Personal aerial vehicles, an innovative transport mode to bridge the niche between scheduled airliners and ground transport, are seen by aviation researchers and engineers as a solution to provide ...fast urban on-demand mobility. This paper reviews recent research efforts on the personal aerial vehicle (PAV), with a focus on the US and Europe led research activities. As an extension of the programmatic level overview, several enabling technologies, such as vertical/short take-off and landing (V/STOL), automation, distributed electric propulsion, which might promote the deployment of PAVs, are introduced and discussed. Despite the dramatic innovation in PAV concept development and related technologies, some challenging issues remain, especially safety, infrastructure and public acceptance. As such, further efforts by many stakeholders are required to enable the real implementation and application of PAVs.
VTOL (Vertical Take-Off and Landing) capabilities are desired features of both UAVs (Unmanned Aerial Vehicles) and MAVs (Manned Aerial Vehicles) on condition that a comparable flight performance is ...achieved. VTOL is not only a very suitable technology for UAVs due to the convenience and concealment mission requirements of UAVs, but also very important for both military and civil MAVs due to the advantages of less or even no dependency on airports/air fields. As such, it is necessary to study and compare the VTOL technology of MAVs and UAVs at the same time. This paper highlights the major VTOL technologies and the representing aircraft configurations. The recent VTOL projects in the US are reviewed and compared to give insight into the technological diversities, application opportunities as well as the future development trend for urban air mobility. Then, an intuitive summary and comparison of famous projects and models has been made. Based on the above research, challenges and constraints of VTOL aircraft are summarized. As a supplement to the review of VTOL technologies, the current research activities on short takeoff and landing technologies via active flow control for large commercial aircraft in Europe is also reviewed. At the end, based on the above analysis, this paper points out the future development direction of VTOL vehicles.
In this paper, an adaptive-estimate-incremental nonlinear dynamic inverse (AE-INDI) flight control method is proposed to address the issue of inaccurate angular acceleration signals in the thrust ...vector control of vertical/short takeoff and landing (V/STOL) aircraft. First, considering the change of center of gravity (CG) caused by aircraft structure transformation, a model for the deflection of a three-bearing swivel duct nozzle is established. This model corrects the equations for the aircraft's moment of inertia and angular rate under CG changes. Second, to account for modeling uncertainty and sensor noise, the angular acceleration is estimated by using the aircraft's actuator information and known states. The uncertainty is then compensated for using adaptive techniques. Finally, a stability analysis is performed based on Lyapunov theory to prove the robustness of the control method. Simulation results show that the proposed controller effectively mitigates interference from model uncertainty, stabilizes affected states within 2 s, weakens the effect of unfavorable sensor noise, and reduces the angular rate noise variance by 77.63%, thus verifying the effectiveness and robustness of the control method.
Bypass dual throat nozzle (BDTN) is a new kind of fluidic thrust vectoring nozzle. Based on the excellent performance of BDTN, a short takeoff and landing (STOL) exhaust system as a substitute for ...the complex tilt rotor is investigated. The STOL exhaust system consists of a downward-bending transition part and a BDTN part. As the thrust vectoring angle reaches more than 35° in a separate BDTN, the transition part enables the actual thrust vectoring angle to reach a maximum of over 70° in STOL mode. In cruise mode, thrust vectoring effect of BDTN compensates the inherent deflection angle of the transition part, the thrust vectoring angle reaches nearly 0°. The transition part is designed with three area-laws and two centerline-laws. Results indicate that centerline-law II leads to less total pressure distortion than centreline-law I. Area-law B is the best area-law since it leads to the moderate change rate of cross-section, it makes the total pressure distribution at the outlet of the transition part more uniform. Then, the integrated STOL exhaust system is investigated, the performances are presented. The thrust direction can be changed by controlling two valves in BDTN, the redundant tilting mechanical structure of traditional tilt rotors is replaced by this way, the structural weight is reduced, and flight safety improves. Finally, the best configuration is selected according to the results of the numerical investigation, and the thrust coefficient is more than 0.920 in STOL and cruise mode. The thrust vectoring angle is -73.37° in STOL mode, and it's -1.81° in cruise mode. The design satisfies the basic requirements for STOL and cruising flight. Hence, the STOL exhaust system is worthy of further study.
In this manuscript, we consider a (3+1)-dimensional Sharma-Tasso-Olver-like (STOL) model, which can be used to describe dispersive wave phenomena in optics, plasmas, quantum physics, and others. ...Based on the simplified Hirota approach, the n-soliton solutions are obtained. We observe that the collisions are non-elastic fusion or fission phenomena where some kink waves disappear due to soliton fusion, or a single kink wave splits into more kink waves due to soliton fusion. We derive kinky-lump breather, combo line kink and kinky-lump breather, and a pair of kinky-lump breather wave solutions that degenerate from two-, three- and four-solitons respectively by choosing complex conjugate values involving free parameters. Moreover, we demonstrate a few new collisions of the Jacobi elliptic sine function with one soliton, and a periodic cosine function which provides kinky-periodic waves and double-periodic waves. All special properties of those collision solutions are illustrated with the 3D, density and contour plots.
•We consider (3+1)-dimensional Sharma-Tasso-Olver-like model.•The solitons, periodic, Jacobi elliptic functions and its interactions are obtained.•We observed the interactions as non-elastic fusion or fission phenomena.•The solutions are illustrated with the 3D, density and contour plots.
Distributed Electric Propulsion (DEP) aircraft use multiple electric motors to drive the propulsors, which gives potential benefits to aerodynamic-propulsion interaction. To investigate and quantify ...the aerodynamic-propulsion interaction effect of the wing section, we built a DEP demonstrator with 24 “high-lift” Electric Ducted Fans (EDFs) distributed along the wing’s trailing edge. This paper explores and compares the aero-propulsion coupling characteristics under various upstream speed, throttle, and EDF mounting surface deflection angles using a series of wind tunnel tests. We compare various lift-augmentation power conditions to the clean configuration without propulsion unit under the experiment condition of 15–25 m/s freestream flow and angles of attack from −4° to 16°. The comparison of computational results to the experimental results verifies the effectiveness of the computational fluid dynamic analysis method and the modeling method for the DEP configuration. The results show that the EDFs can produce significant lift increment and drag reduction simultaneously, which is accordant with the potential benefit of Boundary Layer Ingestion (BLI) at low airspeed.
The core of the short takeoff and landing problem in thrust-vectoring V/STOL vehicles is the tilt angle control of the thrust vector nozzles. This work resolves it by figuring out the optimal tilt ...angle time history with optimization methods. Since the optimization process is constrained by the transition corridor of the vehicle and the mission requirements, the transition corridor is firstly established by the AES theory with the longitudinal model of the V/STOL protype, where the jet-induced effect of the 3BSD nozzle and the lift fan are especially considered. In addition, the control redundancy caused by the multiple physical control actuators is addressed by a suitable control allocation and flight-mode-based control strategy, which ensures a smooth conversion. By establishing appropriate mission references and optimization constraints, the optimal control strategy and the corresponding transition process are obtained, based on the direct inverse and SQP algorithms.
Enhancement in the aerodynamic performance of wings and airfoils is very notable when Active Flow Control (AFC) is applied to Short Take-off and Landing aircraft (STOL). The present numerical study ...shows the application of steady, pulsed and synthetic tangential jets applied to the plain flap shoulder of a modified NASA Trapezoidal Wing. Pulsed jets are modeled by sinusoidal and square waveforms while synthetic jets are modeled only by pure sine waveform. The freestream airflow conditions are Mach number equal to 0.2 and Reynolds number equal to 4.3 million based on the mean aerodynamic chord. The presented simulations are two-dimensional and based on RANS for steady jet cases and URANS for pulsed and synthetic cases, compiled with the open-source suite SU2 and adapted for time varying boundary conditions. Numerical results for modified configurations based on the same baseline wing profile considering different leading edges, jet slot height, flap position, blowing mass flow, type and frequency of the jets are presented. Curves of pressure coefficient distribution revealed a substantial influence upstream of the AFC, around the slat and main element. The jet slot height analysis showed that the lift gain is also influenced by the slot size due to the change of the local flow velocity considering the same blowing momentum coefficient. Regarding the jet frequency, no significant differences on the lift coefficients were found between the reduced frequencies F+ equal to 1 and 2. Results of aerodynamic loads showed an improved lift coefficient in relation to the baseline airfoil when pulsed and steady jets are employed. Pulsed jets under square waveform were effective even at high deflected flap condition at 50°, with a significant gain in the lift coefficient of 36%, in relation to the uncontrolled case, combined with a drag reduction of 20%, and a decrease in mass flow up to 49% in relation to the steady jet for the same lift gain. Although sine and square waveform results presented similar improvements for lift, the drag is around 15% higher for the former. When compared with the steady jet case, the mass flow reduction is 36% for the sinewave. Synthetic jets with zero-net-mass-flux proved superior to the baseline conventional multi-element airfoil only with deployed flap at 50°, where a modest lift improvement of 5% was observed.
A novel actuator disk model (ADM) coupled with lifting-line theory is proposed in this paper. Several virtual planform blades are placed on a disk plane with a constant azimuthal interval, and the ...lifting-line theory is applied to each blade to predict the effective angle of attack. The proposed model considers the local lift and drag forces acting on disk surface cells by interpolating the predicted effective angle of attack with various azimuth angles to the actuator disk plane; therefore, the proposed model considers individual blade tip vortices without tip loss functions. Experimental data for hover and forward flight rotors are used to validate the proposed model. For hovering flight, sectional thrust based on collective pitch angles predicted by the modified ADM was similar to that obtained in the experiments. For forward flight, the inflow above the rotor estimated by the proposed ADM was similar to that obtained in the experiments and by using other numerical methods. Thus, the developed ADM can be used for rotor performance analysis under the main flight conditions of V/STOL.
