Radio altimeter height measurement precision flight test verification method based on laser range finder

Abstract

The present application belongs to the field of aircraft flight test technology, and discloses a radio altimeter height measurement precision flight test verification method based on a laser range finder, comprising the following steps: step one: measuring the position difference between the radio altimeter and the laser range finder; step two: measuring the installation roll angle L θ1 and the installation pitch angle L θ2 of the laser range finder; step three: installing a data acquisition device on the aircraft, and synchronously collecting the laser range finder height H1, the radio height H2, the roll angle θ1, the pitch angle θ2, and the indicated airspeed Vi; step four: collecting the initial height value H0 of the laser range finder when the aircraft is in a ground stop state, and simultaneously recording the initial value I θ1 of the roll angle and the initial value I θ2 of the pitch angle of the inertial navigation system output; step five: controlling the aircraft to fly, and collecting the collected data through the data acquisition device; step six: calculating the measurement value deviation ΔH1(t) of the radio altimeter signal transceiver system and the laser range finder caused by the pitch attitude change; calculating the measurement value deviation ΔH2(t) of the radio altimeter signal transceiver system and the laser range finder caused by the roll attitude change; step seven: calculating the actual height from the ground H(t) measured by the laser range finder; step eight: calculating the flight test precision ΔH(t) of the radio altimeter height measurement; and step nine: calculating the mean value and the standard deviation of the flight test precision in the flight time period.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aircraft flight test technology, and particularly relates to a radio altimeter height measurement precision flight test verification method based on a laser range finder. BACKGROUND

[0002] A radio altimeter (Low Range Radio Altimter), also referred to as a radar altimeter, is applied to measure the height relative to the ground or water surface in the field of aircrafts. The radio altimeter is particularly important in the stages of take-off, climbing, low-altitude flight and speed-reducing approach flight of an aircraft, and provides real-time aircraft height information for pilots, which helps to prevent ground collision. The radio altimeter can normally work in various complex weather conditions such as heavy fog, clouds and rainy days, and is an indispensable general navigation basic equipment on modern aircrafts. The working principle of the radio altimeter is based on radar technology, which works by transmitting electromagnetic waves and receiving reflected waves reflected from the ground or water surface.

[0003] The performance indicators of the radio altimeter include sampling rate, transmission power, height measurement range and height measurement precision. The sampling rate and transmission power are generally verified through laboratory tests, and the height measurement range and height measurement precision need to be verified through special flight tests. The flight test verification method for the height measurement range is relatively simple: the aircraft continuously climbs in height until the radio altimeter does not display the height or the displayed value is fixed as a value that is no longer updated, and after the flight is completed, the radio altimeter cutoff height can be obtained by downloading the flight parameter data and analyzing the radio altimeter cutoff height in the flight parameter data. However, the flight test verification method for the height measurement precision is relatively complex.

[0004] The mainstream radio altimeter height measurement precision flight test verification method uses a total station or a differential GPS system for measurement. The total station height measurement flight test method can obtain relatively high measurement precision, but it cannot obtain continuous reference data, the number of sampling data points is often small, and it can only measure the radio altimeter height measurement precision of a hovering state aircraft, and cannot measure the radio altimeter height measurement precision of a level flight state aircraft. The differential GPS height measurement flight test method can obtain relatively high measurement precision, and the obtained data is continuous, and the amount of sampling data meets the data analysis requirements. However, it can only measure the radio altimeter height measurement precision of a hovering state helicopter, and cannot measure the radio altimeter height measurement precision of a level flight state aircraft. In addition, the aircraft needs to be parked in a hovering site for high-precision differential positioning before the flight test, and the measurement site is limited. SUMMARY

[0005] Invention purposes: the application provides a laser range finder based aircraft radio altimeter height measurement precision flight test verification method, which uses a laser range finder to measure and verify the radio altimeter height measurement precision in flight test, corrects the system error, obtains continuous test data meeting the data analysis requirements, and further obtains the radio altimeter height measurement precision in hovering and flat flying state.

[0006] Technical scheme

[0007] The laser range finder based radio altimeter height measurement precision flight test verification method comprises the following steps:

[0008] Step one: measure the position difference between the radio altimeter and the laser range finder;

[0009] Step two: measure the installation roll angle L θ1 and the installation pitch angle L θ2 of the laser range finder;

[0010] Step three: install a data acquisition device on the aircraft, and synchronously collect the laser range finder height H1, the radio height H2, the roll angle θ1, the pitch angle θ2, and the indicated airspeed Vi;

[0011] Step four: collect the initial height value H0 of the laser range finder when the aircraft is in the ground stop state; at the same time, record the initial value I θ1 of the roll angle and the initial value I θ2 of the pitch angle output by the inertial navigation system;

[0012] Step five: control the aircraft to fly, and collect the collected data through the data acquisition device;

[0013] Step six: calculate the deviation ΔH1(t) of the radio altimeter signal transceiver system and the laser range finder measurement value caused by the pitch attitude change; calculate the deviation ΔH2(t) of the radio altimeter signal transceiver system and the laser range finder measurement value caused by the roll attitude change;

[0014] Step seven: calculate the actual height from the ground H(t) measured by the laser range finder;

[0015] Step eight: calculate the flight test precision ΔH(t) of the radio altimeter height measurement;

[0016] Step nine: calculate the mean value and standard deviation of the flight test precision in the flight time period.

[0017] Further, the method further comprises: step ten: repeat steps five to nine, perform multiple flights, respectively calculate the mean value and standard deviation of the multiple flight test precision, and obtain the radio altimeter height measurement precision.

[0018] Further, in step one, the position difference of the radio altimeter and the laser range finder in longitudinal, lateral and heading direction is measured, and is recorded as L1, L2 and L3 respectively.

[0019] Further, in step five, the aircraft is controlled to take off in hovering mode, and the height from the ground is about 5m, and the hovering is stabilized for 5 minutes, and a group of data is collected.

[0020] Further, in step five, the aircraft is controlled to take off in hovering mode, and the height from the ground is about 5m, and the hovering is stabilized for 5 minutes, and a group of data is collected.

[0021] Further, in step six, the calculation process of the measurement value deviation caused by the change of the pitch attitude is as follows:

[0022] ΔH1(t)=(L2+L3)sin[θ2(t)-(Iθ2-Lθ2)].

[0023] Further, in step six, the calculation process of the measurement value deviation caused by the change of the roll attitude is as follows:

[0024] ΔH2(t)=(L1)sin[θ1(t)-(Iθ1-Lθ1)].

[0025] Further, in step seven, the calculation formula of the actual height from the ground is as follows:

[0026] H(t)=H1(t)cos[θ2(t)-(Iθ2-Lθ2)].

[0027] Further, in step eight, the calculation process of the height measurement accuracy is as follows:

[0028] ΔH(t)=H(t)+ΔH1(t)+ΔH2(t)-H2(t).

[0029] In summary, the beneficial effects of the present application are as follows:

[0030] The present application uses the laser range finder to realize the measurement and verification of the radio altimeter height measurement accuracy in the flight test state of the aircraft, has high sampling rate and high measurement accuracy, the method is reliable to implement, the obtained test data is continuous data, and the test data analysis requirements are met. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a schematic diagram of the measurement data of the radio altimeter and the laser range finder.

[0032] Figure 2 It is a height measurement accuracy change course diagram of the radio altimeter with time. DETAILED DESCRIPTION

[0033] The application provides a laser range finder-based aircraft radio altimeter height measurement precision flight test verification method, comprising basic data measurement, test data acquisition, hovering and steady flight state flight test, height measurement precision analysis and calculation. The flight test verification method mainly comprises the following steps:

[0034] 1) Due to the installation position limitation, the laser range finder cannot be installed at the same position as the radio altimeter, and the laser range finder is installed below the aircraft;

[0035] 2) The position differences L1, L2 and L3 of the radio altimeter signal transceiver system and the laser range finder in the lateral direction, longitudinal direction and heading direction of the helicopter are measured;

[0036] 3) The inclination angle L θ1 and the pitch angle L θ2 of the laser range finder installation are measured using a level;

[0037] 4) An airborne data acquisition device is installed on the aircraft to collect the laser range finder height H1, the radio altimeter height H2, the aircraft roll angle θ1, the aircraft pitch angle θ2, the aircraft indicated airspeed Vi, and flight control parameters, wherein the indicated airspeed is used for flight state identification, and other parameters are used for precision calculation;

[0038] 5) The aircraft is powered on while grounded, and the ranging height value H0 of the laser range finder is collected; at the same time, the initial value I θ1 of the helicopter roll angle and the initial value I θ2 of the pitch angle output by the aircraft inertial navigation system are recorded;

[0039] 6) The aircraft takes off and hovers at a height of about 5m, and stabilizes for 5 minutes, and the airborne data acquisition device continuously records each measurement parameter;

[0040] 7) The aircraft stabilizes at a height of about 40m and flies at an indicated airspeed of 150km / h for 1 minute, and the airborne data acquisition device continuously records each measurement parameter;

[0041] 8) Each of steps 6) and 7) is repeated three times, the aircraft lands, and the measurement data recorded by the airborne data acquisition device is downloaded;

[0042] 9) The time period when the helicopter performs stable hovering and stable steady flight is identified according to the indicated airspeed, flight attitude and flight control parameters, and the data of the laser range finder height H1(t), the radio altimeter height H2(t), the helicopter roll angle θ1(t), the helicopter pitch angle θ2(t), the aircraft indicated airspeed Vi(t) and the like varying with time t in the corresponding time period are extracted from the measurement data;

[0043] 10) The data extracted in step 9) is used to calculate the time variation of the difference between the radio altimeter signal transceiver system and the laser rangefinder measurement caused by the change in the helicopter's pitch attitude according to formula (1):

[0044] ΔH1(t) = (L2+L3) sin [θ2(t) - (Iθ2 - Lθ2)] (1)

[0045] 11) The data extracted in step 9) is used to calculate the time variation of the difference between the radio altimeter signal transceiver system and the laser rangefinder measurement caused by the change in the helicopter's roll attitude according to formula (2):

[0046] ΔH2(t) = (L1) sin [θ1(t) - (Iθ1 - Lθ1)] (2)

[0047] 12) The data extracted in step 9) is used to calculate the actual height above ground measured by the laser rangefinder according to formula (3). The laser rangefinder measures the actual distance from the laser beam to the reflection point on the ground, not the actual height above ground of the aircraft, which needs to be corrected:

[0048] H(t) = H1(t) cos [θ2(t) - (Iθ2 - Lθ2)] (3)

[0049] 13) The data extracted in step 9) and the results of 10), 11), and 12) are used to calculate the flight test accuracy of the radio altimeter height measurement according to formula (4):

[0050] ΔH(I) = H(l) + ΔH1(l) + ΔH2(l) - H2(l) (4)

[0051] 14) The radio altimeter height measurement accuracy in stable hovering and stable level flight states is calculated according to steps 10) to 13) respectively;

[0052] 15) The average value of the radio altimeter height measurement accuracy data obtained in step 13) is calculated according to formula (5), where n is the total number of data collected:

[0053] ΔH a = ∑ΔH(t) / n (5)

[0054] 16) The standard deviation of the radio altimeter height measurement accuracy data obtained in step 13) is calculated according to formula (6):

[0055] (6)

[0056] 17) The average value and standard deviation of the height measurement accuracy data obtained from three repeated flights in stable hovering and stable level flight are calculated respectively, and the radio altimeter height measurement accuracy characteristics are given in the form of (average value ± standard deviation).

[0057] During the flight test, the installation and measurement errors of the laser range finder, and the errors caused by the change of the aircraft flight attitude during the flight process due to the installation position of the laser range finder and the radio altimeter can be accurately calculated through the above flight test verification method, and then the height measurement accuracy of the radio altimeter during the flight test of the aircraft is obtained.

[0058] By calculating the mean value of the height measurement accuracy data of the radio altimeter, the error caused by chance can be effectively excluded. By calculating the standard deviation of the height measurement accuracy data of the radio altimeter, the concentration of the data can be viewed, and then the measurement quality of the radio altimeter is fed back.

[0059] Embodiment

[0060] The laser range finder is installed on the right side of the short wing of the aircraft, and the UMA2000 data collector is installed inside the aircraft. The power supply is connected to the 28V direct current on the aircraft, and the atmospheric data system indicating airspeed bus data, inertial navigation system, aircraft roll angle, pitch angle, and radio altimeter height bus data are extracted respectively. After completing the test modification, the test equipment is powered on for inspection, and the basic data is measured to obtain the position difference L1=2.2m, L2=4m, L3=1.1m, installation roll angle L θ1 =-0.23°, installation pitch angle L θ2 =0.4°, initial value of roll angle I θ1 =0°, initial value of pitch angle I θ2 =0.83°, and initial height value H0=0.84m of the laser range finder.

[0061] The aircraft performs hovering flight test, and data is collected at a sampling rate of 20Hz, a total of 3 times, the first flight test 388s, a total of 7771 point data, the second flight test 394s, a total of 7869 point data, and the third flight test 396s, a total of 7901 point data. According to the flight test verification method, the flight test data is calculated, and the mean value of the height measurement accuracy of the radio altimeter in the flight test state is 0.21m, and the standard deviation is 0.10m.

[0062] The aircraft performs a steady flight test, and data is collected at a sampling rate of 20Hz, a total of 3 times, the first flight test 49s, a total of 967 point data, the second flight test 51s, a total of 1001 point data, and the third flight test 52s, a total of 1031 point data. According to the flight test verification method, the flight test data is calculated, and the mean value of the height measurement accuracy of the radio altimeter in the flight test state is 0.39m, and the standard deviation is 0.12m.

Claims

1. A flight test verification method for laser range finder based radio altimeter height measurement, characterized in that: The method comprises the following steps: Step one: measure the position difference between the radio altimeter and the laser range finder; Step two: Measure the installation roll angle L of the laser range finder θ1 and the installation pitch angle L θ2 ; Step three: install a data acquisition device on the aircraft, and synchronously collect the height H1 of the laser range finder, the height H2 of the radio altimeter, the roll angle θ1, the pitch angle θ2, and the indicated airspeed Vi; Step four: collect the initial height value H0 of the laser range finder when the aircraft is in the ground parking state; record the initial value I of the roll angle of the aircraft output by the inertial navigation system at the same time θ1 and the initial value I of the pitch angle θ2 ; Step five: control the flight of the aircraft, and collect the collected data through the data acquisition device; Step six: Calculate the radio altimeter signal transceiver system and laser rangefinder measurement bias caused by the change in pitch attitude ; Computing the deviation of radio altimeter signal transceiver system measurements from laser rangefinder measurements caused by changes in roll attitude ; Step seven: Calculate the actual height above ground measured by the laser rangefinder ; Step eight: Calculate the flight test accuracy of radio altimeter height ; Step nine: calculate the mean value and the standard deviation of the test flight precision in the flight period.

2. The method of claim 1, wherein: The method further comprises: step ten: repeat steps five to nine, perform multiple flights, respectively calculate the mean value and the standard deviation of the test flight precision of the multiple flights, and obtain the height measurement precision of the radio altimeter.

3. The method of claim 2, wherein: In step one, the position difference between the radio altimeter and the laser range finder in the longitudinal direction, the lateral direction, and the heading direction is measured, and is respectively denoted as L1, L2, and L3.

4. The method of claim 3, wherein: In step five, the aircraft is controlled to take off in a hovering manner, the height from the ground is 5 m, the hovering is stabilized for 5 min, and a group of data is collected.

5. The method of claim 4, wherein: In step five, the aircraft is controlled to fly steadily at an indicated airspeed of 150 km / h at a height of 40 m from the ground for 1 min, and a group of data is collected.

6. The method of claim 5, wherein: In step six, the calculation process of the measurement value deviation caused by the change of the pitch attitude is as follows: 。 7. The method of claim 6, wherein: In step six, the calculation process of the measurement value deviation caused by the change of the roll attitude is as follows: 。 8. The method of claim 7, wherein: In step seven, the actual height from the ground is calculated according to the following formula: 。 9. The method of claim 8, wherein: In step eight, the calculation process of the height measurement precision is as follows: 。

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