CN105718727A - Stratospheric airship flight performance parameter estimation method and system - Google Patents

Abstract

The invention relates to a stratospheric airship flight performance parameter estimation method and system. The stratospheric airship flight performance parameter estimation method comprises the steps: enabling an airship in a steady circling flight state; acquiring ground velocity, attitude angle information and position information of the airship; estimating flight performance parameters of the airship according to the ground velocity, attitude angle information and position information of the airship. According to the stratospheric airship flight performance parameter estimation method and system, which are provided by the invention, the accurate flight performance parameters, such as horizontal wind velocity, wind direction, airspeed, steady circling radius, circling period, circling angular speed, sideslip angle, attack angle and the like, can be computed by utilizing the ground velocity, position information and attitude angle information given out by a navigation system of the airship under an upper thin atmosphere environment; furthermore, the process is simple and is easy to implement; as long as main propeller rotation speed and yaw controlled quantity are constant, the airship can start the circling flight state; due to the circling flight, the airship has a constant altitude, and the wind speed and the wind direction are also constant, so that the airship is located under a constant wind field, and airship flight performance parameter estimation errors are reduced.

Description

Method and system for estimating flight performance parameters of stratospheric airship

Technical Field

The invention relates to the technical field of aviation measurement and control, in particular to a method and a system for estimating flight performance parameters of an airship on an stratosphere.

Background

In recent years, driven by the demands of regional atmospheric environment monitoring, disaster prevention and reduction, high-resolution real-time monitoring, early warning, missile defense, anti-terrorism, regional communication and the like, stratospheric airships attract general attention of various countries, and major countries such as the united states, japan, russia, korea, european union, china and the like continuously start related research plans and begin deeper research and development work. Some countries have begun to undertake stratospheric airship prototype development and flight tests.

The flight test is an important basis for checking whether flight performance indexes meet requirements and whether the overall design of the airship is reasonable. At present, stratospheric airships are in an exploration stage, the period for carrying out one-time test flight is long, and the cost are also high, so that the flight characteristic parameters as many as possible are expected to be estimated through one-time flight test. However, in the current stage, the flight performance parameters or flight characteristic parameters of the stratospheric airship are obtained from flight tests, and several fundamental difficulties exist: first, the relative wind speed or true wind speed cannot be measured. Due to the particularity of the stratosphere environment, relative wind speed information (airspeed, attack angle and sideslip angle) or true wind speed information during flight cannot be obtained in real time at present. Such information is critical to the identification of the underlying flight characteristics parameters, since the dynamics of a stratospheric airship are related to its speed of movement relative to the atmosphere, and not to the speed of movement relative to the ground. Secondly, the stratospheric airship is in a wind field environment. The stratospheric wind field is not constant, the wind speed/direction changes with the change of the height, and only when the change of the height is small, the wind field can be approximately regarded as the constant wind field. Because the stratospheric airship is large in size and low in movement speed, the dynamic characteristics of the stratospheric airship are greatly influenced by wind. Different from a low-altitude airship which can select a windless environment to carry out a flight test, the flight test of the stratospheric airship cannot isolate the influence of wind. In case wind speed is not measurable, the difficulty of parameter estimation is exacerbated. Thirdly, some defects of the stratospheric test airship aggravate the difficulty of maintaining the flight working condition. For example, due to the difficulty in adjusting the pitch attitude, it is difficult for an airship in a stratosphere to maintain constant-height flight, once the thrust or airspeed of the airship changes, the altitude will drift, and the altitude drift often causes the pressure of the airship body to change, thereby generating an inflation and deflation effect, and changing the quality parameters of the airship. However, maintaining a specific flight condition is the key to identifying the flight characteristic parameters through experimental methods.

The dilemma of evaluating flight performance parameters through a test method is illustrated by taking wind speed estimation as an example. It has been thought that wind speed can be extracted by the following method: firstly, the airship is in an unpowered flying state, and at the moment, the ground speed given by a navigation system such as a GPS is the wind speed. Since the stratospheric wind field has better time stability, the wind speed can be considered to be kept constant in the subsequent flight performance evaluation test. However, in fact, the stratospheric wind field changes with the altitude in a layered manner, once the power is turned on, due to the difficulty of adjusting the pitching attitude, the airship can hardly be kept in a zero-attack-angle flying state, the flying altitude can drift, and once the altitude change is coupled with the inflation and deflation, the altitude drift can easily exceed 200 m. At this time, the wind field at the new altitude is not already the wind field when flying before.

Mathematically, the problem of experimental identification of flight characteristic parameters of the stratospheric airship can be summarized as follows: on the premise that a wind field and airspeed are unknown, how to carry out experimental design and identification algorithm design enables the expected flight characteristic parameters to be estimated only by utilizing other information such as moving tracks, speeds, attitudes and the like relative to the ground. At the stratosphere and above, no method in the prior literature can directly provide real-time horizontal wind speed and direction, airspeed, steady-state hover radius, hover period, hover angle rate, sideslip angle and attack angle information required by evaluating flight performance for the stratosphere airship.

Disclosure of Invention

The invention aims to solve the technical problem of accurately estimating the flight performance parameters of the stratospheric airship.

To this end, the invention provides a method for estimating flight performance parameters of an airship on a stratosphere, which comprises the following steps:

bringing the airship into a stable hover flight state;

acquiring ground speed, attitude information and position information of the airship;

and estimating the flight performance parameters of the airship according to the ground speed, the attitude information and the position information of the airship.

Preferably, said bringing said airship into stable hover flight condition comprises:

fixing the rotation speed and the yaw control quantity of a main propeller of the airship to enable the airship to enter a hovering flight state; and when the fluctuation value of the flying height of the airship is smaller than a preset value, the airship is considered to enter a stable hovering flying state.

Preferably, the flight performance parameters of the airship comprise wind speed, airspeed, yaw handling performance parameters and longitudinal and transverse stability performance parameters.

Preferably, the calculation process of the wind speed and the airspeed comprises the following steps:

establishing a first circular equation according to the relation among the wind speed, the airspeed and the ground speed:

${(V_x-W_x)}^2+{(V_y-W_y)}^2=V_a^2$

wherein (V)_x,V_y) The ground speed (W) measured by the ship-borne navigation system_x,W_y) For the wind speed to be estimated, V_aIs the airspeed to be estimated;

using a plurality of ground speeds (V) measured during hover flight_xi,V_yi) I 1,2, …, the wind speed to be estimated (W) is calculated by a circle fitting algorithm_x,W_y) And airspeed V to be estimated_a。

Preferably, the wind speed (W) to be estimated is calculated by a circle fitting algorithm_x,W_y) And airspeed V to be estimated_aComprises the following steps:

A. passing through a plurality of ground speeds (V)_xi,V_yi) I 1,2, … n, defining intermediate parameters

a＝2W_x，b＝2W_y，c＝V_a ²-(W_x ²+W_y ²)

Constructing a least square equation;

$\left[\begin{array}{ccc}{V}_{x1}& V_{y1}& 1\\ V_{x2}& V_{y2}& 1\\ .& .& .\\ .& .& .\\ .& .& .\\ V_{xn}& V_{yn}& 1\end{array}\right]\left[\begin{array}{c}a\\ b\\ c\end{array}\right]=\left[\begin{array}{c}{V_{x1}}^2+{V_{y1}}^2\\ {V_{x2}}^2+{V_{y2}}^2\\ .\\ .\\ .\\ {V_{xn}}^2+{V_{yn}}^2\end{array}\right]$

B. solving a least square equation to calculate a, b and c;

C. calculating the wind speed (W) from a, b, c_x,W_y) Airspeed V_a。

$W_x=\frac{a}{2},W_y=\frac{b}{2},V_a=\sqrt{c+{W_x}^2+{W_y}^2}$

Preferably, the yaw handling performance parameters include: the circling radius, the circling period and the circling angular speed of the airship; the calculation process of the yaw handling performance parameters comprises the following steps:

establishing a second circular equation according to the hovering trajectory of the airship

[(x-W_xt)-x₀₀]²+[(y-W_yt)-y₀₀]²＝R²

Wherein (W)_x,W_y) Is the wind speed, (x)₀₀,y₀₀) As the position of the circle center at the initial moment, (x, y) is the shipborne navigationThe airship position measured by the system, R is the hovering radius of the airship to be estimated, and t is time;

selecting a series of points (x) from the hover trajectory of the airship_i,y_i,t_i) And i is 1,2 and …, and calculating the hover radius R of the airship to be estimated through a circle fitting algorithm.

Preferably, the spiral period and the spiral angular velocity are calculated by the following formulas:

$\mathrm{\ω}=\frac{V_a}{R}$

$T_{circle}=\frac{2\mathrm{\π}}{\mathrm{\ω}}$

where ω is the spiral angular rate, T_circleIs the period of the spiral.

Preferably, the longitudinal and lateral stability performance parameters comprise an average sideslip angle, an instantaneous sideslip angle, an average angle of attack, and an instantaneous angle of attack of the airship;

the average and instantaneous sideslip angles of the airship are calculated by the following formulas:

$\stackrel{\‾}{\mathrm{\β}}={\sin }^{-1}\left(\frac{{\stackrel{\‾}{V}}_{a,yb}}{V_a}\right)$

${\mathrm{\β}}_i={\sin }^{-1}\[\frac{{\left(V_{a,yb}\right)}_i}{V_a}\]$

$\left[\begin{array}{c}{\stackrel{\‾}{V}}_{a,xb}\\ {\stackrel{\‾}{V}}_{a,yb}\\ {\stackrel{\‾}{V}}_{a,zb}\end{array}\right]=\frac{1}{m}{\left[\begin{array}{c}\underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,xb}\right)}_i\\ \underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,yb}\right)}_i\\ \underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,zb}\right)}_i\end{array}\right]}_i$

${\left[\begin{array}{c}{V}_{a,xb}\\ V_{a,yb}\\ V_{a,zb}\end{array}\right]}_i=A({\mathrm{\φ}}_i,{\mathrm{\θ}}_i,{\mathrm{\ψ}}_i){\left[\begin{array}{c}{V}_{a,x}\\ V_{a,y}\\ V_{a,z}\end{array}\right]}_i$

${\left[\begin{array}{c}{V}_{a,x}\\ V_{a,y}\\ V_{a,z}\end{array}\right]}_i={\left[\begin{array}{c}{V}_x\\ V_y\\ V_z\end{array}\right]}_i-\left[\begin{array}{c}{W}_x\\ W_y\\ 0\end{array}\right]$

wherein, ${\left[\begin{array}{ccc}{V}_{a,x}& V_{a,x}& V_{a,z}\end{array}\right]}_i^T$ is the component of airspeed in the navigation coordinate system; ${\left[\begin{array}{ccc}{V}_x& V_y& V_z\end{array}\right]}_i^T$ for the component of the ground speed in the navigation coordinate system, [ W ]_xW_y0]^TBeing the component of the wind speed in the navigational coordinate system, ${\left[\begin{array}{ccc}{V}_{a,xb}& V_{a,yb}& V_{a,zb}\end{array}\right]}_i^T$ the component of the airspeed on the body axis, A (φ)_i,θ_i,ψ_i) For the transformation matrix from the navigation coordinate system to the body axis system, m is the number of points on the spiral trajectory, i is 1,2, …, m,to average slip angle, β_iIs t_iThe angle of the side slip at the moment, ${\left[\begin{array}{ccc}{\stackrel{\‾}{V}}_{a,xb}& {\stackrel{\‾}{V}}_{a,yb}& {\stackrel{\‾}{V}}_{a,zb}\end{array}\right]}^T$ is the average value of the components of the airspeed on the body axis,is the average of the y-axis direction components of the airspeed on the body axis, (V)_a,yb)_iIs t_iThe time-of-day airspeed is the y-axis direction component on the body axis.

Preferably, the average and instantaneous angles of attack of the airship are calculated by the following formula:

$\stackrel{\‾}{\mathrm{\α}}={\tan }^{-1}\left(\frac{{\stackrel{\‾}{V}}_{a,zb}}{{\stackrel{\‾}{V}}_{a,xb}}\right)$ or $\stackrel{\‾}{\mathrm{\α}}\≈\frac{1}{m}\underset{i=1}{\overset{m}{\Σ}}{\mathrm{\θ}}_i$

${\mathrm{\α}}_i={\tan }^{-1}\frac{{\left(V_{a,bz}\right)}_i}{{\left(V_{a,bx}\right)}_i}$ Or ${\mathrm{\α}}_i\≈{\mathrm{\θ}}_i$

Wherein,in order to obtain an average angle of attack,is the average of the m pitch angles,is the average value of the space velocity on the z-axis direction component of the body axis,as the average of the x-axis component of the airspeed on the body axis, α_iIs t_iInstantaneous angle of attack at time, theta_iIs t_iPitch angle at time (V)_a,bz)_iIs t_iAverage value of z-axis direction component of space velocity on body axis at moment (V)_a,bx)_iIs t_iThe time-of-day airspeed is the average of the x-axis direction components on the body axis.

In another aspect, the present invention further provides a system for estimating flight performance parameters of an airship on a stratosphere, including: the device comprises a flight unit, an acquisition unit and an estimation unit;

the flying unit is used for enabling the airship to enter a stable hovering flying state;

the acquisition unit acquires the ground speed, attitude information and position information of the airship;

the estimation unit is used for estimating the flight performance parameters of the airship according to the ground speed, the attitude information and the position information of the airship.

The method and the system for estimating the flight performance parameters of the stratospheric airship can calculate the accurate flight performance parameters such as horizontal wind speed, wind direction, airspeed, yaw control performance (steady state hovering radius, hovering period, spiraling angle rate), longitudinal and transverse stability (sideslip angle and attack angle) and the like by utilizing the ground speed, position and attitude angle information given by a navigation system in the stratospheric airship in a high-altitude thin atmospheric environment; the process of the invention is simple and easy to realize, and the airship can enter the hovering flight state only by fixing the rotating speed and the yaw control quantity of the main propeller, and the hovering flight enables the airship to be at a fixed height, the wind speed and the wind direction to be fixed, so that the airship is in a constant wind field, and the error of estimating the flight performance parameters of the airship on the stratosphere is reduced.

Drawings

The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:

FIG. 1 is a schematic flow diagram illustrating a method of estimating stratospheric airship flight performance parameters in accordance with the present invention;

FIG. 2 is a schematic flow chart diagram illustrating one embodiment of a method of estimating stratospheric airship flight performance parameters of the present invention;

FIG. 3 is a schematic diagram showing the relationship among the ground speed, the wind speed and the airspeed vector in a wind field environment;

FIG. 4 shows a schematic view of the hover trajectory of a stratospheric airship in a wind farm environment;

FIG. 5 is a schematic diagram of a relationship between a cycloid locus cycloid and a circle in a wind field environment;

FIG. 6 is a schematic of the change in sideslip angle over time;

fig. 7 is a schematic view of the angle of attack as a function of time.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the present invention provides a method of estimating stratospheric airship flight performance parameters,

enabling the airship to enter a stable hovering flight state;

acquiring ground speed, attitude information and position information of an airship;

and estimating the flight performance parameters of the airship according to the ground speed, the attitude information and the position information of the airship.

As shown in fig. 2, wherein preferably bringing the airship into stable hover flight includes: fixing the main propeller rotation speed and the yaw control quantity of the airship to enable the airship to enter a hovering flight state; and when the fluctuation value of the flying height of the airship is smaller than a preset value, the airship is considered to enter a stable hovering flying state. Wherein preferably, the ground speed, attitude information and position information of the airship comprise: the ground speed, attitude information and position information of the airship are obtained through an onboard navigation system of the airship. In order to evaluate the flight performance of the airship, the flight performance parameters of the airship, which need to be acquired, include horizontal wind speed, wind direction, airspeed, yaw handling performance parameters and longitudinal and lateral stability performance parameters. The method is suitable for estimating flight performance parameters of the stratospheric airship.

When the airship enters into stable hovering flight, the airspeed is kept unchanged, the airship can automatically enter into a fixed-height flight state, and during fixed-height flight, the wind field can be approximately considered to be constant, and the wind speed and the wind direction are kept unchanged. After the airship flies in a hovering manner, the wind speed is (W)_x,W_y) The ground speed is (V)_x,V_y) The speed (airspeed) may also be considered constant at steady-state hover flight, with a magnitude of V_aSpecifically, the calculation process of the wind speed and the airspeed includes: as shown in fig. 3, a first circular equation is established according to the relation among the wind speed, the airspeed and the ground speed:

${(V_x-W_x)}^2+{(V_y-W_y)}^2=V_a^2---\left(1\right)$

wherein (V)_x,V_y) The ground speed (W) measured by the ship-borne navigation system_x,W_y) For the wind speed to be estimated, V_aIs the airspeed to be estimated;

using a plurality of ground speeds (V) measured during hover flight_xi,V_yi) I 1,2, …, the wind speed to be estimated (W) is calculated by a circle fitting algorithm_x,W_y) And airspeed V to be estimated_a。

The circle fitting algorithm is a method for estimating the position and the radius of a circle center through track points on a circle, and the curve equation of a general circle is

(x-x₀)²+(y-y₀)²＝R²(2)

Wherein x and y are the locus coordinates of the x direction and the y direction on the plane, and x₀、y₀The x coordinate and the y coordinate of the center of the circle, and R is the radius of the circle.

After being unfolded, is

$2x_{0}x+2y_{0}y+R^2-(x_0^2+y_0^2)=x^2+y^2---\left(3\right)$

Order to

$a=2x_0,b=2y_0,c=R^2-(x_0^2+y_0^2)---\left(4\right)$

Then there is

ax+by+c＝x²+y²(5)

Known track point (x)_i,y_i) I-1, 2, …, n, the least squares equation can be constructed from the above equation

$\left[\begin{array}{ccc}{x}_1& y_1& 1\\ x_2& y_2& 1\\ .& .& .\\ .& .& .\\ .& .& .\\ x_n& y_n& 1\end{array}\right]\left[\begin{array}{c}a\\ b\\ c\end{array}\right]=\left[\begin{array}{c}{x}_1^2+y_1^2\\ x_2^2+y_2^2\\ .\\ .\\ .\\ x_n^2+y_n^2\end{array}\right]---\left(6\right)$

After a, b and c are estimated, the circular curve parameters (circle center position and radius) can be obtained

$x_0=\frac{a}{2},y_0=\frac{b}{2},R=\sqrt{c+x_0^2+y_0^2}---\left(7\right)$

The first equation of the circle described in the formula (1) and the general equation of the circle described in the formula (2) have a parameter corresponding relationship of the ground speed (V)_x,V_y) Corresponding to the trajectory coordinates x, y, the wind speed (W) to be estimated_x,W_y) Corresponding to the coordinate x of the circle center₀、y₀Airspeed V to be estimated_aCorresponding to the radius R of the circle. The ground speed (V) can be passed according to the above steps_x,V_y) Calculating wind speed (W)_x,W_y) And space velocity V_a。

So the wind speed (W) to be estimated is calculated by a circle fitting algorithm_x,W_y) And airspeed V to be estimated_aComprises the following steps:

A. passing through a plurality of ground speeds (V)_xi,V_yi) I 1,2, … n, defining intermediate parameters

$a=2W_x,b=2W_y,c={V_a}^2-({W_x}^2+{W_y}^2)$

Constructing a least square equation;

$\left[\begin{array}{ccc}{V}_{x1}& V_{y1}& 1\\ V_{x2}& V_{y2}& 1\\ .& .& .\\ .& .& .\\ .& .& .\\ V_{xn}& V_{yn}& 1\end{array}\right]\left[\begin{array}{c}a\\ b\\ c\end{array}\right]=\left[\begin{array}{c}{V_{x1}}^2+{V_{y1}}^2\\ {V_{x2}}^2+{V_{y2}}^2\\ .\\ .\\ .\\ {V_{xn}}^2+{V_{yn}}^2\end{array}\right]$

B. solving a least square equation to calculate a, b and c;

C. calculating the wind speed (W) from a, b, c_x,W_y) AirspeedV_a。

$W_x=\frac{a}{2},W_y=\frac{b}{2},V_a=\sqrt{c+{W_x}^2+{W_y}^2}$

Thus, by measuring a plurality of ground speeds (V)_xi,V_yi) I 1,2, …, and a first equation of a circleThe wind speed (W) can be estimated_x,W_y) And space velocity V_aThe value of (c). The wind speed is a vector, and the direction of the wind speed can also be determined according to the positive and negative of the wind speed.

As shown in fig. 4 and 5, in a wind field environment, the curve of the spiral locus is a cycloid, rather than a closed circle curve, and the cycloid is equivalent to the locus drawn by the wheel rim when the wheel rolls. If the wheel center is used as a reference, the track of the wheel rim relative to the wheel center is still a circle. Preferably, the yaw handling performance parameters include: the circling radius, the circling period and the circling angular speed of the airship; the calculation process of the yaw handling performance parameters comprises the following steps:

establishing a second circular equation according to the hovering trajectory of the airship

[(x-W_xt)-x₀₀]²+[(y-W_yt)-y₀₀]²＝R²(8)

Wherein (W)_x,W_y) Is the wind speed, (x)₀₀,y₀₀) The position of the center of a circle at the initial moment, (x, y) is the position of the airship measured by the shipborne navigation system, and R is the circling radius of the airship to be estimated;

selecting a series of points (x) from the hover trajectory of the airship_i,y_i,t_i) And i is 1,2 and …, and calculating the hover radius R of the airship to be estimated through a circle fitting algorithm.

In particular, in estimating the wind speed (W)_x,W_y) Then, assume the position of the center of the circle at the initial time as (x)₀₀,y₀₀) Then, at time t, the position of the center of the circle (x)₀,y₀) Is composed of

$\left\{\begin{array}{c}{x}_0=x_{00}+W_{x}t\\ y_0=y_{00}+W_{y}t\end{array}\right.---\left(9\right)$

The position of the airship relative to the center of a circle also satisfies the general circular curve equation

(x-x₀)²+(y-y₀)²＝R²(10)

Wherein x and y are the locus coordinates of the x direction and the y direction on the plane, and x₀、y₀The x coordinate and the y coordinate of the center of the circle, and R is the radius of the circle.

Substituting the formula (9) into the above formula to obtain a second equation of a circle

[(x-W_xt)-x₀₀]²+[(y-W_yt)-y₀₀]²＝R²(11)

Order to

$\left\{\begin{array}{c}X=x-W_{x}t\\ Y=y-W_{y}t\end{array}\right.---\left(12\right)$

The following identification equation is obtained

[X-x₀₀]²+[Y-y₀₀]²＝R²(13)

Taking a certain point on the cycloidal track of the airship as an initial point, and selecting a series of points (x) from the track_i,y_i,t_i) I is 1,2, …, (X) is calculated_i,Y_i) I 1,2, …, an estimate of the radius R of the disc can be obtained using the circle fitting algorithm described above.

The spiral period and the spiral angular velocity can be calculated by the following formulas:

$\mathrm{\ω}=\frac{V_a}{R}---\left(14\right)$

$T_{circle}=\frac{2\mathrm{\π}}{\mathrm{\ω}}---\left(15\right)$

where ω is the spiral angular rate, T_circleIs the period of the spiral.

Preferably, the longitudinal and lateral stability performance parameters comprise an average sideslip angle, an instantaneous sideslip angle, an average angle of attack and an instantaneous angle of attack of the airship;

the average and instantaneous sideslip angles of the airship are calculated by the following formulas:

$\stackrel{\‾}{\mathrm{\β}}={\sin }^{-1}\left(\frac{{\stackrel{\‾}{V}}_{a,yb}}{V_a}\right)---\left(16\right)$

${\mathrm{\β}}_i={\sin }^{-1}\[\frac{{\left(V_{a,yb}\right)}_i}{V_a}\]---\left(17\right)$

$\left[\begin{array}{c}{\stackrel{\‾}{V}}_{a,xb}\\ {\stackrel{\‾}{V}}_{a,yb}\\ {\stackrel{\‾}{V}}_{a,zb}\end{array}\right]=\frac{1}{m}{\left[\begin{array}{c}\underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,xb}\right)}_i\\ \underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,yb}\right)}_i\\ \underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,zb}\right)}_i\end{array}\right]}_i---\left(18\right)$

${\left[\begin{array}{c}{V}_{a,xb}\\ V_{a,yb}\\ V_{a,zb}\end{array}\right]}_i=A({\mathrm{\φ}}_i,{\mathrm{\θ}}_i,{\mathrm{\ψ}}_i){\left[\begin{array}{c}{V}_{a,x}\\ V_{a,y}\\ V_{a,z}\end{array}\right]}_i---\left(19\right)$

${\left[\begin{array}{c}{V}_{a,x}\\ V_{a,y}\\ V_{a,z}\end{array}\right]}_i={\left[\begin{array}{c}{V}_x\\ V_y\\ V_z\end{array}\right]}_i-\left[\begin{array}{c}{W}_x\\ W_y\\ 0\end{array}\right]---\left(20\right)$

wherein, ${\left[\begin{array}{ccc}{V}_{a,x}& V_{a,y}& V_{a,z}\end{array}\right]}_i^T$ is the component of airspeed in the navigation coordinate system; ${\left[\begin{array}{ccc}{V}_x& V_y& V_z\end{array}\right]}_i^T$ for the component of the ground speed in the navigation coordinate system, [ W ]_xW_y0]^TBeing the component of the wind speed in the navigational coordinate system, ${\left[\begin{array}{ccc}{V}_{a,xb}& V_{a,yb}& V_{a,zb}\end{array}\right]}_i^T$ the component of the airspeed on the body axis, A (φ)_i,θ_i,ψ_i) For the transformation matrix from the navigation coordinate system to the body axis system, m is the number of points on the spiral trajectory, i is 1,2, …, m,to average slip angle, β_iIs t_iThe angle of the side slip at the moment, ${\left[\begin{array}{ccc}{\stackrel{\‾}{V}}_{a,xb}& {\stackrel{\‾}{V}}_{a,yb}& {\stackrel{\‾}{V}}_{a,zb}\end{array}\right]}^T$ is the average value of the components of the airspeed on the body axis,is the average of the y-axis direction components of the airspeed on the body axis, (V)_a,yb)_iIs t_iThe time-of-day airspeed is the y-axis direction component on the body axis.

In particular, considering that the wind speed in the vertical direction is small, and therefore assumed to be zero, the airspeed component (V) on the navigational system is derived from the ground speed and the wind speed_a,x,V_a,y,V_a,z)

$\left[\begin{array}{c}{V}_{a,x}\\ V_{a,y}\\ V_{a,z}\end{array}\right]=\left[\begin{array}{c}{V}_x\\ V_y\\ V_z\end{array}\right]-\left[\begin{array}{c}{W}_x\\ W_y\\ 0\end{array}\right]---\left(21\right)$

Assuming the attitude angles from the navigation system to the body axis are (psi, theta, phi), the airspeed is converted from the navigation system to the body axis $\left[\begin{array}{c}{V}_{a,xb}\\ V_{a,yb}\\ V_{a,zb}\end{array}\right]=A_n^b\left[\begin{array}{c}{V}_{a,x}\\ V_{a,y}\\ V_{a,z}\end{array}\right]---\left(22\right)$

Transformation matrixCalculated from the attitude angles (psi, theta, phi) by the following formula

For each point on the spiral trajectory, (V) is calculated according to equation (21)_a,yb)_i，i＝1,2,…,m。

When the roll angle phi is small, (V)_a,yb)_iCan be simplified into

(V_a,yb)_i≈[-V_xsinψ+V_ycosψ+V_asinθsinφ]_i(24)

Wherein, V_x,V_yThe components of the ground speed in the x and y directions, V, respectively_aIs the average airspeed;

get

${\stackrel{\‾}{V}}_{a,yb}=\frac{1}{m}\underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,yb}\right)}_i---\left(25\right)$

Then there is an average slip angle of

$\stackrel{\‾}{\mathrm{\β}}={\sin }^{-1}\left(\frac{{\stackrel{\‾}{V}}_{a,yb}}{V_a}\right)---\left(26\right)$

Equation (26) is the average sideslip angle at steady state hover, correspondingly at each t_iAt that moment, the instantaneous sideslip angle β may be calculated_i

${\mathrm{\β}}_i={\sin }^{-1}\[\frac{{\left(V_{a,yb}\right)}_i}{V_a}\]---\left(27\right)$

As shown in FIG. 6, a plot of the instantaneous and average sideslip angles of an airship, the instantaneous sideslip angle β of the airship_iRelative to the average slip angleThe smaller the fluctuation amount, the better the airship lateral stability.

Preferably, the average angle of attack and the instantaneous angle of attack of the airship are calculated by the following formulas:

$\stackrel{\‾}{\mathrm{\α}}={\tan }^{-1}\left(\frac{{\stackrel{\‾}{V}}_{a,zb}}{{\stackrel{\‾}{V}}_{a,xb}}\right)$ or $\stackrel{\‾}{\mathrm{\α}}\≈\frac{1}{m}\underset{i=1}{\overset{m}{\Σ}}{\mathrm{\θ}}_i---\left(28\right)$

${\mathrm{\α}}_i={\tan }^{-1}\frac{{\left(V_{a,bz}\right)}_i}{{\left(V_{a,bx}\right)}_i}$ Or α_i≈θ_i(29)

WhereinIn order to obtain an average angle of attack,is the average of the m pitch angles,is the average value of the space velocity on the z-axis direction component of the body axis,as the average of the x-axis component of the airspeed on the body axis, α_iIs t_iInstantaneous angle of attack at time, theta_iIs t_iPitch angle at time (V)_a,bz)_iIs t_iAverage value of z-axis direction component of space velocity on body axis at moment (V)_a,bx)_iIs t_iThe time-of-day airspeed is the average of the x-axis direction components on the body axis.

In particular, the mean angle of attackThere are two methods for the estimation of (c). First, the average flying pitch angle θ is obtained, and the average attack angle is

$\stackrel{\‾}{\mathrm{\α}}\≈\frac{1}{m}\underset{i=1}{\overset{m}{\Σ}}{\mathrm{\θ}}_i---\left(30\right)$

Secondly, the airspeed component (V) of the body axis system given by the formula (19)_a,xb,V_a,yb,V_a,zb)_iComputing

${\stackrel{\‾}{V}}_{a,xb}=\frac{1}{m}\underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,xb}\right)}_i,{\stackrel{\‾}{V}}_{a,zb}=\frac{1}{m}\underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,zb}\right)}_i---\left(31\right)$

Then have an average angle of attack of

$\stackrel{\‾}{\mathrm{\α}}={\tan }^{-1}\left(\frac{{\stackrel{\‾}{V}}_{a,zb}}{{\stackrel{\‾}{V}}_{a,xb}}\right)---\left(32\right)$

Accordingly, at each t_iAt the moment, the instantaneous angle of attack α can be calculated_i

${\mathrm{\α}}_i={\tan }^{-1}\frac{{\left(V_{a,bz}\right)}_i}{{\left(V_{a,bx}\right)}_i},$ Or α_i≈θ_i(33)

FIG. 7 is a graph of instantaneous and average angles of attack for an airship, instantaneous angle of attack α_iRelative to the average angle of attackThe fluctuation amount of the airship reflects the longitudinal stability of the airship. The smaller the amount of fluctuation, the better the longitudinal stability of the airship.

On the other hand, by adopting the method for estimating the flight performance parameters of the airship on the stratosphere, the invention also provides a system for estimating the flight performance parameters of the airship on the stratosphere, which comprises the following steps: the device comprises a flight unit, an acquisition unit and an estimation unit;

the flying unit is used for enabling the airship to enter a stable hovering flying state;

the acquisition unit acquires the ground speed, attitude information and position information of the airship;

the estimation unit is used for estimating the flight performance parameters of the airship according to the ground speed, the attitude information and the position information of the airship.

The method and the system for estimating the flight performance parameters of the airship on the stratosphere can calculate the accurate flight performance parameters such as horizontal wind speed, wind direction, airspeed, yaw control performance (steady state hovering radius, hovering period, spiraling angle rate), longitudinal and transverse stability (sideslip angle and attack angle) and the like by utilizing the ground speed, position and attitude angle information given by a navigation system in the airship under the high-altitude thin atmospheric environment; the process of the invention is simple and easy to realize, and the airship can enter the hovering flight state only by fixing the rotating speed and the yaw control quantity of the main propeller, and the hovering flight enables the airship to be at a fixed height, the wind speed and the wind direction to be fixed, so that the airship is in a constant wind field, and the error of estimating the flight performance parameters of the airship on the stratosphere is reduced.

Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims (10)

1. A method for estimating flight performance parameters of an airship on a stratosphere is characterized in that,

bringing the airship into a stable hover flight state;

acquiring ground speed, attitude information and position information of the airship;

and estimating the flight performance parameters of the airship according to the ground speed, the attitude information and the position information of the airship.

2. The method of claim 1, wherein said entering said airship into stable hover flight comprises:

fixing the rotation speed and the yaw control quantity of a main propeller of the airship to enable the airship to enter a hovering flight state; and when the fluctuation value of the flying height of the airship is smaller than a preset value, the airship is considered to enter a stable hovering flying state.

3. The method of estimating stratospheric airship flight performance parameters according to any one of claims 1 to 2,

the flight performance parameters of the airship comprise wind speed, airspeed, yaw manipulation performance parameters and longitudinal and transverse stability performance parameters.

4. The method of claim 3, wherein the calculation of the wind speed and the airspeed comprises:

establishing a first circular equation according to the relation among the wind speed, the airspeed and the ground speed:

${(V_x-W_x)}^2+{(V_y-W_y)}^2=V_a^2$

wherein (V)_x,V_y) The ground speed (W) measured by the ship-borne navigation system_x,W_y) For the wind speed to be estimated, V_aTo be estimatedAirspeed;

using a plurality of ground speeds (V) measured during hover flight_xi,V_yi) I 1,2, … n, the wind speed to be estimated (W) is calculated by a circle fitting algorithm_x,W_y) And airspeed V to be estimated_a。

5. Method for estimating the flight performance parameters of an airship in the stratosphere according to claim 4, characterized in that the wind speed (Wt) to be estimated is calculated by a circle fitting algorithm_x,W_y) And airspeed V to be estimated_aComprises the following steps:

A. passing through a plurality of ground speeds (V)_xi,V_yi) I 1,2, … n, defining intermediate parameters

a＝2W_x，b＝2W_y，c＝V_a ²-(W_x ²+W_y ²)

Constructing a least square equation;

$\left[\begin{array}{ccc}{V}_{x1}& V_{y1}& 1\\ V_{x2}& V_{y2}& 1\\ .& .& .\\ .& .& .\\ .& .& .\\ V_{xn}& V_{yn}& 1\end{array}\right]\left[\begin{array}{c}a\\ b\\ c\end{array}\right]=\left[\begin{array}{c}{V_{x1}}^2+{V_{y1}}^2\\ {V_{x2}}^2+{V_{y2}}^2\\ .\\ .\\ .\\ {V_{xn}}^2+{V_{yn}}^2\end{array}\right]$

B. solving a least square equation to calculate a, b and c;

C. calculating the wind speed (W) from a, b, c_x,W_y) Airspeed V_a。

$W_x=\frac{a}{2},W_y=\frac{b}{2},V_a=\sqrt{c+{W_x}^2+{W_y}^2}$

6. The method of claim 3, wherein the yaw handling performance parameters comprise: the circling radius, the circling period and the circling angular speed of the airship; the calculation process of the yaw handling performance parameters comprises the following steps:

establishing a second circular equation according to the hovering trajectory of the airship

[(x-W_xt)-x₀₀]²+[(y-W_yt)-y₀₀]²＝R²

Wherein (W)_x,W_y) Is the wind speed, (x)₀₀,y₀₀) The position of the center of a circle at the initial moment is (x, y) the position of the airship measured by the airborne navigation system, R the circling radius of the airship to be estimated, and t time;

selecting a series of points (x) from the hover trajectory of the airship_i,y_i,t_i) And i is 1,2 and …, and calculating the hover radius R of the airship to be estimated through a circle fitting algorithm.

7. The method of claim 6, wherein the hover period and the hover angular velocity are calculated by the following formula:

$\mathrm{\ω}=\frac{V_a}{R}$

$T_{circle}=\frac{2\mathrm{\π}}{\mathrm{\ω}}$

where ω is the spiral angular rate, T_circleIs the period of the spiral.

8. The method of claim 3, wherein the longitudinal and lateral stability parameters comprise an average sideslip angle, an instantaneous sideslip angle, an average angle of attack, and an instantaneous angle of attack of the airship;

the average and instantaneous sideslip angles of the airship are calculated by the following formulas:

$\stackrel{\‾}{\mathrm{\β}}={\sin }^{-1}\left(\frac{{\stackrel{\‾}{V_a}}_{,yb}}{V_a}\right)$

${\mathrm{\β}}_i={\sin }^{-1}\[\frac{{\left(V_{a,yb}\right)}_i}{V_a}\]$

$\left[\begin{array}{c}{\stackrel{\‾}{V}}_{a,xb}\\ {\stackrel{\‾}{V}}_{a,yb}\\ {\stackrel{\‾}{V}}_{a,zb}\end{array}\right]=\frac{1}{m}{\left[\begin{array}{c}\underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,xb}\right)}_i\\ \underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,yb}\right)}_i\\ \underset{i=1}{\overset{m}{\Σ}}{\left(V_{a,zb}\right)}_i\end{array}\right]}_i$

${\left[\begin{array}{c}{V}_{a,xb}\\ V_{a,yb}\\ V_{a,zb}\end{array}\right]}_i=A({\mathrm{\φ}}_i,{\mathrm{\θ}}_i,{\mathrm{\ψ}}_i){\left[\begin{array}{c}{V}_{a,x}\\ V_{a,y}\\ V_{a,z}\end{array}\right]}_i$

${\left[\begin{array}{c}{V}_{a,x}\\ V_{a,y}\\ V_{a,z}\end{array}\right]}_i=\left[\begin{array}{c}{V}_x\\ V_y\\ V_z\end{array}\right]-\left[\begin{array}{c}{W}_x\\ W_y\\ 0\end{array}\right]$

wherein, ${\left[\begin{array}{ccc}{V}_{a,x}& V_{a,y}& V_{a,z}\end{array}\right]}_i^T$ as a component of airspeed in the navigational coordinate system； ${\left[\begin{array}{ccc}{V}_x& V_y& V_z\end{array}\right]}_i^T$ For the component of the ground speed in the navigation coordinate system, [ W ]_xW_y0]^TBeing the component of the wind speed in the navigational coordinate system, ${\left[\begin{array}{ccc}{V}_{a,xb}& V_{a,yb}& V_{a,zb}\end{array}\right]}_i^T$ the component of the airspeed on the body axis, A (φ)_i,θ_i,ψ_i) For the transformation matrix from the navigation coordinate system to the body axis system, m is the number of points on the spiral trajectory, i is 1,2, …, m,is the average slip angle，β_iIs t_iThe angle of the side slip at the moment, ${\left[\begin{array}{ccc}{\stackrel{\‾}{V}}_{a,xb}& {\stackrel{\‾}{V}}_{a,yb}& {\stackrel{\‾}{V}}_{a,zb}\end{array}\right]}^T$ is the average value of the components of the airspeed on the body axis,is the average of the y-axis direction components of the airspeed on the body axis, (V)_a,yb)_iIs t_iThe time-of-day airspeed is the y-axis direction component on the body axis.

9. The method of claim 8, wherein the average and instantaneous angles of attack of the airship are calculated by:

$\stackrel{\‾}{\mathrm{\α}}={\tan }^{-1}\left(\frac{{\stackrel{\‾}{V}}_{a,zb}}{{\stackrel{\‾}{V}}_{a,xb}}\right)$ or $\stackrel{\‾}{\mathrm{\α}}\≈\frac{1}{m}\underset{i=1}{\overset{m}{\Σ}}{\mathrm{\θ}}_i$

${\mathrm{\α}}_i={\tan }^{-1}\frac{{\left(V_{a,bz}\right)}_i}{{\left(V_{a,bx}\right)}_i}$ Or α_i≈θ_i

Wherein,in order to obtain an average angle of attack,is the average of the m pitch angles,is the average value of the space velocity on the z-axis direction component of the body axis,as the average of the x-axis component of the airspeed on the body axis, α_iIs t_iInstantaneous angle of attack at time, theta_iIs t_iPitch angle at time (V)_a,bz)_iIs t_iAverage value of z-axis direction component of space velocity on body axis at moment (V)_a,bx)_iIs t_iThe time-of-day airspeed is the average of the x-axis direction components on the body axis.

10. A system for estimating stratospheric airship flight performance parameters, comprising: the device comprises a flight unit, an acquisition unit and an estimation unit;

the flying unit is used for enabling the airship to enter a stable hovering flying state;

the acquisition unit acquires the ground speed, attitude information and position information of the airship;

the estimation unit is used for estimating the flight performance parameters of the airship according to the ground speed, the attitude information and the position information of the airship.