CN116660844A - Calibration tool and calibration method for vehicle-mounted millimeter wave radar antenna - Google Patents
Calibration tool and calibration method for vehicle-mounted millimeter wave radar antenna Download PDFInfo
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- CN116660844A CN116660844A CN202310471910.7A CN202310471910A CN116660844A CN 116660844 A CN116660844 A CN 116660844A CN 202310471910 A CN202310471910 A CN 202310471910A CN 116660844 A CN116660844 A CN 116660844A
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Classifications
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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
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/40—Means for monitoring or calibrating
- G01S7/4004—Means for monitoring or calibrating of parts of a radar system
- G01S7/4039—Means for monitoring or calibrating of parts of a radar system of sensor or antenna obstruction, e.g. dirt- or ice-coating
- G01S7/4043—Means for monitoring or calibrating of parts of a radar system of sensor or antenna obstruction, e.g. dirt- or ice-coating including means to prevent or remove the obstruction
Abstract
The invention relates to the technical field of vehicle-mounted radars, in particular to a calibration tool and a calibration method for a vehicle-mounted millimeter wave radar antenna. Triggering type sending single-frame FMCW waveform is carried out by receiving an angle information message sent by an upper computer; the angle of the calibration tool is reversely moved to the position of-75 degrees of the radar by sending a motor driving command through the calibration upper computer; enabling the radar to send a frame of FMCW waveform and uploading 2DFFT message information at a fixed distance in the frame of waveform; the calibration upper computer receives and stores the 2DFFT information and drives the radar to step to the next positive direction angle; the calibration upper computer calculates DBF factors through the collected 151 groups of 2DFFT data; the calibration upper computer sends the calculated DBF factor to the radar, the radar lower computer receives and stores the calibration information, the influence of the automobile rear protection covering piece on the radar angle measurement performance can be reduced under certain conditions, the angle precision attenuation caused by the covering piece factors after the radar is installed can be greatly reduced, and higher angle measurement precision can be achieved after calibration.
Description
Technical Field
The invention belongs to the technical field of vehicle-mounted radars, and particularly relates to a calibration tool and a calibration method for a vehicle-mounted millimeter wave radar antenna.
Background
When the millimeter wave radar is used as a vehicle-mounted part, most of the millimeter wave radar is installed below a front protection/rear protection covering piece due to stealth and aesthetic considerations, and the factors such as the structural thickness, the structural morphology, the external paint material and the like of the covering piece can negatively influence the performance of the millimeter wave radar.
The existing radar antenna calibration method calibrates the radar antenna based on the production line environment, can only reduce the influence of the radar radome on the antenna performance, and cannot reduce the influence of the automobile outer shell covering part on the radar antenna performance.
Disclosure of Invention
Aiming at the problems, the invention provides a calibration tool and a calibration method for a vehicle millimeter wave radar antenna. The negative influence of the rear protection cover on the radar performance is reduced, and the angle precision attenuation caused by the cover factors after the radar is installed can be greatly reduced.
The invention provides a calibration tool for a vehicle millimeter wave radar antenna, which comprises the following components: the fixing part comprises a base and a rotating shaft rotatably arranged at the center of the base through a bearing; the moving part comprises a moving trolley, an angle reverser arranged at the top of the moving trolley through a bracket and a driving part arranged at the bottom of the moving trolley; and the two ends of the steel column connector are respectively connected with the upper end of the rotating shaft and the edge of the movable trolley.
Preferably, the reflecting surface of the corner reflector faces in the same direction as the extension direction of the steel cylinder connector.
Preferably, the driving unit includes: a stepping motor arranged at the bottom of the mobile trolley; and a programmable controller connected to the stepper motor; the output shaft of the stepping motor is connected with the moving wheel of the moving trolley, and the programmable controller is arranged at the top of the moving trolley.
Preferably, the bottom of the base is provided with an adjustable foot margin.
On the other hand, the invention provides a calibration method of a vehicle millimeter wave radar antenna, which comprises the following steps:
s1, installing a radar below a covering part in a corresponding position of an automobile, and finding a projection point of the radar on the ground by using a perpendicular method and marking the projection point before the covering part is assembled;
s2, placing the base at a mark point, adjusting a rotating shaft, positioning the rotating shaft on a straight line between the radar and a ground projection point, fixing the base, and connecting the base with a mobile trolley through a steel column connector;
s3, starting the radar, and establishing connection between the radar and the PC as well as connection between the programmable controller and the PC;
s4, the PC controls the radar lower computer to enter a one-degree one-calibration mode through the calibration upper computer;
s5, sending a motor driving command to move the angle reverser to the position of-75 degrees of the radar through the calibration upper computer;
s6, the calibration upper computer sends a waveform trigger message to the radar, so that the radar sends a frame of FMCW waveform and uploads 2DFFT message information at a fixed distance in the frame of waveform;
s7, receiving and storing the 2DFFT information through the calibration upper computer, driving the radar to step to the next positive direction angle, and repeating the steps S6 and S7 until the angle reverser moves to the position of +75 degrees of the radar and uploading the 2DFFT information under the angle;
s8, calculating DBF factors by the calibration upper computer through the collected multiple groups of 2DFFT data;
s9, the calibration upper computer sends the calculated DBF factor to the radar, and the radar lower computer receives and stores the calibration information;
s10, calibration is completed.
Preferably, the starting the radar, establishing a connection between the radar and the PC, and between the programmable controller and the PC, includes: the PC is connected with the programmable controller through the RS-485 serial port module; the PC is connected with the radar through a USB-CAN conversion tool.
Preferably, the PC controls the radar lower computer to enter a one-degree calibration mode through the calibration upper computer, including: the PC transfers the USB-CAN tool to send CAN message through the calibration upper computer, controls the radar lower computer to enter a one-time calibration mode, namely, the single-frame FMCW waveform is triggered and sent through receiving the angle information message sent by the PC, and the radar sends one-frame FMCW waveform every time the CAN message sent by the PC is received.
Preferably, the sending, by the calibration upper computer, a motor driving command to move the angle reverser to the position of-75 degrees of the radar includes: the PC upper computer controls the calibration upper computer to send a motor driving command by calling the RS-485 module; the programmable controller receives the driving command and controls the stepping motor to drive the mobile trolley to move the angle reverser to the position of-75 degrees of the radar.
Preferably, the fixed distance is the radial distance between the angular inverse and the radar, and the information is the radar waveform information processing result after AD extraction and distance dimension and speed dimension twice FFT conversion of an intermediate frequency signal generated by mixing a transmitting waveform and a receiving waveform.
The beneficial effects of the invention are as follows:
the invention provides a calibration tool which mainly comprises a fixed part, a moving part, a steel column connector and other parts, wherein the radar is arranged below a covering part in a corresponding position of an automobile, a projection point of the radar on the ground is found by using a vertical method before the covering part is assembled and marked, a base is placed at the marking point, a rotating shaft is adjusted, the rotating shaft is positioned on a straight line of the radar and the projection point on the ground, the base is fixed, the radar is connected with a mobile trolley through the steel column connector, the radar is started, the connection between the radar and a PC and a programmable controller and the PC is established, the PC controls a radar lower computer to enter a one-degree calibration mode through a calibration upper computer, the angle counter is moved to the position of-75 degrees of the radar through a motor driving command sent by the calibration upper computer, the radar is triggered by the calibration upper computer, the radar is enabled to send a frame of FMCW waveform, 2DFFT message information at a fixed distance position in the frame of the radar is uploaded, the radar is received and stored through the calibration upper computer, the radar is driven to a next positive angle, the radar is enabled to reach a next calibration factor is calculated through the calibration upper computer, and the accuracy factor can be reduced after the DBF is calibrated by the covering part is installed, and the accuracy factor can be greatly reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 shows a schematic structural diagram of a calibration tool for a vehicle millimeter wave radar antenna in an embodiment of the invention;
fig. 2 is a flowchart of a calibration method of a vehicle millimeter wave radar antenna according to an embodiment of the present invention;
FIG. 3 shows a schematic diagram of one of the angle measurement principles of the prior art;
fig. 4 shows a schematic diagram of a second prior art angle measurement principle.
In the figure:
100. a fixing part; 101. a base; 102. a rotating shaft; 103. an adjustable foot margin;
200. a moving part; 201. a moving trolley; 202. an angle reverser; 203. a stepping motor; 204. a programmable controller; 205. a bracket;
300. a steel column connector.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention provides a calibration tool for a vehicle millimeter wave radar antenna, which aims to reduce the influence of a rear protection cover piece of an automobile on the radar angle measurement performance under certain conditions.
Referring to fig. 1, fig. 1 shows a schematic structural diagram of a calibration tool for a vehicle millimeter wave radar antenna according to an embodiment of the invention.
In this embodiment, the calibration fixture includes a fixed portion 100, a movable portion 200, and a steel column connector 300. The fixing portion 100 is used for being fixed on the ground, and the steel cylinder connector 300 is used for combining the moving portion 200 and the fixing portion 100, so that the moving portion 200 can rotate around the fixing portion 100 as a center. Specifically, the following is described.
Illustratively, the fixing part 100 includes a base 101 and a rotating shaft 102 rotatably installed at the center of the base 101 through a bearing.
It will be appreciated that the top of the base 101 is provided with a mounting groove for fixedly mounting the bearing, and the shaft 102 is fixed in the inner ring of the bearing so that the shaft 102 can rotate. The bottom of the base 101 is provided with an adjustable foot 103 for fixing the base 101 to the ground and adjusting the level of the base 101.
It should be noted that the rotation shaft 102 should be kept perpendicular to the ground, so as to facilitate the movement of the moving portion 200.
Illustratively, the moving part 200 includes a moving carriage 201, an angle reverser 202 mounted on the top of the moving carriage 201 through a bracket 205, and a driving part mounted on the bottom of the moving carriage 201.
The travelling car 201 is composed of a frame and wheels, wherein the wheels are arranged in three groups to form triangular distribution. One set is a drive wheel, which is connected to a stepper motor 203. The other two groups are driven wheels. The bracket 205 is used for supporting the angle reflector 202, and the height of the angle reflector 202 can be adjusted according to actual needs for reflecting radar signals.
Specifically, the driving section includes: a stepping motor 203 installed at the bottom of the moving cart 201; and a programmable controller 204 coupled to the stepper motor 203.
Wherein, the output shaft of the step motor 203 is connected with the moving wheel of the moving trolley 201, and the programmable controller 204 is installed on the top of the moving trolley 201. The programmable controller 204 is used as a controller of the stepping motor 203 and is used for controlling the stepping motor 203 to drive the driving wheel to drive the trolley to move at a specified angle.
It should be noted that the reflecting surface of the corner reflector 202 faces in the same direction as the extending direction of the steel cylinder connector 300, which is beneficial to signal reflection.
For example, the steel column connector 300 may be made of steel pipes, steel bars or other hard materials, and the length thereof may be set according to actual needs, which will not be described herein.
It should be noted that, the two ends of the steel cylinder connector 300 are respectively connected to the upper end of the rotating shaft 102 and the side of the moving trolley 201 through bolts, so as to maintain the stability of the three components and facilitate the disassembly and assembly.
In addition, based on the calibration tool, the calibration method of the vehicle millimeter wave radar antenna is provided.
The calibration method will be described in detail, and the millimeter wave radar workflow, the millimeter wave radar angle measurement principle and the angle measurement principle need to be described before the description, as follows.
As known from the prior art, the millimeter wave radar work flow is as follows:
TX antenna transmitting FMCW waveforms
An RX antenna receives and transmits echo signals to a baseband
3. The baseband performs mixing operation to generate intermediate frequency signals and ADC data in a sampling mode
4. The signal processing module starts to work and converts the ADC data into 2DFFT data by performing FFT calculation in the distance dimension and the speed dimension
5. Screening 2DFFT data peak value by constant false alarm detection (CFAR) to output original trace peak value list
6. Calculating angle information corresponding to the initial point trace by DBF solution angle mode
7. Calculating the real speed information of the original point trace by a speed solution fuzzy algorithm
8. Outputting raw data point cloud information
9. And performing application layer processing.
It should be noted that the above flow is only briefly described, and the specific flow may refer to the prior art, which is not described herein again.
The prior art shows that the millimeter wave radar angle measurement principle is as follows:
FMCW radar systems use a horizontal plane to estimate the angle of the reflected signal, which is referred to as the angle of arrival (AoA).
When the target distance changes slightly, the phase at the Range-FFT peak changes greatly, so the phase change caused by the difference Δd between the object and the two antennas can be used to estimate the Angle of Arrival (Angle of Arrival).
As known from the prior art, the angle measurement principle is as follows:
a small change in target distance results in a phase change of the range-FFT peak. At least 2 RX antennas are required for angle estimation.
The differential distance Δd from the target to each antenna results in a phase change of the FFT peak, which is used to estimate the angle of arrival.
The relationship between the phase change and the distance is as follows:
assuming that the inter-antenna distance is d, Δd=lsin (θ), the arrival angle can be estimated as:
accuracy of estimation: since Δφ depends on sin (θ) and is a nonlinear dependency, the accuracy of angle estimation is high when θ approaches 0 °, and decreases when θ approaches 90 °.
Referring to fig. 2, fig. 2 is a flowchart illustrating a calibration method of an on-vehicle millimeter wave radar antenna according to an embodiment of the present invention.
In this embodiment, a calibration method for a vehicle millimeter wave radar antenna includes the following steps:
s1, installing a radar below a covering part in a corresponding position of an automobile, and finding a projection point of the radar on the ground by using a perpendicular method and marking the projection point before the covering part is assembled;
for example, for the search of the projection point, a laser pen may be used, the laser pen is installed at the center of a circular ring, the circular ring is lifted by a vertical line, then one end of the vertical line is fixed on the radar, and the laser point is marked as the projection point after the laser pen is stationary.
S2, placing the base 101 at a mark point, adjusting the rotating shaft 102, positioning the rotating shaft on the straight line of the radar and the ground projection point, fixing the base 101, and connecting the base 101 with the mobile trolley 201 through the steel column connector 300;
in particular, the steel cylinder connector 300 should be maintained horizontal while being installed, preventing the base 101 from tilting.
S3, starting the radar, and establishing connection between the radar and the PC as well as between the programmable controller 204 and the PC;
specifically, the PC is connected with the programmable controller 204 through an RS-485 serial port module (communication bus: serial port); the PC is connected with the radar through a USB-CAN conversion tool (communication bus: standard CAN bus).
S4, the PC controls the radar lower computer to enter a one-degree one-calibration mode through the calibration upper computer;
specifically, the PC invokes the USB-CAN tool through the calibration upper computer to send a CAN message, and controls the radar lower computer to enter a one-degree one-calibration mode, namely, the single-frame FMCW waveform is triggered and sent through receiving the angle information message sent by the PC, and the radar sends a frame FMCW waveform every time the CAN message sent by the PC is received.
S5, sending a motor driving command to move the angle reverser 202 to the position of-75 degrees of the radar through the calibration upper computer;
the method specifically comprises the following steps: the PC upper computer controls the calibration upper computer to send a motor driving command by calling the RS-485 module; the programmable controller 204 receives the driving command and controls the stepping motor 203 to drive the mobile trolley to move the angle reverser 202 to the position of-75 degrees of the radar.
S6, the calibration upper computer sends a waveform trigger message to the radar, so that the radar sends a frame of FMCW waveform and uploads 2DFFT message information at a fixed distance in the frame of waveform;
specifically, the fixed distance is the radial distance between the angular inverse and the radar, and the information is the radar waveform information processing result after AD extraction and distance dimension and speed dimension twice FFT conversion of an intermediate frequency signal generated by mixing a transmitting waveform and a receiving waveform.
S7, receiving and storing the 2DFFT information through the calibration upper computer, driving the radar to step to the next positive direction angle, and repeating the steps S6 and S7 until the angle reverser 202 moves to the position of +75 degrees of the radar and uploading the 2DFFT information under the angle;
s8, calculating DBF factors by the calibration upper computer through the collected multiple groups of 2DFFT data;
specifically, the DBF goniometer principle and the DBF calibration factor calculation method are as follows:
principle of: the basic idea of DBF (digital beam forming) is to weight and sum the received signals of the antenna elements, and the obtained maximum guiding position is the estimation of the direction of arrival of the target.
The implementation mode is as follows: when the millimeter wave radar receives the trigger signal, the rotation angle of the millimeter wave radar turntable has a certain deviation from the detection angle of the phase difference to be calibrated, and the accuracy of the phase calibration of the millimeter wave radar antenna array can be effectively improved by carrying out angle compensation on the angle deviation.
By acquiring phase values of the radar when detecting targets with different angles, a sin curve of the phase difference of the radar receiving array antenna and the angle change of the targets is fitted, the intercept is phase errors caused by coupling between feeder lines to be compensated and the inside of a radio frequency chip, and the amplitude divided by 2 pi is the antenna phase center (the value is a multiple of the wavelength) to be compensated.
Selecting one antenna of the millimeter wave radar as a reference antenna, wherein the other antennas are all antennas to be calibrated; firstly, extracting phase values of a reference antenna under different detection angles and phase values of a first antenna to be calibrated under different detection angles; secondly, for the same detection angle, the phase value of the antenna to be calibrated and the phase value of the reference antenna are subjected to difference, and the phase difference between the antenna to be calibrated and the reference antenna under the detection angle is obtained; and repeating the above process for the rest antennas to be calibrated, thereby obtaining the phase difference between each antenna to be calibrated and the reference antenna under different detection angles.
Determining a phase compensation coefficient according to the angle compensation result, the antenna phase center distance and the phase difference: Δω=2pi d p sin(θ+θ e )/λ+ω e ；
Wherein Δω is a phase difference, θ is a detection angle, θ e Is an angle compensation value, lambda is the wavelength of electromagnetic wave, omega e D is the phase compensation coefficient p Is the phase center-to-center spacing.
S9, the calibration upper computer sends the calculated DBF factor to the radar, and the radar lower computer receives and stores the calibration information;
s10, calibration is completed.
Furthermore, in other embodiments, the millimeter wave radar antenna calibration method may include the steps of: controlling a radar target simulator to simulate a target to be detected according to a preset target distance, speed and radar reflecting area; controlling a millimeter wave radar turntable to drive the millimeter wave radar to rotate at a uniform speed through a radar center rotating shaft, so that the targets to be detected are positioned at different detection angles of the millimeter wave radar; the cloud platform is controlled to send trigger signals under different detection angles so as to trigger the millimeter wave radar to send waveforms and acquire echo data of each antenna to be calibrated under different detection angles; acquiring instruction time delay of the cloud platform for sending the trigger signal under different detection angles; performing angle compensation on the detection angle of the millimeter wave radar according to the instruction time delay and the rotation angular speed of the millimeter wave radar; performing signal processing on the echo data to acquire phase information of each antenna channel to be calibrated in the echo data; acquiring phase compensation coefficients of the antenna channels to be calibrated according to the angle compensation result and the phase information; and carrying out phase compensation on each antenna to be calibrated according to the phase compensation coefficient.
The obtaining the phase compensation coefficient of each antenna channel to be calibrated according to the angle compensation result and the phase information comprises the following steps: determining a reference antenna and an antenna to be calibrated, and obtaining a phase value of the reference antenna and a phase value of each antenna to be calibrated; according to the phase values of the reference antenna and the phase values of the antennas to be calibrated, obtaining phase differences of the reference antenna and the antennas to be calibrated under different detection angles; and determining the phase compensation coefficient according to the angle compensation result and the phase difference.
The step of obtaining the instruction time delay of the cloud platform for sending the trigger signal under different detection angles comprises the following steps: when the millimeter wave radar turntable rotates to a first detection angle, controlling the cloud platform to send the trigger signal; acquiring a first time node of the cloud platform for sending the trigger signal; acquiring a second time node of the millimeter wave radar receiving the trigger signal; and determining the time interval of the first time node and the second time node as the instruction time delay.
The performing angle compensation on the detection angle of the millimeter wave radar according to the instruction time delay and the rotation angular speed of the millimeter wave radar comprises: acquiring an actual detection angle to which the millimeter wave radar turntable is currently rotated when the second time node is reached; determining an angle error between the first detected angle and the actual detected angle; and carrying out angle compensation on the first detection angle according to the angle error.
The step of performing signal processing on the echo data, and the step of obtaining phase information of each antenna channel to be calibrated in the echo data includes: performing two-dimensional fast Fourier transform on each echo data to obtain a signal spectrum of each echo data; determining the position of the target simulated by the target simulator in the signal spectrum according to the target distance and the target speed; and acquiring a phase value corresponding to the position to acquire the phase value of each antenna under each detection angle.
By taking a single-shot four-received millimeter wave angle radar as an example, the millimeter wave radar calibrated by the method can reach the following standard in angle measurement accuracy under the condition of the existence of a covering piece, as shown in table 1:
| a | angle-20 deg | RCS 5dBsm | Distance 50m | ±0.1deg |
| b | Angle 0deg | RCS 5dBsm | Distance 50m | ±0.1deg |
| c | Angle 10deg | RCS 5dBsm | Distance 50m | ±0.1deg |
| d | Angle 20deg | RCS 5dBsm | Distance 50m | ±0.1deg |
| e | Angle 40deg | RCS 5dBsm | Distance 50m | ±0.2deg |
| f | Angle 60deg | RCS 5dBsm | Distance 50m | ±0.3deg |
| g | Angle 70deg | RCS 5dBsm | Distance 50m | ±0.3deg |
| h | Angle 75deg | RCS 5dBsm | Distance 50m | ±0.3deg |
The standard can cover most of angle radar use scenes, and for the radar with more transmitting and receiving antennas, higher angle measurement precision can be achieved after the calibration, so that the method can be proved to have enough universality.
In summary, according to the invention, the radar is installed below the covering part in the corresponding position of the automobile, a projection point of the radar on the ground is found by using a vertical method and marked before the covering part is assembled, the base is placed at the marking point, the rotating shaft is adjusted, the base is positioned on a straight line of the radar and the projection point on the ground, the base is fixed, then the radar is connected with the mobile trolley through the steel column connector, the connection between the radar and the PC and between the programmable controller and the PC is started, the PC controls the radar lower computer to enter a one-degree calibration mode through the calibration upper computer, the calibration upper computer sends a motor driving command to move the angle inverter to the position of-75 degrees of the radar, the calibration upper computer triggers a message to the radar, the radar sends a frame FMCW waveform, the radar is uploaded with 2DFFT message information at a fixed distance in the frame waveform, the radar is received and stored through the calibration upper computer, the radar is driven to a next positive direction angle, the calibration upper computer calculates DBF factors through the acquired multiple groups of 2DFFT data, the calibration upper computer calculates the DBF factors, the accuracy of the radar is reduced, the accuracy of the radar can be greatly reduced, and the accuracy of the radar can be greatly reduced after the covering part is installed, and the accuracy of the radar can be greatly reduced after the accuracy is reached.
Although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. Calibration frock of on-vehicle millimeter wave radar antenna, its characterized in that includes:
the fixing part comprises a base and a rotating shaft rotatably arranged at the center of the base through a bearing;
the moving part comprises a moving trolley, an angle reverser arranged at the top of the moving trolley through a bracket and a driving part arranged at the bottom of the moving trolley; a kind of electronic device with high-pressure air-conditioning system
The steel column body connector, the both ends of steel column body connector are connected respectively the upper end of pivot with the limit portion of travelling car.
2. The calibration fixture for the vehicle millimeter wave radar antenna according to claim 1, wherein the reflecting surface of the angle reflector faces in the same direction as the extending direction of the steel cylinder connector.
3. The calibration fixture for an in-vehicle millimeter wave radar antenna according to claim 2, wherein the driving part comprises:
a stepping motor arranged at the bottom of the mobile trolley; a kind of electronic device with high-pressure air-conditioning system
A programmable controller connected to the stepper motor;
the output shaft of the stepping motor is connected with the moving wheel of the moving trolley, and the programmable controller is arranged at the top of the moving trolley.
4. The calibration fixture for the vehicle millimeter wave radar antenna according to claim 3, wherein adjustable feet are installed at the bottom of the base.
5. A method for calibrating a calibration fixture for a vehicle millimeter wave radar antenna according to any one of claims 1-4, comprising:
s1, installing a radar below a covering part in a corresponding position of an automobile, and finding a projection point of the radar on the ground by using a perpendicular method and marking the projection point before the covering part is assembled;
s2, placing the base at a mark point, adjusting a rotating shaft, positioning the rotating shaft on a straight line between the radar and a ground projection point, fixing the base, and connecting the base with a mobile trolley through a steel column connector;
s3, starting the radar, and establishing connection between the radar and the PC as well as connection between the programmable controller and the PC;
s4, the PC controls the radar lower computer to enter a one-degree one-calibration mode through the calibration upper computer;
s5, sending a motor driving command to move the angle reverser to the position of-75 degrees of the radar through the calibration upper computer;
s6, the calibration upper computer sends a waveform trigger message to the radar, so that the radar sends a frame of FMCW waveform and uploads 2DFFT message information at a fixed distance in the frame of waveform;
s7, receiving and storing the 2DFFT information through the calibration upper computer, and driving the radar to step to the next positive direction angle; repeating the steps S6 and S7 until the angle reverser moves to the position of +75 degrees of the radar and uploading 2DFFT information under the angle;
s8, calculating DBF factors by the calibration upper computer through the collected multiple groups of 2DFFT data;
s9, the calibration upper computer sends the calculated DBF factor to the radar, and the radar lower computer receives and stores the calibration information;
s10, calibration is completed.
6. The method for calibrating an antenna of a millimeter wave radar for vehicle according to claim 5, wherein said activating the radar to establish a connection between the radar and a PC, and between a programmable controller and the PC, comprises:
the PC is connected with the programmable controller through the RS-485 serial port module;
the PC is connected with the radar through a USB-CAN conversion tool.
7. The method for calibrating a millimeter wave radar antenna for a vehicle according to claim 6, wherein the step of controlling, by the PC, the radar lower computer to enter a one-degree one-calibration mode through the calibration upper computer comprises:
the PC transfers the USB-CAN tool to send CAN message through the calibration upper computer, controls the radar lower computer to enter a one-time calibration mode, namely, the single-frame FMCW waveform is triggered and sent through receiving the angle information message sent by the PC, and the radar sends one-frame FMCW waveform every time the CAN message sent by the PC is received.
8. The method for calibrating an antenna of a millimeter wave radar for vehicles according to claim 7, wherein said transmitting a motor driving command by said calibration upper computer moves an angle reverser to-75 degrees of said radar, comprises:
the PC upper computer controls the calibration upper computer to send a motor driving command by calling the RS-485 module;
the programmable controller receives the driving command and controls the stepping motor to drive the mobile trolley to move the angle reverser to the position of-75 degrees of the radar.
9. The method for calibrating a vehicle millimeter wave radar antenna according to claim 8, wherein the fixed distance is a radial distance between an angular inverse and a radar, and the information is a radar waveform information processing result obtained by performing AD extraction and distance dimension and speed dimension twice FFT conversion on an intermediate frequency signal generated by mixing a transmitting waveform and a receiving waveform.
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