Airflow angle estimation method for light small low-cost unmanned aerial vehicle under simple sensor configuration

Abstract

The application discloses a flow angle estimation method for a light, small and low-cost unmanned plane under a simple sensor configuration, and provides an expression for displaying and estimating the flow angle from the definition of the flow angle; under the condition that the sensor configuration is an inertial navigation system and an air speed tube, inertial angles of attack and inertial sideslip angles are calculated by using attitude angle information, a track tilt angle and a track azimuth angle; wind speed and a wind direction are estimated by using ground speed, true air speed and a drift angle according to a wind speed triangle; the estimated wind field information is used to compensate the inertial angles of attack and the inertial sideslip angles, so that the accurate estimation of the flow angle is obtained. The application provides a flow angle estimation method for the light, small and low-cost unmanned plane under the simple sensor configuration, and does not need to increase additional on-board sensor equipment, so that the flight safety is ensured without increasing the cost and the weight of the unmanned plane.

Description

Technical Field

[0001] This invention relates to a method for estimating the airflow angle of a lightweight, low-cost unmanned aerial vehicle with a simple sensor configuration, belonging to the field of aerospace technology. Background Technology

[0002] Angle of attack and sideslip angle, collectively known as airflow angles, are crucial flight status parameters affecting flight safety. Their accuracy and reliability directly impact the operational status and performance of critical airborne systems such as flight control systems, stall warning systems, and flight management systems. Furthermore, angle of attack and sideslip angle are frequently used as feedback signals in flight control; inaccurate angle of attack and sideslip angle information can lead to serious flight accidents.

[0003] For large aircraft equipped with numerous sensors, an Air Data System (ADS) or a Flushed Air Data System (FADS) can provide the crew with accurate airflow angle information. However, due to cost and weight limitations, the sensor configuration on small UAVs is relatively simple and generally does not include ADS and FADS. Therefore, for lightweight, low-cost UAVs with simple sensor configurations, accurate estimation of airflow angles is crucial for ensuring their safe flight. This invention is proposed against this background, focusing on lightweight, low-cost UAVs, and estimating the angle of attack and sideslip angle with a simple sensor configuration. This is of great significance for improving the safety of the control system and ensuring flight safety. Summary of the Invention

[0004] To address the problem of airflow angle estimation for lightweight, low-cost unmanned aerial vehicles (UAVs) with simple sensor configurations, this invention proposes an airflow angle estimation method for lightweight, low-cost UAVs with simple sensor configurations. This method utilizes measurement information provided by an inertial navigation system and an airspeed tube to estimate the airflow angle, thereby ensuring flight safety.

[0005] Specifically, the present invention proposes a method for estimating the airflow angle of a lightweight, low-cost unmanned aerial vehicle with a simple sensor configuration, characterized by the following steps:

[0006] Step 1: Calculate the azimuth angle χ based on the sensor measurements of the UAV. The sensor configuration of a given UAV is: inertial navigation system, pitot tube; based on the characteristics and functions of the navigation sensors, the inertial navigation system can measure position information (latitude, longitude, and altitude) and velocity information (eastward velocity V). E Northbound speed V N Vertical velocity V U and ground speed V g Attitude information (pitch angle θ, roll angle φ, and heading ψ), and the pitot tube can measure vacuum speed V. aThe formula for calculating the azimuth angle χ of the flight path is:

[0007]

[0008] Step 2: Calculate the track inclination angle γ. The calculation formula is:

[0009]

[0010] Step 3: Calculate the deflection angle A DA The calculation formula is:

[0011]

[0012] Where sgn(·) is the sign function.

[0013] Step 4: Calculate the angle of attack α k and inertial sideslip angle β k Specifically:

[0014] Step 4.1: Calculate the coordinate transformation matrix from the track coordinate system to the body coordinate system. The calculation method is as follows:

[0015]

[0016] in It is the rotation transformation matrix from the track coordinate system to the ground coordinate system. It is the rotation transformation matrix from the ground coordinate system to the body coordinate system.

[0017] Step 4.2: Simplify the coordinate transformation matrix Because α k and β k All are small angles, satisfying

[0018]

[0019] therefore It can be simplified to

[0020]

[0021] Step 4.3: Calculate the rotation transformation matrix from the track coordinate system to the ground coordinate system. The calculation method is as follows:

[0022]

[0023] Step 4.4: Calculate the rotation transformation matrix from the ground coordinate system to the body coordinate system. The calculation method is as follows:

[0024]

[0025] Step 4.5: Combining Steps 4.1, 4.3, and 4.4, establish the relation:

[0026]

[0027] Step 4.6: Since (χ-ψ) and (θ-γ) are generally small angles, they satisfy...

[0028]

[0029] Therefore, the relation in step 4.5 can be simplified to obtain...

[0030]

[0031] Step 4.7: Combining Step 4.2 and Step 4.6, obtain the inertial angle of attack α. k and inertial sideslip angle β k

[0032]

[0033] Step 5: Estimate wind speed V w Wind direction A w Specifically:

[0034] Step 5.1: Based on the wind speed triangle, use the inertial navigation system to measure the ground speed V. g Vacuum speed V measured by airspeed tube a And the deflection angle A calculated in step 3 DA The formula for calculating wind speed is:

[0035]

[0036] Step 5.2: Calculate the wind direction using the following formula:

[0037]

[0038] in

[0039] A w '=χ+π+Asgn(A DA )

[0040] A is an auxiliary angle, which can be calculated using the Law of Cosines. The formula is:

[0041]

[0042] Step 6: Estimate the airflow angle, i.e., estimate the angle of attack α and sideslip angle β, specifically:

[0043] Step 6.1: Calculate the wind vector components u on the three axes of the body coordinate system. w ,v w ,w w Specifically:

[0044] Step 6.1.1: Decompose the wind vector to obtain the easterly wind V. w,y and northerly wind V w,x The calculation formula is:

[0045]

[0046] Step 6.1.2: The wind vector is defined in the ground coordinate system and can be transformed using a coordinate transformation matrix. Transform it to the body coordinate system to obtain u. w ,v w ,w w The calculation formula is:

[0047]

[0048] Step 6.2: Calculate the angle of attack increment Δα and sideslip angle increment Δβ caused by wind. The calculation formula is as follows:

[0049]

[0050] Step 6.3: Based on the inertial angle of attack α calculated in Step 4 k and inertial sideslip angle β k And the angle of attack increment Δα and sideslip angle increment Δβ calculated in step 6.2 are used to estimate the airflow angles, i.e., the angle of attack α and sideslip angle β. The calculation formula is as follows:

[0051]

[0052] The advantages of this invention are as follows: Unlike existing airflow angle estimation methods based on Kalman filtering and artificial intelligence, this invention starts from the definition of airflow angle and gives an explicit estimation expression for airflow angle, which is simpler and clearer in form; in addition, this invention provides an airflow angle estimation method for lightweight and low-cost UAVs with simple sensor configurations without the need to add additional airborne sensor equipment, thereby improving safety without increasing cost or UAV weight. Attached Figure Description

[0053] The accompanying drawings provided in this section are used to further explain the present invention and constitute a part of this application. The schematic diagrams and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0054] Figure 1 Schematic diagram of coordinate system transformation

[0055] Figure 2 Schematic diagram of the projection of the wind speed triangle on the ground

[0056] Figure 3 Horizontal wind decomposition diagram

[0057] Figure 4 track azimuth

[0058] Figure 5 Track inclination angle

[0059] Figure 6 Deflection angle

[0060] Figure 7 Angle of attack and angle of sideslip

[0061] Figure 8 The estimated wind direction and wind speed

[0062] Figure 9 The estimated airflow angles (angle of attack and sideslip angle) Detailed Implementation

[0063] The present invention will be explained in detail below with reference to the accompanying drawings. It should be noted that the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0064] Problem Description: The sensor configuration of a small, low-cost drone is as follows: inertial navigation system, pitot tube; the working scenario is that the aircraft maintains steady level flight at an altitude of 500m, a flight speed of 80m / s, and a heading of 45°; the horizontal mode is set to heading hold mode, that is, the aircraft maintains its initial heading unchanged; the simulation time is 100s, and within 0-50s, the wind speed is 3m / s and the wind direction is 60°, and within 50-100s, the wind speed is 5m / s and the wind direction is 45°.

[0065] The specific solution is as follows:

[0066] Step 1: Calculate the azimuth angle χ of the flight path, and measure the eastward velocity V of the UAV using the inertial navigation system. E Northbound speed V N Vertical velocity V U Ground speed V g The airspeed V of the UAV is obtained by measuring the pitch angle θ, roll angle φ, and heading ψ, and the pitot tube. a The method for calculating the azimuth angle χ of the flight path is as follows: The results are as follows Figure 4 As shown;

[0067] Step 2: Calculate the track inclination angle γ. The calculation method is as follows: The results are as follows Figure 5 As shown;

[0068] Step 3: Calculate the deflection angle A DA The calculation method is as follows Where sgn(·) is the sign function: The results are as follows Figure 6 As shown;

[0069] Step 4: Calculate the angle of attack α k and inertial sideslip angle β k The calculation method is as follows The results are as follows Figure 7 As shown;

[0070] Step 5: Estimate wind speed and direction, calculated as follows: in The results are as follows Figure 8 As shown;

[0071] Step 6: Estimate the angle of attack and sideslip angle to obtain the airflow angle. The calculation method is as follows: The results are as follows Figure 9 As shown, where

[0072]

[0073] Following the steps above, the simulation examples were performed under the set conditions in the Matlab / Simulink simulation environment, and the results were as follows: Figures 4 to 9 The simulation results are shown. The simulation results demonstrate that the airflow angle estimation method for a lightweight, low-cost UAV with a simple sensor configuration proposed in this invention can accurately estimate the airflow angles (i.e., angle of attack and sideslip angle). When wind direction and speed change, the maximum estimation error for the sideslip angle is 0.4°, and the maximum estimation error for the angle of attack is only 0.05°, which meets the accuracy requirements of the control system for airflow angles.

Claims

1. A method for airflow angle estimation of a light small low-cost unmanned aerial vehicle with simple sensor configuration, characterized in that, The steps are as follows: Step 1: Calculate the track azimuth χ according to the sensor measurement results of the unmanned aerial vehicle configuration; the sensor configuration of a certain unmanned aerial vehicle is known: inertial navigation system, airspeed tube; according to the characteristics and functions of the navigation sensor, the inertial navigation system can measure position information, speed information and attitude information, wherein the position information includes longitude, latitude and height, the speed information includes eastward speed VE, northward speed VN, vertical speed VU and ground speed Vg, and the attitude information includes pitch angle θ, roll angle φ and heading ψ; the airspeed tube measures true airspeed Va; then the calculation formula of the track azimuth χ is: Step 2: Calculate the track tilt angle The calculation formula is: Step 3: Calculate the drift angle The calculation formula is: wherein is the sign function; Step 4: Calculate the inertial angle of attack and the inertial sideslip angle , in particular: Step 4.1: Calculate the coordinate transformation matrix from the track coordinate system to the body coordinate system The calculation method is: wherein is a rotation transformation matrix from the track coordinate system to the ground coordinate system, is a rotation transformation matrix from the ground coordinate system to the body coordinate system; Step 4.2: Simplify the coordinate transformation matrix ; since and satisfy Thus are reduced to Step 4.3: Calculate the rotation transformation matrix from the track coordinate system to the ground coordinate system The calculation method is: Step 4.4: Calculate the rotation transformation matrix from the ground coordinate system to the body coordinate system The calculation method is: Step 4.5: Establish the relationship formula by combining steps 4.1, 4.3 and 4.4: Step 4.6: Since and satisfies Therefore, the relationship formula in step 4.5 can be simplified to Step 4.7: Combine step 4.2 and step 4.6 to get the inertial angle of attack and the inertial sideslip angle Step 5: Estimate wind speed and wind direction , in particular: Step 5.1: Calculate the wind speed using the measured ground speed from the inertial navigation system, the measured true airspeed from the pitot tube, and the calculated angle of sideslip from step 3, according to the wind speed triangle relationship The wind speed is calculated using the formula:​​ Step 5.2: Calculate the wind direction, and the calculation formula is: wherein is an auxiliary angle, which can be calculated according to the cosine law, and the calculation formula is Step 6: Estimate the airflow angle, i.e. the angle of attack and the sideslip angle in particular: Step 6.1: Calculate the components of the wind vector on the three axes of the body coordinate system In particular: Step 6.1.1: Decompose the wind vector into an eastward wind and a northward wind , calculated as: Step 6.1.2: The wind vector is defined in the ground coordinate system and can be transformed by the coordinate transformation matrix to the body coordinate system, and then the wind vector in the body coordinate system is obtained The calculation formula is: Step 6.2: Calculate the angle of attack increment caused by the wind and the sideslip angle increment , the formula is: Step 6.3: Calculate the angle of attack based on the inertia obtained in Step 4. and inertial sideslip angle and the angle of attack increment calculated in step 6.2 and sideslip angle increment Estimate the airflow angle, i.e., the angle of attack. and sideslip angle The calculation formula is: 。

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