 may control the transmitting radar unit 1 to continuously transmit the direction-finding signal, and when an obstacle is detected in a certain direction, the control unit 9 may control the distance-measuring signal control unit 6 to control the transmitting radar unit 1 to transmit the corresponding distance-measuring signal.
After the ranging signal is emitted, the ranging signal is projected to a target area, and a second echo signal formed by the ranging signal is received by the second receiving radar unit 7. The distance analyzing unit 8 is configured to analyze the second echo signal to obtain a distance between the obstacle and the vehicle body. In this embodiment, both the sending method of the ranging signal and the analysis method of the second echo signal adopt a radar ranging method known in the prior art, and are not described herein again.
The following describes an obstacle detection flow of the in-vehicle millimeter wave collision avoidance radar system 100 according to the present embodiment with reference to the drawings.
In this embodiment, the propagation function H is measured before the start of the measurement1And echo function H2Has finished measuring, setting, and is stored in the letterIn the number storage unit 22. Meanwhile, the value of the mesh division performed on the target area by the mesh division unit 21, and the control matrix a of the transmission signal control section 2 have also been set in advance.
Fig. 4 is a flow chart of obstacle detection of the vehicle-mounted millimeter wave collision avoidance radar system according to the embodiment of the present invention.
As shown in fig. 4, the obstacle detection flow of the in-vehicle millimeter wave collision avoidance radar system 100 includes the following steps.
In step S1, the mesh dividing unit 21 divides the direction-finding area into N parts in the horizontal direction and M parts in the vertical direction according to a preset mesh division value to obtain M × N meshes, and then proceeds to step S2.
In step S2, the direction-finding signal control unit 2 controls the transmitting radar unit to transmit the direction-finding signal to the target area according to the control matrix a, and the process then proceeds to step S3.
In step S3, the first echo signal generated by projecting the direction-finding signal to the target area is received by the first receiving radar unit 3, and the process proceeds to step S4.
In step S4, the reflectance analysis section 4 analyzes the reflectance distribution of the target region from the first echo signal, and the process proceeds to step S5.
In step S5, the obstacle determination unit 5 determines whether or not an obstacle exists in each direction of the target area based on the reflectance distribution and the preset reflectance threshold, and then the process proceeds to step S6.
In step S6, the ranging signal control unit 6 controls the transmitting radar unit 1 to transmit the ranging signal, and the process then proceeds to step S7.
In step S7, the second receiving radar unit 7 is used to receive the second echo signal formed by projecting the ranging signal to the target area, and the process then proceeds to step S8.
In step S8, the distance analysis unit 8 analyzes the distance to the obstacle, and then the vehicle enters an end state.
In this embodiment, the obstacle detection is performed cyclically. That is, once the in-vehicle millimeter wave collision avoidance radar system 100 starts operating under the instruction of the vehicle control system, the in-vehicle millimeter wave collision avoidance radar system 100 enters the next measurement immediately after the end of one measurement. Therefore, the above-mentioned "entering into the end state" merely means that one measurement ends, and the in-vehicle millimeter wave collision avoidance radar system 100 will start the next measurement immediately after the end state with the same flow as the above-mentioned flow.
Examples effects and effects
According to the vehicle-mounted millimeter wave anti-collision radar system provided by the embodiment, the direction-finding signal control part adopts the matrix which corresponds to Q transmitting radar units and contains random amplitude modulationThe random frequency modulation matrix f and the control matrix A of the random phase modulation matrix p control signals transmitted by the transmitting radar unit, so that the transmitting radar unit transmits pseudo-hot signals, the correlation between the control matrix A and received signals is reduced, and further, a compressed sensing algorithm can be applied to direction finding of the millimeter wave radar, therefore, after corresponding echo signals are measured, a reflection coefficient matrix of a direction finding area can be obtained through a reconstruction method based on compressed sensing, and whether obstacles exist in the corresponding direction is further judged according to reflection coefficients corresponding to grids in the reflection coefficient matrix.
Therefore, the system provided by the embodiment adopts the multipoint emission type radar to carry out direction finding, the number of the emission radar units in the multipoint emission type radar is 4-16, the problem that the resolution of the single-point radar in the traditional radar measuring method is limited by the Rayleigh limit can be solved, the whole resolution breaks through the limit which can be reached by the single-point radar, and the direction finding resolution is greatly improved. Meanwhile, the algorithm of the compressed sensing is adopted for sampling and data analysis, so that the result can be accurately analyzed. Therefore, the method of the embodiment can simultaneously realize high-precision and wide-range direction finding.
In an embodiment, the propagation function stored in the function storage unit is obtained by an analytical deduction method, and the echo function is obtained by deduction according to the propagation function. Because the analysis deduction method combines the actual measurement data with the analysis process according to the propagation characteristics, the intensity change of the signals in the processes of emission and reflection can be reflected more accurately, and the precision of the method of the embodiment is further improved.
Claims (7)
1. The utility model provides an on-vehicle millimeter wave anticollision radar system, installs on the car for carry out direction finding and range finding to the barrier in the target area around the automobile body, its characterized in that includes:
the transmitting radar part is provided with Q transmitting radar units which are arranged in an array manner and transmits radar signals to the target area;
a direction-finding signal control section for controlling the transmitting radar unit to transmit a direction-finding signal for direction-finding of an obstacle according to a predetermined direction-finding signal control mode;
a first receiving radar unit having R first receiving radar units, for receiving a first echo signal generated by the direction-finding signal;
a reflection coefficient analysis unit configured to analyze the first echo signal to obtain a reflection coefficient distribution in the target region;
an obstacle determination unit configured to determine whether an obstacle exists in each direction of the target area based on the reflection coefficient distribution in the target area and a predetermined reflection coefficient threshold;
a ranging signal control part for controlling the transmitting radar unit to transmit a ranging signal for ranging an obstacle according to a predetermined ranging signal control method;
a second receiving radar unit that receives a second echo signal generated by the ranging signal; and
a distance analysis unit that analyzes the second echo signal to obtain a distance between the obstacle and the vehicle body,
wherein, the control matrix A is calculated according to the following formula:
in the above formula, the first and second carbon atoms are,the method comprises the steps of obtaining an amplitude modulation matrix containing Q random amplitude control functions corresponding to the Q radar transmitting units, obtaining a frequency modulation matrix containing Q random frequency control functions corresponding to the Q radar transmitting units, and obtaining a phase modulation matrix containing Q random phase control functions corresponding to the Q radar transmitting units.
2. The vehicle-mounted millimeter wave collision avoidance radar system of claim 1, wherein:
wherein the direction-finding signal control section includes:
a mesh dividing unit that divides the target area into M × N meshes;
function memoryA storage unit for storing a propagation function H reflecting intensity variation of the signal emitted by the radar emission unit projected to each grid of the direction finding area1And an echo function H reflecting the intensity variation of the first echo signal generated by each of the grids propagating to the R receiving radar units2；
The control matrix setting unit is used for setting a control matrix A which comprises Q control functions corresponding to Q radar transmitting units and respectively enabling the Q radar transmitting units to transmit random amplitude-phase transmitting signals; and
a signal control unit for controlling the radar transmitting unit to transmit the direction-finding signal according to the control matrix A,
the reflection coefficient analysis unit is based on the propagation function H1And the echo function H2And the control matrix A analyzes the first echo signal to obtain a reflection matrix x containing reflection coefficients respectively corresponding to the grids as the reflection coefficient distribution.
3. The vehicle-mounted millimeter wave collision avoidance radar system of claim 1, wherein:
wherein Q is in the range of 4 to 16,
r ranges from 1 to 8.
4. The vehicle-mounted millimeter wave collision avoidance radar system of claim 1, wherein:
wherein the amplitude modulation matrixAs shown in the following formula:
wherein,to satisfy a pseudo-random sequence of a gaussian distribution, τ is the sequence index in the time dimension.
5. The vehicle-mounted millimeter wave collision avoidance radar system of claim 1, further comprising:
and the control part controls the direction-finding signal control part to control the transmitting radar part to transmit n frames of the direction-finding signals, and further controls the distance-measuring signal control part to control the transmitting radar part to transmit 1 frame of the distance-measuring signals.
6. The vehicle-mounted millimeter wave collision avoidance radar system of claim 1, further comprising:
a control part for controlling the operation of the display device,
when the obstacle judging part judges that an obstacle exists in the target area, the control part controls the ranging signal control part, so that the ranging signal control part controls the transmitting radar part to send out 1 frame of ranging signal.
7. A method for detecting obstacles in a vehicle-mounted millimeter wave anti-collision radar system is used for carrying out direction finding and distance measuring on the obstacles in a target area around a vehicle body, and is characterized by comprising the following steps:
step S1, dividing the direction-finding area into N parts in the horizontal direction and M parts in the vertical direction by adopting a grid dividing unit to obtain M multiplied by N grids;
step S2, a direction-finding signal control part is adopted to control Q transmitting radar units arranged in a matrix form to transmit direction-finding signals to the target area according to a control matrix A;
step S3, a first echo signal formed after the direction-finding signal is projected to the target area is received by a first receiving radar part;
step S4, a reflection coefficient analysis part is adopted to analyze the reflection coefficient distribution of the target area according to the first echo signal;
step S5, judging whether there is an obstacle in each direction of the target area by an obstacle judging part according to the reflection coefficient distribution and a preset reflection coefficient threshold;
step S6, a ranging signal control part is adopted to control the transmitting radar part to transmit ranging signals;
step S7, a second receiving radar part is adopted to receive a second echo signal formed after the ranging signal is projected to the target area;
step S8, adopting the distance analysis part to analyze the distance of the obstacle,
wherein, the control matrix A is calculated according to the following formula:
in the above formula, the first and second carbon atoms are,the method comprises the steps of obtaining an amplitude modulation matrix containing Q random amplitude control functions corresponding to the Q radar transmitting units, obtaining a frequency modulation matrix containing Q random frequency control functions corresponding to the Q radar transmitting units, and obtaining a phase modulation matrix containing Q random phase control functions corresponding to the Q radar transmitting units.
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