CN112363145A - Vehicle-mounted laser radar temperature compensation system and method - Google Patents
Vehicle-mounted laser radar temperature compensation system and method Download PDFInfo
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract
The invention discloses a vehicle-mounted laser radar temperature compensation system, which collects distances measured by a laser radar at different test temperatures, constructs a distance temperature change curve relation, generates a function relation between compensation time and temperature, acquires the current temperature of the laser radar when the next frame depth image of the laser radar is exposed, calculates the compensation time corresponding to the current temperature, adds the compensation time to a shutter signal of the laser radar, completes the time domain compensation of the laser radar, corrects the brightness change of a gray scale image caused by the change of the laser radar along with the temperature, collects the distances measured by the laser radar at each test temperature on the basis of the time domain compensation, performs cubic spline interpolation, generates a spline interpolation table of the distance along with the change of the temperature, and establishes a corresponding relation between the temperature and the compensation distance; and searching the corresponding compensation distance according to the current temperature of the laser radar, and increasing the compensation distance for the depth image of the next frame to ensure that the distance compensation precision is high in both the linear region and the nonlinear region of the electronic device.
Description
Technical Field
The invention relates to the technical field of vehicle-mounted laser radars, in particular to a temperature compensation system and method for a vehicle-mounted laser radar.
Background
Lidar, as a representative of 3D vision devices, has been widely used in our lives, such as face-brushing payment, face-brushing unlocking, and the like. In the field of vehicle-mounted, such as unmanned driving, blind cleaning, face brushing and entering, in-vehicle behavior identification and the like, the laser radar is also increasingly applied. The laser radar detects the gray scale proportion relation of two adjacent groups of reflected laser signals to measure the distance. The laser signal of laser radar and the shutter signal of laser radar are sensitive to temperature, and along with temperature change, the phases of the laser signal and the shutter signal can also change along with the change of temperature, so that ranging deviation is caused.
In the prior art, feedback adjustment is generally performed by increasing a temperature compensation coefficient, and the scheme is simple and convenient, but is only suitable for scenes with narrow working temperature range and better device linearity. However, in the field of vehicle-mounted devices, the working temperature range is large, most electronic components enter a nonlinear region, and the distance measurement accuracy is rapidly deteriorated. In addition, the positions of the laser signal and the shutter signal in the time domain are also changed due to temperature change, so that the gray value of a gray scale image output by the laser radar is also changed violently, and is too dark or exposed, and the recognition accuracy of a face brushing payment or a face brushing unlocking scene is influenced.
Disclosure of Invention
Based on the above, the invention aims to provide a temperature compensation system and method for a vehicle-mounted laser radar, which can accurately compensate temperature changes in a linear region and a nonlinear region of an electronic device and can eliminate the severe brightness change of a laser radar output gray scale image caused by large temperature change.
In order to achieve the above object, the present invention provides a temperature compensation system for a vehicle-mounted laser radar, the system comprising:
the first acquisition module is used for acquiring the distances measured by the laser radar at different test temperatures to form a first group of data of which the distances change along with the temperature;
the temperature compensation time relation module is used for constructing a distance temperature change curve relation according to the first group of data and generating a function relation between compensation time and temperature according to the light speed and distance relation;
the time domain compensation module is used for acquiring the current temperature of the laser radar when the next frame of depth image of the laser radar is exposed, calculating the compensation time corresponding to the current temperature, increasing the compensation time for the shutter signal of the laser radar and completing the time domain compensation of the laser radar;
the second acquisition module is used for carrying out corresponding time domain compensation on the laser radar at each test temperature and acquiring the distance measured by the laser radar at each test temperature to form a second group of data of which the distance changes along with the temperature;
the temperature compensation distance relation module is used for carrying out cubic spline interpolation on the second group of data, generating a spline interpolation table with the distance changing along with the temperature and establishing the corresponding relation between the temperature and the compensation distance;
and the distance compensation module is used for searching the corresponding compensation distance in the spline interpolation table according to the current temperature of the laser radar and increasing the compensation distance for the next frame of depth image.
Preferably, the temperature compensation time relation module is specifically configured to:
the constructed distance temperature change curve equation is shown as formula (1):
y＝7E-05x3-0.0123x2-6.1153x+792.59 (1)；
wherein y is the distance and x is the temperature;
setting the initial point temperature of the laser radar in the calibration as T0, and substituting the initial point temperature into formula (1) to obtain corresponding y 0;
the equation of the curve of the compensation distance Δ y with the change of the temperature x is formula (2):
Δy＝7E-05x3-0.0123x2-6.1153x+(792.59-y0) (2)。
preferably, the temperature compensation time relation module is further specifically configured to:
according to a light speed distance formula s-0.5C- Δ t, wherein Δ t is the sum of laser emission and return time of the laser radar, and a functional relation equation of compensation time Δ t and temperature x is obtained;
Δt＝[7E-05x3-0.0123x2-6.1153x+(792.59-y0)]/599.584916 (3)。
preferably, the system further comprises a temperature sensor, wherein the temperature sensor collects the current temperature of the laser radar and sends the current temperature to the time domain compensation module and the distance compensation module.
Preferably, the system further comprises an image processing module, wherein the image processing module comprises a shutter signal trigger position register;
the time domain compensation module calculates compensation time according to the acquired current temperature of the laser radar by using a formula (3), and sends the compensation time to the image processing module;
and the image processing module writes the compensation time into the shutter signal trigger position register, updates the compensation time into a new trigger signal, and drives the shutter signal by using the new trigger signal when the next frame of depth image of the laser radar is exposed, so as to complete the time domain compensation of the laser signal and the shutter signal of the laser radar.
Preferably, the temperature compensation distance relation module is specifically configured to:
using cubic spline interpolation to generate a spline interpolation table according to the discrete data of the acquired distance changing along with the temperature, wherein the interpolation function is,
res＝interp1(x,y,xq,'spline') (4)；
wherein x is the collected temperature data, y is the distance of the corresponding temperature point, and xq is the interpolation interval.
Preferably, the distance compensation module is specifically configured to:
reading the current temperature of the laser radar through a temperature sensor, and inquiring a compensation distance or a critical compensation distance corresponding to the current temperature in a spline interpolation table according to the current temperature;
setting the initial point temperature when the laser radar is calibrated, correspondingly setting the initial value of the compensation distance in the spline interpolation table, and adding the final compensation distance or the critical compensation distance to the next frame depth image by subtracting the initial value of the compensation distance from the final compensation distance or the critical compensation distance.
Preferably, the system further comprises:
the threshold module is used for setting a temperature change threshold and a time change threshold for collecting temperature;
the timing module is used for counting the time interval of temperature acquisition;
and the judging module is used for acquiring the current temperature of the laser radar if the time interval is greater than the time change threshold, judging whether the difference between the current temperature and the temperature acquired last time is greater than the temperature change threshold, and executing the time domain compensation module or the distance compensation module if the difference is greater than the temperature change threshold.
In order to achieve the above object, the present invention provides a temperature compensation method for a vehicle-mounted laser radar, wherein the method comprises:
collecting distances measured by a laser radar at different test temperatures to form a first group of data of which the distances change along with the temperature;
constructing a distance-temperature change curve relation according to the first group of data, and generating a function relation of compensation time and temperature according to the light speed and distance relation;
when the next frame of depth image of the laser radar is exposed, acquiring the current temperature of the laser radar, calculating the compensation time corresponding to the current temperature, and increasing the compensation time for the shutter signal of the laser radar to complete the time domain compensation of the laser radar;
correspondingly performing time domain compensation on the laser radar at each test temperature, and collecting the distance measured by the laser radar at each test temperature to form a second group of data of which the distance changes along with the temperature;
carrying out cubic spline interpolation on the second group of data to generate a spline interpolation table with the distance changing along with the temperature, and establishing a corresponding relation between the temperature and the compensation distance;
and searching a corresponding compensation distance in the spline interpolation table according to the current temperature of the laser radar, and increasing the compensation distance for the next frame of depth image.
Preferably, the method further comprises:
setting a temperature change threshold and a time change threshold for collecting temperature;
counting the time interval of the acquisition temperature;
and if the time interval is greater than the time change threshold, acquiring the current temperature of the laser radar, judging whether the difference between the current temperature and the temperature acquired last time is greater than the temperature change threshold, and if so, executing the time domain compensation step or the distance compensation step.
Compared with the prior art, the vehicle-mounted laser radar temperature compensation system and the method thereof have the beneficial effects that: the gray level image brightness difference caused by temperature change can be fundamentally solved, and the accuracy rate based on the gray level image recognition algorithm is improved; the temperature range of the whole vehicle-mounted laser radar is adapted, and through two-stage adjustment of time domain position adjustment and distance fine adjustment, the measurement accuracy is higher in both a linear region and a nonlinear region of an electronic device, and the millimeter-level wide temperature range distance measurement accuracy is achieved; the embedded calling algorithm is exquisite, the dependence on the system computing power is low, and too much system computing power is not occupied in the using process.
Drawings
FIG. 1 is a system diagram of a vehicle lidar temperature compensation system according to one embodiment of the invention.
Fig. 2 is a graph of distance versus temperature according to an embodiment of the present invention.
FIG. 3 is a graph illustrating the variation of compensation time with temperature according to an embodiment of the present invention.
FIG. 4 is a graphical illustration of distance versus temperature according to an embodiment of the present invention.
Fig. 5 is a cubic spline interpolation curve according to an embodiment of the present invention.
FIG. 6 is a graph of distance versus temperature after time domain compensation, according to an embodiment of the present invention.
Fig. 7 is a flowchart of a method for vehicle-mounted lidar temperature compensation according to one embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to the specific embodiments shown in the drawings, which are not intended to limit the present invention, and structural, methodological, or functional changes made by those skilled in the art according to the specific embodiments are included in the scope of the present invention.
In an embodiment of the present invention shown in fig. 1, the present invention provides a vehicle-mounted lidar temperature compensation system, including:
the first acquisition module 10 is used for acquiring the distances measured by the laser radar at different test temperatures to form a first group of data of which the distances change along with the temperature;
the temperature compensation time relation module 11 is configured to construct a distance-temperature change curve relation according to the first group of data, and generate a function relation between compensation time and temperature according to the light speed and distance relation;
the time domain compensation module 12 is configured to obtain a current temperature of the laser radar when a next frame depth image of the laser radar is exposed, calculate a compensation time corresponding to the current temperature, increase the compensation time for a shutter signal of the laser radar, and complete time domain compensation of the laser radar;
the second acquisition module 13 is configured to perform corresponding time domain compensation on the laser radar at each test temperature, and acquire a distance measured by the laser radar at each test temperature to form a second set of data in which the distance changes with temperature;
the temperature compensation distance relation module 14 is configured to perform cubic spline interpolation on the second set of data, generate a spline interpolation table in which a distance changes with temperature, and establish a corresponding relation between temperature and a compensation distance;
and the distance compensation module 15 is configured to search a corresponding compensation distance in the spline interpolation table according to the current temperature of the laser radar, and add the compensation distance to the depth image of the next frame.
The laser radar detects the gray scale proportion relation of two adjacent groups of reflected laser signals to measure the distance, and the gray scale proportion and distance relation is set before leaving a factory and is obtained by calibration. Under different temperatures, due to the characteristics of electronic devices, the relative delay of a laser signal of a laser radar and a shutter signal in a time domain is different, so that under the same actual distance, firstly, a sensor CMOS of the laser radar obtains different gray values, the gray values are integral values of the shutter signal and the reflected laser signal, a gray scale image output by the laser radar is a 2D image, the gray values represent brightness of the gray scale image, face recognition is usually performed through the gray scale image, and the position change of the laser signal and the shutter signal in the time domain can be caused by the temperature change of the devices, so that the sensor of the laser radar obtains the gray scale images with different brightness. Secondly, different measurement distances, i.e. measurement deviations, are generated. According to the invention, time compensation is carried out on the laser signal and the shutter signal of the laser radar in the time domain when the temperature changes, distance compensation is carried out on the obtained depth image, and through two-stage adjustment of time domain position adjustment and distance fine adjustment, the brightness change of the gray-scale image caused by the temperature change is solved, the algorithm accuracy based on the gray-scale image face recognition is improved, and the distance measurement precision of the output depth image is increased.
The first acquisition module acquires distances measured by the laser radar at different test temperatures to form data of the distance changing along with the temperature. And placing the laser radar and the test white board into a high-low temperature box, and fixing the positions of the laser radar and the test white board. And after the laser radar works normally, recording the distance between the temperature and the test white board. The temperature of the high and low temperature boxes is set from-40 to 85 degrees, and the temperature is increased by every 10 degrees. The initial ambient temperature during the calibration of the laser radar is the initial point temperature of the laser radar, for example, the ambient temperature is 25 degrees, the temperature of the laser radar is 10 degrees, and then the initial point temperature of the laser radar is 35 degrees. The range of the lidar measurements at various temperatures from-30 degrees to 95 degrees was therefore collected.
And the temperature compensation time relation module constructs a distance temperature change curve according to the data of the distance changing along with the temperature, and generates a function relation between the temperature and the compensation time according to the relation between the light speed and the distance. Specifically, the collected data of the distance changing with the temperature is imported into data processing software, and a curve of the distance changing with the temperature is constructed, such as a trend graph of the distance changing with the temperature shown in fig. 2. The constructed distance temperature change curve equation is shown as formula (1):
y＝7E-05x3-0.0123x2-6.1153x+792.59 (1)；
where y is the distance, x is the temperature, and y is in mm. The lidar temperature compensation compensates for the effects of temperature variations, and therefore requires subtraction of the initial values of the lidar calibration times. Setting the initial point temperature of the laser radar calibration as T0, and substituting the formula (1) to obtain the corresponding y 0. The curve equation of the variation of the compensation distance along with the temperature is shown as the formula (2):
Δy＝7E-05x3-0.0123x2-6.1153x+(792.59-y0) (2)；
for example, the initial point temperature during the calibration of the laser radar is 35 degrees, and in formula (1), y0 is 566.4882, so that the curve equation of the compensation distance changing with the temperature is as follows:
Δy＝7E-05x3-0.0123x2-6.1153x+226.1018；
according to the light speed distance formula s is 0.5C Δ t, wherein Δ t is the sum of the laser emission time and the laser return time of the laser radar, a function relation equation of the compensation time Δ t and the temperature x is obtained:
Δt＝[7E-05x3-0.0123x2-6.1153x+(792.59-y0)]/599.584916 (3)；
Δ t is given in seconds and x is given in ℃. According to the function relation equation of the compensation time and the temperature of the laser radar, the corresponding compensation time can be obtained. As shown in fig. 3, the compensation time is plotted as a function of temperature.
And the time domain compensation module acquires the current temperature of the laser radar when the next frame of depth image of the laser radar is exposed, calculates the compensation time corresponding to the current temperature, and increases the compensation time for the shutter signal of the laser radar. The system further comprises a temperature sensor, wherein the temperature sensor collects the current temperature of the laser radar and sends the current temperature to the time domain compensation module and the distance compensation module. The temperature sensor adopts an IIC interface. And the time domain compensation module reads the current temperature value of the laser radar through the IIC interface. The system further comprises an image processing module, wherein the image processing module comprises a shutter signal trigger position register, the time domain compensation module obtains compensation time through calculation of formula (3) according to the obtained current temperature of the laser radar, the compensation time is sent to the image processing module, the image processing module writes the compensation time into the shutter signal trigger position register and updates the compensation time into a new trigger signal, and when the next frame depth image of the laser radar is exposed, the new trigger signal is used for driving the shutter signal, so that the time domain compensation of the laser signal and the shutter signal of the laser radar is completed. The compensation accuracy is the clock resolution in the time domain. The time domain variation of the laser signal and the shutter signal of the laser radar is compensated through the compensation time, and the influence of the temperature variation on the laser radar in the time domain is fundamentally solved. However, the time-domain variation of the laser signal and the shutter signal is compensated by the compensation time, and only coarse adjustment can be performed under the influence of the resolution of the system driving signal in the time domain, that is, the brightness variation of a gray scale image output by the laser radar caused by temperature variation is solved and the distance error is controlled within a small range. For example, the period of the external clock 45M of the laser radar system is about 22.22ns, and after the frequency division of the system (1/128), the minimum period is about 173.6ps, and the corresponding ranging accuracy is 26mm (s-c t/2). The pulse width of the laser signal and the shutter signal of the laser radar system is 22ns, and the compensation minimum period accounts for about 0.79% of the pulse width.
From the above, it can be seen that distance and temperature need to be finely adjusted on the basis of time domain compensation of the laser signal and the shutter signal, so as to achieve the millimeter-scale wide temperature range ranging accuracy. And the second acquisition module performs corresponding time domain compensation on the laser radar at each test temperature, executes time domain compensation on the laser radar at each test temperature according to the time domain compensation module, and acquires the distance measured by the laser radar at each test temperature, so that the acquired distance data are based on the distance data after time domain compensation, and a second group of data with the distance varying with the temperature is formed. And placing the laser radar and the test white board into a high-low temperature box, and fixing the positions of the laser radar and the test white board. And after the laser radar works normally, recording the distance between the temperature and the test white board. The temperature of the high and low temperature boxes is set from-40 to 85 degrees, and the temperature is increased by every 10 degrees. The initial ambient temperature during the calibration of the laser radar is the initial point temperature of the laser radar, for example, the ambient temperature is 25 degrees, the temperature of the laser radar is 10 degrees, and then the initial point temperature of the laser radar is 35 degrees. The range of the lidar measurements at various temperatures from-30 degrees to 95 degrees was therefore collected. Data collected as a function of temperature as shown in figure 4.
And the temperature compensation distance relation module performs cubic spline interpolation on the data of the distance changing along with the temperature to generate a spline interpolation table of the distance changing along with the temperature, and establishes a corresponding relation between the temperature and the compensation distance. Specifically, cubic spline interpolation is adopted for discrete data of the acquired distance changing along with the temperature to generate a spline interpolation table, and an interpolation function is as follows:
res＝interp1(x,y,xq,'spline') (4)；
where x is the collected temperature data, y is the distance of the corresponding temperature point, and xq is the interpolation interval, as shown in fig. 5, which is a cubic spline interpolation curve generated for the example.
And the distance compensation module searches the corresponding compensation distance in the spline interpolation table according to the current temperature of the laser radar and increases the compensation distance for the next frame of depth image. And reading the current temperature of the laser radar through a temperature sensor, and inquiring a compensation distance or a critical compensation distance corresponding to the current temperature in a spline interpolation table according to the current temperature. Similarly, the temperature compensation compensates for the effect of the temperature change, i.e., the initial value needs to be subtracted. Setting the initial point temperature when the laser radar is calibrated to be T0, and correspondingly setting the initial point temperature to be the compensation distance initial value in the spline interpolation table, wherein the final compensation distance or the critical compensation distance is the compensation distance minus the compensation distance initial value, and adding the final compensation distance or the critical compensation distance to the next frame depth image. And obtaining high-precision depth image data. In addition, the system is suitable for a wide temperature range of a vehicle gauge product, more accurate correction data can be obtained by adopting cubic spline interpolation, the size of an interpolation table can be modified through an interpolation interval, very high distance compensation precision is realized in a linear area and a non-linear area of an electronic device, and the requirements of the system on distance measurement precision and speed are met.
In practical application, in order to reduce the computing resources of the system, the corresponding compensation value is updated only when the temperature changes, and when the temperature does not change, the compensation value calculated when the temperature changes last time is used. In a specific embodiment of the present invention, the system further includes a threshold module, a timing module, and a determination module. The threshold module is used for setting a temperature change threshold and a time change threshold for collecting temperature, the timing module is used for counting a time interval for collecting the temperature, if the time interval is greater than the time change threshold, the judging module obtains the current temperature of the laser radar and judges whether the difference between the current temperature and the last obtained temperature is greater than the temperature change threshold, and if the difference is greater than the temperature change threshold, the time domain compensation module or the distance compensation module is executed for temperature compensation. For example, the compensation accuracy of the distance compensation module is set to 0.5mm, the corresponding temperature change is about 1 degree (based on the collected data, the distance change per degree is about 0.41 mm/deg.c), and the temperature change threshold is set to 0.5 degree because the distance temperature change curve does not change uniformly and a certain margin is reserved. Meanwhile, the IIC bus is relatively seriously occupied because the temperature needs to be queried in real time for temperature compensation. Considering that the temperature cannot change instantaneously, the query is set once per second, so that the temperature compensation base number feedback can be ensured, and the system resources can be saved.
The experimental result proves that the verification is carried out under the same test environment, the laser radar and the test white board are placed in the high-low temperature box, the positions of the laser radar and the test white board are fixed, after the laser radar works normally, the distance between the temperature and the test white board is recorded, the temperature of the warm box is set from-40 ℃ to 85 ℃, the temperature is gradually increased every 5 ℃, the corresponding temperature value and the corresponding distance are collected, the distance of the distance changing along with the temperature is controlled within 5mm according to the test result, and the distance changing along with the temperature is controlled according to the time domain compensation and the temperature compensation curve shown in fig. 6.
In an embodiment of the present invention shown in fig. 7, a method for temperature compensation of a vehicle-mounted laser radar is provided, the method including:
s701, collecting distances measured by a laser radar at different test temperatures to form a first group of data of the distance changing along with the temperature;
s702, constructing a distance and temperature change curve relation according to the first group of data, and generating a function relation of compensation time and temperature according to the light speed and distance relation;
s703, when the next frame of depth image of the laser radar is exposed, acquiring the current temperature of the laser radar, calculating the compensation time corresponding to the current temperature, and increasing the compensation time for the shutter signal of the laser radar to complete the time domain compensation of the laser radar;
s704, performing corresponding time domain compensation on the laser radar at each test temperature, and collecting the distance measured by the laser radar at each test temperature to form a second group of data of which the distance changes along with the temperature;
s705, carrying out cubic spline interpolation on the second group of data to generate a spline interpolation table with the distance changing along with the temperature, and establishing a corresponding relation between the temperature and the compensation distance;
s706, according to the current temperature of the laser radar, searching a corresponding compensation distance in the spline interpolation table, and increasing the compensation distance for the next frame of depth image.
And placing the laser radar and the test white board into a high-low temperature box, and fixing the positions of the laser radar and the test white board. And after the laser radar works normally, recording the distance between the temperature and the test white board. And collecting the distances measured by the laser radar at different test temperatures to form data of the distance changing along with the temperature. And constructing a distance-temperature change curve relation according to the first group of data, and generating a functional relation between the compensation time and the temperature according to the light speed and distance relation. And when the next frame of depth image of the laser radar is exposed, acquiring the current temperature of the laser radar, calculating the compensation time corresponding to the current temperature according to the functional relation, and increasing the compensation time for the shutter signal of the laser radar to complete the time domain compensation of the laser radar. And correspondingly performing time domain compensation on the laser radar at each test temperature, and collecting the distance measured by the laser radar at each test temperature, so that the collected distance data are based on the distance data subjected to time domain compensation to form a second group of data with the distance varying with the temperature. And carrying out cubic spline interpolation on the second group of data to generate a spline interpolation table with the distance changing along with the temperature, establishing a corresponding relation between the temperature and the compensation distance, searching the corresponding compensation distance in the spline interpolation table according to the current temperature of the laser radar, increasing the compensation distance for the next frame of depth image, and finishing the accurate distance compensation for the laser radar.
In a specific embodiment of the present invention, the method further includes: setting a temperature change threshold and a time change threshold for collecting temperature; counting the time interval of the acquisition temperature; and if the time interval is greater than the time change threshold, acquiring the current temperature of the laser radar, judging whether the difference between the current temperature and the temperature acquired last time is greater than the temperature change threshold, and if so, executing the time domain compensation step or the distance compensation step.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (10)
1. A vehicle lidar temperature compensation system, the system comprising:
the first acquisition module is used for acquiring the distances measured by the laser radar at different test temperatures to form a first group of data of which the distances change along with the temperature;
the temperature compensation time relation module is used for constructing a distance temperature change curve relation according to the first group of data and generating a function relation between compensation time and temperature according to the light speed and distance relation;
the time domain compensation module is used for acquiring the current temperature of the laser radar when the next frame of depth image of the laser radar is exposed, calculating the compensation time corresponding to the current temperature, increasing the compensation time for the shutter signal of the laser radar and completing the time domain compensation of the laser radar;
the second acquisition module is used for carrying out corresponding time domain compensation on the laser radar at each test temperature and acquiring the distance measured by the laser radar at each test temperature to form a second group of data of which the distance changes along with the temperature;
the temperature compensation distance relation module is used for carrying out cubic spline interpolation on the second group of data, generating a spline interpolation table with the distance changing along with the temperature and establishing the corresponding relation between the temperature and the compensation distance;
and the distance compensation module is used for searching the corresponding compensation distance in the spline interpolation table according to the current temperature of the laser radar and increasing the compensation distance for the next frame of depth image.
2. The vehicle lidar temperature compensation system of claim 1, wherein the temperature compensation time relationship module is specifically configured to:
the constructed distance temperature change curve equation is shown as formula (1):
y＝7E-05x3-0.0123x2-6.1153x+792.59 (1)；
wherein y is the distance and x is the temperature;
setting the initial point temperature of the laser radar in the calibration as T0, and substituting the initial point temperature into formula (1) to obtain corresponding y 0;
the equation of the curve of the compensation distance Δ y with the change of the temperature x is formula (2):
Δy＝7E-05x3-0.0123x2-6.1153x+(792.59-y0) (2)。
3. the vehicle lidar temperature compensation system of claim 2, wherein the temperature compensation time relationship module is further specifically configured to:
according to the light speed distance formula s is 0.5C Δ t, wherein Δ t is the sum of the laser emission time and the laser return time of the laser radar, the functional relation equation of the compensation time Δ t and the temperature x is obtained as follows:
Δt＝[7E-05x3-0.0123x2-6.1153x+(792.59-y0)]/599.584916 (3)。
4. the vehicle lidar temperature compensation system of claim 3, further comprising a temperature sensor that collects a current temperature of the lidar and transmits the current temperature to the time domain compensation module and the distance compensation module.
5. The vehicle lidar temperature compensation system of claim 4, wherein the system further comprises an image processing module, the image processing module comprising a shutter signal trigger position register,
the time domain compensation module calculates compensation time according to the acquired current temperature of the laser radar by using a formula (3), and sends the compensation time to the image processing module;
and the image processing module writes the compensation time into the shutter signal trigger position register, updates the compensation time into a new trigger signal, and drives the shutter signal by using the new trigger signal when the next frame depth image of the laser radar is exposed, so as to complete the time domain compensation of the laser signal and the shutter signal of the laser radar.
6. The vehicle-mounted lidar temperature compensation system of claim 5, wherein the temperature compensation distance relationship module is specifically configured to:
using cubic spline interpolation to generate a spline interpolation table according to the discrete data of the acquired distance changing along with the temperature, wherein the interpolation function is,
res＝interp1(x,y,xq,'spline') (4)；
wherein x is the collected temperature data, y is the distance of the corresponding temperature point, and xq is the interpolation interval.
7. The vehicle-mounted lidar temperature compensation system of claim 5, wherein the distance compensation module is specifically configured to:
reading the current temperature of the laser radar through a temperature sensor, and inquiring a compensation distance or a critical compensation distance corresponding to the current temperature in a spline interpolation table according to the current temperature;
setting the initial point temperature when the laser radar is calibrated, correspondingly setting the initial value of the compensation distance in the spline interpolation table, and adding the final compensation distance or the critical compensation distance to the next frame depth image by subtracting the initial value of the compensation distance from the final compensation distance or the critical compensation distance.
8. The vehicle lidar temperature compensation system of claim 7, wherein the system further comprises:
the threshold module is used for setting a temperature change threshold and a time change threshold for collecting temperature;
the timing module is used for counting the time interval of temperature acquisition;
and the judging module is used for acquiring the current temperature of the laser radar if the time interval is greater than the time change threshold, judging whether the difference between the current temperature and the temperature acquired last time is greater than the temperature change threshold, and executing the time domain compensation module or the distance compensation module if the difference is greater than the temperature change threshold.
9. A vehicle-mounted laser radar temperature compensation method is characterized by comprising the following steps:
collecting distances measured by a laser radar at different test temperatures to form a first group of data of which the distances change along with the temperature;
constructing a distance-temperature change curve relation according to the first group of data, and generating a function relation of compensation time and temperature according to the light speed and distance relation;
when the next frame of depth image of the laser radar is exposed, acquiring the current temperature of the laser radar, calculating the compensation time corresponding to the current temperature, and increasing the compensation time for the shutter signal of the laser radar to complete the time domain compensation of the laser radar;
correspondingly performing time domain compensation on the laser radar at each test temperature, and collecting the distance measured by the laser radar at each test temperature to form a second group of data of which the distance changes along with the temperature;
carrying out cubic spline interpolation on the second group of data to generate a spline interpolation table with the distance changing along with the temperature, and establishing a corresponding relation between the temperature and the compensation distance;
and searching a corresponding compensation distance in the spline interpolation table according to the current temperature of the laser radar, and increasing the compensation distance for the next frame of depth image.
10. The vehicle lidar temperature compensation method of claim 9, wherein the method further comprises:
setting a temperature change threshold and a time change threshold for collecting temperature;
counting the time interval of the acquisition temperature;
and if the time interval is greater than the time change threshold, acquiring the current temperature of the laser radar, judging whether the difference between the current temperature and the temperature acquired last time is greater than the temperature change threshold, and if so, executing the time domain compensation step or the distance compensation step.
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