WO2020103290A1

WO2020103290A1 - Attitude control method for final substage orbital application subsystem

Info

Publication number: WO2020103290A1
Application number: PCT/CN2018/124508
Authority: WO
Inventors: 曾占魁; 郑琦; 邹旭; 蒋丽丽; 青志能; 吴俊杰; 魏然; 江炜; 万玉柱
Original assignee: 上海埃依斯航天科技有限公司
Priority date: 2018-11-19
Filing date: 2018-12-27
Publication date: 2020-05-28
Also published as: CN109573105A; CN109573105B

Abstract

An attitude control method for a final substage orbital application subsystem, comprising: when the final substage orbital application subsystem is in a rate damping phase, an attitude controller utilizes a minus B-dot magnetic control law, and uses a three-axis magnetorquer as an execution mechanism to exert a control magnetic torque in order to damp the angular velocity of the final substage orbital application subsystem in the pitch axis, roll axis, and yaw axis, performing despinning processing on the final substage orbital application subsystem; and when the final substage orbital application subsystem is in a steady-state control phase, the attitude controller, in a pitch loop, utilizes a PD control law having dead time compensation, and uses a bias momentum wheel and the three-axis magnetorquer as execution mechanisms to exert a control magnetic torque in order to complete pitch loop attitude control, and roll/yaw loops are designed using a sliding mode controller. The present method solves the problem of sun pointing in final substage orbital application subsystems, while also eliminating the impact of dead time, and raising the accuracy of attitude control in final substage orbital application subsystems.

Description

Attitude control method of the application subsystem of the last sub-track staying track

This application requests the priority of the Chinese patent application with the application number 201811372982.1 (invention name: attitude control method of the last sub-level track- keeping application subsystem ) filed on December 21 , 2018 .

Technical field

The invention belongs to the technical field of spacecraft control, and relates to an attitude control method, in particular to an attitude control method of an application subsystem of the last sub-track staying track.

Background technique

In the past, after every rocket launch in various countries, as the first-stage rocket, second-stage rocket and fairing fell off and returned to the ground, the last stage of the rocket would enter orbit with its payload, and occupy valuable orbital resources in space for a long time. It poses a safety threat to orbiting space vehicles and is currently the largest volume of space junk. Using the carrying measurement system at the stage of the last stage of the launch vehicle to transform the original stage of the rocket into a low-cost scientific experiment and communication platform can turn waste into treasure.

The traditional spacecraft has a controllable attitude and can obtain energy stably by controlling the solar panel of the aircraft to the sun. However, for the last stage of the rocket, its attitude is constantly spinning with a certain nutation in space, and the process of sensor signal acquisition, the calculation process of the controller and the actuation process of the actuator will produce a time lag, giving The design of the measurement and control system and the energy system has brought difficulties, it is difficult to achieve the orientation to Japan, and effective and controllable data cannot be obtained.

Summary of the invention

The object of the present invention is to provide a post-tracking application subsystem attitude control method to solve the problems raised in the above technical background.

To achieve the above objectives, the present invention adopts the following technical solutions:

An attitude control method of the last sub-level track-keeping application subsystem includes:

After the last sub-tracking application subsystem enters the mission setting track, a setting threshold value of the post-tracking application subsystem's attitude angular rate is pre-stored in the attitude controller, when the attitude angular rate is greater than the attitude controller Within the set threshold, start the rate damping phase, and de-rotate the last sub-stage derailment application subsystem; when the attitude angular rate is less than or equal to the set threshold in the attitude controller, the last sub-stage derailment application The subsystem enters the steady-state control phase of ground orientation;

Among them, in the rate damping phase, the attitude controller uses the Minus B-dot magnetron law, and uses a three-axis magnetic torque device as an actuator to apply a control magnetic moment to damp the pitch axis of the last sub-tracking application subsystem , The angular velocity of the rolling axis and the deflection axis to achieve attitude control in the rate damping phase;

Among them, in the steady state control phase, the attitude controller adopts the PD control law with time lag compensation in the pitch loop, and uses the bias momentum wheel and the three-axis magnetic torque device as the actuator to apply the control magnetic moment to complete Attitude control of the pitch loop, while eliminating the effects of time lag; the attitude controller uses sliding mode control laws to design switching functions and variable structure control laws in the rolling loop and offset loop, constructing the last sub-track application subsystem Control commands for rolling and yaw circuits.

Preferably, an implementation structure of the three-axis magnetic torque converter includes: three independent magnetic rods with the same performance, and the three magnetic rods are respectively installed along the X, Y, and Z axes of the last sub-track gauge measuring subsystem.

Preferably, the control torque applied by the three-axis magnetic torque device as an actuator is:

which is,

Among them, M is the control magnetic moment applied by the three-axis magnetic torque device, and the three directions of X, Y and Z are [M _x M _y M _z ];

It is the rate of change of the magnetic field vector under the system of the last sub-track-keeping application subsystem. The three directions of X, Y, and Z are [B _bx B _by B _bz ], which are obtained by differential processing from the measured values of the magnetometer respectively ; K is the control gain coefficient, and the three directions of X, Y, and Z are k ₁ , k ₂ , and k ₃ .

Preferably, the offset momentum wheel is installed in the negative direction of the pitch axis.

Preferably, the attitude control method of the last sub-stage track-keeping application subsystem further includes:

Select an attitude sensor to measure the attitude information of the last sub-track-keeping application subsystem;

Based on the measurement data of the attitude sensor, an attitude determination algorithm is used to determine the attitude.

More preferably, the attitude determination algorithm includes:

When the last sub-stage track keeping application subsystem works in the rate damping stage, the attitude determination algorithm is selected, but not limited to, one or more of a dual vector attitude determination algorithm and a single magnetic vector attitude determination algorithm;

When the last sub-stage track keeping application subsystem works in the steady state control stage, the attitude determination algorithm is selected, but not limited to, one or more of the extended Kalman filtering method and the single magnetic vector attitude determination algorithm.

More preferably, the attitude sensor includes, but is not limited to, one or more of a sun sensor, a three-axis magnetic torque sensor, a magnetometer, and a gyro.

Step 1: Using Euler angle method, the posture kinematics model is established as

Equation (1), ω is the component array of the inertial angular velocity of the last sub-tracking application subsystem in the body coordinate system; ω _x , ω _y , ω _z are the three-axis inertial angular velocity of the last sub-tracking application subsystem;

Is the three-axis attitude angular velocity, that is, the rolling attitude angular velocity, pitch attitude angular velocity and yaw attitude angular velocity, respectively;

θ and ψ are three-axis attitude angles, namely roll attitude angle, pitch attitude angle and yaw attitude angle; ω _o is the orbital angular velocity;

Step 2: Ignore the influence of flexible factors, and establish the posture dynamic model of the last sub-track application subsystem as

In equation (2), I is the inertial matrix of the last sub-track application subsystem; ω is the component array of the inertial angular velocity of the last sub-track application subsystem in the body coordinate system;

Is the differential of the inertial angular velocity; h is the angular momentum of the offset momentum wheel, and the component on the three axes of the body is h = [h _x h _y h _z ] ^T ; T _c is the control torque and T _d is the disturbance torque;

Step 3: When the last sub-track application subsystem works in the steady-state control stage and the triaxial attitude angular velocity is a small angle (less than or equal to 30 °), simplify the attitude kinematics model as

The configuration of the offset momentum wheel with a fixed speed in the Y direction of the system is used to simplify the attitude dynamic model as

Given that ω _o is a small quantity, equation (4) is further simplified to

In equations (4) and (5), I _x , I _y , and I _z are the three-axis inertial matrix of the last sub-track-keeping application subsystem;

Is the three-axis attitude angular acceleration, that is, the rolling attitude angular acceleration, the pitch attitude angular acceleration, and the yaw attitude angular acceleration, respectively; h _x , h _y , and h _z are the components of the angular momentum h of the offset momentum wheel on the three axes; T _x , T _y and T _z are the components of the control torque T _c on the three axes;

Among them, the pitch loop is decoupled from the rolling loop and the yaw loop.

Preferably, in the steady-state control phase, the attitude controller adopts a PD control law with Smith time lag compensation in the pitch loop, and a Smith predictor is connected to the attitude controller based on the PD control law to complete Attitude control of the pitch loop, including:

The attitude controller transfer function is D (s), i.e., the transfer function of the controlled object execution mechanism is _{^{D o (s) e -τs,}} τ is a pure delay time constant, s is a time variable; controlled object The transfer function that does not include the pure delay part is D _o (s), and the transfer function of the controlled object pure delay part is e ^-τs ; the compensation loop composed of the attitude controller D (s) and the Smith predictor becomes Pure lag compensator, the transfer function D '(s) of the pure lag compensator is

After compensation, the closed-loop transfer function Φ ’(s) of the system is

In contrast, the closed-loop transfer function Φ (s) of the uncompensated system is

After time-lag compensation, e- ^τs in equation (7) is outside the closed-loop control loop and does not affect the stability of the system.

Preferably, in the steady-state control phase, the attitude controller uses a PD control law with Dalin time-lag compensation in the pitch loop to complete the attitude control of the pitch loop.

Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

An attitude control method for the application subsystem of the last sub-track retention system, which uses a bias momentum wheel and a three-axis magnetic torque device as an actuator to apply a control magnetic moment to complete the attitude control. The pitch loop can be designed separately at small attitude angles, using the PD control law with time-lag compensation; the rolling / yaw loop is designed with a sliding mode controller, which solves the problem of the sun orientation of the last sub-track application subsystem and eliminates it The influence of the time lag improves the attitude control accuracy of the last-stage orbit-keeping application subsystem, and is beneficial to the ground imaging and data communication of the remote sensing satellite.

BRIEF DESCRIPTION

FIG. 1 is a schematic diagram of a system structure of an application system of a last-stage rail-retention application system according to a preferred embodiment of the present invention;

Figure 2 is a schematic diagram of a typical attitude control loop structure;

FIG. 3 is a flowchart of the attitude control method of the last sub-track-keeping application subsystem of the preferred embodiment of the present invention;

4 is a schematic diagram of the structure of the attitude control loop of the Smith predictor;

Fig. 5 is a graph of the X-axis rotation angular velocity variation of the last sub-track application subsystem in the rate damping phase;

6 is a graph of the Y-axis rotation angular velocity change of the last-stage track-keeping application subsystem in the rate damping stage;

7 is a curve diagram of the Z-axis rotation angular velocity of the last sub-track retention application subsystem in the rate damping stage;

Fig. 8 is a graph of the yaw angle of the last-stage derailment application subsystem in the rate damping phase;

9 is a curve diagram of the roll angle change of the application subsystem of the last sub-track retention in the rate damping phase;

Fig. 10 is a graph of the change in pitch angle of the application subsystem of the last sub-track keeping track in the rate damping phase;

FIG. 11 is a graph showing the change of the output magnetic moment of the X-axis of the last sub-track application subsystem in the rate damping phase;

FIG. 12 is a graph showing the change of the output magnetic moment of the Y-axis of the last sub-track application subsystem in the rate damping phase;

Fig. 13 is a graph showing the change of the output magnetic moment of the Z-axis of the last sub-track-keeping application subsystem in the rate damping phase;

14 is a graph of the X-axis rotation angular velocity variation of the last-stage track keeping application subsystem when the time-lag compensation algorithm is not used in the steady-state control stage;

15 is a graph of the Y-axis rotation angular velocity variation of the last-stage track keeping application subsystem when the time-lag compensation algorithm is not used in the steady-state control stage;

16 is a graph of the change of the Z-axis rotation angular velocity of the last-stage track keeping application subsystem when the time-lag compensation algorithm is not used in the steady-state control stage;

17 is a graph of the yaw angle of the last sub-stage track-keeping application subsystem when the time-lag compensation algorithm is not used in the steady-state control stage;

18 is a curve diagram of the roll angle change of the last sub-track application subsystem when the time-lag compensation algorithm is not used in the steady-state control stage;

FIG. 19 is a graph of the change in pitch angle of the application subsystem of the last sub-track keeping track when the time-lag compensation algorithm is not used in the steady-state control stage;

FIG. 20 is a graph of the output magnetic moment variation curve of the X-axis of the last sub-track-keeping application subsystem when the time-lag compensation algorithm is not used in the steady-state control stage;

21 is a graph of the Y-axis output magnetic moment variation curve of the last sub-track-keeping application subsystem when the time-lag compensation algorithm is not used in the steady-state control stage;

22 is a graph of the output magnetic moment variation curve of the Z-axis of the last sub-track keeping application subsystem when the time-lag compensation algorithm is not used in the steady-state control stage;

23 is a graph of the X-axis rotation angular velocity variation of the last-stage track keeping application subsystem when the time-lag compensation algorithm is used in the steady-state control stage;

24 is a graph of the Y-axis rotation angular velocity variation of the last-stage track keeping application subsystem when the time-lag compensation algorithm is used in the steady-state control stage;

FIG. 25 is a graph showing the change of the Z-axis rotation angular velocity of the last-stage track keeping application subsystem when the time-lag compensation algorithm is used in the steady-state control stage;

Fig. 26 is a graph of the yaw angle of the last sub-stage track keeping application subsystem when the time-delay compensation algorithm is used in the steady-state control stage;

FIG. 27 is a curve diagram of the roll angle change of the last sub-stage track keeping application subsystem when the time-delay compensation algorithm is used in the steady-state control stage;

FIG. 28 is a graph of the change in pitch angle of the last sub-track application subsystem when the time-delay compensation algorithm is used in the steady-state control stage;

FIG. 29 is a graph showing the change of the X-axis output magnetic moment of the last sub-track-keeping application subsystem when the time-lag compensation algorithm is used in the steady-state control stage;

FIG. 30 is a graph showing the change of the output magnetic moment of the Y-axis of the last sub-track keeping application subsystem when the time-lag compensation algorithm is used in the steady-state control stage;

Fig. 31 is a graph showing the change of the output magnetic moment of the Z axis of the last-stage track keeping application subsystem when the time-lag compensation algorithm is used in the steady-state control stage.

detailed description

The present invention provides an attitude control method for the application subsystem of the last sub-track staying track. In order to make the objectives, technical solutions and effects of the present invention clearer and clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

Example one:

As shown in FIG. 1, this embodiment provides an attitude control system of a last-stage track-keeping application subsystem, which includes an attitude sensor, an attitude controller, and an actuator.

The attitude sensor is used to obtain the attitude information of the last sub-track-keeping application subsystem, and output a signal having a functional relationship with the attitude parameter. Attitude sensors include sun sensors, three-axis magnetic torque devices, GPS and three-axis gyros.

An attitude controller, which is in communication with the attitude sensor, is used to determine the current state of the last child-tracking application subsystem according to the attitude information of the last child-tracking application subsystem, and the current state is the rate The rate damping control command is issued during the damping phase, or the stable control command is issued when the current state is the steady state control phase.

The actuator, which is in communication with the attitude controller, includes a bias momentum wheel and a three-axis magnetic torque device. The offset momentum wheel is installed in the negative direction of the pitch axis; an implementation structure of the three-axis magnetic torque device includes three independent magnetic rods with the same performance, and the three magnetic rods are measured along the remaining track of the last substage respectively The X, Y and Z axes of the subsystem are installed.

The schematic diagram of a typical attitude control loop structure is shown in Figure 2.

Example 2:

As shown in FIG. 3, a method for attitude control of the last sub-track staying application subsystem includes:

After the last sub-tracking application subsystem enters the mission setting track, a setting threshold value of the post-tracking application subsystem's attitude angular rate is pre-stored in the attitude controller, when the attitude angular rate is greater than the attitude controller Within the set threshold, start the rate damping phase, and de-rotate the last sub-stage derailment application subsystem; when the attitude angular rate is less than or equal to the set threshold in the attitude controller, the last sub-stage derailment application The subsystem enters the steady-state control phase of ground orientation. among them:

1) In the rate damping phase, the attitude controller uses the Minus B-dot magnetron law and uses a three-axis magnetic torque device as an actuator to apply a control magnetic moment to damp the pitch axis of the last sub-track application subsystem , The angular velocity of the rolling axis and the deflection axis to achieve attitude control in the rate damping phase.

2) In the steady-state control phase, the attitude controller uses a PD control law with time lag compensation in the pitch loop, using a bias momentum wheel and the three-axis magnetic torque converter as an actuator to apply a control magnetic moment to complete Attitude control of the pitch loop, while eliminating the effects of time lag; the attitude controller uses sliding mode control laws to design switching functions and variable structure control laws in the rolling loop and offset loop, constructing the last sub-track application subsystem Control commands for rolling and yaw circuits.

In the early stage of the last sub-track application subsystem, due to the separation of stars and arrows, there will be a large angular rate of the last sub-track application subsystem, and the last sub-track application subsystem is in a rotating or rolling state. First, the application subsystem of the last sub-stage derailment should be racemized, that is, velocity damping.

At this time, the attitude controller uses the Minus B-dot magnetic control law, and uses a magnetic torque device as an actuator to apply a control magnetic moment to damp the three axes of the last-stage track-keeping application subsystem, namely the pitch axis, the roll axis, Deflect the angular velocity of the axis to achieve attitude control in the rate damping phase.

The rate of change of the magnetic field vector of the last-sub-track application subsystem reflects the angular velocity information of the last-sub-track application subsystem. Under certain conditions, there is a monotonous approximate correspondence between the two. Therefore, The angular velocity of the last-sub-track application subsystem can be damped by using the rate of change of the magnetic field vector under the current system of the last-sub-track application subsystem.

Control the output of the magnetic torque converter according to equation (1)

which is,

Under the action of the Minus B-dot magnetron law determined by equation (1), the kinetic energy of the last sub-stage rail-tracking application subsystem of the last sub-track rail-tracking application subsystem gradually attenuates, that is, the last sub-stage rail-tracking application subsystem The angular rate of each axis of the subsystem will gradually decrease. When the satellite's attitude angular rate decays to the magnitude of the orbital angular velocity, select the appropriate timing to switch the satellite's attitude control mode to the ground-orientation three-axis stable mode.

The main goal of the ground-orientation three-axis stabilization control mode is to keep the three Euler attitude angles of the satellite near zero, and realize the stability of the satellite Z-axis pointing to the ground, which is beneficial to the ground imaging and data communication of remote sensing satellites.

In the above method, the offset momentum wheel is installed in the negative direction of the pitch axis; an implementation structure of the three-axis magnetic torquer includes three independent magnetic rods with the same performance, and the three magnetic rods are respectively along the The X, Y, Z three-axis installation of the last sub-track gauge measuring subsystem.

Offset Momentum Wheel: The Offset Momentum Wheel spins up before the launch of the last sub-track-keeping application subsystem. Once the stars and arrows are separated, the last sub-track-tracking application subsystem can obtain stability along the normal direction of the track And anti-jamming capability; during the entire normal flight phase of the last-stage track-keeping application subsystem, the bias momentum wheel clock remains at the center speed.

Three-axis magnetic torque device: The three-axis magnetic torque device is one of the actively controlled actuators. It uses the magnetic torque generated by the current-carrying coil as the control torque. A magnetic bar is respectively installed on the three inertia main shafts of the last sub-stage track keeping application subsystem, and the direction of the magnetic moment generated by each magnetic bar is parallel to the corresponding axis. By changing the magnitude of the input current of each magnetic bar Within a certain range, the magnitude of the output magnetic moment of each axis can be freely controlled, so that a suitable active magnetic control torque can be provided for the three axes of the last sub-track application subsystem.

In addition, the attitude control method of the last sub-stage track keeping application subsystem also includes an attitude determination process, and attitude determination is a prerequisite for attitude control. The terminal sub-track application subsystem uses the posture information measured by the posture sensor and undergoes appropriate processing to obtain the posture parameters of the terminal sub-track application subsystem's body coordinate system relative to the track coordinate system. The specific process includes:

1) Select the attitude sensor and measure the attitude information of the last sub-track application subsystem;

2) According to the measurement data of the attitude sensor, an attitude determination algorithm is selected for attitude determination.

The accuracy of attitude determination depends on the hardware accuracy of the attitude sensor and the accuracy of the attitude determination algorithm.

Wherein, the attitude sensor includes, but is not limited to, one or more of a sun sensor, a three-axis magnetic torque device, a magnetometer, and a gyro. Specifically, the attitude sensor may include the following:

The sun sensor is a sensitive device used to capture the direction of the sun.

Magnetometer, used to measure the magnetic field vector in the space environment. In the initial stage, there is no posture information of the last sub-tracking application subsystem, and it is necessary to obtain the change of the geomagnetic field vector in the body coordinate system of the last sub-tracking application subsystem by differentiating the measured value of the magnetometer To achieve control.

A gyro is an attitude sensor used to measure the angular velocity of the last sub-track application subsystem relative to inertial space.

These attitude measurement sensors have their own strengths. Table 1 summarizes their respective advantages and disadvantages. Due to the limitation of their respective error sources, these sensors have different accuracy ranges, and their accuracy is generally between 0.0001 ° and 0.3 °.

Table 1 Performance comparison of attitude sensors

The attitude determination algorithm is to process the attitude information measured by the attitude sensor, and filter or estimate the attitude parameters of the satellite through an algorithm:

In this embodiment, starting from actual engineering, a three-axis attitude determination algorithm is mainly used: 1) dual vector attitude determination algorithm; 2) single magnetic vector attitude determination algorithm; 3) extended Kalman filter algorithm (EKF).

Dual-vector attitude determination algorithm: The dual-vector attitude determination algorithm uses the geomagnetic vector B _b and the sun vector S _b in the body coordinate system of the last-stage orbit-keeping application subsystem to compare the geomagnetic vector B _o and the sun in the orbit coordinate system vector S _o, using a simplified dual vector QUEST attitude determination algorithm to determine the attitude of the three-axis stage Sueko left rail applications subsystem. In the illuminated area, if the direction vector of the sun is not parallel to the geomagnetic vector, a dual-vector attitude determination algorithm may be used to determine the attitude of the last-sub-track application subsystem.

Single magnetic vector attitude determination algorithm: The single magnetic vector attitude determination algorithm is an attitude determination algorithm for special scenes. Under the condition that the rolling angle and yaw angle are small angles, the algorithm only needs to use the magnetometer measurement and the geomagnetic field model Can calculate the pitch angle. This algorithm is suitable for the three-axis stability control phase of ground pointing, and the roll angle and yaw angle at this time can be attenuated to a small angle under the action of chapter precession control law.

Extended Kalman filter algorithm (EKF): The extended Kalman filter algorithm uses the Taylor expansion of the nonlinear function and retains the first-order terms, thereby realizing the linearization of the nonlinear function and retaining the first-order accuracy.

The extended Kalman filter algorithm is suitable for scenarios where MEMS gyros and other attitude sensors work together. When in the sun-illuminated area, the solar sensor and magnetometer measurement can be connected to the filter observation link to correct the posture state estimate; when in the shadow area, the solar sensor cannot work, or you can use the magnetometer measurement Information correction attitude estimation state.

The attitude control method of the last sub-level track-keeping application subsystem further includes:

Step 1: The Euler angle method is used to establish the attitude kinematics model. The stellar attitude dynamics equation adopts the 312 rotation method to obtain the attitude kinematics model of the last sub-track application subsystem

Equation (2), ω is the component array of the inertial angular velocity of the last sub-tracking application subsystem in the body coordinate system; ω _x , ω _y , ω _z are the three-axis inertial angular velocity of the last sub-tracking application subsystem;

θ and ψ are three-axis attitude angles, namely roll attitude angle, pitch attitude angle and yaw attitude angle; ω _o is the orbital angular velocity.

In equation (3), I is the inertial matrix of the last sub-track application subsystem; ω is the component array of the inertial angular velocity of the last sub-track application subsystem in the body coordinate system;

Is the differential of the inertial angular velocity; h is the angular momentum of the offset momentum wheel, and the component on the three axes of the body is h = [h _x h _y h _z ] ^T ; T _c is the control torque, and T _d is the disturbance torque.

Given that ω _o is a small quantity, equation (5) is further simplified to

In equations (5) and (6), I _x , I _y , and I _z are the three-axis inertial matrix of the last sub-track-keeping application subsystem;

Is the three-axis attitude angular acceleration, that is, the rolling attitude angular acceleration, the pitch attitude angular acceleration, and the yaw attitude angular acceleration, respectively; h _x , h _y , and h _z are the components of the angular momentum h of the offset momentum wheel on the three axes; T _x , T _y and T _z are the components of the control torque T _c on the three axes.

It can be seen from equation (6) that the pitch loop is decoupled from the roll loop and yaw loop, and the attitude control algorithm of the pitch loop can be designed separately.

1) Design of PD controller with time-lag compensation in pitch loop

The PD control method is a classic control method and has been successfully applied in many satellites.

For the last stage of the rocket, its attitude is constantly spinning and accompanied by a certain nutation in space, and the process of the sensor collecting signals, the calculation processing of the controller and the actuating process of the actuator will all produce time lag. In the past, in order to simplify the design of control methods, people usually ignored the influence of time-delay factors, but a small time-delay will also have a great influence on the control effect. With the fixed-speed bias momentum wheel configuration, it is impossible to provide output torque by adjusting the momentum wheel speed, it is difficult to achieve effective attitude adjustment, and the attitude stability accuracy is not high.

In this embodiment, the design of the PD controller with time-lag compensation in the pitch loop eliminates the effect of time-lag, which is beneficial to improve the attitude control accuracy of the last-stage track-keeping application subsystem, in particular, it can effectively improve the rolling angle and deviation Control accuracy of the angle of flight. It includes: a) Smith predictor; b) Dalin algorithm.

Smith predictor

In the steady-state control phase, the attitude controller adopts a PD control law with Smith time lag compensation in the pitch loop, and a Smith predictor is connected to the attitude controller based on the PD control law to complete the pitch loop. Attitude control.

4, the transfer function of said attitude controller for D (s), i.e., the transfer function of the controlled object actuator is _{^{D o (s) e -τs,}} τ is a pure delay time constant, s is Time variable; the transfer function of the controlled object that does not contain the pure lag part is D _o (s), the transfer function of the controlled object's pure lag part is e ^-τs ; estimated by the attitude controller D (s) and Smith The compensation loop composed of the compensator becomes a pure lag compensator, and the transfer function D '(s) of the pure lag compensator is

After time delay compensation, e- ^τs in equation (8) is outside the closed-loop control loop and does not affect system stability.

Dalin algorithm

In the steady-state control stage, the attitude controller may also use a PD control law with Dalin time-lag compensation in the pitch loop to complete the attitude control of the pitch loop.

2) Rolling / yaw loop sliding mode variable control method

A sliding mode variable control method is used to design the switching function and the variable structure control law, and construct the control instructions of the rolling loop and the yaw loop of the last sub-track application subsystem.

The sliding mode variable control method is widely used in various engineering fields. The main reason is that when the system moves on the sliding mode surface, it is robust against external disturbances and parameter perturbations. Variable structure control is essentially a special type of non-linear control, and its non-linearity appears as a discontinuous control. This control strategy differs from other controls in that the "structure" of the system is not fixed but can be purposefully continuously changed in the dynamic process according to the current state of the system, forcing the system to follow the predetermined "sliding mode" state Trajectory movement, so, also known as variable structure control (VSC) is sliding mode control (SMC), that is, sliding mode variable structure control (SMC), that is, sliding mode variable structure control (VSS). Sliding mode variable structure control has the advantage of not relying on external disturbances and internal parameter changes. By designing an appropriate switching function and variable structure control law, the system can ensure that the system reaches the switching manifold within a limited time, and then realize the sliding mode motion.

Example three:

Simulation example:

The on-orbit flight phase of the last sub-track application subsystem is simulated, and the simulation input conditions are:

a) Running track

Orbit type: Solar synchronous orbit Orbit height: 539km

Orbital inclination: 97.5553deg Orbital eccentricity: 0

b) Satellite quality characteristics

Satellite quality: 8.3 ± 0.5kg Satellite size: 110mm × 231.7mm × 346mm

Satellite inertia: I _xx = 0.088kg · m ² , I _yy = 0.116kg · m ² , I _xx = 0.044kg · m ²

1) B-dot damping simulation

Taking the rate damping stage as an example, the simulation is performed. The specific parameters and simulation results are as follows:

a) Initial posture

Attitude angle: [10; 10; 10] deg Rotation angular velocity: [-3; -3; -3] deg / sec

b) Control parameters

Control period: 1sec, damping gain: 3e5

The simulation results are as follows:

As shown in Figures 5-7, the abscissa is the control period, in seconds; the ordinate is the rotational angular velocity, in deg / sec. The B-dot control magnetron can effectively reduce the rotation angular velocity of each axis of the last-stage track-keeping application subsystem. After 1000s, the rotation angular velocity of each axis basically converges to a smaller range.

As shown in Figures 8 to 10, the abscissa is the control period in seconds; the ordinate is the attitude angle and the unit is deg. B-dot control magnetron can reduce the yaw angle, roll angle, pitch angle is constantly changing.

As shown in Figures 11 to 13, the abscissa is the control period in seconds; the ordinate is the magnetic moment and the unit is Am ² . At the moment of initial orbit entry, the initial rotation angular velocity of the last sub-track keeping application subsystem (simulation) is large, and the output command magnetic moment is large, as the rotation angular velocity of the last sub-track staying application subsystem (simulation) decreases , The magnetic moment output by the control command is continuously decreasing.

2) Simulation of steady state control stage

Taking the steady-state control stage as an example, the simulation is performed. The specific parameters and simulation results are as follows:

a) Initial posture

Attitude angle: [10; 10; 10] deg Rotation angular velocity: [0.0009; 0.0180; 0.003] deg / sec

b) Control parameters

Control period: 1sec Chapter precession damping gain: 3e5

Proportional coefficient of pitch channel: 1.1e-6 Differential coefficient of pitch channel: 1.55e-4

The simulation results are as follows:

In Figures 14-16, the abscissa is the control period in seconds; the ordinate is the rotational angular velocity in deg / sec; in Figures 17-19, the abscissa is the control period in seconds; the ordinate is the attitude Angle, unit is deg; In Figures 20 to 22, the abscissa is the control period, the unit is second; the ordinate is the magnetic moment, the unit is Am ² .

As shown in Figures 14 to 19, the B-dot magnetron law is adopted in the rolling circuit and the yaw circuit. The X-axis and Z-axis rotation angular velocities are kept within 0.005deg / sec, and the Y-axis rotation angular velocity is kept at the orbital angular velocity as In the small neighborhood of the center; the control accuracy of roll angle and yaw angle is 4deg, and the control accuracy of pitch angle is 0.1deg.

Because of the harmful interference input in the control laws of the rolling loop and yaw loop, the control accuracy of the rolling angle and yaw angle is obviously not as high as that of the pitch angle control.

When the time-lag compensation algorithm is used in the pitch loop, other simulation conditions remain unchanged, and the simulation results are as follows:

In Figures 23 to 25, the abscissa is the control period in seconds; the ordinate is the rotation angular velocity in deg / sec; in Figures 26 to 28, the abscissa is the control period in seconds; Angle, unit is deg; In Figures 29 to 31, the abscissa is the control period, the unit is second; the ordinate is the magnetic moment, the unit is Am ² .

Comparing Fig. 17, Fig. 18 with Fig. 26, and Fig. 27, it can be seen that after the time-lag compensation algorithm is adopted in the pitch loop, the control accuracy of the roll angle and the yaw angle can be effectively improved.

The specific embodiments of the present invention have been described in detail above, but they are only used as examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

An attitude control method for the application subsystem of the last sub-track staying track, characterized in that it includes:

After the last sub-tracking application subsystem enters the mission setting track, a setting threshold value of the post-tracking application subsystem's attitude angular rate is pre-stored in the attitude controller, when the attitude angular rate is greater than the attitude controller Within the set threshold, start the rate damping phase, and de-rotate the last sub-stage derailment application subsystem; when the attitude angular rate is less than or equal to the set threshold in the attitude controller, the last sub-stage derailment application The subsystem enters the steady-state control phase of ground orientation;

Among them, in the rate damping phase, the attitude controller uses the Minus B-dot magnetron law, and uses a three-axis magnetic torque device as an actuator to apply a control magnetic moment to damp the pitch axis of the last sub-tracking application subsystem , The angular velocity of the rolling axis and the deflection axis to achieve attitude control in the rate damping phase;

Among them, in the steady state control phase, the attitude controller adopts the PD control law with time lag compensation in the pitch loop, and uses the bias momentum wheel and the three-axis magnetic torque device as the actuator to apply the control magnetic moment to complete Attitude control of the pitch loop, while eliminating the effects of time lag; the attitude controller uses sliding mode control laws to design switching functions and variable structure control laws in the rolling loop and offset loop, constructing the last sub-track application subsystem Control commands for rolling and yaw circuits.
The attitude control method of the final sub-track application subsystem according to claim 1, characterized in that: an implementation structure of the three-axis magnetic torque device includes three independent magnetic rods with the same performance, and the three magnetic rods are respectively along the The X, Y, Z three-axis installation of the last sub-track gauge measurement subsystem is described.
The attitude control method of the final sub-track application subsystem according to claim 1, wherein the three-axis magnetic torque device as a control magnetic moment applied by the actuator is:

which is,

Among them, M is the control magnetic moment applied by the three-axis magnetic torque device, and the three directions of X, Y and Z are [M x M y M z ];
It is the rate of change of the magnetic field vector under the system of the last sub-track-keeping application subsystem. The three directions of X, Y, and Z are [B bx B by B bz ], which are obtained by differential processing from the measured values of the magnetometer respectively ; K is the control gain coefficient, and the three directions of X, Y, and Z are k 1 , k 2 , and k 3 .
The attitude control method of the last sub-track application subsystem of claim 1, wherein the offset momentum wheel is installed in the negative direction of the pitch axis.
The attitude control method of the last sub-track application subsystem according to claim 1, wherein the attitude control method of the last sub-track application subsystem further comprises:

Select an attitude sensor to measure the attitude information of the last sub-track-keeping application subsystem;

Based on the measurement data of the attitude sensor, an attitude determination algorithm is used to determine the attitude.
The attitude control method of the last sub-track-keeping application subsystem according to claim 5, wherein the attitude determination algorithm includes:

When the last sub-stage track keeping application subsystem works in the rate damping stage, the attitude determination algorithm is selected, but not limited to, one or more of a dual vector attitude determination algorithm and a single magnetic vector attitude determination algorithm;

When the last sub-stage track keeping application subsystem works in the steady state control stage, the attitude determination algorithm is selected, but not limited to, one or more of the extended Kalman filtering method and the single magnetic vector attitude determination algorithm.
The attitude control method of the last sub-track application subsystem according to claim 5, wherein the attitude sensor includes, but is not limited to, one of a sun sensor, a three-axis magnetic torque sensor, a magnetometer, and a gyro Kind or several.
The attitude control method of the last sub-track application subsystem according to claim 1, wherein the attitude control method of the last sub-track application subsystem further comprises:

Step 1: Using Euler angle method, the posture kinematics model is established as

Equation (1), ω is the component array of the inertial angular velocity of the last sub-tracking application subsystem in the body coordinate system; ω x , ω y , ω z are the three-axis inertial angular velocity of the last sub-tracking application subsystem;
Is the three-axis attitude angular velocity, that is, the rolling attitude angular velocity, pitch attitude angular velocity and yaw attitude angular velocity, respectively;
θ, ψ three-axis attitude angle, i.e. the angle of roll attitude, pitch attitude angle and yaw attitude angle; ω o is the angular velocity of the track;

Step 2: Ignore the influence of flexible factors, and establish the posture dynamics model of the last sub-track application subsystem as

In equation (2), I is the inertial matrix of the last sub-track application subsystem; ω is the component array of the inertial angular velocity of the last sub-track application subsystem in the body coordinate system;
Is the differential of the inertial angular velocity; h is the angular momentum of the offset momentum wheel, and the component on the three axes of the body is h = [h x h y h z ] T ; T c is the control torque and T d is the disturbance torque;

Step 3: When the last sub-track application subsystem works in the steady-state control stage and the triaxial attitude angular velocity is a small angle, the simplified kinematics model is

The configuration of the offset momentum wheel with a fixed speed in the Y direction of the system is used to simplify the attitude dynamic model as

Given that ω o is a small quantity, equation (4) is further simplified to

In equations (4) and (5), I x , I y , and I z are the three-axis inertial matrix of the last sub-track-keeping application subsystem;
Is the three-axis attitude angular acceleration, that is, the rolling attitude angular acceleration, the pitch attitude angular acceleration, and the yaw attitude angular acceleration, respectively; h x , h y , and h z are the components of the angular momentum h of the offset momentum wheel on the three axes; T x , T y and T z are the components of the control torque T c on the three axes;

Among them, the small angle is less than or equal to 30 °; the pitch circuit is decoupled from the rolling circuit and the yaw circuit.
The attitude control method of the last sub-stage track keeping application subsystem according to claim 1, characterized in that: in the steady-state control stage, the attitude controller adopts a PD control law with Smith delay compensation in the pitch loop, By connecting a Smith predictor to the attitude controller based on the PD control law, the attitude control of the pitch loop is completed, including:

The attitude controller transfer function is D (s), i.e., the transfer function of the controlled object execution mechanism is D o (s) e -τs, τ is a pure delay time constant, s is a time variable; controlled object The transfer function that does not include the pure delay part is D o (s), and the transfer function of the controlled object pure delay part is e -τs ; the compensation loop composed of the attitude controller D (s) and the Smith predictor becomes Pure lag compensator, the transfer function D '(s) of the pure lag compensator is

After compensation, the closed-loop transfer function Φ ’(s) of the system is

In contrast, the closed-loop transfer function Φ (s) of the uncompensated system is

After time-lag compensation, e- τs in equation (7) is outside the closed-loop control loop and does not affect the stability of the system.
The attitude control method of the final sub-track application subsystem according to claim 1, characterized in that, in the steady-state control stage, the attitude controller uses a PD control law with Dalin time-lag compensation in the pitch loop, Complete the attitude control of the pitch loop.