This paper presents experimental verification of the active vibration control of a smart cantilever composite beam using a PID controller. In order to prevent negative occurrences in the derivative and integral terms in a PID controller, first-order low-pass filters are implemented in the derivative action and in the feedback of the integral action. The proposed application setup consists of a composite cantilever beam with a fiber-reinforced piezoelectric actuator and strain gage sensors. The beam is modeled using a finite element method based on third-order shear deformation theory. The experiment considers vibration control under periodic excitation and an initial static deflection. A control algorithm was implemented on a PIC32MX440F256H microcontroller. Experimental results corresponding to the proposed PID controller are compared with corresponding results using proportional (P) control, proportional–integral (PI) control and proportional–derivative (PD) control. Experimental results indicate that the proposed PID controller provides 8.93% more damping compared to a PD controller, 14.41% more damping compared to a PI controller and 19.04% more damping compared to a P controller in the case of vibration under periodic excitation. In the case of free vibration control, the proposed PID controller shows better performance (settling time 1.2 s) compared to the PD controller (settling time 1.5 s) and PI controller (settling time 2.5 s).

A novel concept of morphing airfoils, capable of changing camber and thickness, is proposed. A variable airfoil shape, defined by six input parameters, is achieved by allowing the three spinal points (at fixed axial positions) to slide vertically, while the upper and lower surfaces are determined by the lengths of the three corresponding ribs that are perpendicular to the spine. Thus, it is possible to find the most appropriate geometric configuration for a wide range of possible operating conditions often present with contemporary unmanned aerial vehicles. Shape optimizations for different Reynolds numbers and different cost functions are performed by coupling a genetic algorithm with simple panel method flow calculations. The obtained airfoils are presented and compared, whereas the proposed concept is validated by more advanced flow simulations. It appears that improvements in aerodynamic performance of nearly 20% can be expected at Re ranging from 0.05 × 10⁶ to 0.1 × 10⁶. The proposed methodology shows promise and can be applied to different types of lifting surfaces, including wing, tail or propeller blade segments. To check the viability of this method for producing airfoils that can be used in a practical sense, structural analysis of one of the obtained geometries using a simplified 1D finite element method as well as a more detailed 3D analysis are performed. The model is then 3D-printed on a fused deposition modeling (FDM) printer with a polyethylene terephthalate glycol (PETG) filament, and the capability of the airfoil to adequately morph between the two desired geometries is experimentally shown.

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.

The main aim of this paper was to determine the influence of different parameters of winglet design on overall Unmanned Aerial Vehicle (UAV) aerodynamics. Looking from an aerodynamicist's point of view, the main reason for using such wingtip devices is to reduce induced drag component, which noticeably contributes to total drag when flying both in cruising flight and on higher angles of attack at lower speeds. Significant benefits of using winglets on overall aircraft performance include reduced fuel burn, increased maximum range and endurance, and higher cruise altitude. Total drag of a simplified mock-up of an existing tactical UAV was calculated using hybrid approach. Parasite drag was obtained using analytical and semi empirical methods, while the induced drag and the lift in its linear domain were determined using inviscid CFD model based on a 3D vortex lattice method (VLM). Computational analyses were focused on determining the influence of winglet cant angle, root chord length, span, airfoil, and twist angle on lift-to-drag ratio of the UAV. Results obtained for different types of winglets (straight, blended and elliptical) were compared, and the best performing in the prescribed dimensions were the elliptical winglets. Their geometry was further optimized, finally providing an overall lift-to-drag ratio increase of 7% compared to the original UAV design without winglets, which represents quite remarkable improvement.

The ability of flying continuously over prolonged periods of time has become target of numerous research studies performed in recent years in both the fields of civil aviation and unmanned drones. High altitude platform stations are aircrafts that can operate for an extended period of time at altitudes 17 km above sea level and higher. The aim of this paper is to design and optimize a wing for such platforms and computationally investigate its aerodynamic performance. For that purpose, two-objective genetic algorithm, class shape transformation and panel method were combined and used to define different airfoils with the highest lift-to-drag ratio and maximal lift coefficient. Once the most suitable airfoil was chosen, polyhedral half-wing was modeled and its aerodynamic performances were estimated using the CFD approach. Flow simulations of transitional flow at various angles-of-attack were realized in ANSYS FLUENT and various quantitative and qualitative results are presented, such as aerodynamic coefficient curves and flow visualizations. In the end, daily mission of the aircraft is simulated and its energy requirement is estimated. In order to be able to cruise above Serbia in July, an aircraft weighing 150 kg must accumulate 17 kWh of solar energy per day.

The main aim of this paper was to determine the influence of different parameters of winglet design on overall Unmanned Aerial Vehicle (UAV) aerodynamics. Looking from an aerodynamicist's point of view, the main reason for using such wingtip devices is to reduce induced drag component, which noticeably contributes to total drag when flying both in cruising flight and on higher angles of attack at lower speeds. Significant benefits of using winglets on overall aircraft performance include reduced fuel burn, increased maximum range and endurance, and higher cruise altitude. Total drag of a simplified mock-up of an existing tactical UAV was calculated using hybrid approach. Parasite drag was obtained using analytical and semi empirical methods, while the induced drag and the lift in its linear domain were determined using inviscid CFD model based on a 3D vortex lattice method (VLM). Computational analyses were focused on determining the influence of winglet cant angle, root chord length, span, airfoil, and twist angle on lift-to-drag ratio of the UAV. Results obtained for different types of winglets (straight, blended and elliptical) were compared, and the best performing in the prescribed dimensions were the elliptical winglets. Their geometry was further optimized, finally providing an overall lift-to-drag ratio increase of 7% compared to the original UAV design without winglets, which represents quite remarkable improvement.