阅读说明：本技术 用于运动物体高精度测距的雷达装置及其测量方法 (Radar device for high-precision distance measurement of moving object and measurement method thereof ) 是由 陈侃 梁卫祖 刘培育 植宝辉 王磊 于 2021-01-11 设计创作，主要内容包括：本发明用于运动物体高精度测距的雷达装置及其测量方法,毫米波雷达安装在运动物体上,通过测量反射体与运动物体之间相对运动的距离和速度,从而测量出运动物体移动的距离和速度；反射体固定静止并设置两层间距为Δd-(real)、半径r-1和r-2的反射板,使用圆极化透镜天线,毫米波雷达发射电磁波到反射体,并接收反射回来电磁波,分别计算出第一层反射板和第二层反射板的距离d-1和d-2,以及两层反射板之间的距离差通过ZoomFFT算法、跟踪算法和数据处理,确保测量目标可靠和准确性,消除多径和其它反射物回波影响,测量距离精度达到毫米级；能够解决复杂环境使用场景中的多径干扰和其它反射物反射干扰问题,测量出运动物体移动距离和速度,成本低廉,结构简单,操作方便。(The invention relates to a radar device for high-precision distance measurement of a moving object and a measuring method thereof.A millimeter wave radar is arranged on the moving object, and the distance and the speed of the movement of the moving object are measured by measuring the distance and the speed of the relative movement between a reflector and the moving object; the reflector is fixed and static and is provided with a distance delta d between two layers real Radius r 1 And r 2 The reflecting plate uses a circularly polarized lens antenna, a millimeter wave radar transmits electromagnetic waves to a reflector and receives the reflected electromagnetic waves, and the distances d between the first layer of reflecting plate and the second layer of reflecting plate are respectively calculated 1 And d 2 And the difference in distance between the two reflecting plates Through the ZoomFFT algorithm, the tracking algorithm and the data processing, the reliability and the accuracy of a measured target are ensured, the influence of multipath and echoes of other reflectors is eliminated, and the precision of the measured distance reaches the millimeter level; capable of solving complex environment use sceneThe multi-path interference and the reflection interference of other reflectors can be solved, the moving distance and the moving speed of the moving object can be measured, the cost is low, the structure is simple, and the operation is convenient.)

1. A radar device for high-precision distance measurement of a moving object is characterized in that: the device comprises a millimeter wave radar and a reflector which are sequentially arranged side by side, wherein the millimeter wave radar is fixed on a moving object, and the reflector is fixedly installed through a fixed background wall; the reflector is provided with a plurality of layers of reflecting plates extending along the vertical direction, and the reflecting areas of the plurality of layers of reflecting plates are gradually increased along the direction far away from the millimeter wave radar; the center position of each layer of reflecting plate and the center position of the millimeter wave radar are positioned in the same horizontal plane, and the distance between the last layer of reflecting plate farthest from the millimeter wave radar and the fixed background wall is more than or equal to the distance resolution d_res6 times of the distance between each layer of reflecting plate and the next layer of reflecting plate is larger than or equal to the distance resolution d_res6 times of the total weight of the composition; the distance resolution d_resBy the formulaWhere c is the speed of light and B is the FMCW wave swept bandwidth.

2. The radar apparatus for high-precision ranging of a moving object according to claim 1, wherein: the antenna unit of the millimeter wave radar adopts a receiving and transmitting shared antenna unit, receiving and transmitting wave beams are symmetrically arranged, and the pointing direction of the wave beams is 0 degree.

3. The radar apparatus for high-precision ranging of a moving object according to claim 2, wherein: the antenna of the millimeter wave radar adopts a circularly polarized lens antenna, and the 3dB wave beam width of the circularly polarized lens antenna is less than or equal to +/-1.25 degrees; the millimeter wave radar is provided with a Langer coupler, the Langer coupler can feed the antenna units orthogonally, and the polarization mode of the transmitting antenna is opposite to that of the receiving antenna.

4. A radar apparatus for high-precision ranging of a moving object according to claim 3, wherein: the reflector is provided with a first layer of reflecting plate and a second layer of reflecting plate, and the radius r of the first layer of reflecting plate₁Radius r of the second layer reflector plate of 5mm₂30 mm; each layer of reflecting plate is an aluminum plate.

5. A measuring method of a radar apparatus for high-precision ranging of a moving object according to any one of claims 1 to 4, wherein: the method comprises the following steps:

s1, searching for the radar initial power-on reflector:

the millimeter wave radar transmits frequency-modulated continuous waves and receives electromagnetic waves respectively reflected by a first layer of reflecting plate and a second layer of reflecting plate of a reflector to generate two beat frequencies delta f₁And Δ f₂Respectively processed by high-precision algorithm ZoomFFT, according to formulaCalculating the distance d between the millimeter-wave radar and the first layer of reflecting plate₁And the distance d between the millimeter-wave radar and the second layer reflecting plate₂The difference between the two distances isWherein d is the distance between the radar and the reflecting plate, Δ f is the beat frequency, T is the frequency sweep time period of the FMCW wave, c is the speed of light, and B is the frequency sweep bandwidth of the FMCW wave;

s2, determining a reflector:

respectively measuring the distance d between the first layer of reflecting plate and the millimeter wave radar₁And a secondDistance d between layer reflecting plate and millimeter wave radar₂Preferably satisfies the condition d₂-d₁＝Δd_real±d_resThe reflector is a preset reflector; when all the reflectors can not meet the preset condition, selecting the reflector with the maximum energy as a reflector target according to the two-dimensional FFT amplitude spectrum value of the reflector;

s3, forming two tracking tracks through the first layer of reflecting plate and the second layer of reflecting plate in the moving process of the moving object provided with the millimeter wave radar, wherein when the tracking track formed by one layer of reflecting plate is interfered by other false targets and lost, the tracking track formed by the other layer of reflecting plate is delta d_real±d_resSearching nearby and retrieving the positions of the two reflecting plates again;

and S4, respectively calculating the signal energy and the signal-to-noise ratio of the first layer of reflecting plate and the second layer of reflecting plate on the basis of the calculation result of S3, selecting the distance value between the larger signal energy and the millimeter wave radar as an accurate value, and processing the distance measurement result by linear filtering to realize accurate distance and speed information output.

6. The measurement method of the radar apparatus for high-precision ranging of the moving object according to claim 5, wherein: in step S1, the millimeter wave radar transmits N FMCW waveforms in one measurement process, where N is 16, 32, 64, 128, 256, or 512; when the distance of the static reflector is measured, firstly accumulating time domain sampling signals of a plurality of FMCW waveforms, and then calculating the accurate distance of the reflector through a ZoomFFT spectrum thinning algorithm; the moving speed of the moving object relative to the reflecting plate is obtained through two-dimensional FFT.

7. The measurement method of the radar apparatus for high-precision ranging of the moving object according to claim 6, wherein:

the N FMCW waveform signals transmitted by the millimeter wave radar at different times in step S1 are represented by the following equation:

wherein A is_TkTo transmit signal amplitude, f₀，The number of waveforms N for the initial frequency and initial phase of the FMCW signal may preferably be 16, 32, 64, 128, 256, 512;

after being reflected by the reflecting plate, the signals received at different moments are as follows:

A_Rkfor the k-th received signal amplitude, τ_i，The delay and the phase of the ith reflector path in the environment are shown, WGN (delta) is environment white noise, the amplitude mean value delta and the phase are random;

the system mixes the transmitting signal and the receiving signal and filters high-frequency components;

the intermediate frequency beat signal is represented as:

wherein the intermediate frequency of the reflector plate isF is calculated by distance dimension Fourier transform_IiThen by the formulaCalculating the distance between the reflecting plate and the radar, wherein c is the speed of light;

the intermediate frequency signals are accumulated and then averaged:

after processing, the effective signal amplitude of the intermediate frequency signal is mean valueThe amplitude of the null signal is offset by the amplitude generated by the random phase of the noise, and the mean value of the noise amplitude becomesTherefore, the signal-to-noise ratio of the system is increased to N times before the noise amplitude is offset, and f is calculated through distance dimension Fourier transform_Ii；

The system distance measurement precision is

Wherein f is_sThe sampling rate of the radar is m, and the number of sampling points of a single waveform is m;

interpolating a distance dimension Fourier transform result by adopting a ZoomFFT spectrum thinning algorithm;

the interpolation multiple is n, m is preferably 128, 256, 512 and 1024, and n is preferably 64, 128, 256 and 512;

the system ranging precision is improved to

Storing the distance dimension Fourier transform result of the last step into a system cache (RAM);

after the transform results of the Nth waveform distance dimensional Fourier transform and the zoomFFT spectrum refinement are collected, the stored data are subjected to velocity dimensional Fourier transform;

the speed of the current moving object relative to the reflecting plate is obtained through distance-speed two-dimensional transformation, and the precision isWhereinλ is the wavelength.

8. The method of claim 5, wherein the radar apparatus for high-precision ranging of moving objects comprises: in the step S4, d is added₂-d₁From a known distance Δ d_realComparison, when d₂-d₁From a known distance Δ d_realAnd if the distance measurement result is inconsistent, judging that the distance measurement result has multipath influence, and then performing compensation correction on the distance measured by the radar by adopting a compensation algorithm.

9. The measurement method of the radar apparatus for high-precision ranging of the moving object according to claim 8, wherein:

when the environment has multipath interference, the radar measures the distance of a single reflectord_realAs the real distance of the reflector from the radar, d_multRange offsets generated for multipath effects;

due to d_multFar less than radar range resolution

So that the distance between the two layers is set to satisfy Deltad_real≥6×d_resThe distance between the two reflecting plates is d₁＝d_real1+d_mult1And d₂＝d_real2+d_mult2(ii) a The difference between the two reflecting plates is d₁₂＝d₁-d₂＝d_real1-d_real2+d_mult1-d_mult2＝Δd_real+d_mult12(ii) a Distance measurement deviation d generated by multipath influence_mult12＝d₁₂-Δd_real(ii) a Wherein, Δ d_realA known spacing of two reflector plates;

when d is₁₂＝Δd_realJudging that the current result is accurate and is not influenced by multipath interference;

when d is₁₂≠Δd_realIn the process, interference influence exists in the ranging result, and the next compensation correction is needed.

Taking the measured reflection energy or signal-to-noise ratio of the two layers of reflecting plates as a weight to carry out compensation correction;

setting two layers of reflecting plates to reflect energy as p₁And p₂Signal to noise ratio of s₁And s₂(ii) a Obtaining a corrected ranging result through the following formula:

or:

and selecting the ranging result with large reflection energy or signal-to-noise ratio as a final result to be output.

10. The measurement method of the radar apparatus for high-precision ranging of the moving object according to claim 5, wherein:

the method for processing the ranging result by adopting the linear filtering specifically comprises the following steps:

s51, predicting X (k | k-1) state according to the k-1 time result;

s52, covariance matrix P prediction, P (k | k-1) ═ P (k-1) + Q;

s53, calculating a linear gain K, K ═ P (K | K-1)/(P (K | K-1) + R);

s54, state X update, X (K) ═ X (K-1) + K (in (K) — X (K-1));

s55, covariance matrix update, P (K) × P (K | K-1);

s56, outputting the processing result, out (k) ═ x (k);

wherein Q is the process noise variance and R is the measurement noise variance;

the process noise variance Q is 0.001;

the measurement noise variance R is 0.002.

Technical Field

The invention belongs to the technical field of radar short-range high-precision distance measurement in the radio industry, and particularly relates to a radar device for high-precision distance measurement of a moving object and a measuring method thereof.

Background

In the field of radar short-range high-precision ranging, FMCW waves are generally transmitted by a radar, and a time difference delta tau exists between the transmitted electromagnetic waves and the received reflected echoes of a reflector, so that the frequency is inconsistent with the local frequency at the moment; by utilizing the difference, beat frequency delta f is formed by the receiving down converter, and after ADC sampling, the distance of the reflector is calculated through zoom FFT refinement and amplification, so that the speed of the relative reflector is calculated through two-dimensional FFT, and the purpose of distance measurement is realized; however, in a scene with a complex use environment, such as an application site of elevator shaft position positioning, logistics dock warehouse hoisting positioning, conveyor belt vehicle positioning and the like, due to the fact that a plurality of interference signals exist in the complex environment, electromagnetic waves received by a radar include multipath frequency components and other reflector reflection frequency components of the surrounding environment, the signal-to-noise ratio of useful reflector signals is reduced, the ranging accuracy is influenced, and the multipath frequency components and the other reflector interference frequency components need to be distinguished; in the prior art, a mode of narrowing a wave beam (spatial resolution) or improving distance resolution (frequency resolution) is generally adopted to achieve the purpose of distinguishing multipath frequency components and other reflector interference frequency components, but the aperture of an antenna needs to be improved by narrowing the wave beam, and the aperture of the antenna is limited by engineering construction, spatial arrangement and manufacturing cost and is difficult to improve; the range resolution is limited by the sweep frequency bandwidth of the radar, the device capability and the radio frequency spectrum supervision, and is not easy to improve.

In addition, in the traditional method, the reflector is usually tracked by depending on the intensity of energy reflected by the object under the condition of a single reflector, and the moving process is easily interfered by other objects, even the reflector is lost, so that the distance measuring effect is influenced; the interference of mechanical vibration or other environmental factors causes disturbance to the finally obtained ranging result.

Disclosure of Invention

In order to solve the above problems in the prior art, the present invention aims to provide a radar apparatus and a measurement method thereof, which can solve the problems of multipath interference and reflection interference of other reflectors in a complex environment use scene, measure the relative movement distance and speed between a reflector and a millimeter wave radar, have low cost, simple structure and convenient operation, and are used for high-precision distance measurement of a moving object.

The technical scheme adopted by the invention is as follows:

the device comprises a millimeter wave radar and a reflector which are sequentially arranged side by side, wherein the millimeter wave radar is fixed on a moving object, and the reflector is fixedly installed through a fixed background wall; the reflector is provided with a plurality of layers of reflecting plates extending along the vertical direction, and the reflecting areas of the plurality of layers of reflecting plates are gradually increased along the direction far away from the millimeter wave radar; the center position of each layer of reflecting plate and the center position of the millimeter wave radar are positioned in the same horizontal plane, and the distance between the last layer of reflecting plate farthest from the millimeter wave radar and the fixed background wall is more than or equal to the distance resolution d_res6 times of the distance between each layer of reflecting plate and the next layer of reflecting plate is larger than or equal to the distance resolution d_res6 times of the total weight of the composition; the distance resolution d_resBy the formulaWhere c is the speed of light and B is the FMCW wave swept bandwidth.

The antenna unit of the millimeter wave radar adopts a receiving and transmitting shared antenna unit, receiving and transmitting wave beams are symmetrically arranged, and the pointing direction of the wave beams is 0 degree.

The antenna of the millimeter wave radar adopts a circularly polarized lens antenna, and the 3dB wave beam width of the circularly polarized lens antenna is less than or equal to +/-1.25 degrees.

The millimeter wave radar is provided with a Langer coupler, the Langer coupler can feed the antenna units orthogonally, and the polarization mode of the transmitting antenna is opposite to that of the receiving antenna.

The reflector is provided with a first layer of reflecting plate and a second layer of reflecting plate, the radius of the first layer of reflecting plate is 5mm, and the radius of the second layer of reflecting plate is 30 mm; each layer of reflecting plate is an aluminum plate.

The invention also relates to a measuring method of the radar device for the high-precision distance measurement of the moving object, which comprises the following steps:

s1, searching for the radar initial power-on reflector:

the millimeter wave radar transmits frequency-modulated continuous waves and receives electromagnetic waves respectively reflected by a first layer of reflecting plate and a second layer of reflecting plate of a reflector to generate two beat frequencies delta f₁And Δ f₂Respectively processed by high-precision algorithm ZoomFFT, according to formulaWherein d is the distance between the radar and the reflector, Δ f is the beat frequency, T is the frequency sweep time period of the FMCW wave, c is the speed of light, and B is the frequency sweep bandwidth of the FMCW wave; calculating the distance d between the millimeter-wave radar and the first layer of reflecting plate₁And the distance d between the millimeter-wave radar and the second layer reflecting plate₂The difference between the two distances is

S2, determining a reflector:

measuring the distance between the first layer of reflecting plate and the millimeter wave radar, preferably satisfying the condition d₂-d₁＝Δd_real±d_resThe target of (1) is a preset reflector target; when all the reflectors can not meet the preset condition, selecting the reflector with the maximum energy as a reflector target according to the two-dimensional FFT amplitude spectrum value of the reflector;

s3, in the moving process of the millimeter wave radar, two tracking tracks are formed through the first layer of reflecting plate and the second layer of reflecting plate, and when the tracking track formed by one layer of reflecting plate is interfered by other false reflectors and lost, the tracking track formed by the other layer of reflecting plate is at delta d_real±d_resSearching nearby and retrieving the preset reflector again;

and S4, respectively calculating the signal energy and the signal-to-noise ratio of the first layer of reflecting plate and the second layer of reflecting plate on the basis of the calculation result of S3, selecting the distance value between the larger signal energy and the millimeter wave radar as an accurate value, and outputting accurate distance and speed information by adopting linear filtering processing as a final result.

In step S1, the millimeter wave radar transmits N FMCW waveforms in one measurement process, where N is 16, 32, 64, 128, 256, or 512; when the distance of the static reflector is measured, firstly accumulating time domain sampling signals of a plurality of FMCW waveforms, and then calculating the accurate distance of the reflector through a ZoomFFT spectrum thinning algorithm; the moving speed of the moving object relative to the reflecting plate is obtained through two-dimensional FFT.

In the step S4, d is added₂-d₁From a known distance Δ d_realComparison, when d₂-d₁From a known distance Δ d_realAnd if the distance measurement result is inconsistent, judging that the distance measurement result has multipath influence, and then performing compensation correction on the distance measured by the radar by adopting a compensation algorithm.

The N FMCW waveform signals transmitted by the millimeter wave radar at different times in step S1 are represented by the following equation:

wherein A is_TkTo transmit signal amplitude, f₀，The number of waveforms N for the initial frequency and initial phase of the FMCW signal may preferably be 16, 32, 64, 128, 256, 512;

after being reflected by the reflecting plate, the signals received at different moments are as follows:

A_Rkfor the k-th received signal amplitude, τ_i，The delay and the phase of the ith reflector path in the environment are shown, WGN (delta) is environment white noise, the amplitude mean value delta and the phase are random;

the system mixes the transmitting signal and the receiving signal and filters high-frequency components;

the intermediate frequency beat signal is represented as:

wherein the intermediate frequency of the reflector plate isF is calculated by distance dimension Fourier transform_IiThen by the formulaCalculating the distance between the reflecting plate and the radar, wherein c is the speed of light;

the intermediate frequency signals can be accumulated and then averaged:

after processing, the effective signal amplitude of the intermediate frequency signal is mean valueThe amplitude of the null signal is offset by the amplitude generated by the random phase of the noise, and the mean value of the noise amplitude becomesTherefore, the signal-to-noise ratio of the system is increased to N times before the noise amplitude is offset, and f is calculated through distance dimension Fourier transform_Ii；

The system distance measurement precision is

Wherein f is_sThe sampling rate of the radar is m, and the number of sampling points of a single waveform is m;

interpolating a distance dimension Fourier transform result by adopting a ZoomFFT spectrum thinning algorithm;

the interpolation multiple is n, m is preferably 128, 256, 512 and 1024, and n is preferably 64, 128, 256 and 512;

the system ranging precision is improved to

Storing the distance dimension Fourier transform result of the last step into a system cache (RAM);

after the transform results of the Nth waveform distance dimensional Fourier transform and the zoomFFT spectrum refinement are collected, the stored data are subjected to velocity dimensional Fourier transform;

the speed of the current moving object relative to the reflecting plate is obtained through distance-speed two-dimensional transformation, and the precision isWhere λ is the wavelength.

When the environment has multipath interference, the radar measures the distance of a single reflectord_realAs the real distance of the reflector from the radar, d_multRange offsets generated for multipath effects;

due to d_multFar less than radar range resolution

So that two spaces are set to satisfy Δ d_real≥6×d_resThe distance between the two reflecting plates is d₁＝d_real1+d_mult1And d₂＝d_real2+d_mult2The difference of the distances between the two reflecting plates is d₁₂＝d₁-d₂＝d_real1-d_real2+d_mult1-d_mult2＝Δd_real+d_mult12(ii) a Distance measurement deviation d generated by multipath influence_mult12＝d₁₂-Δd_real(ii) a Wherein, Δ d_realThe known spacing of the two reflector plates;

when d is₁₂＝Δd_realJudging that the current result is accurate and is not influenced by multipath interference;

when d is₁₂≠Δd_realIn the process, interference influence exists in the ranging result, and the next compensation correction is needed.

And the measured reflection energy or signal-to-noise ratio of the two layers of reflecting plates is used as a weight to carry out compensation correction;

setting the energy reflected by two layers of reflecting plates as p₁And p₂Signal to noise ratio of s₁And s₂(ii) a Obtaining a corrected ranging result through the following formula:

or:

and selecting the ranging result with large reflection energy or signal-to-noise ratio as a final result to be output.

And processing the ranging result by adopting linear filtering, specifically comprising the following steps: s11, according to the k-1 time node

If so, predicting X (k | k-1) for the state;

s12, covariance matrix P prediction, P (k | k-1) ═ P (k-1) + Q;

s13, calculating a linear gain K, K ═ P (K | K-1)/(P (K | K-1) + R);

s14, state X update, X (K) ═ X (K-1) + K (in (K) — X (K-1));

s15, covariance matrix update, P (K) × P (K | K-1);

s16, outputting the processing result, out (k) ═ x (k);

where Q is the process noise variance and R is the measurement noise variance.

The process noise variance preferentially selects Q to be 0.001;

the measurement noise variance is preferably 0.002.

The invention has the beneficial effects that:

a radar device for high-precision distance measurement of a moving object and a measuring method thereof are disclosed, wherein a millimeter wave radar is fixedly arranged on the moving object, and the purpose of measuring the moving distance and speed of the moving object is achieved by measuring the distance and speed of relative movement between a reflector and the moving object; the reflector is simultaneously provided with two layers of reflecting plates, which is beneficial to tracking and positioning of the distance measurement reflector; when the signal of one of the reflecting plates is interfered and lost, the distance relationship between the two reflecting plates can be determined at delta d_real±d_resNearby, searching the reflecting plate meeting the distance relation again to ensure the continuous tracking and ranging process; linear filtering processing is adopted, so that result disturbance can be reduced, stable output is realized, and the disturbance phenomenon of the final ranging result caused by mechanical vibration or interference of other environmental factors is prevented; the ranging accuracy under the conditions of multipath and stray interference can be improved, and millimeter-level precision is achieved; the method can solve the problems of multipath interference and reflection interference of other reflectors in a complex environment use scene, measures the moving distance and speed of a moving object relative to the reflectors, and has the advantages of low cost, simple structure and convenient operation.

Drawings

FIG. 1 is a schematic structural diagram of a radar device for high-precision ranging of a moving object according to the present invention

FIG. 2 is a schematic diagram of a radar reflector structure of the radar apparatus for high-precision ranging of moving objects according to the present invention;

FIG. 3 is a schematic diagram of the change of the reflected signal of the circularly polarized antenna of the radar apparatus for high-precision distance measurement of a moving object according to the present invention;

fig. 4 is a schematic diagram of the digital signal processing flow of the radar device for high-precision distance measurement of a moving object according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or intervening components may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The terms "connected" and "coupled" when used in this application, encompass both direct and indirect connections, and also include both direct and indirect connections, where appropriate and without making any inconsistency.

The invention provides a radar device for high-precision distance measurement of a moving object, which has the following general concept scheme: the millimeter wave radar 1 is installed on a moving object, the reflector 2 is fixedly installed through the fixed background wall 5, the reflector 2 is fixed and static, the millimeter wave radar is fixedly installed on the moving object, and the distance and the speed of the moving object can be measured by measuring the distance and the speed of the relative movement between the reflector and the moving object.

A plurality of layers of reflecting plates are arranged in the reflector 2, each layer of reflecting plate and the fixed background wall extend in the vertical direction and are parallel to each other, and the reflecting areas of the plurality of layers of reflecting plates are gradually increased in the direction away from the millimeter wave radar; the center position of each layer of reflecting plate and the center position of the millimeter wave radar are positioned in the same horizontal plane, and the distance between the last layer of reflecting plate farthest from the millimeter wave radar and the fixed background wall is more than or equal to the distance resolution d_res6 times of the distance between each layer of reflecting plate and the next layer of reflecting plate is larger than or equal to the distance resolution d_res6 times of the total weight of the composition; distance resolution d_resBy the formulaWhere c is the speed of light and B is the FMCW wave swept bandwidth. FMCW frequency modulation continuous waves (FMCW waves for short) transmitted by a millimeter wave radar are respectively reflected by a plurality of layers of reflecting plates, the millimeter wave radar obtains distance precision and speed precision after mixing and operation processing of transmitted and received signals, and selects a ranging result with large reflection energy or signal-to-noise ratio according to use requirements to be output as a final result; linear filtering processing is adopted, so that result disturbance can be reduced, stable output is realized, and the disturbance phenomenon of the final ranging result caused by mechanical vibration or interference of other environmental factors is prevented; the ranging accuracy under the conditions of multipath and stray interference can be improved, and millimeter-level precision is achieved; the method can solve the problems of multipath interference and reflection interference of other reflectors in a complex environment use scene, measures the moving distance and speed of a moving object relative to the reflectors, and has the advantages of low cost, simple structure and convenient operation.

Specifically, in a radar device structure for high-precision distance measurement of a moving object, a millimeter wave radar 1 (hereinafter referred to as a radar) is installed on the moving object, a reflector 2 (hereinafter referred to as a reflecting device) is fixed through a fixed background wall 5, two layers of reflecting plates of a first layer reflecting plate 3 and a second layer reflecting plate 4 are arranged inside the reflector 2, the two layers of reflecting plates of the first layer reflecting plate 3 and the second layer reflecting plate 4 are made of aluminum plates or other metal materials, and the reflecting area of the first layer reflecting plate 3 is smaller than that of the second layer reflecting plate 4A reflection area; the distance between the two layers of reflecting plates (hereinafter referred to as reflecting surfaces) can be adjusted according to practical application, and the minimum distance d between the second layer of reflecting plate 4 and the installation surface of the fixed background wall 5_min≥6×d_resThe minimum distance Δ d between the first-layer reflector 3 (hereinafter referred to as the first-layer reflecting surface) and the second-layer reflector 4 (hereinafter referred to as the second-layer reflecting surface)_real≥6×d_resAnd signals between two layers of reflecting plates, namely two layers of reflecting surfaces, are prevented from interfering with each other.

As shown in fig. 2, the center of the reflector faces the center of the radar, the first layer of reflecting surface is close to the radar, and the second layer of reflecting surface is far from the radar;

the radar antenna adopts a circularly polarized lens antenna, and 3dB wave beams are less than or equal to +/-1.25 degrees;

the radar antenna is designed by adopting a receiving and transmitting shared antenna unit, the receiving and transmitting wave beams are symmetrical, and the wave beams point to the direction of 0 degree;

the Langer coupler is adopted to orthogonally feed the antenna units, the polarization mode of the transmitting antenna is right-handed/left-handed, and the polarization mode of the receiving antenna is left-handed/right-handed, so that polarization isolation is realized; the working principle is shown in fig. 3.

As shown in fig. 1, the millimeter wave radar 1 is provided with a circularly polarized lens antenna, the circularly polarized lens antenna is simultaneously connected with a TX amplifier and an RX amplifier through a Langer coupler, the RX amplifier is connected with the TX amplifier through a down converter, a digital-to-analog converter, a digital signal processor and an FMCW wave generator in sequence, wherein the digital signal processor is connected with an ARM processor.

The radar will transmit multiple FMCW waveforms, the number N of which may preferably be 16, 32, 64, 128, 256, 512, during one measurement.

The digital signal processing flow is shown in fig. 4, and the operation steps are as follows:

the radar mixes the transmitted and received signals, the filter filters out high frequency components to obtain an intermediate frequency signal f_I；

The intermediate frequency signal is subjected to time domain accumulation averaging noise reduction processing, and the effective signal amplitude is an average valueMean value of noise amplitudeIs composed of

By means of m-point distance dimension Fourier transform, the intermediate frequency f of the two layers of reflecting plates can be calculated₁And f₂The number of Fourier transform points is preferably 128, 256, 512 and 1024, and the distance precision is in this case

Interpolating the Fourier transform result by adopting a ZoomFFT algorithm to obtain a refined frequency f₁' and f₂'. The interpolation multiple of the algorithm is n, n can be optimized to 64, 128, 256 and 512 in consideration of comprehensive hardware processing capacity, and the refined distance precision is

The Fourier transform result of each waveform is stored in a system buffer (RAM). And after the transformation result of the Nth waveform is collected, performing velocity dimension Fourier transformation. The speed v of the current moving object relative to the reflecting plate is obtained through distance-speed two-dimensional transformation, and the precision is

In the application of moving object distance measurement, after one reflecting plate is interfered and lost, the distance relationship between two reflecting plates can be determined according to the delta d_real±d_resAnd searching for a reflector meeting the distance relation again nearby, and considering the reflector as a preset reflector.

Distance d between two reflecting plates₁＝d_real1+d_mult1And d₂＝d_real2+d_mult2. The difference between the two distances is d₁₂＝d₁-d₂＝d_real1-d_real2+d_mult1-d_mult2＝Δd_real+d_mult12. When d is₁₂＝Δd_realAnd meanwhile, the current result can be judged to be accurate and not influenced by multipath interference. When d is₁₂≠Δd_realIn the process, interference influence exists in the ranging result, and the next compensation correction is needed.

Further, the result is corrected by the following equation in the multipath case:

or:

in some application scenarios, the system only requires that one valid ranging result be output. At this time, a ranging result with large reflection energy or signal-to-noise ratio may be preferably output as a final result;

linear filtering processing is adopted, so that result disturbance is reduced, and stable output is realized;

the linear filtering process and the measured noise variance are preferably: q ═ 0.001 and R ═ 0.002.

The invention relates to a device and a method in a radar system, in particular to the field of short-range high-precision distance measurement of a moving object on a track in a complex environment. The method is used for realizing high-precision distance measurement on the linearly moving object on the track in the complex interference environment. The radar system comprises a millimeter-wave radar mounted on a moving object, a circularly polarized lens antenna, and a reflector fixed and stationary at a known separation distance Δ d_realRadii r1 and r₂The double-layer reflecting surface of (1). The millimeter wave radar transmits electromagnetic waves to the reflector, and the distances d between the first layer of reflecting surface and the second layer of reflecting surface are calculated by receiving the reflected electromagnetic waves₁And d₂，Through the ZoomFFT algorithm, the tracking algorithm and data processing, the reliability and accuracy of the measured reflector are determined, the influence of multipath and echoes of other reflectors is eliminated better, and the accuracy of the measured distance reaches the millimeter level.

1. First of radar transmitting FMCW wave and receiving reflectorThe layer reflecting surface and the second layer reflecting surface reflect the electromagnetic wave to generate two beat frequencies delta f₁And Δ f₂Respectively processed by high-precision algorithm ZoomFFT, according to formulaWhere d is the radar-reflector distance, Δ f is the beat frequency, T is the FMCW frequency sweep time period, c is the speed of light, and B is the FMCW frequency sweep bandwidth. Determining distances d between the radar and the reflecting surfaces 1 and 2₁And d₂Theoretically, the difference between the two distances is

2. The radar reflecting device is a circular reflecting plate made of aluminum plates and divided into two layers, wherein the radius r of a reflecting surface of a first layer is₁5mm, radius r of the reflecting surface of the second layer₂The thickness is 30mm, but not limited to this material, size and shape, and a rectangular reflector plate may be selected, or a reflector plate of another material or another shape may be selected according to actual use conditions. Distance delta d between two aluminum plates_real≥6×d_resWherein the distance resolution d_resBy the formulaAnd (4) obtaining. During installation, the center of the aluminum plate is over against the center of the radar, the first layer of reflecting surface is close to the radar, and the second layer of reflecting surface is far away from the background by a distance d_min≥6×d_resBut is not limited to this distance.

3. The radar antenna adopts a circularly polarized lens antenna, a TX and an RX share an antenna unit, a Langer coupler orthogonally feeds power to the antenna unit to form circularly polarized electromagnetic waves, and the polarization mode of the TX is right-handed/left-handed, and the polarization mode of the RX is left-handed/right-handed.

4. Due to the existence of external interference, when the radar is powered on for the first time, the distance measured by the radar needs to be determined to be a preset reflector. Measuring the distance between the first and second reflecting surfaces of the reflector and the radar, preferably satisfying the condition d₂-d₁＝Δd_real±d_resThe reflector is a preset reflectorWhen the condition is not satisfied, the reflector with the maximum energy is selected as the reflector.

5. In the moving process of an object, two tracking tracks are formed by the radar passing through the first layer of reflecting plate and the second layer of reflecting plate, one reflecting plate is interfered by other false reflectors and lost, and the other reflecting plate passes through the other reflecting plate at delta d_real±d_resAnd searching nearby, and retrieving the two layers of reflecting plates again.

6. On the basis of the former condition, the signal energy and the signal-to-noise ratio of the first layer reflecting plate and the second layer reflecting plate are calculated, the distance between the first layer reflecting plate with large signal energy or the second layer reflecting plate with large signal energy and the radar is preferably an accurate value, and the final result is processed by linear filtering to realize accurate distance and speed information output.

7. On the basis of the above condition, when d is obtained₂-d₁From a known distance Δ d_realWhen the distance measurement result is inconsistent with the distance measurement result, the multipath influence can be judged, and the compensation algorithm can be adopted to compensate and correct the distance measured by the radar.

8. A radar transmits a waveform, one frame containing a plurality of FMCW waveforms (Chirp). When the distance of a static reflector is measured, firstly, accumulating time domain sampling signals of a plurality of FMCW waveforms (Chirp) so as to improve the signal-to-noise ratio of a system, and then calculating the accurate distance of the reflector through a frequency spectrum refining algorithm; the speed of the moving object relative to the reflecting plate is obtained through two-dimensional FFT.

9. The radar and the reflector are used in a matched mode and are used for application of elevator shaft position locating, logistics wharf warehouse hoisting position locating and conveyor belt vehicle position locating.

10. The method of 4/5/6/7/8/9 is used for elevator hoistway position location, logistics dock warehouse hoist position location, and conveyor belt vehicle position location applications.

The specific measurement process and principle are as follows:

the invention aims to provide a radar system device and a method, which can better solve the problems of multipath interference and reflection interference of other reflectors in a complex environment scene with lower cost and realization complexity, measure the moving distance and speed of a moving object relative to a reflector and realize millimeter-scale distance measurement precision.

The radar reflecting device is made of aluminum plate and is divided into two layers of reflecting surfaces, wherein the radius r of the first layer of reflecting surface₁5mm, radius r of the reflecting surface of the second layer₂30mm, distance delta d between two layers of aluminum plates_real≥6×d_res，d_resBy the formulaAnd (4) obtaining. During installation, the center of the aluminum plate is over against the center of the radar, the first layer of aluminum plate is close to the radar, and the second layer of aluminum plate is away from the background by a distance d_min≥6×d_res。

The antenna adopts a circularly polarized lens antenna, 3dB wave beams are less than or equal to +/-1.25 degrees, and reflection echo interference in other directions is reduced. The TX and the RX share the antenna unit, the Langer coupler orthogonally feeds the antenna unit, the polarization mode of the TX is right-handed/left-handed, the polarization mode of the RX is left-handed/right-handed, the transmission characteristic of circularly polarized electromagnetic waves is just utilized, right-handed/left-handed electromagnetic waves emitted by the transmitting antenna are reflected by a reflector, the excited electromagnetic waves are changed into left-handed/right-handed electromagnetic waves, and the receiving antenna just receives the electromagnetic waves in the same polarization mode. And for electromagnetic waves reflected by multiple paths, the polarization directions are opposite, polarization isolation has a certain inhibiting effect on the multiple path signals, and the influence of the multiple paths on the ranging precision is weakened. The working principle is shown in fig. 3, in which the wall 6 is the wall around the measuring place.

Radar initial power-on reflector finding: the radar receives the electromagnetic waves reflected by the first layer reflecting surface and the second layer reflecting surface of the reflector and generates two beat frequencies delta f₁And Δ f₂Respectively processed by high-precision algorithm ZoomFFT, according to formulaDetermining the distance d₁And d₂The difference between the two distances is theoreticallyBy d₁And d₂Relation solving traditional method for searching preset reflector by means of reflected signal strength and movingOne of the reflecting plates is interfered by other interference reflectors with equal distances, so that the error of the measured distance is overlarge, and even the preset reflector is lost.

The radar will transmit multiple FMCW waveforms (Chirp) during one measurement. Generally, the more the number of the transmitted waveforms is, the higher the system distance measurement and velocity measurement accuracy is. The FMCW signals transmitted by the radar at different times are represented by the following equation:

wherein A is_TkTo transmit signal amplitude, f₀，The number of waveforms N may preferably be 16, 32, 64, 128, 256, 512 for the initial frequency and initial phase of the FMCW signal.

After being reflected by the reflecting plate, the signals received at different moments are as follows:

A_Rkfor the k-th received signal amplitude, τ_i，The delay and the phase of the ith reflector path in the environment are shown, WGN (delta) is environment white noise, the amplitude mean value delta and the phase are random.

The system mixes the transmitted and received signals and filters out high frequency components. The intermediate frequency beat signal can be expressed as:

wherein the intermediate frequency of the reflector plate isBy passingThe distance dimension Fourier transform can calculate f_IiAnd the distance of the target can be represented by the formulaAs a result, c is the speed of light.

The intermediate frequency signals can be accumulated and then averaged:

after processing, the effective signal amplitude of the intermediate frequency signal is mean valueWhile the null signal amplitudes, the amplitudes due to the random phase of the noise cancel. The noise amplitude mean value will becomeThus, the signal-to-noise ratio of the system can be improved to N times of the previous signal-to-noise ratio. Thus, after a distance dimensional Fourier transform, a more accurate f can be calculated_IiAnd the ranging precision of the system is improved.

In general, f is calculated due to the barrier effect of the Fourier transform_IiOnly one rough value, the system ranging precision isWherein f is_sFor radar sampling rate, m is the number of single waveform sampling points. Furthermore, in order to improve the ranging precision of the system, a zoomFFT spectrum thinning algorithm can be adopted to interpolate the distance dimension Fourier transform result. The interpolation multiple is n, and m can be preferably 128, 256, 512 and 1024 and n can be preferably 64, 128, 256 and 512 in combination in consideration of comprehensive hardware processing capacity. At this time, the system ranging precision can be improved

Meanwhile, the result of the last step of transformation is saved in a system cache(RAM). After the transform result of the nth waveform is collected, a velocity-dimensional fourier transform may be performed on the stored data. The moving speed of the current moving object relative to the reflecting plate can be obtained by distance-speed two-dimensional transformation, and the precision isλ is the wavelength.

In particular, when the environment is subject to multipath interference. For a single reflection, the distance measured by the radar isd_realAs the real distance of the reflector from the radar, d_multThe range offset generated for multipath effects. Due to d_multFar less than radar range resolutionAt this time, the radar cannot judge whether the ranging result is affected by multipath, thereby causing the accuracy of ranging to be reduced.

The invention arranges two layers of reflecting plates, and the distance between the reflecting plates needs to satisfy delta d_real≥6×d_resSo as to avoid mutual interference between objects. In the process of one-time distance measurement, the distance d between two objects can be obtained through the steps₁＝d_real1+d_mult1And d₂＝d_real2+d_mult2The difference between the two reflecting plates is d₁₂＝d₁-d₂＝d_real1-d_real2+d_mult1-d_mult2＝Δd_real+d_mult12Wherein, Δ d_realThe spacing is known for two layers of reflector plates. When d is₁₂＝Δd_realAnd meanwhile, the current result can be judged to be accurate and not influenced by multipath interference. When d is₁₂≠Δd_realIn the process, interference influence exists in the ranging result, and the next compensation correction is needed.

In the invention, the compensation correction is carried out by taking the measured reflection energy or signal-to-noise ratio of the two layers of reflecting plates as a weight. Setting two layers of reflecting plates to reflect energy as p₁And p₂Signal to noise ratio of s₁And s₂. Obtaining a corrected ranging result through the following formula:

or:

typically, the system only requires that one valid ranging result be output. In this case, a ranging result with a large reflected energy or signal-to-noise ratio may be preferably output as a final result.

In the application of distance measurement of moving objects, the invention is beneficial to the tracking and positioning of the distance measurement reflector by arranging two layers of reflecting plates. Under the condition of a traditional single reflector, the target is usually tracked by depending on the intensity of energy reflected by an object, and the moving process is easily interfered by other objects, so that the reflector is lost. In the invention, when one of the reflecting plates is interfered and lost, the distance relationship between the two reflecting plates can be determined at delta d_real±d_resAnd nearby, searching for the reflecting object meeting the distance relation again. And as a preset reflector, the tracking and ranging process is ensured to be continuous.

In practice, the final ranging result may be disturbed due to mechanical vibration or other environmental factors. The invention adopts the following steps to carry out linear filtering processing, can reduce the disturbance of the result and realize stable output:

1. predicting X (k | k-1) for the state according to the result at the moment k-1;

2. covariance matrix P prediction, P (k | k-1) ═ P (k-1) + Q;

3. calculating linear gain K, K ═ P (K | K-1)/(P (K | K-1) + R);

4. state X update, X (K) ═ X (K-1) + K (in (K) -X (K-1));

5. covariance matrix update, P (K) × P (K | K-1);

6. outputting a processing result, out (k) ═ x (k);

in the process, Q is the process noise variance and R is the measurement noise variance. The method can be adjusted according to application environment, and the method preferably comprises the following steps: q is 0.001 and R is 0.002 to realize stable output of distance measurement result.

The first embodiment is as follows:

1. the radar reflecting device is made of an aluminum plate or other metals and is divided into two layers, wherein the reflecting area of the first layer is smaller than that of the second layer;

2. the distance between the two layers of reflecting plates can be adjusted according to practical application, and the minimum distance d between the second layer of reflecting surface and the mounting surface_min≥6×d_resThe minimum distance delta d between the first layer reflection surface and the second layer reflection surface_real≥6×d_res. Preventing mutual interference between reflecting objects;

3. the center of the reflecting device is over against the center of the radar, the first layer of reflecting surface is close to the radar, and the second layer of reflecting surface is far away from the radar;

4. the radar antenna adopts a circularly polarized lens antenna, and 3dB wave beams are less than or equal to +/-1.25 degrees;

5. the radar antenna is designed by adopting a receiving and transmitting shared antenna unit, the receiving and transmitting wave beams are symmetrical, and the wave beams point to the direction of 0 degree;

the Langer coupler orthogonally feeds the antenna units, the polarization mode of the transmitting antenna is right-handed/left-handed, and the polarization mode of the receiving antenna is left-handed/right-handed, so that polarization isolation is realized;

7. the radar will transmit multiple FMCW waveforms, the number N of which may preferably be 16, 32, 64, 128, 256, 512, during one measurement.

8. The radar mixes the transmitted and received signals, the filter filters out high frequency components to obtain an intermediate frequency signal f_I；

9. The intermediate frequency signal is subjected to time domain accumulation averaging noise reduction processing, and the effective signal amplitude is an average valueNoise amplitude mean value of

10. By means of m-point distance dimension Fourier transform, the intermediate frequency f of the two layers of reflecting plates can be calculated₁And f₂The number of Fourier transform points canPreferably 128, 256, 512, 1024, with a distance accuracy of

11. Interpolating the Fourier transform result by adopting a ZoomFFT algorithm to obtain a refined frequency f₁' and f₂'. The interpolation multiple of the algorithm is n, n can be optimized to 64, 128, 256 and 512 in consideration of comprehensive hardware processing capacity, and the refined distance precision is

12. The Fourier transform result of each waveform is stored in a system buffer (RAM). And after the transformation result of the Nth waveform is collected, performing velocity dimension Fourier transformation. The speed v of the current moving object relative to the reflecting plate is obtained through distance-speed two-dimensional transformation, and the precision is

13. In the application of moving object distance measurement, after one reflecting plate is interfered and lost, the distance relationship between two reflecting plates can be determined according to the delta d_real±d_resAnd searching for a reflector meeting the distance relation again nearby to serve as a preset reflector.

14. Distance d between two reflecting plates₁＝d_real1+d_mult1And d₂＝d_real2+d_mult2. The difference between the two distances is d₁₂＝d_real1-d_real2+d_mult1-d_mult2＝Δd_real+d_mult12. When d is₁₂＝Δd_realAnd meanwhile, the current result can be judged to be accurate and not influenced by multipath interference. When d is₁₂≠Δd_realIn the process, interference influence exists in the ranging result, and the next compensation correction is needed.

15. The result is corrected in the multipath case by the following equation:

or:

16. in some cases, the system only requires that one valid ranging result be output. At this time, a ranging result with large reflection energy or signal-to-noise ratio may be preferably output as a final result;

17. linear filtering processing is adopted, so that result disturbance is reduced, and stable output is realized;

18. the linear filtering process and the measured noise variance are preferably: q ═ 0.001 and R ═ 0.002.