JPH1048305A - Tracking apparatus for communication satellite for mobile body communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a tracking apparatus by which the direction of an antenna beam can be directed to the direction of a satellite always with constant accuracy irrespective of the motion state of a mobile body. SOLUTION: A computing part 41 fetches outputs of a GPS 411 to a wheel speed sensor 414, it executes various computing and processing operations to the outputs, and it sends their results to an antenna control part 42 as control information. Thereby, an azimuth control voltage and an elevation control voltage are supplied respectively to servomotors 423, 4247 and an antenna 421 is directed to a satellite always with constant accuracy. At this time, inside the computing part 41, the frequency band of the sensor is divided into two parts as a high band and a low band in order to compute information on the motion such as the posture angle or the like of a mobile body, the rate gyro 412 is distributed to the side of the high band so as to be in charge, and the accelerometer 413 is distributed to the side of the low band so as to be in charge, and their distribution to be in charge is changed dynamically to an optimum value according to the motion state of the mobile body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite tracking apparatus for a satellite communication antenna mounted on a mobile body, and more particularly, to the motion information of the mobile body including its attitude angle, using sensor fusion processing.
The present invention relates to a communication satellite tracking device for mobile communication including a means for accurately measuring over a wide frequency range.

[0002]

2. Description of the Related Art Communication satellites and terrestrial mobiles (often
In communication with an automobile, a low frequency of about L band (1 to 2 GHz) is used. In particular, when the amount of information is not so large, an omnidirectional antenna is used. However, when handling a large amount of information transmission such as images, it is necessary to use a high frequency band, and due to the limitations of transmission power and reception resolution, an antenna having sharp directivity (in other words, a high gain antenna) Need to be used. When using an antenna having a sharp directivity, it is necessary to always direct the beam direction to the satellite. This is called tracking.

[0003] The tracking system is roughly classified into a closed loop system and an open loop system. The former is a method in which information of the received signal strength is used as a tracking control amount in some form, and a typical example is a monopulse method. FIG. 8 is a principle diagram of the monopulse method, and FIG. 9 shows a beam pattern of the antenna in the monopulse method. In FIG. 8, reference numeral 81 denotes a main reflecting mirror of the parabolic antenna, and reference numeral 82 denotes a sub-reflecting mirror, which is disposed at the focal point of the main reflecting mirror 81 described above. First, two feed horns 8 symmetrically arranged with respect to the main reflecting mirror axis.
Considering the case where 3a and 83b were used, the beams formed by these feed horns are denoted by A and B, respectively, as shown in FIG. FIG. 9 shows the directivity of the sum signal and the difference signal of the beams A and B. If the antenna thus configured is used as a receiving antenna and the antenna is driven so that the difference signal becomes zero, the antenna is correctly oriented in the direction of arrival of the radio wave. In order to discriminate between azimuth (azimuth) and elevation (elevation), four horns are combined, the sum of all horns is taken as a sum signal (communication signal), and the difference signal between the two sets of horns on the left and right is calculated. If the azimuth error signal is used, the difference signal between the upper and lower horns is used as the elevation error signal, and the antenna is driven so that both error signals become zero, the antenna can be correctly directed in the direction of the radio wave incidence. it can.

However, in the above-described closed-loop system, when a mobile body passes through an area where radio waves from a satellite cannot reach due to a tunnel or other obstacle, if the attitude of the mobile body changes significantly during that time, the mobile station is re-entered. When entering an area where there are no obstacles, it is necessary to return to the initial state and search for the arrival direction of the radio wave, and it is not possible to immediately return to the state of optimal directivity. Further, since the antenna requires at least four feed horns, the size of the antenna is increased, and a heavy burden is imposed on the tracking mechanism. Further, the algorithm for tracking the communication satellite is separated, and the burden on software increases. If there is no beacon radio wave from the satellite, transmission from the mobile to the satellite cannot be performed. In general, in satellite communication in which the frequency band is different between the uplink and the downlink, a tracking mechanism must be installed for each of these bands, and the tracking mechanism may be excessively large compared to a mobile body. There is.

[0005] On the other hand, as a device classified into the open-loop system, a device used in combination with an azimuth sensor such as a magnetic compass or a gyro compass and an inertial navigation device has been reported. However, the gyro compass is expensive, requires regular maintenance and inspection, and is unsuitable for use on a vehicle in terms of accuracy, reliability and economy. This is a change in the state of motion of the car (turning, accelerating,
This is because deceleration is more frequent than that of other moving objects (aircraft, ships, etc.), and the reliability of delicate mechanical mechanisms such as suspension lines is limited.

[0006] Under the circumstances described above, great expectations are placed on an open-loop system using a communication antenna system on a mobile object. For example, JP-A-6-177633 discloses an example of a system included in this category. In the present invention, the moving object is a global positioning system (global posi
The GPS receiver is equipped with a receiver of the traction system (hereinafter abbreviated as GPS), which enables the user to measure his / her own position from time to time and to know its speed and azimuth of traveling. Further, the moving body is equipped with means (acceleration sensor, inclinometer, etc.) for measuring the attitude angle. Generally, communication satellites are geostationary satellites, and their latitude, longitude, and altitude are known. Therefore,
The azimuth and elevation of the satellite with respect to the antenna mounting surface of the moving object can be calculated from the above-described various data, and based on this, the antenna control unit can direct the antenna to the satellite.

According to the present invention, the radio wave emitted from the communication satellite is not used for tracking control on the mobile body side.
Also, even if the moving body enters an area where reception is impossible due to obstacles or the like, as long as the GPS receiver is functioning, the antenna is directed in the correct direction, and at the same time passes through this area, restores normal communication functions. . In this method, expensive equipment requiring periodic maintenance, such as a gyrocompass, is not used, so that the system is inexpensive and the number of maintenance operations is greatly reduced.

[0008]

However, in the above-described communication satellite tracking device for mobile communication, the attitude angle of the mobile is measured using an inclinometer fixed thereto.
In general, a sensor fixed to a moving body converts a physical quantity into an electric quantity and outputs the electric quantity as a function of time. However, it is possible to consider a frequency component (Fourier component) for the electric quantity. Here, the inclinometer outputs an accurate value for a low frequency component, but an error increases for a high frequency component. Therefore, inaccurate tracking of the antenna cannot be avoided.

[0009]

In order to solve the above problems, the present invention employs the following means. That is, as means for detecting the attitude angle of the moving body, appropriate sensors are selected for the low frequency band and the high frequency band, respectively, and the entire frequency band is shared by these sensors. That is, the measurement accuracy is improved over a wide frequency band by introducing the sensor fusion processing. Specifically, an inclinometer as in a conventional example is used as a sensor in charge of a low frequency region, and a rate gyro using an optical fiber is used in a high frequency region. The function of the inclinometer described above is that the three inclinometers are arranged parallel to three orthogonal axes.
The output of the acceleration sensor can be substituted by performing an algebraic operation.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the structure of the present invention, the theoretical basis of the present invention will be described. In FIG. 1, the sphere means the earth, and NP and SP indicate the North Pole and the South Pole, respectively. S is (in most cases, geostationary satellite) communications satellites indicates, P ₃ is surface OS of the earth (O earth center) is the intersection of, and P ₀ is the position of the moving body. λ and λs
Is the elevation angle, Λ and Λs are the azimuth angles. Cartesian coordinates called local NED reference coordinate system at point P ₃ system x ₃ y ₃ z
Consider _three . This coordinate system is also called the navigational coordinate system, and x ₃
The axis is a straight line from the point P ₃ toward the North Pole (N), the y ₃ axis is a straight line from the point P ₃ toward the east (E), and the z ₃ axis is the earth center O (or immediately below, from the point P ₃ , It is a straight line toward D). If the radius of the earth is R ₀ , R ₀ is about 6.378
× 10 ⁶ m. Note that the altitude of the moving body, compared to the R _0,
Ignored because it is as small as three digits. The NED reference coordinate system is a rectangular coordinate system that can be considered at any point on the earth's surface.

Here, the unit vector S in the satellite S direction in the coordinate system P ₃ is

[0012]

(Equation 1)

It can be expressed as Equation (1) right-hand side is a matrix of three rows and one column, matrix elements of the first to third line are each x _3, y ₃
And z is a ₃ component. In addition, written on the left and right of S ₀
The [] mark is a symbol indicating that this quantity is a matrix (the same applies hereinafter). Next, as shown in the figure, the position of the moving body is set to P _0, and three points P ₁ , P ₂ and P ₃ are determined. Here, the unit vector unit that desires the satellite S from the origin P ₀ of the local NED reference coordinate system P ₀ (x ₀ y ₀ z ₀ coordinate system) is [S ₀ ]
Then, the following relationship is obtained by the Euler angle rotation coordinate transformation.

[0014]

(Equation 2)

When the altitude of the satellite is Hs, R ₀ ≪Hs
, The unit vector in the satellite direction in the coordinate system P ₃ [S
₃ ] may be analyzed using a vector translated spatially up to the coordinate system P _0, but if this condition is not satisfied, a unit vector pointing the satellite from the coordinate system P ₀ must be used. . 'By displaying the [S ₀ the vector [S _0]'] can be displayed as follows.

[0016]

(Equation 3)

Here, L is the distance from the measurement point P ₀ to the satellite S. On the other hand, in the coordinate system P ₀ , the azimuth (azimuth angle) θz and the elevation angle (elevation angle) θy of the satellite in this coordinate system can be expressed by the following equations, respectively.

[0018]

(Equation 4)

[0019]

(Equation 5)

However, here,

[0021]

(Equation 6)

## EQU1 ## Each matrix element of equation (6) is represented by equation (2)
To (6). NED reference coordinate system at (x ₀ y ₀ z ₀ Cartesian coordinate system), since Motoma' azimuth θz and elevation θy overlooking the satellite, then supplied to the satellite tracking mechanism including an antenna (42 in FIG. 4 described later) Find the control angle. Here, NE at the position of the moving body described above.
In addition to the D reference coordinate system, a moving object coordinate fixed to the moving object (or a sensor) and a tracking coordinate system fixed to the above-described satellite tracking mechanism are introduced. When tracking is successful, the x-axis of this coordinate system coincides with the center axis of the antenna beam. Therefore, this coordinate system is considered not to be constrained by the surroundings of the x-axis but to represent countless coordinates in which only the direction of the x-axis matches.

The moving body coordinate system (x ₁
spatial rotation matrix to y ₁ z ₁ coordinate system) [phi], its tracking coordinate system from the mobile coordinate system to (x ₂ y ₂ z ₂ coordinate system)
[ψ], and the tracking coordinate system from the NED reference coordinate system
[θ], these spatial rotation matrices have a relationship as shown in FIG. 2, and the following formula is established.

[0024]

(Equation 7)

Each of these matrices is a square matrix of 3 rows and 3 columns, and the specific form will be described below in order. Since the matrix operation is complicated, only the essential points will be described. First, [ψ] is represented by the product of three spatial rotation matrices.

[0026]

(Equation 8)

Where ψ _x , ψ _y and ψ _z are x,
Euler angles with the y and z axes as rotation axes. Therefore,

[0028]

(Equation 9)

Next, [θ] is given as a product of two spatial rotation matrices as follows.

[0030]

(Equation 10)

Here, θ _y and θ _z are Euler angles around the z and y axes, respectively. However, the Euler angle with the x axis as the rotation axis is zero, meaning that the antenna is not rotated around the x axis, in order to match the plane of polarization of the radio wave coming from the satellite to that of the antenna. . Next, a spatial rotation matrix [φ] related to the posture angle of the moving object, that is, the roll angle φ _x , the pitch angle φ _y, and the yaw angle φ _z will be discussed.

[0032]

[Equation 11]

Here, [φ] ^t means the transposed matrix of [φ], and the matrix element on the right side of equation (11) is given by the following equation.

[0034]

(Equation 12)

From equations (7), (10), (11) and (12),

[0036]

(Equation 13)

From the relationship of the equation (7), the right sides of the equations (9) and (13) (each having a matrix of 1 row and 3 columns) are equal, and corresponding matrix elements are also equal. Focusing on this fact, the following relationship is easily obtained.

[0038]

[Equation 14]

[0039]

(Equation 15)

Θ _y and θ _z are given by equations (4) and (5)
And c (1,1) to c (3,3) are functions of φ _x , φ _y and φ _z . Therefore, the control angle of the satellite tracking mechanism ψ
_y and [psi _z will become apparent as long demanded attitude angle phi _x, phi _y, and phi _z. The theory of Euler angles is described by Kanichiro Kato, "Introduction to Aircraft Mechanics" (The University of Tokyo Press)
Familiar with.

While the mobile object is kept stationary and the satellite is initially captured, θ _y and θ _z are known and φ _x
And φ _y use the values read from the inclinometer. When the scanning the phi _z between -Pai～pai, there is always received electric field becomes the maximum position. However, since the electric field fluctuation near the maximum value is gradual, two scanning angles at which this becomes the maximum value −3 dB are stored, and the center position of these is set as the maximum position of the received electric field, that is, the optimal pointing. Φ at that time
_z becomes the azimuth of the moving object, and the system alignment based on the radio wave arrival direction is completed.

The tracking when the moving object is stationary is performed by using the received electric field strength. During the running, the movement information of the moving object is fetched through the sensor, and the posture angle [φ], the position and the like of the moving object are detected in real time. The antenna control angle is calculated in accordance with the above-described equations. This performs satellite tracking. In order to perform stable tracking, it is, of course, necessary to improve the accuracy of all motion parameters.
The accuracy of [φ] is the largest and affects tracking performance. The role of the sensor is shared between the high band and the low band in the frequency domain, and the sharing ratio is rationally changed based on the motion parameter. The attitude angles φ _x , φ _y and φ _z are respectively expressed by the following equations (1)
According to the recurrence formula shown in 6), it is sequentially and approximately calculated. Here, for convenience of explanation of the calculation procedure, the symbols φ _{x to} φ _z are not used, and these are represented by c _n .

[0043]

(Equation 16)

[0044] Here, n: an integer indicating the order of sampling a _n: a low frequency region in charge of the sensor (inclinometer, GPS, etc.) angle output b _n of: angle output c _n of the high-frequency region assigned sensor (rate gyro): System angle output, ν _n : weight function (0 ≦ ν _n
≦ 1) K: Limit coefficient, α: Nonlinearization order Here, c ₀ (zero approximate value of c _n ) depends on the roll angle φ _x and the value obtained from the inclinometer in the case of the pitch angle φ _{y in} the case of the standstill, and in the case of the yaw angle φ _z it depends on the arrival direction of the radio wave. Use the value obtained from the system alignment. Using this equation, depending on the motion state of the system, α,
Optimum numerical values such as ν _n are set, and sensor fusion is performed in real time to improve the accuracy of the attitude angle.

Note that the sensor fusion processing is based on the precondition that data is acquired at the same time interval. However, among the sensors that make up the system, GPS
Has unique characteristics, such as unstable sampling, long intervals, or frequent data interruptions.Therefore, to apply to the processing method using the above recurrence formula, It involves various difficulties. Therefore, although the data itself has a large error in the high frequency region, the feedback amount is an extremely low frequency component. (1) In calculating the amount of feedback, data at the same time (of the system and the GPS) is used in association with each other as much as possible, and if that is not possible, the amount of feedback at the previous time is used as the amount of feedback at the current time. Let it. Note that the feedback amount is the first term on the right side of the above equation (16). (2) The feedback amount applied in the system operation loop is divided into the ratio of the system operation loop time to the GPS sampling time, and is applied to the system loop cycle. More specifically, it is assumed that the data operation cycle of the system loop is indicated by τ (sec), and that the sensors other than the GPS perform data sampling with a cycle at this time interval. In contrast, the GPS outputs data at time intervals T (sec). here,

[0046]

[Equation 17]

Where m is an integer significantly larger than 1. Assuming that the GPS output data fluctuates by β ° during the time T, the rate of change of the GPS data is β / T
(° / sec). Therefore, in the operation cycle of each system loop, the amount of change in the GPS output data is

[0048]

(Equation 18)

The operation is performed in this operation cycle. (3) When the instantaneous interruption of the GPS data occurs, the steady-state feedback is continued using the feedback amount of the loop cycle immediately before the instantaneous interruption detection. In the system, as shown in FIG. 3, the output of the wheel speed meter is used as a speed reference. First, consider the case where there is no feedback due to the reference speed, that is, the case where K ₁ = K ₂ = 0. The angular velocities are integrated to give the system attitude angle,
Further, the acceleration is integrated using this to obtain the system attitude. However, in this case, since the reference speed (wheel speedometer, etc.) is not utilized, if the angular velocity includes a constant term error, the order relating to time increases at the time of integration into the attitude angle, and the attitude angle Errors increase with time. If the acceleration is integrated using this as a factor, the error in system speed increases with time and diverges.

On the other hand, when K ₁ and K ₂ ≠ 0,
At the point of addition in the center of FIG. 3, the difference between the system speed output and the reference speed is obtained as a deviation, and is fed back to the input side. Thereby, the constant term error included in the sensor output is removed. This method can also be used to improve the pitch attitude angle. If there is an error in the value of the pitch angle, this leaks into the gravitational acceleration, causing a speed error. By taking a deviation between the reference speed and the system speed and applying negative feedback to the pitch angle with an appropriate gain, the accuracy of the pitch angle can be improved. This effect is remarkable when the moving body is accelerated or decelerated. The concept of these processes is represented by a recurrence formula as follows.

[0051]

[Equation 19]

[0052]

(Equation 20)

Here, ν _n : system output speed, _pn : system output pitch angle u _n : reference speed (here, output of wheel speed meter) K ₁ , K ₂ : feedback coefficient.

FIG. 4 shows an embodiment of the present invention. In this embodiment, a calculation unit 41 that processes output data of various sensors is provided.
It comprises an antenna control mechanism section 42 and a video receiving section 43. As described above, the initial acquisition of the satellite is performed by transmitting the radio wave arriving from the satellite to the plane antenna 421 with an azimuth of 360
This is performed by receiving while scanning in the ° range.
At this time, the received voltage is taken in as a spectrum analyzer 433 analog voltage via the BS tuner 431 and monitored. However, this received voltage is not used as tracking information while the moving object is running. Instead, the arithmetic unit 41 is supplied with the position and orientation information from the GPS 411, the angular velocity from the rate gyro 412, the acceleration from the acceleration sensor 412, and the reference speed from the wheel speedometer 414, and these data are The data is taken into the arithmetic unit 41 via various interfaces. The output of the acceleration sensor 412 is integrated with respect to time to obtain speed information, and is also subjected to algebraic calculation to perform a function equivalent to an inclinometer. The arithmetic unit 41 arithmetically processes the information by the above-described method, and outputs a control signal to the antenna control mechanism unit 42 while displaying various motion parameters on the plasma display 415 or the color liquid crystal display 416. This signal is taken into an azimuth / elevation angle control circuit 422, and based on this signal, the circuit outputs an azimuth / elevation control voltage to an azimuth servomotor 423 and an elevation servomotor 424, respectively. This always directs the antenna beam to the satellite with a certain degree of accuracy. The signal received by the planar antenna 421 is supplied to the BS tuner 431 and displayed on the television receiver 432.

FIG. 5 shows a schematic diagram of the software of the system. The GPS, rate gyro, acceleration sensor, and wheel speedometer are subjected to various types of processing, and a system output is prepared such as position, attitude angle, speed, antenna control information, satellite information, and the like. GP
The latitude, longitude, and altitude information derived from S are mainly used as low-frequency correction of system position information. G
The PS azimuth information is used for low-frequency correction of the system azimuth. The output of the rate gyro serves as a posture information source, and the posture information is held in a quaternion. The quaternion also incorporates other posture supplementary information to maintain a constant surface in real time. Based on this quaternion, the vector amount of the moving object coordinate system is expressed as N
A coordinate transformation matrix for performing coordinate transformation into a vector quantity of the ED reference coordinate system is generated. The posture angle of the moving object is calculated from the coordinate transformation matrix.

On the other hand, the output of the acceleration sensor is used as information of the inclinometer, and is converted into an NED reference coordinate system by a coordinate conversion matrix and integrated to obtain a speed in the NED reference coordinate system. This is integrated to calculate the position, obtain the speed of the moving body coordinate system again, determine the deviation from the wheel speedometer, and use it for speed correction and pitch angle correction. The satellite position information is used to calculate a control angle to be sent to the antenna tracking mechanism from the position and attitude of the moving object calculated by the system.

FIG. 5 shows an example of a flow chart of the system, in which a circle indicates a confluence where additive processing is mainly performed, a cross (x surrounded by a circle) indicates a confluence mainly performed for multiplication processing, and α ₁ Is the feedback coefficient of the roll angle, α ₂ is the feedback coefficient of the pitch angle, α ₃ is the feedback coefficient of the yaw angle (both are the processes corresponding to equation (16)), and β is the feedback coefficient of the velocity (equation (19) Corresponding processing). In FIG. 5, the underlined items on the left side indicate input sources of information, and those on the left side indicate generic names of output information. The roles and functions of the above items will be described sequentially. GPS The values of latitude, longitude, altitude and azimuth output from GPS are used.

Of these, the latitude, longitude and altitude are calculated from the deviation from the values immediately before calculated by the system, and are set as NE.
The speed deviation of the D reference coordinates is obtained. This is converted into a value in the moving body coordinate system using a conversion matrix, multiplied by a feedback coefficient β, converted into a value in the moving body coordinate system, and fed back as a speed deviation of the moving body coordinate system before the simple integration process. . In other words, it plays a role of preventing the divergence of the position error of the system using the GPS data.

The value of the azimuth angle is different from the above-mentioned one, and the deviation from the yaw angle immediately before calculated by the system is taken, and this value is used as a feedback amount to feed back to the yaw angular velocity region. Is described as a function of the speed information obtained from the wheel speedometer. This will be specifically described as follows. GP
Since the reliability of the output azimuth of S depends on the moving speed, at high speeds, the feedback coefficient is increased to increase the GPS dependence, and conversely, at low speeds, the feedback coefficient is decreased to decrease the GPS dependence. As a result, a wide azimuth accuracy can be maintained. The feature is that coefficients are operated continuously instead of separating thresholds and the like. Since the processing is different for each axis of the rate gyro, they will be described individually. Note that x, y, and z described here are based on the moving object coordinate system. The quaternion is composed of components of scalar 1 and vector 3 that secure posture information, and can be said to be an extension of the concept of complex numbers. The transformation matrix represents a vector quantity described in the moving body coordinate system by N
It is a 3-by-3 spatial rotation matrix to be converted into a value in the ED reference coordinate system.

The roll, pitch and yaw attitude angles are calculated from the transformation matrix and output. Further, a control azimuth angle and an elevation angle are calculated from the attitude angle and the elevation angle of the satellite azimuth at that point. x angular velocity The rotational angular velocity about the x-axis includes the roll angle (normal tilt) obtained from the acceleration (yield only in gravitational acceleration in the constant velocity linear motion) that appears in the y and z components of the acceleration sensor from the roll angle immediately before calculated by the system. (The output is the same as the one called the total meter). However,
The roll angle obtained from the acceleration sensor is basically acceleration other than gravitational acceleration, that is, starting acceleration, braking acceleration,
When centrifugal acceleration, vibration acceleration, and the like occur, a large error is caused. Therefore, in the case of the motion of a car, since a large centrifugal force is generated in the y direction when traveling on a curve, unless the roll angle dependence obtained from the acceleration sensor is reduced,
The accuracy of the entire system is reduced. Since the product of the yaw angular velocity and the velocity is proportional to the centrifugal acceleration in the y-direction, by describing the feedback coefficient as a function of this value, it is possible to prevent a decrease in the accuracy of the system when traveling on a curve. y angular velocity y
The rotation speed around the axis is the pitch angle obtained from the pitch angle immediately before the system calculates, and the pitch angle obtained from the acceleration (only the gravitational acceleration in the case of constant velocity linear motion) that appears in the x and z components of the acceleration sensor. The deviation obtained by subtracting the same is fed back to enhance the accuracy. This is exactly the same as for the x-axis, except that the wheel speed minus the previous speed calculated by the system is 1 /
g is multiplied and returned. The z-angular velocity sensor z-axis angular velocity has been described in the section on CPS, and will not be described. Acceleration sensor The output of the acceleration sensor calculates the velocity and the position as integral, and calculates the roll angle obtained by calculating the y and z components and the pitch angle obtained by calculating the x and z components, as reference information for feedback. Used as x acceleration rate In addition to being used as a factor to generate the gyro y-axis feedback pitch angle (not the system pitch angle), the speed obtained from the wheel speed meter is subtracted from the x speed just calculated by the system and returned to this. Multiply by the coefficient β and feed back.
This is input to the coordinate conversion processing as x acceleration in the moving object coordinate system. y acceleration rate In addition to being used as a generating element of the gyro x-axis feedback roll angle (not the system roll angle), the y velocity just before the system is calculated is subtracted, and this is converted as the y acceleration of the moving object coordinate system. Input to processing. This processing is based on the assumption that no speed occurs in the left-right direction of the vehicle. Z acceleration rate The gyro is used as a factor for generating the x-axis return roll angle (not the system roll angle) and the y-axis return pitch angle (not the system pitch angle). This is input to the coordinate conversion process as the y acceleration of the moving object coordinate system. This is a process assuming that no speed occurs in the vertical direction of the vehicle.

The above acceleration input is converted into N using a transformation matrix.
The speed is converted to the ED reference coordinate system and integrated to obtain the speed of the NED reference coordinate system. From this, in addition to calculating the latitude, longitude and altitude as the position, the speed of the moving body coordinate system is calculated by performing an inverse transformation to the moving body coordinate system. In particular, the speed in the x direction of the moving object coordinate system is output as the system speed (corresponding to the traveling speed of the vehicle). Wheel speed sensor The wheel speed from the wheel tachometer takes a deviation from the system speed and is fed back to x acceleration and y angular speed, which helps to improve the pitch attitude angle and the speed accuracy. The latitude, longitude and altitude of the satellite to be tracked are given as numerical values. From this and the position obtained from the system, the azimuth and elevation of the satellite in the NED reference coordinate system are calculated. Further, a control azimuth angle and a control elevation angle are calculated from the calculation with the system attitude angle. The strength of the radio wave from the spectrum analyzer satellite is read, and the electric field strength and the reception rate are evaluated.

FIGS. 6 and 7 show the results of an experiment conducted in a suburban area on a mobile communication communication satellite tracking device designed and prototyped based on the sensor fusion method shown in Expression (15). 6, the vertical axis indicates the pitch angle and the speed of the moving body, and the horizontal axis indicates the elapsed time. The upper part of FIG. 6 shows the pitch angle, and the bold line shows the output of the inclinometer, which shows that an offset (constant term) error is included during acceleration / deceleration. On the other hand, what is indicated by a thin line is the output of the system, and it can be seen that the effect of acceleration / deceleration has been considerably reduced. On the other hand, for the speed in the lower part of FIG. 6, the stepwise output is the output of the wheel tachometer, and such output is obtained because the pulse resolution with respect to the traveling distance is not sufficient. The system output speed smoothly traces this period, and it can be evaluated that a more accurate value is obtained.

FIG. 7 shows a situation when a broadcasting satellite is tracked by this system. The vertical axis represents the relative received power (dB), and the horizontal axis represents the angle formed by the downward axis of the moving object floor surface and the vertical downward axis. If the roll angle of the moving body is φ ₁ and the pitch angle is φ ₂ ,

[0064]

(Equation 21)

There is the following relationship. The vertical axis plots the change in the relative received power during running with the maximum power search value during stationary and normal reception at 0 dB. Relative received power is -1
If it is 0 dB or more, it means that the satellite can be directed with an accuracy of ± 5 °. The region where the angle formed with the vertical line is 5 ° or more is a region where reception is not possible at all with tracking only in one azimuth axis, but it can be seen that there are considerable data points and reception has been achieved with a considerable probability. . However, since the results of this tracking experiment include the blocking of radio waves by buildings (generally, shadowing), considering this effect, the actual tracking achievement is better than that shown here. Is assumed.

As a modified example of the present invention, there can be mentioned a system to which a magnetic compass is added, utilizing the fact that geomagnetism indicates magnetic north. In this case, in the initial work to direct the beam of the antenna in the direction of arrival of the radio wave at rest,
Since the azimuth can be known in advance by the magnetic compass, the antenna beam can be directed to the vicinity of the satellite at a stretch without checking the electric field strength, and the azimuth initialization of the moving body can be speeded up. Further, when the GPS cannot perform positioning for a long time for some reason, it can be used as auxiliary azimuth information.

Further, the satellite tracking apparatus of the present invention internally calculates various motion parameters (attitude angle, velocity, position, etc.) of the mobile object in order to track the satellite from the mobile object, and finally controls the tracking antenna system. The angle is obtained, but from a different point of view, it can be treated as a motion measuring device or position estimating device for a moving object that outputs the acceleration, angular velocity, speed, posture (including azimuth) and position of the moving object in real time. it can.

By incorporating the communication satellite tracking device for mobile communication of the present invention into a mobile, stable satellite communication can be performed using a high-gain antenna in a high frequency region of about the Ku band or higher. Although omnidirectional antennas have been used in lower frequency bands, radio power can be used effectively in higher frequency bands where antennas with small size and sharp beams can be manufactured. Therefore, only a small amount of power is required for radio wave transmission, which is suitable for transmission in a mobile body having a limited power supply. From the viewpoint of the communication satellite, the gain on the receiving side is improved, so that the transmission power can be reduced, and the satellite can be reduced in size and cost.

Also, unlike a ground station, a communication satellite has an extremely wide service area,
It is possible to provide information to a plurality of mobile stations in a wide range, or to obtain information from mobile stations. Fortunately, with the satellite tracking device of the present invention, the position and other motion parameters of the mobile body can be obtained in real time, so that the information obtained from the mobile body can be stored in the base station on the ground via the communication satellite. Conversely, it is also possible to give information from the ground base station to the mobile station via the satellite. This can reduce the cost compared to the conventional case where a relay station is installed on the ground, and since it does not have a ground relay station, it is considered to be effective for emergency communication in the event of a disaster.

When the method of the present invention is compared with the monopulse method, the present invention does not use any information on the electric field intensity during tracking, and thus clears all the weak points of closed loop tracking. Specifically, a complicated control algorithm for tracking is not required, and it is possible to quickly return to normal tracking after shadowing such as passing through a tunnel. In addition, the antenna itself requires only two control axes in the monopulse system. However, in the present invention, only one control axis is required. In addition to reducing the cost of the antenna unit by half, the load on the antenna mounted control unit is reduced. It is possible to reduce the size and cost.

On the other hand, when compared with a system using a gyrocompass or a magnetic compass instead of using the GPS, position information can be obtained at low cost. It has the feature of pointing in the direction. This is because when GPS is not used, the accuracy of the position information is remarkably reduced, and to compensate for this, an extremely accurate and expensive inertial sensor must be used. GP
When S is used, the inertial sensor used can be of low cost.

In the above description, an inclinometer (including one that performs an algebraic operation on the output of the three-axis acceleration sensor to derive a tilt value) is used as the attitude angle sensor in the low frequency range. Has described that a rate gyro is used, but the type of sensor is not limited to this, and if a sensor having desired performance is developed, it may be used. In addition, the frequency domain is not limited to being divided into two in the high and low areas, but may be divided into other appropriate integers according to the performance of the sensor to be used.

[0073]

As described above, according to the satellite tracking apparatus for mobile communication of the present invention, appropriate sensors for the low frequency region and the high frequency region are selected as means for detecting the motion information of the mobile object, respectively. The entire frequency band is assigned to these sensors, and the degree of dependence on these sensors is adjusted appropriately according to the moving state of the moving object. The beam direction can be directed to the satellite.

[Brief description of the drawings]

FIG. 1 illustrates a positional relationship between a satellite in outer space and a moving object on the ground.

FIG. 2 shows the relationship between rotation and a coordinate system in performing tracking.

FIG. 3 is a block diagram of a method for improving the accuracy of pitch attitude angle and speed by speed deviation feedback.

FIG. 4 is a configuration diagram of hardware that applies the present invention to a vehicle-mounted communication satellite tracking system.

FIG. 5 is a block diagram of software in which the present invention is applied to a vehicle-mounted communication satellite tracking system.

FIG. 6 shows a time course of a system output of a pitch angle and a speed during traveling of a moving object.

FIG. 7 is a diagram showing a distribution of a reception state according to an inclination angle and a relative reception power in a vehicle-mounted communication satellite tracking system to which the present invention is applied.

FIG. 8 shows the principle of a monopulse system, which is a typical example of closed-loop tracking.

FIG. 9 is a diagram showing synthesis of a beam pattern of a monopulse system.

[Explanation of symbols]

 41 arithmetic unit 411 GPS 412 rate gyro 413 acceleration sensor 414 wheel speedometer 415 plasma display 416 color liquid crystal display 42 antenna mechanism control unit 421 plane antenna 422 azimuth / elevation angle control circuit 423 azimuth angle servomotor 424 elevation angle servomotor 43 image unit 431 BS tuner 432 Television receiver 433 Spectrum analyzer 81 Main reflecting mirror 82 Secondary reflecting mirror 83a, 83b Feed horn

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsumi Sakai 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture Within the Opto-System Laboratory, Hitachi Cable, Ltd. (72) Inventor Junpei Miyazaki Hidaka-cho, Hitachi City, Ibaraki Prefecture 5-1-1, Hidaka Factory, Hitachi Cable, Ltd.

Claims (4)

[Claims] An apparatus for tracking a communication satellite for mobile communication, comprising a three-axis acceleration sensor, a three-axis angular velocity sensor, an inclinometer, a GPS device, a speedometer, and an antenna direction control device. And dividing the frequency domain into a plurality of sections, distributing the responsibilities of sensors or devices to each of them, and having control means for dynamically changing the responsibilities to optimal values according to the state of motion of the moving object. A communication satellite tracking device for mobile communication. 2. The frequency domain is divided into two parts, a charge of an inclinometer is allocated to a low frequency area, and 3
2. The communication satellite tracking device for mobile communication according to claim 1, wherein a charge of the shaft angular velocity sensor is allocated. 3. The tracking device for mobile communication satellite according to claim 2, wherein said inclinometer has means for performing an algebraic operation on the output of said three-axis acceleration sensor. 4. The communication satellite tracking device according to claim 2, wherein said three-axis angular velocity sensor is a rate gyro.