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Disturbance Rejection Control for The Green Bank Telescope

Ranka, Trupti
http://orcid.org/0000-0002-6193-0952
http://rave.ohiolink.edu/etdc/view?acc_num=case1459556332

Abstract Details

2016, Doctor of Philosophy, Case Western Reserve University, EECS - System and Control Engineering.
The GBT is a single dish, receiving radio telescope. It is capable of receiving radio waves in the frequency range of 300 MHz to 115 GHz. The off-axis primary reflector of the telescope is 100 meters in diameter. A truss boom (feedarm) extends about 60 meters perpendicular to the primary reflector and is supported at the edge of the reflector. A subreflector is placed at the tip of the feedarm, which directs the focused radio waves from the primary reflector to the radio receivers placed on the feedarm. At high radio frequencies of observation, the uncorrected pointing and tracking errors become limiting factors for making useful scientific observations. The primary reflector and subreflector servo systems need to reduce the pointing and tracking errors due to torque disturbances acting on the system. The overall aim of this research is to redesign the servo control systems such that they are able to give a superior disturbance rejection performance. The 4 contributions of this research are: 1) Verifying the dynamical model of the structure using system identification experiments. 2) The unique reformulation of the extended state observer (ESO) design as a quantitative feedback design problem in frequency domain and splitting the design of the ESO as a feedback observer and a feedforward filter. This formulation gives a more systematic way of designing an ESO as compared to the current technique used for the ESO design. This method is then used to design the ESO based controller for the primary reflector position loop. The ESO based controller provides more than 50% improvement in disturbance rejection in the primary reflector servo loop, as compared to the legacy PID controller. 3) The innovative use of extremum seeking controller (ESC) with a disturbance feedforward signal. We investigate the use of disturbance feedforward with ESC and show that disturbance feedforward improves the speed of the ESC loop by improving the initial condition of the ESC loop and by reducing the magnitude of the error dynamics. 4) The formulation of the subreflector control as an extremum seeking problem, and using the ESC with disturbance feedforward for the subreflector control. This method gives more than 40% improvement in the tracking of a point source against feedarm swaying in wind gusts.
Mario Garcia-Sanz (Advisor)
Vira Chankong (Committee Member)
Sree N. Sreenath (Committee Member)
Christos Papachristou (Committee Member)
121 p.
Astronomy; Electrical Engineering; Systems Science
Robust control, active disturbance rejection control, Extended State Observer, extremum seeking control, large flexible structures, radio telescopes,

Recommended Citations

Citations

  • Ranka, T. (2016). Disturbance Rejection Control for The Green Bank Telescope [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1459556332

    APA Style (7th edition)

  • Ranka, Trupti. Disturbance Rejection Control for The Green Bank Telescope. 2016. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1459556332.

    MLA Style (8th edition)

  • Ranka, Trupti. "Disturbance Rejection Control for The Green Bank Telescope." Doctoral dissertation, Case Western Reserve University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1459556332

    Chicago Manual of Style (17th edition)

case1459556332
608
© 2016, some rights reserved.Creative Commons License Disturbance Rejection Control for The Green Bank Telescope by Trupti Ranka is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.