KR102734739B1 - Airspeed estimation method and apparatus using propeller performance analysis method - Google Patents

Abstract

A method and device for estimating airspeed using a propeller performance analysis method are disclosed. According to an embodiment of the present invention, a method for estimating airspeed using a propeller performance analysis method includes, in connection with a propeller-propelled aircraft, a step of calculating an equivalent lift coefficient and an equivalent drag coefficient as propeller equivalent aerodynamic data; a step of writing each of the equivalent lift coefficient and the equivalent drag coefficient as an equivalent lift coefficient polynomial and an equivalent drag coefficient polynomial, which are functions of an angle of attack; and a step of finding an advance ratio corresponding to an input shaft power coefficient of the aircraft using the equivalent lift coefficient polynomial and the equivalent drag coefficient polynomial, thereby estimating an airspeed during flight of the aircraft.

Description

{AIRSPEED ESTIMATION METHOD AND APPARATUS USING PROPELLER PERFORMANCE ANALYSIS METHOD}

The present invention relates to a method and device for estimating airspeed using a propeller performance analysis method, which estimates airspeed during flight using propeller-related sensing values in a propeller-propelled aircraft connected to an electric motor.

Air speed is one of the most important variables in aircraft control.

Existing airspeed measuring devices sold for aircraft installation use the Pitot-static method.

Because deficiencies in airspeed measurements can lead to erroneous pilot inputs and have serious consequences for flight safety, aircraft must be equipped with multiple reliable airspeed measurement devices.

Conventional airspeed measuring devices using the pitot-static method use pitot tubes that protrude externally, so failures may occur when the pitot tubes become blocked by ice, water, moisture, foreign substances, etc.

In past aircraft accident cases, many accidents have been reported as being caused by the failure of the pitot tube of an airspeed measuring device using the pitot-static method.

Due to concerns about pitot tube failure, there are methods to duplicate or triple the airspeed measuring device, but this redundancy method increases the weight and cost due to the additional hardware.

In addition, the method of multiplexing airspeed measuring devices has the disadvantage of not being able to prevent cases where airspeed measuring devices fail simultaneously.

Existing airspeed measuring devices using the pitot-static pressure method have a problem in that the error increases rapidly when the airspeed is below about 50 km/h, making it difficult to measure airspeed properly.

The problems with these existing airspeed measuring devices using the pitot-static method cannot be avoided because they are problems with the measurement range of the pressure sensor, although there are slight differences in the minimum measurable speed values depending on the product.

Therefore, there is an urgent need for a new airspeed estimation model that estimates airspeed using a propeller performance analysis method without using hardware such as a pitot tube of existing airspeed measuring devices.

An embodiment of the present invention aims to provide a method and device for estimating airspeed using a propeller performance analysis method, which estimates airspeed using various data related to a propeller in an aircraft propelled by a propeller connected to an electric motor.

In addition, the purpose of this embodiment is to predict airspeed using a propeller performance analysis method, so that it is independent from an existing pitot-static airspeed measuring device, and thus, when used together, the reliability of the airspeed measuring device is increased, and since there is no additional hardware, it contributes to weight and cost reduction.

In addition, the purpose of this embodiment is to utilize it as a redundancy that serves as a backup function in the event of a failure of the primary equipment, a pitot-static type airspeed measuring device.

In addition, the purpose of this embodiment is to provide an airspeed estimation model that can accurately predict speed without increasing error even in a low speed range of 0 to 50 km/h.

According to one embodiment of the present invention, a method for estimating airspeed using a propeller performance analysis method may include the steps of: calculating an equivalent lift coefficient and an equivalent drag coefficient as propeller equivalent aerodynamic data in relation to a propeller-propelled aircraft; writing each of the equivalent lift coefficient and the equivalent drag coefficient as an equivalent lift coefficient polynomial and an equivalent drag coefficient polynomial, which are functions of an angle of attack; and estimating an airspeed during flight of the aircraft by finding an advance ratio corresponding to an input shaft power coefficient of the aircraft using the equivalent lift coefficient polynomial and the equivalent drag coefficient polynomial.

In addition, according to an embodiment of the present invention, an airspeed estimation device using a propeller performance analysis method may be configured to include a calculation unit that calculates an equivalent lift coefficient and an equivalent drag coefficient as propeller equivalent aerodynamic data in connection with a propeller-propelled aircraft; a writing unit that writes each of the equivalent lift coefficient and the equivalent drag coefficient as an equivalent lift coefficient polynomial and an equivalent drag coefficient polynomial, which are functions of an angle of attack; and a processing unit that finds an advance ratio corresponding to an input shaft power coefficient of the aircraft using the equivalent lift coefficient polynomial and the equivalent drag coefficient polynomial, thereby estimating an airspeed during flight of the aircraft.

According to one embodiment of the present invention, in an aircraft propelled by a propeller connected to an electric motor, an airspeed estimation method and device using a propeller performance analysis method for estimating airspeed using various data related to the propeller can be provided.

In addition, since the present invention predicts airspeed using a propeller performance analysis method, it is independent from the existing pitot-static pressure type airspeed measuring device, and thus, when used together, the reliability of the airspeed measuring device can be increased, and since there is no additional hardware, it can contribute to weight and cost reduction.

In addition, according to the present invention, it can be utilized as a redundancy that serves as a backup function in the event of a failure of the primary equipment, the pitot-static pressure type airspeed measuring device.

In addition, the present invention provides an airspeed estimation model capable of accurately predicting speed without increasing error even in a low-speed range of 0 to 50 km/h.

FIG. 1 is a block diagram illustrating the configuration of an airspeed estimation device using a propeller performance analysis method according to an embodiment of the present invention.
Figure 2 is an example of the configuration of a propeller-driven aircraft.
Figure 3 is a diagram explaining the force and speed at the blade cross section.
Figure 4 is a diagram to explain the relationship between speed and angle in the blade cross section.
Figure 5 is a drawing illustrating the external appearance of the APC FF 4.2x4 propeller.
Figure 6 is a graph comparing the angle of attack and the equivalent lift coefficient.
Figure 7 is a graph comparing the angle of attack and the equivalent drag coefficient.
Figure 8 shows the predicted airspeed results (y-axis) for a given shaft power (x-axis).
FIG. 9 is a flow chart illustrating an airspeed estimation method using a propeller performance analysis method according to an embodiment of the present invention.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. However, since various modifications may be made to the embodiments, the scope of the patent application rights is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, or substitutes to the embodiments are included in the scope of the rights.

The terms used in the examples are for the purpose of description only and should not be construed as limiting. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, the terms "comprises" or "has" and the like are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood to not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments belong. Terms defined in commonly used dictionaries, such as those defined in common dictionaries, should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and shall not be interpreted in an idealized or overly formal sense, unless expressly defined in this application.

In addition, when describing with reference to the attached drawings, the same components will be given the same reference numerals regardless of the drawing numbers, and redundant descriptions thereof will be omitted. When describing an embodiment, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description thereof will be omitted.

FIG. 1 is a block diagram illustrating the configuration of an airspeed estimation device using a propeller performance analysis method according to an embodiment of the present invention.

Referring to FIG. 1, an airspeed estimation device (hereinafter, abbreviated as 'airspeed estimation device') (100) using a propeller performance analysis method according to one embodiment of the present invention may be configured to include a calculation unit (110), a writing unit (120), and a processing unit (130).

First, the calculation unit (110) is associated with a propeller-driven aircraft and calculates an equivalent lift coefficient and an equivalent drag coefficient as propeller equivalent aerodynamic data. That is, the calculation unit (110) can calculate an equivalent lift coefficient and an equivalent drag coefficient applied to the propeller by using propeller basic shape data and propeller performance data.

The lift coefficient is the dimensionless component of the force perpendicular to the flow acting on an object placed in a flow, i.e., lift. It can be determined by the cross-sectional shape of the object parallel to the flow, the angle between the object and the flow, the Reynolds number, and the Mach number.

The drag coefficient is a coefficient that represents the drag force received by an object moving in a flow. It can be a dimensionless constant used when quantifying the resistance received by an object in a flow.

In calculating the equivalent lift coefficient and the equivalent drag coefficient, the calculation unit (110) can read blade data of the blades constituting the propeller.

For example, the calculation unit (110) calculates the propeller diameter , number of blades , of the blade Code in location , and blade pitch angle The basic shape data of the propeller can be read.

Additionally, the calculation unit (110) can read propeller performance data of the propeller.

For example, the calculation unit (110) is initially given a forward ratio , thrust coefficient , and power coefficient You can read the propeller performance data of the above thrust coefficient. , and power coefficient can be obtained through wind tunnel testing or CFD calculations.

In addition, the calculation unit (110) calculates the equivalent lift coefficient by the Newton-Rapson method using the blade data and the propeller performance data as inputs. and the equivalent drag coefficient can be calculated.

The Newton-Rapson method is an iterative solution method that finds approximate values by infinitely reducing the interval a≤x≤b that contains the solution when the real roots of an n-th order equation cannot be found by factoring or calculations such as the root formula.

The calculation unit (110) satisfies [Formula 1] to obtain the equivalent lift coefficient. and the equivalent drag coefficient can be calculated.

[Formula 1]

,

Here, is 'solidity', is the 'resultant relative velocity', is 'rotation rate', is the 'propeller radius', is a 'dimensionless length', is the 'flow angle', is the 'thrust coefficient', is the 'power coefficient'.

The writing unit (120) writes the equivalent lift coefficient and the equivalent drag coefficient as an equivalent lift coefficient polynomial and an equivalent drag coefficient polynomial, respectively, which are functions of the angle of attack. That is, the writing unit (120) can play a role of writing the calculated equivalent lift coefficient and the equivalent drag coefficient as polynomials by expressing them as functions of the angle of attack.

The angle of attack can refer to the angle between the baseline (chord line) of the cut surface of the airplane's wing and the airflow.

The writing unit (120) satisfies [Formula 2] and the equivalent lift coefficient and the equivalent drag coefficient , the angle of reception can be written as a function of .

[Formula 2]

The processing unit (130) estimates the airspeed of the aircraft during flight by finding the advance ratio corresponding to the input shaft power coefficient of the aircraft using the equivalent lift coefficient polynomial and the equivalent drag coefficient polynomial. That is, the processing unit (130) can calculate the advance ratio of the aircraft by the equivalent lift coefficient polynomial and the equivalent drag coefficient polynomial, and estimate the airspeed of the aircraft by the calculated advance ratio.

In estimating the airspeed, the processing unit (130) can receive the propeller operating conditions of the propeller.

The processing unit (130) can receive inputs such as atmospheric temperature, atmospheric pressure, propeller RPM, and propeller blade angle as propeller operating conditions.

Additionally, the processing unit (130) can calculate the input shaft power coefficient.

The processing unit (130) calculates the axial power of the aircraft according to [Formula 3]. By expressing it in the form of a power coefficient, the input shaft power coefficient can be calculated.

[Formula 3]

: air density

: rotation frequency (revolution per second)

: Propeller diameter

: Axial power

: Input shaft power coefficient

Continuing, the processing unit (130) can perform the Inner Loop and Outer Loop by the Newton-Rapson method using the propeller operating conditions and the input shaft power coefficient as inputs.

The processing unit (130) can calculate the inner loop and outer loop twice using the Newton-Rapson method. The processing unit (130) can calculate the forward ratio Calculate the Outer Loop using dummy variable as a variable Inner Loop can be calculated using as a variable.

The outer loop of the Newton-Rapson method has a parameter called the forward ratio. It can be. Forward ratio The inner loop of the Newton-Rapson method has a dummy variable parameter It can be.

Afterwards, the processing unit (130) performs the forward ratio by repeatedly performing the Inner Loop and the Outer Loop. can converge to a certain value.

The above advance ratio After convergence to a certain value, the processing unit (130) satisfies [Formula 4] and converges to the above advance ratio to a certain value. From air speed can be estimated.

[Formula 4]

Above is the 'rotation frequency', and the above can be the 'propeller diameter'.

According to one embodiment of the present invention, in an aircraft propelled by a propeller connected to an electric motor, an airspeed estimation method and device using a propeller performance analysis method for estimating airspeed using various data related to the propeller can be provided.

In addition, since the present invention predicts airspeed using a propeller performance analysis method, it is independent from the existing pitot-static pressure type airspeed measuring device, and thus, when used together, the reliability of the airspeed measuring device can be increased, and since there is no additional hardware, it can contribute to weight and cost reduction.

In addition, according to the present invention, it can be utilized as a redundancy that serves as a backup function in the event of a failure of the primary equipment, the pitot-static pressure type airspeed measuring device.

In addition, the present invention provides an airspeed estimation model capable of accurately predicting speed without increasing error even in a low-speed range of 0 to 50 km/h.

The airspeed estimation device (100) according to the present invention can receive information during flight from a propeller-driven aircraft, calculate the airspeed in real time, and provide it to a pilot or a flight control computer.

The input information may be sensing values measured by sensors mounted on the aircraft, and examples thereof include atmospheric temperature, atmospheric pressure, atmospheric density (atmospheric density can be calculated if atmospheric temperature and atmospheric pressure are known), propeller RPM, propeller blade angle, and propeller shaft power.

Of these, propeller shaft power may be the most important variable among the input information.

Examples of methods for driving a propeller include the electric motor method, reciprocating engine method, and turboprop engine method.

The electric power sources for electric motors include batteries, fuel cells, and hybrid methods combining batteries and engines.

The system configuration of a propeller-driven aircraft including a battery, which is the most commonly used electric power source, is as shown in Fig. 2.

Figure 2 is an example of the configuration of a propeller-driven aircraft.

Propeller-driven aircraft fly by transmitting power from a battery to a motor through an ESC (Electronic Speed Controller), and transmitting the rotational force generated by the motor that received the power to the propeller, thereby rotating the propeller.

By measuring the electric power input from the battery to the ESC (motor controller), the input electric power can be determined.

: Motor Efficiency

: Motor controller efficiency

: Electric power

: Axial power

When using a reciprocating engine or turboprop engine to drive the propeller, the shaft power can be calculated by measuring the torque at the propeller connecting shaft.

: Rotation speed

: Talk

The airspeed estimation device (100) can accurately predict airspeed when the propeller direction and rotation axis are coaxial.

Figure 3 is a diagram explaining the force and speed at the blade cross section.

In Fig. 3, the relationship between the velocity and force acting on a representative blade cross-section is explained to analyze the propeller.

In Fig. 3, the speed, power, and angle of the propeller are defined in the direction of cross-section with respect to the propeller travel direction.

The power is, can be defined through .

is the thrust (force generated by the propeller, direction of propeller movement) acting on the element.

is the torque acting on the element.

is the tangential force acting on the element (a force acting in the direction opposite to the propeller rotation).

is the element drag (velocity (It is the opposite direction to the rotation with the directional force).

Silver element lift (velocity) (The blade is pushed upward by a vertical force.)

The speed is, can be defined through .

is the airspeed (propeller forward speed).

is the speed due to propeller rotation at radius r.

is the induced speed (the speed generated by the propeller wake).

Is It is the sum of the propeller's forward speed and rotational speed.

is the resultant relative velocity. ( , )

The angle is can be defined through .

is the angle of attack (speed (angle from the blade cross-section to the demonstration line).

is the blade pitch angle (the angle from the horizontal line in the forward direction of the propeller to the blade cross-section chord line).

is the flow angle (velocity in the vertical line of the forward direction of the propeller) ) is the angle.

Figure 4 is a diagram to explain the relationship between speed and angle in the blade cross section.

FIG. 4 shows the velocity and angle relationships added in the calculation process according to the present invention in the velocity and angle definitions described in FIG. 3.

The speed in Fig. 4 is, In addition, can be defined by adding .

is the induction speed ( ) is the axial component.

is the induction speed ( ) is the tangential component.

is the resultant speed ( ) is the axial component.

is the resultant speed ( ) is the tangential component.

The angle in Fig. 4 is In addition, can be defined through .

is the induced angle.

is the inflow angle.

is a dummy variable ( ).

Nomenclature used in the present invention is as follows.

In addition, the Subscripts used in the present invention are as follows.

Lock (Lock, C. N. A, Graphical Method of Calculating the Performance of an Airscrew, British A.R.C., Report and Memoranda 1675, 1935.) developed a single-element method to express the thrust and shaft power of a propeller in terms of the equivalent lift coefficient, equivalent drag coefficient, and integration coefficient at a single propeller blade reference cross-section located at 0.7R of the blade, in order to shorten the calculation time of the blade-element theory.

The equivalent lift coefficient and equivalent drag coefficient of a reference cross-section of a propeller blade are values representing the entire propeller, which are different from the actual lift coefficient and drag coefficient of the cross-section at the same location of the blade, and can be obtained from thrust and power data for the advance ratio of the propeller measured through testing.

In the present invention, a propeller performance analysis method is proposed that combines a parameter-based induced speed calculation method based on Lock's method.

The propeller performance analysis method according to the present invention can quickly predict thrust and shaft power at any blade angle and advance ratio by inputting chord and pitch angle at a reference cross-section of a propeller blade, and advance ratio, thrust coefficient and power coefficient data of the propeller constructed from a wind tunnel test, without requiring three-dimensional shape data of the blade or aerodynamic data of cross-sections in the radial direction.

The airspeed estimation device (100) can utilize the propeller performance analysis method to predict airspeed.

The airspeed estimation device (100) can recognize the shaft power of the propeller during flight, calculate the advance ratio using a propeller performance analysis method, and calculate the airspeed from an equation defining the advance ratio.

The airspeed estimation device (100) can calculate propeller equivalent aerodynamic force data.

To calculate the airspeed during flight, the equivalent lift coefficient and equivalent drag coefficient at the propeller blade reference cross-section are required.

The airspeed estimation device (100) inputs propeller geometric data, such as diameter, number of blades, chord length at 0.7R position, and pitch angle, and propeller performance data, such as thrust coefficient and power coefficient for advance ratio, constructed from wind tunnel tests, and can obtain equivalent lift coefficient and equivalent drag coefficient as propeller equivalent aerodynamic data.

The airspeed estimation device (100) can use the obtained equivalent lift coefficient and equivalent drag coefficient as a polynomial that is a function of the angle of attack in the airspeed calculation process.

In the process of creating propeller equivalent aerodynamic data as a function of angle of attack, the airspeed estimation device (100) can receive basic shape data of the propeller and propeller performance data.

The basic shape data of the propeller is propeller diameter , number of blades , of the blade Code in location , and blade pitch angle It could be.

Propeller performance data is forward ratio , thrust coefficient , and power coefficient It could be. Forward ratio can be obtained through wind tunnel testing or CFD calculations.

The airspeed estimation device (100) can create an equivalent lift coefficient and an equivalent drag coefficient polynomial, obtained through input data, as a function of the angle of attack.

The airspeed estimation device (100) is a device that can estimate the number of blades. , propeller radius , cross-sectional location based on the propeller blade ( , ) Code in Wow blade pitch angle ( and at ) can be read ( (is the radial length).

The airspeed estimation device (100) is a device that can estimate the number of blades. , code , radial length Using solidity ( can be calculated.

The airspeed estimation device (100) can read propeller performance data.

Advance rate , thrust coefficient , power coefficient is given as a result of wind tunnel test.

The airspeed estimation device (100) is solidity And propeller performance data can be input and calculated using the Newton-Rapson method.

The airspeed estimation device (100) is a dummy variable of the range of can be determined.

The airspeed estimation device (100) is Through, dummy variable The residual is set as a parameter of the Newton-Rapson method. Repeat the calculation until it becomes as follows.

is the inflow angle, is the induced angle.

In this calculation can be determined as

The airspeed estimation device (100) is a relative resultant velocity Axial component of , tangential component can be calculated.

Advance ratio and Is and can be expressed as

This If we organize it as am( is the circumference of the circle).

Axial component Is can be expressed as

Tangential component Is can be expressed as

relative resultant velocity Is can be expressed as

The airspeed estimation device (100) is a flow angle can be calculated.

The airspeed estimation device (100) is a blade pitch angle flow angle in By subtracting the angle of attack can be calculated.

The airspeed estimation device (100) is an equivalent lift coefficient , equivalent drag coefficient can be calculated.

Equivalent lift coefficient , equivalent drag coefficient is the input value, the forward ratio , thrust coefficient , power coefficient can be calculated from

[Formula 1]

,

The airspeed estimation device (100) is an induced angle can be calculated.

The airspeed estimation device (100) is an induction speed dummy variable without calculating Induced angle from geometric relationship can be calculated directly.

The airspeed estimation device (100) is a dummy variable flow angle in By subtracting the induced angle can be calculated.

The airspeed estimation device (100) is a tip loss factor can be calculated.

The airspeed estimation device (100) is an equivalent lift coefficient and derived from vortex theory The difference can be defined as residual.

The airspeed estimation device (100) is a dummy variable in the next iteration can be obtained.

The airspeed estimation device (100) is It can be calculated repeatedly up to .

The airspeed estimation device (100) calculates the residual value for each iteration. Compared to, If it is smaller, it can be judged as convergence and the calculation can be terminated.

The airspeed estimation device (100) calculates , Received each Create a polynomial as a function of .

[Formula 2]

The airspeed estimation device (100) can calculate the airspeed during flight.

Data required to calculate airspeed include propeller operating conditions such as air temperature, air pressure, propeller RPM, propeller blade angle, and propeller shaft power.

The propeller shaft power can be obtained by considering the motor efficiency and motor controller efficiency from the electric power input to the motor controller (or motor).

The airspeed estimation device (100) uses data on propeller operating conditions and polynomials of equivalent lift coefficient and equivalent drag coefficient to calculate the advance ratio corresponding to the input power coefficient. can be found by iterative calculation.

The airspeed estimation device (100) can receive input information regarding propeller operating conditions, such as air temperature, air pressure, propeller RPM, propeller blade angle, and propeller shaft power.

Propeller shaft power can be calculated by considering the motor efficiency and motor controller efficiency from the electric power input to the motor controller (or motor).

The airspeed estimation device (100) uses input information, an equivalent lift coefficient polynomial, and an equivalent drag coefficient polynomial to estimate the power coefficient. The corresponding advance ratio can be found by iterative calculation (Newton-Rapson method).

The airspeed estimation device (100) is a shaft power As given, it can be converted into a power coefficient form.

: air density

: rotation frequency (revolution per second)

: Propeller diameter

: Axial power

: Input shaft power coefficient

The airspeed estimation device (100) can calculate the inner loop and outer loop twice using the Newton-Rapson method.

The airspeed estimation device (100) is a forward speed Calculate the Outer Loop using dummy variable as a variable Inner Loop can be calculated using as a variable.

The airspeed estimation device (100) is, in the outer loop, the range of the advance ratio. can be determined (Newton-Rapson method for ).

The outer loop of the Newton-Rapson method has a parameter called the forward ratio. It becomes.

The airspeed estimation device (100) is, in the inner loop, the range of the dummy variable. can be determined (Newton-Rapson method for ).

Advance rate The inner loop of the Newton-Rapson method has a dummy variable parameter It can be.

The airspeed estimation device (100) is a relative resultant velocity Axial component of , tangential component can be calculated.

The airspeed estimation device (100) is a flow angle Calculate .

The airspeed estimation device (100) is a tip loss factor can be calculated.

The airspeed estimation device (100) is an angle of attack can be calculated.

The airspeed estimation device (100) is an angle of attack Equivalent lift coefficient corresponding to and equivalent drag coefficient , can be calculated from the equivalent lift coefficient and equivalent drag coefficient polynomials.

[Formula 2]

The airspeed estimation device (100) is an induced angle can be calculated.

The airspeed estimation device (100) can calculate the residual.

The airspeed estimation device (100) is a dummy variable can be updated.

The airspeed estimation device (100) is It can be repeatedly calculated up to .

The airspeed estimation device (100) calculates the parameter (advance ratio) when the inner loop converges. Power coefficient corresponding to can be calculated.

,

The airspeed estimation device (100) is an input power coefficient and The difference can be calculated as the residual.

The airspeed estimation device (100) is a parameter (advance ratio) can be updated.

Through this, the airspeed estimation device (100) calculates the parameters in the next iteration. can be obtained.

The airspeed estimation device (100) is It can be repeated up to (Outer Loop).

The airspeed estimation device (100) calculates the residual value for each iteration. Compared to If it is smaller, it is considered convergence and the calculation can be terminated.

The airspeed estimation device (100) is a converged parameter From air speed Calculate .

[Formula 4]

M. Selig of UIUC has conducted wind tunnel performance measurements on a variety of small propellers from various manufacturers used in RC airplanes and small UAVs and has published the test results (Brandt, J. B., Deters, R. W., Ananda, G. K., Dantsker, O. D., and Selig, M., UIUC Propeller Data Site, https://m-selig.ae.illinois.edu/props/propDB.html.).

To verify the developed calculation method, it is necessary to perform calculations using the APC FF 4.2x4 model among the UIUC propeller data and compare it with the wind tunnel test results.

Figure 5 is a drawing illustrating the external appearance of the APC FF 4.2x4 propeller.

The APC FF 4.2x4 propeller of Figure 5 may have two fixed-pitch blades and a diameter of 10.7 cm.

The geometry data of the APC FF 4.2x4 propeller in the UIUC database is the radial length of the blades, which is non-dimensionalized. , non-dimensionalized code , blade pitch angle is given as follows.

In the calculation Uses the code and blade pitch angle values in .

Performance data for the APC FF 4.2x4 propeller in the UIUC database, the first column is the advance ratio ( The second column gives the thrust coefficient, the third column gives the power coefficient, and the fourth column gives the efficiency value.

Here, there is data for three cases of propeller rotation speeds: 6,000 RPM, 8,000 RPM, and 10,000 RPM. In this calculation, the thrust coefficient and power coefficient at 10,000 RPM are used as input data.

In calculating propeller equivalent aerodynamic data, the airspeed estimation device (100) reads blade data.

The airspeed estimation device (100) reads and stores propeller performance data.

and

The airspeed estimation device (100) calculates using the Newton-Rapson method.

The airspeed estimation device (100) is a parameter The boundary values and convergence criteria are set as follows.

Figure 6 is a graph comparing the angle of attack and the equivalent lift coefficient.

Figure 6 shows the results of calculating the lift coefficient.

The x-axis of Fig. 6 is the angle of attack , and the y-axis represents the lift coefficient.

The marks are the original calculated values, and the result of fitting them to the second-order equation of the angle of attack is shown as a solid line in Fig. 6.

The equivalent lift coefficient second-order polynomial is as follows.

Figure 7 is a graph comparing the angle of attack and the equivalent drag coefficient.

Figure 7 shows the results of calculating the equivalent drag coefficient.

The x-axis of Fig. 7 is the angle of attack , and the y-axis represents the equivalent drag coefficient.

The marks are calculated values, and the result of fitting them to the second-order equation of the angle of attack is shown as a solid line in Fig. 7.

The equivalent drag coefficient second-order polynomial is as follows.

The airspeed estimation device (100) can use the second-order polynomial of the equivalent lift coefficient and the second-order polynomial of the equivalent drag coefficient together with the propeller operating conditions to calculate the airspeed.

The airspeed estimation device (100) can input the shaft power value of the APC FF 4.2x4 propeller and calculate the corresponding airspeed according to the following process.

The airspeed estimation device (100) reads the propeller operating conditions.

Propeller operating conditions can include atmospheric temperature, atmospheric pressure, propeller RPM, and propeller blade pitch angle.

The airspeed estimation device (100) reads the input power coefficient.

The airspeed estimation device (100) calculates using a double Newton-Rapson method.

The airspeed estimation device (100) is a forward speed Calculation Loop for Newton-Rapson method for ) performs the Outer Loop.

define

The airspeed estimation device (100) is a dummy variable Calculation Loop for Newton-Rapson method for ) performs the inner loop.

define

The airspeed estimation device (100) is a forward speed Dummy variables inside the calculation loop You can run a calculation loop.

The airspeed estimation device (100) is given Dummy variable for As the calculation converges, Dummy variable for The calculation was performed and finally converged. can be found.

The airspeed estimation device (100) is converged From airspeed (airspeed) Calculate .

[Formula 4]

Figure 8 shows the predicted airspeed results (y-axis) for a given shaft power (x-axis).

In Fig. 8, the shaft power value was used as input data to include the power coefficient range measured in the wind tunnel test at UIUC.

Figure 8 shows the calculated airspeed (y-axis) for each input power on the x-axis.

In Fig. 8, the marks are the wind tunnel test data of UIUC, and the solid line is the result of this calculation method, which can be seen to be very good agreement with the wind tunnel test data.

The airspeed estimation device (100) can make very accurate predictions even at speeds below 50 km/h, where pitot-static type airspeed measuring devices show inaccurate results.

Below, FIG. 9 describes in detail the work flow of the air speed estimation device (100) according to embodiments of the present invention.

The airspeed estimation method according to the present embodiment can be performed by an airspeed estimation device (100).

FIG. 9 is a flow chart illustrating an airspeed estimation method using a propeller performance analysis method according to an embodiment of the present invention.

First, the airspeed estimation device (100) is associated with a propeller-driven aircraft and calculates an equivalent lift coefficient and an equivalent drag coefficient as propeller equivalent aerodynamic data (910). Step (910) may be a process of calculating an equivalent lift coefficient and an equivalent drag coefficient applied to the propeller using propeller basic shape data and propeller performance data.

The lift coefficient is the dimensionless component of the force perpendicular to the flow acting on an object placed in a flow, i.e., lift. It can be determined by the cross-sectional shape of the object parallel to the flow, the angle between the object and the flow, the Reynolds number, and the Mach number.

The drag coefficient is a coefficient that represents the drag force received by an object moving in a flow. It can be a dimensionless constant used when quantifying the resistance received by an object in a flow.

In calculating the equivalent lift coefficient and the equivalent drag coefficient, the airspeed estimation device (100) can read blade data of the blades constituting the propeller.

For example, the airspeed estimation device (100) is a propeller diameter , number of blades , of the blade Code in location , and blade pitch angle The basic shape data of the propeller can be read.

Additionally, the airspeed estimation device (100) can read propeller performance data of the propeller.

For example, the airspeed estimation device (100) is initially given a forward speed , thrust coefficient , and power coefficient You can read the propeller performance data of the above thrust coefficient. , and power coefficient can be obtained through wind tunnel testing or CFD calculations.

In addition, the airspeed estimation device (100) uses the Newton-Rapson method, which inputs the blade data and the propeller performance data, to estimate the equivalent lift coefficient. and the equivalent drag coefficient can be calculated.

The Newton-Rapson method is an iterative solution method that finds approximate values by infinitely reducing the interval a≤x≤b that contains the solution when the real roots of an n-th order equation cannot be found by factoring or calculations such as the root formula.

The airspeed estimation device (100) satisfies [Formula 1] to obtain the equivalent lift coefficient and the equivalent drag coefficient can be calculated.

[Formula 1]

,

Here, is 'solidity', is the 'resultant relative velocity', is 'rotation rate', is the 'propeller radius', is a 'dimensionless length', is the 'flow angle', is the 'thrust coefficient', is the 'power coefficient'.

In addition, the airspeed estimation device (100) writes each of the equivalent lift coefficient and the equivalent drag coefficient as an equivalent lift coefficient polynomial and an equivalent drag coefficient polynomial, which are functions of the angle of attack (920). Step (920) may be a process of writing the calculated equivalent lift coefficient and the equivalent drag coefficient as polynomials by expressing them as functions of the angle of attack.

The angle of attack can refer to the angle between the baseline (chord line) of the cut surface of the airplane's wing and the airflow.

The airspeed estimation device (100) satisfies [Formula 2] and the equivalent lift coefficient and the equivalent drag coefficient , the angle of reception can be written as a function of .

[Formula 2]

Continuing, the airspeed estimation device (100) estimates the airspeed of the aircraft during flight by finding a forward ratio corresponding to the input shaft power coefficient of the aircraft using the equivalent lift coefficient polynomial and the equivalent drag coefficient polynomial (930). Step (930) may be a process of calculating the forward ratio of the aircraft by the equivalent lift coefficient polynomial and the equivalent drag coefficient polynomial, and estimating the airspeed of the aircraft by the calculated forward ratio.

In estimating the airspeed, the airspeed estimation device (100) can receive the propeller operating conditions of the propeller.

The airspeed estimation device (100) can receive inputs such as air temperature, air pressure, propeller RPM, and propeller blade angle as propeller operating conditions.

Additionally, the airspeed estimation device (100) can calculate the input shaft power coefficient.

The airspeed estimation device (100) calculates the axial power of the aircraft according to [Formula 3]. By expressing it in the form of a power coefficient, the input shaft power coefficient can be calculated.

[Formula 3]

: air density

: rotation frequency (revolution per second)

: Propeller diameter

: Axial power

: Input shaft power coefficient

Continuing, the airspeed estimation device (100) can perform an inner loop and an outer loop by the Newton-Rapson method using the propeller operating conditions and the input shaft power coefficient as inputs.

The airspeed estimation device (100) can calculate the inner loop and outer loop twice using the Newton-Rapson method. The airspeed estimation device (100) can calculate the forward ratio Calculate the Outer Loop using dummy variable as a variable Inner Loop can be calculated using as a variable.

The outer loop of the Newton-Rapson method has a parameter called the forward ratio. It can be. Forward ratio The inner loop of the Newton-Rapson method has a dummy variable parameter It can be.

Afterwards, the airspeed estimation device (100) calculates the forward speed by repeatedly performing the Inner Loop and the Outer Loop. can converge to a certain value.

The above advance ratio After the constant value converges, the airspeed estimation device (100) satisfies [Formula 4] and the advance ratio converges to a constant value. From air speed can be estimated.

[Formula 4]

Above is the 'rotation frequency', and the above can be the 'propeller diameter'.

According to one embodiment of the present invention, in an aircraft propelled by a propeller connected to an electric motor, an airspeed estimation method and device using a propeller performance analysis method for estimating airspeed using various data related to the propeller can be provided.

In addition, since the present invention predicts airspeed using a propeller performance analysis method, it is independent from the existing pitot-static pressure type airspeed measuring device, and thus, when used together, the reliability of the airspeed measuring device can be increased, and since there is no additional hardware, it can contribute to weight and cost reduction.

In addition, according to the present invention, it can be utilized as a redundancy that serves as a backup function in the event of a failure of the primary equipment, the pitot-static pressure type airspeed measuring device.

In addition, the present invention provides an airspeed estimation model capable of accurately predicting speed without increasing error even in a low-speed range of 0 to 50 km/h.

The method according to the embodiment may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the medium may be those specially designed and configured for the embodiment or may be those known to and available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands such as ROMs, RAMs, flash memories, etc. Examples of the program commands include not only machine language codes generated by a compiler but also high-level language codes that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiment, and vice versa.

The software may include a computer program, code, instructions, or a combination of one or more of these, which may configure a processing device to perform a desired operation or may independently or collectively command the processing device. The software and/or data may be permanently or temporarily embodied in any type of machine, component, physical device, virtual equipment, computer storage medium or device, or transmitted signal waves, for interpretation by the processing device or for providing instructions or data to the processing device. The software may also be distributed over network-connected computer systems, and stored or executed in a distributed manner. The software and data may be stored on one or more computer-readable recording media.

Although the embodiments have been described with limited drawings as described above, those skilled in the art can apply various technical modifications and variations based on the above. For example, even if the described techniques are performed in a different order than the described method, and/or the components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or are replaced or substituted by other components or equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are also included in the scope of the claims described below.

100 : Airspeed Estimation Device
110 : Calculation Department
120 : Writing Department
130 : Processing Unit

Claims (13)

In relation to a propeller-driven aircraft, a step of calculating an equivalent lift coefficient and an equivalent drag coefficient as propeller equivalent aerodynamic data;
A step of writing the above equivalent lift coefficient and the above equivalent drag coefficient as an equivalent lift coefficient polynomial and an equivalent drag coefficient polynomial, which are functions of the angle of attack, respectively; and
A step of estimating the airspeed of the aircraft during flight by finding the advance ratio corresponding to the input shaft power coefficient of the aircraft using the equivalent lift coefficient polynomial and the equivalent drag coefficient polynomial.
A method for estimating airspeed using a propeller performance analysis method, including: In the first paragraph,
The above calculation steps are:
A step of reading blade data of blades constituting the above propeller;
A step of reading propeller performance data of the above propeller; and
By the Newton-Rapson method using the above blade data and the above propeller performance data as input, the equivalent lift coefficient and the equivalent drag coefficient Steps to calculate
A method for estimating airspeed using a propeller performance analysis method, including: In the second paragraph,
The above equivalent lift coefficient and the equivalent drag coefficient The steps to calculate are:
The equivalent lift coefficient above satisfies [Formula 1] and the equivalent drag coefficient Steps to calculate
[Formula 1]
,


- is 'solidity', is the 'resultant relative velocity', is 'rotation rate', is the 'propeller radius', is a 'dimensionless length', is the 'flow angle', is the 'thrust coefficient', is the 'power factor' -
A method for estimating airspeed using a propeller performance analysis method, including: In the third paragraph,
The steps for writing the above are:
Satisfying [Formula 2], the equivalent lift coefficient and the equivalent drag coefficient , the angle of reception Steps to write as a function of
[Formula 2]


A method for estimating airspeed using a propeller performance analysis method, including: In paragraph 4,
The step of estimating the airspeed of the above aircraft during flight is as follows:
A step for receiving propeller operating conditions of the above propeller;
A step of calculating the above input shaft power coefficient;
A step of performing an inner loop and an outer loop by the Newton-Rapson method using the above propeller operating conditions and the above input shaft power coefficient as inputs; and
By repeating the above Inner Loop and the above Outer Loop, the forward ratio Step to converge to a certain value
A method for estimating airspeed using a propeller performance analysis method, including: In paragraph 5,
The step of estimating the airspeed of the above aircraft during flight is as follows:
The above advance ratio converges to a constant value by satisfying [Formula 4] From air speed Steps to estimate
[Formula 4]

- Above is the 'rotation frequency', and the above is 'propeller diameter' -
A method for estimating airspeed using a propeller performance analysis method, which further includes: In relation to a propeller-driven aircraft, a calculation unit that calculates the equivalent lift coefficient and the equivalent drag coefficient as propeller equivalent aerodynamic data;
A writing unit that writes the above equivalent lift coefficient and the above equivalent drag coefficient as an equivalent lift coefficient polynomial and an equivalent drag coefficient polynomial, which are functions of the angle of attack, respectively; and
A processing unit that estimates the airspeed of the aircraft during flight by finding the advance ratio corresponding to the input shaft power coefficient of the aircraft using the equivalent lift coefficient polynomial and the equivalent drag coefficient polynomial.
An airspeed estimation device using a propeller performance analysis method, including: In Article 7,
The above calculation part,
The blade data of the blades constituting the propeller are read, the propeller performance data of the propeller is read, and the equivalent lift coefficient is obtained by the Newton-Rapson method using the blade data and the propeller performance data as inputs. and the equivalent drag coefficient Calculating
Airspeed estimation device using propeller performance analysis method. In Article 8,
The above calculation part,
The equivalent lift coefficient above satisfies [Formula 1] and the equivalent drag coefficient Calculating
[Formula 1]
,


- is 'solidity', is the 'resultant relative velocity', is 'rotation rate', is the 'propeller radius', is a 'dimensionless length', is the 'flow angle', is the 'thrust coefficient', is the 'power factor' -
Airspeed estimation device using propeller performance analysis method. In Article 9,
The above writing department,
Satisfying [Formula 2], the equivalent lift coefficient and the equivalent drag coefficient , the angle of reception Written as a function of
[Formula 2]


Airspeed estimation device using propeller performance analysis method. In Article 10,
The above processing unit,
The propeller operating conditions of the propeller are input, the input shaft power coefficient is calculated, and the inner loop and outer loop are performed by the Newton-Rapson method using the propeller operating conditions and the input shaft power coefficient as inputs, and the advance ratio is calculated by repeatedly performing the inner loop and the outer loop. Converging to a certain value
Airspeed estimation device using propeller performance analysis method. In Article 11,
The above processing unit,
The above advance ratio converges to a constant value by satisfying [Formula 4] From air speed Estimating
[Formula 4]

- Above is the 'rotation frequency', and the above is 'propeller diameter' -
Airspeed estimation device using propeller performance analysis method. A computer-readable recording medium having recorded thereon a program for executing any one of the methods of claims 1 to 6.