Closed‐loop vibration control tests were conducted on a twist‐actuated model helicopter rotor in forward flight. The Active Twist Rotor (ATR) is a four‐bladed, Mach‐scaled, fully articulated rotor, with active blades. The active blades have embedded piezoelectric
active fiber composite actuators that allow direct control of blade twist. The experiments were conducted at the NASA Langley Transonic Dynamics Tunnel. During the tests, the rotor system response characteristics were identified, using linear time‐periodic (LTP) system identification
techniques. Results indicated that the effects of periodicity on the system response are small, and hence time‐invariant control techniques can be used. The control algorithm used is based on the modified T matrix approach, which results in a continuous‐time control law. The
control laws used were designed to reduce both 4P and 1P hub normal shears (the dominant vibration loads) simultaneously. Cyclic twist was used to control the 4P vibration, while collective twist was used to control the 1P vibration. It was found that a single control law could be used successfully
throughout the test envelope (μ = 0.14 to μ = 0.333). At all advance ratios, the1P and 4P vibrations were significantly reduced.
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Document Type: Research Article
Department of Aerospace Engineering, The University of Michigan, Ann Arbor, MI
Publication date: 2005-04-01
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