Tension-aligned structures have been proposed for space-based antenna applications that require high degree of accuracy. This type of structures use compression members to impart tension on the antenna, thus helping to maintain the shape and facilitate disturbance rejection. These structures can be very large and therefore sensitive to low-frequency excitations. In this study, two control strategies are proposed for the purpose of vibration suppression. First, a semi-active control strategy for tension-aligned structures is proposed, based on the concept of stiffness variation by sequential application and removal of constraints. The process funnels vibration energy from low-frequency to high-frequency modes of the structure, where it is dissipated naturally due to internal damping. In this strategy, two methods of stiffness variation were investigated, including: 1) variable stiffness hinges in the panels and 2) variable stiffness elastic bars connecting the panels to the support structure. Two-dimensional and three-dimensional models were built to demonstrate the effectiveness of the control strategy. The second control strategy proposed is an active scheme which uses sensor feedback to do negative work on the system and to suppress vibration. In particular, it employs a sliding mechanism where the constraint force is measured in real time and this information is used as feedback to prescribe the motion of the slider in such a way that the vibration energy is reduced from the structure continuously and directly. The investigation of the sliding mechanism was performed numerically using the model of a nonlinear beam. Practical issues of this control scheme have been considered and measures such as adding a low-pass filter was taken to ease requirements on the control hardware. It has been shown in simulations that these two control strategies are effective mechanisms to remove energy from a vibrating system.To validate the control strategies, an experimental setup was built. A 3.66 meter long aluminum beam was placed on a rigid bench with a tension device applied at one end. A belt-driven actuator carried a slider, which moved axially along the surface of the beam. On the sliding interface, the slider imposed a constraint on the beam to maintain zero transverse displacement. Rotation at the sliding contact point, controlled by an electromagnetic brake, could be fixed instantaneously, or allowed to vary freely. The slider was equipped with strain gauges and an encoder to measure the constraint force from the beam. The sensor data was fed back and processed in real-time by a control algorithm implemented on a DSP board. Different control strategy combinations have been experimented on the system. Results showed that, with light material damping present in the structure, the two control strategies effectively redistributed the vibration energy into the high-frequency modes, where it was dissipated naturally and quickly.
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