CN117192521A - Laser radar code wheel calibration subdivision method, device and computer system - Google Patents
Laser radar code wheel calibration subdivision method, device and computer system Download PDFInfo
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Abstract
The invention discloses a laser radar code wheel calibration subdivision method, which comprises the following steps: laser radar code wheel relative size calibration: recording the interval clock cycle number of each code wheel grating tooth, calculating the ratio of the adjacent grating tooth interval clock cycle number in a circle of time, forming a plurality of arrays by the ratio, performing average value processing, confirming the angle value between two grating teeth, and storing the calibration data into a laser radar; subdividing a laser radar code wheel: calculating the rotation angular velocity of the adjacent grating tooth motor, determining the time interval of triggering laser pulses of the adjacent grating tooth, reading the instant moment of the grating tooth, adjusting the triggering frequency of the laser pulses, obtaining the absolute angle value of each grating tooth, and continuously assigning values to the scanning angle values by combining the rotation angular velocity of the motor until the moment of reading the next grating tooth. The invention also discloses a laser radar code wheel calibration subdivision device and a computer system. The invention effectively improves the precision index of the code disc, solves the angle positioning error of the code disc, avoids the calibration error, and can be widely applied to the field of laser radars.
Description
Technical Field
The present invention relates to lidar technologies, and in particular, to a method, an apparatus, and a computer system for calibrating and subdividing a lidar code wheel.
Background
Laser radars can be classified into three types in their scanning form, namely mechanical rotational scanning, galvanometer scanning, and optical phased arrays. In order to realize angle positioning, a photoelectric encoder is generally adopted to realize measurement and control of a scanning angle. The photoelectric encoder generally comprises a code disc and a code reader, and the code reader comprises a light source and a photoelectric sensor.
Photoelectric encoders are classified into reflective and transmissive types based on the mechanism by which the light source interacts with the code wheel. Photoelectric encoders are classified into incremental encoding and absolute encoding based on the different shapes of the code wheel. In practical implementations of mechanical steer lidar, transmissive delta photoelectric encoding or reflective delta photoelectric encoding is typically employed.
In order to ensure accurate scanning angle, the measured profile has high reduction degree, and the grating/tooth on the incremental code disc is required to have high uniformity, and in the practical application process, the accurate angle positioning of scanning cannot be realized due to insufficient machining precision and installation positioning deviation. The deviations of the marking angle from the true scanning angle can be caused by the non-uniformity of the grating/tooth widths themselves, the non-uniformity of the grating/tooth spacing, and the eccentricity of the overall mounting of the code wheel.
In the existing compact-structure laser radar, the processing limit of the overall dimension of a code wheel and the density of grating/tooth is limited, and on the premise that one grating/tooth cannot correspond to one ranging laser pulse, in order to further improve the angular resolution of radar scanning, a code wheel code division strategy is often adopted, namely a plurality of ranging laser pulses with equal angle intervals are emitted between scanning angles corresponding to adjacent grating/tooth. Therefore, the variable of the rotation speed stability of the motor is introduced, if the rotation speed of the motor is unstable, the adjacent grid/space read by the code reader is unstable in time fluctuation, the uniformity of the corresponding angle of the laser pulse cannot be realized by code disc code division based on a fixed time interval, and the problems of code disc processing and installation positioning deviation are superposed, so that the point cloud image obtained by final scanning ranging is not matched with the outline of a real measured object, and image distortion such as distortion and the like occurs.
In order to overcome the problems, the existing coping strategy is to improve the processing and assembling precision of the code wheel, optimize and control the motor and reduce the instability of the rotating speed. But the problems can not be fundamentally solved, and the method further increases the production cost of the radar, which is not beneficial to mass production.
Disclosure of Invention
The invention aims to overcome the defects of the background technology, and provides a laser radar code wheel calibration subdivision method, a laser radar code wheel calibration subdivision device and a laser radar code wheel calibration subdivision computer system, which can effectively improve the precision index of the code wheel, solve the angle positioning errors caused by the grating tooth processing errors and the installation deviations of the code wheel, and avoid the calibration errors caused by unstable motor revolution in the calibration link.
The invention provides a laser radar code wheel calibration subdivision method, which comprises two parts of laser radar code wheel relative size calibration and laser radar code wheel subdivision, and comprises the following specific contents: s1, calibrating the relative size of a laser radar code disc: the controller of the laser radar records the interval clock cycle number corresponding to each code wheel grating tooth in the rotation period of the motor, calculates the ratio of the adjacent grating tooth interval clock cycle number in the period of one circle, forms a plurality of arrays by the ratio in the period of one circle, carries out average processing on the plurality of arrays to obtain an average array, confirms the absolute angle value corresponding to each two grating teeth based on the total number of the code wheel and the average array, and stores a series of values formed by the absolute angle values corresponding to each two grating teeth as calibration data into the laser radar; s2, subdividing a laser radar code wheel: calculating the rotation angular velocity of a motor between adjacent grating teeth based on the absolute angle value of the code wheel and the real-time measured grating tooth space clock cycle number of the code wheel, determining the time interval of triggering laser emission pulses between the adjacent grating teeth by the angle resolution of the laser radar and the rotation angular velocity, adjusting the triggering frequency of the laser pulses by the time interval and the instant moment, acquiring the absolute angle value of each code wheel grating tooth according to the pre-stored calibration data of the laser radar and the absolute zero position of the code wheel, calculating the angle fixed value corresponding to the instant moment of each triggering laser pulse by combining the rotation angular velocity of the motor, assigning a value of the scanning angle corresponding to the laser pulse at the current moment by taking the angle fixed value as a scanning stepping angle value, accumulating the scanning stepping angle value corresponding to the laser pulse at the next time on the basis of the scanning angle value, and continuously endowing the scanning stepping angle value to the subsequent scanning angle value until the next grating tooth moment is read.
In the above technical solution, the step of calibrating the relative size of the lidar code wheel is as follows: s11, recording an interval clock cycle number C corresponding to each adjacent code disc grating tooth read by a read head in a period of one rotation of a laser radar motor by utilizing a controller of the laser radar 1 、C 2 ……C n Wherein C 1 Corresponding to the number of clock cycles between the first and second gate teeth, C n Corresponding to the number of clock cycles between the nth and the (n+1) th gate teeth; s12, calculating the ratio of the adjacent gate interval space clock cycle numbers to be K respectively 1 、K 2 ……K n Wherein K is 1 =C 2 /C 1 ，……K n =C n+1 /C n The method comprises the steps of carrying out a first treatment on the surface of the Will K 1 、K 2 ……K n Marked as array A 1 I.e. A 1 =[K 1 ,K 2 ……K n ]The method comprises the steps of carrying out a first treatment on the surface of the S13, repeating the step S11 and the step S12, recording the ratio of the adjacent grid interval space clock cycles corresponding to the laser radar motor in other time rotation periods, and respectively obtaining an array A 2 ，A 3 ……A m The method comprises the steps of carrying out a first treatment on the surface of the S14, pair A 1 ，A 2 ……A m Performing mean processing to obtain a mean array，/>The method comprises the steps of carrying out a first treatment on the surface of the S15, according to the code discTotal number of teeth and mean array->And confirming absolute angle values corresponding to adjacent grating teeth, and storing a series of values formed by the absolute angle values corresponding to every two grating teeth as calibration data into the laser radar to finish the calibration of the relative intervals of grating teeth of the laser radar code disc.
In the above technical solution, in step S14, the mean value processing is as follows: dividing the sum of the corresponding ratio in each array by m to obtain the average value of the ratio, and forming the average value array of the average values of the ratiosThe calculation process is as follows: />，/>……/>Then->、/>……/>Marked as array->I.e. +.>=[/>,/>……/>]。
In the above technical solution, in the step S15, after the serial angle values corresponding to adjacent grating teeth are stored as calibration data in the laser radar, the absolute angle values of the grating teeth of each code disc are calculated and obtained on the premise of knowing the position corresponding to the absolute zero point of the code disc, and the absolute angle values of the grating teeth of each code disc are stored as calibration data in the laser radar.
In the technical scheme, the steps of subdividing the laser radar code wheel are as follows: s21, reading the current grating tooth and the previous adjacent grating teeth of the code disc by using the code disc reading head, and obtaining corresponding adjacent grating tooth clock cycle numbers by a controller based on the laser radar; s22, calculating the calculated rotation angular velocity of the motor between each grating tooth in the previous adjacent grating teeth and the next grating tooth based on the previous adjacent grating tooth space clock cycle number of the current grating tooth and the code wheel calibration data, and calculating the calculated rotation angular velocity of the motor between the current grating tooth and the next grating tooth according to the obtained calculated rotation angular velocity; s23, calculating a current time interval delta t between the current grating tooth and the next grating tooth for triggering two laser pulses according to the angular resolution and the calculated rotation angular velocity of the laser radar n The method comprises the steps of carrying out a first treatment on the surface of the S24, reading current instantaneous time T of current grid teeth of the code disc by the code disc reading head n The previous time interval Deltat for triggering the laser pulse between the previous grating tooth and the current grating tooth is acquired n-1 On the basis of (a), after the triggering of the next laser pulse, the time interval is adjusted to be the current time interval delta t n The code disk reading head reads the adjusted time interval transient time T after adjustment n ' at T n ’+△t n Triggering the next laser pulse emission at the moment; s25, determining the absolute angle value corresponding to each grating tooth according to the calibration link and the current instantaneous time T n And adjusting the time interval transient time T n The number of the laser radar system clocks which can be acquired between' and the rotation angular velocity of a plurality of motors are calculated, and the instantaneous time T of the time interval is obtained by calculation n The fixed angle value corresponding to the triggering laser pulse is taken as the scanning stepping angle value corresponding to the laser pulse at the current moment, so as toAnd taking the scanning angle value corresponding to the laser pulse at the current moment as a basic value, taking the scanning stepping angle value as an accumulation item, and obtaining the scanning angle value of the subsequent laser pulse in an accumulation mode until the next grating tooth moment is read.
In the above technical solution, in the step S22, the method for estimating the rotational angular velocity is to perform first-order linear fitting according to the obtained plurality of calculated rotational angular velocities, so as to obtain the estimated rotational angular velocity.
In the above-described aspect, in the step S22, the first-order linear fitting is an arithmetic approximation of a rotation angular velocity value.
In the above technical solution, in the step S24, at the current instant time T n To the adjustment time interval instant time T n The number of trigger laser pulses can be adjusted according to the processing capacity of the hardware of the laser radar system during the period of reading the code disc.
The invention also provides a laser radar code wheel calibration subdivision device, which comprises a computer program, wherein the computer program can execute the laser radar code wheel calibration subdivision method.
The invention also provides a computer system which comprises the laser radar code wheel calibration subdivision device.
The laser radar code wheel calibration subdivision method, the device and the computer system have the following beneficial effects:
1. the code disc with relatively low precision is calibrated by utilizing the high-precision system internal clock, so that the precision index of the code disc can be effectively improved;
2. by calibrating the code wheel under the integral operation of the laser radar, the angle positioning error caused by the grating tooth processing error and the installation deviation of the code wheel can be solved simultaneously;
3. the ratio of the adjacent grid interval clock cycle number is used as calibration object data, so that calibration errors caused by unstable motor rotation speed in a calibration link are effectively avoided;
4. the laser radar subjected to angle calibration introduces a rotating speed estimation method in a code wheel subdivision link, can effectively cope with fluctuation of the rotating speed of a motor in the radar working process, ensures uniformity (relatively constant interval of laser pulse pointing angles) and accuracy (accurate absolute value of each laser pulse pointing angle) of a radar scanning angle, and effectively avoids the occurrence of image distortion problems such as point cloud image distortion, distortion and the like.
Drawings
FIG. 1 is a schematic diagram of a disclosed mirror scanning lidar structure according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a transceiver-integrated rotary lidar according to a second embodiment of the present invention;
FIG. 3 is a schematic diagram of the overall flow of the method for calibrating and subdividing a laser radar code wheel according to the present invention;
FIG. 4 is a schematic diagram of a specific flow chart of a laser radar code wheel relative size calibration part in the laser radar code wheel calibration subdivision method of the present invention;
FIG. 5 is a schematic flow chart of the principle description of the absolute zero of the calibration code wheel and the laser radar scanning zero of the calibration code wheel of the relative size calibration part of the laser radar code wheel in the laser radar code wheel calibration subdivision method;
FIG. 6 is a schematic diagram showing a position structure between an absolute zero point of a calibration code wheel of a laser radar code wheel relative size calibration part and a laser radar scanning zero point in the laser radar code wheel calibration subdivision method of the present invention;
FIG. 7 is a schematic diagram of a detailed flow of a laser radar code wheel subdivision part in the laser radar code wheel calibration subdivision method of the present invention;
FIG. 8 is a schematic diagram of a laser radar code wheel calibration subdivision device;
FIG. 9 is a schematic diagram of a computer system according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, which should not be construed as limiting the invention.
1. The invention relates to a laser radar system with code wheel calibration and subdivision
The laser radar system of the present invention includes: the device comprises a light source, a light source driving module, a collimation module, a convergence module, a detector driving module, a data processing module and a main control module.
Referring to fig. 1, for the mirror scanning laser radar structure disclosed in the first embodiment, except for a transmitting mirror and a code disc, other parts are fixed, and a motor drives the reflecting mirror and the code disc to rotate to realize scanning, wherein a component for realizing a core scanning function comprises the motor, the code disc, a code reader, the reflecting mirror and a motor driving module.
Referring to fig. 2, for the transceiver-integrated rotary lidar structure disclosed in the second embodiment, except for a motor, a motor driving module and a code wheel (the motor, the motor driving module and the code wheel constitute a lidar stator), the rest components are integrally fixed on a rotor of the motor to constitute a lidar rotor, the lidar rotor is driven to partially rotate by the rotation of the motor to realize scanning, and a component for realizing the core scanning function comprises the motor, the code wheel, a code reader and the motor driving module.
The above is a typical embodiment, and of course, if the technical scheme of the invention is suitable, the scheme can also be used for other types of lidar.
2. The invention has the specific technical scheme that
Referring to fig. 3, the method for calibrating and subdividing the laser radar code wheel comprises two parts of laser radar code wheel relative size calibration and laser radar code wheel subdivision, and specifically comprises the following steps:
s1, calibrating the relative size of a laser radar code disc: the controller of the laser radar records the interval clock cycle number corresponding to each code wheel grating tooth in the rotation period of the motor, calculates the ratio of the adjacent grating tooth interval clock cycle number in the period of one circle, forms a plurality of arrays by the ratio in the period of one circle, carries out average processing on the plurality of arrays to obtain an average array, confirms the absolute angle value corresponding to each two grating teeth based on the total number of the code wheel and the average array, and stores a series of values formed by the absolute angle values corresponding to each two grating teeth as calibration data into the laser radar;
s2, subdividing a laser radar code wheel: calculating the rotation angular velocity of a motor between adjacent grating teeth based on the absolute angle value of the code wheel and the real-time measured grating tooth space clock cycle number of the code wheel, determining the time interval of triggering laser emission pulses between the adjacent grating teeth by the angle resolution of the laser radar and the rotation angular velocity, adjusting the triggering frequency of the laser pulses by the time interval and the instant moment, acquiring the absolute angle value of each code wheel grating tooth according to the pre-stored calibration data of the laser radar and the absolute zero position of the code wheel, calculating the angle fixed value corresponding to the instant moment of each triggering laser pulse by combining the rotation angular velocity of the motor, assigning a value of the scanning angle corresponding to the laser pulse at the current moment by taking the angle fixed value as a scanning stepping angle value, accumulating the scanning stepping angle value corresponding to the laser pulse at the next time on the basis of the scanning angle value, and continuously endowing the scanning stepping angle value to the subsequent scanning angle value until the next grating tooth moment is read.
S1, laser radar code disc relative size calibration method
Referring to fig. 4, the laser radar after assembly is used as a calibration object, and specific calibration steps are as follows:
s11, electrifying and starting the laser radar to a stable working state;
s12, recording the interval clock cycle number C corresponding to each adjacent code disc grating tooth read by the read head in the period of one rotation of the laser radar motor by utilizing the controller of the laser radar 1 、C 2 ……C n Wherein C 1 Corresponding to the number of clock cycles between the first and second gate teeth, C n In one or more embodiments, the controller of the lidar is an FPGA chip inside the lidar system, and of course, the controller may be one or more of a chip such as CPU, GPU, MCU, DSP, soC, ASIC or TTL;
s13, calculating the ratio of the adjacent gate interval space clock cycle numbers to be K respectively 1 、K 2 ……K n Wherein K is 1 =C 2 /C 1 ，……K n =C n+1 /C n The method comprises the steps of carrying out a first treatment on the surface of the Array K 1 、K 2 ……K n Is marked as A 1 I.e. A 1 =[K 1 ,K 2 ……K n ]；
S14, repeating the step S12 and the step S13, recording the ratio of the adjacent grid interval space clock cycles corresponding to the laser radar motor in other time rotation periods, and respectively obtaining an array A 2 ，A 3 ……A m ；
S15, pair A 1 ，A 2 ……A m Performing mean processing to obtain a mean array，/>；
In one or more embodiments, the mean processing is as follows:
dividing the sum of the corresponding ratio in each array by m to obtain the average value of the ratio, and forming the average value array of the average values of the ratiosThe calculation process is as follows:
，/>……/>，
and then will be、/>……/>Marked as array->I.e. +.>=[/>,/>……/>]；
S16, according to the total tooth number and average value array of the code wheelAnd confirming absolute angle values corresponding to two adjacent grating teeth, and storing a series of values formed by the absolute angle values corresponding to every two grating teeth as calibration data into the laser radar to finish the calibration of the relative intervals of grating teeth of the laser radar code disc.
On the premise of knowing the corresponding position of the absolute zero of the code wheel (the calibration of the absolute zero of the code wheel and the scanning zero of the laser radar is referred to herein, and only the principle description is made because of the non-main content of the invention), referring to fig. 5 to 6, step one, fixing the laser radar 1 on the tooling table 2; firstly fixing a scanning baffle 3 in the direction of an increment code wheel zero point angle (not shown in the figure) preliminarily recognized by the laser radar 1, placing a shielding object 4, adhering the scanning baffle 3 and one side of the shielding object 4, which is far away from the laser radar 1, to ensure that the shielding object 4 has obvious characteristics compared with the surrounding environment, wherein the obvious characteristics of the shielding object 4 compared with the surrounding environment means that the pulse width of a surface reflection wave of the shielding object 4 is higher than that of the surrounding environment reflection wave, in one or more embodiments, the pulse width of the surface reflection wave of the shielding object 4 is 2-10 times of that of the surrounding environment reflection wave, the pulse width is the time of a rising edge subtracted from the time of a falling edge of a received optical signal, namely, starting timing after the laser is emitted, recording a time when the signal (rising edge) is received, and recording a time again when the signal disappears (the falling edge), wherein the two time differences are pulse width values; according to different settings of the timing chip and different time resolutions, in the embodiment, the minimum time unit is 7.6ps, the corresponding pulse width value is 1, the corresponding pulse width of the shielding object 4 is 60000-80000, the corresponding pulse width of the surrounding environment is about 10000, and in terms of practical effects, the pulse width of the surrounding environment is fluctuated, and the pulse width of the shielding object 4 reaches more than 2 times of pulse width and is obviously different from the surrounding environment; step three, starting the laser radar 1 to scan to obtain a point cloud image 5; and step four, confirming a scatter diagram (not shown in the figure) obtained by scanning the shielding object 4 in the point cloud image 5, wherein the position on the incremental code disk of the laser radar 1 corresponding to the center of the scatter diagram is the zero point of the incremental code disk of the laser radar 1), and the absolute angle value of each code disk grating tooth can also be calculated. Similarly, the absolute angle value of each grating tooth of the code wheel can be used as calibration data to be stored in the laser radar.
S2, implementation method for subdivision of laser radar code wheel
Under the actual working state of the laser radar, the laser radar relies on the average value array of the code discThe time when the adjacent two grating teeth trigger the emission of laser pulses is determined according to the interval clock cycles corresponding to the grating teeth of the code wheel measured in real time, and the laser radar system performs analysis and judgment at the time when the code wheel reading head reads the grating teeth, see fig. 7, and the specific laser radar code wheel subdivision steps are as follows:
s21, reading the current grating tooth (corresponding to the grating tooth serial number n) and the first plurality of adjacent grating teeth of the code disc by utilizing the code disc reading head, wherein in one or more embodiments, the first plurality of adjacent grating teeth are the first two adjacent grating teeth (corresponding to the grating tooth serial numbers n-1 and n-2 respectively), and of course, the first plurality of adjacent grating teeth can also take other numbers of adjacent grating teeth, for example, the first three adjacent grating teeth (corresponding to the grating tooth serial numbers n-1, n-2 and n-3 respectively) or the first four adjacent grating teeth (corresponding to the grating tooth serial numbers n-1, n-2, n-3 and n-4 respectively); the lidar-based controller obtains a corresponding number of adjacent gate interval clock cycles, which in one or more embodiments are each C n-2 And C n-1 Wherein C n-2 Adjacent gate teeth corresponding to between the n-2 gate teeth and the n-1 gate teethIsolating the clock cycle number C n-1 In one or more embodiments, the controller of the laser radar is an FPGA chip inside the laser radar system, and of course, the controller may be one or more of chips such as CPU, GPU, MCU, DSP, soC, ASIC and TTL;
s22, calculating a calculated rotation angular velocity of the motor between each grating tooth in the previous adjacent grating teeth and the next grating tooth based on the previous adjacent grating tooth space clock cycle number of the current grating tooth and the code wheel calibration data respectively, and calculating the calculated rotation angular velocity of the motor between the current grating tooth and the next grating tooth according to the obtained calculated rotation angular velocity, wherein the calculating method of the calculated rotation angular velocity is to perform first-order linear fitting according to the obtained calculated rotation angular velocity, so as to obtain the calculated rotation angular velocity, the first-order linear fitting is further refined into an arithmetic approximation of the rotation angular velocity value, and of course, in other embodiments, the calculating method of the calculated rotation angular velocity can also be one or more of other estimation algorithms such as a high-order function fitting, a Kalman filtering algorithm and other estimation algorithms, in one or more embodiments, the calculating method is based on C n-2 And C n-1 The first calculated rotation angular velocity V of the motor between the n-2 th grating tooth and the n-1 th grating tooth is calculated by the code wheel calibration data n-2 A second calculated rotation angular velocity V of the motor between the n-1 th grating tooth and the n-th grating tooth n-1 Estimating an estimated rotational angular velocity V of the motor between the nth grating tooth and the (n+1) th grating tooth n While the derived strategy is to set V n-2 、V n-1 And V n The arithmetic series are arranged between the two arithmetic series, and the technical effects of the speed arithmetic approximation are that the method is simple and practical, the calculated amount is small, and the calculation resources of a laser radar system are saved;
s23, calculating a current time interval delta t for triggering two laser pulses between the current grating tooth and the next grating tooth according to the angular resolution of the laser radar and the calculated rotation angular velocity n In one or more embodiments, the angular resolution requirement (e.g., R) and the derived rotational angular velocity V are based on the lidar n Calculating the time interval delta t between the nth grating tooth and the (n+1) th grating tooth for triggering two laser pulses n I.e. Δt n =R/V n ；
S24, reading current instantaneous time T of current grid teeth of the code disc by the code disc reading head n The previous time interval Deltat for triggering the laser pulse between the previous grating tooth and the current grating tooth is acquired n-1 Based on the trigger frequency, when the next laser pulse is triggered, the time interval is adjusted to be the current time interval delta t n The instantaneous time T of the code disk reading head reading adjustment time interval n ' at T n ’+△t n Triggering the next laser pulse firing at a time, in one or more embodiments, at a time T at which the code wheel readhead reads the nth grating tooth n The pulse triggering time interval delta t between the n-1 gate tooth and the n-th gate tooth is acquired n-1 And on the basis of the trigger frequency, after the next laser pulse is triggered, the time interval is adjusted to be the current time interval delta t n The code disk reading head reads the adjusted time interval transient time T after adjustment n ' at T n ’+△t n Triggering the next laser pulse emission at the moment; when the current instantaneous time T of the nth gate tooth is read n To adjust the time interval transient time T n In the 'time period', the number of trigger pulses can be adjusted or determined according to the processing capacity of the hardware of the laser radar system, and if the processing speed of the hardware of the laser radar system is low, the number of trigger pulses can be properly increased (not limited to one) so as to leave enough time for calculating the rotating speed and the pulse trigger time interval;
s25, determining the absolute angle value corresponding to each grating tooth according to the calibration link and the current instantaneous time T n And adjusting the time interval transient time T n The number of the laser radar system clocks which can be acquired between' and the rotation angular velocity of a plurality of motors are calculated, and the instantaneous time T of the time interval is obtained by calculation n The angle fixed value corresponding to the triggering laser pulse is taken as the scanning stepping angle value corresponding to the laser pulse at the current moment, the scanning angle value corresponding to the laser pulse at the current moment is taken as the basic value, and the scanning stepping angle value is taken as the accumulation itemIn one or more embodiments, the method can confirm the calculated rotation angular velocity of the motor only by confirming one calculated rotation angular velocity of the motor, and can confirm the absolute angle value corresponding to each grating tooth in the calibration link because the instantaneous time T before the nth grating tooth is read n And adjusting the time interval transient time T n The number of laser radar system clocks between' can be collected, and the second calculation rotation angular velocity V of the known motor is utilized n-1 The instantaneous time T of the adjustment time interval can be calculated and obtained n And taking the angle fixed value corresponding to the moment trigger pulse as a scanning stepping angle value corresponding to the laser pulse at the current moment, taking the scanning angle value corresponding to the laser pulse at the current moment as a basic value, taking the scanning stepping angle value as an accumulation term, and obtaining the scanning angle value of the subsequent laser pulse in turn in an accumulation mode until the next grating tooth moment is read.
Referring to fig. 8, the laser radar code wheel calibration subdivision device provided by the invention comprises two modules, namely laser radar code wheel relative size calibration and laser radar code wheel subdivision, and specifically comprises the following steps:
the laser radar code disc relative size calibration module: the controller of the laser radar records the interval clock cycle number corresponding to each code wheel grating tooth in the rotation period of the motor, calculates the ratio of the adjacent grating tooth interval clock cycle number in the period of one circle, forms a plurality of arrays by the ratio in the period of one circle, carries out average processing on the plurality of arrays to obtain an average array, confirms the absolute angle value corresponding to each two grating teeth based on the total number of the code wheel and the average array, and stores a series of values formed by the absolute angle values corresponding to each two grating teeth as calibration data into the laser radar;
and the laser radar code wheel subdivision module is used for: calculating the rotation angular velocity of a motor between adjacent grating teeth based on the absolute angle value of the code wheel and the real-time measured grating tooth space clock cycle number of the code wheel, determining the time interval of triggering laser emission pulses between the adjacent grating teeth by the angle resolution of the laser radar and the rotation angular velocity, adjusting the triggering frequency of the laser pulses by the time interval and the instant moment, acquiring the absolute angle value of each code wheel grating tooth according to the pre-stored calibration data of the laser radar and the absolute zero position of the code wheel, calculating the angle fixed value corresponding to the instant moment of each triggering laser pulse by combining the rotation angular velocity of the motor, assigning a value of the scanning angle corresponding to the laser pulse at the current moment by taking the angle fixed value as a scanning stepping angle value, accumulating the scanning stepping angle value corresponding to the laser pulse at the next time on the basis of the scanning angle value, and continuously endowing the scanning stepping angle value to the subsequent scanning angle value until the next grating tooth moment is read.
Referring to fig. 9, the computer system of the present invention includes a lidar code wheel calibration subdivision device.
3. Principle description of the laser radar code wheel calibration subdivision method
1. In the process of calibrating the code wheel of the laser radar, the motor is not in an ideal state of calibration, even if the laser radar rotor performs enough accurate dynamic balance balancing, the motor is installed enough accurately, the feedback control is enough accurate, the rotation speed of the motor still has slight fluctuation, but as the speed change is continuous, no jump exists between adjacent grating teeth, and therefore, for the designated grating teeth, the ratio of the clock cycles between the adjacent grating teeth obtained by multiple calibration is a relatively constant value according to the calibration steps S12, S13 and S14.
2. Also, according to the continuity of the motor rotation speed change, we rely on the first calculation of the rotation angular velocity V n-2 And second calculating a rotational angular velocity V n-1 The estimated rotation angular velocity V can be estimated relatively accurately n . The calculation may be based on the first calculated rotational angular velocity V n-2 And second calculating a rotational angular velocity V n-1 Estimating the estimated rotational angular velocity V n The rotation angular velocity V may be calculated based on the third calculation n-3 First calculating rotational angular velocity V n-2 And second calculating a rotational angular velocity V n-1 Estimating the estimated rotational angular velocity V n Because the value of the rotation angular velocity between the grating teeth to be acquired is calculatedThe more the calculation accuracy is, the higher the calculation accuracy is, so the number of the rotation angular velocities between the grating teeth required to be acquired is not limited to two or three, and can be determined according to the storage and processing capacity of the laser radar system hardware to data. Of course, in the extreme case, only one angular velocity value of the rotation between the grating teeth can be acquired, and the angular velocity value can be used as the angular velocity value of the rotation between the current grating tooth and the next grating tooth directly for subsequent angular subdivision. When more than two inter-gate rotation angular velocity values are collected for calculation, the calculation strategy is not limited to an arithmetic approximation (first order linear fitting) based on velocity values, and the calculation strategy can be one or more of first order linear fitting, high order function fitting, a Kalman filtering algorithm and other pre-estimation algorithms.
3. When the code disk reading head reads the current instant time T of the nth grating tooth n The switching of the triggering period of the laser pulse is not performed, but is performed after one or more laser pulses are triggered according to the original triggering frequency, so that the blocking of the laser pulse (the triggering time interval of two pulses is too short) can be effectively avoided, and meanwhile, enough hardware processing time is reserved for calculation of the rotating speed and the triggering time interval of the laser pulse. The reason for the jam is that the deviation of the rotation speed prediction and the grating tooth spacing of the code wheel calibration are not integer multiples of the laser radar scan angle resolution. Each time the triggering period of the laser pulse is switched, the triggering period falls into practical operation, the pulse emission time interval delta changes correspondingly in order to cope with the change of the motor rotation speed, but the final result ensures that the angle interval value of the adjacent laser pulse is unchanged, namely the angle resolution value of the radar, because every time one grating tooth moment is read, the reference of the fixed value of the scanning angle of all pulses between the grating tooth and the next grating tooth is changed, the scanning speed is changed (the scanning speed is calculated by the angular speed between the previous grating teeth), the time interval of the emitted laser pulse is changed, but the angular speed is multiplied by the interval time = interval angle, the interval angle is unchanged, and the fixed value difference of the angles corresponding to the adjacent pulses is constant. The angle fixed value difference corresponding to the adjacent pulses here is constant.
4. Abbreviation and key term definitions
FPGA (Field Programmable Gate Array): a field programmable gate array;
CPU (Central Processing Unit): a central processing unit;
GPU (Graphic Processing Unit): a graphics processor;
MCU (Microcontroller Unit): a single chip microcomputer;
DSP (Digital Signal Processing): a digital signal processor;
SoC (System on Chip): a system-on-chip;
ASIC (Application Specific Integrated Circuit): an application specific integrated circuit;
TTL (transmitter-transmitter Logic): transistor-transistor logic.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
What is not described in detail in this specification is prior art known to those skilled in the art.
Claims (10)
1. A laser radar code wheel calibration subdivision method is characterized in that: the method comprises the following steps of calibrating the relative size of a laser radar code disc and subdividing the laser radar code disc:
s1, calibrating the relative size of a laser radar code disc: the controller of the laser radar records the interval clock cycle number corresponding to each code wheel grating tooth in the rotation period of the motor, calculates the ratio of the adjacent grating tooth interval clock cycle number in the period of one circle, forms a plurality of arrays by the ratio in the period of one circle, carries out average processing on the plurality of arrays to obtain an average array, confirms the absolute angle value corresponding to each two grating teeth based on the total number of the code wheel and the average array, and stores a series of values formed by the absolute angle values corresponding to each two grating teeth as calibration data into the laser radar;
s2, subdividing a laser radar code wheel: calculating the rotation angular velocity of a motor between adjacent grating teeth based on the absolute angle value of the code wheel and the real-time measured grating tooth space clock cycle number of the code wheel, determining the time interval of triggering laser emission pulses between the adjacent grating teeth by the angle resolution of the laser radar and the rotation angular velocity, adjusting the triggering frequency of the laser pulses by the time interval and the instant moment, acquiring the absolute angle value of each code wheel grating tooth according to the pre-stored calibration data of the laser radar and the absolute zero position of the code wheel, calculating the angle fixed value corresponding to the instant moment of each triggering laser pulse by combining the rotation angular velocity of the motor, assigning a value of the scanning angle corresponding to the laser pulse at the current moment by taking the angle fixed value as a scanning stepping angle value, accumulating the scanning stepping angle value corresponding to the laser pulse at the next time on the basis of the scanning angle value, and continuously endowing the scanning stepping angle value to the subsequent scanning angle value until the next grating tooth moment is read.
2. The lidar code wheel calibration subdivision method of claim 1, wherein: the relative size calibration of the laser radar code disc comprises the following steps:
s11, recording an interval clock cycle number C corresponding to each adjacent code disc grating tooth read by a read head in a period of one rotation of a laser radar motor by utilizing a controller of the laser radar 1 、C 2 ……C n Wherein C 1 Corresponding to the number of clock cycles between the first and second gate teeth, C n Corresponding to the number of clock cycles between the nth and the (n+1) th gate teeth;
s12, calculating the ratio of the adjacent gate interval space clock cycle numbers to be K respectively 1 、K 2 ……K n Wherein K is 1 =C 2 /C 1 ，……K n =C n+1 /C n The method comprises the steps of carrying out a first treatment on the surface of the Will K 1 、K 2 ……K n Marked as array A 1 I.e. A 1 =[K 1 ,K 2 ……K n ]；
S13, repeating the step S11 and the step S12, and recording the laser radarThe motor rotates the ratio of the corresponding adjacent grid interval clock cycle number in a circle of other time to respectively obtain an array A 2 ，A 3 ……A m ；
S14, pair A 1 ，A 2 ……A m Performing mean processing to obtain a mean array，/>；
S15, according to the total tooth number and average value array of the code wheelAnd confirming absolute angle values corresponding to adjacent grating teeth, and storing a series of values formed by the absolute angle values corresponding to every two grating teeth as calibration data into the laser radar to finish the calibration of the relative intervals of grating teeth of the laser radar code disc.
3. The lidar code wheel calibration subdivision method of claim 2, wherein: in the step S14, the mean value processing is as follows:
dividing the sum of the corresponding ratio in each array by m to obtain the average value of the ratio, and forming the average value array of the average values of the ratiosThe calculation process is as follows:
，/>……/>，
and then will be、/>……/>Marked as array->I.e. +.>=[/>,/>……/>]。
4. A lidar code wheel calibration subdivision method as defined in claim 3, wherein: in the step S15, after the serial angle values corresponding to the adjacent grating teeth are stored as calibration data in the laser radar, the absolute angle values of the grating teeth of each code disc are calculated and obtained on the premise of knowing the position corresponding to the absolute zero point of the code disc, and the absolute angle values of the grating teeth of each code disc are stored as calibration data in the laser radar.
5. The lidar code wheel calibration subdivision method of claim 4, wherein: the laser radar code wheel subdivision steps are as follows:
s21, reading the current grating tooth and the previous adjacent grating teeth of the code disc by using the code disc reading head, and obtaining corresponding adjacent grating tooth clock cycle numbers by a controller based on the laser radar;
s22, calculating the calculated rotation angular velocity of the motor between each grating tooth in the previous adjacent grating teeth and the next grating tooth based on the previous adjacent grating tooth space clock cycle number of the current grating tooth and the code wheel calibration data, and calculating the calculated rotation angular velocity of the motor between the current grating tooth and the next grating tooth according to the obtained calculated rotation angular velocity;
s23, calculating a current time interval delta t between the current grating tooth and the next grating tooth for triggering two laser pulses according to the angular resolution and the calculated rotation angular velocity of the laser radar n ；
S24, reading current instantaneous time T of current grid teeth of the code disc by the code disc reading head n The previous time interval Deltat for triggering the laser pulse between the previous grating tooth and the current grating tooth is acquired n-1 On the basis of (a), after the triggering of the next laser pulse, the time interval is adjusted to be the current time interval delta t n The code disk reading head reads the adjusted time interval transient time T after adjustment n ' at T n ’+△t n Triggering the next laser pulse emission at the moment;
s25, determining the absolute angle value corresponding to each grating tooth according to the calibration link and the current instantaneous time T n And adjusting the time interval transient time T n The number of the laser radar system clocks which can be acquired between' and the rotation angular velocity of a plurality of motors are calculated, and the instantaneous time T of the time interval is obtained by calculation n The angle fixed value corresponding to the triggering laser pulse is taken as a scanning stepping angle value corresponding to the laser pulse at the current moment, the scanning angle value corresponding to the laser pulse at the current moment is taken as a basic value, the scanning stepping angle value is taken as an accumulation item, and the scanning angle value of the subsequent laser pulse is obtained in an accumulation mode until the next grating tooth moment is read.
6. The lidar code wheel calibration subdivision method of claim 5, wherein: in the step S22, the method for estimating the rotational angular velocity is to perform first-order linear fitting according to the obtained plurality of calculated rotational angular velocities, thereby obtaining an estimated rotational angular velocity.
7. The lidar code wheel calibration subdivision method of claim 6, wherein: in the step S22, the first-order linear fitting is an arithmetic approximation of the rotation angular velocity value.
8. The lidar code wheel calibration subdivision method of claim 7, wherein: in the step S24, at the current instant time T n To the adjustment time interval instant time T n The number of trigger laser pulses can be adjusted according to the processing capacity of the hardware of the laser radar system during the period of reading the code disc.
9. A lidar code wheel calibration subdivision device, comprising a computer program, characterized in that: the computer program is capable of executing the laser radar code wheel calibration subdivision method as defined in any one of claims 1 to 8.
10. A computer system, characterized in that: the computer system comprising the lidar code wheel calibration subdivision device of claim 9.
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