Message error control and platform motion compensation method based on space-based navigation source

Abstract

The present invention provides a method for message error control and platform motion compensation based on an air-based navigation source, and belongs to the field of aerospace engineering and control system technology. The method comprises the following steps: first, calculating the message parameters of the planned track; then, calculating the planned motion parameters of the platform based on the message parameters, and obtaining the current actual motion parameters through the airborne motion sensor; then, comparing the planned motion parameters with the actual motion parameters, and calculating the motion compensation amount; finally, inputting the motion compensation amount into the motion control system, and generating the corresponding control law in real time to compensate for the navigation message error. The method improves the autonomy and stability of the platform, effectively reduces the influence of external factors on navigation accuracy, enhances the platform's adaptability to complex environments, and improves the robustness of the system under various complex environments and conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of aerospace engineering and control systems, and in particular relates to a method for message error control and platform motion compensation based on an air-based navigation source. Background Art

[0002] In the field of aerospace engineering and control system technology, air-based platforms such as Unmanned Aerial Vehicles (UAVs) and Pseudo Satellites are playing an increasingly important role. These platforms can not only perform complex tasks, but also serve as navigation signal sources to provide positioning services to ground users. However, the motion control of most air-based platforms currently still mainly relies on signals from external navigation systems such as the Global Navigation Satellite System (GNSS), and has not yet fully utilized the navigation messages broadcast by the platform itself to optimize its motion control performance, which to a certain extent limits the application potential of air-based platforms as navigation sources.

[0003] Although the use of navigation messages provided by ground-based and air-based augmented signals (such as the Global Positioning System, GPS) to control the position and attitude of air-based platforms has been widely studied and applied, most of these systems rely on external signal sources. Existing technologies determine the position and speed of air-based platforms by receiving navigation signals from the outside, receiving GNSS signals through satellite signal receivers, and the platform's own sensors such as inertial navigation and barometers, and then use this information for track planning and dynamic control.

[0004] However, the existing technologies rarely involve using the navigation message (NavigationMessage) broadcast by the air-based platform itself to control the platform's motion parameters. In the research in this field, the traditional control system generally only acts as the transmitter of the signal, and does not participate in the feedback link. That is, the existing technology often only uses the navigation message sent to other receivers, rather than feeding back this information for its own motion parameter correction.

[0005] Although existing technologies have been able to alleviate the impact of navigation message errors on the positioning accuracy of air-based platforms to a certain extent, they still face many challenges in practical applications. In particular, how to identify and compensate for navigation message errors in real time and accurately, and how to seamlessly integrate this error compensation strategy into the motion control system of air-based platforms, are still urgent issues to be solved in this technical field. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a method for message error control and platform motion compensation based on air-based navigation sources, and introduces a closed-loop control mechanism in the air-based platform, so that the platform is not only the transmitter of navigation signals, but also the executor of self-correction using these signals, that is, the navigation messages broadcast by the platform itself are used to correct its own position and motion state. The method can greatly improve the autonomy of the air-based platform and its stability when GPS signals are unavailable, and realize accurate compensation for the motion control of the air-based platform, thereby significantly improving the positioning accuracy and task execution efficiency of the air-based platform in complex environments.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A method for message error control and platform motion compensation based on an air-based navigation source comprises the following steps:

[0009] Step 1: Calculate the message parameters of the planned flight path: Generate the corresponding navigation message parameters from the flight path information according to the planned flight path;

[0010] Step 2: Calculate the planned motion parameters of the air-based platform based on the navigation message parameters to obtain the position, velocity and acceleration information of the platform under the ideal state; obtain the actual motion parameters of the air-based platform in real time through the onboard motion sensor;

[0011] Step 3: Compare the planned motion parameters of the air-based platform with the actual motion parameters, calculate the deviation between the two, and obtain the motion compensation amount of the air-based platform;

[0012] Step 4: Input the calculated motion compensation amount into the motion control system to generate corresponding control instructions, drive the actuator to adjust the motion state of the air-based platform in real time, and compensate for the navigation message error.

[0013] The beneficial effects of the present invention are:

[0014] The navigation message broadcast by the air-based platform itself is used to control the motion parameters, which reduces the dependence on external signal sources. Especially when the external signal is limited or lost, the autonomy and stability of the platform can be significantly improved. The real-time monitoring of the motion state of the air-based platform and the dynamic correction mechanism of the internal navigation message are proposed to effectively reduce the impact of external factors such as multipath effect, ionospheric and tropospheric delay on navigation accuracy. At the same time, since the need to wait and process external signals is reduced, the processing delay can also be reduced, and a more timely response can be made to the rapidly changing motion state. The highly integrated navigation system used can process a variety of sensor data, including but not limited to inertial measurement unit (IMU) data, which enhances the adaptability of the air-based platform to different situations and improves the robustness of the system in various environments and conditions. Even when some sensor data is unavailable, the system can continue to perform tasks, improving the mission success rate and the overall reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a principle block diagram of the message error control and platform motion compensation method based on air-based navigation source of the present invention;

[0016] Figure 2 This is a flow chart of the error compensation algorithm of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] like Figure 1 The figure shows the overall framework of the message error control and platform motion compensation method based on the airborne navigation source. The following is a detailed description of the key steps and components mentioned in the figure:

[0019] Starting time: This is the time point when the whole process starts. At this moment, the initial telegram parameter calculation is performed, including the predetermined position and expected motion state of the platform.

[0020] Message parameter calculation: This step involves calculating the relevant message parameters of the planned trajectory, which will be used to determine the planned motion trajectory of the air-based platform.

[0021] Calculation of motion parameters of planned trajectory: In this step, the predetermined motion parameters of the air-based platform, such as speed, acceleration, etc., are calculated based on the message parameters.

[0022] Obtain current motion parameters: The current position and motion status of the platform are obtained in real time through onboard sensors such as inertial measurement units, barometric altimeters, and GNSS receivers.

[0023] Correction moment: This is the moment when the predetermined parameters are corrected based on the actual motion parameters obtained to accurately compensate for any deviations.

[0024] Error compensation calculation: The error compensation result is input into the motion control system, and the motion control of the airborne platform is adjusted according to the error to ensure that the platform moves according to the predetermined trajectory.

[0025] Motion control system adjustment: The error compensation results are input into the motion control system, and the motion control of the airborne platform is adjusted according to the error to ensure that the platform moves according to the predetermined trajectory.

[0026] Before the second message broadcast: Before the next message broadcast, ensure that all error compensation and adjustments have been completed to improve the accuracy and reliability of the navigation message.

[0027] The entire system operates periodically according to the process of "parameter calculation-error compensation-motion control-effect monitoring-feedback optimization". Through the interactive feedback of air-based navigation source messages and its own motion parameters, it realizes the continuous improvement of navigation accuracy and platform control performance. It is an innovative adaptive closed-loop control method. It specifically includes the following steps:

[0028] Step 1: Calculation of message parameters for planned track

[0029] The telegram adaptation of the space-based platform in the Earth-centered Earth-fixed coordinate system (ECEF) at the start time requires changing the calculation method of the original 18-parameter ephemeris model, and broadcasting the position of the space-based platform without changing the original telegram format. First, perform an accurate position calibration. Because the coordinates in the Earth-centered Earth-fixed coordinate system ECEF need to be represented, the original satellite angular velocity must be corrected to 0, so , .

[0030] is the average angular velocity of the satellite at the reference time in the original message parameters, is the difference between the satellite average angular velocity at the reference time and the calculated value, is the rate of change of the difference between the satellite average angular velocity at the reference time and the calculated value, is the gravitational constant in the geocentric inertial coordinate system. , It is the semi-major axis distance of the imaginary orbit at the reference time.

[0031] In order to ensure that the ECEF coordinates of the Earth-centered Earth-fixed coordinate system do not change with time at the time of the platform's broadcast, the orbital inclination of the hypothetical orbit is required to be , the longitude of the ascending node of the hypothetical orbit In the original satellite orbit model, the longitude of the ascending node is Usually expressed as in, Indicates the time difference between the current time and the reference time. To simplify the adaptation process, it is assumed that the airborne platform is located in an elliptical orbit with the center of the earth as the focus and is always at the perigee, that is, the original mean anomaly angle is 0. At the same time, the perigee argument Set to , eccentricity The relevant values ​​of the reference ellipsoid are used.

[0032] The distance between the long and short axes of the six elements of the navigation satellite orbit is calculated using , orbital inclination , Longitude of ascending node The spatial position of the airborne platform can be constrained. For convenience, the geographic coordinates of the platform are described later through the perigee argument. and the original anomaly The simplified settings of these two get the geographic coordinates and the major semi-axis distance , orbital inclination , Longitude of ascending node The relationship is:

[0033] ,

[0034] In the formula, Represents the longitude, latitude and curvature radius of the reference ellipsoid of the airborne platform.

[0035] And the latitude and longitude can be converted into coordinates of the Earth-centered Earth-fixed coordinate system ECEF by the following formula.

[0036]

[0037] In the formula is the three-dimensional coordinate of the airborne platform in the Earth-centered Earth-fixed coordinate system ECEF, is the eccentricity of the reference ellipsoid.

[0038] Step 2: Calculate the planned motion parameters of the air-based platform based on the message parameters of the planned trajectory, and obtain the motion parameters of the current actual path based on the motion sensor; specifically include:

[0039] Step 2.1: Calculation of motion parameters of planned trajectory

[0040] The X, Y, and Z coordinates in the Earth-fixed rectangular coordinate system are all about , , The three-variable function can be separated into Expand everywhere, They respectively represent the length of the major semi-axis, latitude and longitude of the reference point where the space-based platform is located at the time of message broadcasting in the ground-fixed rectangular coordinate system. Taking the coordinate of the X-axis as an example:

[0041] ,

[0042] in, Indicates the X coordinate about , , exist The gradient matrix at Indicates the coordinate of the airborne platform in the X-axis direction. This coordinate is about , , The ternary function of Represents the coordinate X about , , exist The Hessian matrix at Represents the coordinate X about , , exist The third-order partial derivative matrix at , Representation vector The transpose of , , Respectively , , The first derivative with respect to time is Indicates the time interval for the air-based platform to update its status. Respectively represent the status update interval Internal parameters The amount of change;

[0043] The velocity of the airborne platform in the X-axis direction in the Earth-centered Earth-fixed rectangular coordinate system for:

[0044] ,

[0045] Acceleration in the X-axis direction for:

[0046] ,

[0047] Acceleration in the X-axis direction for:

[0048] ,

[0049] Without considering high-order errors, the motion parameters (speed, acceleration, jerk) of the airborne platform can be constrained by the change rate of the semi-major axis, the change rate of the ascending node right ascension, and the change rate of the orbital inclination in the navigation message. A complete set of navigation messages corresponds to a unique motion trajectory of the airborne platform. The same calculation method can be used to calculate the speed, acceleration, and jerk in the Y and Z directions.

[0050] When such an airborne platform is used as a navigation source for the user, the motion characteristics of the airborne platform can be compensated for through the broadcast navigation message, so that the broadcast navigation message can accurately characterize the position of the airborne platform and predict the platform position within a period of time.

[0051] Step 2.2: The motion sensor obtains the current motion parameters

[0052] The airborne platform is equipped with a series of high-precision motion sensors to obtain the platform's motion state parameters in real time. These sensors may include: (1) Inertial Measurement Unit (IMU): composed of an accelerometer and a gyroscope, it can measure the acceleration and angular velocity of the airborne platform, thereby obtaining the platform's speed, position, and attitude information. (2) Barometric altimeter: By measuring the change in atmospheric pressure, the altitude information of the airborne platform can be accurately obtained. (3) GNSS receiver: Receives GNSS navigation message signals and provides the platform with absolute position, velocity, and time information.

[0053] These sensors collect data at a certain frequency and send the raw measurement data to the motion control system for processing. By fusing multiple sensor data, a high-precision and high-reliability motion state estimate of the airborne platform can be obtained, providing input for subsequent motion compensation control.

[0054] Step 3: Error compensation calculation

[0055] Here, the current motion parameters obtained by the motion sensor and the planned message parameters are corrected. In this step, the planned motion parameters of the air-based platform calculated in step 2.1 are directly used to adjust the actual motion state obtained by the motion sensor to achieve real-time compensation of navigation errors. The specific process is as follows:

[0056] First, define the planned motion parameters as the desired state vector :

[0057] X d = [ x d , y d , z d , x ˙ d , y ˙ d , z ˙ d , x ¨ d , y ¨ d , z ¨ d ] T

[0058] in, are the components of the desired position in the X, Y, and Z directions, respectively. are the expected velocity components, are the expected acceleration components respectively. It is the expected value of the state calculated based on the message broadcast in step 2.1.

[0059] Taking the components in the x direction as an example, the expectations are:

[0060]

[0061] in Indicates reference point The X coordinate component of the ground fixed system, and the same can be done for the Y\Z directions. At the same time, the actual motion parameters are expressed as the state vector :

[0062] X = [ x , y , z , x ˙ , y ˙ , z ˙ , x ¨ , y ¨ , z ¨ ] T

[0063] in, are the actual position components, are the actual velocity components, are the actual acceleration components respectively.

[0064] Then, calculate the deviation between the actual state and the expected state :

[0065]

[0066] Step 3 directly uses the planned motion parameters to adjust the actual motion state, thus achieving intuitive and efficient navigation error compensation control. This method has a fast response speed and relatively low computational complexity, and is very suitable for air-based platforms with fast motion state changes and high real-time requirements. While using PID control to compensate for errors, it can also eliminate steady-state errors (integral action) and improve dynamic response (differential action), providing a more precise and stable control effect. At the same time, the design of the PID gain matrix is ​​more flexible, and can be adjusted separately for different motion components (position, velocity, acceleration) to achieve better control performance.

[0067] Step 4: Motion control system adjustment

[0068] The motion control system is the core component of the air-based platform, responsible for real-time compensation control of the platform's motion according to the planned track, message adaptation information and motion sensor feedback. It mainly consists of the following modules:

[0069] Motion compensation control law design module: This module calculates the deviation information between the actual state and the expected state according to step 3 , design and generate real-time motion compensation control law. The specific design process is as follows:

[0070] Select control variables: According to the motion characteristics and control objectives of the airborne platform, select appropriate control variables, which include the three position, velocity, and acceleration components under the ground-fixed system.

[0071] Design compensation control law: Design compensation control law for the above motion parameters that need to be controlled , directly use the deviation information to adjust each actual motion state parameter:

[0072]

[0073] in, To control the output, is the deviation signal, , , They are proportional, integral, and differential gain matrices, respectively, and can be designed and debugged according to specific system characteristics and control requirements. As a control instruction, it is input into the motion control system to directly drive the actuator to change the actual motion of the airborne platform, so that it can track the planned trajectory as quickly as possible and achieve real-time compensation of navigation errors.

[0074] like Figure 2 As shown, an algorithm flow chart of the telegram error control and platform motion compensation method based on air-based navigation source proposed by the present invention is given. The figure introduces the implementation process of steps 3 and 4. The process starts from obtaining the actual motion parameters obtained by the airborne sensor and the planned motion parameters obtained by calculating the telegram parameters of the planned track, and enters the core loop of motion compensation control. First, the planned motion parameters are compared with the actual motion parameters, and the deviation between the two is calculated to obtain the motion compensation amount of the air-based platform. Then, the calculated motion compensation amount is input into the motion control system to generate the corresponding control law. After the control law is generated, the motion control system outputs the control instruction to drive the actuator (such as thruster, rudder, etc.) to adjust the motion state of the air-based platform in real time, so that it can track the planned track as much as possible and compensate for the navigation telegram error. The adjusted platform motion state will be detected in real time by the airborne sensor to form a new round of feedback information. Next, the algorithm will determine whether the current motion compensation effect reaches the predetermined performance indicators, such as navigation accuracy, tracking error, etc. If the requirements have been met, the control process ends; otherwise, the system will continue to iterate, re-compare motion parameters, calculate compensation amounts, generate control laws, and drive actuators until the ideal compensation effect is achieved.

[0075] In this invention, we propose a method for message error control and platform motion compensation based on air-based navigation sources. The core idea is to use the navigation messages broadcast by the air-based platform itself to perform real-time correction and compensation control on its motion state. However, in actual engineering applications, some alternative technical solutions can also be used according to different mission requirements, environmental conditions and technical means to achieve similar functions and performance.

[0076] In the design of motion compensation control law, the present invention adopts a method based on PID control. As an alternative, predictive control technology can be used. This technology establishes a state space prediction model based on the dynamic model of the air-based platform and the environmental disturbance model to predict the motion state of the platform in the future. The predicted motion state is compared with the planned trajectory, the future motion error is calculated in advance, and the predictive compensation control law is designed to correct the motion of the platform in advance. Compared with feedback control based on the current error, predictive control can improve the dynamic response performance of the system and reduce the tracking error, but it requires a more accurate system model and higher computing power.

[0077] The current motion compensation control of the present invention adopts the traditional PID control method. As an alternative, intelligent control technology can be introduced. This technology uses artificial intelligence methods (such as neural networks, fuzzy logic, reinforcement learning, etc.) to establish a nonlinear mapping relationship between motion errors and compensation control laws. Through offline training or online learning, the parameters or structure of the compensation control law are adaptively adjusted according to the motion state and performance indicators of the platform. Compared with traditional PID control, intelligent control can handle more complex system dynamics and environmental uncertainties and achieve better control performance, but the algorithm design and implementation are more difficult.

[0078] In addition, the present invention only studies the motion compensation problem of a single air-based platform. In the scenario where multiple air-based platforms work together, collaborative control technology can be used as an alternative. This technology uses the relative navigation information between platforms (such as relative position, relative speed, etc.) to design a distributed collaborative control law. Each platform calculates the collaborative compensation control amount based on its own motion state and the state of the adjacent platform, corrects the motion error, and realizes the overall motion optimization of the formation. Compared with single-platform control, collaborative control can improve the robustness and fault tolerance of navigation and achieve higher-level task collaboration, but it requires a reliable platform-to-platform communication and information sharing mechanism.

[0079] In summary, the core framework of the present invention has good scalability and can flexibly introduce various advanced algorithms and technologies to further improve the performance and effect of navigation message error-assisted air-based platform motion control compensation. The selection of these alternative solutions requires comprehensive consideration of system requirements, computing resources, costs and other factors to weigh and arrive at the optimal design.

[0080] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for message error control and platform motion compensation based on airborne navigation source, characterized in that: The steps include: Step 1: Calculate the message parameters of the planned flight path: Generate the corresponding navigation message parameters from the flight path information according to the planned flight path; Step 2: Calculate the planned motion parameters of the air-based platform based on the navigation message parameters to obtain the position, velocity and acceleration information of the platform under the ideal state; obtain the actual motion parameters of the air-based platform in real time through the onboard motion sensor; Step 3: Compare the planned motion parameters of the air-based platform with the actual motion parameters, calculate the deviation between the two, and obtain the motion compensation amount of the air-based platform; Step 4: Input the calculated motion compensation amount into the motion control system, generate corresponding control instructions, drive the actuator to adjust the motion state of the air-based platform in real time, and compensate for the navigation message error; The step 1 comprises: The relationship between the geographic coordinates, the semi-major axis distance, the orbital inclination, and the longitude of the ascending node is set as follows: ， Where B, L, and A represent the latitude and longitude of the space-based platform in the ground-fixed rectangular coordinate system and the radius of curvature of the umbral circle of the reference ellipsoid, respectively. represents the orbital inclination, represents the longitude of the ascending node of the imaginary orbit where the platform is located, Indicates the distance of the major axis among the six elements of the navigation satellite orbit; The step 2 comprises: Step 2.1, calculating the planned motion parameters of the air-based platform; constraining the planned motion parameters of the air-based platform with the major axis change rate, the ascending node longitude change rate, and the orbit inclination change rate in the planned track message parameters, a set of complete planned track message parameters corresponding to determine a unique planned motion parameter of the air-based platform, the platform motion parameters include speed, acceleration, and jerk; Step 2.2, the motion sensor obtains the current motion parameters; the high-precision motion sensors equipped on the air-based platform include: one or more of an inertial measurement unit, a barometric altimeter, and a GNSS receiver. The motion sensor collects data at a certain frequency and sends the collected data to the motion control system for processing.

2. The method for message error control and platform motion compensation based on airborne navigation source according to claim 1, characterized in that: The step 3 comprises: Define the planned motion parameters as the desired state vector : ， in, are the components of the desired position in the X, Y, and Z directions, respectively. are the expected velocity components, are the expected acceleration components respectively, and the superscript T represents the transpose of the matrix; ， In the formula, Indicates reference point The X-coordinate component of the Earth-fixed rectangular coordinate system is, They respectively represent the length of the major semi-axis, latitude and longitude of the reference point where the space-based platform is located at the time of message broadcasting in the ground-fixed rectangular coordinate system, , , They represent the velocity, acceleration, and jerk of the airborne platform in the X-axis direction in the ground-fixed rectangular coordinate system. represents the time difference between the current time and the reference time, t represents the current time, Indicates the reference time. Based on the same operation, the velocity, acceleration, and jerk of the airborne platform in the Y and Z axis directions in the ground-fixed rectangular coordinate system are obtained. Finally, the actual motion parameters are expressed as the state vector : ， in, are the actual position components, are the actual velocity components, are the actual acceleration components respectively; Calculate the deviation between the actual state and the expected state : 。 3. The method for message error control and platform motion compensation based on airborne navigation source according to claim 2, characterized in that: In step 4, the motion control system is the core component of the air-based platform, which is responsible for real-time compensation control of the motion of the air-based platform according to the planned track, message adaptation information and motion sensor feedback. The motion control system includes a motion compensation control law design module, which is used to calculate the deviation between the actual state and the expected state calculated in step 3. , design and generate real-time motion compensation control law. The specific design process is as follows: Select control variables: According to the motion characteristics and control objectives of the air-based platform, select control variables, including position, velocity, and acceleration components in the three directions of X, Y, and Z in the ground-fixed rectangular coordinates; Design compensation control law: Design compensation control law for the selected control variable , using the deviation between the actual state and the expected state Adjust each actual motion parameter: ， in, , , are proportional, integral, and differential gain matrices respectively, represents the time variable used for integration; The compensated motion state As a control instruction, it is input into the motion control system to directly drive the actuator to change the actual movement of the air-based platform.

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