A composite control method and control device for a three-axis hybrid inertial navigation system

Abstract

The present invention provides a composite control method and control device for a three-axis hybrid inertial navigation system. Based on IMU attitude information and angular measurement information of a three-axis indexing mechanism, the attitude transfer matrix from the carrier coordinate system to the navigation coordinate system is calculated, and the carrier attitude Euler angle is solved, which is recorded as the isolated command angle. Based on the isolated command angle, each target modulation command angle obtained in a static state, and the transfer matrix from the carrier coordinate system to the three-axis indexing mechanism coordinate system, each composite command control angle corresponding to each target modulation command angle is solved; and the three-axis indexing mechanism is controlled. The composite control scheme provided by the present invention is used to overcome the defects of the prior art such as the limitation of carrier maneuverability or poor stability, and ensure that the system improves the navigation accuracy and stability of the inertial navigation system by isolating the carrier angular motion while eliminating the influence of modulation device errors.

Description

Technical Field

[0001] The present invention relates to the field of inertial navigation, and more particularly to a composite control method and a control device for a three-axis hybrid inertial navigation system. Background Art

[0002] The accuracy of an inertial navigation system is primarily affected by initial alignment errors, inertial device errors, and vehicle motion, which in turn lead to navigation errors such as divergence and oscillation. In high-precision, long-endurance, three-axis hybrid inertial navigation systems, initial alignment errors are kept to a minimum after a long period of alignment. Therefore, navigation accuracy is primarily affected by inertial device errors and vehicle motion.

[0003] Currently, the main method to improve the hybrid inertial navigation system is to use high-precision inertial devices and perform dual-axis modulation under the carrier system, but it is only applicable when the carrier angular motion is small or the gyro scale factor error is stable. Summary of the Invention

[0004] In order to suppress the coupling effect between carrier motion and device errors and improve the accuracy of an inertial navigation system, the present invention provides a composite control method and a control device for a three-axis hybrid inertial navigation system.

[0005] According to a first aspect of the present invention, a composite control method for a three-axis hybrid inertial navigation system is provided. The three-axis hybrid inertial navigation system includes an inertial measurement unit (IMU) and a three-axis indexing mechanism. The control method includes:

[0006] Step 1: Initially align the three-axis hybrid inertial navigation system. Based on the IMU attitude information after initial alignment, control the rotation of the three-axis indexing mechanism so that the IMU coordinate system coincides with the local geographic coordinate system.

[0007] Step 2: Based on the IMU attitude information and the angle measurement information of the three-axis indexing mechanism, the attitude transfer matrix from the carrier coordinate system to the navigation coordinate system is calculated, and the carrier attitude Euler angle is solved, which is recorded as the isolation command angle;

[0008] Step 3: Calculate the first attitude transfer matrix from the carrier coordinate system to the outer ring axis coordinate system according to the isolation instruction angle The second attitude transfer matrix of the outer ring coordinate system relative to the middle ring coordinate system And the third attitude transfer matrix of the middle ring coordinate system relative to the inner ring coordinate system

[0009] Step 4: Obtain each target modulation command angle under static conditions;

[0010] Step 5: Based on the isolated command angle, each target modulation command angle and the first attitude transfer matrix, the second attitude transfer matrix and the third attitude transfer matrix, solving each composite command control angle corresponding to each target modulation command angle;

[0011] Step six: Control the three-axis indexing mechanism based on each compound instruction control angle.

[0012] According to a second aspect of the present invention, a composite control device for a three-axis hybrid inertial navigation system is provided, comprising an inertial measurement unit and a three-axis indexing mechanism, wherein a navigation solver board is installed in the inertial measurement unit, and an angle measurement control board and a servo drive board are installed in the three-axis indexing mechanism;

[0013] The navigation solver is used to calculate the attitude transfer matrix from the carrier coordinate system to the navigation coordinate system based on the IMU attitude information and the angle measurement information of the three-axis indexing mechanism, and solve the carrier attitude Euler angle, which is recorded as the isolation command angle; and calculate the first attitude transfer matrix from the carrier coordinate system to the outer ring axis coordinate system according to the isolation command angle. The second attitude transfer matrix of the outer ring coordinate system relative to the middle ring coordinate system And the third attitude transfer matrix of the middle ring coordinate system relative to the inner ring coordinate system and solving each composite command control angle corresponding to each target modulation command angle based on each target modulation command angle obtained under static conditions, the isolated command angle, the first attitude transfer matrix, the second attitude transfer matrix, and the third attitude transfer matrix, and sending each composite command control angle to a measurement control board;

[0014] The measurement control board is used to obtain the angle measurement information of the three-axis indexing mechanism and forward it to the navigation solution board; and control the servo drive board to control the rotation of the three-axis indexing mechanism according to each composite instruction control angle.

[0015] The present invention provides a composite control method and control device for a three-axis hybrid inertial navigation system. Based on IMU attitude information and angle measurement information from a three-axis indexing mechanism, the method calculates the attitude transfer matrix from the carrier coordinate system to the navigation coordinate system and solves for the carrier attitude Euler angles, which are recorded as isolation command angles. Based on the isolation command angles, the acquired target modulation command angles in a static state, and the transfer matrix from the carrier coordinate system to the three-axis indexing mechanism coordinate system, each composite command control angle corresponding to each target modulation command angle is solved. The three-axis indexing mechanism is then controlled. Utilizing the three-axis indexing mechanism, a carrier motion isolation strategy is added based on a dual-axis modulation scheme, enabling the device to modulate in a geographic system and fully utilize the system's performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1A flow chart of a composite control method for a three-axis hybrid inertial navigation system provided by the present invention;

[0017] Figure 2 It is the structural diagram of the three-axis indexing mechanism;

[0018] Figure 3 It is the flow chart of the composite control scheme;

[0019] Figure 4 A schematic structural diagram of a control device for a three-axis hybrid inertial navigation system provided by the present invention;

[0020] Figure 5 It is a schematic diagram of the overall structure of the control device of the three-axis hybrid inertial navigation system;

[0021] Figure 6 is a circuit structure diagram of a current detection unit;

[0022] Figure 7 This is a comparison chart of the error curves of modulation control and compound control. DETAILED DESCRIPTION

[0023] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0024] Example 1

[0025] A composite control method for a three-axis hybrid inertial navigation system, see Figure 1 , the composite control method mainly includes the following steps:

[0026] Step 1: Perform initial alignment on the three-axis hybrid inertial navigation system. Based on the IMU attitude information after initial alignment, control the rotation of the three-axis indexing mechanism so that the IMU coordinate system coincides with the local geographic coordinate system.

[0027] It can be understood that the three-axis hybrid inertial navigation system of the embodiment of the present invention mainly includes an inertial measurement unit IMU and a three-axis indexing mechanism. Figure 2 This is a schematic diagram of the three-axis indexing mechanism of the inertial device of a high-precision, long-endurance, three-axis hybrid inertial navigation system. The three rings are defined as the inner ring, middle ring, and outer ring from the inside to the outside, respectively. The corresponding rotation axes are defined as the inner ring axis, middle ring axis, and outer ring axis, and the coordinate systems they are in are the inner ring coordinate system, middle ring coordinate system, and outer ring coordinate system, respectively. When installing the inertial measurement unit, align the Y axis of the IMU coordinate system with the inner ring axis. After power-on, adjust the initial position of the rotation axis so that the X axis of the IMU coordinate system coincides with the middle ring axis and the Z axis of the IMU coordinate system coincides with the outer ring axis, so that the IMU coordinate system coincides with the local geographic coordinate system.

[0028] Step 2: Based on the IMU attitude information and the angle measurement information of the three-axis transfer mechanism, the attitude transfer matrix from the carrier coordinate system to the navigation coordinate system is calculated, and the carrier attitude Euler angle is solved, which is recorded as the isolation command angle.

[0029] Specifically, based on the IMU attitude information and the angle measurement information of the three-axis indexing mechanism, the attitude transfer matrix from the carrier coordinate system (b system) to the navigation coordinate system (n system) is calculated, and the carrier attitude Euler angle is solved: azimuth Pitch angle θ s , roll angle γ s , denoted as the isolation command angle.

[0030] Step 3: Calculate the first attitude transfer matrix from the carrier coordinate system to the outer ring axis coordinate system according to the isolation instruction angle The second attitude transfer matrix of the outer ring coordinate system relative to the middle ring coordinate system And the third attitude transfer matrix of the middle ring coordinate system relative to the inner ring coordinate system

[0031] Specifically, the attitude transfer matrix from the b system to the outer ring axis coordinate system (w system) is calculated based on the isolation command angle calculated in step 2 The attitude transfer matrix of the outer ring coordinate system (w system) relative to the middle ring coordinate system (z system) The attitude transfer matrix of the middle ring coordinate system (z system) relative to the inner ring coordinate system (IMU three-axis coordinate system (s system)) The calculation is as follows:

[0032]

[0033]

[0034]

[0035] Step 4: Obtain each target modulation instruction angle under static conditions.

[0036] It can be understood that the target modulation command angle in the embodiment of the present invention adopts a 48-position modulation scheme, which rotates around the celestial axis and the north axis of the geographic system respectively. The target modulation command angle design under static conditions is shown in Table 1 below. To rotate 180° around the Z axis of the navigation coordinate system, To rotate 180° in the opposite direction around the Z axis of the navigation coordinate system, To rotate 180° in the positive direction around the Y axis of the navigation coordinate system, In order to rotate 180° in the opposite direction around the Y axis of the navigation coordinate system, for the 48 position modulation schemes, the three-axis indexing mechanism is controlled to rotate according to the rotation sequence.

[0037] Table 1 Target modulation command angle

[0038]

[0039]

[0040] Step 5: Based on the isolated instruction angle, each target modulation instruction angle and the first attitude transfer matrix, the second attitude transfer matrix and the third attitude transfer matrix, solve each composite instruction control angle corresponding to each target modulation instruction angle.

[0041] Since the target modulation command angle obtained in step 4 is the command angle in the geographic coordinate system, it is necessary to convert the target modulation command angle into the actual modulation command angle during the actual driving process of the three-axis indexing mechanism. According to each target modulation command angle and the first posture transfer matrix, the second posture transfer matrix and the third posture transfer matrix, the actual modulation command angle corresponding to each target modulation command angle is solved by the following formula:

[0042]

[0043] Where θ Target , γ Target 、 It is the target modulation instruction angle when the three-axis indexing mechanism executes the modulation strategy under static conditions, and is obtained according to the rotation order; θ tiaozhi , γ tiaozhi In order to isolate the carrier motion condition, the actual modulation command angle when the three-axis indexing mechanism executes the modulation strategy needs to be solved.

[0044] When the carrier pitch angle θ s ≠±90°, the actual modulation command angle θ tiaozhi , γ tiaozhi There is a solution, and we can calculate:

[0045]

[0046] The actual modulation command angle corresponding to each target modulation command angle is obtained by solving the problem, and then each composite control command angle is calculated based on each actual modulation command angle and the isolated command angle:

[0047]

[0048] Where θ zhiling , γ zhiling and is the compound control command angle.

[0049] The above formula is used to solve the actual modulation command angle corresponding to each target modulation command angle. For the 48 target modulation command angles, the rotation order of the 48 actual modulation command angles obtained through the calculation is consistent with the rotation order of the 48 target modulation command angles. Therefore, the rotation order of the 48 composite control command angles finally calculated is consistent with the rotation order of the 48 target modulation command angles obtained.

[0050] Step six: Control the three-axis indexing mechanism based on each compound instruction control angle.

[0051] It can be understood that based on the calculated multiple composite control instruction angles, the three-axis indexing mechanism is controlled to perform rotation modulation in accordance with the rotation order.

[0052] See Figure 3 , which is a working principle diagram of the three-axis indexing mechanism under the composite control scheme of the three-axis hybrid inertial navigation system in an embodiment of the present invention, mainly includes the following steps:

[0053] (1) Use the inertial measurement unit (IMU) to measure the motion information of the IMU relative to the inertial system, and obtain the current IMU attitude transformation matrix through navigation solution. Based on the three-axis indexing mechanism angle measurement unit, calculate the inertial device base attitude transformation matrix and obtain the base angular motion information.

[0054] (2) The three-axis indexing mechanism is used to rotate the IMU, isolating the influence of the carrier angular motion on the IMU. At the same time, the IMU is periodically flipped symmetrically in the navigation coordinate system, projecting the deterministic error of the inertial element into a periodic oscillation error in the navigation coordinate system, thereby suppressing the influence of the inertial device error on the navigation results and improving the navigation accuracy of the system.

[0055] See Figure 4 , which is the workflow diagram of the composite control method, mainly includes the following steps:

[0056] (1) During the equipment startup process, the main program performs a power-on self-test on the three-axis mixed-inertia system to confirm that the inertial components, goniometer board, and servo control board are working properly, and that the physical connections of the equipment are normal;

[0057] (2) After the device starts normally, the navigation board sends a reset command, and the servo control mechanism drives the IMU to rotate to the initial position;

[0058] (3) During the coarse alignment process, the composite control angle is always the initial angle; after entering the fine alignment, the composite control angle is calculated and solved by the comprehensive calculation of the base Euler angle and the calibration rotation scheme; after entering the navigation phase, the composite control angle is calculated and solved by the comprehensive calculation of the base Euler angle and the modulation command angle.

[0059] (4) The servo control mechanism continuously controls the three-axis rotating shaft system to rotate according to the compound control angle until the equipment operation is completed and the power is cut off.

[0060] In order to suppress the coupling effect of carrier motion and device errors and improve the accuracy of the inertial navigation system, the present invention utilizes a three-axis indexing mechanism and a two-axis modulation scheme to add a carrier motion isolation strategy, so that the inertial navigation system has the ability to be modulated in the geographic system and fully exerts the system efficiency.

[0061] Example 2

[0062] A composite control device for a three-axis hybrid inertial navigation system, see Figure 5 The composite control device includes an inertial measurement unit and a three-axis transfer mechanism. The inertial measurement unit is equipped with a navigation solver board, and the three-axis transfer mechanism is equipped with an angle measurement control board and a servo drive board.

[0063] The navigation solver is used to calculate the attitude transfer matrix from the carrier coordinate system to the navigation coordinate system based on the IMU attitude information and the angle measurement information of the three-axis indexing mechanism, and solve the carrier attitude Euler angle, which is recorded as the isolation command angle; and calculate the first attitude transfer matrix from the carrier coordinate system to the outer ring axis coordinate system according to the isolation command angle. The second attitude transfer matrix of the outer ring coordinate system relative to the middle ring coordinate system And the third attitude transfer matrix of the middle ring coordinate system relative to the inner ring coordinate system Based on the acquired target modulation command angles under static conditions, the isolated command angles, and the first, second, and third attitude transfer matrices, each composite command control angle corresponding to each target modulation command angle is calculated, and each composite command control angle is sent to a measurement control board. The measurement control board is configured to acquire angle measurement information of the three-axis indexing mechanism and forward it to the navigation solver board. Based on each composite command control angle, the servo drive board is configured to control the rotation of the three-axis indexing mechanism.

[0064] It is understandable that, see Figure 5 , an electrical system of a three-axis indexing mechanism consisting of an angle measurement control board and a servo drive board was designed. In addition, a navigation solver board was also installed in the inertial navigation unit.

[0065] Among them, the angle measurement control board adopts the structure of core board + base board. The core board uses Zynq7020SOC core board. The base board is mainly composed of RS422 transceiver circuit, 12-channel ADC circuit and power supply circuit. Its composition block diagram is as follows Figure 5 shown.

[0066] The angle measurement control board performs digital closed-loop control of the position and velocity of the three-axis indexing mechanism based on instructions from the navigation solver (IMU). It provides PWM pulse signals to the servo driver board and receives the current detection unit from the servo driver board, converting the sampled current into a voltage signal. This signal is then converted to analog-to-digital (A / D) to form a current feedback closed-loop. The angle measurement control board also transmits operating status information of the servo driver board and the board itself to the navigation solver via an RS422 transceiver circuit, while also providing angle measurement and self-test information to the navigation solver. The main functions of the angle measurement control board are as follows:

[0067] 1) The SOC core board outputs PWM signals to control the movement and rotation of the three-axis indexing mechanism;

[0068] 2) Obtain the angle measurement information of the reading head through the RS422 interface, and provide the turntable angle measurement information and self-test information to the navigation solver board through the RS422 serial port;

[0069] 3) With running signal indicator light function;

[0070] 4) Dual digital closed loop function of position and speed;

[0071] 5) High-precision position angle measurement function;

[0072] 6) Provide +5V power to the read head and servo driver board.

[0073] Among them, the servo drive board is mainly composed of a current detection unit and a power drive module, which are described in detail as follows:

[0074] (1) Current detection unit:

[0075] In a servo control system, the controller needs to accurately and timely know the actual current in the motor's stator windings to implement closed-loop current control and design current protection circuits. In an embodiment of the present invention, current detection uses a Hall effect current sensor. This method utilizes the Hall effect of the Hall effect sensor to convert the magnetic signal generated by the current into an electrical signal based on the Hall effect principle. This achieves signal isolation, minimizes electrical interference, and provides high accuracy.

[0076] The Hall sensor is Ltsr6-NP, with an output-to-input ratio of 4:1000, a maximum input current of 9A, and an accuracy of 0.5%. After the current passes through the Hall sensor, it is converted into a proportional small current signal and input into the electrical isolation. The small current signal is converted into a corresponding voltage signal through a precision resistor and sent to the A / D conversion chip through an op amp. Take the V phase current sampling as an example. The current detection unit circuit diagram is as follows Figure 6As shown, the current sampling unit is actually a chip N1. Pins 1, 2, and 3 of chip N1 are connected to the servo motor's current output. Pins 4, 5, and 6 of chip N1 are connected to the servo motor's phase A or B current. Pin 7 is connected to the output reference voltage, pin 8 is the output resolution voltage terminal, pin 9 is grounded, and pin 10 is connected to a 5V power supply. The model of chip N1 is LTSR6-NP.

[0077] (2) Power drive module:

[0078] The power driver module is a three-phase bridge with gate drivers and bridge arms composed entirely of MOS transistors. It primarily drives AC servo motors by receiving PWM switching signals from the goniometer control board to vary the frequency and amplitude of the three-phase output voltage. It offers a continuous output current of 30A and a maximum power supply voltage of 75VDC. The module features comprehensive protection features, including VCC undervoltage lockout, adjustable dead time, and a disable function. This not only reduces system size and development time, but also enhances reliability.

[0079] The main functions of the power drive module are as follows:

[0080] 1) One board contains two power drive modules, which can drive two permanent magnet synchronous motors simultaneously;

[0081] 2) With external input signal brake function;

[0082] 3) Input and output signal isolation function;

[0083] 4) Power status indication function;

[0084] 5) Undervoltage lockout function inside the driver chip.

[0085] As a preferred embodiment, the three-axis hybrid laser inertial navigation system includes a high-precision inertial measurement unit (IMU) three-axis indexing mechanism, a navigation computer and related circuits.

[0086] The inertial measurement unit (IMU) uses inertial device sensing to measure angular and linear motion, which it then outputs to the navigation solver for inertial navigation. This determines the IMU's attitude in the navigation coordinate system. Combining the three-axis indexing mechanism's angle measurement information with the modulation scheme's instructions, it calculates the composite control command angle and outputs it to the three-axis indexing mechanism.

[0087] The three-axis indexing mechanism completes the carrier angular motion isolation and rotation modulation by receiving the composite control instructions output by the navigation computer, and receives the synchronization signal to complete the inner, middle and outer ring angle measurement sampling and output it to the navigation computer.

[0088] In a preferred embodiment, the same system is used to test the modulation control scheme and the composite control scheme. The navigation results are as follows: Figure 7 As shown in the figure, due to the influence of carrier motion, the error of using only the modulation scheme is large, while the composite control scheme has higher accuracy, which can prove the effectiveness of the composite control scheme.

[0089] The present invention provides a composite control scheme for a high-precision, long-endurance, three-axis hybrid laser inertial navigation system, which can effectively eliminate the effects of carrier angular motion and device errors on navigation accuracy. The main beneficial effects are as follows:

[0090] (1) Eliminate the influence of device constant bias error;

[0091] (2) Eliminate the influence of asymmetric error of scale factor;

[0092] (3) Eliminate the coupling effect of carrier angular motion and scale factor symmetry error.

[0093] This invention designs a composite control scheme for high-precision, long-endurance, three-axis hybrid laser inertial navigation systems. It fully exploits the potential of hybrid laser inertial navigation systems, improving navigation accuracy and meeting the needs of various offshore platforms and users. Combining high-precision laser gyros, precision shafting machining, and advanced servo control, it achieves high-precision carrier motion isolation and modulation.

[0094] It should be noted that, in the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0095] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0096] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0097] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0098] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0099] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0100] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A composite control method for a three-axis hybrid inertial navigation system, characterized in that: The three-axis hybrid inertial navigation system includes an inertial measurement unit (IMU) and a three-axis indexing mechanism, and the control method includes: Step 1: Initially align the three-axis hybrid inertial navigation system. Based on the IMU attitude information after initial alignment, control the rotation of the three-axis indexing mechanism so that the IMU coordinate system coincides with the local geographic coordinate system. Step 2: Based on the IMU attitude information and the angle measurement information of the three-axis indexing mechanism, the attitude transfer matrix from the carrier coordinate system to the navigation coordinate system is calculated, and the carrier attitude Euler angle is solved, which is recorded as the isolation command angle; Step 3: Calculate the first attitude transfer matrix from the carrier coordinate system to the outer ring axis coordinate system according to the isolation instruction angle The second attitude transfer matrix of the outer ring coordinate system relative to the middle ring coordinate system And the third attitude transfer matrix of the middle ring coordinate system relative to the inner ring coordinate system Step 4: Obtain each target modulation command angle under static conditions; Step 5: Based on the isolated command angle, each target modulation command angle and the first attitude transfer matrix, the second attitude transfer matrix and the third attitude transfer matrix, solving each composite command control angle corresponding to each target modulation command angle; Step 6: Control the three-axis indexing mechanism based on each composite command control angle; the carrier posture Euler angle in step 2 includes the carrier azimuth angle Pitch angle θ s and roll angle γ s ; The step three calculates the first posture transfer matrix by the following formula Second attitude transfer matrix And the third attitude transfer matrix The target modulation command angle includes 48 position modulation schemes, which rotate around the geographic system celestial axis and the geographic system north axis respectively, wherein the 48 position modulation schemes have a set rotation order; The step 5, based on the isolated command angle, each target modulation command angle, and the first attitude transfer matrix, the second attitude transfer matrix, and the third attitude transfer matrix, solves each composite command control angle corresponding to each target modulation command angle, including: According to each target modulation instruction angle and the first posture transfer matrix, the second posture transfer matrix and the third posture transfer matrix, the actual modulation instruction angle corresponding to each target modulation instruction angle is solved by the following formula: Where θ Target , γ Target 、 It is the target modulation instruction angle when the three-axis indexing mechanism executes the modulation strategy under static conditions, and is obtained according to the rotation order; θ tiaozhi , γ tiaozhi To isolate the actual modulation command angle of the three-axis indexing mechanism when executing the modulation strategy under the condition of carrier motion; When the carrier pitch angle θ s ≠±90°, the actual modulation command angle θ tiaozhi , γ tiaozhi There is a solution, and we can calculate: Calculate each composite control instruction angle according to each actual modulation instruction angle and the isolation instruction angle: Where θ zhiling , γ zhiling and is the compound control command angle.

2. The control method according to claim 1, characterized in that: The three ring frames of the three-axis indexing mechanism are defined as the inner ring, middle ring and outer ring from the inside to the outside, and the corresponding rotation axes are the inner ring axis, middle ring axis and outer ring axis. Among them, the coordinate system of the inner ring axis is the inner ring coordinate system, the coordinate system of the middle ring axis is the middle ring coordinate system, and the coordinate system of the outer ring axis is the outer ring coordinate system.

3. A composite control device for a three-axis hybrid inertial navigation system, characterized in that: It includes an inertial measurement unit and a three-axis indexing mechanism, wherein the inertial measurement unit is equipped with a navigation solver board, and the three-axis indexing mechanism is equipped with an angle measurement control board and a servo drive board; The navigation solver is used to calculate the attitude transfer matrix from the carrier coordinate system to the navigation coordinate system based on the IMU attitude information and the angle measurement information of the three-axis indexing mechanism, and solve the carrier attitude Euler angle, which is recorded as the isolation command angle; and calculate the first attitude transfer matrix from the carrier coordinate system to the outer ring axis coordinate system according to the isolation command angle. The second attitude transfer matrix of the outer ring coordinate system relative to the middle ring coordinate system And the third attitude transfer matrix of the middle ring coordinate system relative to the inner ring coordinate system and solving each composite command control angle corresponding to each target modulation command angle based on each target modulation command angle obtained under static conditions, the isolated command angle, the first attitude transfer matrix, the second attitude transfer matrix, and the third attitude transfer matrix, and sending each composite command control angle to a measurement control board; The measurement control board is used to obtain the angle measurement information of the three-axis indexing mechanism and forward it to the navigation solution board; and control the servo drive board to control the rotation of the three-axis indexing mechanism according to each composite instruction control angle.

4. The control device according to claim 3, characterized in that The angle measurement control board includes a core board and a base board, wherein the core board is a SOC core board, and the base board includes an RS422 transceiver circuit, a 12-channel ADC circuit and a power supply circuit; The angle measurement control board is used to control the angle according to the composite instruction sent by the navigation solver board, provide a PWM pulse signal to the servo driver board, and receive the voltage signal converted by the servo driver board according to the sampled current and perform AD conversion to form a current feedback closed loop, so as to realize the control drive of the digital closed loop of the position and speed of the three-axis indexing mechanism; And the working status information of the servo driver board and this board is sent to the navigation solver board through the RS422 transceiver circuit, and the angle measurement information and self-test information are provided to the navigation solver board.

5. The control device according to claim 4, characterized in that The servo drive board includes a current sampling unit and a power drive module; The current sampling unit is a Hall current sensor, which is used to sample the actual current in the stator winding of the servo motor, convert it into a voltage signal, and feed it back to the angle measurement control board; The power drive module is used to receive the PWM switch signal output by the angle measurement control board to change the frequency and amplitude of the three-phase output voltage to drive the AC servo motor.

6. The control device according to claim 5, characterized in that The current sampling unit is chip N1, pins 1, 2 and 3 of the chip N1 are connected to the current output end of the servo motor, pins 4, 5 and 6 of the chip N1 are all connected to the A phase or B phase current of the servo motor, pin 7 is connected to the output end reference voltage, pin 8 is the output solution voltage end, pin 9 is grounded, and pin 10 is connected to a 5V power supply.

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