Air floating satellite attitude control demonstration system and control method thereof

Abstract

The application discloses a kind of air float satellite attitude control demonstration system and its control method, the system includes main structure part and air float simulation structure part, main structure part is divided into three layers structure arrangement actuator, power supply module, attitude measurement module, control module, solar panel;Air float simulation structure part includes spherical shell, air float platform, counterweight and air pump.The application adopts full physical entity simulation, and the attitude deviation oscillation that satellite in-orbit weightlessness environment possibly appears is reproduced truly, can realize the unfolding and retraction of solar panel, while maintaining the stability of attitude.Structure is intuitive, clear and easy to understand, suitable as teaching demonstration device.Function modularization is easy to disassemble and replace.Layered structure divides each main function, and the division of labor is clear, with good universality, can be adapted to different accessories for testing.Beneficial to student understanding different accessory purposes, different standard accessories can be replaced according to target requirement.

Description

Technical Field

[0001] This invention relates to the field of embedded system measurement and control technology, specifically to a teaching demonstration system and its control method for satellite attitude measurement and control in a spherical space. Background Technology

[0002] How satellites adjust their attitude control in the weightless environment of space is a key technical issue in aerospace engineering. However, there are still some gaps in teaching demonstrations addressing this issue. Purely theoretical teaching can deeply explain the control mechanism, but it lacks physical demonstrations and is not very intuitive. Using animation to demonstrate satellite attitude changes can fully show the process, but it lacks immersion and interaction with the real physical environment. It is now possible to explore a full physical simulation teaching demonstration of satellite attitude control in weightlessness to improve teaching effectiveness, stimulate students' interest in designing simulated satellites, and encourage them to actively pay attention to related aerospace engineering projects.

[0003] Currently, there are quite a few full-physical simulation demonstration systems for satellite weightlessness attitude. However, most of these large-scale devices are used for scientific research purposes, providing preliminary verification for physical satellites that are about to be put into use. These systems are sophisticated and complex. Some smaller devices focus on multi-degree-of-freedom, large-angle adjustable, and attitude reproduction, but do not focus on demonstrating attitude adjustment methods. Neither of these are suitable for teaching demonstrations.

[0004] Publication No. CN114625027A discloses a multi-spacecraft attitude and orbit control ground-based full-physical simulation system based on a multi-degree-of-freedom motion simulator, belonging to the field of spacecraft ground simulation testing. It employs a dynamics simulator to simulate the orbital / attitude dynamics of two satellites in real time. A relative navigation system is used to sense the relative motion state of the two satellites and to perform navigation calculations based on the sensing results. A wireless data transmission system enables data interaction between the on-board and off-board systems. A visual demonstration system uses specialized software to simulate the real-time operating conditions of the motion simulator. This invention uses two dumbbell-shaped air-bearing platforms to simulate the attitude motion of the tracking and target satellites, thereby achieving motion simulation with two degrees of freedom in the plane and three degrees of freedom in attitude, achieving high-precision simulation and providing a reliable platform for verifying small satellite escort control schemes.

[0005] The technical solution of this invention has the following problems:

[0006] 1. This technical solution focuses on simulating high-precision relative motion and coordinated control of two satellites in orbit.

[0007] 2. This technical solution includes 6 orthogonal reaction wheels and 4 propulsion fans, and simultaneously simulates the rotation of a satellite in orbit and the translation of a relatively moving air-bearing platform, making it more complex and resulting in excess demand.

[0008] 3. The ground control terminal of this technical solution includes a dynamics simulator, a navigation computer, a ground integrated monitoring system, and a visual demonstration system, which is too large and complex and is clearly unsuitable for teaching and demonstration purposes.

[0009] CN117163329A discloses a CubeSat attitude measurement and control simulation device based on a transparent air-floating sphere, belonging to the field of aerospace simulation. The device includes an air-floating mechanism, an air-floating platform, and a control mechanism. The air-floating mechanism includes an air-floating sphere with a clamping assembly inside, which holds the CubeSat. The clamping assembly includes a telescopic rod and a clamping claw, and an adjustment component inside for adjusting the center of mass of the air-floating mechanism. The air-floating platform includes a base and a spherical bowl mounted on the base. An air-floating port is located at the bottom of the spherical bowl, and an air valve is located on the base. The air-floating port communicates with the air valve, and an air compressor provides airflow to suspend the air-floating sphere placed on the spherical bowl. The control mechanism acquires simulation data of the CubeSat and controls the adjustment component. This invention, by placing the CubeSat inside the air-floating sphere and suspending it with the sphere, enables the CubeSat to achieve three degrees of freedom rotation in a microgravity environment, effectively meeting the requirements of satellite attitude control simulation.

[0010] The technical solution of this invention has the following problems:

[0011] 1. This technical solution uses the movement of internal guide rails to change the position of the sphere's center of gravity to achieve attitude change. It can only achieve attitude control in a simulated environment on the ground, which is inconsistent with actual satellite control and cannot meet the needs of control teaching.

[0012] 2. This technical solution cannot realize the measurement feedback display of the current attitude data. It can be used for attitude demonstration, but it lacks the data required for control.

[0013] 3. This technical solution is primarily designed for science popularization and demonstration purposes and cannot meet the teaching simulation needs of students in related majors.

[0014] The invention disclosed in publication number CN113359790A presents a full-physical simulation verification system based on the CMG satellite attitude control algorithm. This full-physical simulation verification system includes: a simulated satellite control system, used to simulate the real-world operation of a satellite control system in orbit; and a ground testing system, which wirelessly transmits information to the simulated satellite control system via a wireless communication device, realizing the functions of telemetry data downlink and control commands, simulating communication between the on-board antenna and the ground radar. This invention has the following problems:

[0015] 1. The ground testing system of this technical solution includes an air-bearing platform for angle measurement, leveling and control computer, remote control unit, database, display terminal, network switch and wireless communication device, focusing on the simulation of remote wireless communication.

[0016] 2. A fiber optic gyroscope assembly is required as a navigation subsystem.

[0017] 3. The technical solution of this invention focuses on the scheme planning of the full physical simulation system, but does not provide a suitable physical construction. Summary of the Invention

[0018] Purpose of the invention: To address the shortcomings of existing technologies, the purpose of this invention is to provide an air-floating satellite attitude control demonstration system. This system uses an air-floating hemispherical platform to create a weightless environment for the satellite, and constructs a satellite attitude measurement and control system within the hemispherical space to achieve convenient, fast, and accurate satellite attitude adjustment. It is suitable for teaching demonstration scenarios.

[0019] The present invention also provides a corresponding control method, which measures the satellite attitude and controls the changes in the satellite attitude, thereby controlling the satellite to adjust to any set attitude; and can maintain the attitude stability to demonstrate the unfolding and retraction of foldable solar panels.

[0020] Technical Solution: To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0021] A demonstration system for attitude control of an air-floating satellite includes a main structure and an air-floating simulation structure. The main structure is divided into three layers, separated by two disks. The bottom layer is an actuator that drives the satellite to rotate along the z-axis, located at the center of the disk. The middle layer consists of two orthogonally arranged actuators that drive the satellite to rotate along the x and y axes, and a power supply module. The top layer includes an attitude measurement module, a control module, a communication module, and a solar panel. The attitude measurement module is responsible for measuring the device's attitude data. The control module is used for target attitude calculation, controlling the actuators to perform actions, controlling the deployment and retraction of the solar panel, and controlling the communication transmission between the device and the host computer. The solar panel is a foldable solar panel. The communication module uses Bluetooth communication to interact with the host computer and transmit data, including status parameter feedback and control command issuance.

[0022] The air-float simulation structure includes a spherical shell, an air-float platform, a counterweight, and an air pump. The main structure is housed inside the spherical shell. The air-float platform is a triaxial air-float platform supported by spherical air bearings, forming a spherical air film to create a simulated weightless environment. The counterweight is adhesive and is attached to a support structure that does not affect operation after the air pump is turned on, depending on the device's orientation. It is used to adjust the device's center of gravity so that it is located at the center of the sphere.

[0023] When the air-floating satellite attitude control demonstration system is working, the attitude measurement module measures the attitude data of the device, the communication module sends the measurement data to the host computer, the communication module receives the host computer's control commands, the control module calculates the target angle based on the host computer's control commands and the measured attitude data, and sends control commands to the actuator. The actuator drives the device to adjust the posture to achieve the target angle, and the control module controls the deployment and retraction of the solar panels to realize the teaching demonstration.

[0024] The control method of the air-bearing satellite attitude control demonstration system includes the following steps:

[0025] First, turn on the power and check the connection between the communication module and the host computer system;

[0026] The second step is to turn off the power after confirming a normal communication connection, place the main structure inside the hemispherical shell on the air-floating platform, turn on the air pump, and observe the attitude of the device. To demonstrate the deployment and retraction of the solar panels, simply observe whether the device is level. To demonstrate full-angle adjustment, remove the solar panels, cover them with the upper hemispherical shell, and check whether the device can maintain the angle after rotating at any angle. If not, adjust the counterweights to make the system's center of gravity meet the requirements.

[0027] Third, turn on the power. After the communication connection is successful, the attitude data is fed back to the host computer interface. At this time, input the target angle data, and the satellite can adjust to the target angle.

[0028] The fourth step is to send a pre-set command after the satellite has reached the target angle and its attitude is stable, so as to deploy the solar panels and realize the demonstration. The same applies to retracting them.

[0029] Beneficial Effects: This invention discloses an air-floating satellite attitude control demonstration system and its control method. Its main purpose is to simulate the weightlessness of a satellite in space and demonstrate basic attitude recovery and adjustment functions. The system includes an air-floating simulation structure and the main structure serving as the attitude control system. The air-floating simulation structure consists of a spherical structure simulating a satellite, an air-floating platform providing the simulation environment, and an external air pump system. The attitude control system is installed inside the spherical shell and is designed as a three-layer structure, including three motors, three flywheels, a battery, an inertial measurement unit, a control circuit board, an H-bridge drive, a Bluetooth module, and a counterweight. This air-floating satellite attitude control demonstration system can simulate the weightless suspension state of a satellite, measure the satellite's attitude data in real time and display it on a host computer, and control the satellite's attitude to overcome external disturbances and maintain a horizontal position or adjust to a preset angle, achieving stable deployment and retraction of solar panels. Compared to other similar devices currently available, this system has a more intuitive, clear, and easy-to-understand structure, making it suitable as a teaching demonstration device. It adopts a modular design for easy disassembly and replacement. The layered structure clearly defines the functions of each main component, providing good versatility and allowing for testing with different accessories. It helps students understand the uses of different accessories and allows them to replace different standard accessories according to different target needs. Attached Figure Description

[0030] Figure 1 This is an overall rendering of the device;

[0031] Figure 2 This is a diagram of the lower layer structure of the device;

[0032] Figure 3 This is a diagram of the middle layer structure of the device;

[0033] Figure 4 This is a structural diagram of the main device;

[0034] Figure 5 , Figure 6 , Figure 7 These are the front view, top view, and left view of the main device, respectively.

[0035] Figure 8 This is a diagram showing the connection relationships between the various modules of the device;

[0036] Figure 9 This is the circuit schematic of the transformer module;

[0037] Figure 10 This is a diagram illustrating the functionality of the Topic function;

[0038] Figure 11 This is a schematic diagram of the air flotation principle;

[0039] Figure 12 This is a PID control structure diagram;

[0040] Figure 13 It is a structural diagram that can be adjusted at all angles;

[0041] Figure 14 This is an illustration of what it looks like when the solar panels are retracted. Detailed Implementation

[0042] To provide a clearer understanding of the features and advantages of the technical solution of the present invention, the composition and implementation of the specific solution are described below in conjunction with the accompanying drawings.

[0043] Attitude control studies the attitude motion of a satellite rotating around its center of mass. By applying a rotational torque around the center of mass, the satellite's position in space can be maintained or changed as needed. The tasks of an attitude control system include attitude determination and attitude control.

[0044] Early development of single-satellite systems primarily focused on momentum satellites (such as spin satellites, dual-spin satellites, and satellites with biased momentum flywheels). These satellites utilize the gyroscopic stability generated by rotation around their spin axis to maintain the satellite's spin axis's orientation relative to inertial space. Other methods included jet control, nutation dampers, or solar radiation pressure control, but these methods had lower accuracy and were mainly used for space physics exploration. Later, zero-momentum satellites emerged. Based on the actuator configuration, their attitude stabilization control can be divided into fully driven and underdriven types. For a three-axis stabilized spacecraft, an attitude control system with actuators (momentum exchange devices or thrusters) in all three axes constitutes a fully driven system, where the dimension of the system's configuration space is the same as the dimension of its control input. An underdriven system is one where the dimension of the control input is lower than the dimension of its configuration space.

[0045] Generally speaking, the hardware of a satellite attitude control system consists of three parts: attitude sensor, controller, and actuator, while the software includes the algorithms required for measurement information processing and control logic formation.

[0046] In practice, attitude determination systems on satellites are typically composed of a combination of gyroscopes, star sensors, infrared horizon sensors, sun sensors, and magnetometers. These sensors use different reference points, indicating that multiple different types of attitude sensors are generally required for attitude determination. However, this invention operates under ground gravity, thus directly utilizing the accelerometers, gyroscopes, and magnetometers contained within the inertial measurement unit (IMU) to determine attitude information.

[0047] Actuators generally include a flywheel, a jet thruster, and a magnetic torque converter. During steady-state satellite operation, the flywheel is the primary actuator, while the thruster and magnetic torque converter are mainly used for unloading the flywheel, attitude acquisition, or certain attitude maneuvers. Among wheel control methods, the reaction wheel control method has the highest accuracy, followed by the bias momentum wheel control method. This invention uses a three-orthogonal reaction flywheel as the actuator.

[0048] Attitude calculation based on IMU. The attitude matrix provides the data needed for calculating the vehicle's attitude and navigation parameters. The vehicle's attitude and heading reflect the orientation relationship between the vehicle coordinate system and the navigation coordinate system. Determining the orientation relationship between the two coordinate systems requires the use of matrix methods and the displacement theorem for rigid body motion at a fixed point in mechanics. The direction cosine table is derived using the matrix method, and the displacement theorem for rigid body motion at a fixed point shows that any finite displacement of a rigid body in fixed-point motion can be achieved through a single rotation around an axis at the fixed point. This invention uses the quaternion method to describe the orientation relationship of the moving coordinate system relative to the reference coordinate system.

[0049] Simulation applies similarity theorems and analogies to study phenomena, essentially using models to replace actual systems for experiments and research. Air-bearing platforms, as a simulation method for satellite attitude control systems, emerged almost simultaneously with satellite development. For example, the early US Thales satellite used air-bearing platforms for nutation damping tests; in early 1968, my country used a three-axis air-bearing platform for antenna extension tests on the Dongfanghong-1 satellite. By simulating a weightless environment with an air-bearing platform, the satellite's control system is composed of some or all physical components, forming a simulation loop identical to the actual situation, using actual control laws and operating software. In this way, simulation can more realistically simulate the satellite's dynamics, momentum exchange, momentum coupling, and identify potential problems in the actual model. This invention uses a three-axis air-bearing platform to achieve the greatest possible reproduction of a weightless environment.

[0050] (I) System Structure

[0051] This invention provides a demonstration system for attitude control of an air-floating satellite, the system consisting of a main structure and an air-floating simulation structure. (Refer to...) Figures 1-7 The main structure 3 is a three-layer structure. The bottom layer consists of a flywheel 5, a motor 4, and their fixing structure along the z-axis, placed at the center of the disk. The middle layer consists of orthogonally placed and fixed motors 7 and flywheels 8 along the x and y axes, as well as a battery structure 6. The upper layer contains an inertial measurement unit 9, a control module 10, and a solar panel 11. The air-floating simulation structure consists of two spherical shells 2 and an air-floating platform 1 that provides the simulation environment. The entire system places the main structure within the hemispherical shells, as shown in the diagram. Figure 1 As shown, the external PC control terminal is connected to the structure via a Bluetooth module.

[0052] In this invention, the control module uses an STM32F407 development board, where the main functions such as attitude algorithm execution and information transmission and processing are performed. The development board has multiple built-in sensors, including an accelerometer for detecting the device's acceleration. It also includes a temperature sensor and a pressure sensor for measuring ambient temperature and air pressure. These built-in sensors can, on the one hand, simulate satellite data to obtain the device's current operating environment parameters, providing real-time feedback for troubleshooting; on the other hand, they can provide some data support if other satellite functions are added later.

[0053] The measurement module uses an inertial measurement unit (IMU), which includes accelerometers, gyroscopes, magnetometers, and other components, and is responsible for measuring attitude data.

[0054] The Bluetooth transmission module and its corresponding communication host computer control interface are responsible for the communication connection between the satellite device and the computer, including status parameter feedback and control command issuance.

[0055] The actuators include an H-bridge motor drive module as the speed and direction controller for the motor; a motor as the attitude control actuator for the satellite system; and a flywheel as the main angular momentum exchange structure, generating reaction force. The flywheel is directly driven by its corresponding motor, and the angle information of the x, y, and z axes is measured by the inertial measurement unit and transmitted to the motor-flywheel actuators of each of the three axes to complete the attitude control of their respective axes.

[0056] The power supply module includes a rechargeable battery and two transformer circuits adapted to each component to provide the appropriate power supply voltage.

[0057] The air-bearing simulation structure is a fully physical simulation module, comprising a spherical shell, an air-bearing platform, counterweights, and an air pump, creating a simulated weightless environment with virtually no friction or disturbance torque. The counterweight adjustment device centers the gravity at the center of the sphere, ensuring consistent gravity for the satellite at any angle and preventing additional oscillations caused by gravity shifts during attitude adjustments. The three-axis air-bearing platform, supported by spherical air bearings, relies on a spherical air film to reduce friction, providing the required attitude movement range in all three axes and simulating the satellite's three-axis coupled dynamics, such as… Figure 11 As shown. The counterweight is adhesive; after turning on the air pump, it is attached to a supporting structure that does not interfere with the operation, depending on the orientation of the device.

[0058] The solar panel is a foldable solar panel, and its folding and unfolding are directly controlled by the control module.

[0059] The system adopts a layered modular design, and different standard components can be replaced according to different target requirements. For example, to realize the optical observation function, the development board with a camera can be replaced as the control center module, and to simulate the attitude determination of on-orbit satellites, the measurement module can be replaced with a gyroscope, magnetometer, etc.

[0060] According to such Figure 8 The module wiring is completed as shown. Figure 8 The solid lines represent wired connections, while the dashed lines represent wireless transmission. The computer uses host computer software to wirelessly communicate with the STM32 development board via Bluetooth, enabling feedback of status parameters and issuance of control commands. Simultaneously, the Bluetooth module, inertial measurement unit, H-bridge drive module, and X and Y axis motors are directly connected to the development board for signal transmission. An 11V battery power supply is provided... Figure 9 The transformer module shown supplies power to the latter four components. In this invention, the Z-axis motor 4 requires an H-bridge module for driving, while the X and Y-axis motors 7 can be directly controlled by an STM32 development board. The H-bridge drive module is used for motor direction and speed control. The Z-axis direction is the main attitude control direction; since a high-power motor is selected, it is connected to an H-bridge module as the driver. The X and Y-axis directions use lower-power motors, which have built-in H-bridge drivers, so no external H-bridge is needed. In practical scenarios, the need for an external H-bridge module can be determined based on the motor's operating requirements.

[0061] (II) Software Structure

[0062] It employs a real-time parallel processing system designed for embedded development, offering a high degree of flexibility. Its main advantage lies in providing functions for multi-threaded execution and efficient data management. When multiple tasks run concurrently with different time constraints and priorities, the system provides a multi-threaded execution method. Each thread has a corresponding priority, allowing it to be suspended when necessary and resumed when needed. The system also provides convenient data management functions: Topic and Subscriber. Figure 10 Each line represents a user-defined Topic. Users can store useful data in the corresponding Topic, and when they need the data, they simply subscribe to the corresponding Topic using a Subscriber to retrieve it. The advantage of this method is clear data management. During attitude calculation, the computation, publication, and transmission of different parameters are processed in parallel without interference. In this invention, satellite attitude adjustment utilizes a real-time parallel processing system function library based on the C++ language environment. The IMUThread function for inertial measurement unit data reading, and the topic and subscribe functions for data uploading and acquisition are written.

[0063] (III) System Control Principles

[0064] (1) Attitude calculation

[0065] The motherboard accumulates measurements from the accelerometer, gyroscope, and magnetometer. Once a certain number of measurements are collected, the average value is calculated, and the initial Euler angle quaternion and other parameters are then determined.

[0066] Let α, β, and γ be the roll, pitch, and yaw angles of the inertial measurement unit coordinate system relative to the ground reference coordinate system, respectively. The quaternions q0, q1, q2, and q3 can then be calculated using the formula below, with q representing a vector composed of these four quaternions.

[0067]

[0068]

[0069] in, , , The accelerometer measures the acceleration along the xyz axes. , These are the magnetometer readings measured on the y-axis and z-axis.

[0070] The covariance matrix P_q of the quaternions, the error covariance matrix var of the attitude information source, and the initial quaternion covariance matrix are calculated using the Jacobian matrix of the quaternions. These different covariance matrices are used to evaluate the system's performance and the degree to which the predictive model can be trusted. According to the coordinate system convention in the filter, the gyroscope measurements are transformed from the sensor coordinate system to the body coordinate system. The time step dt is calculated, and by calculating the difference between the current time and the previous update time, the angular velocity W in the state matrix X is updated using the following formula. b Quaternion q and gyroscope zero-bias estimate X gk .

[0071]

[0072]

[0073]

[0074] Among them, gyro x (k) is the measurement value of the gyroscope on the x-axis at the k-th step, w bx It is the angular velocity W b The component on the x-axis, x gx (k) is the zero-biased estimate X at the k-th step. gk The components on the x-axis have similar meanings to the corresponding parameters on the y and z axes, and λ is the weighting coefficient.

[0075] Normalize the quaternion by dividing it by its modulus to ensure that it meets the requirements of a unit quaternion.

[0076] Update the state covariance matrix P by propagating the covariance according to the following formula:

[0077]

[0078] Where F is the discrete one-step transition matrix and FuF is the system noise matrix. Let be the transpose function. To ensure that the covariance matrix P remains symmetric, add P and its transpose matrix and then divide by 2.

[0079]

[0080]

[0081]

[0082]

[0083]

[0084] The Jacobian matrix h1 updated by the acceleration measurement is calculated using the formula above. This matrix describes the impact of acceleration measurement error on the state vector. The process covariance matrix S1 is obtained by multiplying the Jacobian matrix by the state covariance matrix P and adding the acceleration measurement noise covariance matrix R1. Then, the Kalman gain W1 and the updated state vector X are derived. The state vector X is corrected using the acceleration measurement values ​​through the above steps. Subsequent steps are similar. By processing the magnetometer values, the estimated azimuth angle and body attitude changes are calculated and added to X (updating the state vector X) to update the state of the Kalman filter. Finally, the optimal estimated quaternion values ​​and rotational velocity state are obtained.

[0085] (2) PID control

[0086] Let ω be the angular velocity of the celestial body, and the angular velocity of the flywheel relative to the celestial body be... , Let O be the total moment of inertia of the celestial body and the flywheel about point O, and let O be the moment of inertia of the celestial body. , Let be the moment of inertia of the flywheel relative to the center of mass of the satellite, where

[0087]

[0088] in, These are the moments of inertia of the flywheel relative to the x, y, and z axes, respectively.

[0089] The total angular momentum of the celestial body and the flywheel is as follows: angular momentum of the celestial body (excluding the flywheel). With flywheel angular momentum sum:

[0090]

[0091] Differentiating the above equation, we can obtain the following from the theorem of angular momentum:

[0092]

[0093] Right now:

[0094]

[0095] in: The control torque of the motor on the flywheel shaft. The external torque is given by the above equation, which is the satellite attitude dynamics model with three orthogonal reaction flywheels as actuators.

[0096] The device is controlled as follows Figure 12 A dual-loop PID control is employed. The PID algorithm can be expressed by the following formula:

[0097]

[0098] Where u(t) is the control input, e(t) is the error, and t is the time. These are control parameters.

[0099] This device uses a two-layer PID controller to control the motor speed, thereby achieving attitude adjustment. The outer controller calculates the error based on the satellite's target attitude and current attitude, and then outputs a control signal using a PID algorithm; this signal represents the target motor speed. The inner controller calculates the error based on encoder measurements and the outer controller's output, and then outputs a control signal using a PID algorithm; this signal represents the motor's drive voltage. Thus, through this two-layer PID controller, users can achieve precise control of the satellite's attitude.

[0100] The speed loop and angle loop each have corresponding control parameters. Adjusting these parameters can change the speed of response and the intensity of oscillation. If the system has been reconfigured, or if the device's angle and attitude are not ideal, the PID control parameters can be readjusted (generally, adjusting these parameters should be the first priority). ,back , Prioritize adjusting the three parameters of the speed control loop to achieve a fast but very small overshoot. Next, adjust the angle control loop to achieve a slow but overshoot-free response. The x, y, and z axes each have their own set PID control parameters. Generally, adjusting the z-axis PID control parameters will improve the angle; unless necessary, do not modify the x and y axis parameters.

[0101] In this invention, satellite attitude adjustment utilizes a real-time parallel processing system function library based on the C++ language environment. Three-axis corresponding code for dual-loop PID control was written, along with a wireless parameter tuning host computer program that interfaces with Bluetooth. When a module is replaced or the angle and attitude are unsatisfactory, the host computer software can be used to feed back attitude data in real time and plot response curves to readjust the PID control parameters.

[0102] (3) Communication between host computer and Bluetooth

[0103] For Bluetooth communication of this device, to give instructions, input a command like "$a%f#$b%f#$c%f#" into the host interface and send it to the microcontroller. Alternatively, you can directly enter the desired system parameters such as KP / KI / KD or the target angle / position in the preset parameter fields, and send the settings all at once to achieve Bluetooth parameter tuning and attitude adjustment. When the host computer receives a data packet like "$%s, %s, %s, %s, %s#\n", it unpacks it to obtain different data variables, which are displayed on the host computer software interface. The interface includes a visual display of acceleration, magnetic force, angular velocity, attitude, and temperature, and the data is simultaneously saved to an Excel spreadsheet, including the above variables, the current time, and the number of transmissions.

[0104] (iv) System operation procedure

[0105] First, turn on the power and check the Bluetooth connection with the host computer system.

[0106] The second step, after confirming Bluetooth connectivity, is to turn off the power and place the main unit inside the hemispherical shell on the air-floating platform, then turn on the air pump. Observe the device's attitude. To demonstrate the deployment and retraction of the solar panel, simply observe whether the device is horizontal (i.e., the system's center of gravity is located in the lower half of the central axis). To demonstrate full-angle adjustment, the solar panel needs to be removed, and the upper hemispherical shell should be replaced as shown. Figure 13 As shown, check whether the device can maintain the angle after rotating at any angle (i.e., the system's center of gravity coincides with the center of the ball). If it does not meet the requirement, the counterweights should be adjusted to make the system's center of gravity meet the requirement.

[0107] The third step is to turn on the power. After the Bluetooth connection is successful, the attitude data is fed back to the host computer interface. At this time, you can input the target angle data, and the satellite can be adjusted to the target angle. (Note that after the solar panels are installed, the device cannot achieve full-angle rotation. Avoid excessive pitch and yaw angle adjustments.)

[0108] Fourth, once the satellite has reached the target angle and its attitude is stable, a pre-set command can be sent to deploy the solar panels, thus completing the demonstration. Deploying them is similar. The solar panels retract as follows: Figure 14 As shown.

[0109] The air-bearing satellite attitude control demonstration system provided by this invention has a simple physical structure and employs full physical entity simulation to realistically reproduce the attitude deviation and oscillations that a satellite may experience in a weightless environment in orbit. It can deploy and retract solar panels while maintaining attitude stability. The structure is intuitive, clear, and easy to understand, making it suitable as a teaching demonstration device. Its modular design allows for easy disassembly and replacement. The layered structure clearly defines the functions of each major component, providing good versatility and allowing for testing with different accessories. This facilitates students' understanding of the uses of different accessories, and different standard accessories can be replaced according to different target requirements.

Claims

1. A demonstration system for attitude control of an air-floating satellite, characterized in that, It includes a main structure and an air-floating simulation structure. The main structure is divided into three layers, separated by two disks. The bottom layer is the actuator that drives the satellite to rotate along the z-axis, which is located at the center of the disk. The middle layer consists of two actuators and a power supply module that are orthogonally arranged to drive the satellite to rotate along the x and y axes. The upper layer consists of an attitude measurement module, a control module, a communication module, and a solar panel. The attitude measurement module is responsible for measuring the device's attitude data. The control module is used to calculate the target attitude, control the actuators to perform actions, control the solar panel to unfold and retract, and control the communication transmission between the device and the host computer. The solar panel is a foldable solar panel. The communication module uses Bluetooth communication to interact with the host computer and transmit data, including status parameter feedback and control command issuance. The actuator includes a motor, a bridge drive circuit, and a flywheel. The bridge drive circuit serves as the speed and direction control device for the motor; the motor serves as the attitude control actuator for the satellite system; the flywheel serves as the main angular momentum exchange structure, generating a reaction force; the flywheel is directly driven by the corresponding motor, and the angle information of the x, y, and z axes is measured by the inertial measurement unit and transmitted to the motor and flywheel actuators of the three axes respectively to complete the attitude control of their respective axes. The air-float simulation structure includes a spherical shell, an air-float platform, a counterweight, and an air pump. The main structure is housed inside the spherical shell. The air-float platform is a triaxial air-float platform supported by spherical air bearings, forming a spherical air film to create a simulated weightless environment. The counterweight is adhesive and is attached to a support structure that does not affect operation after the air pump is turned on, depending on the device's orientation. It is used to adjust the device's center of gravity so that it is located at the center of the sphere. When the air-floating satellite attitude control demonstration system is working, the attitude measurement module measures the attitude data of the device, the communication module sends the measurement data to the host computer, the communication module receives the host computer's control commands, the control module calculates the target angle based on the host computer's control commands and the measured attitude data, and sends control commands to the actuator. The actuator drives the device to adjust the posture to achieve the target angle, and the control module controls the deployment and retraction of the solar panels to realize the teaching demonstration.

2. The air-bearing satellite attitude control demonstration system according to claim 1, characterized in that, The three actuators form an orthogonal structure, and the attitude dynamics model of the satellite system is as follows: Let ω be the angular velocity of the celestial body, and the angular velocity of the flywheel relative to the celestial body be... , Let O be the total moment of inertia of the celestial body and the flywheel about point O, and let O be the moment of inertia of the celestial body. , Let be the moment of inertia of the flywheel relative to the center of mass of the celestial body. Then the total angular momentum of the celestial body and the flywheel is: The angular momentum of the celestial body excluding the flywheel component. For the angular momentum of the flywheel, differentiating the above equation, we get the following from the angular momentum theorem: That is: in: The control torque of the motor on the flywheel shaft. As the external torque, the above equation is the satellite attitude dynamics model with three orthogonal reaction flywheels as actuators.

3. The air-bearing satellite attitude control demonstration system according to claim 2, characterized in that, The satellite attitude adjustment adopts dual-loop PID control, which consists of a position loop PID and a velocity loop PID. The control method is as follows: the motor is initialized to record the initial attitude position and attitude changes are detected in real time. When an attitude change is detected, the change in angle is recorded, and the difference required to be changed is used as the change in velocity. The position loop PID calculates the required angle change for each axis and outputs it to the velocity loop PID control. The velocity loop PID control outputs a control voltage signal to the bridge drive circuit according to the voltage required for different speed accelerations, thereby controlling the accelerated rotation of the motor to adjust the attitude. In the control module, the satellite attitude adjustment control system adopts a real-time parallel processing system function library based on the C++ language environment, and writes the three-axis corresponding code for dual-loop PID control, as well as the host computer program for wireless parameter tuning that interfaces with the communication module.

4. The air-bearing satellite attitude control demonstration system according to claim 3, characterized in that, When a module in the demonstration system is replaced or the angle and posture are not ideal, the system supports using the host computer software to feed back the posture data in real time and draw the response curve to readjust the PID control parameters.

5. The air-bearing satellite attitude control demonstration system according to claim 1, characterized in that, The attitude measurement module uses an inertial measurement unit, including an accelerometer, a gyroscope, and a magnetometer. When the control module performs attitude calculation, it accumulates the measurement values ​​of the accelerometer, gyroscope, and magnetometer. After reaching a specified number, it obtains the average value, thereby calculating the initial Euler angle quaternion parameters. According to the coordinate system convention in the filter, the gyroscope measurement value is transformed from the sensor coordinate system to the body coordinate system, the time step dt is calculated, and the quaternion, angular velocity and gyroscope zero bias estimate in the state matrix X are updated by calculating the difference between the current time and the last update time. Update the state covariance matrix P and propagate the covariance. Calculate the Jacobian matrix h1 updated by acceleration measurement, obtain the process covariance matrix S1 by multiplying the Jacobian matrix with the state covariance matrix P and adding the acceleration measurement noise covariance matrix R1, and then obtain the Kalman gain W1 and the updated state vector. By processing the magnetometer values, the estimated changes in azimuth and body posture are calculated and added to the updated state vector to update the state of the Kalman filter, ultimately obtaining the optimal estimated quaternion values ​​and rotational velocity state.

6. The air-bearing satellite attitude control demonstration system according to claim 5, characterized in that, In the control module, the satellite attitude calculation system adopts a real-time parallel processing system function library based on the C++ language environment. The IMUThread function for reading inertial measurement unit data, the topic function for uploading and acquiring data, and the subscribe function are written. The topic function is used to store user-defined data, and the subscribe function is used to subscribe to the corresponding topic to retrieve the required data.

7. The air-bearing satellite attitude control demonstration system according to claim 1, characterized in that, The control module uses an STM32 development board. The communication module, attitude measurement unit, motor drive circuit, and x and y axis motors are directly connected to the development board to achieve signal transmission.

8. The air-bearing satellite attitude control demonstration system according to claim 7, characterized in that, The development board has a variety of built-in sensors, including an accelerometer for detecting device acceleration, a temperature sensor for measuring ambient temperature, and a pressure sensor for measuring ambient air pressure. The measured working environment parameters are fed back to the host computer in real time, which facilitates troubleshooting.

9. A control method for an air-bearing satellite attitude control demonstration system according to any one of claims 1-8, characterized in that, Includes the following steps: First, turn on the power and check the connection between the communication module and the host computer system; The second step is to turn off the power after confirming a normal communication connection, place the main structure inside the hemispherical shell on the air-floating platform, turn on the air pump, and observe the attitude of the device. To demonstrate the deployment and retraction of the solar panels, simply observe whether the device is level. To demonstrate full-angle adjustment, remove the solar panels, cover them with the upper hemispherical shell, and check whether the device can maintain the angle after rotating at any angle. If not, adjust the counterweights to make the system's center of gravity meet the requirements. Third, turn on the power. After the communication connection is successful, the attitude data is fed back to the host computer interface. At this time, input the target angle data, and the satellite can adjust to the target angle. The fourth step is to send a pre-set command once the satellite has the target angle and its attitude is stable, and then deploy the solar panels to complete the demonstration.

Images