RU2087390C1 - Method of determination of velocity head of incoming flow on boards space vehicle equipped with system of powered gyroscopes - Google Patents

Abstract

FIELD: space engineering. SUBSTANCE: in plotting the orientation of space vehicle relative to flow and maintaining it in section of determination of velocity head, moment of flow pressure force (in form of integral estimation) acting on space vehicle is measured. Powered gyroscopes are used as meters which give vector H (t) of accumulated moment of momentum of space vehicle. During first passage of measuring section, configuration and orientation of space vehicle are maintained at minimum external disturbing moment and during subsequent passages of this section, maximum aerodynamic moment is created, other components of disturbing moment being kept constant. EFFECT: enhanced accuracy of determination of velocity head with no special instruments. 1 dwg

Description

 The invention relates to the field of space technology and can be used to determine the speed pressure of a free stream on spacecraft controlled by power gyroscopes.

(C_i соответствующие аэродинамические коэффициенты, S_m площадь миделя объекта), во-вторых, по значению скоростного напора (при известной скорости объекта V) можно судить о плотности атмосферы ρ В свою очередь, зная плотность и используя зависимость плотности от высоты, можно определить высоту полета H=f(ρ) Таким образом, измерение скоростного напора позволит получить информацию о силах, действующих на объект, и о высоте полета. Что касается получаемых данных о распределении плотности, то они представляют значительный самостоятельный интерес в связи с изучением параметров верхней атмосферы, прогнозированием времени существования КА и определением необходимых запасов топлива.The measurement of the pressure head in flight directly on board the spacecraft (SC) is one of the tasks, the solution of which is necessary for the implementation of autonomous control of the object. The value of the velocity head (C _H = ρv ^2/2) defines, firstly, F _i aerodynamic forces and moments acting on the spacecraft:

(C _{i are the} corresponding aerodynamic coefficients, S _{m is} the midship area of the object), and secondly, by the value of the velocity head (at the known object velocity V), one can judge the density of the atmosphere ρ In turn, knowing the density and using the dependence of density on height, flight altitude H = f (ρ) Thus, measuring the pressure head will provide information on the forces acting on the object and on the flight altitude. As for the obtained data on the density distribution, they are of considerable independent interest in connection with the study of the parameters of the upper atmosphere, the prediction of the spacecraft lifetime, and the determination of the necessary fuel reserves.

A known method for determining the pressure head according to the braking of the spacecraft (see Space Research, vol. X, issue 3. M. Nauka, 1972, p. 452 453). In it, knowing the dependence ΔH = f (C _H , t), the change in flight altitude ΔH over time t is determined by means of the radio control of the orbit, then C _{n is} calculated.

Using this method leads to rough estimates of the value of C _n . This is due to the large order of smallness of ΔH during the flight time of the section on which C _n measurements are made.

There is a method of determining the speed pressure of a flow on board a spacecraft using a membrane sensor closest in technical essence to the proposed invention and accepted by the authors as a prototype (see TsAGI, issue 2103, M. 1980, pp. 3-14). This technique consists in using the property of the membrane to bend under the action of force from the side of the incoming flow. Thus, the dynamic pressure ρv ^2/2 perceived membrane sensor.

где C_X(α, θ) коэффициент сопротивления, зависящий от коэффициента аккомодации α нормального импульса и угла атаки q пластины, А площадь пластины) (см. Труды ЦАГИ, вып. 2103. М. 1980, с. 4).For this, a set of equipment with a sensitive element is installed onboard the spacecraft; orient the spacecraft with respect to the incident flow so that the angle between the plane of the sensor plate and the direction of flow is 90 ^o C; maintain this orientation of the spacecraft in the portion of the orbit where C _n is measured, and measure the external perturbing aerodynamic effect on the spacecraft by registering the deflection of the membrane Δ proportional to the force F acting on it in a free molecular flow; then determined by the measured values of D, the velocity head of the incoming flow (C _n ), which is proportional to D

where C _X (α, θ) is the resistance coefficient depending on the accommodation coefficient α of the normal impulse and the angle of attack q of the plate, A is the area of the plate) (see Transactions of TsAGI, issue 2103. M. 1980, p. 4).

 The main disadvantage of this method is the large error (10 - 20%), which is a consequence of working with values of large order of smallness, determined by the small area of membrane A.

In addition, the above method allows you to measure C _n with a large heterogeneity of the medium only in a narrow "tube" of the incoming flow (in cross section with area A), when in practice a "tube" in cross section with area S _{m is} needed.

The technical result is to increase the accuracy of determination of C _n .

перед достижением указанного участка орбиты определяют ориентацию КА, при которой значение вектора аэродинамического момента максимально, а остальные составляющие главного вектора возмущающего момента неизменны, строят данную ориентацию КА, с момента достижения указанного участка и до его конца измеряют текущее значение вектора кинетического момента в системе

определяют изменение вектор функции накопленного кинетического момента

по выражению

соответственно

приведенные к нулевым условиям начала участка), определяют значение скоростного напора набегающего потока ([C_н(t)] по выражению:

где К_a обобщенный аэродинамический коэффициент КА).The specified technical result is achieved by the fact that in the method, which includes the orientation of the spacecraft relative to the incoming flow, maintaining the orientation of the spacecraft in the portion of the orbit where the speed of the head of the free stream is measured, the measurement of the external aerodynamic effects acting on the spacecraft, the determination of the speed of the head of the head the measured values of the velocity head of the incident flow, before reaching the measured portion of the orbit, the orientation of the spacecraft is determined, at which the value of the main the vector of the perturbing moment is minimal, they build the given orientation of the spacecraft, from the moment of reaching the section to its end measure the current values of the vector of kinetic moment in the system

before reaching the indicated portion of the orbit, the orientation of the spacecraft is determined, at which the value of the aerodynamic moment vector is maximum, and the remaining components of the main vector of the disturbing moment are unchanged, this orientation of the spacecraft is built, from the moment of reaching the indicated section to the end, the current value of the kinetic moment vector in the system is measured

determine the change in the function vector of the accumulated kinetic moment

by expression

respectively

reduced to zero conditions at the beginning of the section), determine the value of the velocity head of the incoming flow ([C _n (t)] by the expression:

where K _{a is the} generalized aerodynamic coefficient of the spacecraft).

 As indicated, the invention is aimed at improving accuracy in determining the speed head. To justify the achievement of this goal by the proposed method, we compare the factors that determine the error in the prototype and the invention.

и погрешности в определении обобщенного аэродинамического параметра КА. Погрешность в измерении

согласно техническим характеристикам системы СГ модуля "Гамма" (см. Система управления движением модуля "Гамма". Контроль режимов, П25092-118 НПО "Энергия", г. Калининград, 1987) не более 2,5% Погрешность в определении коэффициента K_a (см. Пакет прикладных программ "Высота"; ОФАП, САПР, 1983, НПО "Энергия", г. Калининград) не хуже 1,5% Таким образом, если пренебречь погрешность дифференцирования, то суммарная погрешность предложенного авторами способа определения скоростного напора не превышает 4% У прототипа указанная погрешность 10%
Сущность изобретения поясняется графически: на чертеже представлен космический аппарат (КА), управляемый по углам ψ, ν и γ и снабженный средством регулирования аэродинамического момента, например, панелями 1 солнечных батарей.From the expression for the pressure head, given together with the claims, it follows that the error of determination consists of the error of measurement of values

and errors in determining the generalized aerodynamic parameter of the spacecraft. Measurement error

according to the technical characteristics of the Gamma module SG system (see Gamma module motion control system. Control of modes, P25092-118 NPO Energia, Kaliningrad, 1987) no more than 2.5% Error in determining the coefficient K _a ( see the Application package "Height"; OFAP, CAD, 1983, NPO Energia, Kaliningrad) not worse than 1.5% Thus, if we neglect the error of differentiation, the total error of the method proposed by the authors for determining the pressure head does not exceed 4 % The prototype specified error of 10%
The invention is illustrated graphically: the drawing shows a spacecraft (SC), controlled by the angles ψ, ν and γ and equipped with means for controlling the aerodynamic moment, for example, solar panels 1.

 Panels 1 can deviate through an angle v relative to the spacecraft body.

под действием внешнего возмущающего момента

(см. Б.В.Раушенбах, Е.Н.Токарь. Управление ориентацией КА. М. Наука, 1974, с. 125 -126).By turning the spacecraft hull to various orientations in orbit, as well as by turning solar panels (or other similar elements), various disturbing moments can be created on the spacecraft hull. Modern spacecraft are widely used in orientation systems of inertial actuators, for example, power gyroscopes with the ability to accumulate kinetic momentum

under the influence of an external disturbing moment

(see B.V. Rauschenbakh, E.N. Tokar. Control of the orientation of the spacecraft. M. Nauka, 1974, p. 125-126).

The spacecraft works, in determining C _n , as follows.

и гравитационный

моменты, остальные же составляющие

незначительны по отношению к ним и не учитываются в расчетах движения КА (см. Механика космического полета. М: Машиностроение, 1989, с. 107). Необходимо определить ориентацию КА, при которой

Гравитационный момент по осям орбитальной системы координат равен (см. А.П.Разыграев. Основы управления полетом космических аппаратов. М. Машиностроение, 1990, с. 26):

где J_x, J_y, J_z моменты инерции КА; ν, γ углы тангажа и крена; w орбитальная частота. Таким образом

при условии γ=ν _→ 0. Аэродинамический момент:

где C_i коэффициент аэродинамической силы, l_x характеристическое расстояние, S_м площадь миделя,

при условии C_i _→ 0 соответственно C_i _→ 0 при условии γ=ν=ψ=Φ _→ 0 где ψ угол рыскания, v угол атаки больших элементов конструкции (например солнечных батарей; см. фиг. 1, поз. 1). Следовательно, в орбитальной системе координат условие

выполняется при γ=ν=ψ=Φ _→ 0 (В случае солнечных батарей (СБ): Φ _→ 0 означает, что СБ ориентированы "флюгером" по отношению к набегающему потоку).Before reaching the portion of the orbit, on which it is necessary to establish the value of C _n , determine the orientation of the spacecraft at which the value of the main vector of the disturbing moment is minimal. Let, for example, the spacecraft revolve in orbits with an altitude of 150.450 km, on which the tasks of determining C _n are most often posed. At these altitudes, the value of the main vector of the disturbing moment is determined by the aerodynamic

and gravitational

moments, the remaining components

insignificant in relation to them and are not taken into account in the calculations of the spacecraft motion (see. Space Flight Mechanics. M: Mashinostroenie, 1989, p. 107). It is necessary to determine the orientation of the spacecraft at which

The gravitational moment along the axes of the orbital coordinate system is equal (see A.P. Razigraev. Fundamentals of spacecraft flight control. M. Mashinostroenie, 1990, p. 26):

where J _x , J _y , J _{z are the} moments of inertia of the spacecraft; ν, γ pitch and roll angles; w orbital frequency. Thus

provided γ = ν _ → 0. Aerodynamic moment:

where C _{i is} the aerodynamic force coefficient, l _{x is the} characteristic distance, S _{m is} the midship area,

under the condition C _i _ → 0, respectively, C _i _ → 0 under the condition γ = ν = ψ = Φ _ → 0 where ψ is the yaw angle, v is the angle of attack of large structural elements (for example, solar panels; see Fig. 1, item 1 ) Therefore, in the orbital coordinate system, the condition

is performed at γ = ν = ψ = Φ _ → 0 (In the case of solar panels (SB): Φ _ → 0 means that the SBs are oriented with a “weather vane” with respect to the incident flow).

 Next, the spacecraft builds the orientation: the angles γ, ν, ψ are reduced to zero by the executive bodies of the spacecraft, the angle v is the orientation system of the solar panels.

На данном участке, ограниченном временным интервалом (0, τ ):

где

значение

в начале участка. Накопленный кинетический момент в системе СГ на донном участке (приведенный к нулевым условиям начала участка):

поскольку

то

Измерения

необходимы для "установки нуля" измерительного прибора, которым является система СГ (учет погрешности от принятых допущений: КА магнитоуравновешен и т.д.).From the moment of reaching the site on which C _n is determined, and until its end, the current values of the kinetic moment vector in the system are measured

In this section, limited by the time interval (0, τ):

Where

value

at the beginning of the site. Accumulated kinetic moment in the SG system at the bottom site (reduced to zero conditions at the beginning of the site):

because the

then

Measurements

are necessary for the "zeroing" of the measuring device, which is the SG system (accounting for errors from the accepted assumptions: the spacecraft is magnetically balanced, etc.).

неизменны по отношению к предшествующей ориентации КА, т.е. стремятся к нулю: очевидно, если

то γ=ν=ψ=0, Φ ≠ 0. В случае солнечных батарей максимальный аэродинамический момент при ориентации СБ "пропеллер" (в этом случае M_A=C_iρv²l_XS_Мsin2Φ) и Φ=45^°
С момента достижения КА участка, на котором определяется C_н, и до его конца измеряют текущие значения вектора кинетического момента в системе СГ

где

значение

в начале участка. В этом случае

Далее определяют изменение вектора функции накопленного кинетического момента:

В заключение определяется C_н согласно выражению:

где

-аэродинамические коэффициенты КА при первом и втором вариантах измерения

В качестве примера реализации предлагаемого способа рассмотрим КА астрофизический модуль "Гамма", на борту которого установлены система СГ и СБ с системой их ориентации (см. В.С.Ковтун, В.В.Митрикас, В.Н.Платонов, С.Г.Ревнивых, Н.А.Суханов. Математическое обеспечение проведения экспериментов при управлении ориентацией космического астрофизического модуля "Гамма". Изв. АН СССР. Технич. кибернетика. 1990, N 3, с. 144 157).Then, until this section is reached, the next orientation of the spacecraft is built at the next turn, at which the value of the aerodynamic moment vector is maximum, and the remaining components

unchanged with respect to the previous orientation of the spacecraft, i.e. tend to zero: obviously, if

then γ = ν = ψ = 0, Φ ≠ 0. In the case of solar panels, the maximum aerodynamic moment when the SB is “propeller” oriented (in this case, M _A = C _i ρv ² l _X S _M sin2Φ) and Φ = 45 ^°
From the moment the spacecraft reaches the site on which C _n is determined, and until its end, the current values of the kinetic moment vector in the SG system are measured

Where

value

at the beginning of the site. In this case

Next, determine the change in the function vector of the accumulated kinetic moment:

In conclusion, C _n is determined according to the expression:

Where

aerodynamic coefficients of the spacecraft in the first and second measurement options

As an example of the implementation of the proposed method, we consider the Gamma astrophysical module, on board of which an SG and SB system with their orientation system are installed (see V.S. Kovtun, V.V. Mitrikas, V.N. Platonov, S.G. .Revnivykh, N.A. Sukhanov. Software for conducting experiments in controlling the orientation of the Gamma astrophysical space module. Izv. AN SSSR. Technical Cybernetics. 1990, N 3, p. 144 157).

) (подробную реализацию см. например, "Навигация, наведение и стабилизация в космосе." Под ред. Дж.Э.Миллера. М. Машиностроение, 1970, с. 208 215), вычисляет накопленный кинетический момент по формуле

. Далее перед достижением участка на следующем витке строят вышеизложенными средствами ориентацию с углами γ=ν=ψ=0 а СБ разворачивают "пропеллером", т.е. Φ₁=45^°, Φ₂=135^°,
где Φ₁ и Φ₂ соответственно углы разворота первой и второй солнечных батарей.Suppose, it is required to determine the velocity head of the incident flow in the spacecraft’s orbit 300 km high, limited by the interval [0; τ
For this, before reaching the indicated area, using the executive bodies of the Gamma spacecraft orientation and control system, they build an orientation in the orbital coordinate system with angles g = ν = ψ = 0 using the SB orientation system and construct the solar cell orientation with a “weather vane”, i.e. . Φ = 0
From the moment the site (t = 0) is reached and until its end (t = τ), the Gamma on-board computer complex (BVK) captures the current measured values of the kinetic moment vector in the system

) (for a detailed implementation see, for example, “Navigation, Guidance, and Stabilization in Space.” Edited by J.E. Miller. M. Mechanical Engineering, 1970, p. 208 215), calculates the accumulated kinetic moment by the formula

. Next, before reaching the site in the next round, the orientation with the angles γ = ν = ψ = 0 is built with the above means and the SB is deployed with a “propeller”, i.e. Φ ₁ = 45 ^° , Φ ₂ = 135 ^° ,
where Φ ₁ and Φ _2, respectively, the rotation angles of the first and second solar cells.

Следующим этапом БВК вычисляет изменение вектор-функции накопленного кинетического момента по формуле

В заключение БВК вычисляет искомый C_н по выражению:

где

для КА "Гамма" S_м 5,8 м², l_x 7,7 м,

.From the moment the site is reached and until its end, according to the above scheme, calculate

The next stage of the BVK calculates the change in the vector function of the accumulated kinetic moment by the formula

In conclusion, IOO calculates the desired C _n by the expression:

Where

for Gamma spacecraft S _m 5.8 m ² , l _x 7.7 m,

.

Moreover, for the differential value of 2.34 • 10 ^-3 on a fixed interval dt, C _n 9.36 • 10 ^-5 .

Claims (1)

 A method for determining the flow velocity on board a spacecraft with a system of power gyroscopes, including the orientation of the spacecraft relative to the flow, maintaining orientation on the measured portion of the orbit, measuring external perturbing aerodynamic effects acting on the spacecraft, determining from the measured values of the flow velocity characterized in that before reaching the measured portion of the orbit determine the orientation and configuration of the space app arata, at which the values of the main vector of the disturbing moment, as well as the aerodynamic disturbance moment are minimal, build this orientation of the spacecraft, from the moment the measured section is reached and until its end, the current value of the vector function of the kinetic moment in the system of power gyroscopes is measured, before each subsequent measured the orbit section determines the orientation and configuration of the spacecraft, at which the value of the aerodynamic moment vector is maximum, and the remaining components of of the apparent vector of the disturbing moment are unchanged, they build this orientation with the modified configuration of the spacecraft, re-measure the current value of the vector function of the kinetic moment in the system of power gyroscopes in the same section, determine the change in the vector function of the accumulated kinetic moment as a result of the subsequent passage of the measured portion of the orbit with respect to to this vector function, measured as a result of the previous passage of the measured portion of the orbit, and use this change of the vector function to determine dividing the desired speed head.