CN109143206B - Laser radar calibration device and calibration method - Google Patents
Laser radar calibration device and calibration method Download PDFInfo
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- CN109143206B CN109143206B CN201810982381.6A CN201810982381A CN109143206B CN 109143206 B CN109143206 B CN 109143206B CN 201810982381 A CN201810982381 A CN 201810982381A CN 109143206 B CN109143206 B CN 109143206B
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/497—Means for monitoring or calibrating
Abstract
The invention provides a laser radar calibration device and a laser radar calibration method, and belongs to the technical field of laser radar systems. The laser radar calibration device comprises a plurality of reflection units, a plurality of adjusting mechanisms and a control unit, the distance between each reflection unit and the laser radar is continuously changed, the adjusting mechanisms are used for adjusting the included angle between each reflection unit and a laser beam, and the control unit is in communication connection with the laser radar. In the calibration method, a laser radar emits laser beams according to a preset measuring angle direction, and the laser beams irradiate on a plurality of reflecting units; and adjusting an included angle between the reflection unit and the laser beam, acquiring an error between the measured distance and the actual distance, and determining calibration data of the laser radar according to the error, the intensity of the laser signal and the actual distance. According to the laser radar calibration device and the laser radar calibration method, a large amount of continuously-changed measurement data can be obtained without moving the reflection unit, real working conditions are simulated, and calibration efficiency and calibration precision are effectively improved.
Description
Technical Field
The invention belongs to the technical field of laser radar systems, and particularly relates to a laser radar calibration device and a laser radar calibration method.
Background
The laser radar is a radar system that emits a laser beam to detect a characteristic quantity such as a position and a velocity of a target. The laser radar can be used for effectively acquiring information around a space, and in order to realize accurate positioning of a target object, the laser radar needs to be accurately calibrated, so that the ranging precision of the radar is improved, and the reliability of the laser radar in actual work is ensured.
The laser radar needs to calibrate the emitted laser before use or leaving a factory, the traditional mode is that a plurality of standard reflecting plates with different distances from the laser radar are placed in a space which is open, free of interference and few in foreign matters, and the laser radar is calibrated by detecting the ranging accuracy of the laser radar at different distances. Among other things, movement of standard reflective panels between different distances is typically accomplished manually or by movement of an agv (automated Guided vehicle) cart. Because there are the relatively poor and longer problem of measuring time of precision in artifical or AGV dolly removal standard reflecting plate to make laser radar mark inefficiency, mark the precision low, and in practical application, the reflectivity diverse of target object, the laser beam's that laser radar received signal intensity is different, and then influences and marks the precision.
Disclosure of Invention
The invention provides a laser radar calibration device and a calibration method adopting the same, and aims to solve the technical problem that in the prior art, the laser radar calibration and calibration precision is low.
In order to achieve the above object, the present invention provides a laser radar calibration apparatus, including:
the laser radar comprises a plurality of reflection units, a plurality of control units and a plurality of control units, wherein the reflection units are used for receiving laser beams emitted by a laser radar and reflecting the laser beams to the laser radar so that the laser radar measures the laser beams to obtain measurement parameters, and the distance between each reflection unit and the laser radar is continuously changed;
the adjusting mechanisms correspond to the reflecting units one by one and are used for adjusting the included angles between the reflecting units and the laser beams;
the control unit is in communication connection with the laser radar and is used for receiving the measurement parameters sent by the laser radar;
the supporting seat is used for installing each adjusting mechanism, and the supporting seat is perpendicular to the lateral wall of the laser radar in the direction of the lateral wall, and the projection of the supporting seat in the direction of the lateral wall is an involute curve.
The reflection unit is a reflection plate, and each of the adjustment mechanisms includes:
the mounting plate is vertically arranged on the supporting seat, is positioned at a preset measuring point of the laser radar and is used for mounting the reflecting plate;
and the adjusting bolt penetrates through the mounting plate and abuts against the reflecting plate, and is used for adjusting an included angle between the reflecting plate and the mounting plate.
Further, the reflecting plate through the pendulum pivot with the mounting panel is articulated, the pendulum pivot is on a parallel with preset measuring point is in the tangential direction on the involute curve, just the pendulum pivot with laser beam coplane.
Furthermore, each reflecting plate is arranged at equal intervals by taking an axis which vertically passes through the circle center as a rotating shaft, and the included angle between every two adjacent reflecting plates is the same as the resolution of the preset rotating angle of the laser radar.
Further, the calculation formula of the length of each reflection plate along the direction of the swing shaft is as follows:
l＝2*(tanθ/2)*(r+r*ψ)
wherein l is the length of the reflection plate at a preset measurement point, and r is the radius of the base circle of the involute curve; psi is a preset measuring angle corresponding to the preset measuring point, and theta is a preset rotation angle resolution of the laser radar.
The laser radar calibration device provided by the invention has the beneficial effects that the closed-loop receiving of the laser beam emitted by the laser radar is realized by arranging the reflection unit and the control unit, and the measurement data of the laser radar is obtained; the distance between each reflecting unit and the laser radar is continuously changed, and the included angle between each reflecting unit and the laser beam can be adjusted through the adjusting mechanism, so that the change of the signal intensity of the laser beam received and reflected by the laser radar is realized, and the change of the signal intensity of the laser beam in the application of the laser radar is really simulated; in practical application, the transmitting frequency of the laser beam of the laser radar can be set, and the distance between each reflecting unit and the laser radar is continuously changed, so that the measuring data of the continuously changed measuring distance can be obtained. According to the scheme, the position of the reflection unit and the included angle between the reflection unit and the laser beam are positioned only before calibration is started, the laser radar emits the laser beam according to the preset emission frequency, the measurement data of the laser radar at the continuously-changed measurement distance can be obtained, the measurement data are more, and noise data can be filtered; the position of the reflecting unit does not need to be moved, and personnel are not needed to participate in the calibration process, so that the calibration efficiency is improved; the intensity of the laser signal at each measuring distance is different, the influence of the intensity of the laser signal on the measured data can be analyzed and obtained, and the reliability of the calibration precision is improved. According to the laser radar calibration device provided by the invention, the automation of the calibration process is realized through the arrangement of the plurality of reflection units with continuously changing distances from the laser radar, the measurement data under different laser signal intensities can be obtained through the adjustable angles between the reflection units and the laser beams, the influence of the laser signal intensities on the measurement data is obtained, the calibration efficiency is effectively improved, and the calibration precision and the reliability are improved.
The invention also provides a laser radar calibration method, which comprises the following steps:
the method comprises the steps that the laser radar is arranged at a target position, a plurality of reflection units are arranged, each reflection unit corresponds to a preset measuring angle of the laser radar, and the distance between each reflection unit and the laser radar is continuously changed;
adjusting and setting an included angle between each reflection unit and a laser beam emitted by the laser radar;
controlling a laser radar to emit laser beams according to a preset measuring angle so that each laser beam is projected on a corresponding reflection unit;
acquiring the actual distance between the laser radar and each reflecting unit;
obtaining the measuring distance and the measuring signal intensity of the laser radar and each reflecting unit;
and determining the error between the measured distance and the actual distance, and determining the calibration data of the laser radar according to the error, the signal intensity and the actual distance.
Further, each reflection unit is vertically arranged on a supporting seat through an adjusting mechanism, wherein the projection of the side wall of the supporting seat facing the laser radar along the direction vertical to the side wall is an involute curve;
arranging a laser radar at the circle center position of the base circle of the involute curve;
the distance between each reflection unit and the laser radar is continuously changed, and the change relationship is as follows:
d＝r+r*ψ
wherein r is the radius of the base circle of the involute curve; psi is a preset measuring angle at a preset measuring point; d is the actual distance between the laser radar and each reflection unit at the preset measuring point.
Furthermore, the adjusting mechanisms correspond to the reflecting units one by one,
the adjusting and setting of the incident angle between each reflection unit and the laser beam includes:
controlling the reflection units to swing around the adjusting mechanisms, and adjusting and setting the included angle between each reflection unit and the corresponding adjusting mechanism to a target included angle; wherein the swing axis of the reflection unit is coplanar with the laser beam.
Further, the obtaining an error between the measured distance and the actual distance, and determining calibration data of the laser radar according to the error, the signal strength, and the actual distance includes:
acquiring actual measurement time t of the laser radar at the preset measurement angle, wherein the actual measurement time t is the time from the laser beam emission of the laser radar to the laser beam reflection of the laser radar;
acquiring the signal intensity tl of the received reflected laser beam of the laser radar at the preset measuring angle;
calculating and obtaining theoretical measurement time t' ═ d × 2/v of the laser radar at the preset measurement angle, wherein v is the speed of light;
calculating an error Wc-t-d 2/v between the actual measurement time t and the theoretical measurement time t' at the preset measurement angle;
fitting the error W by least squaresCEquation W relating signal intensity tl of reflected laser beam to said actual distance dCF (tl, d), wherein the signal intensity tl of the reflected laser beam changes along with the change of the included angle between the reflector and the laser beam;
and acquiring a relation equation f (tl, d) of an actual distance d between the laser radar and the measuring point on the reflecting plate, the signal intensity tl of the reflected laser beam and the actual measuring time t at the preset measuring angle, wherein the relation equation f (tl, d) is t-d × 2/v.
The laser radar calibration method provided by the invention has the beneficial effects that the laser radar rotationally scans and emits laser beams in the preset measurement angle direction, the positions of the laser radar and the reflection units are arranged, so that the laser beams irradiate on the reflection units, the reflection units are multiple, each reflection unit corresponds to one preset measurement angle of the laser radar, the actual distance between the laser radar and each reflection unit is known and continuously changes, before the laser radar starts to measure, the included angle between each reflection unit and the laser beams is adjusted, the measurement distance between the laser radar and the reflection units in each preset measurement angle direction and the measurement signal intensity are obtained, and then the calibration data of the laser radar can be determined according to the error between the measurement distance and the actual distance, the signal intensity and the actual distance. The distances between the multiple reflection units and the laser radar are continuously changed, the measurement data of the continuously changed measurement distances can be obtained without moving the reflection units, noise data can be eliminated, and the accuracy of fitting analysis is improved; the change of the signal intensity is measured, so the influence of the acquired signal intensity on the calibration precision can be analyzed. The laser radar calibration method provided by the invention truly simulates the use condition of the laser radar, and has high calibration efficiency and high calibration precision.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a first schematic structural diagram of a laser radar calibration apparatus according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram ii of a laser radar calibration apparatus according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of an adjustment mechanism provided in an embodiment of the present invention;
fig. 4 is an involute curve coordinate diagram of a cross section of the support seat according to the embodiment of the present invention.
Wherein, each reference numeral:
1. a reflection unit; 101. a reflective plate; 2. a laser radar; 3. an adjustment mechanism; 301. mounting a plate; 302. adjusting the bolt; 303. a swing shaft; 4. supporting seat: 5. a control unit; 6. a base circle; 7. an involute curve; 8. the center of the base circle; 9. the measurement point D is preset.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In the description of the present invention, "a plurality" or "a plurality" means two or more.
Referring to fig. 1 and fig. 2, a laser radar calibration apparatus according to the present invention will now be described. Lidar calibration device, be used for maring lidar 2, including a plurality of reflection unit 1, with a plurality of adjustment mechanism 3 of each reflection unit 1 one-to-one and be used for receiving the control unit 5 of the measurement parameter that lidar 2 sent, each reflection unit 1 all is used for receiving the laser beam of 2 launches of lidar, and reflect laser beam to lidar 2, so that lidar 2 measures laser beam and obtains measurement parameter, the distance continuous variation between each reflection unit 1 and the lidar 2, adjustment mechanism 3 is used for adjusting each reflection unit 1 and laser beam's contained angle, control unit 5 is connected with lidar 2 communication.
The laser radar 2 scans and emits laser beams in a rotating mode, the laser beams are received by the laser radar 2 after being reflected by the reflecting unit 1, and the measuring distance between the laser radar 2 and the reflecting plate 101 at the position is obtained through calculation of the time from the laser beam emitting to the reflected laser beams by the laser radar 2.
Optionally, the laser radar 2 is horizontally arranged to horizontally emit a laser beam, the reflection unit 1 is a reflection plate 101, the multiple reflection plates 101 are continuously arranged through the adjusting mechanism 3, and each reflection plate 101 is arranged at a preset measurement angle and the distance between the reflection plate 101 and the laser radar 2 is continuously changed; in practical application, the angle between each reflecting plate 101 and the laser beam is adjusted in advance through the adjusting mechanism 3, at this time, the laser signal intensity received by the laser radar 2 at each reflecting plate 101 is different, the laser radar 2 scans each reflecting plate 101 in a rotating manner to obtain the measurement distance at each reflecting plate 101 and the measurement signal intensity at the reflecting plate 101, and as each reflecting plate 101 is set according to the preset measurement angle, the measurement distance at the preset measurement angle, that is, the measurement signal intensity, is obtained.
Optionally, the control Unit 5 is a microprocessor (Microcontroller Unit), and the laser radar 2 sends the known preset measurement angle, the measurement distance obtained by measurement, the signal strength at the preset measurement angle, and the actual distance between the laser radar 2 at the known preset measurement angle and the measurement point on the reflective plate 101 to the control Unit 5.
The laser radar calibration device provided by the invention has the beneficial effects that the closed-loop receiving of the laser beam emitted by the laser radar is realized by arranging the reflection unit and the control unit, and the measurement data of the laser radar is obtained; the distance between each reflecting unit and the laser radar is continuously changed, and the included angle between each reflecting unit and the laser beam can be adjusted through the adjusting mechanism, so that the change of the signal intensity of the laser beam received and reflected by the laser radar is realized, and the change of the signal intensity of the laser beam in the application of the laser radar is really simulated; in practical application, the transmitting frequency of the laser beam of the laser radar can be set, and the distance between each reflecting unit and the laser radar is continuously changed, so that the measuring data of the continuously changed measuring distance can be obtained. According to the scheme, the position of the reflection unit and the included angle between the reflection unit and the laser beam are positioned only before calibration is started, the laser radar emits the laser beam according to the preset emission frequency, the measurement data of the laser radar at the continuously-changed measurement distance can be obtained, the measurement data are more, and noise data can be filtered; the position of the reflecting unit does not need to be moved, and personnel are not needed to participate in the calibration process, so that the calibration efficiency is improved; the intensity of the laser signal at each measuring distance is different, the influence of the intensity of the laser signal on the measured data can be analyzed and obtained, and the reliability of the calibration precision is improved. According to the laser radar calibration device provided by the invention, the automation of the calibration process is realized through the arrangement of the plurality of reflection units with continuously changing distances from the laser radar, the measurement data under different laser signal intensities can be obtained through the adjustable angles between the reflection units and the laser beams, the influence of the laser signal intensities on the measurement data is obtained, the calibration efficiency is effectively improved, and the calibration precision and the reliability are improved.
As an embodiment of the lidar calibration apparatus provided by the present invention, please refer to fig. 1 and fig. 2, it preferably includes a supporting seat 4 for mounting each adjusting mechanism 3, and a projection of a side wall of the supporting seat 4 facing the lidar 2 along a direction perpendicular to the side wall is an involute curve 7.
The curve intersecting all tangents of one curve to form a right angle is called as an involute of the curve, a common involute means an involute of a circle, and an involute curve 7 in the scheme is an involute curve 7 of a base circle 6. The laser radar 2 is arranged at the center 8 of the base circle of the involute curve 7, and the distance between each point on the side wall of the laser radar 2 and the support seat 4 changes continuously and linearly.
Reflecting plate 101 passes through adjustment mechanism 3 and installs perpendicularly on supporting seat 4, sets up the recess that is used for fixed adjustment mechanism 3 at the upper surface of supporting seat 4, and this recess is on a parallel with the lateral wall of supporting seat 4, then the distance between a plurality of reflecting plates 101 and laser radar 2 satisfies the characteristics of involute curve 7 promptly.
In this scheme, for the supporting seat 4 of curve 7 and the recess of setting in supporting seat 4 top that gradually bursts at the seams through the projection that sets up the lateral wall, be convenient for carry out reflecting plate 101 fixed for the projection of each reflecting plate 101's measuring point on supporting seat 4 is the curve that gradually bursts at the seams, simple to operate, the location of completion each reflecting plate 101 that can be swift. In practical application, laser radar 2 can be the frequency transmission laser beam of predetermineeing, triggers once in each same angle interval position, and laser radar 2's signal acquisition frequency and reflecting plate 101's number one-to-one, then laser radar 2 and each reflecting plate 101's distance is continuous linear variation, is convenient for eliminate accidental error and carries out fitting analysis, eliminates accidental error, improves and marks the precision.
As a specific embodiment of the laser radar calibration device provided by the present invention, please refer to fig. 1 and fig. 3, the adjusting mechanism 3 includes an installation plate 301 for installing the reflection plate 101, and an adjusting bolt 302 for adjusting an included angle between the reflection plate 101 and the installation plate 301, wherein the installation plate 301 is vertically disposed on the support base 4 and located at a preset measurement point of the laser radar 2; the adjusting bolt 302 passes through the mounting plate 301 and abuts against the reflection plate 101.
Optionally, the mounting plate 301 is a rectangular frame provided with support rods, the support rods are vertically fixed to the rectangular frame, the rectangular frame is bilaterally symmetrical with respect to the support rods, the reflecting plate 101 is adjusted to swing with respect to the rectangular frame through adjusting bolts 302, and the two adjusting bolts 302 are respectively located on the upper side and the lower side of the rectangular frame, penetrate through the rectangular frame, abut against the reflecting plate 101 and are hinged to the rectangular frame. Laser radar 2 predetermine the measuring point and predetermine measuring angle and be confirmed by laser radar 2's rotational scanning speed and predetermined laser emission frequency, and the bracing piece is vertical to be fixed at the upper surface of supporting seat 4 in this embodiment, and is located laser radar 2 predetermines measuring point department, and guarantee laser beam all can be received and feedback by reflecting plate 101. In this embodiment, the adjusting bolt is screwed to adjust the included angle between the laser beam 2 and the reflector 101 so as to adjust the intensity of the laser signal received by the laser radar 2, the adjusting bolt with a fixed pitch and a drift diameter can be set, the swing angle of the reflector relative to the rectangular frame is determined by screwing the adjusting bolt, so that the swing angle can be accurately adjusted and set, in practical application, the swing angle with multi-level changes can be set according to the number of the reflectors, the laser radar receives various laser signal intensities, and the diversity of the measurement data is improved.
As a specific embodiment of the laser radar calibration apparatus provided by the present invention, please refer to fig. 1 and fig. 2, the reflection plate 101 is hinged to the mounting plate 301 through a swing shaft 303, the swing shaft 303 is parallel to a tangential direction of a preset measurement point 9 of the laser radar 2 on the involute curve 7, and the swing shaft 303 is coplanar with the laser beam. The swing rotating shaft 303 is parallel to the tangential direction of the preset measuring point 9 of the laser radar 2 on the involute curve 7, so that when the swing rotating shaft 303 swings, an included angle between a plane perpendicular to the swing rotating shaft 303 and the laser beam 2 is always unchanged, and the swing rotating shaft 303 has only one swing freedom degree. In this embodiment, the swing shaft 303 is coplanar with the laser beam and is along the tangential direction of the preset measuring point 9, so that the laser beam always irradiates on the swing shaft 303, and screwing the adjusting bolt 302 only changes the incident angle of the laser beam on the reflective plate 101, thereby ensuring that the laser radar 2 can always receive the reflected laser beam.
As a specific embodiment of the lidar calibration apparatus provided by the present invention, please refer to fig. 1 and fig. 2, the reflective plates 101 are arranged at equal intervals by using an axis passing through the circle center 8 as a rotation axis, and an included angle between two adjacent reflective plates 101 is the same as a preset rotation angle resolution of the lidar 2.
The preset rotation angle resolution of the laser radar 2 is the angle of rotation of the laser beam emitted by the laser radar 2 every time, the angle is determined by the rotation scanning speed of the laser radar 2 and the preset laser emission frequency, and at this time, the preset measurement point and the preset measurement angle of the laser radar 2 are known; the plurality of reflection plates 101 are fixedly installed on the supporting base 4, the radius and the expansion angle of the base circle 6 of the supporting base 4 are set, namely the scanning range of the laser radar 2 is known, so that when the laser radar 2 rotates according to the preset transmitting frequency and the rotating scanning speed, fixed acquisition times exist, and the acquisition angle at each time is known. In a specific embodiment, the preset rotation angle resolution of the laser radar is 2 °, the expansion angle of the involute curve 7 is 270 °, the laser radar 2 has 135 preset measurement points, the angle difference between every two adjacent preset measurement points is 2 °, the 135 reflecting plates 101 are arranged, the reflecting plates 101 are arranged on the upper surface of the supporting seat 4 at equal intervals according to 2 ° intervals, the multiple reflecting plates 101 are perpendicular to the laser beams at the preset measurement points, the distances between each reflecting plate 101 and the laser radar 2 are different, and the linear change is continuous, so that the subsequent fitting analysis is facilitated.
Referring to fig. 1, fig. 2 and fig. 3, as a specific embodiment of the laser radar calibration apparatus provided by the present invention, a calculation formula of the length of the reflection plate 101 along the direction of the swing shaft 303 is as follows:
l＝2*(tanθ/2)*(r+r*ψ)
wherein l is the length of the reflection plate at a preset measurement point, and r is the radius of the base circle of the involute curve; ψ is a preset measurement angle at the preset measurement point, and θ is a preset rotation angle resolution of the laser radar.
It is known that the distances between each reflecting plate 101 and the laser radar 2 are different, and when the laser radar 2 rotationally scans at a preset fixed speed, the larger the distance between the reflecting plate 101 and the laser radar 2 is, the larger the area of the reflecting plate 101 is.
The connecting line between the starting point of the involute curve 7 and the center 8 of the base circle is an X axis, the preset rotation angle resolution theta of the laser radar is 2 degrees, and the first preset measurement point psi1Is 2 DEG, and a second predetermined measuring point psi2Is 4 deg., and a third predetermined measurement point psi3The preset measurement angle is 6 degrees, and so on, the nth measurement point psinThe preset measurement angle of (2 n). The reflecting plate 101 is perpendicular to the laser beam, the swing shaft 303 is parallel to the tangent of the preset measuring point on the involute curve 7, and the laser beam irradiates on the central point of the reflecting plate 101, so that the length of the reflecting plate 101 at each preset measuring point can be obtained according to the following formula:
l＝2*(tanθ/2)*(r+r*ψ)
wherein, (r + r ψ) is a distance from the reflecting plate 101 to the laser radar 2 at a preset measuring point, determined by characteristics of an involute curve, an angle between the laser beam and the X axis is θ/2, the laser beam is irradiated at a center point of the reflecting plate 101, and thus a length of a half reflecting plate is (tan θ/2) (r + r ψ) is a length of a half reflecting plate. The reflecting plate 101 can be arranged according to the l processing, interference does not exist among all the reflecting plates 101, all laser beams in the rotary scanning of the laser radar 2 are enabled to be irradiated on the reflecting plate 101, and omission does not exist.
The laser radar calibration method provided by the invention will now be explained. The method comprises the following steps:
the method comprises the steps that a laser radar 2 is arranged at a target position, a plurality of reflection units 1 are arranged, each reflection unit 1 corresponds to a preset measurement angle psi of the laser radar 2, and the distance between each reflection unit 1 and the laser radar 2 changes continuously;
adjusting and setting an included angle between each reflection unit 1 and a laser beam emitted by the laser radar 2;
controlling the laser radar 2 to emit a plurality of laser beams according to a preset measurement angle psi, so that each laser beam is projected on the corresponding reflection unit 1;
acquiring the actual distance d between the laser radar 2 and each reflection unit 1;
obtaining the measurement distance and the measurement signal intensity tl of the laser radar 2 and each reflection unit 1;
and determining an error Wc of the measured distance and the actual distance d, and determining calibration data of the laser radar 2 according to the error, the signal strength tl and the actual distance d.
In practical applications, the predetermined measurement point and the predetermined measurement angle ψ of the laser radar 2 are determined by the rotational scanning speed of the laser radar 2 and the predetermined laser emission frequency. Optionally, the reflection unit 1 is a reflection plate 101, there are a plurality of reflection plates 101, the plurality of reflection plates 101 correspond to the preset measurement angle ψ one-to-one, and the distance relationship between the plurality of reflection plates 101 and the laser radar 2 changes.
Reflecting plate 101 passes through adjustment mechanism 3 and adjusts contained angle between it and the laser beam, the 2 levels of laser radar arrange, the laser beam level is shone, the center of reflecting plate 101 is located same horizontal plane with laser beam, the vertical arrangement of reflecting plate 101, then with laser beam between the contained angle be 90, shine laser beam total reflection on reflecting plate 101 this moment and receive to laser radar 2, laser radar 2's measuring signal intensity tl is the biggest this moment, adjust reflecting plate 101 and laser beam's right-angled contained angle, can adjust laser radar 2's measuring signal intensity tl.
The laser radar calibration method provided by the invention has the beneficial effects that the laser radar rotationally scans and emits laser beams in the preset measurement angle direction, the positions of the laser radar and the reflection units are arranged, so that the laser beams irradiate on the reflection units, the reflection units are multiple, each reflection unit corresponds to one preset measurement angle of the laser radar, the actual distance between the laser radar and each reflection unit is known and continuously changes, before the laser radar starts to measure, the included angle between each reflection unit and the laser beams is adjusted, the measurement distance between the laser radar and the reflection units in each preset measurement angle direction and the measurement signal intensity are obtained, and then the calibration data of the laser radar can be determined according to the error between the measurement distance and the actual distance, the signal intensity and the actual distance. The distances between the multiple reflection units and the laser radar are continuously changed, the measurement data of the continuously changed measurement distances can be obtained without moving the reflection units, noise data can be eliminated, and the accuracy of fitting analysis is improved; the change of the signal intensity is measured, so the influence of the acquired signal intensity on the calibration precision can be analyzed. The laser radar calibration method provided by the invention truly simulates the use condition of the laser radar, and has high calibration efficiency and high calibration precision reliability.
As a specific implementation manner of the laser radar calibration method provided by the invention, each reflection unit 1 is vertically installed on a supporting seat 4 through an adjusting mechanism 3, wherein the projection of the side wall of the supporting seat 4 facing the laser radar 2 along the direction vertical to the side wall is an involute curve 7;
arranging the laser radar 2 at the position of the center 8 of the base circle of the involute curve 7;
the distance between each reflection unit and the laser radar is continuously changed, and the change relationship is as follows:
d＝r+r*ψ
wherein r is the radius of the base circle of the involute curve; psi is a preset measurement angle; d is the actual distance between the laser radar and the measuring point on the reflecting plate when the measuring angle is preset.
In practical application, a positioning mark is drawn on a plane, the positioning mark forms a reference involute curve, the radius of a base circle of the reference involute curve is the same as that of a base circle 6 of an involute curve 7 of the reflecting plate 101, the supporting seat 4 is horizontally placed and is overlapped with the positioning mark, and the construction of a calibration field is completed. The origin of the calibration field is the circle center 8 of the base circle 6 of the involute curve 7 of the supporting seat 4, and the laser radar 2 is located at the origin of the calibration field. Each reflection plate 101 is fixed on the upper surface of the supporting seat 4 along a curve parallel to the side wall of the supporting seat 4 and located at the position of the predetermined measurement point 9, so that the projection of each predetermined measurement point 9 on each reflection plate 101 on the supporting seat 4 is also an involute curve. The actual distance between the measuring point at the preset measuring angle psi and the origin is determined by the characteristics of the involute curve, namely the actual distance d between the measuring point on each reflecting plate 101 and the laser radar 2, and the distance between the measuring point at each preset measuring angle psi on the reflecting plate 101 of the involute curve 7 and the center 8 of the base circle 6 is fixed and continuously and linearly changed.
Each angle on the involute curve 7 corresponds to different distances, each distance is connected with the central dot and is intersected with one point on the circle, the tangent line of the circle is made by the point, and the connection line of the actual distance point and the central dot is perpendicular to the tangent line.
As shown in fig. 3, a coordinate system is established with a center 8 of a base circle 6 as an origin, a point a is located on the base circle 6 and is a starting point of an involute curve 7, a direction of a connecting line between the origin 0 and the point a is an X axis, a preset measurement angle ψ is a radian included angle between a measurement point and the X axis, a length of 0C is an actual distance d at the preset measurement angle ψ, a point B is an intersection of 0C and the base circle 6, and BM is a tangent line at the intersection. The radius of the base circle 6 is r, and the parameter equation of the obtained involute is as follows:
X＝r(cosψ+ψsinψ)
Y＝r(sinψ-ψcosψ)
the calculation formula for calculating the actual distance d between the measurement point at the preset angle psi and the origin point by using the equation is as follows:
d＝r+r*ψ
the continuous linear change is realized between psi and d, the coordinates of the measuring points are expressed as phi, d, the minimum value of the actual distance d between the measuring points and the origin is r, the maximum value is 2 pi r, and the coordinates of the measuring points can be obtained by setting the laser emission frequency of the laser radar 2. Through setting up supporting seat 4 in this scheme, each reflecting plate 101 of realization that can convenient and fast arranges according to the curve that gradually bursts at seams, and the distance linearity between each reflecting plate and the laser radar this moment changes, and the one-to-one, conveniently carries out contrastive analysis, and the accessible sets up laser radar's measuring frequency, acquires more measured data, and the fitting accuracy is high.
As a specific implementation manner of the laser radar calibration method provided by the present invention, the adjusting mechanism 3 corresponds to each reflection unit 1 one to one, and adjusting and setting the included angle between the reflection plate 101 at each preset measurement angle ψ and the laser beam includes:
controlling the reflection units 1 to swing around the adjusting mechanisms 3, and adjusting and setting the included angle between each reflection unit 1 and the corresponding adjusting mechanism 3 to a target included angle; and the swinging axis of the reflecting plate is coplanar with the laser beam.
Optionally, the adjusting mechanism 3 includes a mounting plate 301 for mounting the reflection plate 101, and an adjusting bolt 302 for adjusting an included angle between the reflection plate 101 and the mounting plate 301, the adjusting bolt 302 is screwed to adjust an included angle between the laser beam 2 and the reflection plate 101 and further an angle at which the laser beam irradiates on the reflection plate 101, so as to adjust the laser signal intensity tl received by the laser radar 2, the adjusting bolt with a fixed pitch and a path can be set, it is determined that the adjusting bolt screws a circle of reflection plate to a swing angle relative to the rectangular frame, so as to achieve accurate adjustment and setting of the swing angle, in practical application, the swing angle with multi-level changes can be set according to the number of the reflection plates, the laser radar receives various laser signal intensities, and diversity of measurement data is improved.
As a specific implementation manner of the laser radar calibration method provided by the present invention, the obtaining an error between the measured distance and the actual distance, and the determining calibration data of the laser radar according to the error, the laser signal intensity, and the actual distance includes:
acquiring actual measurement time t of the laser radar 2 at a preset measurement angle psi, wherein the actual measurement time t is the time from the laser beam emission of the laser radar 2 to the reflected laser beam reception;
acquiring the signal intensity tl of the received reflected laser beam of the laser radar at the preset measuring angle;
calculating to obtain theoretical measurement time t' ═ d × 2/v of the laser radar 2 at a preset measurement angle ψ, wherein v is the speed of light;
calculating to obtain an error Wc between the actual measurement time t and the theoretical measurement time t' at the preset measurement angle psi;
fitting error W by least squaresCEquation W of relation between signal intensity tl of reflected laser beam and actual distance dCF (tl, d), wherein the signal intensity tl of the reflected laser beam followsThe included angle between the reflecting plate and the laser beam changes;
and acquiring a relation equation f (tl, d) of an actual distance d between the laser radar and a measuring point on the reflecting plate, the intensity tl of a reflected laser beam signal and an actual measuring time t at a preset measuring angle psi, wherein t-d is 2/v.
The speed of the laser beam in the air is a known value, so that the distance measured by the laser radar 2 at the preset measurement angle ψ from the reflecting plate 101 can be calculated from the actual measurement time t. The laser radar 2 transmits the above data in real time to the control unit 5 for analysis arithmetic processing, wherein the measurement data is transmitted in the form of (ψ, d).
Least squares (also known as the least squares method) is a mathematical optimization technique. It finds the best function match of the data by minimizing the sum of the squares of the errors; unknown data can be simply obtained by using a least square method, and the sum of squares of errors between the obtained data and actual data is minimum; the least squares method can also be used for curve fitting. In a specific embodiment, the lidar 2 triggers a measurement every 2 ° of rotation, and the lidar 2 then measures the actual measurement time t at a plurality of preset measurement angles ψn(in ns) by a predetermined measurement angle psin(in units of arc) signal intensities tl of the reflected laser beams received by the lidar at the plurality of predetermined measurement anglesn(in ns) and the lidar 2 at a plurality of predetermined measurement angles psinThe actual distance d between the time and the measuring point on the reflecting plate 101n(in m) to a microcontroller which fits the error W by least squaresCEquation W of relation between signal intensity tl of reflected laser beam and actual distance dCF (tl, d); and then calculating the relation between the actual distance d of the measuring point and the measuring time t and the signal intensity t1 to finish calibration.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (5)
1. Laser radar calibration device, its characterized in that includes:
the laser radar comprises a plurality of reflection units, a plurality of control units and a plurality of control units, wherein the reflection units are used for receiving laser beams emitted by a laser radar and reflecting the laser beams to the laser radar so that the laser radar measures the laser beams to obtain measurement parameters, and the distance between each reflection unit and the laser radar is continuously changed;
the adjusting mechanisms correspond to the reflecting units one by one and are used for adjusting the included angles between the reflecting units and the laser beams;
the control unit is in communication connection with the laser radar and is used for receiving the measurement parameters sent by the laser radar;
the supporting seat is used for mounting each adjusting mechanism, and the projection of the side wall of the supporting seat facing the laser radar along the direction vertical to the side wall is an involute curve;
the reflection unit is a reflection plate, and each of the adjustment mechanisms includes:
the mounting plate is vertically arranged on the supporting seat, is positioned at a preset measuring point of the laser radar and is used for mounting the reflecting plate;
the adjusting bolt penetrates through the mounting plate and abuts against the reflecting plate, and is used for adjusting an included angle between the reflecting plate and the mounting plate; the reflecting plates are arranged at equal intervals by taking an axis which vertically passes through the circle center as a rotating shaft, and the included angle between every two adjacent reflecting plates is the same as the resolution of the preset rotating angle of the laser radar;
the reflecting plate is hinged with the mounting plate through a swing rotating shaft, the swing rotating shaft is parallel to the tangential direction of the preset measuring point on the involute curve, and the swing rotating shaft and the laser beam are coplanar;
the calculation formula of the length of each reflecting plate along the direction of the swing rotating shaft is as follows:
l＝2*(tanθ/2)*(r+r*ψ)
wherein l is the length of the reflection plate at a preset measurement point, and r is the radius of the base circle of the involute curve; psi is a preset measuring angle corresponding to the preset measuring point, and theta is a preset rotation angle resolution of the laser radar.
2. A calibration method for a lidar calibration device as defined in claim 1, comprising the steps of:
the method comprises the steps that the laser radar is arranged at a target position, a plurality of reflection units are arranged, each reflection unit corresponds to a preset measuring angle of the laser radar, and the distance between each reflection unit and the laser radar is continuously changed;
adjusting and setting an included angle between each reflection unit and a laser beam emitted by the laser radar;
controlling a laser radar to emit laser beams according to a preset measuring angle so that each laser beam is projected on a corresponding reflection unit;
acquiring the actual distance between the laser radar and each reflecting unit;
obtaining the measuring distance and the measuring signal intensity of the laser radar and each reflecting unit;
and determining the error between the measured distance and the actual distance, and determining the calibration data of the laser radar according to the error, the signal intensity and the actual distance.
3. A calibration method of a lidar calibration device according to claim 2, wherein each reflection unit is vertically mounted on a supporting base through an adjusting mechanism, wherein a projection of a side wall of the supporting base facing the lidar along a direction perpendicular to the side wall is an involute curve;
arranging a laser radar at the circle center position of the base circle of the involute curve;
the distance between each reflection unit and the laser radar is continuously changed, and the change relationship is as follows:
d＝r+r*ψ
wherein r is the radius of the base circle of the involute curve; psi is a preset measuring angle at a preset measuring point; d is the actual distance between the laser radar and each reflection unit at the preset measuring point.
4. A calibration method for a lidar calibration device according to claim 3, wherein the adjusting mechanism corresponds to each reflection unit one to one, and adjusts and sets an included angle between each reflection unit and the laser beam, comprising:
controlling the reflection units to swing around the adjusting mechanisms, and adjusting and setting the included angle between each reflection unit and the corresponding adjusting mechanism to a target included angle; wherein the swing axis of the reflection unit is coplanar with the laser beam.
5. A calibration method for lidar calibration apparatus according to claim 4, wherein determining an error between the measured distance and the actual distance, and determining calibration data for the lidar based on the error, the signal strength, and the actual distance comprises:
acquiring actual measurement time t of the laser radar at the preset measurement angle, wherein the actual measurement time t is the time from the laser beam emission of the laser radar to the reflected laser beam receiving of the laser radar;
acquiring the signal intensity tl of the received reflected laser beam of the laser radar at the preset measuring angle;
calculating and obtaining theoretical measurement time t' ═ d × 2/v of the laser radar at the preset measurement angle, wherein v is the speed of light;
calculating an error Wc-d 2/v between the actual measurement time t and the theoretical measurement time t' at the preset measurement angle;
fitting the error W by least squaresCEquation W relating signal intensity tl of reflected laser beam to said actual distance dCF (tl, d), wherein the signal intensity tl of the reflected laser beam changes along with the change of the included angle between the reflector and the laser beam;
and acquiring a relation equation f (tl, d) of an actual distance d between the laser radar and the measuring point on the reflecting plate, the signal intensity tl of the reflected laser beam and the actual measuring time t at the preset measuring angle, wherein the relation equation f (tl, d) is t-d × 2/v.
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