Warning: include(/home/content/m/p/i/mpittelkau/html/includes/PEAR/login.php) [function.include]: failed to open stream: No such file or directory in /home/content/01/2468701/html/index.php on line 16

Warning: include() [function.include]: Failed opening '/home/content/m/p/i/mpittelkau/html/includes/PEAR/login.php' for inclusion (include_path='.:/usr/local/php5/lib/php') in /home/content/01/2468701/html/index.php on line 16

Warning: include(/home/content/m/p/i/mpittelkau/html/templates/fooloo/utf.php) [function.include]: failed to open stream: No such file or directory in /home/content/01/2468701/html/index.php on line 19

Warning: include() [function.include]: Failed opening '/home/content/m/p/i/mpittelkau/html/templates/fooloo/utf.php' for inclusion (include_path='.:/usr/local/php5/lib/php') in /home/content/01/2468701/html/index.php on line 19

Warning: include(/home/content/m/p/i/mpittelkau/html/includes/error.php) [function.include]: failed to open stream: No such file or directory in /home/content/01/2468701/html/index.php on line 22

Warning: include() [function.include]: Failed opening '/home/content/m/p/i/mpittelkau/html/includes/error.php' for inclusion (include_path='.:/usr/local/php5/lib/php') in /home/content/01/2468701/html/index.php on line 22

Warning: include(/home/content/m/p/i/mpittelkau/html/modules/mod_related_items/tmpl/gallery.php) [function.include]: failed to open stream: No such file or directory in /home/content/01/2468701/html/index.php on line 25

Warning: include() [function.include]: Failed opening '/home/content/m/p/i/mpittelkau/html/modules/mod_related_items/tmpl/gallery.php' for inclusion (include_path='.:/usr/local/php5/lib/php') in /home/content/01/2468701/html/index.php on line 25
Control-Structure Interaction (CSI) Analysis Tool

Aerospace Control Systems

Spacecraft GNC Systems Engineering

 
Control-Structure Interaction (CSI) Analysis Tool PDF Print E-mail
Article Index
Control-Structure Interaction (CSI) Analysis Tool
Pointing Error Analysis
All Pages

The CSI Analysis Tool is used to evaluate control-structure interaction and control system stability, and to compute the pointing error response of spacecraft and optical payloads to disturbances and sensor noise. This Matlab tool models the rigid-body and flexible structure, attitude sensors and gyros, reaction wheels, the steady-state attitude determination (Kalman) filter, a three-axis PID controller, structural mode filters, payload dynamics (including line-of-sight stabilizers), and time delays. The component transfer functions are interconnected to form system matrices, from which the open-loop and closed-loop frequency response to inputs and disturbances, and the covariance response to noise can be evaluated.

The algorithms incorporated into the CSI tool were previously applied to the STEREO and MESSENGER spacecraft, and was used to investigate and resolve a control-structure interaction problem on the TIMED spacecraft. The frequency response plots below were generated from the structural model for the MESSENGER spacecraft. These plots show the frequency response from the spin axis of reaction wheel 1 to the four IMU sense axes and to the Mercury Dual Imaging System (MDIS) payload interface.

Stability margins are evaluated by breaking the feedback loop at various locations, including the star trackers, IMU, and reaction wheels. This is done for single channels and multiple channels. The frequency response is evaluated by using a phase-gain tracker so that modal peaks are not missed, which yields accurate structural mode gain margins and peak response in attitude and rate. (The frequencies at the modal peaks are known also from the modes and modal dampings in the structural model.) In the case of phase stabilization, a time-delay margin is appropriate and can be evaluated.

Because of variations in control system designs amongst various spacecraft, this tool generally usually requires minor customization for each spacecraft. However, the modular structure of the Matlab software makes this a relatively easy task. The tool is not limited to three-axis attitude control systems; the same approach can be applied to other types of control systems.

Response from wheel 1 to IMUClosed-loop wheel 1 to MDISClosed-loop wheel 1 to MDIS with structural mode filter