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Conference Papers-Microwave Propelled Sail
Note: The papers on this website may differ from the published versions, both in format and in content.
Microwave Propelled Sail:
C. T. Abdallah, E. Schamiloglu, K.A. Miller, D. Georgiev, J. Benford and G. Benford and G. Singh,
"Dynamics and Control of Microwave-Propelled Sails",
Proceedings 2001 Space Exploration and Transportation: Journey into the Future, pp. 559-564, Albuquerque, NM, February 2002.
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Abstract: This paper is concerned with the stability of carbon ber sail structures that are being studied in
a series of experiments at the Jet Propulsion Laboratory (JPL) by a team led by Microwave Sciences,
Inc. The passive dynamic stability in the one-dimensional (1-D) case is most easily understood in terms of the xed points of the trajectories for the governing equations of motion. A more elaborate attempt at studying the three-dimensional (3-D) stability of rigid sail con gurations with a distributed mass and accounting for sail spin is also being performed using a code developed at JPL. The simple 1-D
model introduces the possibility of controlling a microwave-propelled sail using various nonlinear control
strategies. This work will be extended in the future to control the full 3-D case. We present results of
studies in both the 1-D and 3-D analyses. In addition to providing guidance to future proof-of-principle
experiments, this work will lead to novel strategies for enabling a feedback power controller to steer a sail to a desired altitude.
E. Schamiloglu, C. T. Abdallah, D. Georgiev, J. Benford and G. Benford,,
"Control of Microwave-Propelled Sails Using Delayed Measurements",
Proceedings of the 3rd IFAC Workshop on Time Delay Systems, pp. 69-72, Santa Fe, NM, Dec. 8-10, 2001.
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Abstract: This paper is concerned with the control of carbon fiber sail structures that are being studied in
a series of experiments at the Jet Propulsion Laboratory (JPL) and at the University of California,
Irvine. The passive dynamic stability in the one-dimensional (1-D) case was studied in an earlier paper
in terms of the fixed points of the trajectories for the governing equations ofmotion. The simple 1-D
model introduced the possibility of controlling a microwave-propelled sail using various nonlinear control
strategies, using both position and velocity measurements. In the current paper, we assume that velocity
measurements are unavailable, and that the position measurements are delayed (due to the finite speed
of light). We then use a novel feedback that employs delayed position measurements only to stabilize
the sail about an equilibrium position. The paper will also contain preliminary results on studying the
stability of the full 3-D sail model, and potential control strategies.
F. Hegeler, M.D. Partridge, E. Schamiloglu,
and C.T. Abdallah,
"Studies of Relativistic Backward-Wave Oscillator Operation in the Cross-Excitation Regime",
IEEE Transactions On Plasma Science, VOL. 28, NO. 3, pp.567-575, June 2000.
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Abstract: We first reported the operation of a relativistic backward-wave oscillator (BWO) in the so-called cross-excitation
regime in 1998. This instability, whose general properties were predicted earlier through numerical studies, resulted from
the use of a particularly shallow rippled-wall waveguide [slow wave structure (SWS)] that was installed in an experiment to
diagnose pulse shortening in a long-pulse electron beam-driven high-power microwave (HPM) source. This SWS was necessary
to accommodate laser interferometry measurements along the SWS during the course of microwave generation. Since those
early experiments, we have studied this regime in greater detail using two different SWS lengths.We have invoked time-frequency
analysis, the smoothed-pseudo Wigner–Ville distribution in particular, to interpret the heterodyned signals of the radiated
power measurements. These recent results are consistent with earlier theoretical predictions for the onset and voltage scaling
for this instability. This paper presents data for a relativistic BWO operating in the single-frequency regime for two axial
modes, operating in the cross-excitation regime, and discusses the interpretation of the data, as well as the methodology used for
its analysis. Although operation in the cross-excitation regime is typically avoided due to its poorer efficiency, it may prove useful
for future HPM effects studies.
E. Chahine, C. T. Abdallah, D. Georgiev, and E. Schamiloglu,
"Microwave-propelled sails and their control",
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Abstract: This paper presents the microwave-propelled sail, its structure, assumptions. We will present its equations
of motion, then we will conduct stability analysis and we will design a controller to make it asymptotically stable.
E. Schamiloglu,G.T. Park, V.S. Souvalian,
C.T. Abdallah, and F. Hegeler,
"Advances in the Control of a "Smart Tube" High Power Backward Wave Oscillator",
IEEE Transactions, pp.852-855, 1999.
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Abstract: Previous accomplishments pertaining to the control of various parameters of an intense
beam-driven relativistic backward wave oscillator (BWO) include maintaining a specified or desired output power over a
determined frequency bandwidth, and maintaining a constant frequency over a wide range of power. This was accomplished
using an iterative learning control (ILC) algorithm that yielded the appropriate input variables for the electron beam,
as well as the appropriate displacement of the slow wave structure from the cutoff neck. A problem of much greater
complexity is the simultaneous control of both frequency and power, involving the independant mapping of both power and
frequency dependance on the two input variables: cathode voltage and slow wave structure displacement. The resultant
two variable system has been successfully implemented and tested for convergence with minimal iterations. In this paper
we present an overview of our "smart tube," its development, and our most recent results.
C. T. Abdallah, W. Yang,
E. Schamiloglu, L. Moreland,
"Identification and control Methods for High Power Electron Beam-Driven Microwave Tubes", pp. 711-716.
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Abstract: The goal of this paper is to introduce some identification and control systems concepts to
the field of high power microwave (HPM) tubes. These concepts are well known to the control systems community, but have not
been fully exploited within the HPM community. The simpler mathematical aproach used is contrasted with the more physical
modeling, using first principles and advocated by experimental results. The paper also reports on a preliminary application
of these ideas to the Sinus-6 electron beam accelerator. We present simlation results which show that a simple nonlinear
model using static neural networks is sufficient to accurately model the input/output behavior of the Sinus-6 driven Backward
wave oscillator (BWO).
C.T. Abdallah, W. Yang,
E. Schamiloglu, and V. Souvalian
"On The Control of a High Power Backward-wave Oscillator Using Quantifier Elimination Methods",
Proceedings of the American Control Conference, pp. 1-2, Albuquerque, NM, June 1997.
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Abstract: This paper presents an experimental/theoretical study of methods to identify and control a
repetitively-pulsed high power microwave source. A neural network was used to model the system and Quantifier Elimination (QE)
theory is used to search for suitable operating conditons.
E. Schamiloglu, C.T. Abdallah,
G.T. Park and V.S. Souvalian,
"Implementation Of A Frequency-Agile, High Power Backward Wave Oscillator",
IEEE Transactions, pp.742-746, 1997.
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Abstract: Recent work at the University of New Mexico (UNM) has demonstrated how finite length effects in
a high power vacuum backward wave oscillator (BWO) can be exploited to achieve frequency agility for constant beam and magnetic field parameters.
This enhanced bandwidth is obtained through the axial displacement of the slow wave structure with respect to the cutoff
neck "inlet" to the electrodynamic system. This paper describes progress on the implementation of this automatic displacement
to facilitate the incorporation of a robust controller, as proposed by Abdallah et al. The purpose of this controller is to demonstrate
a "smart tube" where a variety of objectives, such as i) maximizing the frequency bandwidth for a given constant power output,
ii) maximizing the radiated peak power at a given frequency, or iii) maximizing the beam-to-power conversion efficiency, can be achieved automatically.
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