An azimuth-cross-pitch system adapted to very high sea states

Abstract

The application discloses an azimuth-cross-pitch type pedestal system suitable for extremely high sea conditions and belongs to the field of satellite communication antennas. The system comprises an azimuth-cross-pitch type pedestal, motors for driving rotation of the shafts, a driver for controlling the rotation of the motors, encoders for collecting azimuth, cross and pitch shaft angle information, and a controller for receiving driver information, encoder information and navigation information. After the encoders collect the shaft angle code information, the information is reported to the driver. The driver analyzes the received code information and reports the information to the controller in the form of CAN messages as the feedback of the shafts. The controller controls the driver to realize stable satellite tracking of the antenna. The application has high structural strength, a large cross shaft movement range, low cost and can realize stable satellite tracking under extremely high sea conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of satellite communication antenna, in particular to a shipborne three-axis satellite communication antenna capable of stable tracking of satellite in extremely high sea conditions. BACKGROUND

[0002] When a small ship sails in the open sea, the ship shaking condition thereof is much worse than that of a large ship. In order to ensure the stable connection of a communication link, a satellite communication antenna installed thereon needs to overcome the influence of large swing amplitude and short swing period ship shaking interference when working. With the need of China for small ship sailing in the open sea, the research on stable tracking of satellite in extremely high sea conditions is imperative.

[0003] In the normal working process of a shipborne synchronous satellite communication antenna, the antenna beam needs to be pointed to the target satellite in real time to ensure the reliable connection of the communication link. First, the antenna system needs to calculate the theoretical pointing geographic angle of the target satellite according to the current geographic position of the ship and the longitude of the target satellite. Second, the target deck angle of the current pedestal form antenna is calculated according to the heading, roll and pitch data of the ship itself, so as to drive the antenna to accurately point to the target satellite. The most critical thing is the selection of the antenna pedestal form. An inappropriate pedestal form will affect the working efficiency of the antenna, so as to fail to meet the normal use requirements. The most commonly used pedestal forms are two-axis and three-axis pedestal forms. The two-axis pedestal form is mainly azimuth-elevation type pedestal form, and the three-axis pedestal form is mainly azimuth-elevation-cross type pedestal form. However, the two types of pedestal forms cannot meet the application requirements in extremely high sea conditions.

[0004] Specifically, the existing azimuth-elevation type pedestal form has the following disadvantages:

[0005] The azimuth-elevation type pedestal form has the problem of over-the-top tracking failure. When the ship approaches the equator during sailing, the communication link will be interrupted due to the failure of the azimuth axis to quickly track when the target satellite is at a high elevation angle or over the top.

[0006] The existing azimuth-elevation-cross type pedestal form has the following disadvantages:

[0007] 1) It is difficult to make the cross-axis movement range large. Due to the small tonnage of the ship, the poor sea conditions in the working sea area and other reasons, the ship will be subjected to large amplitude ship shaking when sailing in the working sea area. The cross-axis needs to have a large movement range at a high elevation angle to isolate the ship body shaking and ensure accurate pointing, which will lead to complex structure design and reduced reliability.

[0008] 2) The seat frame structure has low strength and low structural resonance frequency. In the application, the tonnage of the ship is small, and the sea conditions in the working sea area of the ship are poor. Therefore, when the ship sails in the working sea area, the swing period of the ship will be significantly shortened. Therefore, the servo bandwidth of the antenna needs to be high. Otherwise, it cannot respond quickly. However, the structural resonance frequency directly determines that the servo bandwidth of the seat frame antenna cannot be high enough. Therefore, the antenna has a fatal defect and cannot guarantee uninterrupted communication. SUMMARY

[0009] The purpose of the present application is to avoid the shortcomings of the conventional seat frame form and provide an azimuth-cross-elevation type seat frame system suitable for extremely high sea conditions. The system can realize stable satellite tracking in extremely high sea conditions and has the characteristics of simple structure design and high reliability.

[0010] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0011] An azimuth-cross-elevation type seat frame system suitable for extremely high sea conditions, comprising an azimuth-cross-elevation type seat frame, a motor for driving the rotation of each axis, a driver for controlling the rotation of the motor, an encoder for collecting the axis angle information of the azimuth, cross and elevation axes, and a controller for receiving the driver information, encoder information and navigation information; the encoder collects the axis angle code information of each axis and reports it to the driver. The driver analyzes the received code information and reports it to the controller in the form of CAN message as the feedback of each axis. The working mode of the controller is as follows:

[0012] The controller receives the navigation information reported by the navigation system, including the longitude and latitude information of the ship, the roll and pitch information, and the heading information;

[0013] When the controller receives the tracking instruction from the station monitoring, the controller takes the target star information and the ship's latitude and longitude information as input and calculates the theoretical geographic angle of the current target star:

[0014]

[0015]

[0016] In the formula,

[0017] A: Theoretical azimuth angle of the target star;

[0018] E: Theoretical elevation angle of the target star;

[0019] Latitude of the ship;

[0020] λ: Longitude of the target star;

[0021] λ s : Longitude of the ship;

[0022] R e Earth's radius;

[0023] h: Altitude of the target satellite above the ground;

[0024] Based on the ship's current heading, roll, and pitch information, the controller uses optimized inverse kinematics equations to calculate the target deck angle pointing towards the target star.

[0025] The controller takes the target deck angle information as input and the shaft angle information reported by the driver as feedback, and calculates the control quantity that meets the design requirements according to the control law.

[0026] The controller sends the control quantity to the driver, which drives the corresponding motor to rotate into position, thereby pointing the antenna towards the target star.

[0027] Furthermore, the encoder is an incremental photoelectric encoder with 500 lines and a total code count of 2000.

[0028] Furthermore, the azimuth axis and cross axis of the azimuth-cross-pitch type mount are orthogonal.

[0029] Furthermore, the azimuth axis of the azimuth-cross-pitch type mount adopts a slip ring structure to ensure the continuity of azimuth axis rotation.

[0030] Furthermore, the optimized inverse kinematic equations are:

[0031]

[0032]

[0033] if but

[0034]

[0035] In the formula,

[0036] A g The azimuth angle at which the antenna points to the target;

[0037] E g The elevation angle of the antenna pointing towards the target;

[0038] k: The ship's heading given by the inertial navigation system guided by the antenna;

[0039] p: The pitch angle of the hull given by the antenna-guided inertial navigation system;

[0040] r: The hull roll angle given by the antenna-guided inertial navigation system;

[0041] A j: The azimuth deck angle in the inertial navigation deck coordinate system, with the antenna pointing towards the bow at zero, and the top-view clockwise angle increasing;

[0042] E j : The elevation angle of the deck in the inertial navigation deck coordinate system is zero when the antenna points to the deck plane and 90° when it points to the mast;

[0043] C j The cross deck angle in the inertial navigation deck coordinate system is zero for azimuth and 90° for pitch. The antenna pointing towards the mast is zero, and deflection to starboard is positive.

[0044] The present invention has the following advantages over the prior art:

[0045] 1. The present invention adopts a three-axis mount form of azimuth-cross-pitch, which can effectively overcome the problems of high elevation angle and over-the-top tracking, ensure that the communication link will not be interrupted due to pointing lag, and improve the reliability of the normal operation of the communication system.

[0046] 2. This invention adopts a three-axis mount design with azimuth-cross-pitch. The cross axis has a large range of motion, which can easily meet the system requirements, greatly reducing the requirements for structural design, improving the system's reliability, and reducing costs.

[0047] 3. This invention adopts a three-axis mount design with azimuth-cross-elevation, which has high structural strength and high structural resonant frequency, thus ensuring that the servo bandwidth can be very high, which is sufficient to meet the short-period swing requirements and thus ensure that the antenna communication is uninterrupted. Attached Figure Description

[0048] Figure 1 This is a block diagram illustrating the principle of the antenna control system in an embodiment of the present invention.

[0049] Figure 2 This is a mechanical structure diagram of the orientation-cross-tilt type mount system in an embodiment of the present invention. Detailed Implementation

[0050] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0051] like Figure 1 and 2 As shown, an azimuth-cross-pitch mount system adapted to extremely high sea states includes an azimuth-cross-pitch mount, on which are mounted motors that drive the rotation of each axis, drivers that control the rotation of the motors, encoders that collect azimuth, cross, and pitch axis angle information, and a controller that receives driver information, encoder information, and navigation information. After collecting the axis angle encoding information of each axis, the encoders report it to the drivers. The drivers parse and process the received encoding information and report it to the controller in the form of CAN messages as feedback for each axis. The controller operates as follows:

[0052] The controller receives navigation information reported by the navigation system, including the ship's longitude and latitude, roll, pitch and heading information;

[0053] When the controller receives a tracking command from the station monitoring, it uses the target satellite information and the ship's latitude and longitude information as inputs to calculate the theoretical geographic angle of the current target satellite:

[0054]

[0055]

[0056] In the formula,

[0057] A: Theoretical azimuth angle of the target star;

[0058] E: Theoretical elevation angle of the target satellite;

[0059] Ship latitude;

[0060] λ: Longitude of the target star;

[0061] λ s : Warship longitude;

[0062] R e Earth's radius;

[0063] h: Altitude of the target satellite above the ground;

[0064] Based on the ship's current heading, roll, and pitch information, the controller uses optimized inverse kinematics equations to calculate the target deck angle pointing towards the target star.

[0065] The controller takes the target deck angle information as input and the shaft angle information reported by the driver as feedback, and calculates the control quantity that meets the design requirements according to the control law.

[0066] The controller sends the control quantity to the driver, which drives the corresponding motor to rotate into position, thereby pointing the antenna towards the target star.

[0067] The system design process begins with determining the ship's operating elevation angle range based on its operational sea area and communication satellite information. Next, the system's extreme rolling conditions during navigation are determined based on its dimensions, displacement, and sea conditions. Then, forward and inverse kinematic algorithms are developed for the antenna configuration. Simulations are then performed to determine the minimum required range of motion, minimum velocity, and minimum acceleration for each axis. Finally, the kinematic algorithms are optimized to ensure the system's physical feasibility. The specific steps are as follows:

[0068] ① Determine the working elevation angle

[0069] Based on the ship's operating sea area information and target satellite information, the antenna's operating elevation angle range can be calculated using the following formula. The operating sea area information includes the longitude and latitude of the ship's operating sea area; the target satellite information includes satellite longitude and other information. The formula for calculating the operating elevation angle is:

[0070]

[0071] in,

[0072] E: Antenna operating elevation angle;

[0073] The latitude of the sea area where the ship operates;

[0074] λ: Longitude of the target satellite;

[0075] λ s Longitude of the sea area where the ship operates;

[0076] R e Earth's radius;

[0077] h: The altitude of the target satellite above the ground.

[0078] ② Determine the swing conditions

[0079] Based on information such as the ship's external dimensions, tonnage, and sea conditions in the operating area, simulation software can be used to determine the maximum rolling conditions that the ship may experience during its navigation in its operating area, including information such as roll amplitude, roll period, pitch amplitude, and pitch period.

[0080] ③ Develop kinematic formulas

[0081] The system employs a novel frame design, namely an azimuth-cross-pitch frame, with the azimuth and cross axes orthogonal. The forward and inverse kinematic equations for this frame are developed as follows:

[0082] Forward kinematic equations:

[0083]

[0084]

[0085] Inverse kinematic equations:

[0086]

[0087]

[0088] if but

[0089]

[0090] in,

[0091] A g The azimuth angle at which the antenna points to the target;

[0092] E g The elevation angle of the antenna pointing towards the target;

[0093] k: The ship's heading given by the inertial navigation system guided by the antenna;

[0094] p: The pitch angle of the hull given by the antenna-guided inertial navigation system;

[0095] r: The hull roll angle given by the antenna-guided inertial navigation system;

[0096] A j : The azimuth deck angle in the inertial navigation deck coordinate system, with the antenna pointing towards the bow at zero, and the top-view clockwise angle increasing;

[0097] E j : The elevation angle of the deck in the inertial navigation deck coordinate system is zero when the antenna points to the deck plane and 90° when it points to the mast;

[0098] C j The cross deck angle in the inertial navigation deck coordinate system is zero for azimuth and 90° for pitch. The antenna pointing towards the mast is zero, and deflection to starboard is positive.

[0099] ④ Simulation calculation

[0100] Leveraging MATLAB's powerful computational capabilities, using the results from ① and ② as input and the kinematic formulas from ③ as the medium, the motion range, velocity, and acceleration requirements of each axis were calculated and used as the basis for structural design and equipment selection. The simulation results are summarized in Table 1 below:

[0101] Table 1 Simulation Results

[0102]

[0103] ⑤ Algorithm optimization

[0104] As can be seen from Table 1, when the antenna operating elevation angle is 10° and 30°, the speed and acceleration required for the cross axis are very large, making such a system impossible to implement.

[0105] The roll angle, projected onto the azimuth dial, is used to proportionally distribute the azimuth and cross axes in real time to the antenna pointing, according to the change in elevation angle. This allows the azimuth and cross axes to be combined to isolate roll pointing disturbances. Specifically, the azimuth axis isolates heading disturbances, while the cross axis isolates some or all roll disturbances based on its operating elevation angle range. Furthermore, the pitch and cross axes isolate the remaining roll and pitch disturbances to the pointing. Because the azimuth axis shares some of the cross axis's functionality, the cross axis performance requirements are reduced at low elevation angles. The simulation results of the optimized algorithm are shown in Table 2 below.

[0106] Table 2 Simulation results after optimization

[0107]

[0108] In summary, this invention addresses the shortcomings of conventional mount stabilization methods, such as complex structure, low reliability, and limited antenna operating range, by proposing a novel mount capable of optimized tracking under extremely high sea states. This invention overcomes the deficiencies of conventional mounts, simplifies the structural design, and improves system reliability. More importantly, it develops and upgrades the corresponding kinematic equations for the novel mount, ensuring the feasibility of the antenna system and ultimately guaranteeing uninterrupted tracking of the target satellite, maintaining a stable and uninterrupted communication link.

Claims

1. A bearing-crossing-pitch type mounting system adapted to extremely high sea states, characterized in that, The system includes an azimuth-cross-pitch mount, on which are mounted motors that drive the rotation of each axis, drivers that control the motor rotation, encoders that collect azimuth, cross, and pitch axis angle information, and a controller that receives driver, encoder, and navigation information. After collecting the axis angle encoding information, the encoders report it to the drivers. The drivers then parse and process the received encoding information and report it to the controller in CAN message format as feedback for each axis. The controller operates as follows: The controller receives navigation information reported by the navigation system, including the ship's longitude and latitude, roll, pitch and heading information; When the controller receives a tracking command from the station monitoring, it uses the target satellite information and the ship's latitude and longitude information as inputs to calculate the theoretical geographic angle of the current target satellite: In the formula, Theoretical azimuth angle of the target star; Theoretical elevation angle of the target satellite; : Latitude of the ship; Longitude of the target star; : Warship longitude; Earth's radius; The altitude of the target satellite above the ground; Based on the ship's current heading, roll, and pitch information, the controller calculates the target deck angle pointing towards the target star using optimized inverse kinematics equations; the optimized inverse kinematics equations are: In the formula, The azimuth angle at which the antenna points to the target; The elevation angle of the antenna pointing towards the target; The antenna guides the ship's heading as given by the inertial navigation system; The pitch angle of the hull is given by the antenna-guided inertial navigation system; The hull roll angle given by the antenna-guided inertial navigation system; : The azimuth deck angle in the inertial navigation deck coordinate system, with the antenna pointing towards the bow at zero, and the top-view clockwise angle increasing; : The pitch angle of the deck in the inertial navigation deck coordinate system is zero when the antenna points to the deck plane and 90° when it points to the mast; Cross deck angle in the inertial navigation deck coordinate system: azimuth is zero, elevation is 90°, antenna pointing towards the mast is zero, and deviation to starboard is positive; The controller takes the target deck angle information as input and the shaft angle information reported by the driver as feedback, and calculates the control quantity that meets the design requirements according to the control law. The controller sends the control quantity to the driver, which drives the corresponding motor to rotate into position, thereby pointing the antenna towards the target star.

2. The azimuth-cross-pitch type mounting system adapted to extremely high sea states according to claim 1, characterized in that, The encoder is an incremental photoelectric encoder with 500 lines and a total code count of 2000.

3. The azimuth-cross-pitch type mounting system adapted to extremely high sea states according to claim 1, characterized in that, The azimuth axis and cross axis of the azimuth-cross-pitch type mount are orthogonal.

4. The azimuth-cross-pitch type mount system adapted to extremely high sea states according to claim 1, characterized in that, The azimuth-cross-pitch type mount uses a slip ring structure for its azimuth axis to ensure the continuity of azimuth axis rotation.

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