航天器姿态控制

A major drawback ---- complexity number of failure points.
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increases the
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Mariner 10
4.Solar sails
Produce thrust as a reaction force induced by reflecting incident light Make small attitude control and velocity adjustments.
Solar sails
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Thruster s
Momentum wheels Control moment gyros
Solar sails
Work together in one spacecraft
Complete the control task
Summary
Control information
Definition
· Installed in a spacecraft · Processes various information for use in controlling the object and its on-board systems and checking the activity of the crew and on-board instrumentation.
5.Electronic digital computers/ hybrid computing systems
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On-Board Computer
What to do ?
actuators
Picture1 Thrusters
Picture2 Momentum wheels
Some common attitude sensor
Star tracker · Measures the positions of stars using photocells or a camera. · One of the most precise attitude sensors
Gyroscopes · Sense rotation in threedimensional space without reliance on the observation of external objects.
Some common attitude sensor
Magnetometer ·Senses magnetic field strength and direction. ·Sensed field strength and direction is compared to a map of the earth magnetic field stored in the memory of an on-board or ground-based guidance computer.
Attitude sensor
Actuators
On-Board Computer
一 Attitude sensor
Attitude sensor
Relative attitude sensors
Absolute attitude sensors
Many sensors generate outputs that reflect the rate of change in attitude.
Attitude control system
演讲人： 演讲人：闫蓉 资料收集：李雅潇， 资料收集：李雅潇，严骅 PPT制作 王克 制作:王克 制作 王克z
Attitude control system
On-Board Computer Actuators Spacecraft Dynamics
Attitude sensor
Thrus ters
Controll er
Solar sails
Actua tors
Momen tum wheels
CMG
Sun sens or Star track er Magn etom eter
Control moment
senor
Gyro scop es
Spacecraft
Attitude information
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2.Momentum wheels Electric motor driven rotors made to spin in the direction to re-orient the vehicle. Suspended on magnetic bearings to avoid friction and breakdown problems. A minimum of two must be used, with additional units providing single failure protection.
Attitude information
Thank you
Brain-On-Board Computer
Character
1.Micro miniature integrated circuits 2.Weigh from 1 to a few dozen kg 3.high operational speed and reliability 4. electrical power ranges from a few dozen to hundreds of watts of
Comparison
Merits：1.Strong signal source 2.clear-cut 3.Low power ： consumption, light quality Demerit：having a shadow area ： Merits：1. High precision 2. View not restricted 3. no orbit ： influence Demerit：1. Weak signal 2. Complex structure, high ： cost Merits：1. Strong Autonomy 2. no orbit influence 3. high ： precision in the limited time Demerit：Easy to drift ： Merits：1. Low cost, low power consumption 2. High sensitivity ： to low orbit satellites Demerit：great Influence on orbit ：
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3.Control Moment Gyros
Spin at constant speed, mounted on gimbals to provide attitude control.
The maximum torque exerted by a CMG is greater than a momentum wheel Making it better suited to large spacecraft.
This class of sensors sense the position or orientation of fields, objects or other phenomena outside the spacecraft.
Some common attitude sensor
Sun sensor ·Senses the direction to the sun. ·Either quite simple or complex depending on mission requirements. Horizon sensor ·Optical instrument that detects light from the ‘limb’ of the Earth‘s atmosphere, ·Provides orientation with respect to the earth about two orthogonal axes.
Picture3 CMG
Picture4 solar sails
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1.Thrusters
Organized as a Reaction control system to provide triaxial stabilization Limitations： fuel usage, engine wear, and cycles of the control valves. The fuel efficiency ： determined by its specific impulse and the smallest torque impulse it can provide
Control moment gyros Merits:1. More precise 2. provide triaxial stabilization Demerit:1.take a long time 2. fuel limitation Merits:1. give precise control 2. can use Solar Energy Demerit: bearing friction and breakdown problems Merits:1.Suit to large spacecraft Demerit:1.additional complexity 2. more expensive Merits:1.Use green energy 2. make small attitude control and velocity adjustments 3. save large amounts of fuel
Save large amounts of fuel on a long-duration mission by producing control moments without fuel expenditure.
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Comparison Thrusters Momentum wheels
Sun sensor
Star tracker
Gyroscopes
Magnetometer
Sun sensor
Speed
Star tracker
Spac ecraft
Magneto meter
Acceleration
On-Board Computer
Gyrosco pes
Location
Brain-On-Board Computer