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Peter M. Bainum, Ph.D.
Distinguished Professor Emeritus of Aerospace Engineering
Phone: (202) 806-6612
Email: pbainum@howard.edu
Research Topics
Structural/control optimization of large space structures; control of flexible expendable launch vehicles; formation flying of orbiting satellites
Summary of Recent Research
This work deals with the simultaneous structural/control optimization of a large space structure (LSS) in low Earth orbit (LEO) subject to the gravity-gradient. The objective from the structural viewpoint is to attain a low weight structure satisfying constraints on the first natural frequency, on the side constraints, and on the damping from the control. Simultaneously the optimal control is to be reached for the structure with the same constraints. It is also desired to confirm the possibility to optimize such a structure by taking the damping factor as input from the control designer. The effect of the coupling between the elastic vibration and the pitch attitude motion on the transient response and on the control effort is analyzed. The control system objectives are the elastic vibration suppression and the attitude control (pitch motion). The LSS orbit is assumed to be circular and the motion is confined on the orbital plane. The NEWSUMT-A and the OPT software are integrated with the ORACLS control package to solve the simultaneous optimization problem. NEWSUMT-A stands for a new sequence of unconstrained minimization techniques to reach the structural optimization. While this software implements the indirect optimization approach, the OPT program solves the structural optimization by using the Generalized Reduced Gradient (GRG) methods. ORACLS computational package implements the Linear Quadratic Regulator to optimize the control cost function. One executive program has been developed and implemented to integrate the three software packages to obtain the integrated structural/control optimization. The result shows relevant reduction in the structural weight with respect to the initial given structure. From the control side the control performance and the damping factor is better than that for the initial given structure. The result shows also that in this case it is possible for the control designer to give some input in the structural design.
A strategy for maintaining separation distances between four satellites in a coplanar elliptical orbiting constellation is developed. A possible scientific application of such a system would be in measuring the curl of the Earth's magnetic field by taking simultaneous measurements along the elliptical orbit. The strategy involves maneuvers which would cause small shifts in the direction of the four semi-major axes. With this approach for Keplerian type orbits, the separation distance between adjacent satellites remains within a few percent of the nominal separation distance. Simulations based on MATLAB and the BG-14 orbital propagator (including various perturbations) show that most of the control energy would be used to compensate for these non-Keplerian perturbations. Studies also include techniques for deployment of clusters of spacecraft into elliptical orbit and also strategies for compensating for the Earth’s oblateness (J2 effect) in the design of the orbitals.
Recent Publications
Bainum, P.M. and Duan, X., “Formation Flying and Constellation Station Keeping in Near Circular Orbits,” Actual Problems of Aviation and Aerospace Systems: Processes, Models, Experiment, 1 (17), Vol. 9, 2004, pp. 32-49.
Fonseca, I.M., Bainum, P.M., and Santos, M.C., “CPU Time Consideration for LSS Structural/Control Optimization with Different Degrees of Freedom.” Acta Astronautica, Vol. 54, 2004, pp. 259-266.
Bainum, Peter M., Tan, Zhaozhing and Duan, Xiadong, “Review of Station Keeping Strategies for Elliptically Orbiting Constellations in Along-Track Formation.” Proc. of Eighth Pan-American Congress of Applied Mechanics, Havana, Cuba, January 5-9, 2004, Vol. 10, Ed. by Julian Bravo Castillero, Martin Ostoja, Starzewski and Reinaldo Rodriquez-Ramos, pp. 350-353.
Bainum, Peter M., “Breakwell Memorial Lecture: Review of Astrodynamics 1958-2001 – A Personal Perspective.” Acta Astronautica, Vol. 51, No. 1-9, 2002, pp. 517-526.
Fonseca, Igar M. Bainum, Peter M. and Lourencao, Paulo, T.M., “Structural and Control Optimization of a Space Structure subjected to the Gravity-Gradient Torque.” Acta Astronautica, Vol. 51, No. 10, 2002, pp. 673-681.
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