A Ground Simulation Verification Method for Ultra-Quiet Control Systems

Abstract

The application discloses a super-static control system ground simulation verification method, belongs to the super-static control system ground verification field, and has the characteristics that a precise magnetic moment output model of a magnetic torque device is established to obtain high-precision control torque information; a precise accelerometer model is introduced to more objectively and accurately calculate the real angular acceleration of a star; an angular acceleration power spectrum density curve is automatically generated, and the power spectrum density situation at the satellite center of mass can be viewed in real time. The method has the characteristics of independence and does not affect normal ground simulation verification, and the real angular velocity information of an external system is introduced to achieve the advantages of objectivity and accuracy.

Description

Technical Field

[0001] This invention relates to a ground simulation verification method for ultra-quiet control systems, belonging to the field of ground verification of ultra-quiet control systems. Background Technology

[0002] The ultra-quiet control system for small satellites is a control system with extremely low angular acceleration power spectral density. The onboard control system uses vibration-free actuators and typically includes a cold gas propulsion system and a magnetic torquer. In on-orbit scientific observation mode, the cold gas propulsion system is generally inactive, and satellite attitude control is achieved solely through the magnetic torquer.

[0003] The performance of ultra-quiet control systems is typically evaluated using the power spectral density calculated from the angular acceleration output by the accelerometer at the satellite's center of mass; that is, the distribution of the energy of the satellite's rotation due to torque as a function of frequency. Since the magnitudes of both the active control torque and the environmental disturbance torque in ultra-quiet control systems are relatively small, the accuracy of the active control torque signal acquisition and the accuracy of the environmental disturbance torque simulation model significantly impact the accuracy of the ground simulation. Therefore, these two aspects are crucial for evaluating the performance of ultra-quiet control systems. Secondly, because ultra-quiet control systems in scientific observation mode rely heavily on the magnetic torquer for attitude control, the torque experienced by the satellite is relatively singular. Therefore, the accuracy of the magnetic torquer's output model also significantly affects the evaluation performance. During the ground simulation verification of ultra-quiet control systems, the following four problems were encountered:

[0004] First, traditional ground-based simulation systems typically have a simulation cycle of 100ms. This long cycle and slow data iteration result in slow updates of information such as space environment disturbance torques, leading to poor real-time performance.

[0005] Second, the magnetic torque output model of the magnetic torque generator is not accurate enough and differs significantly from the actual product state, making the simulation results inaccurate.

[0006] Third, the angular acceleration at the center of mass of a star obtained by traditional ground simulation experiments does not take into account measurement noise, and the data is not objective and accurate enough.

[0007] Fourth, the data processing formulas are cumbersome, data processing is time-consuming, and real-time performance is poor. Summary of the Invention

[0008] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art, establish an accurate magnetic torque output model for the magnetic torque device, and obtain high-precision control torque information; to calculate the true angular acceleration of the celestial body more objectively and accurately by introducing an accurate accelerometer model; and to automatically generate angular acceleration power spectral density curves, so as to view the power spectral density at the center of mass of the satellite in real time.

[0009] The objective of this invention is achieved through the following technical solutions:

[0010] A ground simulation verification method for an ultra-quiet control system comprises two parts;

[0011] Part One includes:

[0012] The satellite ground simulation test began. After the control system was powered on, the satellite entered normal control mode, and normal data exchange occurred between the satellite and the ground. The exchange process is as follows:

[0013] (i) The satellite control system estimates the satellite attitude and calculates the control amount of the satellite attitude deviation by collecting the output information of the sensor of the ground simulation system. The control command information of the actuator is calculated by the control amount of the satellite attitude deviation. In this method, the actuator specifically refers to the magnetic torque device, and the control command information specifically refers to the control command voltage Mcv.

[0014] (II) The ground simulation system collects control information from the actuators and establishes a magnetic moment output model. The control torque acting on the celestial body is then calculated using the dynamic model of the ground simulation system. The calculation process is as follows:

[0015] ①Establish a magnetic torque output model for the magnetic torque actuator.

[0016] Based on the working principle of the magnetic torquer and its circuitry, the control information acquired by the ground simulation system includes the control command voltage Mcv and the telemetry value of the current TMv in the actual magnetic torquer coil, where TMv is the voltage value and represents the magnetic torque output of the actual magnetic torquer. To accurately reflect the output magnetic torque of the actual magnetic torquer, the following calculations are performed:

[0017] The current telemetry value collected at the beginning of the ground simulation cycle is denoted as TMv0. The current telemetry value TMv1 at the end of the ground simulation cycle is estimated. We can obtain: TMv1=TMv0+Mcv / (Lm×T), where T is the ground simulation cycle and Lm is the equivalent inductance of the magnetic torquer.

[0018] Calculate the average current telemetry value over the simulation period T: TMv01=(TMv0+TMv0) / 2;

[0019] Establish the equation for the output magnetic moment M of the magnetic torque generator with respect to the independent variable TMv01: M=f(TMv01);

[0020] ② Calculation of the control torque on the celestial body:

[0021] The ground simulation system generates a control torque T acting on the celestial body by using the magnetic moment of a magnetic torquer and a model of the Earth's magnetic field. m =[T mx T my T mz ], where T mx T is the control torque generated in the x-axis direction. myT is the control torque generated in the y-axis direction. mz The control torque generated in the z-axis direction is calculated using the following formula:

[0022] T mx =M yb B zb -M zb B yb

[0023] T my =M zb B xb -M xb B zb

[0024] T mz =M xb B yb -M yb B xb …(1)

[0025] Magnetic torque M = [M xb M yb M zb ], where M xb M is the magnetic moment in the x-axis direction. yb M is the magnetic moment in the y-axis direction. zb Let B be the magnetic moment in the z-axis direction, and B = [B xb B yb B zb [ ] represents the components of the geomagnetic field along the three axes of the satellite's main system.

[0026] (III) The ground simulation system calculates the space environment disturbance torque T experienced by the celestial body using orbital information and a space environment torque model. d T d Including satellite gravity gradient moment T dg Aerodynamic torque T da Residual magnetic torque T dm Solar radiation pressure T ds .

[0027] T d =T dg +T da +T dm +T ds …(2)

[0028] (iv) The ground simulation system will control the torque T m And the space environment disturbance torque T d The sum of T is used as input to the satellite dynamics equations to calculate the true attitude information of the satellite at time t and the processed angular acceleration of the satellite's center of mass. The calculation process is as follows:

[0029]

[0030] Let t be the angular acceleration of the satellite's center of mass relative to the inertial coordinate system at time t, expressed in terms of the three-axis components of the roll axis (x), pitch axis (y), and yaw axis (z) of the satellite's own system. Let I be the satellite's moment of inertia. -1 It is the inverse matrix of I.

[0031] (v) An accelerometer model is installed in the ground simulation system. Angular acceleration information is incorporated into the accelerometer model to calculate the true angular acceleration at the center of mass of the celestial body. The steps are as follows:

[0032] ① The accelerometer model in the ground simulation system can be activated via command.

[0033] ② After the accelerometer model is activated, the ground simulation system incorporates the actual angular acceleration at the center of mass of the celestial body, generated by the combined action of the control torque produced by the actuator and the disturbance torque of the space environment, into the accelerometer model:

[0034] y(t)=a(t)+b(t)+η1(t)+f1·a(t)+f2·a 2 (t)…(5)

[0035] In the formula, y(t) is the actual angular acceleration at the center of mass of the celestial body measured and output by the accelerometer; a(t) is the angular velocity information of the celestial body calculated by the ground simulation system, that is, the theoretical angular acceleration calculated in step (iv) of Part I. b(t) is the constant drift of the accelerometer angular acceleration measurement, f1·a(t) and f2·a 2 f(t) represents the linear and nonlinear errors, respectively; f1 and f2 are the coefficients of the known linear and quadratic terms; η1(t) is an approximation of a three-dimensional Gaussian white noise vector.

[0036] The accelerometer model built in the ground simulation system was used to obtain the objective and real angular acceleration y(t) at the center of mass of the star.

[0037] (vi) The ground simulation system uses the sensor model to convert the actual attitude information of the celestial body into the output information of the sensor and output it to the satellite control system;

[0038] The entire simulation process has ended.

[0039] Part Two includes:

[0040] (i) The ground simulation system stores the angular acceleration y(t) output by the accelerometer model into the database;

[0041] (ii) The power spectral density of angular acceleration at the satellite's center of mass is calculated using angular acceleration information. The calculation formula is as follows:

[0042]

[0043] A power spectral density calculation program was developed using the above formula. The calculation process is as follows: ① Take the truncation of the actual satellite output angular acceleration y(t) in the time interval [-T, T]; ② Calculate the Fourier transform of y(t), denoted as y(ω); ③ Calculate the power sum at all frequencies within the 2T time interval, E[y(ω)]. 2 ] represents y(ω) 2 ④ Calculate the average power over a time interval of 2T; ⑤ Take the square root of the average power value.

[0044] The average power of the satellite angular acceleration y(t) is calculated using formula (6), which is the power spectral density value of the angular acceleration.

[0045] (III) The effectiveness of satellite ultra-quiet control and the achievement of indicators are evaluated by power spectral density curves.

[0046] Simulation verification tests were conducted using the above process, with data collected at a sampling period of 10ms, totaling 11,152 data points. The power spectral density of the triaxial angular acceleration was calculated, and the results were plotted as follows: Figures 4 to 6 As shown in the figure. The blue curve in the figure represents [0.2×10]. -3 The red curve represents the upper limit of the required index value within the frequency range of [Hz to 0.1Hz]. The red curve represents the actual angular acceleration power spectral density value of the control system obtained using the method described in this invention. If the red curve exceeds the blue curve entirely or partially within the required frequency range, the index is considered not met; conversely, if the red curve is entirely below the blue curve within the required frequency range, the index is considered met. The above evaluation method can be used to evaluate simulation verification results. In this example figure, it can be clearly seen that the actual angular acceleration power spectral density curves within the required frequency range are all below the blue curve, indicating that the index requirements are met.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] (1) The method of the present invention has the characteristics of being independent and not affecting normal ground simulation verification. It adopts the advantage of introducing the real angular velocity information of the external system to achieve objectivity and accuracy.

[0049] (2) While ensuring the normal operation of satellite software tasks, this invention simulates the working mechanism of the actuator more accurately and can quickly and accurately feed back the attitude information of the star.

[0050] (3) The present invention uses automatic calculation of power spectral density at the centroid to evaluate the control index of the ultra-quiet platform, which can efficiently complete the system evaluation.

[0051] (4) This invention can assess the distribution of energy of rotation caused by torque at the center of mass of a star with frequency, and thus reflect the control status of the ultra-quiet control system. Attached Figure Description

[0052] Figure 1 This is a simplified simulation verification diagram of the method of the present invention.

[0053] Figure 2 A simplified diagram of the data acquisition and execution mechanism of traditional ground simulation equipment.

[0054] Figure 3 A simplified diagram of the actuator output for the ground simulation equipment of the ultra-quiet control system.

[0055] Figure 4 This is the roll-off angular acceleration power-skin density curve.

[0056] Figure 5 This is the pitch angle acceleration power spectral density curve.

[0057] Figure 6 This is the power spectral density curve for yaw angle acceleration. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0059] A ground simulation verification method for an ultra-quiet control system is presented, with a simplified simulation verification diagram as shown below. Figure 1 As shown, the ground simulation verification method consists of two parts;

[0060] Part One includes:

[0061] After the satellite control system is powered on, the satellite enters normal control mode and normal data exchange occurs between the satellite and the ground.

[0062] The satellite control system calculates attitude and control quantities by collecting the output information of the sensors in the ground simulation system, and then calculates the control information of the actuators based on the control quantities.

[0063] The ground simulation system collects control information from the actuators, and the ground simulation equipment collects simplified output diagrams from the actuators as shown below. Figure 3 As shown, the control torque acting on the celestial body is calculated;

[0064] The ground simulation system calculates the space environment disturbance torque on the celestial body using orbital information and a space environment torque model;

[0065] The ground simulation system calculates the current attitude information of the celestial body and the angular acceleration of the satellite's center of mass by controlling the torque and the disturbance torque of the space environment;

[0066] The ground simulation system incorporates an accelerometer model, which incorporates the satellite's center of mass angular acceleration into the accelerometer model to calculate the actual angular acceleration at the satellite's center of mass.

[0067] The ground simulation system uses the sensor model to convert the current attitude information of the celestial body into the output information of the sensor, which is then output to the satellite control system.

[0068] Part Two includes:

[0069] The ground simulation system stores the actual angular acceleration at the center of mass of the celestial body into a database;

[0070] By using the actual angular acceleration at the center of mass of the celestial body, the power spectral density of the angular acceleration at the center of mass of the satellite is calculated, and the satellite's ultrastatic control effect and the achievement of indicators are evaluated based on the power spectral density curve.

[0071] A simplified simulation verification diagram is shown below. Figure 2 As shown.

[0072] Furthermore, when the ground simulation system collects the control information output by the actuator:

[0073] The control cycle of the ground simulation system has been changed to 10ms;

[0074] The control cycle of the satellite control subsystem is 500ms;

[0075] A torque output model for the magnetic torque generator is established. This model generates a magnetic moment based on the control information output by the satellite control system. The magnetic moment interacts with the Earth's magnetic field to produce the satellite control torque, which is expressed as follows:

[0076] T M =M×B…………(2)

[0077] Magnetic torque M = M xb M yb M zb ”, of which M xb M is the magnetic moment in the x-axis direction. yb M is the magnetic moment in the y-axis direction. zb The magnetic moment in the z-axis direction, [B xb B yb B zb [T] represents the components of the geomagnetic field along the three axes of the satellite's main system. mx T is the control torque generated in the x-axis direction. my T is the control torque generated in the y-axis direction. mz The control torque generated in the z-axis direction is calculated using the following formula:

[0078] T mx =M yb B zb-M zb B yb

[0079] T my =M zb B xb -M xb B zb

[0080] T mz =M xb B yb -M yb B xb …(3)

[0081] The method for calculating the magnetic moment of a magnetic torque converter, taking the X magnetic torque converter as an example:

[0082]

[0083] Where Δt x+ and Δt x- These represent the widths of the positive and negative pulses of the magnetic torquer within the simulation period T, where T is the simulation period. The magnetic torquer used in the ultra-quiet control system is 30 A·m. 2 .

[0084] The magnetic torque output of the actuator in the control subsystem is non-linear. The FPGA of the ground simulation system calculates the magnetic moment generated by the magnetic torquer by acquiring the output control voltage in real time. When the ground simulation system calculates the torque generated by the interaction between the magnetic moment and the geomagnetic field, it ensures that the latest magnetic moment output is used. A specific acquisition diagram is shown below. Figure 2 As shown.

[0085] The faster the FPGA acquisition cycle, the more accurately it can acquire the true output characteristics of the magnetic torquer; the shorter the simulation cycle, the faster the iteration speed, and the more accurate and realistic the attitude information calculated by the ground simulation system.

[0086] The torques acting on a celestial body include control torques and disturbance torques from the space environment.

[0087] The Euler angles of a celestial body are calculated by the torque acting on it, and then converted into angular velocity and angular acceleration information.

[0088] Furthermore, an accelerometer model was built in the ground simulation system, and the angular velocity of the celestial body generated by the combined action of the control torque produced by the actuator and the disturbance torque of the space environment was incorporated into the accelerometer model:

[0089] y(t)=a(t)+b(t)+η1(t)+f1·a(t)+f2·a 2 (t)…(5)

[0090] In the formula, y(t) is the output vector of the angular acceleration measurement; a(t) is the angular acceleration of the celestial body calculated by the ground simulation system, i.e., the theoretical angular acceleration; b(t) is the constant drift of the accelerometer angular acceleration measurement; and f1·a(t) and f2·a(t) are also present. 2 f(t) represents the linear and nonlinear errors, respectively; f1 and f2 are the coefficients of the known linear and quadratic terms; η1(t) is an approximation of a three-dimensional Gaussian white noise vector.

[0091] Furthermore, the satellite angular acceleration power spectral density characterizes the distribution of energy generated by the torque acting on the satellite as a function of frequency, and the calculation formula is as follows:

[0092]

[0093] The power spectral density calculation process is as follows: ① Take the truncation of the actual angular acceleration y(t) output by the satellite in the time interval [-T, T]; ② Calculate the Fourier transform of y(t), denoted as y(t)(ω); ③ Calculate the power of y(t)(ω) at all frequencies within the 2T time interval; ④ Calculate the average power over the 2T time interval; ⑤ Take the square root of the average power value.

[0094] The average power of the satellite angular acceleration y(t) is calculated using formula (6), which is the power spectral density value of the angular acceleration.

[0095] The power spectral density curve is used to evaluate the satellite's ultra-quiet control indicators and results.

[0096] Simulation verification tests were conducted using the above process, with data collected at a sampling period of 10ms, totaling 11,152 data points. The power spectral density of the triaxial angular acceleration was calculated, and the results were plotted as follows: Figures 4 to 6 As shown in the figure. The blue curve in the figure represents [0.2×10]. -3 The red curve represents the upper limit of the required index value within the frequency range of [Hz to 0.1Hz]. The red curve represents the actual angular acceleration power spectral density value of the control system obtained using the method described in this invention. If the red curve exceeds the blue curve entirely or partially within the required frequency range, the index is considered not met; conversely, if the red curve is entirely below the blue curve within the required frequency range, the index is considered met. The above evaluation method can be used to evaluate simulation verification results. In this example figure, it can be clearly seen that the actual angular acceleration power spectral density curves within the required frequency range are all below the blue curve, indicating that the index requirements are met.

[0097] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0098] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A super static control system ground simulation verification method, characterized in that, Comprise two parts; The first part comprises: After the satellite control system is powered on, the satellite enters a normal control mode, and normal data interaction is performed between the satellite and the ground simulation system; The satellite control system calculates the attitude and control quantity by collecting the output information of the ground simulation system, and calculates the control information of the actuator by the control quantity; The ground simulation system collects the control information of the actuator, and calculates the control torque of the satellite; The ground simulation system calculates the space environment interference torque of the satellite by the orbit information and the space environment torque model; The ground simulation system calculates the current attitude information of the satellite and the angular acceleration of the satellite center of mass by the control torque and the space environment interference torque; The ground simulation system is provided with an accelerometer model, and the angular acceleration of the satellite center of mass is introduced into the accelerometer model to calculate the real angular acceleration of the satellite center of mass; The ground simulation system converts the current attitude information of the satellite into output information of the ground simulation system, and outputs the output information to the satellite control system; The second part comprises: The ground simulation system stores the real angular acceleration of the satellite center of mass in a database; The power spectral density of the angular acceleration of the satellite center of mass is calculated based on the real angular acceleration of the satellite center of mass, and the satellite super-static control effect and the index reaching condition are evaluated based on the power spectral density curve; The actuator is a magnetic torque device, and the control information is a control instruction voltage; The ground simulation system collects the control information of the actuator and establishes a magnetic moment output model to calculate the control torque of the satellite; The control torque of the satellite is calculated in the following manner: The ground simulation system determines the control moment acting on the satellite as T m = [T mx T my T mz ] by the magnetic moment of the magnetic moment device and the earth magnetic field model, wherein T mx is the control moment generated in the rolling axis x direction, T my is the control moment generated in the pitching axis y direction, and T mz is the control moment generated in the yawing axis z direction, and the calculation formula is as follows: T mx = M yb B zb - M zb B yb T my = M zb B xb - M xb B zb T mz = M xb B yb - M yb B xb .....(1) Magnetic moment M = [M xb M yb M zb ], where M xb is the magnetic moment in the x direction of the roll axis, M yb is the magnetic moment in the y direction of the pitch axis, and M zb is the magnetic moment in the z direction of the yaw axis, and B = [B xb B yb B zb ] are the components of the geomagnetic field in the three axes of the satellite body system.

2. The super-steady control system ground simulation verification method according to claim 1, characterized in that, T d , T d T dg , T da , T dm , T ds ; T d = T dg + T da + T dm + T ds .

3. The super-steady control system ground simulation verification method according to claim 1, wherein, Satellite center of mass processing wants angular acceleration The calculation process is as follows: Let t be the components of the angular acceleration of the satellite's center of mass relative to the inertial coordinate system in the satellite's own system along the roll axis (x), pitch axis (y), and yaw axis (z), and let I be the satellite's moment of inertia. -1 It is the inverse matrix of I; T is the control torque T m and the spatial environmental disturbance torque T d .

4. The super-stable control system ground simulation verification method of claim 1, wherein, The accelerometer model in the ground simulation system can be started by an instruction.

5. The super-stable control system ground simulation verification method of claim 1, wherein, The real angular acceleration of the satellite center of mass is determined in the following manner: y(t) = a(t) + b(t) + η1(t) + f1-a(t) + f2-a 2 (t)…(5) where y(t) is the real angular acceleration measured by the accelerometer model at the satellite center of mass; a(t) is the processed angular acceleration calculated by the ground simulation system at the satellite center of mass; b(t) is the constant drift of the angular acceleration measurement of the accelerometer model; f1·a(t) and f2·a(t) are the linear and nonlinear errors, respectively; f1 and f2 are the coefficients of the first-order and second-order terms; and η1(t) is an approximate three-dimensional Gaussian white noise vector. 2 where y(t) is the real angular acceleration measured by the accelerometer model at the satellite center of mass; a(t) is the processed angular acceleration calculated by the ground simulation system at the satellite center of mass; b(t) is the constant drift of the angular acceleration measurement of the accelerometer model; f1·a(t) and f2·a(t) are the linear and nonlinear errors, respectively; f1 and f2 are the coefficients of the first-order and second-order terms; and η1(t) is an approximate three-dimensional Gaussian white noise vector.

6. The super-stable control system ground simulation verification method of claim 1, wherein, The power spectral density of the angular acceleration of the satellite center of mass is calculated based on the real angular acceleration of the satellite center of mass, and the power spectral density calculation process is as follows: ① Take the truncation of the real angular acceleration y(t) of the satellite center of mass in the time interval [-T, T]; ② Calculate the Fourier transform of y(t), denoted as y(t)(ω); ③ In the time interval of 2T, the power of y(t)(ω) at all frequencies is calculated; ④ Calculate the average power in 2T time; ⑤ Take the square root of the average power value.

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