ç®Phase 4 aerodynamic moment and gravity gradient moment to achieve attitude control of micro satellite axis Li Taiyu Zhang Yulin College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha 410073 Xiaoweili axis attitude passive control scheme gravity gradient moment provides the squat and roll recovery torque, pneumatic Torque provides yaw and sag recovery torque; through attitude stability analysis and attitude control process dynamic simulation, the results show that the satellite has the advantages of simple structure, high stability, high precision, subject position, attitude control, axis stability, gravity gradient, aerodynamic force, The environmental moments mainly include aerodynamic moments, gravity gradient moments, geomagnetic moments and solar moments, etc., all of which have directionality. Through the reasonable design of the satellite configuration, the above-mentioned environmental torque can be used to realize the passive attitude control of the small satellite axis. Adopting the environmental torque to realize the axis calibration 1 is a passive attitude control system structure. The structure is high, low in cost and low in development cycle, which is very attractive to microsatellites. If the advancement improves the attitude control accuracy of the satellite, it can be applied to the ground-reconnaissance survey satellite, and can also be applied to the satellite group of the formation flight completion task, and the application prospect is broad.
At present, the axis-stabilized satellites that completely adopt passive attitude control are mainly single-turbidity, and the force gradient ladder is also used as the force gradient rod and the offset moving wheel to introduce two kinds of environmental moments to realize the axis loosening posture wave. In addition, Muwen proposed a passive control method for azimuth stabilization of circular low-orbit microsatellite axes using aerodynamic moments and gravity gradient moments. The stability analysis and control process dynamic simulation of the proposed method 2 Weiji running track structure The shape and attitude control scheme is envisaged as the Guardian of the controlled image, which runs on the low trajectory ,13, and requires the axis to loosen the stellar configuration satellite by the gravity rod extension mechanism eddy current damping ball and also serves as the end mass upwind plane and the satellite main body. The shape of the main body of the satellite is a positive prism. Two aerodynamic plates of equal area are protruded from the two side planes of the prism. The two pneumatic plates with the same height of the pneumatic plate and the prism form two windward planes, and the intersection line is the windward edge. The center of mass of the satellite is close to the nucleus, equal to the two windward planes, and the distance from the bottom surface of the prism is also cold. The running rails are welcoming, and the rear poles and the configuration make the aerodynamic torque and The force gradient moments dominate the space environmental moments that the satellites are subjected to, and they can be used to achieve passive attitude control of the satellite. Two upwind planes provide yaw and pitch direction recovery moments; eddy current dampers increase satellite lateral and longitudinal moments of inertia The difference between the gravity rods makes the satellite point to the ground.
3 The satellite attitude control equation takes the reference coordinate system as. In the orbital coordinate system, the origin is å·³1 centroid, and when the satellite is in equilibrium, the body coordinate system coincides with the orbital coordinate system. The Euler angles are respectively 0, where the roll angle is the axis, the bow corresponds to the 7 axis, and the yaw is the 2 axis. The standard system analyzes the aerodynamic moment and the gravity gradient moment of the defending force. The atmosphere with aerodynamic torque higher than 120 can be regarded as a free molecular flow. The calculation of aerodynamic force is quite complicated. It is the surface temperature and material of the satellite. Characteristics, etc. Regarding the influence of ignoring the temperature change, the aerodynamic and aerodynamic moments are calculated by Equation 1; the windward surface is æž³; for the inflow velocity, the aerodynamic moment and the aerodynamic moment are related to the atmospheric density. The density of the upper atmosphere is affected by many factors, such as the peak year of the solar activity and the orbital height of the earth's magnetic field in the valley and the peak angle of the sun's sun. The change is very large, reaching two levels. In this paper, only the short-period changes in atmospheric density associated with the sun's peak angle of the sun are considered. The popularity density model is as follows: 56 angles, respectively, for the satellite's right ascension and red Han, respectively, for the sun's right ascension and red as the atmospheric sun's peak angle plus If there is a peak at 14 o'clock in the place, then enter = 30.
The following analysis analyzes the change of the flow velocity during the movement of the 圮, and generally thinks that the upper atmosphere is. The 5 times of the Earth's rotation angular velocity rotates relative to the inertial space, and the angular velocity direction is parallel to the axis due to the rotation of the atmosphere, so that the incoming flow direction is not the opposite direction of the defending flight. Instead, it is subject to a slight angular deviation. If the satellite orbit is a circular orbit, the unit flow vector is the orbital angular velocity, which is the angular velocity of the atmospheric sling in the orbital squaring system; the orbital inclination is the ascending point. The time-to-flow relative to the satellite's velocity squared value is approximately positive with the satellite counterclockwise rotation angle. If the satellite orbits the yaw axis to reduce the inflow direction, the yaw moment it receives is slightly higher than the small amount. If there is a small degree of rotation of the satellite 1 and 0, and the aerodynamic moment of the satellite is the above analysis, the aerodynamic moment of the satellite should be 3.2 gravity gradient moment field lacking high order small amount, the seven stars are subject to The gravity gradient moment for the 3.3 satellite attitude equation will be analyzed. 1 to the 渤 moment and 1 is the ladder 1 liter. General equation, circular orbital 1. The attitude equation of motion is the damping coefficient. 4 Attitude stability analysis The attitude equation of Qiu Xing can be the projection of the angular velocity vector of the satellite relative orbital coordinate system in the body coordinate system as the direction of the remaining year. The vector form of the array of aerodynamic moments and gravity gradient moments is respectively: 3 is the array of the body coordinate system relative to the orbital coordinate system direction cosine array column and column elements; 6 is the aerodynamic value of the satellite; The distance from the center of the centroid to the centroid is substituted into the equation 1214 and the velocity damping is added. There are 17 points multiplied by the two ends of the equation 15. After 1 integral, there is a system of the main inertia of the star system, with an element and the first element, respectively. The orbital coordinate system 1 axis and the axis unit vector equation 16 The left end of the first term is the kinetic energy of the 1 star and inch track system rotation. The second term is 1 force gradient potential energy, the third term is the centrifugal term and the end is the aerodynamic force. (4) The potential energy is taken as the function ugly at the left end of the equation, which is good for positive and only when the satellite is pointing to the axis to stabilize the equilibrium state. Fortunately, the second and third terms on the right side of Equation 17 shift the equilibrium state of the satellite. If you do not consider them, just first. The value of , is greater than, there is a piece of 0, the system is stable. The right end of Equation 17 is due to the rotation of the atmosphere. The magnitude of the change is large with the increase of the inclination of the orbit. This satellite is more suitable for flying in a small dip orbit.
5 attitude control process simulation analysis speed; damping coefficient 1 =., 01 When the flow direction is the opposite direction of satellite flight, the satellite pressure center is in the body coordinate system 120, know = 0.6931 atmospheric density according to the data of the literature 3, given no throw Under the condition, the maximum and minimum values ​​of the atmospheric density are considered to be the maximum values ​​of the 14-point density at the local point, and the minimum density at the local point is taken as the minimum value. The atmospheric density of the satellite in orbit is given according to Equations 2 and 3. In Equation 2, take 2, and Equation 3 takes 3 to be the solar radio radiation flow rate when the point density is . 12 The upper atmosphere density is the same, the same, the orbital inclination is the degree, the other initial satellite attitude initial value is 0, the satellite experiences the 200008 attitude angle with time. 345 different simulation shapes, the same type of curve generation the same attitude angle From the simulation results, it can be seen from the simulation results that under 0, the yaw attitude angle has a large periodic oscillation with time; as the orbital atmospheric density oscillates around the equilibrium position in the condition 1 pitch attitude; The increase in orbital atmospheric density increases the pitch attitude angle and reduces the angle and tends to a small angle. Under the condition, the rolling attitude angle oscillates near the equilibrium position; as the orbital atmospheric density is large, the amplitude of the oscillation angle of the rolling attitude is increased under the condition of the team, and the oscillation is greatly reduced under the condition.
The yaw attitude deviation is mainly caused by the rotation of the Earth's atmosphere. When the inclination of the orbit is not, the direction of the incoming flow is not in line with the direction of flight of the satellite, but there is a small angle of the angle of the satellite to make periodic changes. The amplitude is proportional to the sinusoid of the orbital inclination, so the yaw attitude angle exists. Periodic oscillation When the orbital atmospheric density is not very large, the satellite yaw direction is not strong against the non-atmospheric rotation disturbance torque, and the yaw attitude angle oscillation amplitude is larger than the Ding angle oscillation amplitude; with the orbital atmospheric density, it is large. The anti-interference torque capability is enhanced, and the yaw attitude angle oscillation amplitude tends to the angle oscillation amplitude. The main interference moments of the satellite pitch direction are the aerodynamic interference moment inertia product interference moment and the geomagnetic interference moment.
When the orbital atmospheric density is not very large, the aerodynamic interference torque is not dominant. With the increase of the orbital atmospheric density, its dominant position becomes more and more obvious, and the aerodynamic underlying torque and the aerodynamic recovery torque are both hooked into the atmospheric density. Proportional, so there will be a phenomenon in Hawthorn 2, when the orbital atmospheric density is not very large, the direction of the torsion is the interference moment and the geomagnetic moment caused by the cross-rotational inertia test. These two disturbance torque phases can cancel the part. Therefore, the 3 conditional roll attitude angle is oscillating near the balance position. As the orbital atmospheric density increases, the nonlinear term in Equation 12 increases. Since the pitch attitude angle tends to be fixed, the rollback report interferes with the force. People, the amplitude of the satellite oscillating angle is increased under the condition that the angle is reduced to the angle, the interference torque in the rolling direction is greatly reduced, and the attitude deviation in the rolling direction is reduced. Under the condition, the attitude of the satellite is greatly improved. The smaller the orbital inclination, the higher the attitude control accuracy of the satellite.
The circular low-orbit micro-satellite axis stabilizes the attitude passive control scheme, the structure is simple and reliable, the anti-interference ability is strong, the attitude control precision is satisfactory, and it is suitable for the satellite 1 Lin Laixing with small dip circular orbit, Pan Keyan compiled. Spacecraft Control Design Guidelines, Volume 2. Beijing Science Press, 1981.
1 PCT, attitude dynamics and control of the satellite under the action of environmental torque. Sun Chengqi translation. Control Engineering, 1985.
3 enjoy, Ye Zonghai. Low Earth Orbiter Space Environment Manual. Beijing National Defense Industry Press, 1996.
4 Tu Shancheng editor. Satellite Attitude Dynamics and Control 1. Beijing Aerospace Press, 1999.
5 Tang Xisheng. Compensation method for the error of the Earth's atmosphere model for precise orbit determination. Beijing Astronomical Journal, 1997, 3836 Su Kefu Duinenko. Orbital spacecraft aerodynamics. Zhang Yanlin translated. Beijing National Defence Industry Press, 1979. Sun Zhaowei, Xu Yuli Gradient Small Satellite Gravity Field Capture (1) Method China's empty call science and technology. 1Jinzhi 4 Brewing Hui Li 1 leg Pan, Qing Li is currently pursuing a Ph.D. in Aerospace Science and Technology from the School of Aerospace and Materials Engineering, National Defense Science and Technology University. He is mainly engaged in the use of ± also magnetic field to control the attitude of tiny satellites and use environmental torque to realize the micro satellite axis. Attitude passive stability control research
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