l9_acs - Attitude Determination and Control Attitude (ADCS)...

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Attitude Determination and Control Attitude Determination and Control (ADCS) (ADCS) Olivier L. de Olivier L. de Weck Weck Department of Aeronautics and Astronautics Department of Aeronautics and Astronautics Massachusetts Institute of Technology Massachusetts Institute of Technology 16.684 Space Systems Product Development 16.684 Space Systems Product Development Spring 2001 Spring 2001
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ADCS Motivation ADCS Motivation ± Motivation In order to point and slew optical systems, spacecraft attitude control provides coarse pointing while optics control provides fine pointing ± Spacecraft Control Spacecraft Stabilization Spin Stabilization Gravity Gradient Three-Axis Control Formation Flight Actuators Reaction Wheel Assemblies (RWAs) Control Moment Gyros (CMGs) Magnetic Torque Rods Thrusters Sensors: GPS, star trackers, limb sensors, rate gyros, inertial measurement units Control Laws ± Spacecraft Slew Maneuvers Euler Angles Quaternions Key Question: What are the pointing requirements for satellite ? NEED expendable propellant: On-board fuel often determines life Failing gyros are critical (e.g. HST)
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Outline Outline ± Definitions and Terminology ± Coordinate Systems and Mathematical Attitude Representations ± Rigid Body Dynamics ± Disturbance Torques in Space ± Passive Attitude Control Schemes ± Actuators ± Sensors ± Active Attitude Control Concepts ± ADCS Performance and Stability Measures ± Estimation and Filtering in Attitude Determination ± Maneuvers ± Other System Consideration, Control/Structure interaction ± Technological Trends and Advanced Concepts
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Opening Remarks Opening Remarks ± Nearly all ADCS Design and Performance can be viewed in terms of RIGID BODY dynamics ± Typically a Major spacecraft system ± For large, light-weight structures with low fundamental frequencies the flexibility needs to be taken into account ± ADCS requirements often drive overall S/C design ± Components are cumbersome, massive and power-consuming ± Field-of-View requirements and specific orientation are key ± Design, analysis and testing are typically the most challenging of all subsystems with the exception of payload design ± Need a true “systems orientation” to be successful at designing and implementing an ADCS
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Terminology Terminology ATTITUDE ATTITUDE : Orientation of a defined spacecraft body coordinate system with respect to a defined external frame (GCI,HCI) ATTITUDE ATTITUDE DETERMINATION: DETERMINATION: Real-Time or Post-Facto knowledge, within a given tolerance, of the spacecraft attitude ATTITUDE CONTROL: ATTITUDE CONTROL: Maintenance of a desired, specified attitude within a given tolerance ATTITUDE ERROR: ATTITUDE ERROR: “Low Frequency” spacecraft misalignment; usually the intended topic of attitude control ATTITUDE JITTER: ATTITUDE JITTER: “High Frequency” spacecraft misalignment; usually ignored by ADCS; reduced by good design or fine pointing/optical control.
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Pointing Control Definitions
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l9_acs - Attitude Determination and Control Attitude (ADCS)...

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