CN109375183B - Missile-borne distance high-resolution radar high-precision dynamic distance calibration system and method - Google Patents

Abstract

The invention discloses a system and a method for calibrating dynamic distance of a quantitative high-speed missile-borne distance high-resolution radar, wherein the system comprises a mobile station, a mobile station GPS antenna, a mobile station radio antenna, a reference station GPS antenna, a reference station radio antenna, a target machine, a guide system, a time service system, a GPS time service antenna, a two-dimensional rotary table, an auxiliary control system and a missile-borne radar (12) to be tested. Wherein, the mobile station GPS antenna and the mobile station radio antenna are all arranged on the target machine; the system comprises a reference station, a reference station GPS antenna, a reference station radio antenna, a guide system, a time service system, a GPS time service antenna, a two-dimensional turntable and an auxiliary control system, wherein the reference station, the reference station GPS antenna, the reference station radio antenna, the guide system, the time service system, the GPS time service antenna, the two-dimensional turntable and the auxiliary control system are connected through a cable and are placed at one position, and the missile-borne radar to be detected is fixed on the two-dimensional turntable and the auxiliary control system. The invention has the advantages that: the method is simple to realize, and has the advantages of simple and convenient operation, high dynamic distance calibration precision and the like by depending on the system to implement the high-precision dynamic distance calibration of the missile-borne distance high-resolution radar.

Description

A high-precision dynamic range calibration system and method for missile-borne range high-resolution radar

technical field

The invention relates to a distance calibration system and method for missile-borne radar, in particular to a high-precision dynamic distance calibration system and method for missile-borne distance high-resolution radar.

Background technique

The traditional radar distance calibration methods are ground-based static distance calibration. This method can effectively calibrate the static distance system error of the radar, but for the high-speed missile-borne range high-resolution radar, the radar needs to give a certain The distance measurement value at a specified time, so the dynamic distance measurement accuracy is the real concern of the system. To calibrate the time-related distance measurement system error, the static distance calibration system cannot be implemented, so a high-precision dynamic distance calibration system is required to complete the calibration of the missile-borne range high-resolution radar dynamic distance measurement system error.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high-precision dynamic distance calibration system and method for a missile-borne range high-resolution radar, so as to solve the problem that the static distance calibration system cannot calibrate the error of the distance measurement system.

In order to solve the above technical problems, the present invention provides a high-precision dynamic distance calibration system for missile-borne high-resolution radar, which is characterized by comprising: a mobile station, a mobile station GPS antenna, a mobile station radio antenna, a reference station, and a reference station GPS Antenna, base station radio antenna, target aircraft, guidance system, timing system, GPS timing antenna, two-dimensional turntable and auxiliary control system, missile-borne radar to be tested;

The mobile station, mobile station GPS antenna, mobile station radio antenna are all installed on the target machine; base station, base station GPS antenna, base station radio antenna, guidance system, timing system, GPS timing antenna, two-dimensional turntable and auxiliary control system It is placed in one place through a cable connection, and the missile-borne radar to be tested is fixed on the two-dimensional turntable and the auxiliary control system. The mobile station, the mobile station GPS antenna, the mobile station radio antenna, the base station, the base station GPS antenna, and the base station radio antenna constitute a dual-station real-time differential GPS system.

Another object of the present invention is to provide a high-precision dynamic distance calibration method for a missile-borne high-resolution radar, including:

In the first step, the static distance calibration method is used to obtain the static distance measurement system error Δd, and Δd is compensated into the radar ranging algorithm to be measured;

The second step is to calibrate the initial heading angle, pitch angle, and GPS coordinates of the two-dimensional turntable and its auxiliary control system;

The third step is the timing of the dynamic distance calibration system

The GPS timing antenna 10 is connected with the timing system 9, the timing system is turned on, and after the GPS time is locked, the GPS time and GPS second pulses are output to the outside; the guidance system 8, the two-dimensional turntable and the auxiliary control system 11 are respectively connected with the timing system 9 Connect and power on, start the synchronization and calibration of GPS time;

The fourth step is dynamic distance calibration

Put the missile-borne radar system to be tested in the working state; set the rotation speed of the two-dimensional turntable and the auxiliary control system, and make it work in the external guidance mode; the target aircraft 7 flies according to the designed route and speed;

The fifth step of data processing

The GPS coordinates of the target aircraft with GPS time information can be obtained from the mobile station 1. Combined with the known GPS coordinates of the missile-borne radar, the absolute distance D _n of each target's GPS coordinate point relative to the missile-borne radar to be tested can be obtained by calculation. and relative velocity V _n , the test file recorded by the radar to be tested has the missile-borne radar measurement distance D _m with GPS time stamp, and the absolute distance and radar test distance under the same GPS time stamp can be obtained by aligning the GPS time stamp, and calculate From the ranging error ΔD _n , the average ranging error ΔD _a and the average relative velocity V _a can be obtained by calculating the average value, so Δt=ΔD _a /V _a can be obtained;

So far, the dynamic range calibration of the missile-borne radar 12 to be tested is completed.

The present invention achieves the following beneficial technical effects

Simple to implement, the system includes: mobile station, mobile station GPS antenna, mobile station radio antenna, base station, base station GPS antenna, base station radio antenna, target machine, guidance system, timing system, GPS timing antenna, two-dimensional turntable and accessories Control system, missile-borne radar to be tested. Relying on this system to implement high-precision dynamic range calibration of missile-borne range high-resolution radar has the advantages of simple operation and high dynamic range calibration accuracy.

Description of drawings

1 is a structural diagram of a high-precision dynamic range calibration system for a missile-borne range high-resolution radar according to the present invention;

FIG. 2 is a calibration timing diagram of the present invention.

reference numerals

1. Rover station 2. Rover station GPS antenna 3. Rover station radio antenna 4. Base station 5. Base station GPS antenna 6. Base station radio antenna 7. Target machine 8. Guidance system 9. Timing system 10. GPS timing antenna 11 .2D turntable and auxiliary control system 12. Missile-borne radar to be tested

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages and characteristics of the present invention will be more clearly understood from the following description and claims. It should be noted that, the accompanying drawings are all in a very simplified form and are all applied to inaccurate scales, and are only used to facilitate and clearly assist the purpose of explaining the embodiments of the present invention.

It should be noted that, in order to clearly illustrate the content of the present invention, the present invention provides multiple embodiments to further illustrate different implementations of the present invention, wherein the multiple embodiments are enumerated rather than exhaustive. In addition, for the sake of brevity of description, the content mentioned in the previous embodiment is often omitted in the latter embodiment, and therefore, the content not mentioned in the latter embodiment may refer to the former embodiment accordingly.

Although the invention can be expanded in various forms of modification and substitution, some specific embodiments are also listed and described in detail in the specification. It should be understood that it is not the intention of the inventor to limit the invention to the particular embodiments set forth, but on the contrary, the intention of the inventor is to protect all improvements, equivalent substitutions and modifications made within the spirit or scope defined by this statement of claims . The same part numbers may be used throughout the drawings to represent the same or similar parts.

Please refer to FIG. 1 , a high-precision dynamic distance calibration system of a missile-borne high-resolution radar of the present invention includes: a mobile station 1, a mobile station GPS antenna 2, a mobile station radio antenna 3, a reference station 4, and a reference station GPS antenna 5. Base station radio antenna 6, target aircraft 7, guidance system 8, timing system 9, GPS timing antenna 10, two-dimensional turntable and auxiliary control system 11, missile-borne radar to be tested 12;

The mobile station 1, mobile station GPS antenna 2, mobile station radio antenna 3 are all installed on the target machine 7; base station 4, base station GPS antenna 5, base station radio antenna 6, guidance system 8, timing system 9, GPS The timing antenna 10 , the two-dimensional turntable and the auxiliary control system 11 are connected to one place by a cable, and the missile-borne radar 12 to be tested is fixed on the two-dimensional turntable and the auxiliary control system 11 . Mobile station 1, mobile station GPS antenna 2, mobile station radio antenna 3, base station 4, base station GPS antenna 5, base station radio antenna 6 constitute a dual-station real-time differential GPS system.

In one embodiment, the timing system 9 is based on GPS time.

The present invention also provides a high-precision dynamic range calibration method for the missile-borne range high-resolution radar, including:

In the first step, the static distance calibration method is used to obtain the static distance measurement system error Δd, and Δd is compensated into the radar ranging algorithm to be measured;

The second step is to calibrate the initial heading angle, pitch angle, and GPS coordinates of the two-dimensional turntable and its auxiliary control system;

The third step is the timing of the dynamic distance calibration system

The GPS timing antenna 10 is connected with the timing system 9, the timing system is turned on, and after the GPS time is locked, the GPS time and GPS second pulses are output to the outside; the guidance system 8, the two-dimensional turntable and the auxiliary control system 11 are respectively connected with the timing system 9 Connect and power on, start the synchronization and calibration of GPS time;

The fourth step is dynamic distance calibration

Put the missile-borne radar system to be tested in the working state; set the rotation speed of the two-dimensional turntable and the auxiliary control system, and make it work in the external guidance mode; the target aircraft 7 flies according to the designed route and speed;

The fifth step of data processing

The GPS coordinates of the target aircraft with GPS time information can be obtained from the mobile station 1. Combined with the known GPS coordinates of the missile-borne radar, the absolute distance D _n of each target's GPS coordinate point relative to the missile-borne radar to be tested can be obtained by calculation. and relative velocity V _n , the test file recorded by the radar to be tested has the missile-borne radar measurement distance D _m with GPS time stamp, and the absolute distance and radar test distance under the same GPS time stamp can be obtained by aligning the GPS time stamp, and calculate From the ranging error ΔD _n , the average ranging error ΔD _a and the average relative velocity V _a can be obtained by calculating the average value, so Δt=ΔD _a /V _a can be obtained;

So far, the dynamic range calibration of the missile-borne radar 12 to be tested is completed.

In one embodiment, the obtaining the static distance measurement system error Δd by using the static distance calibration method further includes: compensating Δd into the radar ranging algorithm to be measured.

In one embodiment, the initial heading angle, pitch angle, and GPS coordinate calibration of the two-dimensional turntable and the auxiliary control system includes: placing the GPS antenna 5 of the reference station at the center of the antenna of the missile-borne radar 12 to be measured.

In one embodiment, the initial heading angle, pitch angle, and GPS coordinate calibration of the two-dimensional turntable and the auxiliary control system further include: setting the reference station 4 to work in an average positioning state, and obtaining accurate bombs to be tested through long-term observation The GPS coordinates of the on-board radar are calculated using the GPS coordinates of the missile-borne radar to be tested and the GPS coordinates of the entry point of the designed target aircraft route to obtain the initial heading angle θ and pitch angle φ.

In one embodiment, the initial heading angle, pitch angle, and GPS coordinate calibration of the two-dimensional turntable and the auxiliary control system further includes: presetting the two-dimensional turntable and the auxiliary control system to the calculated heading angle θ and pitch angle φ.

In one embodiment, the calibration of the initial heading angle, pitch angle, and GPS coordinates of the two-dimensional turntable and the auxiliary control system further includes: setting the parameters of the guidance system: GPS coordinates of the missile-borne radar to be measured.

In one embodiment, the missile-borne radar system to be tested is placed in the working state; the rotational speed of the two-dimensional turntable and the auxiliary control system is set, and it is made to work in the external guidance mode; the target aircraft 7 is carried out according to the designed route and speed Flying includes: when the target aircraft enters the effective working range of the radar to be tested, the missile-borne radar to be tested is in a transmitting working state, and the test file is recorded. When the target aircraft exits the effective working range of the radar to be tested, the radar ends its work.

In one embodiment, the data processing step further includes: causing the target machine 7 to perform dynamic distance calibration multiple times at different speeds, and averaging the obtained Δt to obtain a distance calibration result.

In one embodiment, for the high-speed missile-borne range high-resolution radar, the ranging error is mainly affected by two aspects, one is the time-independent ranging system error, denoted as Δd, and the other is the time-dependent ranging The systematic error is Δt×V, where V is the relative speed. Δd can be obtained through the static distance calibration method, and Δt can be obtained through the high-precision dynamic distance calibration system of the present invention.

ΔD=Δt×V+Δd

1. System plan

In one embodiment, a system and method for quantitative high-speed missile-borne distance high-resolution radar dynamic distance calibration, comprising a mobile station 1, a mobile station GPS antenna 2, a mobile station radio antenna 3, a reference station 4, and a reference station GPS antenna 5 , base station radio antenna 6 , target aircraft 7 , guidance system 8 , timing system 9 , GPS timing antenna 10 , two-dimensional turntable and auxiliary control system 11 , and missile-borne radar to be tested 12 . The mobile station 1, mobile station GPS antenna 2, mobile station radio antenna 3 are all installed on the target machine 7; base station 4, base station GPS antenna 5, base station radio antenna 6, guidance system 8, timing system 9, GPS timing The antenna 10 , the two-dimensional turntable and the auxiliary control system 11 are connected by cables and placed in one place, and the missile-borne radar 12 to be tested is fixed on the two-dimensional turntable and the auxiliary control system 11 .

In one embodiment, the mobile station 1 , the mobile station GPS antenna 2 , the mobile station radio antenna 3 , the reference station 4 , the base station GPS antenna 5 , and the base station radio antenna 6 constitute a dual-station real-time differential GPS system. It can output the differential GPS coordinate position of the target machine in real time to the outside world.

In one embodiment, the guidance system 8 can receive the target GPS coordinate position information output by the reference station 4 in real time, and calculate with the known GPS coordinate position of the missile-borne radar 12 to be tested, and output guidance information, the guidance information includes the target The azimuth angle θ and the pitch angle φ of the aircraft 7 in the coordinate system of the missile-borne radar 12 to be tested, as well as the distance D and the relative velocity V.

In one embodiment, the two-dimensional turntable and the auxiliary control system 11 can receive the guidance information in real time and control the azimuth and pitch angles.

The timing system 9 is connected with the GPS timing antenna 10 to provide high-precision time alignment for the entire system.

2. High-precision time alignment

In one embodiment, in the whole process of dynamic range calibration, in order to ensure that the missile-borne radar 12 to be tested can stably intercept the target, a high-precision requirement is put forward for the guidance system; in the post-test data processing, it is necessary to compare a certain The absolute distance and measurement distance of the moment also put forward high-precision requirements for the alignment of the moment. The whole system takes GPS time as the time reference, and the timing system 9 outputs the GPS time and GPS second pulse in a unified manner to jointly provide ns-level time alignment service. When recording data, both the guidance system 8 and the missile-borne radar 12 to be tested simultaneously record the time stamp calibrated by the timing system, and the time stamp is accurate to 1 ms. Mobile station 1 and reference station 2 also use GPS time as a reference when recording data, and the recording time stamp is accurate to 1ms.

3. System Accuracy Analysis

Referring to FIG. 2 , the accuracy of the high-precision dynamic distance calibration system is mainly affected by the GPS accuracy. The base station and mobile station use L1 and L2 dual-frequency GPS receivers, and the accuracy in real-time differential mode is not greater than 0.01m+1ppm (CEP); the speed measurement accuracy of the mobile station is not greater than 0.03m/s (RMS); GPS update rate is 20Hz .

In one embodiment, the time when the GPS of the target aircraft is acquired is t1, the time when the reference station receives the GPS information of the target aircraft is t2, the time t3 when the guidance computer calculates the guidance information, and the missile-borne radar (12) to be tested measures the distance of the target aircraft The time is t4. t2-t1 is recorded as the target GPS delay time Δt1; t3-t2 is the internal delay of the guidance system, recorded as Δt2; t4-t3 is the delay time of the missile-borne radar control system to be tested, recorded as Δt3. In the real-time differential GPS system, Δt1 is a fixed value, Δt2 and Δt3 can be obtained by calculating the time stamp in the record file, and the accuracy can reach 1ms. For a missile-borne radar system with a narrow beam width, the position of the target aircraft at t4 can be calculated by compensating Δt1+Δt2+Δt3 in the guidance system, and then the guidance information can be calculated to ensure that the missile-borne radar to be tested can stably track the target. machine.

In one embodiment, after the dynamic distance calibration is completed, the absolute distance at a certain moment can be calculated by using the GPS position of the target machine and the known GPS position of the missile-borne radar to be measured. The absolute distance accuracy is mainly affected by the GPS accuracy. In the high-precision dynamic distance calibration system of the present invention, the absolute distance accuracy is not greater than 2m.

Fourth, the specific operation process

The first step of static distance calibration

Using the static distance calibration method, the static distance measurement system error Δd is obtained, and Δd is compensated into the radar ranging algorithm to be measured.

The second step is to calibrate the initial heading angle, pitch angle, and GPS coordinates of the two-dimensional turntable and its auxiliary control system.

The GPS antenna 5 of the reference station is placed at the center of the antenna of the missile-borne radar 12 to be tested.

The reference station 4 is set to work in the average positioning state, and the accurate GPS coordinates of the missile-borne radar to be measured are obtained through long-term observation. Using the GPS coordinates of the missile-borne radar to be tested and the GPS coordinates of the entry point of the designed target aircraft route, the initial heading angle θ and pitch angle φ are calculated.

Preset the 2D turntable and auxiliary control system to the calculated heading angle θ and pitch angle φ.

Set the guidance system parameters: GPS coordinates of the missile-borne radar to be tested.

The third step is the timing of the dynamic distance calibration system

The GPS timing antenna 10 is connected to the timing system 9, the timing system is turned on, and after the GPS time is locked, the GPS time and GPS second pulses are output to the outside. The guidance system 8 , the two-dimensional turntable and the auxiliary control system 11 are respectively connected to the timing system 9 and turned on to start the synchronization and calibration of the GPS time.

The fourth step is dynamic distance calibration

Put the missile-borne radar system to be tested in the working state; set the rotation speed of the two-dimensional turntable and the auxiliary control system, and make it work in the external guidance mode; the target aircraft 7 flies according to the designed route and speed; wait for the target aircraft to enter the test When the radar is within the effective working distance, the missile-borne radar to be tested is in the launching working state, and the test file is recorded. When the target aircraft exits the effective working range of the radar to be tested, the radar stops working.

The fifth step of data processing

The GPS coordinates of the target aircraft with GPS time information can be obtained from the mobile station 1. Combined with the known GPS coordinates of the missile-borne radar, the absolute distance between the GPS coordinate points of each target aircraft and the missile-borne radar to be measured can be calculated. _Dn and relative velocity _Vn . The test file recorded by the radar to be tested has the measurement distance D _m with the GPS time stamp. By aligning the GPS time stamp, the absolute distance and the test distance under the same GPS time stamp can be obtained, and the ranging error ΔD _n can be calculated. The average ranging error ΔD _a and the average relative velocity Va can be obtained by calculating the average value, and thus Δt ₌ ΔD _a /V _a can be obtained.

In order to ensure the accuracy of dynamic distance calibration, the target machine 7 performs dynamic distance calibration multiple times at different speeds, and averages the obtained Δt to obtain a more accurate distance calibration result.

So far, the dynamic range calibration of the missile-borne radar 12 to be tested is completed.

The present invention achieves the following beneficial technical effects

Simple to implement, the system includes: mobile station, mobile station GPS antenna, mobile station radio antenna, base station, base station GPS antenna, base station radio antenna, target machine, guidance system, timing system, GPS timing antenna, two-dimensional turntable and accessories Control system, missile-borne radar to be tested. Relying on this system to implement high-precision dynamic range calibration of missile-borne range high-resolution radar has the advantages of simple operation and high dynamic range calibration accuracy.

According to the technical solution and concept of the present invention, any other suitable modifications can also be made. For those of ordinary skill in the art, all these replacements, adjustments and improvements should fall within the protection scope of the appended claims of the present invention.

Claims (8)

1. a bomb-borne distance high-resolution radar high-precision dynamic distance calibration method is characterized in that, comprising: The first step is to use the static distance calibration method to obtain the static distance measurement system error Δd, and compensate Δd to the radar ranging algorithm to be measured; The second step is to calibrate the initial heading angle, pitch angle, and GPS coordinates of the two-dimensional turntable and its auxiliary control system; The third step is the timing of the dynamic distance calibration system The dynamic distance calibration system comprises: a mobile station (1), a mobile station GPS antenna (2), a mobile station radio antenna (3), a reference station (4), a reference station GPS antenna (5), a reference station radio antenna ( 6), target aircraft (7), guidance system (8), timing system (9), GPS timing antenna (10), two-dimensional turntable and auxiliary control system (11), missile-borne radar to be tested (12); The mobile station (1), the mobile station GPS antenna (2), and the mobile station radio antenna (3) are all installed on the target machine (7); the base station (4), the base station GPS antenna (5), the base station radio The antenna (6), the guidance system (8), the timing system (9), the GPS timing antenna (10), the two-dimensional turntable and the auxiliary control system (11) are connected by cables and placed in one place, and the missile-borne radar to be tested (12) is fixed On the two-dimensional turntable and the auxiliary control system (11), the mobile station (1), the mobile station GPS antenna (2), the mobile station radio antenna (3), the reference station (4), the reference station GPS antenna (5), the reference station The station radio antenna (6) constitutes a dual-station real-time differential GPS system; Connect the GPS timing antenna (10) to the timing system (9), turn on the timing system, and start outputting GPS time and GPS second pulses after the GPS time is locked; connect the guidance system (8), the two-dimensional turntable and the auxiliary control system (11) are respectively connected to the timing system (9) and start up to start synchronization and calibration of GPS time; Step 4 Dynamic distance calibration Put the missile-borne radar system to be tested in the working state; set the rotational speed of the two-dimensional turntable and the auxiliary control system, and make it work in the external guidance mode; the target aircraft (7) flies according to the designed route and speed; The fifth step data processing Obtain the GPS coordinates of the target aircraft with GPS time information from the mobile station (1). Combined with the known GPS coordinates of the missile-borne radar, the absolute distance D of each target's GPS coordinate point relative to the missile-borne radar to be tested is calculated. _n and relative velocity V _n , the test file recorded by the radar to be tested has the missile-borne radar measurement distance D _m with the GPS time stamp, and the absolute distance and the radar test distance under the same GPS time stamp are obtained by aligning the GPS time stamp, and calculate The ranging error ΔD _n is obtained, and the average ranging error ΔD _a and the average relative velocity V _a are obtained by calculating the average value, thus obtaining Δt=ΔD _a /V _a ; So far, the dynamic range calibration of the missile-borne radar (12) to be tested is completed. 2. The high-precision dynamic distance calibration method for high-resolution radar on a missile-borne distance according to claim 1, wherein said adopting the static distance calibration method to obtain the static distance measurement system error Δd also comprises: compensating Δd to In the radar ranging algorithm to be measured. 3. bomb-borne distance high-resolution radar high-precision dynamic distance calibration method according to claim 1, is characterized in that, described two-dimensional turntable and auxiliary control system initial heading angle, pitch angle, GPS coordinate calibration comprise: The station GPS antenna (5) is placed at the center of the antenna of the missile-borne radar (12) to be tested. 4. bomb-borne distance high-resolution radar high-precision dynamic distance calibration method according to claim 3, is characterized in that, described two-dimensional turntable and auxiliary control system initial heading angle, pitch angle, GPS coordinate calibration also comprise: setting The base station (4) works in the state of average positioning, obtains the accurate GPS coordinates of the missile-borne radar to be tested through long-term observation, and uses the GPS coordinates of the missile-borne radar to be tested and the GPS coordinates of the designed target aircraft route entry point to calculate the initial Heading angle θ, pitch angle φ. 5. bomb-borne distance high-resolution radar high-precision dynamic distance calibration method according to claim 4, is characterized in that, described two-dimensional turntable and auxiliary control system initial heading angle, pitch angle, GPS coordinate calibration also comprise: The 2D turntable and its auxiliary control system are preset to the calculated heading angle θ and pitch angle φ. 6. bomb-borne distance high-resolution radar high-precision dynamic distance calibration method according to claim 5, is characterized in that, described two-dimensional turntable and auxiliary control system initial heading angle, pitch angle, GPS coordinate calibration also comprise: setting Guidance system parameters: GPS coordinates of the missile-borne radar to be tested. 7. bomb-borne distance high-resolution radar high-precision dynamic distance calibration method according to claim 1, is characterized in that, the described bomb-borne radar system to be tested is placed in working state; two-dimensional turntable and auxiliary control system rotational speed are set , and make it work in the external guidance mode; the target aircraft (7) flies according to the designed route and speed, including: when the target aircraft enters the effective working range of the radar to be tested, the missile-borne radar to be tested is in a launching working state , and record the test file. When the target aircraft exits the effective working distance of the radar to be tested, the radar ends its work. 8. bomb-borne distance high-resolution radar high-precision dynamic distance calibration method according to claim 7, is characterized in that, described data processing step also comprises: make target machine (7) carry out dynamic distance multiple times under different speeds Calibration, average the obtained Δt to obtain the distance calibration result.

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