RU2020417C1 - Inertial navigation system - Google Patents

Abstract

FIELD: navigation instrumentation engineering. SUBSTANCE: inertial navigation system consists of azimuth-free gyrostabilized platform and computing unit in which components of absolute motion speed and coordinates are computed by accelerometer signals. Novelty consists in that accelerometer signals are fed to motors for platform stabilization with correction. Correction is formed by components of absolute linear speed from cross channels with regard to object latitude. Such damping system makes it possible to reduce disturbance of navigation system and to increase its accuracy. Effect is particularly appreciable in operation of system for more than 1 h. EFFECT: higher accuracy in determination of angles of orientation, speed and coordinated in steady horizontal motion of object at constant speed and heading. 2 dwg

Description

 The invention relates to navigation instrumentation and can be used to develop accurate autonomous inertial navigation systems.

 A class of inertial navigation systems (ANS) of a semi-analytical type with a free azimuth-free platform is known, the drawback of which is the presence of undamped vibrational components of errors in determining the orientation angles of velocities and coordinates of an object caused by instrumental errors of their elements (errors in the initial gyro platform display, gyroscope drift, zero accelerometer signals and other).

 ANNs are known in which information from external, not included in ANNs, speed meters or object coordinates is used to damp these vibrational components of errors. The disadvantages of such systems are their autonomy, complexity and high cost due to the use of dynamic filters for processing signals from external speed and coordinate meters.

 Also known are ANNs in which corrective devices with special-purpose transfer functions are used in the gyro-platform control channels to damp the oscillatory components of the errors indicated above and to preserve the gyro-platform unperturbed by the speeds and accelerations of the object. The disadvantage of such systems is the complexity of the transfer functions of corrective devices, in particular, the high order of the numerator polynomials, which complicates their practical implementation.

 Closest to the technical nature of the claimed device is an ANN containing a gyro platform with an accelerometer and a gyroscope in each of the two horizontal channels and a gyroscope in the azimuth channel, two identical circuits, respectively, in the first and second horizontal channels, each of which is made in series connected an integrator connected by its input to the accelerometer of the corresponding channel, the first scaling unit, the first adder and amplifier, the output of which is connected to the gyroscope input and the corresponding channel, as well as the second scaling unit, a coordinate and velocity determination unit common to both channels, the first and second inputs of which are connected to the outputs of the integrators of the first and second channels, respectively, and in each channel the output of the second scaling unit is connected to the second input of the first adder.

 The aim of the invention is to improve the accuracy of determining orientation angles, speeds and coordinates in the steady state horizontal movement of an object with a constant speed and constant heading.

 The goal is achieved by the fact that in the known ANN the first multiplication unit, the inverter and the second adder are connected in series to the first channel, the second input of which is connected to the accelerometer of the first channel, the first input of the first multiplication unit connected to the output of the integrator of the second channel, introduced in series connected to the second multiplication unit and the third adder, the second input of the third adder connected to the output of the accelerometer of the second channel, and the first input of the second multiplication unit connected to the integ Ator first channel, introduced as common to both channels, scaling unit having an input connected to the output determination unit velocities and coordinates on a signal sine latitude.

 In well-known ANNs, the use of internal connections between their elements for damping gyro platform oscillations leads to its perturbation by the object’s motion parameters with speed, acceleration, and acceleration change rate. In the proposed ANN, unlike the well-known technical solutions, with the help of additionally introduced adders, multipliers, a scaling element, and an inverter, corrections to the gyro platform control signals are formed, which provide autonomous damping of the gyro platform oscillations while maintaining its unperturbation in the steady-state horizontal mode of the object at a constant speed and with constant course.

 In FIG. 1 shows a structural diagram of an ANN; in FIG. 2 is a functional block diagram of the calculation of speeds and coordinates.

 ANN consists (Fig. 1) of gyro platform 1 connected in two horizontal channels with the first 2 and second 3 accelerometers and the first 4 and second 5 gyroscopes, and in the azimuth channel with the third gyroscope 6, as well as the first 7 and second 8 integrators and block 9 for determining speeds and coordinates. The outputs of the first 2 and second 3 accelerometers are connected respectively to the inputs of the first 7 and second 8 integrators, as well as to the first inputs of the ninth 10 and tenth 11 adders, the second inputs of which are connected respectively with the output of the sixth multiplier 12 and through the third inverter 13 with the output of the seventh multiplier 14 The first inputs of the sixth 12 and seventh 14 multipliers are connected respectively with the outputs of the second 8 and first 7 integrators, and the second inputs, through the seventh scaling element 15, are connected with the sixth output of the speed and coordinate calculation unit 9. The outputs of the ninth adder 10 and the first integrator 7, respectively, through the first 16 and third 17 scaling elements are connected to the inputs of the first adder 18, the output of which through the first correction amplifier 19 is connected to the input of the first gyroscope 4. The outputs of the tenth adder 11 and the second integrator 8, respectively, through the second 20 and the fourth 21 scaling elements are connected to the inputs of the second adder 22, the output of which through the second correction amplifier 23 is connected to the input of the second gyroscope 5.

 Block 9 calculation of speeds and coordinates (Fig. 2) consists of five multipliers 24-28, the first 29 and second 30 dividers of three integrators 31, 32, 33, six adders 34-39, the first 40 and second 41 sine converters, the first 42 and the second 43 cosine converters, the first 44 and the second 45 inverters, two scaling elements 46, 47 and four signal sets 48-51.

 The first inputs of the first 24 and second 25 multipliers are connected to the output of the first integrator 7, and the second inputs are respectively the outputs of the first cosine 42 and the first sine 40 converters. The first inputs of the third 26 and fourth 27 multipliers are connected to the output of the second integrator 8, the second input of the third multiplier 26 and through the first inverter 44 the second input of the fourth multiplier 27 are connected respectively to the outputs of the first cosine 42 and the first sine 40 converters. The outputs of the second 25 and third 26 multipliers are connected to the inputs of the third adder 34, the output of which through the fifth scaling element 46 and the third integrator 31 is connected to the first input of the fourth adder 35. In turn, the second input of the latter is connected to the output of the first signal generator 48, and the output with the inputs of the second sine 41 and second cosine 43 converters. The outputs of the first 24 and fourth 27 multipliers are connected to the inputs of the fifth adder 36, the output of which through the sixth scaling element 47 is connected to the first input of the first divider 29 and the input of the second inverter 45 connected to the first input of the fifth multiplier 28. In turn, the second input of the last is connected to the output of the second divider 30, connected by the inputs to the output of the second sine 41 and second cosine 43 of the converters, and the output through the fourth integrator 32 is connected to the first input of the sixth adder 37. The second input of the latter is connected with the output of the second setter 49 signals, and the output with the input of the first sine 40 and the first cosine 42 converters. The output of the first divider 29, connected by the second input to the output of the second cosine converter 43, is connected to the first input of the seventh adder 38, the second input of which is connected to the output of the third signal setter 50, and the output through the fifth integrator 33 to the first input of the eighth adder 39, connected by the second the input with the output of the fourth setter 51 signals. The outputs of the third 34, fourth 35, fifth 36, sixth 37, eighth 39 adders and the output of the second sine converter 41 are the first to sixth outputs of the unit 9 for calculating speeds and coordinates and at the same time the outputs of the system. The sixth output of the speed and coordinate calculation unit 9 — the output of the second sine transducer 41, is connected through the seventh scaling element 15 to the inputs of the sixth 12 and seventh 14 multipliers.

 ANN operates as follows.

 In the steady state of the object’s movement, the horizontal control channels, the first channel, the first accelerometer 2, the ninth adder 10, the first scaling element 16, the first integrator 7, the third scaling element 17, the first adder 18, the first correction amplifier 19, the first gyroscope 4, the second channel, the second accelerometer 3, the tenth adder 11, the second scaling element 20, the second integrator 8, the fourth scaling element 21, the second adder 22, the second correction amplifier 23, the second gyroscope 5 carry out the orientation of the gyro platform 1 relative tionary plane of the horizon. In this case, the presence in the horizontal control channels of the connections according to the signals of the first 2 and second 3 accelerometers provides damping of the gyro platform 1. The third gyroscope 6 stabilizes the position of the gyro platform in azimuth relative to the inertial space, i.e. gyro platform 1 is free in azimuth.

The output signals of the first 2 and second 3 accelerometers a ₁ and ₂ are respectively fed to the inputs of the first 7 and second 8 integrators, the outputs of which generate signals proportional to the components V ₁ , V _{2 of the} absolute speed of the object, acting along the sensitivity axes of the first 2 and second 3 accelerometers.

(V_E/R)tdφdt, (1)
φ=φ_o+

(V_N/R)dt,
λ= λ_o+

(V_E/Rcosω₂φ-ω₃)dt, где V_E, V_N - постоянная и северная составляющие абсолютной скорости объекта;
χ - угол разворота гироплатформы в азимуте, положительное значение - при повороте платформы к западу от меридиана;
φ - географическая широта местоположения объекта;
λ - долгота местоположения объекта;
χ_o,φ_o,λ_o - начальные значения соответствующих координат;
ω₃ - угловая скорость суточного вращения Земли;
R - радиус сферической модели Земли.From the outputs of the first 7 and second 8 integrators, the signals are fed to the inputs of the speed and coordinate calculation unit 9, in which, in accordance with the functional diagram shown in FIG. 2, the following parameters are calculated according to the corresponding dependencies:
V _E = V ₁ cosχ-V ₂ sinχ,
V _N = V ₁ sinχ + V ₂ cosχ,
χ = χ _o -

(V _E / R) tdφdt, (1)
φ = φ _o +

(V _N / R) dt,
λ = λ _o +

(V _E / Rcosω ₂ φ-ω ₃ ) dt, where V _E , V _N are the constant and northern components of the absolute speed of the object;
χ is the angle of rotation of the gyro platform in azimuth, a positive value is when the platform rotates west of the meridian;
φ is the geographical latitude of the location of the object;
λ is the longitude of the location of the object;
χ _o , φ _o , λ _o - the initial values of the corresponding coordinates;
ω ₃ - the angular velocity of the daily rotation of the Earth;
R is the radius of the spherical model of the Earth.

The value of the angular velocity of the daily rotation of the Earth and the initial values of the coordinates χ _o , φ _o , λ _o are introduced into the circuit of the unit 9 for calculating the velocities and coordinates using the third 50, second 49, first 48 and fourth 51 signal adjusters, respectively (Fig. 2 )

The signals generated at the outputs of block 9 for calculating the velocities and coordinates are proportional to the components V _E , V _{N of the} absolute speed of the object and its coordinates χ, φ, X, are output for the proposed ANN.

The second inputs of the ninth 10 and tenth 11 adders from the outputs of the sixth multiplier 12 and the third inverter 13, respectively, are fed with the correction signals Δa ₁ , Δa ₂ , formed in accordance with the structural diagram shown in FIG. 1, by the following relations:
Δa ₁ = ω ₃ V ₂ sinφ,
Δa ₂ = -ω ₃ V ₁ sinφ. (2)
The indicated connections in the steady-state mode of horizontal movement of an object with a constant speed and a constant course ensure that the gyro platform 1 is unperturbed by the rate of change of the absolute acceleration of the object when there are links in the system that provide damping of the gyro platform 1 oscillations.

 The ability to achieve a positive effect in the proposed technical solution is confirmed by the following.

-ω_Зv₂sinφ,
w₂=

+ω₃v₁sinφ, (3) где

,

- составляющие относительного ускорения объекта.The absolute accelerations w ₁ , w ₂ , acting along the sensitivity axes of the first 2 and second 3 accelerometers, are determined by the relations (3):
w ₁ =

-ω ₃ v ₂ sinφ,
w ₂ =

+ ω ₃ v ₁ sinφ, (3) where

,

- components of the relative acceleration of the object.

,

относительного ускорения равны нулю, т.е.

=

=0 . При условии, что погрешности ориентации α₁,α₂ гироплатформы 1 относительно плоскости горизонта - малы, в рассматриваемом случае движения объекта ускорения а_1n, a_2n измеряемые первым 2 и вторым 3 акселерометрами, в первом приближении описываются соотношением (4):
a_1n=w₁+ω₃α₂,
a_2n=w₂-ω₃α₁, (4) где ω₃ = g(V₁ ²+V₂ ²)R - вертикальное ускорение.When moving an object with a constant speed and a constant course, the components

,

relative acceleration are zero, i.e.

=

= 0. Provided that the orientation errors α ₁ , α _{2 of the} gyro platform 1 relative to the horizon plane are small, in the case under consideration the movements of the acceleration object a _1n , a _2n measured by the first 2 and second 3 accelerometers are described, in a first approximation, by the relation (4):
a _1n = w ₁ + ω ₃ α ₂ ,
a _2n = w ₂ -ω ₃ α ₁ , (4) where ω ₃ = g (V ₁ ² + V ₂ ² ) R is the vertical acceleration.

,
α₂ ^у= c₂w₁, (5) где с₁, с₂ - коэффициенты передачи первого 16 и второго 20 масштабирующих элементов.In the prototype, the use of accelerations a _1n , a _2n to damp the oscillations of the gyro platform 1 leads to disturbance by its rate of change in absolute acceleration (2). Moreover, the established errors α ₁ ^y , α ₂ ^{for the} orientation of the gyro platform 1, which subsequently lead to errors at the output of the system, in the first approximation have the form (2)
α ₁ ^y = -c

,
α ₂ ^у = c ₂ w ₁ , (5) where с ₁ , с ₂ are transmission coefficients of the first 16 and second 20 scaling elements.

= -

ω_Зv₂(v₁sinχ+v₂cosχ),

= -

ω_Зv₁(v₁sinχ+v₂cosχ), (6) следовательно α $\genfrac{}{}{0ex}{}{\text{y}}{\text{1}}$ ≠0, α $\genfrac{}{}{0ex}{}{\text{y}}{\text{2}}$ ≠0 .For the case under consideration, the movement of the object

= -

ω _З v ₂ (v ₁ sinχ + v ₂ cosχ),

= -

ω _З v ₁ (v ₁ sinχ + v ₂ cosχ), (6) therefore α $\genfrac{}{}{0ex}{}{\text{y}}{}$$\genfrac{}{}{0ex}{}{}{\text{1}}$ ≠ 0, α $\genfrac{}{}{0ex}{}{\text{y}}{}$$\genfrac{}{}{0ex}{}{}{\text{2}}$ ≠ 0.

(w₂+Δa₂),
α $\genfrac{}{}{0ex}{}{\text{y}}{\text{2}}$ = c₂

(w₁+Δa₁) (7) Подставляя в (7) выражения (2) и (3) для рассматриваемого случая движения объекта, получают α₁ ^у=0,α₂ ^у=0 .In the proposed ANN, the correction signals Δa ₁ , Δa ₂ generated according to (2) are fed to the second inputs of the ninth 10 and tenth 11 adders, where they are added to the signals of the first 2 and second 3 accelerometers. Moreover, the established errors α ₁ ^y , α ₂ ^{for the} orientation of the gyro platform 1 in the first approximation are described by the relations
α $\genfrac{}{}{0ex}{}{\text{y}}{}$$\genfrac{}{}{0ex}{}{}{\text{1}}$ = c

(w ₂ + Δa ₂ ),
α $\genfrac{}{}{0ex}{}{\text{y}}{}$$\genfrac{}{}{0ex}{}{}{\text{2}}$ = c ₂

(w ₁ + Δa ₁ ) (7) Substituting expressions (2) and (3) in (7) for the case of the object in question, we obtain α ₁ ^у = 0, α ₂ ^у = 0.

 Thus, in the inventive ANN, in contrast to the prototype, with horizontal movement of the object with constant speed and course, the gyroplatform 1 remains unperturbed in the presence of connections providing damping of its vibrations. This improves the accuracy of determining orientation angles, speeds and coordinates.

Claims (1)

 Inertial navigation system containing a gyro platform with an accelerometer and a gyroscope in each of the two horizontal channels and a gyroscope in the azimuth channel, two identical circuits in the first and second horizontal channels, respectively, each of which is made in the form of series-connected integrator connected to the accelerometer of the corresponding channel by its input , the first scaling unit, the first adder and amplifier, the output of which is connected to the input of the gyroscope of the corresponding channel, as well as the second ma a scaling unit, a common unit for both channels of coordinates and velocities, the first and second inputs of which are connected to the outputs of the integrators of the first and second channels, respectively, and in each channel the output of the second scaling unit is connected to the second input of the first adder, characterized in that, for the purpose to increase the accuracy of determining orientation angles, velocities and coordinates in the steady-state mode of horizontal movement of the object with a constant speed and a constant course, they are introduced sequentially into the first channel with the first multiplication unit, the inverter and the second adder, the second input of which is connected to the accelerometer of the first channel, the first input of the first multiplication unit connected to the output of the integrator of the second channel, the second multiplication unit and the third adder connected in series to the second channel, the second input of the third adder connected to the output of the accelerometer of the second channel, and the first input of the second multiplication block is connected to the output of the integrator of the first channel, a scaling block common to both channels is also introduced, for which it is connected to the output of the unit for determining speeds and coordinates by the sine signal of the latitude of the place, and the output is connected to the second inputs of the first and second multiplication units.

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