Method for detection using frequency modulated continuous wave and laser radar

Abstract

The present invention provides a method for detection using a frequency modulated continuous wave, comprising: S11: emitting a detection wave according to a preset sweep waveform to detect a target object; S12: receiving an echo after the detection wave is reflected from the target object; and S13: obtaining the distance and / or speed of the target object based on the echo and the detection wave, wherein one cycle of the preset sweep waveform consists of a rising edge, a horizontal area, and a falling edge.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric detection, and in particular to a method for detecting using frequency modulated continuous waves and a laser radar. Background Art

[0002] Figure 1 The structure of a frequency modulated continuous wave (FMCW) radar (FMCW radar for short) is shown. Coupler 1 splits frequency modulated light (the modulation unit is not shown) into local oscillator light and probe light. The probe light passes through a collimator and then scans space through a galvanometer. Probe light reflected by a target (probe light echo) is reflected by the galvanometer and received by the collimator. It then re-enters the system and coherently beats with the local oscillator light. The frequency of the beat signal (always positive) can be used to determine the target's range and velocity. Figure 1 The probe light echo is received by the detector after passing through the circulator. The probe light echo is then mixed with the local oscillator light in the coupler 2. The processing unit includes, for example, a low-pass filter unit and an A / D sampling unit. After the probe light echo and the local oscillator light are mixed, a low-pass filter is applied to obtain a beat frequency signal. After analog-to-digital conversion, a fast Fourier transform (FFT) is performed to obtain the frequency and corresponding amplitude of the beat frequency signal between the transmitted signal (probe light) and the received signal (probe light echo).

[0003] Since the echo light has a time delay relative to the local oscillator light, the actual effective beat frequency time period is the difference between the current linear frequency modulation duration and the echo delay time, and the rest of the section is the invalid beat frequency area caused by the time delay, such as Figure 2 shown.

[0004] In order to obtain the delay and Doppler frequency shift of the echo signal at the same time, a combination of two linear sweep signals with different slopes can be used. The most common one is a triangle wave, such as Figure 3A and Figure 3B As shown, Figure 3A In order to ignore the Doppler shift, Figure 3B To consider the Doppler shift.

[0005] The frequencies f1 and f2 of the beat signals at the rising and falling edges of the triangle wave can be expressed as:

[0006] f1=|f Z -f v | (1)

[0007] f2=|f Z +f v | (2)

[0008] Among them, f ZThe frequency shift of the rising / falling edge without considering the Doppler shift (i.e., the frequency difference) is as follows: Figure 3A As shown, f v is the Doppler frequency shift. According to the above formulas (1) and (2), four groups of f Z With f v Solution. Since the distance is always greater than zero: f Z >0, two groups of solutions can be eliminated. However, as shown in 4, for possible signal 1, |f v |>|f Z |, for possible signal 2, |f v |<|f Z |, the echo signals of both have the same beat frequency as the local signal, making them indistinguishable. Therefore, triangle wave FM cannot handle the measurement of close-range, high-speed objects.

[0009] At the same time, FMCW lidar also faces the problem of multiple echoes. For example, when the galvanometer scans too quickly and is at the edge of an object, the rising and falling edge beat signals include different objects in front and behind. When the galvanometer scans too slowly and is at the edge of an object, the rising and falling edge beat signals are likely to carry reflection information from multiple objects in front and behind, which brings up the problem of how to correctly match them.

[0010] The contents of the background technology section are merely technologies known to the public and do not necessarily represent the existing technologies in this field. Summary of the Invention

[0011] In view of at least one problem in the prior art, the present invention provides a method for detecting using a frequency modulated continuous wave, comprising:

[0012] S11: transmitting a detection wave according to a preset sweep waveform to detect the target object;

[0013] S12: receiving an echo after the detection wave is reflected on the target object; and

[0014] S13: Obtaining the distance and / or speed of the target object according to the echo and the detection wave,

[0015] One cycle of the preset sweep waveform consists of a rising edge, a horizontal area and a falling edge.

[0016] According to one aspect of the present invention, in one cycle of the preset sweep waveform, the horizontal region is connected to the rising edge and the falling edge.

[0017] According to one aspect of the present invention, in one cycle of the preset sweep waveform, the horizontal region is separated from the rising edge and the falling edge.

[0018] According to one aspect of the present invention, step S13 includes:

[0019] S131: Determine the frequency f of the beat signal between the detection wave and the echo in the horizontal region d Whether the corresponding amplitude is greater than or equal to the amplitude threshold;

[0020] S132: according to the frequency f of the beat signal between the detection wave and the echo in the horizontal area d Whether the corresponding amplitude is greater than or equal to the amplitude threshold, the distance frequency shift component f is calculated according to the preset method. z and the velocity frequency shift component f v ;and

[0021] S133: Based on the distance frequency shift component f z and the velocity frequency shift component f v , calculate the distance and speed of the target object.

[0022] According to one aspect of the present invention, step S132 includes:

[0023] When the frequency f of the beat signal between the detection wave and the echo in the horizontal region d When the corresponding amplitude is greater than or equal to the amplitude threshold, determine which one of |f2+f1| / 2 and |f2-f1| / 2 is closer to f d , where f1 is the absolute value of the frequency difference between the detection wave and the echo within the rising edge range, and f2 is the absolute value of the frequency difference between the detection wave and the echo within the falling edge range,

[0024] When |f2-f1| / 2 is closer to fd, the distance frequency shift component fz and the velocity frequency shift component f are calculated as follows: v :

[0025] When |f2+f1| / 2 is closer to f d When the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v :If f1>f2, then If f1<f2, then

[0026] According to one aspect of the present invention, the method further comprises:

[0027] When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist;

[0028] When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

[0029] According to one aspect of the present invention, when there are multiple echoes, echo matching is performed in the following manner: selecting or A set of f1 and f2 is selected, and the other f1 and f2 are discarded.

[0030] According to one aspect of the present invention, the step S103 includes: when the frequency f of the beat signal between the detection wave and the echo in the horizontal area is d When the corresponding amplitude is less than the amplitude threshold, the distance frequency shift component f is calculated as follows: z and the velocity frequency shift component f v :

[0031] According to one aspect of the present invention, the method further comprises:

[0032] When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist;

[0033] When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

[0034] According to one aspect of the present invention, when multiple echoes exist, echo matching is performed in the following manner:

[0035] determining the resulting frequency shift F based on the movement speed of the device emitting the detection wave;

[0036] choose The set of f1 and f2 closest to F is selected, and the others are discarded.

[0037] The present invention also provides a laser radar, comprising:

[0038] a transmitting unit configured to transmit a detection wave according to a preset sweep waveform, wherein one cycle of the preset sweep waveform consists of a rising edge, a horizontal area, and a falling edge;

[0039] a scanning unit configured to receive the detection wave and emit the detection wave after reflection to detect a target object;

[0040] a receiving unit, wherein the echo of the detection wave reflected from the target object is incident on the receiving unit after being reflected by the scanning unit; and

[0041] A processing unit is coupled to the transmitting unit and the receiving unit, and the processing unit is configured to obtain the distance and / or speed of the target object according to the echo and the detection wave.

[0042] According to one aspect of the present invention, in one cycle of the preset sweep waveform, the horizontal region is connected to the rising edge and the falling edge.

[0043] According to one aspect of the present invention, in one cycle of the preset sweep waveform, the horizontal region is separated from the rising edge and the falling edge.

[0044] According to one aspect of the present invention, the processing unit is configured to:

[0045] Determine the frequency f of the beat signal between the detection wave and the echo in the horizontal area d Whether the corresponding amplitude is greater than or equal to the amplitude threshold;

[0046] According to the frequency f of the beat signal between the detection wave and the echo in the horizontal area d Whether the corresponding amplitude is greater than or equal to the amplitude threshold, the distance frequency shift component f is calculated according to the preset method. z and the velocity frequency shift component f v ;and

[0047] According to the distance frequency shift component f z and the velocity frequency shift component f v , calculate the distance and speed of the target object.

[0048] According to one aspect of the present invention, the processing unit is configured to:

[0049] When the frequency f of the beat signal between the detection wave and the echo in the horizontal region d When the corresponding amplitude is greater than or equal to the amplitude threshold, determine which one of |f2+f1| / 2 and |f2-f1| / 2 is closer to f d , where f1 is the absolute value of the frequency difference between the detection wave and the echo within the rising edge range, and f2 is the absolute value of the frequency difference between the detection wave and the echo within the falling edge range,

[0050] When |f2-f1| / 2 is closer to f d When the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v :

[0051] When |f2+f1| / 2 is closer to f dWhen the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v :If f1>f2, then If f1<f2, then

[0052] According to one aspect of the present invention, the processing unit is configured to:

[0053] When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist;

[0054] When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

[0055] According to one aspect of the present invention, the processing unit is configured to: when there are multiple echoes, perform echo matching in the following manner: select or A set of f1 and f2 is selected, and the other f1 and f2 are discarded.

[0056] According to one aspect of the present invention, the processing unit is configured to: when the frequency f of the beat signal between the detection wave and the echo in the horizontal region is d When the corresponding amplitude is less than the amplitude threshold, the distance frequency shift component f is calculated as follows: z and the velocity frequency shift component f v :

[0057] According to one aspect of the present invention, the processing unit is configured to:

[0058] When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist;

[0059] When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

[0060] According to one aspect of the present invention, the processing unit is configured to: when multiple echoes exist, perform echo matching in the following manner:

[0061] determining the resulting frequency shift F based on the movement speed of the device emitting the detection wave;

[0062] choose The set of f1 and f2 closest to F is selected, and the others are discarded.

[0063] The present invention aims to solve the problems of demodulation errors in the current FMCW laser radar based on triangular wave frequency sweep, which cannot handle the measurement of close-range high-speed objects, as well as the multi-echo problem of the FMCW laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0065] Figure 1 A structural diagram of a frequency modulated continuous wave radar is shown;

[0066] Figure 2 Shown Figure 1 Schematic diagram of effective beat frequency area and invalid beat frequency area in FMCW radar;

[0067] Figure 3A The figure shows the probe wave and echo when the triangular wave sweep is used without considering the Doppler shift.

[0068] Figure 3B The figure shows the probe wave and the echo when the Doppler shift is taken into account.

[0069] Figure 4 This shows the possible demodulation errors when using triangular wave sweep frequency to detect close-range high-speed objects.

[0070] Figure 5 A method for detecting using a frequency modulated continuous wave according to an embodiment of the present invention is shown;

[0071] Figure 6A A schematic diagram showing a preset frequency sweep waveform according to an embodiment of the present invention is shown;

[0072] Figure 6B shows a schematic diagram of a preset frequency sweep waveform according to another embodiment of the present invention;

[0073] Figure 6C shows a schematic diagram of a preset frequency sweep waveform according to yet another embodiment of the present invention;

[0074] Figure 7 A schematic diagram showing the frequency and corresponding amplitude of a beat signal between a horizontal region detection wave and an echo according to an embodiment of the present invention;

[0075] Figure 8 、 Figure 9 and Figure 10 Detection waves and echoes in three situations according to an embodiment of the present invention are respectively shown;

[0076] Figure 11 FIG. 4 shows a schematic diagram of performing multi-echo matching according to an embodiment of the present invention; and

[0077] Figure 12 A schematic diagram of a laser radar according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0078] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0079] In the description of the present invention, it should be understood that terms such as "center," "longitudinal," "transverse," "length," "width," "thickness," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," and "counterclockwise" are used to indicate positions or relationships based on those shown in the accompanying drawings. These terms are intended solely to facilitate description and simplify the description of the present invention and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations of the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed to indicate or imply relative importance or to implicitly specify the number of the technical features referred to. Thus, features designated "first" or "second" may explicitly or implicitly include one or more of the designated features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0080] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, removable, or integral connections; mechanical, electrical, or intercommunication connections; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0081] In the present invention, unless otherwise expressly specified or limited, "above" or "below" a first feature may include direct contact between the first and second features, or may include contact between the first and second features not in direct contact but via another feature between them. Furthermore, "above," "above," and "above" a first feature may include both directly above and diagonally above the second feature, or simply indicate that the first feature is at a higher level than the second feature. "Below," "below," and "below" a first feature may include both directly above and diagonally above the second feature, or simply indicate that the first feature is at a lower level than the second feature.

[0082] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0083] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0084] Figure 5 A method 10 for detecting using a frequency modulated continuous wave according to an embodiment of the present invention is shown and will be described in detail below with reference to the accompanying drawings.

[0085] In step S11 , a detection wave is emitted according to a preset sweep waveform to detect a target object, wherein one cycle of the preset sweep waveform consists of a rising edge, a horizontal area, and a falling edge.

[0086] Figure 6A FIG. 1 shows a schematic diagram of a preset frequency sweep waveform according to an embodiment of the present invention. Figure 6A As shown, one cycle T of the preset sweep waveform includes three sections, namely, a rising edge, a horizontal area, and a falling edge. Figure 6A In the preset sweep waveform, the horizontal area is connected to the rising edge and the falling edge, that is, the frequency value of the horizontal area is substantially equal to the maximum value of the frequency value of the rising edge and the falling edge. FIG6B shows a schematic diagram of a preset sweep waveform according to another embodiment of the present invention. Figure 6BAs shown, the horizontal area is separated from the rising edge and the falling edge. The frequency value of the horizontal area in the figure is different from the maximum value of the frequency value of the rising edge and the falling edge. At the same time, the maximum value of the frequency value of the rising edge and the falling edge can be the same or different. Figure 6B Alternatively, the horizontal area may also be located above the rising edge and the falling edge, as shown in FIG. Figure 6C As shown, these are all within the scope of the present invention.

[0087] The present invention can be used Figure 6A 、 Figure 6B and Figure 6C The preset sweep waveforms shown in the figure have the same demodulation methods. Figure 6A The preset sweep waveform shown is used as an example for description.

[0088] In step S12, the probe wave is emitted according to the preset sweep waveform, and the probe wave is diffusely reflected on the target object. Part of the echo returns and is received by the detection device and converted into an electrical signal.

[0089] In step S13: according to the echo and the detection wave, the distance and / or speed of the target object is obtained. That is, the frequency and corresponding amplitude of the beat signal of the echo and the detection wave in each segment are obtained by using Fast Fourier Transform (FFT), and then the distance and / or speed of the target object is obtained based on the frequency of the beat signal. In the present invention, by adopting a three-segment waveform sweep, including a rising edge + a horizontal area + a falling edge, and taking the three segments as a cycle, it is possible to solve the problem of misjudgment and / or multi-echo matching caused by the reversal of the echo frequency (relative to the detection wave) of a close-range high-speed object. The demodulation process according to a preferred embodiment of the present invention is described in detail below.

[0090] According to one aspect of the present invention, step S13 includes:

[0091] Step S131: Determine the frequency f of the beat signal between the detection wave and the echo in the horizontal region. d Whether it is greater than or equal to the amplitude threshold.

[0092] The frequency-time waveform of the echo is usually the same as or close to that of the probe wave. In the present invention, the frequency sweep waveform of the probe wave includes a rising edge, a horizontal region and a falling edge, so the frequency waveform of the echo also includes a rising edge, a horizontal region and a falling edge. Figure 7 The waveform of the frequency sweep of the detection wave and the frequency waveform of the echo are shown. After receiving the echo, the echo and the detection wave are beat by frequency. After the transformation operation, the frequency and corresponding amplitude of the beat signal of the echo and the detection wave at the rising edge, horizontal area and falling edge are obtained. Then the frequency f of the beat signal in the horizontal area is read.d and its corresponding amplitude, the frequency f of the beat signal in the horizontal area d That is, the absolute value of the frequency difference between the detection wave and the echo in the horizontal area, and then the frequency f of the beat signal in the horizontal area is determined. d Whether the corresponding amplitude is greater than or equal to the amplitude threshold.

[0093] In the present invention, the frequency f of the beat signal between the horizontal region detection wave and the echo is d and the velocity frequency shift component f v are closely related, their absolute values ​​are the same, but f d Always positive, f v The value may be positive or negative according to its directionality. In step S132: according to the frequency f of the beat signal between the detection wave and the echo in the horizontal area d Whether the corresponding amplitude is greater than or equal to the amplitude threshold, the distance frequency shift component f is calculated according to the preset method. z and the velocity frequency shift component f v The following describes a calculation method according to a preferred embodiment of the present invention.

[0094] Figure 7 The diagram shows the frequency of the beat signal between the horizontal detection wave and the echo and its corresponding amplitude. d The corresponding amplitude is A d , the amplitude threshold is A dth ,A in the figure d Greater than A dth The amplitude threshold is determined by the noise amplitude when there is no echo, for example, A dth It is 6 times the noise amplitude when there is no echo, and can also be set according to actual conditions.

[0095] When the frequency f of the beat signal between the detection wave and the echo in the horizontal region d When the corresponding amplitude is greater than or equal to the amplitude threshold, determine which one of |f2+f1| / 2 and |f2-f1| / 2 is closer to f d , where f1 is the absolute value of the frequency difference between the detection wave and the echo within the rising edge range, and f2 is the absolute value of the frequency difference between the detection wave and the echo within the falling edge range.

[0096] When |f2-f1| / 2 is closer to f d When |f2-f1| / 2≈f d When |f Z |>|f v|, indicating that there is no frequency sign change on the upper and lower edges (i.e., on the rising edge, the echo is below the detection wave; on the falling edge, the echo is above the detection wave). At this time, there is a Doppler frequency shift (velocity frequency shift component), but the velocity frequency shift component f v Less than the distance frequency shift component f z , the frequencies of the detection wave and the echo are as follows Figure 8 As shown, the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v :

[0097] When |f2+f1| / 2 is closer to f d When |f2+f1| / 2≈f d When |f Z |<|f v |, at this time, the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v :If f1>f2, there is Doppler frequency shift, but the velocity frequency shift component f v Greater than the distance frequency shift component f z , and the velocity frequency shift component f v is negative, the frequency of the detection wave and the echo wave is as follows Figure 9 As shown in the figure (on the rising edge, the echo is below the detection wave; on the falling edge, the echo is below the detection wave and the falling edge is reversed), then If f1<f2, there is Doppler frequency shift, but the velocity frequency shift component f v Greater than the distance frequency shift component f z , and the velocity frequency shift component f v is positive, the frequency of the detection wave and the echo is as follows Figure 10 As shown in the figure (on the rising edge, the echo is above the detection wave, and the rising edge is reversed; on the falling edge, the echo is above the detection wave), then

[0098] According to one aspect of the present invention, step S132 includes: when the frequency f of the beat signal between the detection wave and the echo in the horizontal area is d When the corresponding amplitude is less than the amplitude threshold, that is, A d Less than A dth , it can be considered that there is no f d This situation is usually caused by long distance, small echo signal or too slow movement speed. In this case, the distance frequency shift component f can be calculated as follows z and the velocity frequency shift component f v :

[0099] In step S133: according to the distance frequency shift component f z and the velocity frequency shift component f v , calculate the distance and speed of the target object. After obtaining the distance frequency shift component f z and the velocity frequency shift component f v After that, they can be used to calculate the distance and speed of the target object respectively. In the lidar system, the distance coefficient factor_z and the speed coefficient factor_v are the pre-calibrated values. z and the velocity frequency shift component f v After that, you can multiply the distance coefficient factor_z and the speed coefficient factor_v respectively to calculate the distance and speed of the target object.

[0100] Figure 8 、 Figure 9 and Figure 10 The figure shows only the frequency waveform of one echo. During LiDAR detection, if the galvanometer scans too quickly and is at the edge of an object, multiple echo frequency waveforms will appear. The rising and falling edge beat signals include different objects in front and behind. If the galvanometer scans too slowly and is at the edge of an object, the rising and falling edge beat signals may contain reflection information from multiple objects in front and behind, thus requiring correct matching.

[0101] According to one embodiment of the present invention, it is possible to determine whether there are multiple echoes, and if there are multiple echoes, matching is performed, that is, the matching f1 and f2 groups within the rising edge range and the falling edge range are retained. For example, when the frequency f of the beat signal between the detection wave and the echo in the horizontal area is d When the corresponding amplitude is greater than or equal to the amplitude threshold, if either the number of absolute values ​​of frequency differences f1 within the rising edge range or the number of absolute values ​​of frequency differences f2 within the falling edge range is greater than 1, it is considered that multiple echoes exist (for example, Figure 4 As shown in the case), a match is required, then just look for or A set of f1 and f2 is considered to be a matching pair. The pair of f1 and f2 that meets the above conditions is retained and the other f1 and f2 are discarded. Figure 11 Figure 1 shows a schematic diagram of multi-echo matching, with the top showing the rising edge beat frequency spectrum and the bottom showing the falling edge beat frequency spectrum. As shown in Figure 11, two echoes f1 are generated on the rising edge, and two echoes f2 are generated on the falling edge. Through the above matching method, the first echo on the rising edge and the first echo on the falling edge meet the matching relationship and are retained. Other echoes are excluded for subsequent data processing.

[0102] When the frequency f of the beat signal between the detection wave and the echo in the horizontal region d When the corresponding amplitude is less than the amplitude threshold, and the number of absolute values ​​of frequency differences f1 within the rising edge range and / or the number of absolute values ​​of frequency differences f2 within the falling edge range is greater than 1, the generated frequency shift F can be determined based on the moving speed of the device emitting the detection wave, and then the frequency shift F can be selected so that The set of f1 and f2 closest to F is selected, and the others are discarded. In this case, the frequency shift caused by the relative speed of the surrounding objects due to the vehicle's forward movement is F. F can be obtained from the vehicle's speed sensor or by real-time analysis of the speed of objects in the environment. For speed-based multi-echo matching, echo signals from stationary objects are prioritized among the multi-echoes.

[0103] Therefore, in the presence of multiple echoes, matching is performed in the above manner, retaining a set of f1 and f2, and then the range frequency shift component f is calculated separately in the following manner z and the velocity frequency shift component f v：

[0104] In the embodiment of the present invention described above, a three-segment periodic waveform is used for frequency sweeping, which can solve the misalignment problem during measurement of close-range high-speed objects and the problem of multi-echo matching caused by the existing triangular wave frequency sweeping.

[0105] Figure 12 A laser radar 100 according to an embodiment of the present invention is shown, which can be used to implement the above method 10. Detailed description will be given below with reference to the accompanying drawings.

[0106] like Figure 12 As described above, the laser radar 100 includes a transmitting unit 101, a receiving unit 102, a scanning unit 103, and a processing unit 104. The transmitting unit 101 is configured to transmit a detection wave L1 according to a preset sweep waveform, wherein one cycle of the preset sweep waveform consists of a rising edge, a horizontal area, and a falling edge. Figure 6A 、 6B and 6C. The detection wave L1 is incident on the scanning unit 103. The scanning unit 103 may include a galvanometer or a rotating mirror. The detection wave L1 is reflected in different directions by swinging or rotating and then emitted into the surrounding space, covering the field of view of the laser radar, for detecting the target object OB. The detection wave L1 is diffusely reflected on the target object, and the echo L1' returns to the laser radar 100, which can also be received by the scanning unit 103 and reflected to the receiving unit 102. The receiving unit 102 includes a photodetector, which is configured to receive the echo L1' reflected by the detection wave L1 on the target object OB and convert it into an electrical signal. The transmitting unit 101 and the receiving unit 102 also include a beam shaping unit, such as Figure 1 The collimation unit shown is used to collimate the outgoing detection wave or echo. The processing unit 103 is coupled to the transmitting unit 101 and the receiving unit 102, and the processing unit 103 is configured to obtain the distance and / or speed of the target object based on the echo L1' and the detection wave L1. It is easy for those skilled in the art to understand that Figure 12 The figure shows the functional block diagram of the laser radar 100, rather than the actual structure diagram. The laser radar 100 can preferably be used Figure 1 The structure of the FMCW laser radar shown in the figure, wherein the transmitting unit 101 may include a laser and a signal generating unit, such as a DAC that generates a modulation waveform, wherein the laser emits a laser beam, and the signal generating unit is used to generate a preset sweep waveform, and then use the preset sweep waveform to modulate the laser beam to generate a detection wave L1. The receiving unit 102 may include Figure 1 The galvanometer and collimator unit shown in the figure are used to receive the echo L1' and reflect it to the collimator unit, and the collimator unit converges the echo L1'. The processing unit 103 performs calculation and processing based on the detection wave L1 and the echo L1'.

[0107] According to one aspect of the present invention, in one cycle of the preset sweep waveform, the horizontal area is connected to the rising edge and the falling edge, such as Figure 6A The waveform shown; or the horizontal area is separated from the rising edge and the falling edge, such as Figure 6B and Figure 6C The waveform shown.

[0108] According to one aspect of the present invention, the processing unit is configured to:

[0109] Determine the frequency f of the beat signal between the detection wave and the echo in the horizontal area d Whether the corresponding amplitude is greater than or equal to the amplitude threshold;

[0110] According to the frequency f of the beat signal between the detection wave and the echo in the horizontal area d Whether the corresponding amplitude is greater than or equal to the amplitude threshold, the distance frequency shift component f is calculated according to the preset method. z and the velocity frequency shift component f v ;and

[0111] According to the distance frequency shift component f z and the velocity frequency shift component f v , calculate the distance and speed of the target object.

[0112] According to one aspect of the present invention, the processing unit is configured to:

[0113] When the frequency f of the beat signal between the detection wave and the echo in the horizontal region d When the corresponding amplitude is greater than or equal to the amplitude threshold, determine which one of |f2+f1| / 2 and |f2-f1| / 2 is closer to f d , where f1 is the absolute value of the frequency difference between the detection wave and the echo within the rising edge range, and f2 is the absolute value of the frequency difference between the detection wave and the echo within the falling edge range,

[0114] When |f2-f1| / 2 is closer to f d When the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v :

[0115] When |f2+f1| / 2 is closer to f d When the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v :If f1>f2, then If f1<f2, then

[0116] According to one aspect of the present invention, the processing unit is configured to:

[0117] When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist;

[0118] When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

[0119] According to one aspect of the present invention, the processing unit is configured to: when there are multiple echoes, perform echo matching in the following manner: select or A set of f1 and f2 is selected, and the other f1 and f2 are discarded.

[0120] According to one aspect of the present invention, the processing unit is configured to: when the frequency f of the beat signal between the detection wave and the echo in the horizontal region is d When the corresponding amplitude is less than the amplitude threshold, the distance frequency shift component f is calculated as follows: z and the velocity frequency shift component f v :

[0121] According to one aspect of the present invention, the processing unit is configured to:

[0122] When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist;

[0123] When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

[0124] According to one aspect of the present invention, the processing unit is configured to: when multiple echoes exist, perform echo matching in the following manner:

[0125] determining the resulting frequency shift F based on the movement speed of the device emitting the detection wave;

[0126] choose The set of f1 and f2 closest to F is selected, and the others are discarded.

[0127] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for detecting using a frequency modulated continuous wave, comprising: S11: transmitting a detection wave according to a preset sweep waveform to detect the target object; S12: receiving an echo after the detection wave is reflected on the target object; and S13: Obtaining the distance and / or speed of the target object according to the echo and the detection wave, Wherein one cycle of the preset sweep waveform is composed of a rising edge, a horizontal area and a falling edge; Wherein said step S13 comprises: S131: Determine the frequency f of the beat signal between the detection wave and the echo in the horizontal region d Whether the corresponding amplitude is greater than or equal to the amplitude threshold; S132: according to the frequency f of the beat signal between the detection wave and the echo in the horizontal area d Whether the corresponding amplitude is greater than or equal to the amplitude threshold, the distance frequency shift component f is calculated according to the preset method. z and the velocity frequency shift component f v ;and S133: Based on the distance frequency shift component f z and the velocity frequency shift component f v , calculate the distance and speed of the target object. 2 . The method according to claim 1 , wherein in one cycle of the preset sweep waveform, the horizontal region is connected to the rising edge and the falling edge. 3 . The method according to claim 1 , wherein in one cycle of the preset sweep waveform, the horizontal region is separated from the rising edge and the falling edge.

4. The method according to claim 1, wherein the step S132 comprises: When the frequency f of the beat signal between the detection wave and the echo in the horizontal region d When the corresponding amplitude is greater than or equal to the amplitude threshold, it is judged and Which one is closer to f d , where f1 is the absolute value of the frequency difference between the detection wave and the echo within the rising edge range, and f2 is the absolute value of the frequency difference between the detection wave and the echo within the falling edge range, when Closer to f d When the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v : , ; when Closer to f d When the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v :like ,but , ;like ,but , .

5. The method according to claim 1 or 4, further comprising: When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist; When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

6. The method of claim 5, wherein when multiple echoes exist, echo matching is performed by selecting an echo that satisfies or A set of f1 and f2 is selected, and the other f1 and f2 are discarded.

7. The method according to claim 1, wherein the step S132 comprises: When the frequency f of the beat signal between the detection wave and the echo in the horizontal region d When the corresponding amplitude is less than the amplitude threshold, the distance frequency shift component f is calculated as follows: z and the velocity frequency shift component f v : , , where f1 is the absolute value of the frequency difference between the detection wave and the echo within the rising edge range, and f2 is the absolute value of the frequency difference between the detection wave and the echo within the falling edge range.

8. The method of claim 7, further comprising: When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist; When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

9. The method according to claim 8, wherein when multiple echoes exist, echo matching is performed by: determining the resulting frequency shift F based on the movement speed of the device emitting the detection wave; choose The set of f1 and f2 closest to F is selected, and the others are discarded.

10. A laser radar comprising: a transmitting unit configured to transmit a detection wave according to a preset sweep waveform, wherein one cycle of the preset sweep waveform consists of a rising edge, a horizontal area, and a falling edge; a scanning unit configured to receive the detection wave and emit the detection wave after reflection to detect a target object; a receiving unit, wherein the echo of the detection wave reflected from the target object is incident on the receiving unit after being reflected by the scanning unit; and a processing unit coupled to the transmitting unit and the receiving unit, the processing unit being configured to obtain a distance and / or a speed of the target object according to the echo and the detection wave; Wherein the processing unit is configured to: Determine the frequency f of the beat signal between the detection wave and the echo in the horizontal area d Whether the corresponding amplitude is greater than or equal to the amplitude threshold; According to the frequency f of the beat signal between the detection wave and the echo in the horizontal area d Whether the corresponding amplitude is greater than or equal to the amplitude threshold, the distance frequency shift component f is calculated according to the preset method. z and the velocity frequency shift component f v ;and According to the distance frequency shift component f z and the velocity frequency shift component f v , calculate the distance and speed of the target object.

11. The laser radar as claimed in claim 10, wherein in one cycle of the preset sweep waveform, the horizontal area is connected to the rising edge and the falling edge. 12 . The laser radar as claimed in claim 10 , wherein in one cycle of the preset sweep waveform, the horizontal area is separated from the rising edge and the falling edge.

13. The laser radar according to claim 10, wherein the processing unit is configured to: When the frequency f of the beat signal between the detection wave and the echo in the horizontal region d When the corresponding amplitude is greater than or equal to the amplitude threshold, it is judged and Which one is closer to f d , where f1 is the absolute value of the frequency difference between the detection wave and the echo within the rising edge range, and f2 is the absolute value of the frequency difference between the detection wave and the echo within the falling edge range, when Closer to f d When the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v : , ; when Closer to f d When the distance frequency shift component f is calculated as follows z and the velocity frequency shift component f v :like ,but , ;like ,but , .

14. The laser radar according to claim 10 or 13, wherein the processing unit is configured to: When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist; When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

15. The laser radar according to claim 14, wherein the processing unit is configured to: when there are multiple echoes, perform echo matching by: selecting an echo that satisfies or A set of f1 and f2 is selected, and the other f1 and f2 are discarded.

16. The laser radar according to claim 10, wherein the processing unit is configured to: when the frequency f of the beat signal between the detection wave and the echo in the horizontal area is d When the corresponding amplitude is less than the amplitude threshold, the distance frequency shift component f is calculated as follows: z and the velocity frequency shift component f v : , , where f1 is the absolute value of the frequency difference between the detection wave and the echo within the rising edge range, and f2 is the absolute value of the frequency difference between the detection wave and the echo within the falling edge range.

17. The laser radar according to claim 16, wherein the processing unit is configured to: When the number of absolute values ​​f1 of the frequency differences within the rising edge range and / or the number of absolute values ​​f2 of the frequency differences within the falling edge range is greater than 1, it is determined that multiple echoes exist; When multiple echoes exist, echo matching is performed to retain one f1 within the rising edge range and one f2 within the falling edge range.

18. The laser radar according to claim 17, wherein the processing unit is configured to: when multiple echoes exist, perform echo matching in the following manner: determining the resulting frequency shift F based on the movement speed of the device emitting the detection wave; choose The set of f1 and f2 closest to F is selected, and the others are discarded.

Images