+ Visit NASA.gov + Contact NASA   + Home Collection > NASA  Author > Doherty, Michael J.  Author > Tolson, Robert J.  NASA Center > Langley Research Center  Publication Year > 1991-2000 > 1998  Subject > S-U > Spacecraft Design, Testing And Performance  Availability Options > Online > PDF  Item/Media Type > NASA Report > Contractor Report (CR)  Item/Media Type > Masters Thesis  Note: Start a new navigation search by selecting a link above     Previous Record | Next Record + Back to Results   + Printer Friendly Title: Input Shaping to Reduce Solar Array Structural Vibrations Author(s): Doherty, Michael J.; Tolson, Robert J. Abstract: Structural vibrations induced by actuators can be minimized using input shaping. Input shaping is a feedforward method in which actuator commands are convolved with shaping functions to yield a shaped set of commands. These commands are designed to perform the maneuver while minimizing the residual structural vibration. In this report, input shaping is extended to stepper motor actuators. As a demonstration, an input-shaping technique based on pole-zero cancellation was used to modify the Solar Array Drive Assembly (SADA) actuator commands for the Lewis satellite. A series of impulses were calculated as the ideal SADA output for vibration control. These impulses were then discretized for use by the SADA stepper motor actuator and simulated actuator outputs were used to calculate the structural response. The effectiveness of input shaping is limited by the accuracy of the knowledge of the modal frequencies. Assuming perfect knowledge resulted in significant vibration reduction. Errors of 10 in the modal frequencies caused notably higher levels of vibration. Controller robustness was improved by incorporating additional zeros in the shaping function. The additional zeros did not require increased performance from the actuator. Despite the identification errors, the resulting feedforward controller reduced residual vibrations to the level of the exactly modeled input shaper and well below the baseline cases. These results could be easily applied to many other vibration-sensitive applications involving stepper motor actuators. NASA Center: Langley Research Center Publication Date: Aug. 1998 Document Source: CASI Online Source: View PDF File Document ID: 19980232013 Publication Information: Number of Pages = 134 Report Number: NAS 1.26:208698; NASA/CR-1998-208698 Contract-Grant-Task Number: NCC1-104 Price Code: A07 Keywords: FEEDFORWARD CONTROL; STRUCTURAL VIBRATION; VIBRATION DAMPING; POINTING CONTROL SYSTEMS; SHAPE CONTROL; SOLAR ARRAYS; ACTUATORS; STEPPING MOTORS; INPUT; Accessibility: Unclassified; No Copyright; Unlimited; Publicly available; Updated/Added to NTRS: 2005-08-25 + Back to Top + Sponsored by the NASA Scientific and Technical    Information Program + 2004 Vision for Space Exploration + Freedom of Information Act + NASA Web Privacy Policy and Important Notices + NASA Disclaimers, Copyright Notice,    and Terms and Conditions of Use NASA Official: Calvin Mackey Page Curator: NASA Center for AeroSpace Information (help@sti.nasa.gov) Last Updated: July 5, 2007