Topic
Frequency response
About: Frequency response is a research topic. Over the lifetime, 25705 publications have been published within this topic receiving 332249 citations.
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TL;DR: In this paper, two sets of aluminum beams were used for this experimental study each set consisted of seven beams, the first set had fixed ends, and the second set was simply supported Cracks were initiated at seven different locations from one end to the other end (along the length of the beam) for each set, with crack depth ratios ranging from 01 d to 07 d (d is the beam depth) in steps of 01, at each crack location.
282 citations
TL;DR: In this paper, a lumped element model of a piezoelectric-driven synthetic jet actuator is presented, where the individual components of a synthetic jet are modeled as elements of an equivalent electrical circuit using conjugate power variables.
Abstract: : This paper presents a lumped element model of a piezoelectric-driven synthetic jet actuator. A synthetic jet, also known as a zero net mass-flux device, uses a vibrating diaphragm to generate an oscillatory flow through a small orifice or slot. In lumped element modeling (LEM), the individual components of a synthetic jet are modeled as elements of an equivalent electrical circuit using conjugate power variables. The frequency response function of the circuit is derived to obtain an expression for Q(sub out)/V(sub AC), the volume flow rate per applied voltage. The circuit is analyzed to provide physical insight into the dependence of the device behavior on geometry and material properties. Methods to estimate the model parameters are discussed, and experimental verification is presented. In addition, the model is used to estimate the performance of two prototypical synthetic jets, and the results are compared with experiment.
279 citations
TL;DR: In this paper, a laser and sunlight driven, fast and large oscillation of cantilevers composed of photoresponsive liquid crystal polymer materials was reported. But the experimental frequency response is accurately described by the calculated natural resonant frequency for a non-damped cantilever.
Abstract: We report on the laser and sunlight driven, fast and large oscillation of cantilevers composed of photoresponsive liquid crystal polymer materials. The oscillation frequency, driven with a focused 100 mW laser of multiple wavelengths (457, 488, 514 nm), is as high as 270 Hz and is shown to be strongly correlated to the physical dimensions of the cantilever. The experimental frequency response is accurately described by the calculated natural resonant frequency for a non-damped cantilever. To further understand the conversion efficiency of light energy to mechanical work in the system, the oscillatory behavior of a 2.7 mm × 0.7 mm × 0.04 mm cantilever was examined at pressures ranging from 1 atm to 0.03 atm. A large increase in amplitude from 110° at STP to 250° at low pressure was observed. A first approximation of the system efficiency was calculated at 0.1%. The large increase in amplitude at low pressure indicates strong hydrodynamic loss and thus, the material efficiency is potentially much greater. Using a simple optical setup, oscillatory behavior was also demonstrated using sunlight. This work indicates the potential for remotely triggered photoactuation of photoresponsive polymer cantilevers from long distances with lasers or focused sunlight.
278 citations
TL;DR: The superiority of the AMNOR criterion over conventional LMS and constrained LMS criteria for reducing noise in speech signals was confirmed in subjective preference tests.
Abstract: This paper introduces a new adaptive microphone-array system for noise reduction (AMNOR system). It is first shown that there exists a tradeoff relationship between reducing the output noise power and reducing the frequency response degradation of a microphone-array to a desired signal. It is then shown that this tradeoff can be controlled by the introduction of a fictitious desired signal. A new optimization criterion is presented which minimizes the output noise power while maintaining the frequency response degradation below some pre-determined value (AMNOR criterion). AMNOR determines an optimal noise reduction filter based on this criterion by controlling the tradeoff utilizing the fictitious desired signal. Experiments on noise reduction processing were carried out in a room with a 0.4-s reverberation time. The superiority of the AMNOR criterion over conventional LMS and constrained LMS criteria for reducing noise in speech signals was confirmed in subjective preference tests. The AMNOR system improved the SNR by more than 15 dB in the 300-3200 Hz range.
278 citations
TL;DR: In this paper, a non-linear first-order reset element (FORE) is used to reduce the feedback loop transmission bandwidth of linear, minimum-phase plants with large parameter uncertainty.
Abstract: Feedback systems containing linear, minimum-phase plants with large parameter uncertainty may be designed to achieve specified performance tolerances over the entire range of parameter uncertainty. The principal ‘cost of feedback’ is in the feedback loop bandwidth, which is generally much larger than that of the system as a whole. This makes the system very sensitive to sensor noise and high-frequency parasitics. It is shown how a non-linear ‘first-order reset element’ (FORE) may be used to drastically decrease the feedback loop transmission bandwidth. One is logically led to FORE by simple, linear feedback frequency response concepts. The paper assumes that the primary design problem is to satisfy quantitative response tolerances to command inputs. However, disturbances at the plant are not neglected, but the specification on such disturbances is in the damping of the step response. An important feature of the non-linear design is that the system response to command inputs is almost exactly that of a lin...
276 citations