Ducted Fan Unmanned Aerial Vehicle Research Articles

Compound Learning-Based Model Predictive Control Approach for Ducted-Fan Aerial Vehicles.

Designing an efficient learning-based model predictive control (MPC) framework for ducted-fan unmanned aerial vehicles (DFUAVs) is a difficult task due to several factors involving uncertain dynamics, coupled motion, and unorthodox aerodynamic configuration. Existing control techniques are either developed from largely known physics-informed models or are made for specific goals. In this regard, this article proposes a compound learning-based MPC approach for DFUAVs to construct a suitable framework that exhibits efficient dynamics learning capability with adequate disturbance rejection characteristics. At the start, a nominal model from a largely unknown DFUAV model is achieved offline through sparse identification. Afterward, a reinforcement learning (RL) mechanism is deployed online to learn a policy to facilitate the initial guesses for the control input sequence. Thereafter, an MPC-driven optimization problem is developed, where the obtained nominal (learned) system is updated by the real system, yielding improved computational efficiency for the overall control framework. Under appropriate assumptions, stability and recursive feasibility are compactly ensured. Finally, a comparative study is conducted to illustrate the efficacy of the designed scheme.

Safe Reinforcement Learning for Transition Control of Ducted-Fan UAVs

Ducted-fan tail-sitter unmanned aerial vehicles (UAVs) provide versatility and unique benefits, attracting significant attention in various applications. This study focuses on developing a safe reinforcement learning method for back-transition control between level flight mode and hover mode for ducted-fan tail-sitter UAVs. Our method enables transition control with a minimal altitude change and transition time while adhering to the velocity constraint. We employ the Trust Region Policy Optimization, Proximal Policy Optimization with Lagrangian, and Constrained Policy Optimization (CPO) algorithms for controller training, showcasing the superiority of the CPO algorithm and the necessity of the velocity constraint. The transition trajectory achieved using the CPO algorithm closely resembles the optimal trajectory obtained via the well-known GPOPS-II software with the SNOPT solver. Meanwhile, the CPO algorithm also exhibits strong robustness under unknown perturbations of UAV model parameters and wind disturbance.

Numerical Prediction of Unsteady Aerodynamics of a Ducted Fan Unmanned Aerial Vehicle in Hovering

Recently, ducted fan unmanned aerial vehicles (UAVs) have attracted considerable attention due to their potential for application in both civil and military missions. Compared with free propellers, the presence of duct can in principle decrease the flow contraction after propeller, and gives the potential to fly efficiently with high security, compact structure, and low noise. In the present study, a ducted fan UAV is designed using the open source code OpenProp. The computational fluid dynamics (CFD) simulation model using sliding mesh technique is established and validated as a reliable tool for highly vortical flows by propeller thrust experiment. The effect of the duct, revolution speed, and distance between propellers on the aerodynamic characteristics of the ducted fan UAV is evaluated in detail. Results show that the unducted coaxial upper and lower propellers generate 3.8%, 4.3% more thrust than the unducted single propellers, respectively, and the unducted upper and lower propellers generate 55.9%, 34.9% more thrust than ducted propellers, respectively. The ducted fan UAV generates 5.7% more thrust and consumes 39.1% less power than the unducted coaxial propellers. The thrust of the ducted fan UAV increases first and then follows with a decreased tendency as the distance between propellers increases.

A Novel Adaptive Super-Twisting Sliding Mode Control Scheme with Time-Delay Estimation for a Single Ducted-Fan Unmanned Aerial Vehicle

This article proposes a novel adaptive super-twisting sliding mode control scheme with a time-delay estimation technique (ASTSMC-TDE) to control the yaw angle of a single ducted-fan unmanned aerial vehicle system. Such systems are highly nonlinear; hence, the proposed control scheme is a combination of several control schemes; super-twisting sliding mode, TDE technique to estimate the nonlinear factors of the system, and an adaptive sliding mode. The tracking error of the ASTSMC-TDE is guaranteed to be uniformly ultimately bounded using Lyapunov stability theory. Moreover, to enhance the versatility and the practical feasibility of the proposed control scheme, a comparison study between the proposed controller and a proportional-integral-derivative controller (PID) is conducted. The comparison is achieved through two different scenarios: a normal mode and an abnormal mode. Simulation and experimental tests are carried out to provide an in-depth investigation of the performance of the proposed ASTSMC-TDE control system.

Altitude Control Design and Performance Validation for Unmanned Aerial Vehicle with a Single Ducted-Fan

In this paper, the authors propose a novel control method for altitude control of aerial vehicle by extending the sliding mode law with fuzzy law and feedback control (F-SMFC). The key issue in the sliding mode control method is to suppress the chattering phenomenon. By providing a new control strategy, the solutions of the problems such as governing the chattering phenomenon and arbitrarily exploiting the numeric control by the fuzzy law were obtained. Also, it was shown that the F-SMFC method can cope with the unknown physical parameter of the system. The proposed control method was applied to the altitude control of the single ducted-fan unmanned aerial vehicle (UAV). Both simulation and experimental results were demonstrated to validate effectiveness and satisfactory performances of the proposed controller.

Aerodynamic performance assessment of a ducted fan UAV for VTOL applications

The aerodynamic performance of a recent developed ducted fan Unmanned Aerial Vehicle (UAV) was experimentally assessed by means of force, pressure and PIV measurements. Experiments were conducted on the UAV for both hover and forward flight configurations. Particular attention was given to the in-ground-effect which is important for the take-off and landing modes of the UAV during flight. Variations included rotational speed of the contra-rotating fan, incident angle, forward flight speed and the exit-to-ground distance were examined, allowing a comprehensive understanding of the overall aerodynamic characteristics of the ducted fan UAV. Wind tunnel measurement has successfully defined an initial operation region of the ducted fan UAV. The inlet velocity distortion at the inlet of the UAV during forward flight can significantly influence the inlet circumferential pressure distribution and therefore in principle affect the overall aerodynamic performance. The presence of the ground during take-off and landing can enhance the total lift generation with slightly sacrificing propulsive efficiency. In addition, when the UAV flies in proximity of the ground the back pressure at exit will be increased and thus alleviates the lift production by the duct lip. The outcomes can provide essential information in design and optimization of ducted fan type flight vehicles.

Trajectory tracking control of a VTOL unmanned aerial vehicle using offset-free tracking MPC

Designing a stable and robust flight control system for an Unmanned Aerial Vehicle (UAV) is an arduous task. This paper addresses the trajectory tracking control problem of a Ducted Fan UAV (DFUAV) using offset-free Model Predictive Control (MPC) technique in the presence of various uncertainties and external disturbances. The designed strategy aims to ensure adequate flight robustness and stability while overcoming the effects of time delays, parametric uncertainties, and disturbances. The six degrees of freedom DFUAV model is divided into three flight modes based on its airspeed, namely the hover, transition, and cruise mode. The Dryden wind turbulence is applied to the DFUAV in the linear and angular velocity component. Moreover, different uncertainties such as parametric, time delays in state and input, are introduced in translational and rotational components. From the previous work, the Linear Quadratic Tracker with Integrator (LQTI) is used for comparison to corroborate the performance of the designed controller. Simulations are computed to investigate the control performance for the aforementioned modes and different flight phases including the autonomous flight to validate the performance of the designed strategy. Finally, discussions are provided to demonstrate the effectiveness of the given methodology.

Neural-Networks Control for Hover to High-Speed-Level-Flight Transition of Ducted Fan UAV With Provable Stability

In this paper, we focus on the transition control of a ducted fan vertical take-off and landing (VTOL) unmanned aerial vehicle (UAV). To achieve a steady transition from hover to high-speed flight, a neural-networks-based controller is proposed to learn the system dynamics and compensate for the tracking error between the aircraft dynamics and the desired dynamic performance. In prior, we derive the nonlinear system model of the aircraft full-envelope dynamics. Then, we propose a novel neural-networks-based control scheme and apply it on the underactuated aircraft system. Key features of the proposed controller consist of projection operator, state predictor and dynamic-formed adaptive input. It is proved and guaranteed that the tracking errors of both state predictor and neural-networks weights are upper bounded during the whole neural-networks learning procedure. The very adaptive input is formed into a dynamic structure that helps achieve a reliable fast convergence performance of the proposed controller, especially in high-frequency disturbance conditions. Consequently, the closed-loop system of the aircraft is able to track a certain trajectory with desired dynamic performance. Satisfactory results are obtained from both simulations and practical flight test in accomplishing the designed flight course.

Control Performance Analysis on Variable Configuration of Ducted-Fan Flight Array

This paper proposes a novel aerial system named as a ducted-fan flight array system. The distinct feature of the proposed system is a reconfigurable flight system by assembly or disassembly regarding its operational objectives. This array system comprises multiple ducted-fan unmanned aerial vehicles (UAVs) which have a favorable configuration to equip a connecting mechanism around its duct. For the proposed system, this paper discusses dynamics to take account of the change of physical properties due to its reconfigurable feature. Moreover, the dynamics deal with control effectors which comprise multiple flaps and rotors for the array configuration. Based on the derived dynamic model, performance analysis is conducted to consider total external force and moment, control effect, and mechanical connectivity between the vehicles with respect to various candidates for the array configuration. The analysis shows that dominant parameters are the control power and mechanical connectivity for the proposed flight array system. In contrast, the influence of the external force and moment is relatively small by configuration changes. Through this research, the suitable configuration of the array can be confirmed to be a close-set shape with a balanced control combination.

On dynamic characteristics and stability analysis of the ducted fan unmanned aerial vehicles

This article researches the improvement of dynamics stability of the ducted fan unmanned aerial vehicles by optimizing its mechanical–structure parameters. The instability phenomenon of ducted fan unmanned aerial vehicles takes place frequently due to the complicated airflow in near-earth space, which easily leads to the stability problems, such as out of control, shaking, and loss accuracy of command tracking. The dynamics equations mirror its dynamics characteristics, which are primarily influenced by the mechanical–structure parameters of the whole system. Based on this, the optimization of mechanical–structure parameters has a significant to improve the dynamics stability of the whole system. Therefore, this article uses the concept of Lyapunov exponents to build the quantification relationship between system’s mechanical–structure parameters and its motion stability to enhance its stability from viewpoint of mechanical–structural parameter design. The takeoff, landing, and hovering stage are respectively studied and the conclusions suggest that the optimization of mechanical–structure parameters can be used to promote dynamics stability.

Design of a Control System for an Organic Flight Array Based on a Neural Network Controller

This paper presents a flight control system for an organic flight array (OFA) with a new configuration consisting of multimodularized ducted-fan unmanned aerial vehicles. The OFA has a distinguished advantage of assembling or separating with respect to its missions or operational conditions because of its reconfigurable structure. Therefore, designing a controller that can be flexibly applied in each situation is necessary. First, a dynamic modeling of the OFA based on a single ducted-fan vehicle is performed. Second, the inner loop for attitude control is designed through dynamic model inversion and a PD controller. However, an adaptive control component is needed to flexibly cope with the uncertainty because the operating environment of the OFA is varied, and uncertainty exists depending on the number of modules to be assembled and disturbances. In addition, the performance of the neural network adaptive controller is verified through a numerical simulation according to two scenarios.

Noise Prediction of Ducted Fan Unmanned Aerial Vehicles considering Strut Effect in Hover

In recent years, unmanned aerial vehicles (UAVs) have been developed and studied for various applications, including drone deliveries, broadcasting, scouting, crop dusting, and firefighting. To enable the wide use of UAVs, their exact aeroacoustic characteristics must be assessed. In this study, a noise prediction method for a ducted fan UAV with complicated geometry was developed. In general, calculation efficiency is increased by simulating a ducted fan UAV without the struts that fix the fuselage to the ducts. However, numerical predictions of noise and aerodynamics differ according to whether struts are present. In terms of aerodynamic performance, the total thrust with and without struts is similar owing to the tendency of the thrust of a blade to offset the drag of the struts. However, in aeroacoustic simulations, the strut effect should be considered in order to predict the UAV’s noise because noise from the blades can be changed by the strut effect. Modelling of the strut effect revealed that the dominant tonal noises were closely correlated with the blade passage frequency of the experimental results. Based on the successful detection of noise sources from a ducted fan UAV system, using the proposed noise contribution contour, methods for noise reduction can be suggested by comparing numerical results with measured noise profiles.

Modelling and attitude control of a miniature ducted fan UAV

Ducted fan UAV (Unmanned Aerial Vehicle) has broad application prospective. To study flight dynamics and flight control problems of ducted fan UAV, this paper developed a refined aerodynamic model for the ducted fan UAV by wind tunnel test. Based on that, the flight dynamic model of ducted fan UAV was built, which showed features as being nonlinear and unstable and of strong coupling and, therefore, inspired this paper to adopt a strong adaptive control approach based on decoupling to perform attitude control on the ducted fan vehicle. The approach combined model tracking control and reference model adaptive control together, which highly reduced attitude tracking error and improved stability margin of the closed-loop system, and was successfully applied in flight control simulation and flight tests of the vehicle.

Control System Design for a Ducted-Fan Unmanned Aerial Vehicle Using Linear Quadratic Tracker

Tracking control system based on linear quadratic (LQ) tracker is designed for a ducted-fan unmanned aerial vehicle (UAV) under full flight envelope including hover, transition, and cruise modes. To design the LQ tracker, a system matrix is augmented with a tracking error term. Then the control input can be calculated to solve a single Riccati equation, but the steady-state errors might still remain in this control system. In order to reduce the steady-state errors, a linear quadratic tracker with integrator (LQTI) is designed to add an integral term of tracking state in the state vector. Then the performance of the proposed controller is verified through waypoint navigation simulation under wind disturbance.

A Novel Ducted-Fan UAV Model Using Magnus Effect Steering Engine

This current article presents a ducted-fan unmanned aerial vehicle model based on the Magnus effect. The steering engine of this model consists of four cylinders that are symmetrically installed at the aft inside the duct. The interaction between the rotating cylinder surface and the duct jet flow creates aerodynamic lift (control input), which is proportional to angular velocity of the cylinder. This phenomenon is referred to as the Magnus effect in fluid mechanics. As a common problem in the ducted-fan unmanned aerial vehicles, the pitch-forward (roll-forward) stability is highly sensitive to the yaw motion. A self-adjusting function on the aerodynamic lift is thus needed for the steering engine controller to retain pitch-forward stability. For this purpose, this paper proposes a coordinated design method of steering engine controller and position-attitude controller based on integrated nonlinear flight dynamics and virtual force (torque) guidance. The feasibility of the proposed ducted-fan unmanned aerial vehicle model is shown by simulations.

New Transition Method of a Ducted-Fan Unmanned Aerial Vehicle

In this research, a winged version of the ISTAR (from “intelligence, surveillance, target acquisition, and reconnaissance”) unmanned aerial vehicle is modeled first, and then a new transition method is proposed, which enables the vehicle to fly sideways at low speed for drag reduction. A nonlinear trajectory-following logic is adopted to correct altitude loss and horizontal drift during the transition. By simulation, the proposed transition method shows better acceleration performance. The comparison of the induced drag shows that the vehicle should roll to resume fixed-wing lift as soon as its minimum level-flight speed is achieved to optimize its acceleration performance.

Structure Optimization of Ducted-Fan UAV Based on CFD

Unmanned Aerial Vehicle (UAV) has been developed quickly for decades and a new kind of VTOL (Vertical Take-Off and Landing) UAV which is called Ducted-Fan Uninhabited Aerial Vehicle attracts more and more attention. This paper presents a new structure of the ducted-fan UAV. In this vehicle, the actuator system consists of four rotary cylinders which are symmetrically installed at bottom of inside duct. The force used for attitude stabilization is generated by the interaction between the surface of cylinder and the downwash, which is known as Magnus effect. In this paper, the optimization of this ducted fan UAV is conducted based on Computational Fluid Dynamics (CFD). The response surface methodology (RSM) and Genetic Algorithm (GA) are adopted in the optimization.

Dynamic Analysis of a Ducted Fan UAV in Forward Flight

This paper deals with the dynamic modeling of a ducted fan vertical takeoff and landing (VTOL) unmanned aerial vehicle (UAV) and focuses on the dynamic characteristics analyzing in forward flight. A 6-DOF nonlinear model has been established in terms of the forces and moments and the model can be used in the structure and control system design.

CFD Simulation for a New Ducted-Fan UAV Configuration

Ducted-fan unmanned aerial vehicle (UAV) is very beneficial in many civil and military applications. It has a good operational flexibility similar to helicopter. Normally, the ducting of high speed spinning fan is done for several reasons; the duct produces lift, it provides higher static thrust when compared to a bare fan of the same diameter, substantial noise level from a spinning fan or rotor can be suppressed, and it increase the safety level for both of the system and the user. However, the main challenge is to understand the aerodynamic characteristic of this vehicle. In this paper, computational fluid dynamic (CFD) is used to study the airflow and aerodynamic characteristic on a new configuration of ducted-fan UAV.

Active Yaw Control of a Ducted Fan-Based MAV using Synthetic Jets

The feasibility of using active flow control to stabilize a micro ducted fan unmanned aerial vehicle in a yaw motion was investigated experimentally. Flow control was implemented using synthetic jet actuators to manipulate the flow around the vehicle's stator vanes. As a result, this mechanically simplified control approach can be used to generate a yaw moment on the vehicle instead of moving control surfaces and articulated rotor blades. The rotational control of the MAV (165.5mm in diameter and 177.8mm in height) was obtained by activating surface-mounted synthetic jets that were mounted on a set of four fixed stators downstream of the duct. The synthetic jets were located downstream of a deliberately formed local separation to enable controlled flow reattachment. The flow field around the stators and in the wake was studied using particle image velocimetry (PIV) where the geometrical angle of attack of the stators was either 0° or 6° and the propeller rotational speed was either 4,200RPM or 9,000RPM (g...