RU2578049C1 - Method of determining direction of geographic north using molecular-electronic angular speed sensor and inclination angle sensor - Google Patents

Abstract

FIELD: geography.

SUBSTANCE: invention relates to navigation devices, in particular can be used for determining direction of geographic north. Technical result is achieved due to that device for determining direction of geographic north, includes in addition to sensor of angular motion sensor which is sensitive to change angle of inclination. Signal processing is performed by elimination of angular motion sensor signal signals caused by slopes rotation axis, using readings of installed on same platform sensor which is sensitive to changes in inclination angle. At beginning of platform rotation is determined based on stabilisation of electrode current fixed molecular-electronic sensor. To reduce time of stabilisation of electrode current preliminary mechanically mixed fluid in angular velocity sensor by vibration platform or is placed in liquid outside region where transforming element angular velocity sensor additional electrodes located at same electric potential.

EFFECT: high accuracy of determining direction of geographic north.

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Description

The invention relates to navigation devices, in particular, can be used by devices to determine the direction to the geographical north.

A rather urgent task of the current stage of technological development is the problem of accurately linking various measuring and navigation systems to the true direction to the geographical north. The relevance of the problem of high-precision determination of true azimuth is emphasized by a number of practical applications in orienting, navigating, solving problems of target designation and determining the direction to an object, high-precision orientation of communication systems, geodesy, etc.

The traditional way to determine the azimuth is to measure the direction using a magnetic compass, taking into account (or without) the magnetic declination of the terrain. Despite the fact that this method has been known for a long time, the mismatch of the magnetic and geographical poles, the presence of magnetic anomalies or magnetized objects nearby, makes the use of a compass to determine the direction to the geographical north not accurate enough to solve the indicated problems.

The solution of the problem of positioning and determining the direction of movement in some cases can be achieved using modern satellite systems, such as GPS / GLONAS. However, these methods based on external signals, by definition, are not autonomous, which may be crucial for some applications, for example, for solving navigation problems of underwater vehicles or positioning in closed or underground objects, in addition, to achieve high accuracy in determining directions it is necessary to carry out measurements at several points remote from each other, as well as the use of high-precision signal receivers that provide a small error in determining the coordinates of waiting point.

Modern methods of high-precision orientation determination include the widespread use of various gyrocompass devices [1]. However, the use of high-precision gyrocompasses with an accuracy of determining the azimuthal direction is better than 0.5 °, is significantly limited by their cost, consumption and weight and size parameters.

An alternative to the established trend for the development of various gyroscopic systems for solving the problem of determining the direction can be an autonomous method of finding the azimuth of an object, based on finding the vector of the angular velocity of rotation of the Earth by measuring the Coriolis forces using a linear accelerometer rotating around a certain axis parallel to the sensitivity axis of this accelerometer [2 ]. At the same time, the accuracy of this method is small due to the small Coriolis forces in comparison with a typical external noise vibration background.

с помощью углового акселерометра, вращающегося относительно оси, ортогональной оси чувствительности этого акселерометра. Суть метода заключается в модуляции сигнала скорости вращения земли принудительным механическим вращением углового акселерометра. В случае, когда ось вращения непараллельна $${\overrightarrow{\Omega }}_3$$

, проекция ω₃ вектора угловой скорости вращения Земли на ось чувствительности углового акселерометра, а значит и его выходной сигнал, периодически изменяются при вращении акселерометра, что позволяет определить положения оси чувствительности, лежащие в одной плоскости с вектором угловой скорости вращения Земли $${\overrightarrow{\Omega }}_3$$

, а значит и направление на географический север [3, 4]. Описываемый метод мог бы быть довольно эффективным при наличии достаточно чувствительного измерителя углового движения. Вместе с тем, доступные до недавнего времени угловые датчики движения, включая микроэлектромеханические и волоконно-оптические, не позволяют получить необходимую высокую точность при их применении. Тем не менее, решение задачи высокоточного определения азимутального направления с помощью данного метода достижимо при использовании более чувствительного и точного углового сенсора. В качестве такого сенсора может быть использован угловой датчик, построенный на принципах молекулярно-электронной технологии [5-10]. Описываемое решение реализовано в патенте [11]. Кроме того, близким аналогом является патент [12] на инерционный определитель направления на географический север. Решение представляет собой негироскопическую инерционную систему, позволяющую определять азимут на географический север. Система функционирует с использованием жидкостного углового акселерометра, установленного на вращающуюся платформу. Датчик углового движения устанавливается на платформу, способную вращаться с некоторой постоянной угловой скоростью так, чтобы его ось чувствительности к угловому движению была ортогональна вектору угловой скорости вращения платформы. Стоит обратить внимание, что в обоих прототипах ось вращения платформы выставлена по направлению вектора силы тяжести.Another, more attractive option from the point of view of technical implementation and the achievability of high accuracy in determining the direction of the geographical north, can be the well-known method based on the direct determination of the angular velocity of the Earth’s rotation $${\overrightarrow{\Omega }}_3$$

using an angular accelerometer rotating about an axis orthogonal to the sensitivity axis of this accelerometer. The essence of the method is to modulate the signal of the speed of rotation of the earth by forced mechanical rotation of the angular accelerometer. In the case where the axis of rotation is not parallel $${\overrightarrow{\Omega }}_3$$

, the projection ω _{3 of the} vector of the angular velocity of the Earth’s rotation on the sensitivity axis of the angular accelerometer, and hence its output signal, periodically changes during the rotation of the accelerometer, which allows us to determine the positions of the sensitivity axis lying in the same plane as the angular velocity vector of the Earth $${\overrightarrow{\Omega }}_3$$

, and hence the direction to the geographical north [3, 4]. The described method could be quite effective in the presence of a sufficiently sensitive angular motion meter. At the same time, until recently, angular motion sensors, including microelectromechanical and fiber-optic, do not allow to obtain the necessary high accuracy in their application. Nevertheless, the solution of the problem of high-precision determination of the azimuthal direction using this method is achievable using a more sensitive and accurate angular sensor. An angular sensor based on the principles of molecular-electronic technology can be used as such a sensor [5-10]. The described solution is implemented in the patent [11]. In addition, a close analogue is the patent [12] for the inertial determinant of the direction to the geographical north. The solution is a non-gyroscopic inertial system that allows you to determine the azimuth to the geographical north. The system operates using a liquid angle accelerometer mounted on a rotating platform. The angular motion sensor is mounted on a platform capable of rotating with a certain constant angular velocity so that its axis of sensitivity to angular motion is orthogonal to the angular velocity vector of the platform. It is worth noting that in both prototypes the axis of rotation of the platform is set in the direction of the gravity vector.

The method of compensating for errors caused by the inclination of the axis of rotation of the platform, described in the application [13], is a prototype of the proposed technical solution. In this method, in addition to the angular motion sensor, an inclination sensor is installed on the rotating platform, the readings of which are taken into account when processing the output signals of the angular velocity sensor. However, this does not take into account errors associated with the instability in time of the sensitivity of angular motion sensors to linear accelerations, in particular, gravitational accelerations. In addition, the implementation of this method is carried out without taking into account the time it takes to stabilize the electrode currents in the channel of the angular motion sensor, the reduction of which is important from the point of view of most practical applications of determining the direction to the geographic north.

The objective of the invention is to provide a method for determining the direction of the geographical north, aimed at eliminating the aforementioned disadvantages.

The invention allows to determine the direction to the geographical north with high accuracy comparable to the accuracy of modern precision gyrocompasses without special high-precision leveling. The invention allows to create devices with small dimensions, low power consumption and low weight of the product, and allows measurements in difficult conditions when it is not possible to use other means of navigation. The application of the proposed method allows you to compensate for the perturbation of the output signal of the device caused by a change in the output signal of the sensor when its orientation changes with respect to gravity, which allows you to determine the orientation to geographic north without special leveling conditions with an accuracy corresponding to modern gyrocompasses and gyroscopic devices and reduces the measurement time . The claimed technical solution allows to reduce the time to determine the direction to the geographic north when implementing the method in accordance with the invention by reducing the time interval required to establish stabilization of electrode currents in the channel of the angular velocity sensor.

The specified technical result is achieved by the fact that in the method of determining the direction to the geographical north, which consists in the joint processing of the output signals of the molecular electronic angular velocity sensor and the inclination sensor installed on a single platform capable of rotating with an angular speed that varies in sign and absolute value, with which rotate the platform sequentially counterclockwise and clockwise with the same absolute value of the angular velocity, and the direction of geographical sowing p determined from the following equation:

(1 + R ² ) sin (ϕ ₀ -β ₀ ) -2Rsin (ε-ϕ ₀ -β ₀ ) = 0,

where R and ε are the ratio of the amplitudes of the signals and the phase difference of the signals of the angular velocity sensor at a frequency of rotation when rotating counterclockwise and clockwise,

φ ₀ - the desired angle that determines the direction to the geographical north, relative to the initial position of the platform,

β ₀ - the angle determined by the readings of the tilt sensor according to the expression:

β ₀ = δ / 2 ± π / 2,

where δ is the phase difference of the signals of the tilt sensor during counterclockwise and clockwise rotation,

rotation of the platform is carried out from the moment of stabilization of the electrode currents of the stationary molecular electronic angular velocity sensor, and to reduce the stabilization time of the electrode currents, the fluid is mechanically pre-mixed in the channel of the angular velocity sensor by vibration of the platform or additional electrodes are placed in the liquid outside the transducer element of the angular velocity sensor located at the same electric potential. As an inclination sensor, an accelerometer or an inclinometer or a linear speed sensor are used.

Correction of errors related to the sensitivity of the sensor of angular movements to the inclination of the axis of rotation is performed by eliminating the signals caused by the indicated inclination using two series of experiments consisting of sequential rotation of the platform counterclockwise and clockwise.

The essence of the proposed method for determining the direction to the geographical north is illustrated by graphic materials.

In FIG. Figure 1 shows an example of an experimental setup for determining the direction to the geographic north based on molecular-electronic angular acceleration meters and a sensor that is sensitive to changes in the angle of inclination mounted on the same platform.

In FIG. Figure 2 shows an angular velocity sensor mounted on a moving platform in accordance with the analogue solution [11] and introduced a coordinate system whose axis Ζ is directed along the axis of rotation of the platform, the X axis is perpendicular to the plane of the toroid, i.e. along the sensitivity axis of the angular motion sensor. The Y axis complements the coordinate system to the right triple, α is the angle of inclination of the axis of rotation relative to the vertical, β is the angle between the plane ΟΧΖ and the plane containing the axis Ζ and the gravity vector g, γ is the angle between OZ and the direction of the local meridian, φ is counted against clockwise, the angle between the planes ΟΧΖ and the plane (φ ₀ is the corresponding angle at the initial moment of time) containing the vector of the angular velocity of rotation of the Earth and the axis ΟΖ, Ω is the vector of the speed of rotation of the Earth.

In FIG. Figure 3 shows examples of the curves for establishing the interelectrode current in a molecular electronic angular velocity sensor after applying a potential to the electrodes. Blue - a curve - a motionless platform, red - a platform vibrating with small amplitude.

The method can be implemented on the basis of a device for determining the direction to geographic north, which contains, in addition to the angular velocity sensor installed and set in motion in accordance with the solution of the analogue [11], also a sensor sensitive to a change in the angle of inclination, by which error correction related to the sensitivity of the sensor of angular movements to the inclination of the axis of rotation. In turn, errors are recorded by eliminating signals caused by the indicated inclinations using the readings of a sensor installed on the same platform that is sensitive to changes in the angle of inclination from the signal of the angular motion sensor.

The determination of the direction to the geographical north with high accuracy comparable with the accuracy of modern precision gyrocompasses without special high-precision leveling is provided by compensating for the disturbance of the output signal of the device caused by a change in the output signal of the sensor when its orientation changes with respect to gravity.

One of the problems that must be solved for the effective use of molecular-electronic angular motion sensors to determine the direction to the geographic north is to compensate for disturbances in the output signal caused by a change in the output signal of the sensor when its orientation changes with respect to gravity. In the description of the patent [11], a solution is proposed related to the exact exposure of the axis of rotation of the platform in the direction of the local vertical. Indeed, in this case, rotation does not change the orientation of the sensor with respect to gravity. However, this solution cannot always be implemented technically with the necessary accuracy. Moreover, the device proposed in the patent [11] does not provide any devices for controlling the verticality of the axis of rotation of the platform and, if necessary, correcting its position. Let us determine how errors related to a change in its position with respect to gravity can be corrected if the axis of rotation of the platform is not vertical. For this, consider FIG. 2 sensor rotating relative to one of the axes located in the plane of the toroidal channel of its housing. We introduce a coordinate system whose Z axis is directed along the axis of rotation of the platform, the X axis is oriented perpendicular to the plane of the toroid, i.e. along the sensitivity axis of the angular motion sensor. The Y axis complements the coordinate system to the right triple. We introduce the following notation: α is the angle of inclination of the axis of rotation relative to the vertical, β is the angle between the OXZ plane and the plane containing the Z axis and the gravity vector g. Then the projection of the gravity vector on the axis of the selected coordinate system will be:

Suppose, in addition, that γ is the angle between OZ and the direction of the local meridian, φ is the counterclockwise angle between the OXZ planes and the plane containing the angular velocity vector of the Earth's rotation and the OZ axis. Then the projection of the angular velocity of the Earth’s rotation Ω on the sensitivity axis of the sensor will be:

. В реальности плотность жидкости не является строго постоянной, а зависит, в частности, от изменения ее концентрации или наличия температурных градиентов. Не делая каких-то априорных предположений о характере распределения плотности, в рамках линейного отклика, момент сил, приводящих в движение жидкость, находящуюся в канале тороида, может быть записан в виде:If the fluid in the toroidal channel of the angular motion sensor were strictly homogeneous, then the moment of inertia forces creating the fluid circulation in the channel would be $$M=m{R}^2{\dot{\Omega }}_x$$

. In reality, the density of the liquid is not strictly constant, but depends, in particular, on a change in its concentration or the presence of temperature gradients. Without making any a priori assumptions about the nature of the density distribution, within the framework of the linear response, the moment of forces driving a fluid located in the toroid channel can be written in the form:

The coefficients A _z , A _y take into account the heterogeneity of the distribution of fluid density in the channel of the toroid and the sensitivity of the sensor to linear accelerations caused by this heterogeneity. In this calculation, these coefficients should be considered as a priori unknown and subject to determination on the basis of experimental data.

Suppose that the platform rotates counterclockwise with an angular velocity ω. Then:

Here β ₀ , ϕ ₀ are the values of the corresponding angles at the initial time t = 0. We substitute (1), (2), (4) in (3) and, preserving only the time-dependent terms, we obtain:

Let W (ω) denote the complex coefficient of transformation of the moment of forces M into the output signal of the sensor. Using (5), we find for the output signal when rotating counterclockwise:

Here f _E = mR ² Ωωsinγ; f _G = A _y gsinα.

Similarly, to rotate in the opposite direction:

Calculating the ratio of (6) to (7), we find:

, R, ε, соответственно, амплитуда и фаза соотношения $$\frac{U_{ccw}(\omega )}{U_{cw}(\omega )}$$

. Поскольку U_ccw, U_cw - экспериментально определяемые выходные сигнала датчика угловых движений. Соответственно, R, ε следует рассматривать как величины, определяемые из эксперимента. Решая (8), относительно G, найдем:Here $$G=\raisebox{1ex}{$f_G$}\!\left/ \!\raisebox{-1ex}{$f_E$}\right.$$

, R, ε, respectively, the amplitude and phase of the relation $$\frac{U_{ccw}(\omega )}{U_{cw}(\omega )}$$

. Since U _ccw , U _cw are the experimentally determined output signals of the angular motion sensor. Accordingly, R, ε should be considered as quantities determined from experiment. Solving (8), with respect to G, we find:

We take into account that G is a real value, and we get:

Thus, if the direction of inclination of the axis of rotation (angle β ₀ in our description) were known, then the error associated with the deviation of the axis of rotation of the platform from the vertical could be eliminated and the direction of the angular velocity of the Earth's rotation relative to the initial position of the platform could be determined by determining ϕ ₀ from equation (10).

In turn, to determine the angle β ₀ , the following method can be proposed:

Simultaneously with the angular velocity sensor, a sensor sensitive to gravity (inclination angle), for example, an accelerometer, is placed on the platform.

Let, for simplicity, the sensitivity axis of the indicated accelerometer be directed along the OY axis, i.e. lies in the plane of the toroid. Then, the accelerometer output signals measured in the experiment, when rotating counterclockwise or clockwise, are given by the following expressions:

For the ratio of output signals:

From here:

which allows us to determine the unknown angle β ₀ , based on the experimentally determined value δ. The combined solutions of (10) and (14) allow us to find, in particular, ϕ ₀ , i.e. direction to the geographical north, eliminating errors associated with the influence of the gravity field on the output signal of the angular velocity sensor. Note that the choice between the signs “+” and “-” in expression (18) does not affect the result.

From the above analysis it is seen that the described methods and the obtained mathematical expressions are applicable only under the condition that the coefficients f _E , f _G do not change during measurements. Moreover, the coefficient f _G is determined by the nature of the distribution of fluid density in the toroidal channel of the transducer. In turn, the density of the liquid depends on the distribution of temperature and concentration in the working channel. Both temperature and concentration depend on the time elapsed after applying voltage between the electrodes of the converting element.

On the other hand, the establishment of the distribution of the density of the liquid is accompanied by a change in the interelectrode current in the converting element. A typical time-dependent interelectrode current is illustrated by the curves shown in FIG. 3. The blue curve in figure 3 represents the establishment of the interelectrode current at rest, and for the red curve, the platform does not rotate, but vibrates with a small amplitude. It can be seen that the vibrations lead to a more rapid establishment of the interelectrode current. In this example, the stabilization time decreased from 60,000 seconds to 30,000 seconds, i.e. twice. The stabilization of the interelectrode current measured at rest indicates the completion of the establishment of the distribution of concentration and temperature in the working channel, and, consequently, the density of the working fluid. In turn, this means the stability of f _E and f _G and the possibility of using the above data processing method.

As can be seen from the presented curves, the settling time can be very significant. From the point of view of most practical applications, this time should be significantly reduced. Possible ways to reduce it may be mixing the liquid in the channel of the transducer by applying vibrations to the platform, which is carried out for 5-60 minutes, as illustrated in FIG. 3. At the same time, by regulating the amplitude of the vibrations, the intensity of mixing can be made much larger, which means significantly reducing the stabilization time.

Another way to equalize the concentration of the working fluid is to place additional electrodes at the same potential in the working channel of the converter. The concentration equalization mechanism consists in the fact that a reversible electrochemical reaction occurs on the electrodes

будет относительно более высокой, более интенсивно будет идти прямая реакция, в областях с относительно меньшей концентрацией - обратная реакция. Суммарным результатом электрохимических реакций будет быстрое установление пространственно однородной концентрации.The preferred direction of the reaction depends, with a fixed electrode potential, on the concentration of the components involved in the reaction. In those areas of the fluid adjacent to the electrodes, where the concentration of the active component $$I_3^{-}$$

it will be relatively higher, the direct reaction will be more intense, in the areas with a relatively lower concentration the reverse reaction will occur. The total result of electrochemical reactions will be the rapid establishment of a spatially uniform concentration.

Information sources.

1. Yu.A. Lukomsky, V.G. Peshekhonov, D.A. Skorokhodov, Navigation and traffic management. St. Petersburg: "Elmore", 2002.360 s.

2. J. Reiner, M. Naroditsky, Patent No. US 6502055 B1, G06F 15/00.

3. D.H. Titterton, J.L. Weston, "Strapdown inertial navigation technology", ISBN 0863412602, IEE Publishing, England.

4. B. Blazhnov, L. Nesteryuk, V. Peshekhonov, L. Staroseltsev, ELECTRONICS: Science, Technology, Business, 5/2001, P. 56-59.

5. V.A. Kozlov, Advances in Modern Radio Electronics, No. 5-6, 2004, S. 138-144.

6. Safonov M.V., Agafonov V.M., Kozlov V.A. Prospects for the use of molecular-electronic sensors of rotational motion in various scientific and technical fields // System Problems of Reliability, Quality, Information and Electronic Technologies / Materials of the X International Conference and the Russian Scientific School. Part 1. - M .: Radio and communications, 2005, S. 108.

7. Kozlov V.A., Safonov M.V. and others. "Molecular electronic device for measuring angular movements", patent of the Russian Federation for the invention No. 2323946, application No. 2005130308/28 (033961), 2005.

8. Zaitsev D.L., Kozlov V.A., Safonov M.V. and others. "A method of manufacturing an electrode assembly of a molecular-electronic meter of linear and angular movements with a low level of intrinsic noise", Patent Application No. 2006131449/280 (034193), 2006.

9. Bugaev A.S., Safonov M.V. "Molecular-electronic device for measuring mechanical movements", RF patent for utility model No. 82 862 U1, application No. 2008144490/22, 2008.

10. Zaitsev D.L., Egorov E.V., Egorov I.V. “Creation of a new element base for inertial navigation based on molecular-electronic technology” // Materials of the All-Russian Conference of Graduate Students and Students “Industry of Nanosystems and Materials”, Zelenograd, 2006. P. 105-109.

11. RF patent for utility model No. 89895 "Device for determining directions to the geographic north", authors: Agafonov V. M., Bugaev A. S., Zaitsev D. L., Safonov M. V., application No. 2009130794, publ. . 12/20/2009.

12. Patent US 2007095124.

13. Application No. 20112112374 dated 02.04.2012 A method for determining the direction to the geographic north using the signal of a molecular-electronic sensor of angular movements and compensation for errors associated with the influence of linear accelerations, authors Agafonov VM, Antonov AN, Zaitsev D. L.

Claims (4)

1. The method of determining the direction to the geographic north, which consists in the joint processing of the output signals of the molecular-electronic sensor of angular velocity and inclination sensor installed on a single platform that can rotate with an angular speed that changes in sign and absolute value, at which the platform is rotated sequentially against and clockwise with the same absolute value of the angular velocity, and the direction to the geographic north is determined from the following equation:
(1 + R ² ) sin (ϕ ₀ -β ₀ ) -2Rsin (ε-ϕ ₀ -β ₀ ) = 0,
where R and ε are the ratio of the amplitudes of the signals and the phase difference of the signals of the angular velocity sensor at a frequency of rotation when rotating counterclockwise and clockwise,
φ ₀ - the desired angle that determines the direction to the geographical north, relative to the initial position of the platform,
β ₀ - the angle determined by the readings of the tilt sensor according to the expression:
β ₀ = δ / 2 ± π / 2,
where δ is the phase difference of the signals of the tilt sensor during counterclockwise and clockwise rotation,
characterized in that the rotation of the platform is carried out from the moment of stabilization of the electrode currents of the stationary molecular electronic angular velocity sensor, moreover, the liquid is mechanically pre-mixed in the channel of the angular velocity sensor by vibration of the platform or additional electrodes located in the liquid outside the transducer element of the angular velocity sensor are located with the same electric potential. 2. The method according to p. 1, characterized in that an accelerometer is used as an inclination sensor. 3. The method according to p. 1, characterized in that as a tilt sensor use an inclinometer. 4. The method according to p. 1, characterized in that the linear speed sensor is used as an inclination sensor.

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