31 May 1996 Application of phase-lock loops to periodic disturbance rejection in smart structures
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This paper presents a simple, effective and economical system capable of suppressing periodic vibration (external or self induced) affecting a structure or payload. The approach used integrates piezoelectric materials/actuators, sensors, and low-cost electronics in a novel way. The key innovation is the use of phase-lock-loops (PLL) and switch capacitor filters (SCF) for the on-line identification, tracking and control of periodic vibration. This method concentrates its control action at those frequencies where periodic vibration is detected. Among the advantages of this approach are: it is conceptually simple, easily expandable and modular; the controller does not rely on a model of the structure, and it only needs some approximate notion of the frequency range where the periodic disturbances are expected to occur; it is robust and can be operated at high gain without loss of stability; it is not significantly affected by the presence of random vibration or sensor noise; and it can be implemented with inexpensive electronics. The effectiveness of this new approach was experimentally evaluated using a test unit consisting of a simple structure, accelerometers and Terfenol-D actuators. The structure was excited by driving one of the actuator with sinusoidal and random signals. The resulting periodic disturbances were measured using the accelerometers. The acceleration signals were passed though a bank of PLLs and associated SCFs to detect the fundamental frequency and harmonics. This information was used to drive another actuator that rejected the original disturbances, and attenuation levels as high as 30 dB were achieved.
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Marcelo C. Algrain, Marcelo C. Algrain, Douglas E. Ehlers, Douglas E. Ehlers, Steven L. Hardt, Steven L. Hardt, } "Application of phase-lock loops to periodic disturbance rejection in smart structures", Proc. SPIE 2715, Smart Structures and Materials 1996: Mathematics and Control in Smart Structures, (31 May 1996); doi: 10.1117/12.240830; https://doi.org/10.1117/12.240830

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