Research on Tendon Control System for Flexible Space Structures

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1. Studies on the Design of Tendon Control System(1) Output Feedback Control (Low-Authority Control; LAC): A useful method is developed for determining the optimum output feedback gains and moment-arm location for the design of tendon control system for large flexible space structures. The proposed method employs a nonlinear programming technigue to optimize the design parameters so that the closed-loop poles may be placed in the complex plane as close to the desired pole locations as possible.(2) Modal Control by State Feedbacks (High-Authority Control; HAC): Investigated are two design approaches which provide the designed controller with stability robustness and avoid instability due to mode truncation errors (spillovers). One is (a) LAC/HAC design method and the other is (b) the Loop Transfer Recovery (LTR) approach. The effectiveness of the former method is verified by numerical simulations.2. Laboratory Experiment of Tendon Control System for a Flexible BeamThe prototype tendon c … More ontrol system has been built for a flexible beam control experiment in the laboratory. It consists of a pair of moment arms mounted on the beam, an electrodynamic force actuator and a rotating link at the beam root, and tensile cables (tendons) connecting the link with the moment arms. The hardware experiment has been done successfully, which shows the fundamental feasibility of the tendon control system for the active vibration control of highly flexible structures.(1) Modeling and Identification of the Dynamics of the Experimental Tendon Control System: A mathe-matical model of the coupled beam/tendon system dynamics has been constructed with a finite element method(GEM). Included in the modeling are the contributions of gravitational force, axial static load generated by the tension cables, and proportional dampings. The tendon actuator is modeled as an added one-degree-of -freedom vibrating system. The unknown parameters in the FEM model are determined from the measured responses. The result shows satisfying agreement between the theory and the experiment.(2) Direct Velocity Feedback Control Experiment: Velocity feedback control scheme has been applied to the developed tendon control system. Either of the angular velocity of the moment arms or that of the rotating link was fedback to the electrodynamic actuator. The former system caused a closed-loop in-stability due to the dynamics of the tendon actuator, whereas the latter showed a stable control and ef-fective vibration damping. These facts show that the dynamics of the tendon actuator system plays an important role in the control system design. Less