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Stochastic Free Vibration Analysis of Pre-twisted Singly Curved Composite Shells
Published in Sudip Dey, Tanmoy Mukhopadhyay, Sondipon Adhikari, Uncertainty Quantification in Laminated Composites, 2018
Sudip Dey, Tanmoy Mukhopadhyay, Sondipon Adhikari
Composite singly curved shells are widely used in various engineering applications. Analyzing the effect of twist angle in such structures is immensely important for applications in turbomachinery blades, wind turbines and various aircraft components. Composite structures are often pretwisted due to design and operational needs such as the wing twist of an aircraft is provided to maintain optimum angle of attack preventing negative lift or thrust and maximizing the aerodynamic efficiency. The production of composite structures is always subjected to large variability due to manufacturing imperfection (both structural and material attributes) and operational factors. It is essential to estimate the probabilistic variability in the dynamic responses to ensure the safety and serviceability conditions.
Divergence of a Lifting Surface
Published in Rama B. Bhat, Principles of Aeroelasticity, 2018
If a torque is applied at the tip of a cantilever airplane wing, there is a corresponding resisting torque set up in the wing that limits the wing twist, measured at the tip. As the external torque is increased, there is a corresponding increase in the resisting torque as well as in the torsional deformation of the wing. For small deflections, the torsional deformation at the wing tip is proportional to the external torque and hence the wing can be considered as a linear torsional spring. Therefore, a simple torsional model of the wing can be developed by considering a linear torsional spring that resists the external torque due to the lift force on a typical section of the wing. Such a simple model is shown in Figures 4.2 and 4.3.
Space Law: Emergent Trends
Published in Ruwantissa I.R. Abeyratne, Frontiers of Aerospace Law, 2017
Ironically, at the same time as the Wright Brothers were perfecting their mechanism, a young building apprentice by the name of Curtiss was working as a member of Alexander Graham Bell’s team of experts conducting flying experiments. Curtiss developed ‘wing flaps’ in the nature of ailerons by using the Wright Brothers’ ‘wing twist’ method and applied for a patent that recognized the wing flap mechanism. By 1915, the wing flap method had obviated the Wrights’ wing twist method and all planes were using it. The Wright Brothers sued Curtiss for infringement of patent in 1909, on the grounds that their method also applied to wing flaps. They won the case.112
Active aeroelastic wing application on a forward swept wing configuration
Published in Engineering Applications of Computational Fluid Mechanics, 2019
Rongrong Xue, Zhengyin Ye, Kun Ye
The control power increment with increased wing flexibility was proved by Pendleton, Bessette, Field, Griffin, and Miller (2000), Pendleton et al. (2007) and Pendleton, Lee, and Wasserman (1992). Multiple control surfaces were mounted on an F-16 Agile Falcon and a stiffness-reduced F/A-18. Control surface deflections were shown to improve beneficial wing torsion under higher dynamic pressure conditions and to eliminate the potential aileron reversal. The tests demonstrated higher control powers caused by smaller control surface inputs and the utility of AAW control laws. The control power and handling requirements at the three highest dynamic pressures were verified to be enough for roll performance by controlling aeroelastic wing twist through AAW technology without differential stabilators.
Robust approximation-free prescribed performance control for nonlinear systems and its application
Published in International Journal of Systems Science, 2018
Ruisheng Sun, Jing Na, Bin Zhu
In practical missile applications, it is essential to design appropriate control schemes to achieve certain control performance under complex flight missions (Barbarino, Bilgen, Ajaj, Friswell, & Inman, 2011). To achieve satisfactory control response, the unsteady aerodynamics and nonlinear flight dynamics with uncertainties and external disturbances corresponding to the environmental variations and shape variations, e.g. the time-varying camber, wing twist and self-adapting wings, should be carefully considered (see Sofla, Meguid, Tan, & Yeo, 2010). In realistic applications, the accurate modelling of such nonlinear missile systems may be difficult, which limits the performance of the control systems (see Obradovic & Subbarao, 2011; Scarciotti & Astolfi, 2014). The initial research results in Li, Sun, Bai, and Liu (2015) only considered the ideal case, where only the plant parameters are assumed to be unknown, while the model structures are precisely known. To relax this assumption, Wang and Zhou (2008) suggested a nonlinear dynamic model by considering the interaction between the motion of morphing swept wings and the missile body. However, in this case, the widely used proportional, integral and differential (PID) control may not be able to obtain satisfactory performance, because the fixed control parameters cannot handle various time-varying dynamics over different operation scenarios (Hu, Li, & Zhang, 2014). To address nonlinear missile systems, several advanced control strategies have been studied to tolerate or even compensate for the modelling uncertainties and external disturbances, e.g. robust controls (Liu, Lu, & Zhong, 2014; Wang, Chen, Lu, & Zhong, 2015), variable structure controls (Liu, 2011), feedback linearisation (FL) controls (Cheng, Wang, Liu, & Tang, 2015), backstepping controls (Lee & Chung, 2012; Lu, Liu, Guo, & Chen, 2015), Lyapunov function controls (LFC) (Pukdeboon & Zinober, 2012), adaptive controls (Xu, Yang, & Pan, 2015; Yu, Zhang, & Fei, 2013) and references therein.