CN103901413A - Three-coordinate radar height dynamic calibration equipment and method based on rotor unmanned helicopter - Google Patents

Abstract

The invention belongs to radar calibration equipment, and relates to three-coordinate radar height dynamic calibration equipment and a method thereof based on a rotor unmanned helicopter. The radar height dynamic calibration equipment comprises three Beidou receiver terminals, carrier-borne radar data recording equipment, a flight control system and a calculation and separation system; the three Beidou receiver terminals are respectively a first Beidou receiver which is arranged on a datum point of a wharf and used as a datum station, a second Beidou receiver which is arranged in a ship equivalent position center and a third Beidou receiver which is arranged in a rotor unmanned helicopter; during calibration, Beidou equipment is additionally arranged on the unmanned rotor helicopter and the naval vessel, the physical position changes of the unmanned rotor helicopter and the naval vessel are recorded, meanwhile, naval vessel radar recorded data are synchronously utilized, error processing analysis is carried out on the true value data recorded on the unmanned rotor helicopter and the naval vessel radar recorded data, and finally, a radar elevation error value is obtained.

Description

Three-coordinate radar height dynamic calibration equipment and method based on rotor unmanned helicopter

technical field

The invention belongs to a radar calibration device, in particular to a three-coordinate radar height dynamic calibration device based on a rotorless unmanned helicopter and a method thereof, which can solve the calibration problem of radar elevation angle accuracy.

Background technique

At present, domestic research on shipborne radar calibration is mainly focused on the direction of two-coordinate radar. Zhao Xin et al. proposed to use a zero calibration method based on the combination of differential GPS, CCD, laser theodolite and other technologies. The position accuracy of the calibration system is better than 50cm, and the angle accuracy It is better than 0.05mrad; Yao Jingshun et al. proposed to use GPS technology to dynamically calibrate the shipborne radar, and the target position accuracy reached 1m; Duan Jingxuan et al. proposed to use GPS RTK technology to dynamically calibrate the three-coordinate radar, and the distance calibration error was not greater than 4cm.

In addition to determining the azimuth and distance of the target, the three-coordinate radar can also measure the height of the target. Like all measuring devices, the radar's altitude measurement will have errors, which will seriously affect the use of the radar, and need to be calibrated to ensure the accuracy of the measured values. However, there is no specialized scientific research institution in China to conduct systematic research on the elevation angle calibration method of three-coordinate radar in active service on board. Airplanes, special helicopters, etc. The application procedure for using military aircraft is complicated, especially for the calibration after repair, the application is more difficult and the cost is high, and the GPS data on military aircraft is difficult to extract; the advantage of using balloons as calibration targets is that it can test 0-10000m various High detection accuracy, enough data can be obtained, and the use of balloons is also better than the use of military aircraft in terms of economy. However, using a balloon as a calibration target requires an air traffic control application. After the balloon is released, it is generally impossible to recover, and there are also potential safety hazards. The disadvantage of using civil aviation aircraft is that the target is a non-cooperative target, and it is easy to register the wrong number. Due to the uncontrollable route, the amount of data will be very small. to the accuracy requirements.

The invention uses the rotor unmanned helicopter as a real-time dynamic calibration cooperation target, and mounts the portable double-insertion real-time three-dimensional coordinate position recording device of this set of equipment to accurately analyze and process the helicopter track. Through time synchronization design, difference technology, acquisition and processing of radar measurement data, system noise elimination and outlier elimination, and data error analysis, the radar three-dimensional measurement accuracy error is finally obtained.

Contents of the invention

The present invention solves the technical defects of the existing shipboard three-coordinate radar calibration method, and provides a shipboard three-coordinate radar calibration device, which can perform convenient, efficient, safe and high-precision calibration operations on the radar three-dimensional detection accuracy including the elevation angle method.

Technical scheme of the present invention is:

A three-coordinate radar altitude dynamic calibration device based on an unmanned rotor helicopter, including three Beidou receivers, a ship-borne three-coordinate radar, a flight control system and a calculation subsystem. The system composition is shown in Figure 1. The three Beidou receiver terminals are Beidou receiver 1 installed on the reference point of the dock as a base station, Beidou receiver 2 installed in the center of the equivalent position of the ship, and Beidou receiver 3 installed on the rotor unmanned helicopter, see figure 2. The shipboard three-coordinate radar records data, the flight control system controls the flight of the rotor unmanned helicopter, and the calculation subsystem calculates the real height data.

The three-coordinate radar height dynamic calibration method is to record the physical position changes of the rotor unmanned helicopter and the ship by installing Beidou equipment on the rotor unmanned helicopter and the ship, and simultaneously use the ship radar to record data; during a series of flight actions Afterwards, the error processing and analysis of the true value data recorded on the rotor unmanned helicopter and the recorded data of the ship radar were carried out, and finally the error value of the radar elevation angle was obtained. Specific steps are as follows:

1. Measure the real height data

Three Beidou receivers receive more than 4 satellites synchronously and record raw data in real time. After the calibration is completed, the data is processed according to the data processing and error analysis process, and the precise position information of the ship and the rotor unmanned helicopter is obtained. If the real-time positioning error of the Beidou system is 1m, then the azimuth and elevation angle errors calculated in the radar coordinate system are within 0.002°, and the slant distance error is within 1m, which is several times higher than the radar positioning accuracy. If the elevation angle accuracy of the three-coordinate radar is 0.5°, the single-point positioning accuracy of the real height data equipment can fully meet the requirements within 5m. At present, the single-point accuracy of the carrier phase type Beidou can be fully achieved, and the differential processing is not required.

2. Solve the real height data

Since the Beidou coordinate system uses WGS-84 geodetic coordinates, the position of the target must be converted to the center spherical coordinate system with the radar as the origin, and the distance, azimuth and elevation angle values can be converted. Firstly, the geodetic coordinates measured by Beidou should be converted into space geodetic rectangular coordinates, then the space rectangular coordinates should be converted into station center rectangular coordinates, and finally the station center rectangular coordinates should be converted into station center spherical coordinates to obtain the real distance, azimuth and elevation angles. altitude data.

3. Unified time

In dynamic calibration, it is necessary to unify the measured value and the real height data in time, which is the prerequisite for comparing the measured point trace with the real height data point trace to obtain the error analysis result. The real altitude data is provided by Beidou equipment, and the data itself has UTC time. The position information recorded by the radar measurement value acquisition equipment adopts the highly stable atomic clock of the naval time system equipment as the oscillation source, and the error with the reference time of the real height data position information is less than 100ms, which meets the time unification requirements.

The currently used calibration methods mainly include building a calibration tower, releasing balloons or cooperating with the civil aviation ADS-B system, etc., but these methods have many deficiencies. The performance comparison with the calibration means of the present invention is shown in the table:

Calibration means dynamic performance safety calibration cost Calibration accuracy Civil aviation approval Calibration tower calibration Low high higher high no Military aircraft test flight calibration high high high Low yes Hot Air Balloon Calibration Low Low higher high yes Cooperative calibration of civil aviation system high high high Low yes This system (rotor unmanned helicopter) high high Low high no

The elevation angle calibration equipment of the present invention has novel system design ideas, scientific calibration methods, simple engineering implementation, and strong on-site operability. It uses an unmanned helicopter to mount a specific reflector as a cooperative target, which is highly controllable and measurable. Using the real altitude data acquisition method of "Beidou satellite + public communication network + real-time difference", the calibration accuracy is high, and the route can be planned arbitrarily, and the elevation angle of the radar can be calibrated at full altitude and in all directions.

Description of drawings

Figure 1 is a schematic diagram of the composition of the present invention.

Figure 2 is a schematic diagram of the location of the three Beidou receivers.

Figure 3 is a schematic diagram of the calibration process.

Figure 4 is a simulation diagram of the elevation angle measurement accuracy of the Beidou positioning system.

Fig. 5 is a flow chart of target true height data calculation.

Detailed ways

According to the technical standards for ship radar equipment repair, when the radar measurement accuracy is calibrated, the accuracy of the real height data equipment is required to be at least three times the radar measurement accuracy. Taking the typical value of three-coordinate radar accuracy as an example: the elevation angle accuracy is less than 0.5°, and the distance accuracy is less than 100m. It can be seen that if the accuracy of the real height data of the elevation angle is within 0.1°, and the accuracy of the real height data of the distance is within 25m, the requirement can be met.

It can be seen from the simulation figure 4 of the elevation angle measurement accuracy of the Beidou positioning system that when the distance between the radar and the target is 284.3687m, the elevation angle measurement accuracy is 0.1007°. That is, as long as the distance between the radar and the target exceeds 300m, the ranging accuracy of the Beidou positioning system has little effect on the elevation angle accuracy of the real height data. In addition, the near-range radar blind spot is generally 2-4km away, and the corresponding elevation angle accuracy is 0.015°, which is less than the required 0.1°. In the calibration process, in order to make the radar easy to find and measure the target, the distance between the target and the radar must be It is greater than 3km, so it can be seen that the elevation angle accuracy meets the calibration requirements during the entire calibration process.

1. Acquisition and processing of real height data and measured values

For different ships, there are three implementation methods for the acquisition of real height data and measured values:

One is to access the surface warship combat system through the data acquisition terminal, and obtain it by monitoring the target data message sent by the radar on the combat system network, which is suitable for new surface warships;

The second is to download the target track data from the radar display and control terminal, which is suitable for radar with target data storage function;

The third is to obtain target trace data through a data acquisition device that matches the radar output interface, which is suitable for old-fashioned radars.

In order to ensure the versatility of the recording equipment, the selection of the ship model and the marked radar should be realized, and the network interface protocol should be freely set according to the selection situation to record the radar measurement data. After the real height data is read, the data is preprocessed, and the calculation process is shown in Figure 5.

2. Realization of real height data calculation

In the present invention, the data collection frequency of real height data equipment is set to be 5Hz, that is, one data is taken in 0.2s; the rotating speed of the marked radar is set to be 15rpm, if two fronts work simultaneously, then the data collection frequency is 0.5Hz, That is, 2s to collect a data.

The analysis shows that in order to ensure that the elevation angle error is less than 0.1°, the time error of the real height data of the radar and the Beidou should be less than 0.5s. If random errors and the influence of other parts of the system are considered, the time error of the real height data of the radar and the Beidou is required to be average. It should be less than 0.2s. In order to meet the accuracy requirements, the radar measurement data should be interpolated.

3. Time unified implementation

In the present invention, in order to ensure correct system error calculation and meet the calibration accuracy index, it is required that the data time error of radar and Beidou real height data should be less than 0.5s. This is mainly due to the fact that when the cooperative target is flying stably, the flight speed is generally (40-55) km/h. If the time error between the radar and Beidou is 1s, a distance error of 15m will be generated and superimposed on the radar system error. The elevation angle error caused by this will be greater than 0.17°. In order to ensure that the elevation angle error is less than 0.1°, the time error of the radar and Beidou real height data data should be less than 0.5s. In addition, considering the influence of random errors and other parts of the system, it is required that the data time error of radar and Beidou real height data should be less than 0.1s.

For ships equipped with time system equipment, since the time system equipment uses a highly stable atomic clock as the oscillation source, the error with the Beidou reference time is less than 100ms, which can meet the requirements of radar calibration. In the actual operation process, it is affected by human factors. Time synchronization, etc., the accuracy and reliability of the time system system will deteriorate. Therefore, before accessing, it is necessary to compare the time output by the time system device with the UTC time to obtain the amount of time error. If the difference is not large, it can be ignored. If the difference If it is larger, this error will be compensated during data processing.

For ships without time system equipment, the solution to the time synchronization problem is to provide a separate time system system. Using the 1PPS second pulse signal output by the satellite positioning receiver and the decoded UTC information in NEMA-0183 as the time reference, the second pulse and the corresponding absolute time are transmitted to the main control computer of each radar data acquisition terminal, with an accuracy of less than 20ns. In addition, during radar tracking and measurement, the corresponding time of the target track generally output is not completely consistent with the time of the real height data, so the real height data needs to be interpolated and data supplemented.

Claims (2)

1. A three-coordinate radar height dynamic calibration device based on a rotorless unmanned helicopter, characterized in that the three-coordinate radar height dynamic calibration device includes three Beidou receiver terminals, a ship-borne three-coordinate radar data recording device, and a flight control system The three Beidou receiver terminals are Beidou receiver 1 installed on the reference point of the dock as a reference station, Beidou receiver 2 installed in the center of the equivalent position of the ship, and Beidou installed on the rotor unmanned helicopter Receiver 3: The shipboard three-coordinate radar records data, the flight control system controls the flight of the rotor unmanned helicopter, and the calculation subsystem calculates the real height data. 2. a kind of three-coordinate radar height dynamic calibration method based on rotor unmanned helicopter, it is characterized in that, The three-coordinate radar altitude dynamic calibration equipment based on the rotor unmanned helicopter includes three Beidou receiver terminals, shipboard radar data recording equipment, flight control system and calculation subsystem; the three Beidou receiver terminals are respectively installed on the dock Beidou receiver 1 as a reference station on the point, Beidou receiver 2 installed in the center of the equivalent position of the ship, and Beidou receiver 3 installed on the rotor unmanned helicopter; The three-coordinate radar height dynamic calibration method is to record the physical position changes of the rotor unmanned helicopter and the ship by installing Beidou equipment on the rotor unmanned helicopter and the ship, and simultaneously use the ship radar to record data; during a series of flight actions Afterwards, the error processing and analysis of the true value data recorded on the rotor unmanned helicopter and the recorded data of the ship’s radar are carried out, and finally the radar elevation angle error value is obtained; the specific steps are as follows: 1. Measure the real height data: Three Beidou receivers receive more than 4 satellites synchronously and record the original data in real time. After the calibration is completed, data processing is carried out according to the data processing and error analysis process, and the precise position information of the ship and the rotor unmanned helicopter is obtained; if the real-time positioning error of the Beidou system is 1m, it is attributed to the azimuth and elevation angle errors in the radar coordinate system Within 0.002°, the slant distance error is within 1m, which is several times higher than the radar positioning accuracy; if the three-coordinate radar elevation angle accuracy is 0.5°, the single-point positioning accuracy of the real height data equipment is within 5m, which fully meets the requirements; 2. Calculate the real height data: Beidou’s coordinate system uses WGS-84 geodetic coordinates. When using it, the position of the target must be converted to the center spherical coordinate system with the radar as the origin, and the distance, azimuth and elevation angle can be converted value; firstly, the geodetic coordinates measured by Beidou should be converted into spatial geodetic rectangular coordinates, then the spatial rectangular coordinates should be converted into station center rectangular coordinates, and finally the station center rectangular coordinates should be converted into station center spherical coordinates to obtain the distance, azimuth and Elevation angle true height data. 3. Unification of time: The real height data is provided by Beidou equipment, and the data itself has UTC time; the position information recorded by the radar measurement value recording device uses the high-stable atomic clock of the ship time system device as the oscillation source, and there is an error with the reference time of the real height data position information Less than 100ms, meeting the time uniform requirements.

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