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Morphing aircraft can alter their aerodynamic configuration to obtain multitask adaptability and improve flight performance. In this paper, we apply the variable sweep concept on a tan-dem-wing micro aerial vehicle (MAV) for multitask adaptability, the two canards of which can undergo backward sweep and the two wings can undergo forward sweep. The...
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... backward sweep angle of the canards and the forward sweep angle of the wings are defined as δ1 and δ2, respectively, as shown in Figure 2. When the MAV morphs from loitering configuration to dashing configuration, δ1 and δ2 increase according to a law that can maintain flying stability. ...
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... Insights in a vast number of available references such as [2][3][4][5][6][7][8][9] support the decision of the authors of this paper to finally adopt the tandem wing (TW) configuration for the new UAV. Namely, in the case of classical concepts, the horizontal tail most often generates negative lift in order to provide proper trim in cruising flight. ...
This paper presents the second stage of a tandem fixed-wing unmanned aerial vehicle (UAV) aerodynamic development. In the initial stage, the UAV was optimized by analyzing its characteristics only in symmetrical flight conditions. Posted requirements were that both wings should produce relevant positive lift, the initial stall must occur on the front wing first, the center of pressure should be close to the center of gravity, and longitudinal static stability should be in the optimum range. Computational fluid dynamic (CFD) analyses were performed, where the applied calculation model was derived from the authors’ previous successful projects. The eighth version TW V8 has satisfied all longitudinal requirements. Lateral-directional CFD analyses of V8 showed that the ratio of the lateral and directional stability at the nominal cruising regime was optimal, but both lateral and directional static stabilities were too high. On further development versions, the lower vertical tail was eliminated, a negative dihedral was implemented on the front wing, and four inverted blended winglets were added. Version TW V14 has largely improved lateral and directional stability characteristics, while their optimum ratio at the cruising regime was preserved. Longitudinal characteristics were also well preserved. Maximum lift coefficient and lift-to-drag ratio were increased, compared to the V8.
... Insights in vast amount of available references such as [2][3][4][5][6][7][8][9] support decision of the authors of this paper to finally adopt the tandem wing (TW) configuration for the new UAV; more detailed explanations considering the key aspects of this decision can be found in [1]. With estimated maximum mass of 400 kg and fuselage length of 3.8 m, it was supposed to be powered by four electric motors mounted on the front and the rear wing, powering four tractor-type propellers. ...
... (www.preprints.org) | NOT PEER-REVIEWED | Posted: 23 January 2024 doi:10.20944/preprints202401.1636.v16 ...
This paper presents the second stage of a tandem fixed wing unmanned aerial vehicle (UAV) aerodynamic development. In the initial stage, the UAV was optimized analyzing its characteristics only in symmetrical flight conditions. Posted requirements were that both wings should produce relevant positive lift, the initial stall must occur on the front wing first, the center of pressure should be close to the center of gravity, while longitudinal static stability should be in the optimum range. Computational fluid dynamics (CFD) analyses were performed, where applied calculation model was derived from the authors’ previous successful projects. The eight version TW V8 has satisfied all longitudinal requirements. Lateral-directional CFD analyses of V8 showed that the ratio of the lateral and directional stability at the nominal cruising regime was optimal, but both lateral and directional static stabilities were too high. On further development versions the lower vertical tail was eliminated, negative dihedral was implemented on the front wing, and four inverted blended winglets were added. Version TW V14 has largely improved lateral and directional stability characteristics, while their optimum ratio at cruising regime was preserved. Longitudinal characteristics were also well preserved. Maximum lift coefficient and lift-to-drag ratio were increased, compared to the V8.
... Moreover, due to the opposite sweeping directions of the canards and the wings, the additional inertia forces and moments can be counteracted during morphing, reducing the coupling between the lateral and longitudinal dynamic. This design allows for the complete replacement of the elevator and aileron and is particularly suitable for the popular tube-launched tandem-wing UAV design [27,28], which has better aerodynamic performance at high speeds and can accomplish multitask adaptability [29]. In this paper, we studied the dynamic characteristics of the morphing process and developed a prototype for flight testing. ...
The current morphing technologies are mostly regarded as auxiliary tools, providing additional control torques to enhance the flight maneuverability of unmanned aerial vehicles (UAVs), and they cannot exist independently of the traditional control surfaces. In this paper, we propose a tandem-wing micro aerial vehicle (MAV) with multiple variable-sweep wings, which can reduce the additional inertia forces and moments and weaken the dynamic coupling between longitudinal and lateral motion while the MAV morphs symmetrically for pitch control or asymmetrically for roll control, thereby flying without the traditional aileron and elevator. First, load experiments were conducted on the MAV to verify the structural strength of the multiple variable sweep wings, and the control moments caused by the morphing of the MAV were presented through numerical simulations. Then, the effects caused by symmetric and asymmetric morphing were investigated via dynamic response simulations based on the Kane dynamic model of the MAV, and the generated additional inertia forces and moments were also analyzed during morphing. Finally, dynamic response experiments and open-loop flight experiments were conducted. The experimental results demonstrated that the morphing mode in this study could weaken the coupling between the longitudinal and lateral dynamics and that it was feasible for attitude control without the traditional aileron and elevator while flying.
... Other types divide the wing into three sections for Z-shaped folding to adapt to different flight attitudes, which has been researched and experimented on by Ivanco [9], Xu [13], Zhou [14] and Guo [15], among others. There are also configurations that alter the sweep angle via folding, such as Zhao [16] and Gao [17]. Each configuration has its unique application scenario. ...
Z-shaped folding wings have the potential to enhance the flight performance of an aircraft, contingent upon its mission requirements. However, the current scope of research on unmanned aerial vehicles (UAVs) with Z-shaped folding wings primarily focuses on the analysis of their folding structure and aeroelasticity-related vibrations. Computational fluid dynamics methods and dynamic meshing are employed to examine the folding process of Z-shaped folding wings. By comparing the steady aerodynamic characteristics of Z-shaped folding wings with those of conventional wings, this investigation explores the dynamic aerodynamic properties of Z-shaped folding wings at varying upward folding speeds. The numerical findings reveal that the folding of Z-shaped folding wings reduces the lift-to-drag ratio, yet simultaneously diminishes the nose-down pitching moment, thereby augmenting maneuverability. Concerning unsteady aerodynamics, the transient lift and drag coefficients of the folded wing initially increase and subsequently decrease as the folding angle increases at small angles of attack. Likewise, the nose-down pitching moment exhibits the same pattern in response to the folding angle. Additionally, the aerodynamic coefficients experience a slight decrease during the initial half of the folding process with increasing folding speed. Once the wing reaches approximately 40°~45° of folding, there is an abrupt change in the transient aerodynamic coefficients. Notably, this abrupt change is delayed with higher folding speeds, eventually converging to similar values across different folding speeds.
... These effects may have significant impacts on aircraft dynamics. In [8][9][10], open-loop simulations of the morphing aircraft were performed to verify the effect of the wing transition process, and the results showed that the speed, height, and pitch angle of the morphing aircraft are greatly changed due to morphing. The effect of inertial forces and moments during the morphing of the longitudinal model of a morphing aircraft was investigated in [11], and the results showed that the inertial forces and moments that include the rate terms have very little effect on the dynamics of the morphing aircraft. ...
This work investigates the short-term dynamics caused by shape changes of morphing aircraft. We select a symmetric variable sweep morphing aircraft as the object of study and establish a six-degree-of-freedom multi-loop cascade model, and the coupling between derivative terms is eliminated by matrix transformation. Considering that the change in aerodynamic shape significantly affects the aerodynamic forces of the aircraft in a short period of time, and the variation in mass distribution generates additional aerodynamic forces and moments, we analyze the effects of these factors on the dynamic characteristics of the aircraft based on the open-loop response starting from the steady-state flight conditions. In addition, we analyze the improvement in maneuvering performance brought by morphing as an additional control input. We apply reachable set theory to multi-loop equations of motion and use the size of the reachable set to measure the maneuverability of aircraft. The results confirm that morphing can effectively improve the maneuverability of the aircraft.
... Morphing brings parametric time-varying effects and additional control degrees of freedom, which pose a challenge to the design of flight control systems. In the current research on the control of morphing aircraft, most of the studies focus on the design of control laws to maintain the system's stability and eliminate the time-varying effects and disturbances caused by morphing [7][8][9][10][11][12], for a predetermined morphing process. However, there are few works that regard morphing as a control input, and such works can be divided into two categories according to their objectives of morphing. ...
This work develops a morphing decision strategy to optimize the cruising efficiency for a variable-sweep morphing aircraft, and a simple and practical guidance and control system is given as well. They can work in tandem to accomplish a cruise mission effectively. To make the morphing decision accurately, we take into account the equilibrium equations of forces; the variations in airspeed, altitude, and mass and the optimal configurations for different cruise conditions are solved based on the nonlinear programming method with the objective of minimum engine thrust. Considering that a large amount of computational resources are required to solve the nonlinear programming problems, we establish an offline database of the optimal configurations and design a database-based online morphing decision process. In addition, the proposed morphing decision strategy includes an anti-disturbance mechanism, which ensures that the optimal configuration can be given accurately without chattering under fluctuating airspeed measurements. Comparative results from the simulations finally validate the effectiveness of the proposed strategy.
... Weaver-Rosen et al. [6] used parameter optimization techniques to optimize the curved deformed wings used in light aircraft. In the aspect of folding wing scheme design, Gao et al. [7] applied a variable sweep angle scheme to tandem wing MAV to achieve multi-mission adaptability. Geva et al. [8] proposed a new concept of a morphing wing aircraft that could change between two different working points, improving the endurance of UAVs. ...
Considering the deployment characteristics of the folding wing, this paper proposed three deployment modes, synchronous deployment, fixed-axis–non-fixed-axis stepwise deployment, and non-fixed-axis–fixed-axis stepwise deployment, to obtain the optimal deployment scheme of the orthogonal biaxial folding wing of Unmanned Aerial Vehicles (UAVs) at different airspeeds. On this basis, combined with the folding wing deployment action, the Lagrange method was used to establish the aerodynamic model of the folding wing, and the Fluent simulation software was used to simulate the aerodynamic simulation of multiple deployment modes of the orthogonal biaxial folding wing, which analyze the influence of the UAV deployment mode and airspeed towards the driving torque of the folding wing. Based on the driving moment of the folding wing, the optimal deployment mode at different airspeeds was obtained. The comparison of simulation results shows that when the airspeed is less than 40 m/s, the optimal deployment mode is synchronous deployment. When the airspeed is greater than or equal to 40 m/s, the optimal deployment mode is non-fixed-axis–fixed-axis stepwise deployment. The accuracy of the folding wing aerodynamics model can be proven according to the comparison of the simulation results with the theoretical results.
