“…It is worth mentioning that due to the nature of the applied loads, as well as the dynamic properties of the force balance structure, frequency interference can be challenging. 70 This problem has already been attended to by the current authors whose details are available. 70 The experimental investigation has been performed at the robotic laboratory equipped with a subsonic wind tunnel.…”
Section: Validation Proceduresmentioning
confidence: 93%
“…70 This problem has already been attended to by the current authors whose details are available. 70 The experimental investigation has been performed at the robotic laboratory equipped with a subsonic wind tunnel. 71 Figure 9 shows a schematic of the experimental set-up utilized in this study, in which the blockage ratio of the projected frontal area of the rectangular structure and the cross-sectional area of the test section is less than 1%.Figure 9.The schematic of the experimental set-up.…”
A novel integrated aeroelastic model of flapping wings (FWs) undergoing a prescribed rigid body motion is presented. In this respect, the FW nonlinear structural dynamics is enhanced via a newly proposed modification of implicit condensation and expansion (MICE) method that better considers the structural nonlinear effects. In addition, the unsteady aerodynamic model is also an extension of the widely utilized modified strip theory (MST) in which the flexibility effects are accounted for (MST-Flex). The integrated utility of the proposed generalized MICE and MST-Flex is demonstrated to be more realistic for elastic FW flight simulation applications. The prescribed rigid body motion is produced via a servo motor whose dynamics is also considered for the analysis. A special case study is also performed whose combined aeroelastic solution is determined and validated under a sinusoidal flapping motion. To this end, an experimental setup is designed and tested in order to validate the proposed integrated approach for aeroelastic modeling of FWs. There is very good agreement between the numerical and experimental results for elastic FW aerodynamics. It should be noted that the proposed integrated aeroelastic approach is readily adaptable to all kinds of elastic wings with arbitrary geometry and various combination of structural elements.
“…It is worth mentioning that due to the nature of the applied loads, as well as the dynamic properties of the force balance structure, frequency interference can be challenging. 70 This problem has already been attended to by the current authors whose details are available. 70 The experimental investigation has been performed at the robotic laboratory equipped with a subsonic wind tunnel.…”
Section: Validation Proceduresmentioning
confidence: 93%
“…70 This problem has already been attended to by the current authors whose details are available. 70 The experimental investigation has been performed at the robotic laboratory equipped with a subsonic wind tunnel. 71 Figure 9 shows a schematic of the experimental set-up utilized in this study, in which the blockage ratio of the projected frontal area of the rectangular structure and the cross-sectional area of the test section is less than 1%.Figure 9.The schematic of the experimental set-up.…”
A novel integrated aeroelastic model of flapping wings (FWs) undergoing a prescribed rigid body motion is presented. In this respect, the FW nonlinear structural dynamics is enhanced via a newly proposed modification of implicit condensation and expansion (MICE) method that better considers the structural nonlinear effects. In addition, the unsteady aerodynamic model is also an extension of the widely utilized modified strip theory (MST) in which the flexibility effects are accounted for (MST-Flex). The integrated utility of the proposed generalized MICE and MST-Flex is demonstrated to be more realistic for elastic FW flight simulation applications. The prescribed rigid body motion is produced via a servo motor whose dynamics is also considered for the analysis. A special case study is also performed whose combined aeroelastic solution is determined and validated under a sinusoidal flapping motion. To this end, an experimental setup is designed and tested in order to validate the proposed integrated approach for aeroelastic modeling of FWs. There is very good agreement between the numerical and experimental results for elastic FW aerodynamics. It should be noted that the proposed integrated aeroelastic approach is readily adaptable to all kinds of elastic wings with arbitrary geometry and various combination of structural elements.
“…It can be shown that for an ideal strain gauge, the change of the resistance is related to the strain (ε) as shown in Eq. (2) [8,9].…”
Section: Introductionmentioning
confidence: 99%
“…For instance, the accuracy of the printed strain gauge is affected by temperature drift due to the lacking availability of appropriate material [11]. Another parameter affecting the results is how to balance the strain gauges in different force transducers such as dynamometers [8,12].…”
Designing a safe load-carrying component for mechanical structures requires sufficient information related to the distribution of loads, which is applied to the structure. One of the main design criteria is the level of stress. In some test cases, measuring the stress directly becomes very difficult due to a complex geometry for instance. In this case, the measurement of the physical displacement of the structure, which is known as strain (ε) facilitates this procedure. The accurate strain gauges are mostly sensible and several factors can affect the measurement performance. It is obvious that the resistance tolerances and strain that induced during the application of the gauge, generate some initial offset voltage without the presence of forces. In addition, long lead wires can add resistance to the arm of the circuit bridge, which adds an offset error and desensitizes the output of the bridge. Hence, understanding the effects of significant parameters for analyzing the data is considered valuable. In this paper, the influence of the temperature, the length of wires and the set point of forces on the strain measurement are experimentally investigated at three levels. Furthermore, the design of experiment and related tools such as Taguchi and signal to noise ratio are employed to reduce the errors and uncertainty through the measurement process. Noise can be related to controllable factors or uncontrollable factors, which are extraneous factors. Using the Taguchi method assists to provide a better control over the right set of controllable factors only, to determine the significant factors with their optimal levels. The results indicate that the temperature has a maximum contribution to the measurement of the strain with 76.35%, which is followed by the effects of length of wires and the point of application with 7.66% and 6.77%, respectively.
“…They are used to perform structural health monitoring (SHM), which is critical to predict risks by checking the wear status of equipment and infrastructures and the stress that mechanical parts are subject to [4]. Vibration sensors are based on a variety of transducers, ranging from piezoelectric and piezoresistive materials [5], [6], to micro-electro mechanical (MEMS) accelerometers [7], [8], strain gauges [9], fiber optics [10], and variable capacitors [11].…”
This article presents a wireless passive vibration sensor based on harmonic backscattering. The adopted vibration transducer is a commercial piezoelectric cantilever. The cantilever is connected to the gate of an NMOS transistor, which controls the self-bias point of the Schottky diode responsible for the second-harmonic generation. This way, vibrations induce the amplitude modulation of the backscattered second harmonic. A technique is presented to retrieve the vibration information (both acceleration and frequency) from the acquired spectrum. The vibration frequency is computed as the average frequency difference between the carrier and the first sidebands, while the vibration acceleration is encoded in the duty cycle of the amplitude modulation of the backscattered harmonic. In this contribution, we demonstrate for the first time that this information can be retrieved from the magnitude ratio of the first and second sidebands of the acquired spectrum regardless of the tag-to-reader distance. A complete wireless prototype, working at f 0 = 1.5 GHz, is manufactured and tested in a laboratory environment for tag-to-reader distances up to 1.3 m. Despite some sensor limitations, i.e., the nonlinear relationship between the duty cycle and the vibration acceleration and the dependence of the sensor sensitivity on the vibration frequency, excellent results are obtained for vibration frequencies around the natural oscillation frequency of the cantilever (i.e., 130 Hz), and for variable accelerations and distances, which testifies the high sensitivity and the robustness of the proposed solution.
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