CN113156397B

CN113156397B - High-sensitivity laser radar and signal processing method and positioning method thereof

Info

Publication number: CN113156397B
Application number: CN202110711025.2A
Authority: CN
Inventors: 黄保家; 孔德华; 金浩强
Original assignee: Raytheon Plasma Technology Hangzhou Co ltd
Current assignee: Raytheon Plasma Technology Hangzhou Co ltd
Priority date: 2021-06-25
Filing date: 2021-06-25
Publication date: 2021-10-19
Anticipated expiration: 2041-06-25
Also published as: CN113156397A

Abstract

The invention discloses a high-sensitivity laser radar and a signal processing method and a positioning method thereof, a micro photoelectric array is formed by a plurality of unit photoelectric sensors which are mutually connected in parallel, when the laser signal of the scanning environment is reflected from the target and returns to the micro photoelectric array on the laser radar, each unit photoelectric sensor receiving the laser signal performs photoelectric signal conversion, the output signal of each unit photoelectric sensor and the noise signal are superposed, the noise signal has the part with opposite polarity, the part of the noise signal disappears after the superposition through the positive and negative superposition, the signal is strengthened after the superposition of the output signal, the cancellation length can obtain larger signal-to-noise ratio under the condition of low time delay based on the two factors, and signal amplification is carried out by a signal amplifier after the signal-to-noise ratio is improved, so that the laser radar can acquire weak signals. The invention can be used in the fields of active safety technology of intelligent driving, unmanned aerial vehicles, robots and the like which need to apply precise sensors.

Description

High-sensitivity laser radar and signal processing method and positioning method thereof

Technical Field

The invention relates to the technical field of laser radars, in particular to a high-sensitivity laser radar and a signal processing method and a positioning method thereof.

Background

In radar communication and sensor technology, whether a receiving system of equipment can sense external physical information with high sensitivity is often crucial, and since various noises which do not depend on external signals exist in a sensor, when signals received by the receiving system are weak, the noises often cover the detected signals (namely, the signal-to-noise ratio is smaller than the threshold value of the receiving system), so that the detection work of the system is disabled. This is particularly true in rainy or snowy foggy days, long distances, and small or poorly reflective targets. This problem is an obstacle that unmanned driving and even safe driving assistance systems must overcome.

In the prior art, there are techniques such as phase detection and synchronous detection, which mainly use the relationship presented by front and back signals to accumulate the same signal or judge according to the correlation between data, so as to obtain a higher signal-to-noise ratio. Taking a CCD (Charge Coupled Device) Device as an example, a TDI-CCD (time delay integration Device) adopting an area array is applied to low-light high-speed imaging, and when the TDI-CCD is structurally viewed as a CCD Device of a rectangular area array, an imaging area of the TDI-CCD can be viewed as being composed of a column of vertical CCD registers, the TDI Device is generally used for long-line push scan, a target image is sequentially scanned over TDI pixels of each stage, a first stage pixel collects signal charges in a first exposure integration period, the signal charges are not directly output but transferred to a second stage pixel, in a second integration period, the second stage pixel exposes the same target on the basis of the signal charges transferred from a higher stage and collects the signal charges, and then transfers the signal charges to a third stage pixel, and so on, the signal charges collected by the last row (N rows) of pixels and the signal charges collected by the first N-1 are accumulated and transferred to an output register and output, so that the charges in the TDI direction are transferred to a serial shift mode, each stage of pixel transfers out the charges and also receives the signal charges transferred in the preceding stage, and exposes the next target in the next integration period, so that each time one integration period passes, the TDI-CCD outputs a line of video signals. The TDI-CCD can improve the signal-to-noise ratio by increasing the integration time, the TDI device is generally used for long-line push-broom, and the time delay of TDI and the optical-mechanical push-broom are strictly required to be synchronous when the TDI-CCD is used, so that the integration of TDI is ensured to be the accumulation of photo-generated charges of the same target at different moments. However, in practical applications, these delay times are not allowed, for example, in laser radar, which may cause accidents instantly.

Along with the expansion of the intelligent internet of things technology, laser radars are also applied to unmanned equipment and robots more, and compared with the application of the GPS positioning and navigation technology to the unmanned equipment and the robots, the positioning error of the GPS positioning and navigation technology is larger, so that the unmanned equipment and the robots cannot accurately reach specified target points, and the laser radars have better technical advantages in places with smaller range or complex surrounding environment.

Disclosure of Invention

Technical problem to be solved by the invention

The technical problem of how to improve the signal-to-noise ratio under the condition of low time delay and how to realize accurate positioning by utilizing the laser radar under the condition of inaccurate GPS positioning is solved.

Technical scheme

In order to solve the problems, the technical scheme provided by the invention is as follows:

a signal processing method of a high-sensitivity laser radar comprises the following steps

S30, a photo sensor module receives an externally reflected laser signal, and a micro photo array arranged in m rows by n columns is formed on the photo sensor module, wherein the step S30 includes a step S301, in which the micro photo array receives the externally reflected laser signal, the micro photo array includes m by n unit photo sensors connected in parallel, and output terminals of the unit photo sensors are collected on the same load resistor; s302, outputting current signals by the unit photoelectric sensors reflected by the laser and converging the current signals to a load resistor, so that the load resistor passes through superposed output signals of the current signals output by the unit photoelectric sensors reflected by the laser and superposed noise signals output by the unit photoelectric sensors; and S303, the noise signals on the unit photoelectric sensors have positive and negative parts with opposite polarities, the noise signals are overlapped and then a part of the noise signals are offset through positive and negative overlapping, the output signals are overlapped and then the signals are strengthened, and the signal-to-noise ratio of the output end of the load resistor is improved along with the increase of the number of the unit photoelectric sensors subjected to laser reflection.

The present invention is further configured to further include a step S40, where the signal at the output terminal of the load resistor is input to a signal amplifier, and the signal amplified by the signal amplifier is input to the controller.

The invention is further arranged to further include a step S10, in which the controller sends a control signal to the laser transmitter, and the laser transmitter receives the control signal from the controller and transmits a laser beam to the surrounding environment; in step S20, the laser light emitted to the surrounding object is reflected to the photoelectric sensor module.

A high-sensitivity laser radar adopts the signal processing method and comprises a laser transmitter, a photoelectric sensor module and a controller, wherein the laser transmitter is electrically connected with the controller, and the laser transmitter receives a control signal of the controller to emit a light beam to the surrounding environment; the photoelectric sensor module comprises a plurality of unit photoelectric sensors which are connected in parallel and form an array, and the output ends of the unit photoelectric sensors are gathered on the same load resistor.

The invention is further provided that the load resistor is electrically connected with the input end of the signal amplifier, the signal amplifier combines and amplifies the output signals of the photoelectric sensors of each unit and outputs the amplified signals to the input end of the controller.

The invention further provides a shell, the controller and the laser emitter are both positioned in the shell, and the unit photoelectric sensors on the photoelectric sensor module are arranged on the periphery of the shell in a surrounding manner.

A positioning method of a high-sensitivity laser radar is based on the high-sensitivity laser radar and also comprises the following steps,

s50, presetting a marker to form a closed area, acquiring first acquisition data of the laser radar at a first acquisition point by using the controller, performing global modeling by using the first acquisition point as a base point, and converting the first acquisition data into corresponding first coordinate axis information; s60, comparing the closed area with the first coordinate axis information to judge whether the first acquisition data meet the preset requirement; if the first coordinate axis information meets the preset requirement, executing step S80; if the first coordinate axis information does not meet the preset requirement, executing step S70; s70, controlling the laser radar to move to the area where the preset marker without the acquired coordinate axis signal is located according to the acquired coordinate axis information within the preset acquisition times x, acquiring the surrounding environment when the laser radar reaches the next acquisition point and acquiring the next coordinate axis information, and integrating the acquired coordinate axis information until the superposition of the acquired coordinate axis information meets the preset requirement; after the preset acquisition times x are reached, if the obtained coordinate axis information still cannot be superposed with the preset requirements, giving up positioning acquisition; and S80, completing regional positioning collection, storing all collected coordinate axis information, constructing complete global coordinate axis information, forming communication connection between the laser radar and the cloud server, storing the global coordinate axis information of the laser radar by the cloud server, connecting the mobile equipment terminal and the cloud server, receiving information feedback from the cloud server, sending an instruction to the cloud server, and performing operation management on the laser radar.

Advantageous effects

Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:

(1) a plurality of unit photoelectric sensors which are connected in parallel with each other form a micro photoelectric array, when a laser signal of a scanning environment returns to the micro photoelectric array on a laser radar after being reflected by a target object, each unit photoelectric sensor which receives the laser signal carries out photoelectric signal conversion, an output signal and a noise signal of each unit photoelectric sensor are superposed, the noise signal has a part with opposite polarity, a part of the noise signal disappears after being superposed through positive and negative superposition, the signal is strengthened after the output signal is superposed, the elimination is long, a larger signal-to-noise ratio can be obtained under the condition of low delay based on the two factors, the obtaining mode of the high signal-to-noise ratio is different from the working mode of a CCD device of an area array, the photoelectric sensor module does not need to improve the signal-to-noise ratio through time delay integration and has ultrahigh cost performance, meanwhile, the technical scheme can be used in the occasions where the technical scheme is not suitable, such as the occasions requiring faster response time: the unmanned driving of the Internet of things and other fields.

(2) The photoelectric sensor of the unit which receives the laser reflection signal outputs a current signal and converges the current signal on the load resistor, the load resistor obtains larger superposition power, the signal-to-noise ratio is improved, and then the signal amplifier amplifies the signal, so that the laser radar can acquire a weaker signal, and the laser radar is particularly remarkable in rainy and snowy foggy days, long-distance and small targets or targets with poor reflection performance.

(3) The signal processing method based on the laser radar can be applied to area positioning detection with high precision, coordinate axis information detected by the laser radar is matched with a closed area formed by preset markers, and accurate positioning of an area environment can be achieved.

Drawings

Fig. 1 is a schematic flow chart of step S30 in the signal processing method of the high-sensitivity lidar according to the embodiment of the invention.

Fig. 2 is a schematic flow chart of a signal processing method of a high-sensitivity lidar according to an embodiment of the present invention.

Fig. 3 is a schematic flow chart of a positioning method of a high-sensitivity lidar according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of signal transmission when the high-sensitivity lidar according to the embodiment of the invention is applied.

Fig. 5 is a schematic diagram of a circuit for connecting the photo sensor module and the signal amplifier according to the embodiment of the invention.

Detailed Description

For a further understanding of the present invention, reference will now be made in detail to the embodiments illustrated in the drawings.

The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings. The terms first, second, and the like in the present invention are provided for convenience of describing the technical solution of the present invention, and have no specific limiting effect, but are all generic terms, and do not limit the technical solution of the present invention. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art. The technical solutions in the same embodiment and the technical solutions in different embodiments can be arranged and combined to form a new technical solution without contradiction or conflict, and the technical solutions are within the scope of the present invention.

Example 1

With reference to fig. 1, 2 and 4, the technical solution of the present invention is a signal processing method for a high-sensitivity lidar, including the following steps,

s10, the controller sends a control signal to the laser emitter, and the laser emitter receives the control signal from the controller and emits a laser beam to the surrounding environment;

s20, reflecting the laser emitted to the surrounding environment target object to the photoelectric sensor module;

s30, the photoelectric sensor module receives the laser signal reflected from the outside, and improves the signal-to-noise ratio of the output end, the photoelectric sensor module forms a micro photoelectric array arranged according to m rows by n columns, the step S30 includes the following steps,

s301, the micro photoelectric array receives an externally reflected laser signal, the micro photoelectric array comprises m × n unit photoelectric sensors which are connected in parallel, and output ends of the unit photoelectric sensors are collected on the same load resistor;

s302, outputting current signals by the unit photoelectric sensors reflected by the laser and converging the current signals to a load resistor, so that the load resistor passes through superposed output signals of the current signals output by the unit photoelectric sensors reflected by the laser and superposed noise signals output by the unit photoelectric sensors;

s303, noise signals on the unit photoelectric sensors have positive and negative opposite polarity parts, part of the noise signals are offset by positive and negative superposition after the noise signals are superposed, signals are strengthened after the output signals are superposed, and the signal-to-noise ratio of the output end of the load resistor is improved along with the increase of the number of the unit photoelectric sensors subjected to laser reflection;

and S40, inputting the signal of the output end of the load resistor to a signal amplifier, and inputting the signal amplified by the signal amplifier to a controller.

The following analysis demonstrates the working principle of the parallel output micro-photovoltaic array to improve the signal-to-noise ratio:

setting: p (S) represents the total output signal power of the parallel micro photoelectric array;

P₀(S) represents the output signal power of the unit photosensor;

m represents the number of unit photoelectric sensors receiving laser reflection signals in the micro photoelectric array;

p (N) represents the total noise power of the parallel micro photoelectric arrays;

P₀(N) represents the output noise power of the unit photosensor;

lambda is the signal-to-noise ratio of the receiving circuit, and the receiving circuit refers to the parameters of the parallel micro photoelectric array formed by the multiple unit photoelectric sensors;

λ₀is the signal-to-noise ratio of a receiving circuit constructed by a unit photoelectric sensor.

The noise is in the form of a plurality of noise sources, namely:

due to the fact that

Comprises a positive part and a negative part,

remarking: in the circuit of the communication technology,

P⁺(N) represents the sum of the positive polarity partial powers in the noise; p^-(N) represents the sum of the negative polarity portion power in the noise.

The practical influence of the parallel-connection summary output micro photoelectric array constructed by a plurality of unit photoelectric sensors on noise power superposition in the technical scheme is analogized from the convergence effect of expanded sample space of coin throwing data analysis on the deviation degree.

The experimental data in the table below are from ancestry published by Beijing university Press and engineering mathematics, compiled by Kuang Cedar.

Notation in the table: the difference in the number of throws causes the difference in the front-back ratio from the median, i.e., 0.5, and the larger the number of throws, the smaller the deviation. We define the deviation σ as the ratio of the probability that each batch of money is face up relative to the deviation of 0.5 to 0.5. I.e., σ = (probability of the batch throwing face up-median 0.5)/median 0.5.

Analyzing the convergence effect of sample space expansion on the deviation degree according to the thrown coin data, wherein the sample space expansion has a normal distribution rule, and after the noise signals of the unit photoelectric sensors with opposite polarities obtained by the method are superposed, the ratio of the total noise power of the parallel miniature photoelectric arrays to the output noise power of the unit photoelectric sensors conforms to the theoretical relationship, so that the coin can be obtained

。

And the current signals of all the unit photoelectric sensors are superposed, so that the current signal output by the micro photoelectric array is M times of the current signal output by the unit photoelectric sensor, and the following results can be obtained:

in summary, the signal-to-noise ratio λ of the parallel micro-photoelectric array constructed by the plurality of unit photosensors and the signal-to-noise ratio λ of the receiving circuit constructed by the unit photosensors₀The following coefficient relationship exists:

therefore, compared with the signal-to-noise ratio of a receiving circuit constructed by a single unit photoelectric sensor, the improvement multiple of the signal-to-noise ratio of the parallel micro photoelectric array has the following relationship with the number M of the unit photoelectric sensors, as shown in the following table,

M	16	100	225	625	900
						factor of improvement of signal to noise ratio	1.6*10⁴	10⁷	1.7*10⁸	6*10⁹	2.2*10¹⁰

For example, assuming that a signal detected by a receiving system constituted by a single-cell photosensor is 0.001PW and system internal noise is 1PW, a signal-to-noise ratio processed by the single-cell photosensor is 0.001; if a homogeneous isomorphic micro-photovoltaic array constructed with 16 unit photosensors is used, the signal-to-noise ratio λ will become 0.001 × 16000= 16.

It can be seen that the detection system constructed by the technology can be far away from the interference of general thermal noise (thermal noise). Of course, other noises, such as burst noise (boost noise) whose amplitude can be very strong, are distributed sparsely, do not follow normal distribution law, and can cause interference, but because the probability of its existence with signal is very low, it is not easy to interfere with receiving system, and all communication system and sensing equipment using this technology, after the signal-to-noise ratio is solved, if the output of sensor is not large enough, the electric signal can be amplified by increasing the performance of analog amplifier.

Example 2

With reference to fig. 4 and 5, the technical scheme of the invention is that a high-sensitivity laser radar adopting the signal processing method of the embodiment 1 comprises a laser transmitter 2, a photoelectric sensor module 3, a controller 1, a signal amplifier 4 and a shell, wherein the laser transmitter 2 is electrically connected with the controller 1, and the laser transmitter 2 receives a control signal of the controller 1 and emits a light beam to the surrounding environment; the light beam irradiates a target object in the surrounding environment and then is reflected to the photoelectric sensor module 3; the photoelectric sensor module 3 comprises a plurality of unit photoelectric sensors 31 which are connected in parallel and arranged in an array, and the output ends of the unit photoelectric sensors 31 are gathered on the same load resistor 32; the load resistor 32 is electrically connected with the input end of the signal amplifier 4, the signal amplifier 4 amplifies the output signals of each unit photoelectric sensor 31 after combining, the output amplified signals are transmitted to the input end of the controller 1, the controller 1 and the laser emitter 2 are both positioned in the shell, and the unit photoelectric sensors 31 on the photoelectric sensor module 3 are arranged on the periphery of the shell in a surrounding mode.

Example 3

With reference to fig. 1-3, the technical solution of the present invention is a positioning method based on the high-sensitivity lidar of embodiment 2, further comprising the following steps,

s50, presetting a marker to form a closed area, acquiring first acquisition data of the laser radar at a first acquisition point by using the controller, performing global modeling by using the first acquisition point as a base point, and converting the first acquisition data into corresponding first coordinate axis information;

s60, comparing the closed area with the first coordinate axis information to judge whether the first acquisition data meet the preset requirement; if the first coordinate axis information meets the preset requirement, executing step S80; if the first coordinate axis information does not meet the preset requirement, executing step S70;

s70, controlling the laser radar to move to the area where the preset marker without the acquired coordinate axis signal is located according to the acquired coordinate axis information within the preset acquisition times x, acquiring the surrounding environment when the laser radar reaches the next acquisition point and acquiring the next coordinate axis information, and integrating the acquired coordinate axis information until the superposition of the acquired coordinate axis information meets the preset requirement; after the preset acquisition times x are reached, if the obtained coordinate axis information still cannot be superposed with the preset requirements, giving up positioning acquisition;

and S80, completing regional positioning collection, storing all collected coordinate axis information, constructing complete global coordinate axis information, forming communication connection between the laser radar and the cloud server, storing the global coordinate axis information of the laser radar by the cloud server, connecting the mobile equipment terminal and the cloud server, receiving information feedback from the cloud server, sending an instruction to the cloud server, and performing operation management on the laser radar.

The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention. The invention can be used in the fields of active safety technology of intelligent driving, unmanned aircrafts, robots and the like which need to apply precise sensors.

Claims

1. A signal processing method of a high-sensitivity laser radar is characterized by comprising the following steps: s10, the controller sends a control signal to the laser emitter, and the laser emitter receives the control signal from the controller and emits a laser beam to the surrounding environment;

s30, receiving laser signals reflected from the outside by the photoelectric sensor module, forming a micro photoelectric array arranged in m rows by n columns on the photoelectric sensor module,

the step S30 includes the steps of,

s301, the micro photoelectric array receives an externally reflected laser signal, the micro photoelectric array comprises m × n unit photoelectric sensors which are connected in parallel, the homogeneous isomorphic micro photoelectric array is constructed by the m × n unit photoelectric sensors, and output ends of the unit photoelectric sensors are gathered on the same load resistor;

s303, the noise signals on the unit photoelectric sensors have positive and negative parts with opposite polarities, after the noise signals are superposed, partial noise signals are offset through positive and negative superposition, the superposed output signals are strengthened, and the signal-to-noise ratio of the output end of the load resistor is improved along with the increase of the number of the unit photoelectric sensors subjected to laser reflection;

setting: p (S) represents the total output signal power of the parallel micro photoelectric arrays;

P₀(S) represents the output signal power of the unit photosensor;

P₀(N) represents the output noise power of the unit photosensor;

lambda is the signal-to-noise ratio of the micro photoelectric array receiving circuit, and the micro photoelectric array receiving circuit is constructed by a plurality of unit photoelectric sensors which are connected in parallel;

λ₀the signal-to-noise ratio of a receiving circuit constructed by a unit photoelectric sensor;

p (N) and P₀The relationship between the ratio of (N) and the number M of unit photosensors is as follows (1)

P (S) and P₀The relationship between the ratio of (S) and the number M of unit photosensors is as follows (2)

Lambda and lambda₀The relationship between the ratio of (A) and the number M of unit photosensors is as follows (3)

The ratio of the signal-to-noise ratio of the receiving circuit of the parallel micro photoelectric array constructed by a plurality of unit photoelectric sensors to the signal-to-noise ratio of the receiving circuit constructed by one unit photoelectric sensor is M^3.5。

2. The signal processing method of the high-sensitivity lidar according to claim 1, further comprising:

3. A high-sensitivity laser radar, characterized in that, the signal processing method of any one of claims 1-2 is adopted, and the high-sensitivity laser radar comprises a laser transmitter, a photoelectric sensor module and a controller, wherein the laser transmitter is electrically connected with the controller, and the laser transmitter receives a control signal of the controller to emit a light beam to the surrounding environment;

the photoelectric sensor module comprises a plurality of unit photoelectric sensors which are connected in parallel and arranged in an array mode, and the output ends of the unit photoelectric sensors are gathered on the same load resistor.

4. The lidar of claim 3, wherein the load resistor is electrically connected to an input of a signal amplifier, and the signal amplifier amplifies an output signal of the load resistor and outputs the amplified signal to an input of the controller.

5. The lidar of claim 4, further comprising a housing, wherein the controller and the laser transmitter are located inside the housing, and the unit photosensors on the photosensor module are arranged around the outer periphery of the housing.

6. A method for positioning a high-sensitivity lidar according to any of claims 3 to 5, further comprising the step of,