A zero position calibration method and system for vehicle-mounted satellite in-motion communication

Abstract

The present invention relates to a zero-position calibration method and system for vehicle-mounted satellite communication in motion. The method comprises: using the ground speed heading angle output by the satellite navigation device GNSS and the attitude angle output by the micro-inertial measurement unit MIMU to determine the zero-position calibration value of the azimuth angle; performing a pitch angle static scan during the satellite alignment process to determine the pitch angle of the position with the strongest signal; determining the zero-position error of the pitch angle according to the pitch angle of the position with the strongest signal; and determining the zero-position calibration value of the pitch angle according to the zero-position error of the pitch angle. The present invention improves the stability of the antenna beam pointing of the satellite communication in motion and improves the reliability of capturing satellites.

Description

Technical Field

[0001] The present invention relates to the technical field of mobile satellite communication, and in particular to a zero position calibration method and system for vehicle-mounted satellite mobile communication. Background Art

[0002] Satellite communication in motion technology is a broadband satellite mobile communication technology. It not only has the advantages of satellite communication, but also can realize rapid deployment and long-distance wireless multimedia communication. It has broad application prospects in both military and civilian fields. Satellite communication in motion, in simple terms, is a fixed satellite communication earth station installed on a mobile carrier (such as a car, train, airplane, ship, etc.). As we all know, the prerequisite for a fixed satellite station to establish a communication link with a synchronous orbit satellite is that the azimuth, pitch and polarization of the antenna beam are three-dimensionally aligned with the satellite. In the process, the fixed satellite earth station is placed on a carrier that is constantly moving. In this process, overcoming the change in the carrier's attitude angle and always keeping the antenna pointing to the target satellite becomes the primary task that the satellite communication in motion system needs to solve.

[0003] Satellite antennas are usually installed on azimuth and pitch mounts. In order to keep the direction aligned with the satellite at all times, corresponding attitude angle measurement equipment and motor drive devices are required. By measuring the attitude angle change of the carrier and calculating the compensation, the motor movement angle is obtained, so as to drive the motor to adjust the direction of the satellite antenna and keep the inertial space of the antenna beam stable. The acquisition of attitude angle is usually achieved by using a combined system of satellite navigation system / micro inertial measurement unit (GNSS / MIMU). MIMU has large error, but low cost, which is of great significance for reducing the cost of mobile communication. MIMU can be strapdown mounted on the carrier or installed on the antenna turntable. When installed on the antenna turntable, the azimuth gyro can play the role of inertial tachometer, which is extremely beneficial for stable pointing and reduces the dependence on gyro accuracy. However, there is a prominent problem in the low-precision GNSS / MIMU system, that is, the heading angle estimation accuracy is poor, the convergence is slow, and even when the vehicle maneuverability is not strong, the heading angle divergence will occur. An effective way to solve this problem is to use the ground speed course angle (course angle) output by GNSS in dynamic conditions to assist in the acquisition and correction of the course angle. However, the ground speed course angle obtained by GNSS is the angle between the vehicle's front and the geographic north direction. This angle needs to be converted to the MIMU coordinate system (i.e., the i system, such as Figure 2 As shown), the conversion angle is the azimuth zero position A 0 In addition, for the pitch motor, the control quantity is the absolute position of the pitch pointing angle, and the pitch angle command of the motor must be at the angle zero position β when the pitch angle is mechanically reset to zero. 0 Accurate pointing can only be achieved on the basis of accurate knowledge.

[0004] The traditional method is to use angle measurement equipment to measure the angle between the mechanical structure zero position of the azimuth and pitch angles after the antenna is reset and the front and horizontal plane of the carrier and the turntable, so as to achieve zero position calibration. This method has the following shortcomings: 1) Regardless of the azimuth or pitch angle, the angle measurement instrument cannot accurately measure the angle between the center of the antenna's radio wave beam and the front and horizontal of the vehicle, which is an approximate measurement. For example, for pitch zero position calibration, the inclination angle of the IMU and the inclination angle of the antenna surface are usually measured in turn, and then the two are subtracted to obtain the pitch zero position. This method is relatively rough and has large errors; for heading angle calibration, it is also necessary to roughly estimate the front baseline of the vehicle body, and the calibration accuracy cannot be guaranteed; 2) Since the installation position and installation deformation of each set of antennas may be different, each set of antennas requires measurement personnel to go to the roof, power on and reset, and then measure, which is extremely inconvenient for the calibration process.

[0005] In view of the shortcomings of the existing azimuth and elevation angle zero-position calibration technology, a fully autonomous zero-position calibration algorithm is urgently needed. Summary of the invention

[0006] The purpose of the present invention is to provide a zero-position calibration method and system for vehicle-mounted satellite communication in motion, so as to improve the stability of the antenna beam pointing of the satellite communication in motion and improve the reliability of capturing satellites.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A zero position calibration method for vehicle-mounted satellite communication in motion, comprising:

[0009] The zero position calibration value of the azimuth angle is determined by using the ground speed heading angle output by the satellite navigation device GNSS and the attitude angle output by the micro inertial measurement unit MIMU; the zero position of the azimuth angle is the angle between the heading angle of the vehicle body movement and the initial pointing direction of the antenna; the initial pointing direction of the antenna is the angle pointing of the mechanical zeroing after power-on reset;

[0010] During the satellite alignment process, perform a static pitch scan to determine the pitch angle at the location with the strongest signal;

[0011] Determine the zero position error of the pitch angle according to the pitch angle of the position where the signal is strongest;

[0012] The zero position calibration value of the pitch angle is determined according to the zero position error of the pitch angle.

[0013] Optionally, the method of determining the zero position calibration value of the azimuth angle by using the ground speed heading angle output by the satellite navigation device GNSS and the attitude angle output by the micro inertial measurement unit MIMU specifically includes:

[0014] In the static state of moving communication, the attitude angle output by the current MIMU and the ground speed heading angle output by the GNSS are determined according to the vehicle's linear motion state;

[0015] Using the formula Determine the attitude angle of the vehicle body;

[0016] Replace the heading angle in the attitude angle with the ground speed heading angle output by GNSS, and use the formula determining an estimate of an encoder error angle;

[0017] According to the estimated value of the encoder difference angle and the formula Update the attitude angle of the vehicle body;

[0018] Iterate the calculation n times until the set requirement is met. The estimated value of the encoder difference angle α at this time is n is the target value;

[0019] Determine the zero position of the azimuth according to the target value;

[0020] According to the zero position of the azimuth angle, the zero position calibration value of the azimuth angle is determined by using the sliding average method;

[0021] in, and are transformation matrices, φ,θ, are the attitude angles of the vehicle body, α, α 1 , α n are all estimated values ​​of the encoder difference angle, H, P, and R are all attitude angles output by the current MIMU, and H GNSS It is the ground speed heading angle output by GNSS.

[0022] Optionally, the step of determining the zero position calibration value of the azimuth angle by using a sliding average method according to the zero position of the azimuth angle specifically includes:

[0023] Using the formula Determine the zero calibration value of the azimuth;

[0024] in, is the zero position calibration value of the azimuth, A i The zero position calibration value for calculating the azimuth angle for the i-th time.

[0025] Optionally, determining the zero position error of the pitch angle according to the pitch angle of the position with the strongest signal specifically includes:

[0026] Using the formula Determine the zero error of the pitch angle;

[0027] Among them, Δβ is the zero position error of the elevation angle, E is the elevation angle of the satellite in the geographic system, and β maxis the pitch encoder angle value at the position with the strongest signal, P is the estimated value of the inertial navigation pitch angle deduced by the pitch angle maximum signal method, γ is the encoder angle of the polarization motor, V is the polarization angle of the satellite in the geographic coordinate system, and P a is the actual value of the inertial navigation pitch angle.

[0028] Optionally, determining the zero position calibration value of the pitch angle according to the zero position error of the pitch angle specifically includes:

[0029] Using the formula β 0 =β raw +Δβ determines the zero calibration value of the pitch angle;

[0030] Among them, β 0 is the zero calibration value of the pitch angle, β raw Design zero.

[0031] A zero position calibration system for vehicle-mounted satellite communication in motion, comprising:

[0032] The azimuth zero calibration value determination module is used to determine the azimuth zero calibration value using the ground speed heading angle output by the satellite navigation device GNSS and the attitude angle output by the micro inertial measurement unit MIMU; the azimuth zero is the angle between the vehicle body motion heading angle and the initial antenna pointing direction; the antenna initial pointing direction is the pointing angle after the power-on reset mechanical zeroing;

[0033] A module for determining the pitch angle of the position with the strongest signal, used for performing a pitch angle static scan during the satellite alignment process to determine the pitch angle of the position with the strongest signal;

[0034] A pitch angle zero error determination module, used to determine the pitch angle zero error according to the pitch angle at the position with the strongest signal;

[0035] The pitch angle zero calibration value determination module is used to determine the pitch angle zero calibration value according to the pitch angle zero error.

[0036] Optionally, the azimuth zero position calibration value determination module specifically includes:

[0037] The attitude angle output by MIMU and the ground speed heading angle output by GNSS are determined by the unit, which is used for satellite alignment in the moving and static conditions, and determines the attitude angle output by the current MIMU and the ground speed heading angle output by GNSS according to the state of the vehicle's linear motion;

[0038] The vehicle body attitude angle determination unit is used to use the formula Determine the attitude angle of the vehicle body;

[0039] The estimated value determination unit of the encoder difference angle is used to replace the heading angle in the attitude angle according to the ground speed heading angle output by the GNSS, using the formula determining an estimate of an encoder error angle;

[0040] The vehicle body attitude angle update unit is used to update the estimated value of the encoder difference angle and the formula Update the attitude angle of the vehicle body;

[0041] The iterative unit is used to iterate the calculation n times until the set requirement is met. The estimated value of the encoder difference angle at this time is the target value;

[0042] An azimuth zero position determination unit, used for determining the azimuth zero position according to a target value;

[0043] An azimuth zero position calibration value determination unit, used to determine the azimuth zero position calibration value by a sliding average method according to the azimuth zero position;

[0044] in, and are transformation matrices, φ,θ, are the attitude angles of the vehicle body, α, α 1 , α n are all estimated values ​​of the encoder difference angle, H, P, and R are all attitude angles output by the current MIMU, and H GNSS It is the ground speed heading angle output by GNSS.

[0045] Optionally, the azimuth zero position calibration value determination unit specifically includes:

[0046] The azimuth zero calibration value determination subunit is used to use the formula Determine the zero calibration value of the azimuth;

[0047] in, is the zero position calibration value of the azimuth, A i The zero position calibration value for calculating the azimuth angle for the i-th time.

[0048] Optionally, the pitch angle zero error determination module specifically includes:

[0049] The pitch angle zero error determination module determination unit is used to use the formula Determine the zero error of the pitch angle;

[0050] Among them, Δβ is the zero position error of the elevation angle, E is the elevation angle of the satellite in the geographic system, and β max is the pitch encoder angle value at the position with the strongest signal, P is the estimated value of the inertial navigation pitch angle deduced by the pitch angle maximum signal method, γ is the encoder angle of the polarization motor, V is the polarization angle of the satellite in the geographic coordinate system, and Pa is the actual value of the inertial navigation pitch angle.

[0051] Optionally, the pitch angle zero calibration value determination module specifically includes:

[0052] The zero calibration value determination unit of the pitch angle is used to use the formula β 0 =β raw +Δβ determines the zero calibration value of the pitch angle;

[0053] Among them, β 0 is the zero calibration value of the pitch angle, β raw Design zero.

[0054] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0055] The present invention provides a method and system for zero-position calibration of vehicle-mounted satellite communications in motion. The method adopted does not require special measurement personnel, measurement instruments, manual calculations and other steps; the calibration method adopted is based on the antenna radio wave beam, which is more scientific and accurate than the manual measurement method. The calibration method is the same for any installation vehicle and any use site, and no additional requirements are required for the installation position of the vehicle-mounted satellite communications in motion antenna. That is, the present invention has simple steps, reasonable design and easy implementation, and has important practical significance for the actual use of vehicle-mounted satellite communications in motion. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0057] Figure 1 A schematic flow chart of a zero position calibration method for vehicle-mounted satellite in-motion communication provided by the present invention;

[0058] Figure 2 It is a schematic diagram of the zero position of azimuth and pitch angle (when the vehicle is level);

[0059] Figure 3 This is a schematic diagram of azimuth zero position calculation (when the vehicle is level);

[0060] Figure 4 It is a schematic diagram of the angle relationship under the tilt condition;

[0061] Figure 5 It is a schematic diagram of the azimuth zero position calibration method;

[0062] Figure 6 It is a schematic diagram of the relationship between the pitch angle error and the zero position;

[0063] Figure 7 This is a schematic diagram of pitch angle precision alignment;

[0064] Figure 8 The present invention provides a schematic structural diagram of a zero-position calibration system for vehicle-mounted satellite communications in motion. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] The purpose of the present invention is to provide a zero-position calibration method and system for vehicle-mounted satellite communication in motion, so as to improve the stability of the antenna beam pointing of the satellite communication in motion and improve the reliability of capturing satellites.

[0067] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0068] The ground speed heading angle indicates the direction of movement of the vehicle. Figure 2 As shown, the vehicle body movement direction is OY b Direction (this direction is the direction of the ground speed heading angle), and the direction of the moving communication to the satellite is OY i Direction (this direction is the heading angle of MIMU). The three coordinate systems involved in the figure are i, b and n. i represents the coordinate system corresponding to MIMU, b represents the coordinate system corresponding to the vehicle body, and n represents the local geographic coordinate system (northeast sky coordinate system, x points to the east, y points to the north, and z points to the sky). The Y axes of the other two coordinate systems point to the front and the X axes point to the right, which conforms to the right-hand rule.

[0069] Assuming the vehicle is on an absolutely horizontal plane, the ground speed heading angle H measured by GNSS is GNSS , MIMU heading angle H IMU , the difference angle between the two is:

[0070] dH=H IMU -H GNSS ;

[0071] When the antenna is reset to zero, as a part of initialization, the azimuth encoder is reset to zero, and it is considered that this is the mechanical zero position of the azimuth angle. When the azimuth turntable rotates to the point where the front of the antenna beam is aligned with the front of the vehicle body, the encoder reading is the azimuth zero position M that needs to be calibrated. 0 The physical meaning of this zero position is very clear, that is, when the antenna azimuth turntable rotates to completely coincide with the vehicle body coordinate system (OY 0 Yu OY b If the attitude angle of MIMU is the same as the attitude angle of the vehicle body, and the two are completely consistent, it is possible to use the ground speed and heading angle of GNSS to assist MIMU.

[0072] Assume that when aiming at the target satellite, the encoder angle is M i , then this angle is the angle that the antenna moves from the mechanical zero position to the target satellite. Since the vehicle is horizontal, the heading angle difference and the encoder angle difference can be considered in the local geographic coordinate system, so the heading angle difference dH includes the encoder movement angle M i And the angle A between the encoder mechanical zero position and the front of the vehicle body 0 , so we have:

[0073] dH=M i +A 0 ;

[0074] Therefore, we can get:

[0075] A 0 =(H IMU -H GNSS )-M i ;

[0076] With the above relationship, we can get

[0077] H IMU =H GNSS +(A 0 +M i );

[0078] As shown in the formula, the calibration azimuth zero position A is obtained. 0 With this angle, the heading angle H required for the current integrated navigation can be calculated through the heading angle measured by GNSS. IMU , used to assist the initial alignment of integrated navigation and re-assignment in case of occlusion.

[0079] However, the above solution process is based on the condition that the vehicle is on a horizontal ground. If the vehicle is not traveling on a horizontal ground but on a slope, the above simple relationship no longer holds. Figure 4As shown in the figure, the vehicle is traveling on an inclined plane, which is characterized by the pitch angle P and the roll angle R. The angles reflected by the motor encoder are all on the inclined plane, while the ground speed heading angle measured by GNSS and the heading angle of MIMU are defined in the geographic system (need to be projected to the horizontal plane), so the simple relationship dH=M i +A 0 This is no longer true. The angle relationship of the motor encoder on the inclined plane must be converted to the geographic system before calculation can be performed.

[0080] Figure 1 The present invention provides a flow chart of a zero-position calibration method for vehicle-mounted satellite communications in motion. Figure 1 As shown, the present invention provides a zero position calibration method for vehicle-mounted satellite communication in motion, comprising:

[0081] S101, determining a zero-position calibration value of an azimuth angle using a ground speed heading angle output by a satellite navigation device GNSS and an attitude angle output by a micro inertial measurement unit MIMU; the zero position of the azimuth angle is the angle between the vehicle body motion heading angle and the initial antenna orientation; the initial antenna orientation is the orientation angle after mechanical zeroing after power-on reset;

[0082] S101 specifically includes:

[0083] Align the satellite in static state while in motion, and determine the attitude angle output by the current MIMU and the ground speed heading angle output by the GNSS;

[0084] Using the formula Determine the attitude angle of the vehicle body;

[0085] Replace the heading angle in the attitude angle with the ground speed heading angle output by GNSS, and use the formula determining an estimate of an encoder error angle;

[0086] According to the estimated value of the encoder difference angle and the formula Update the attitude angle of the vehicle body;

[0087] Iterate the calculation n times until the set requirement is met, and the estimated value of the encoder difference angle at this time is the target value;

[0088] Determine the zero position of the azimuth according to the target value;

[0089] According to the zero position of the azimuth angle, the zero position calibration value of the azimuth angle is determined by using the sliding average method;

[0090] in, and are transformation matrices, φ,θ, are the attitude angles of the vehicle body, α, α 1 , αn are all estimated values ​​of the encoder difference angle, H, P, and R are all attitude angles output by the current MIMU, and H GNSS It is the ground speed heading angle output by GNSS.

[0091] The zero position calibration value of the azimuth angle is determined by using a sliding average method according to the zero position of the azimuth angle.

[0092] Specifically include:

[0093] Using the formula Determine the zero calibration value of the azimuth;

[0094] in, is the zero position calibration value of the azimuth, A i The zero position calibration value for calculating the azimuth angle for the i-th time.

[0095] The specific calculation process is as follows:

[0096] In order to calibrate the zero position A of the azimuth angle 0 The physical meaning of the zero position is the azimuth encoder reading when the antenna beam is aligned with the front of the vehicle. Since the vehicle is not on the horizontal ground, the angles involved are transformed to the inclined plane for easy solution. The following coordinate system transformation relationship is considered:

[0097]

[0098] The angles H, P, and R are the attitude angles output by the inertial navigation system. The attitude angles will change as the azimuth turntable rotates. Represents the attitude angle of the vehicle body, where

[0099]

[0100] Represents the transformation matrix from the geographic coordinate system (n) to the inertial navigation coordinate system (i). The other two transformation matrices are and and The structure is the same, just need to replace the corresponding angle.

[0101] Through azimuth scanning, after the antenna is aligned with the satellite, the current heading angle H can be calculated through geometric relationships. At the same time, GNSS can obtain the vehicle's heading angle φ during the vehicle's motion, and the unknown number A can be solved through the formula 0 , define α=M i +A 0 , by expanding the formula, we have

[0102]

[0103] In the formula, cR represents cosR, and sR represents sinR. It is relatively complicated to solve α from the above equation, so an iterative solution method is proposed here. The calculation process is shown in Table 1 below:

[0104] Table 1

[0105]

[0106] The principle is: first assume that it is on a horizontal plane, at this time α=H-φ, θ=P, However, due to the inclination, that is, P and R are not 0, after rotating the inclined plane by an angle α, the pitch angle θ and roll angle calculated according to the coordinate system relationship are must change (for example, when α=0°, θ=P, When α=90°, θ=R, ). Since the vehicle body is not horizontal, α≠H-φ, and φ calculated by α=H-φ 1 ,θ 1 , There is also an error. In this case, the correct H obtained by GNSS is GNSS Replace the error φ 1 , we can infer α which is closer to the true value 1 After multiple recursions, we can finally get an estimate with high accuracy. The following is a specific example to illustrate the above calculation process and roughly determine the value of n.

[0107] Taking Asia Satellite 7 as an example, its alignment angle in Xi'an is: azimuth 186.1°, pitch 50.0°, polarization -5.0°. Assuming that after the successful alignment, the attitude angle of the inertial navigation is H = 190.0°, P = 20.0°, R = -5.0°, and the ground speed heading angle given by GNSS is H GNSS =65.5°, as shown in Table 2, the calibration value is calculated as follows:

[0108] Table 2

[0109]

[0110] From the above table, we can find that the initial angle α 0 =H-φ 0 =124.5°, the only attitude angle of the carrier can be obtained through GNSS, while the pitch angle and roll angle are unknown, assumed to be 0, and then iterative calculation, after 3 iterations, the accuracy has reached 0.01°, it can be considered that the number of iterative calculations n = 3 can meet the accuracy. The above example shows that according to the assumption that the carrier is horizontal, dH = 124.5° is obtained, and the actual calculated encoder difference angle should be Mi +A 0 =127.24°, obviously the two are not equal, the difference is as much as 2.75°, so the overall orientation zero is A 0 The calibration process should take the vehicle's tilt into full consideration. In summary, the calibration method for the azimuth zero position should be modified to first obtain the encoder difference angle α through the above iterative algorithm, and then subtract the current reading M of the azimuth encoder. i , that is, A 0 =α-M i .

[0111] The specific calibration method also needs to consider the effectiveness of GNSS. Therefore, the calibration method also requires that the vehicle can have an effective straight driving, and the measurement error of GNSS data must be fully considered. Therefore, in addition to the above specific algorithms, the vehicle movement and data errors must be simply processed. Therefore, the calibration method of the azimuth zero position is summarized as follows: Figure 5 As shown:

[0112] 1) Align the satellite in the static state and obtain the attitude angles H, P, and R of the MIMU at this time;

[0113] 2) In order to use the ground speed and heading angle measured by GNSS, try to choose an open road, and the vehicle should drive in a straight line for more than 1 minute at a speed of more than 5m / s. When it is determined that the ground speed and heading angle have been effectively output for more than 10s, smoothing filtering will begin. The filter is a simple second-order Butterworth filter (the filter cutoff frequency can be set to 0.5Hz), and timing will begin;

[0114] 3) After 5 seconds, the filter is basically stable, and the heading angle after filtering is brought into the aforementioned iterative algorithm 1 (as shown in Table 1) to calculate the azimuth zero position estimate A 0 , the number of iterations per time is set to n = 3;

[0115] 4) The time is set again for 30 seconds. During this process, the sliding average method is used to further improve the final calibration accuracy, that is, assuming that the calibration value obtained by the i-th calculation is recorded as A i , then the estimated value of the calibration value is expressed as After the timing is completed, the final calibration value Write to Flash and end the calibration process.

[0116] The above calibration process can obtain a relatively high-precision azimuth zero position calibration value, and fully considers the conditions of the vehicle body on various road surfaces and measurement errors.

[0117] S102, performing a pitch angle static scan during the satellite alignment process to determine the pitch angle of the position with the strongest signal;

[0118] When the vehicle is static, the current inertial navigation pitch angle can be calculated through the gravity vector measurement of the accelerometer. After the antenna is aligned with the target satellite, the current inertial navigation pitch angle can also be inferred from the pitch encoder angle at this time. If there is an error in the pitch angle zero position, the inferred pitch angle is inconsistent with the actual pitch angle measured by the accelerometer, and the calibration can be completed through the relationship between the two.

[0119] When the carrier is stationary, the accelerometer can calculate the pitch angle of the turntable through the gravity measurement value.

[0120]

[0121] a in the above formula y is the measurement value of the y-axis accelerometer among the three orthogonally placed accelerometers inside the MIMU, and g is the value of gravity acceleration. Let's see how to infer the current MIMU pitch angle by aligning with the satellite.

[0122] The first step to aligning the satellite is to search for the satellite. At the beginning of the initial satellite search, the pitch angle and polarization angle of the antenna are adjusted to the correct position according to the pitch angle and roll angle values ​​given by the inertial navigation, and then the azimuth rotation scanning search is performed to find the target satellite through the satellite signal. After aligning the satellite, if there is no error in the pitch angle, the satellite signal is at its maximum value, which means that the satellite is aligned. If there is an error in the pitch angle zero position, the pitch angle motor command angle at this time does not match the actual spatial pointing angle of the antenna, which will cause the absolute pointing deviation of the motor in space, and the satellite signal may not be searched. Figure 6 As shown, for example, the design β raw = 2.0°, and the actual zero position is β 0 =3.5°, then when the calculated pitch angle command β=50.5°, when the motor moves to the encoder indication of 50.5°, it cannot align with the satellite, but should be adjusted to β max =52°. Through the above example, it is easy to find that the angle adjusted by the motor is based on the zero angle. Once the reference is wrong, the final command angle will also have a corresponding error. If the difference is too large, the pitch angle may deviate from the satellite beam and fail to find the satellite.

[0123] Therefore, the pitch angle needs to be adjusted dynamically during the satellite search process. The specific method is: after rotating the azimuth angle for one week, if the satellite cannot be locked according to the satellite beacon receiver signal, the standard for locking the satellite is that the received satellite signal strength is greater than the satellite capture threshold X T (This threshold is usually selected based on experience according to the characteristics of the beacon receiver), then adjust the pitch angle to β+(-1) n2n (n is the number of rotations. Considering that commonly used satellite communications in motion are all small-aperture antennas, the elevation beam width is generally 3° to 5°, and each adjustment step is selected as 2° here), continue to rotate the azimuth to search for stars until the target satellite is aligned.

[0124] The above is a large-scale scan of the elevation angle during the satellite alignment process, which can overcome the problem that the azimuth rotation search cannot find the satellite signal due to the zero position error. If accurate satellite pointing is required, accurate scanning of the elevation angle is also required. Figure 6 As shown, based on the current pitch angle, the pitch motor is driven to scan up and down, and the upper and lower angles β of the arrival signal strength Ee are recorded. e1 , β e2 , then the pitch angle corresponding to the maximum signal value is The above method can achieve precise alignment of pitch.

[0125] At this time, the antenna is precisely aimed at the satellite, and the relationship between the angles can be obtained through the coordinate system transformation relationship:

[0126]

[0127] Here, s represents the antenna beam coordinate system, and the angles β and γ represent the transformation angles from the turntable coordinate system where the inertial navigation is installed to the antenna beam coordinate system. In fact, they are the angles that the drive motor of the moving antenna needs to be adjusted. Note that the azimuth angle here is 0, which does not mean that the encoder angle is 0, but because the inertial navigation is installed on the antenna turntable (such as Figure 2 , 3 As shown in the figure, there is no azimuth difference between the inertial navigation coordinate system i and the beam coordinate system s, only the pitch angle and polarization angle. It represents the transformation matrix from the geographic coordinate system to the antenna beam coordinate system. The three angles, azimuth angle A, elevation angle E, and polarization angle V, can be obtained through the relationship between the current geographic location and the geographic location of the target satellite. These three angles are actually the three angles of the satellite antenna fixed on the ground to the star. The physical meaning of the formula is to first use the matrix from the geographic system Transform to inertial navigation system i, and then use the inertial navigation system i Transform to beam coordinate system s, and directly use from geographic system i The transformation to the beam system s is equivalent, and this equation shows the basic principle of communication in motion.

[0128] Transform the formula to get

[0129] After expansion:

[0130]

[0131] Considering only the items in the second row and third column that contain sinP, we obtain:

[0132] sP=-sγ·sβ max ·sV·cE+cβ max ·sE-cγ·sβ max ·cV·cE

[0133] Furthermore, sinP = sinEcosβ max -cosEsinβ max cos(γ-V);

[0134] If γ-V=0, then obviously sinP=sin(E-β max ), that is, P = E-β max This is the direct conversion relationship when the vehicle is horizontal, that is, the pitch angle of the inertial navigation is equal to the geographic pitch angle minus the current pitch encoder angle. max Calculate the estimated value of the inertial navigation pitch angle P.

[0135] S103, determining a zero position error of the pitch angle according to the pitch angle of the position where the signal is strongest;

[0136] S103 specifically includes:

[0137] Using the formula Determine the zero error of the pitch angle;

[0138] Among them, Δβ is the zero position error of the elevation angle, E is the elevation angle of the satellite in the geographic system, and β max is the pitch encoder angle value at the position with the strongest signal, P is the estimated value of the inertial navigation pitch angle deduced by the pitch angle maximum signal method, γ is the encoder angle of the polarization motor, V is the polarization angle of the satellite in the geographic system, and P a is the actual value of the inertial navigation pitch angle.

[0139] The specific derivation process of S103 is as follows:

[0140] Δβ=β max -β=β 0 -β raw , so:

[0141] β 0 =β raw +Δβ=β raw +(β max -β);

[0142] According to the real inertial navigation pitch angle P a And design zero β rawThe calculated elevation angle is β, and the pitch angle corrected according to the maximum signal is β max , the inverse inertial navigation pitch angle is P, and the above relationship can be written as:

[0143]

[0144] Subtracting the above two equations, we get:

[0145] sinP a -sinP=sinE(cosβ max -cosβ)-cosEcos(γ-V)(sinβ max -sinβ);

[0146] Considering that the difference between the designed zero position and the actual zero position is usually less than 5°, using the small angle approximation, the formula is further:

[0147] (cosP)(P a -P)=-sinE·sinβ max ·Δβ-cosE·cosβ max cos(γ-V)·Δβ;

[0148] Therefore, the final pitch angle zero error is:

[0149]

[0150] Still considering the special case of the formula, that is, γ-V = 0, P = E-β max , then it becomes Δβ=(P a -P), which is obviously in line with intuitive understanding.

[0151] S104, determining a zero position calibration value of the pitch angle according to the zero position error of the pitch angle.

[0152] Determining the zero position calibration value of the pitch angle according to the zero position error of the pitch angle in S104 specifically includes:

[0153] Using the formula β 0 =β raw +Δβ determines the zero calibration value of the pitch angle;

[0154] Among them, β 0 is the zero calibration value of the pitch angle, β raw Design zero.

[0155] Figure 8 The present invention provides a schematic diagram of the zero-position calibration system for vehicle-mounted satellite communications in motion. Figure 8 As shown, the present invention provides a zero position calibration system for vehicle-mounted satellite communication in motion, comprising:

[0156] The azimuth zero calibration value determination module 801 is used to determine the azimuth zero calibration value using the ground speed heading angle output by the satellite navigation device GNSS and the attitude angle output by the micro inertial measurement unit MIMU; the azimuth zero is the angle between the vehicle body motion heading angle and the antenna initial pointing direction; the antenna initial pointing direction is the pointing angle after the power-on reset mechanical zeroing;

[0157] The pitch angle determination module 802 of the position with the strongest signal is used to perform pitch angle static scanning during the satellite alignment process to determine the pitch angle of the position with the strongest signal;

[0158] A pitch angle zero error determination module 803, used to determine the pitch angle zero error according to the pitch angle of the position with the strongest signal;

[0159] The pitch angle zero calibration value determination module 804 is used to determine the pitch angle zero calibration value according to the pitch angle zero error.

[0160] The azimuth zero calibration value determination module 801 specifically includes:

[0161] The attitude angle output by MIMU and the ground speed heading angle output by GNSS are determined by the unit, which is used to determine the attitude angle output by the current MIMU and the ground speed heading angle output by GNSS in the case of static satellite alignment in motion;

[0162] The vehicle body attitude angle determination unit is used to use the formula Determine the attitude angle of the vehicle body;

[0163] The estimated value determination unit of the encoder difference angle is used to replace the heading angle in the attitude angle according to the ground speed heading angle output by the GNSS, using the formula determining an estimate of an encoder error angle;

[0164] The vehicle body attitude angle update unit is used to update the estimated value of the encoder difference angle and the formula Update the attitude angle of the vehicle body;

[0165] The iterative unit is used to iterate the calculation n times until the set requirement is met. The estimated value of the encoder difference angle at this time is the target value;

[0166] An azimuth zero position determination unit, used for determining the azimuth zero position according to a target value;

[0167] An azimuth zero position calibration value determination unit, used to determine the azimuth zero position calibration value by a sliding average method according to the azimuth zero position;

[0168] in, and are transformation matrices, φ,θ, are the attitude angles of the vehicle body, α, α 1 , α n are all estimated values ​​of the encoder difference angle, H, P, and R are all attitude angles output by the current MIMU, and H GNSS It is the ground speed heading angle output by GNSS.

[0169] The azimuth zero calibration value determination unit specifically includes:

[0170] The azimuth zero calibration value determination subunit is used to use the formula Determine the zero calibration value of the azimuth;

[0171] in, is the zero position calibration value of the azimuth, A i The zero position calibration value for calculating the azimuth angle for the i-th time.

[0172] The pitch angle zero error determination module 803 specifically includes:

[0173] The pitch angle zero error determination module determination unit is used to use the formula Determine the zero error of the pitch angle;

[0174] Among them, Δβ is the zero position error of the elevation angle, E is the elevation angle of the satellite in the geographic system, and β max is the pitch encoder angle value at the position with the strongest signal, P is the estimated value of the inertial navigation pitch angle deduced by the pitch angle maximum signal method, γ is the encoder angle of the polarization motor, V is the polarization angle of the satellite in the geographic system, and P a is the actual value of the inertial navigation pitch angle.

[0175] The pitch angle zero calibration value determination module 804 specifically includes:

[0176] The zero calibration value determination unit of the pitch angle is used to use the formula β 0 =β raw +Δβ determines the zero calibration value of the pitch angle;

[0177] Among them, β 0 is the zero calibration value of the pitch angle, β raw Design zero.

[0178] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0179] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A zero position calibration method for vehicle-mounted satellite in-motion communication, characterized in that: include: The zero position calibration value of the azimuth angle is determined by using the ground speed heading angle output by the satellite navigation device GNSS and the attitude angle output by the micro inertial measurement unit MIMU; The zero position of the azimuth angle is the angle between the vehicle body motion heading angle and the initial antenna orientation; the initial antenna orientation is the orientation angle after the power-on reset mechanical zeroing; During the satellite alignment process, perform a static pitch scan to determine the pitch angle at the location with the strongest signal; Determine the zero position error of the pitch angle according to the pitch angle of the position where the signal is strongest; Determine the zero position calibration value of the pitch angle according to the zero position error of the pitch angle; The method of determining the zero position calibration value of the azimuth angle by using the ground speed heading angle output by the satellite navigation device GNSS and the attitude angle output by the micro inertial measurement unit MIMU specifically includes: In the static state of moving communication, determine the attitude angle output by the current MIMU and the ground speed heading angle output by the GNSS; Using the formula Determine the attitude angle of the vehicle body; Replace the heading angle in the attitude angle with the ground speed heading angle output by GNSS, and use the formula determining an estimate of an encoder error angle; According to the estimated value of the encoder difference angle and the formula Update the attitude angle of the vehicle body; Iterate the calculation n times until the set requirement is met, and the estimated value of the encoder difference angle at this time is the target value; Determine the zero position of the azimuth according to the target value; According to the zero position of the azimuth angle, the zero position calibration value of the azimuth angle is determined by using the sliding average method; in, and are transformation matrices, are the attitude angles of the vehicle body, α, α1, α n are all estimated values ​​of the encoder difference angle, H, P, and R are all attitude angles output by the current MIMU, and H GNSS It is the ground speed heading angle output by GNSS; Determining the zero position error of the pitch angle according to the pitch angle of the position with the strongest signal specifically includes: Using the formula Determine the zero error of the pitch angle; Among them, Δβ is the zero position error of the elevation angle, E is the elevation angle of the satellite in the geographic system, and β max is the pitch encoder angle value at the position with the strongest signal, P is the estimated value of the inertial navigation pitch angle deduced by the pitch angle maximum signal method, γ is the encoder angle of the polarization motor, V is the polarization angle of the satellite in the geographic system, and P a is the actual value of the inertial navigation pitch angle; Determining the zero position calibration value of the pitch angle according to the zero position error of the pitch angle specifically includes: Using the formula β0=β raw +Δβ determines the zero calibration value of the pitch angle; Among them, β0 is the zero calibration value of the pitch angle, β raw Design zero.

2. A zero position calibration method for vehicle-mounted satellite communication in motion according to claim 1, characterized in that: The method of determining the zero position calibration value of the azimuth angle by using a sliding average method according to the zero position of the azimuth angle specifically includes: Using the formula Determine the zero calibration value of the azimuth; in, is the zero position calibration value of the azimuth, A i The zero position calibration value for calculating the azimuth angle for the i-th time.

3. A zero position calibration system for vehicle-mounted satellite in-motion communication, characterized in that: include: The azimuth zero calibration value determination module is used to determine the azimuth zero calibration value using the ground speed heading angle output by the satellite navigation device GNSS and the attitude angle output by the micro inertial measurement unit MIMU; the azimuth zero is the angle between the vehicle body motion heading angle and the initial antenna pointing direction; the antenna initial pointing direction is the pointing angle after the power-on reset mechanical zeroing; A module for determining the pitch angle of the position with the strongest signal, used for performing a pitch angle static scan during the satellite alignment process to determine the pitch angle of the position with the strongest signal; A pitch angle zero error determination module, used to determine the pitch angle zero error according to the pitch angle at the position with the strongest signal; A pitch angle zero calibration value determination module, used to determine the pitch angle zero calibration value according to the pitch angle zero error; The azimuth zero calibration value determination module specifically includes: The attitude angle output by MIMU and the ground speed heading angle output by GNSS are determined by the unit, which is used to determine the attitude angle output by the current MIMU and the ground speed heading angle output by GNSS in the case of static satellite alignment in motion; The vehicle body attitude angle determination unit is used to use the formula Determine the attitude angle of the vehicle body; The estimated value determination unit of the encoder difference angle is used to replace the heading angle in the attitude angle according to the ground speed heading angle output by the GNSS, using the formula determining an estimate of an encoder error angle; The vehicle body attitude angle update unit is used to update the estimated value of the encoder difference angle and the formula Update the attitude angle of the vehicle body; The iterative unit is used to iterate the calculation n times until the set requirement is met. The estimated value of the encoder difference angle at this time is the target value; An azimuth zero position determination unit, used for determining the azimuth zero position according to a target value; An azimuth zero position calibration value determination unit, used to determine the azimuth zero position calibration value by a sliding average method according to the azimuth zero position; in, and are transformation matrices, are the attitude angles of the vehicle body, α, α1, α n are all estimated values ​​of the encoder difference angle, H, P, and R are all attitude angles output by the current MIMU, and H GNSS It is the ground speed heading angle output by GNSS; The pitch angle zero error determination module specifically includes: The pitch angle zero error determination module determination unit is used to use the formula Determine the zero error of the pitch angle; Among them, Δβ is the zero position error of the elevation angle, E is the elevation angle of the satellite in the geographic system, and β max is the pitch encoder angle value at the position with the strongest signal, P is the estimated value of the inertial navigation pitch angle deduced by the pitch angle maximum signal method, γ is the encoder angle of the polarization motor, V is the polarization angle of the satellite in the geographic system, and P a is the actual value of the inertial navigation pitch angle; The pitch angle zero calibration value determination module specifically includes: The pitch angle zero calibration value determination unit is used to use the formula β0=β raw +Δβ determines the zero calibration value of the pitch angle; Among them, β0 is the zero calibration value of the pitch angle, β raw Design zero.

4. A zero position calibration system for vehicle-mounted satellite communication in motion according to claim 3, characterized in that: The azimuth zero calibration value determination unit specifically includes: The azimuth zero calibration value determination subunit is used to use the formula Determine the zero calibration value of the azimuth; in, is the zero position calibration value of the azimuth, A i The zero position calibration value for calculating the azimuth angle for the i-th time.

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