0191-9067/85 $3.00 + .00 Copyright ® 1985 SUN SAT Energy Council A PRELIMINARY STUDY ON DECENTRALIZED CONTROL OF LARGE-SCALE FLEXIBLE SPS T. KIDA and Y. OHKAMI National Aerospace Laboratory Jindaiji-machi 1880, Chofu Tokyo,Japan Abstract — This preliminary study is intended to investigate the possibility of applying the local decentralized feedback control technique to the SPS attitude/shape control. The controller is implemented by feeding back only the local measurements, and its feedback gains are designed based on the small-size subsystem model. The analyses performed in this paper are concentrated to (1) the total SPS system stability evaluation and (2) the convergence speed estimation, based on the information of an aggregate model. A simple numerical model is introduced to illustrate the design procedure and the stability evaluation results. It is concluded that the major problems of the SPS mission can be attained by the proposed local decentralized control. SPS CONTROL REQUIREMENTS Constructions and operations of Solar Power Satellite (SPS) in orbit have raised many problems in the field of attitude and shape control technologies of Large Space Structures (LSS). The SPS control requirements can be roughly outlined as follows (see Fig. 1). a. Static/Dynamic Structural Shape Control Active control is essentially required to maintain the surface accuracy of the microwave power transmitting antenna and the solar cell structure (1). These large- scale space structures have low modal frequencies (estimated as —0.001 Hz for the solar cell truss structures basic frequency (2)), and therefore dynamical coupling between control efforts and structural vibrations can occur. Static deformations of these structures are also caused by thermal gradients, gravity gradient torques, solar radiation pressures, and so on. h. Pointing Control The microwave transmitting antenna should be maintained to point (the pointing accuracy of — 1 min is required, (1)) the receiving antenna, rectenna, on the ground through 2 DOF gimballing, while the normal line of the solar cell surface is oriented to the sun within approximately 1 deg accuracy. In this situation, the relative rotational motion results in the variation of the total system property, e.g., inertia characteristics of the total space system, or connecting parameters between the antenna and the solar cell structure. Hence, the control system should be designed adaptive or robust to these system structural and parametric variations.
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