Ground simulation verification method for ultra-static control system

Abstract

The invention relates to a ground simulation verification method for a statically inactive control system, which belongs to the field of ground verification of statically inactive control systems and comprises the following steps of: obtaining high-precision control moment information by establishing an accurate magnetic moment output model of a magnetic torquer; an accurate accelerometer model is introduced to more objectively and accurately calculate the real angular acceleration of the star; an angular acceleration power spectral density curve is automatically generated, and the power spectral density condition at the satellite centroid can be checked in real time. The method has the advantages that the method is independent and does not affect normal ground simulation verification, and the real angular velocity information of an external system is introduced, so that the method is objective and accurate.

Description

Technical Field

[0001] The present invention relates to a ground simulation verification method for an ultra-quiet control system, belonging to the field of ground verification of ultra-quiet control systems. Background Art

[0002] The ultra-quiet control system of small satellites is a control system with an extremely low angular acceleration power spectral density. The on-board control system uses actuators without vibration, generally including a cold gas propulsion system and a magnetic torquer. In the on-orbit scientific observation mode, the cold gas propulsion system is generally in an inoperative state, and satellite attitude control only uses the magnetic torquer for control.

[0003] The indexes of the ultra-quiet control system are usually evaluated by 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 rotating under the action of torque with frequency. Since both the active control torque and the environmental disturbance torque of the ultra-quiet control system are relatively small in magnitude, the accuracy of the active control torque signal acquisition and the accuracy of the environmental disturbance torque simulation model will have a greater impact on the ground simulation accuracy. Therefore, these two are very important for the index evaluation of the ultra-quiet control system. Secondly, since the ultra-quiet control system only uses the magnetic torquer for attitude control for a long time in the scientific observation mode, the torque on the satellite body is relatively single. Therefore, the accuracy of the magnetic moment output model of the magnetic torquer will also have a greater impact on the evaluation index. During the ground simulation verification process of the ultra-quiet control system, the following four problems are encountered:

[0004] First, the simulation period of the traditional ground simulation system is usually 100 ms, the simulation period is long, the data iteration is slow, resulting in slow update of information such as the environmental disturbance torque in space and poor real-time performance.

[0005] Second, the magnetic moment output model of the magnetic torquer is not accurate enough, there is a large difference from the real product state, making the simulation results inaccurate.

[0006] Third, the angular acceleration at the satellite's center of mass obtained from the traditional ground simulation test does not consider measurement noise, and the data is not objectively accurate.

[0007] Fourth, the data processing formula is cumbersome, it takes time to process data, and the real-time performance is poor. Summary of the Invention

[0008] The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, establish an accurate magnetic moment output model of the magnetic torquer, and obtain high-precision control torque information; calculate the true angular acceleration of the satellite body more objectively and accurately by introducing an accurate accelerometer model; automatically generate the angular acceleration power spectral density curve, and the power spectral density at the satellite's center of mass can be viewed in real time.

[0009] The object of the present invention is achieved by the following technical solutions:

[0010] A ground simulation verification method for a super quiet control system, including two parts;

[0011] The first part includes:

[0012] When the satellite ground simulation test starts, after the control system is powered on, the satellite enters the normal control mode, and normal data interaction occurs between the satellite and the ground. The interaction process is as follows:

[0013] (1) The satellite control system estimates the satellite attitude by collecting the output information of the sensors of the ground simulation system and calculates the control amount of the satellite attitude deviation, and calculates the control command information of the actuator through the control amount of the satellite attitude deviation; in this method, the actuator specifically refers to the magnetic torquer, and the control command information specifically refers to the control instruction voltage Mcv;

[0014] (2) The ground simulation system collects the control information of the actuator and establishes a magnetic moment output model, and calculates the control torque received by the satellite body through the dynamic model of the ground simulation system; the calculation process is as follows:

[0015] ① Establish the magnetic moment output model of the magnetic torquer actuator

[0016] According to the working principle of the magnetic torquer and its circuit, the control information collected by the ground simulation system includes the control instruction voltage Mcv and the current telemetry value TMv in the real magnetic torquer coil, where TMv is a voltage value and can represent the magnetic moment output of the real magnetic torquer. In order to accurately reflect the output magnetic moment of the real magnetic torquer, the following calculation and processing are performed:

[0017] The current telemetry value collected at the start time of the ground simulation period is recorded as TMv0, and the current telemetry value TMv1 at the end of the ground simulation period is estimated, and we can get: TMv1 = TMv0 + Mcv / (Lm × T), where T is the known ground simulation period and Lm is the equivalent inductance value of the magnetic torquer;

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

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

[0020] ② Calculation of the control torque received by the satellite body:

[0021] The ground simulation system generates the control torque T acting on the satellite body through the magnetic moment of the magnetic torquer and the earth's magnetic field model m =[T mx T my T mz , where T mx is the control torque generated in the x-axis direction, T myThe control torque generated in the y-axis direction, T mz The control torque generated in the z-axis direction, and the calculation formula is as follows:

[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] The magnetic moment of the magnetic torquer M = [M xb M yb M zb , where M xb is the magnetic moment in the x-axis direction, M yb is the magnetic moment in the y-axis direction, M zb is the magnetic moment in the z-axis direction, B = [B xb B yb B zb are the components of the geomagnetic field in the three axes of the satellite's body frame.

[0026] (3) The ground simulation system calculates the space environmental disturbance torque T d acting on the satellite body through the orbital information and the space environmental torque model. T d includes the satellite's gravity gradient torque T dg , aerodynamic torque T da , residual magnetic torque T dm , and solar radiation pressure T ds .

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

[0028] (4) The ground simulation system takes the sum T of the control torque T m and the space environmental disturbance torque T d as the input of the satellite dynamics equation, and calculates the true attitude information of the satellite body at time t and the ideal angular acceleration of the satellite's center of mass. The calculation process is as follows:

[0029]

[0030] The three-axis components of the angular acceleration of the satellite's centroid relative to the inertial coordinate system at time t on the rolling axis x, pitching axis y, and yaw axis z of the satellite's body frame. I is the satellite's moment of inertia, and I -1 is the inverse matrix of I.

[0031] (5) Install the accelerometer model in the ground simulation system and introduce the angular acceleration information into the accelerometer model to calculate the true angular acceleration at the centroid of the satellite body. The steps are as follows:

[0032] ① The accelerometer model in the ground simulation system can be activated by an instruction.

[0033] ② After the accelerometer model is activated, the ground simulation system inputs the true angular acceleration at the centroid of the satellite body generated under the combined action of the control torque generated by the actuator and the space environment disturbance torque into the accelerometer model:

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

[0035] where, in the formula, y(t) is the true angular acceleration measured by the accelerometer at the centroid of the satellite body; a(t) is the angular velocity information of the satellite body calculated by the ground simulation system, that is, the theoretical angular acceleration calculated in the first part, step (4); b(t) is the constant drift of the accelerometer angular acceleration measurement, and f1·a(t), f2·a 2 (t) are the linear and nonlinear errors respectively, and f1, f2 are the known coefficients of the first-order and second-order terms; η1(t) is approximately a three-dimensional Gaussian white noise vector.

[0036] Through the accelerometer model built in the ground simulation system, the objective and true angular acceleration y(t) at the centroid of the satellite body is obtained.

[0037] (6) The ground simulation system converts the true attitude information of the satellite body into the output information of the sensor through the sensor model and outputs it to the satellite control system;

[0038] The entire simulation process ends.

[0039] The second part includes:

[0040] (1) The ground simulation system stores the angular acceleration y(t) output by the accelerometer model in the database;

[0041] (2) Calculate the power spectral density of the angular acceleration at the centroid of the satellite body through the angular acceleration information. The calculation formula is as follows:

[0042]

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

[0044] Use formula (6) to calculate the average power of the satellite angular acceleration y(t), that is, the power spectral density value of the angular acceleration.

[0045] (3) Evaluate the satellite's ultra-quiet control effect and the achievement of indicators through the power spectral density curve.

[0046] Perform simulation verification tests through the above process. Take data with a sampling period of 10 ms and 11,152 data points, and calculate the power spectral density of the three-axis angular acceleration. The calculation results are plotted as a curve as Figures 4 to 6 shown. The blue curve in the figure represents the upper limit of the indicator requirement value in the frequency range of [0.2×10 -3 Hz to 0.1 Hz], and the red curve is the true angular acceleration power spectral density value of the control system obtained by using the method of the present invention. If the red curve completely or partially exceeds the blue curve within the required frequency range, it is determined that the indicator is not met; on the contrary, if the red curve is completely below the blue curve within the required frequency range, it is determined that the indicator is met. The above evaluation method can be used to evaluate the simulation verification results. It can be intuitively seen from the figure of this example that the true angular acceleration power spectral density curves within the required frequency range are all below the blue curve, and it is determined that the indicator requirements are met.

[0047] The present invention has the following beneficial effects compared with the prior art:

[0048] (1) The method of the present invention has the characteristics of being independent and not affecting normal ground simulation verification. By introducing the true angular velocity information of the external system, it has the advantages of objectivity and accuracy.

[0049] (2) While ensuring the normal operation of the satellite's normal software tasks, the present invention more accurately simulates the working mechanism of the actuator and can quickly and accurately feedback the attitude information of the satellite body.

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

[0051] (4) The present invention can evaluate the distribution of the energy of the torque acting on the centroid of the celestial body and rotating with respect to frequency, and further reflect the control situation of the ultra-quiet control system. Brief Description of the Drawings

[0052] Figure 1 It is a schematic diagram for the simulation verification of the method of the present invention.

[0053] Figure 2 It is a schematic diagram of the output of the actuator collected by the traditional ground simulation equipment.

[0054] Figure 3 It is a schematic diagram of the output of the actuator collected by the ground simulation equipment of the ultra-quiet control system.

[0055] Figure 4 It is the power spectral density curve of the roll angular acceleration.

[0056] Figure 5 It is the power spectral density curve of the pitch angular acceleration.

[0057] Figure 6 It is the power spectral density curve of the yaw angular acceleration. Detailed Embodiment

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

[0059] An ultra-quiet control system ground simulation verification method, the simulation verification schematic diagram is as Figure 1 shown, and the ground simulation verification method includes two parts;

[0060] The first part includes:

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

[0062] The satellite control system calculates the attitude and control quantity by collecting the output information of the sensors of the ground simulation system, and calculates the control information of the actuator through the control quantity;

[0063] The ground simulation system collects the control information of the actuator, and the ground simulation equipment collects the output schematic diagram of the actuator as Figure 3 shown, and calculates the control torque received by the celestial body;

[0064] The ground simulation system calculates the space environment disturbance torque received by the celestial body through the orbit information and the space environment torque model;

[0065] The ground simulation system calculates the current attitude information of the celestial body and the ideal angular acceleration of the satellite centroid through the control torque and the space environment disturbance torque;

[0066] An accelerometer model is installed in the ground simulation system. The ideal angular acceleration of the satellite's center of mass is introduced into the accelerometer model to calculate the true angular acceleration at the center of mass of the satellite body.

[0067] The ground simulation system converts the current attitude information of the satellite body into the output information of the sensor through the sensor model and outputs it to the satellite control system.

[0068] The second part includes:

[0069] The ground simulation system stores the true angular acceleration at the center of mass of the satellite body in the database.

[0070] Based on the true angular acceleration at the center of mass of the satellite body, calculate the power spectral density of the angular acceleration at the center of mass of the satellite. Evaluate the satellite's ultra-quiet control effect and the achievement of indicators based on the power spectral density curve.

[0071] The schematic diagram of simulation verification is as Figure 2 shown.

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

[0073] The control period of the ground simulation system is changed to 10 ms;

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

[0075] Establish a torque output model of the magnetorquer. The magnetorquer model generates a magnetic moment according to the control information output by the satellite control system. The magnetic moment interacts with the geomagnetic field to generate a satellite control torque. The generated control torque is expressed as:

[0076] T M = M × B …………(2)

[0077] The magnetic moment M of the magnetorquer = M xb M yb M zb ", where M xb is the magnetic moment in the x-axis direction, M yb is the magnetic moment in the y-axis direction, M zb is the magnetic moment in the z-axis direction, [B xb B yb B zb are the components of the geomagnetic field in the three axes of the satellite body frame, T mx is the control torque generated in the x-axis direction, T my is the control torque generated in the y-axis direction, T mz is the control torque generated in the z-axis direction. The calculation formula is as follows:

[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 calculation method of the magnetic moment of the magnetic torquer takes the X magnetic torquer as an example:

[0082]

[0083] where Δt x+ and Δt x- are the widths of the positive and negative pulses of the magnetic torquer within the simulation period T respectively, T is the simulation period, and the magnetic torquer adopted by the super-static control system is 30 A·m 2 .

[0084] The output of the magnetic torquer of the actuator in the control subsystem is a non-linear output. The FPGA of the ground simulation system calculates the magnetic moment generated by the magnetic torquer by collecting 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 it is the latest magnetic moment output. The specific acquisition schematic diagram is as Figure 2 shown.

[0085] The faster the FPGA acquisition period, the more real output characteristics of the magnetic torquer can be acquired. The smaller the simulation period, the faster the iteration speed, and the more accurate and real the attitude information calculated by the ground simulation system.

[0086] The torques acting on the satellite include the control torque and the space environment disturbance torque.

[0087] The Euler angles of the satellite are calculated through the torques acting on the satellite, and the angular velocity and angular acceleration information of the satellite are converted through the Euler angles.

[0088] Furthermore, an accelerometer model is built in the ground simulation system, and the angular velocity of the satellite generated by the combined action of the control torque generated by the actuator and the space environment disturbance torque is brought into the accelerometer model:

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

[0090] Among them, in the formula, y(t) is the angular acceleration measurement output vector; a(t) is the angular acceleration of the satellite body calculated by the ground simulation system, that is, the theoretical angular acceleration, b(t) is the constant drift of the angular acceleration measurement of the accelerometer, and f1·a(t), f2·a 2 (t) are the linear and nonlinear errors respectively, and f1, f2 are the coefficients of the known first-order and second-order terms; η1(t) is approximately a three-dimensional Gaussian white noise vector.

[0091] Furthermore, the power spectral density of the satellite angular acceleration characterizes the distribution of the energy of the torque received by the satellite for rotation with frequency, and the calculation formula is as follows:

[0092]

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

[0095] The satellite ultra-static control index and result are evaluated through the power spectral density curve.

[0096] Through the above process for simulation verification test, taking data with a sampling period of 10 ms and 11152 data points, the power spectral density of the three-axis angular acceleration is calculated, and the calculation results are plotted as a curve as Figures 4 to 6 shown. The blue curve in the figure represents the upper limit of the index requirement value in the frequency range of [0.2×10 -3 Hz to 0.1 Hz], and the red curve is the true power spectral density value of the angular acceleration of the control system obtained by using the method described in the present invention. If the red curve completely or partially exceeds the blue curve within the required frequency range, it is determined that the index is not met; on the contrary, if the red curve is completely below the blue curve within the required frequency range, it is determined that the index is met. The above evaluation method can be used for the evaluation of the simulation verification results. It can be intuitively seen from the figure of this example that the true power spectral density curves of the angular acceleration within the required frequency range are all below the blue curve, and it is determined that the index requirements are met.

[0097] The content not described in detail in the specification of the present invention belongs to the well-known technology in the art.

[0098] Although the present invention has been disclosed above in 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 solution of the present invention by using the methods and technical content disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A ground simulation verification method for an ultra-quiet control system, characterized in that: It consists of two parts; The first part includes: After the satellite control system is powered on, the satellite enters the normal control mode, and normal data exchange is carried out between the satellite and the ground; The satellite control system calculates the attitude and control quantity by collecting the output information of the ground simulation system sensor, and calculates the control information of the actuator through the control quantity; The ground simulation system collects the control information of the actuator and calculates the control torque on the satellite; The ground simulation system calculates the space environment interference torque on the star through orbit information and space environment torque model; The ground simulation system calculates the current attitude information of the satellite and the angular acceleration of the satellite's center of mass through the control torque and the space environment interference torque; The accelerometer model is loaded into the ground simulation system, and the ideal angular acceleration of the satellite's center of mass is introduced into the accelerometer model to calculate the real angular acceleration at the center of mass of the satellite. The ground simulation system converts the current attitude information of the satellite into the output information of the sensor through the sensor model and outputs it to the satellite control system; The second part includes: The ground simulation system stores the real angular acceleration at the center of mass of the star into the database; The power spectrum density of the angular acceleration at the satellite's center of mass is calculated using the true angular acceleration at the satellite's center of mass, and the satellite's super-quiet control effect and indicator achievement are evaluated based on the power spectrum density curve.

2. The ground simulation verification method of the super-quiet control system according to claim 1 is characterized in that: The actuator refers to the magnetic torquer, and the control information refers to the control command voltage.

3. The ground simulation verification method of the super-quiet control system according to claim 2 is characterized in that: The ground simulation system collects the control information of the actuator and establishes a magnetic torque output model to calculate the control torque acting on the star.

4. The ground simulation verification method of the super-quiet control system according to claim 3 is characterized in that: The control torque on the star is calculated as follows: The ground simulation system determines the control torque acting on the star as T through the magnetic torque device and the earth's magnetic field model. m =[T mx T my T mz ], where T mx is the control torque generated in the x-axis direction, T my is the control torque generated in the y-axis direction, T mz is the control torque generated in the z-axis 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 torque device magnetic moment M = [M xb M yb M zb ], where M xb is the magnetic moment in the x-axis direction, M yb is the magnetic moment in the y-axis direction, M zb is the magnetic moment in the z-axis direction, B=[B xb B yb B zb ] is the component of the geomagnetic field in the three axes of the satellite system.

5. The ground simulation verification method of the super-quiet control system according to claim 1 is characterized in that: The space environment disturbance torque T of the star d , T d Including satellite gravity gradient moment T dg , aerodynamic torque T da , residual magnetic torque T dm 、Sunlight Pressure T ds ; T d =T dg +T da +T dm +T ds 。 6. The ground simulation verification method of the super-quiet control system according to claim 1 is characterized in that: Satellite center of mass processing ideal angular acceleration The calculation process is as follows: is the component of the angular acceleration of the satellite mass center relative to the inertial coordinate system at time t in the roll axis x, pitch axis y, and yaw axis z of the satellite system, I is the satellite moment of inertia, and I -1 is the inverse matrix of I; T is the control torque T m and space environment disturbance torque T d sum.

7. The ground simulation verification method of the super-quiet control system according to claim 1 is characterized in that: The accelerometer model in the ground simulation system can be turned on by command.

8. The ground simulation verification method of the super-quiet control system according to claim 1 is characterized in that: The true angular acceleration at the center of mass of the star is determined as follows: y(t)=a(t)+b(t)+η1(t)+f1·a(t)+f2·a 2 (t)…(5) Where y(t) is the real angular acceleration at the center of mass of the satellite measured by the accelerometer; a(t) is the ideal angular acceleration of the satellite center of mass calculated by the ground simulation system; b(t) is the constant drift of the angular acceleration measurement of the accelerometer; f1·a(t), f2·a 2 (t) are linear and nonlinear errors respectively, f1 and f2 are the coefficients of the known first-order and second-order terms; η1(t) is approximately a three-dimensional Gaussian white noise vector.

9. The ground simulation verification method of the super-quiet control system according to claim 1 is characterized in that: The power spectrum density of the angular acceleration at the satellite’s center of mass is calculated using the angular acceleration information. The power spectrum density calculation process is as follows: ①Truncate the actual output angular acceleration y(t) of the satellite in the time interval [-T,T]; ②Calculate the Fourier transform of y(t), recorded as y(t)(ω); ③Calculate the power and power of y(t)(ω) at all frequencies in the 2T time interval; ④Calculate the average power within the 2T time interval; ⑤Take the square root of the average power value.

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