Ducted fan VTOL UAVs are currently being designed for use by the Army for surveillance and reconnaissance in the battlefield. The vehicle tested in this research is part of the Honeywell MAV program. Able to be carried in a backpack by a single soldier, it has a duct diameter of 11.5-in. and weighs approximately 20-lbs at takeoff. It is designed for flight up to 50-knots with fan speeds varying between 5000 and 8500 RPM. Reynolds numbers, based on the duct diameter, were on the order of Re = 0.96 x 106 to 4.6 x 106. Various control effectors were mounted to the vehicle and tested for maximum control authority to reduce the nose-up pitch moment created during forward flight or with crosswinds present. Static and wind tunnel tests were conducted to measure each control effector's performance. Box vanes, mounted downstream of the duct, utilized four assemblies, each with three vanes and one flap. This configuration showed adequate results in generating a nose-down pitch moment. Duct deflectors, mounted on the windward strut upstream of the duct, reduced the windward lift produced by both the fan and duct, resulting in a nose-down pitch moment. Opposed vanes, utilizing two vanes and flaps for each of the four assemblies, were designed with the same surface area as the box vanes. With each pair capable of independent vane movement, the opposed vanes were tested with the vanes rotating in tandem for a basic elevator deflection and with the leading edges touching, disrupting the flow at the duct exit. Opposed vanes combined the capabilities of the box vanes and duct deflector. Results show that the opposed vanes were the most practical control effector, offering the most control authority for maximum nose-down pitch moment (up to 80% better) with minimal loss in thrust. / Master of Science

In order to improve the flight performance of the Martin Jetpack research was undertaken to investigate the aerodynamic issues that were limiting the P-11A Jetpack's flight envelope. Through research of existing ducted-fan aircraft, a flight model describing the unique aerodynamics of the Martin Jetpack was developed using Matlab®/Simulink® software. The dynamic flight model, which can be ran in real time, includes the reactions from: ducted-fans, aircraft body aerodynamics, control surfaces, gyration and landing gear interactions. Abstract Numerous experiments were designed to quantify and validate assumptions used in the development of the model equations. The experiments took advantage of the small size of the Jetpack by designing and building test apparatuses that measured reactions directly on the actual aircraft. This avoided scaling issues that are traditionally encountered when employing wind tunnels for aerodynamic measurements. Abstract Implementing the experimental results into the model led to the modifications of the existing Jetpack airframe to produce the P-11C Jetpack prototype, which significantly improved the performance of the aircraft. The collected flight data was used to validate the model and good agreement was achieved. Abstract Based on this research a new Jetpack prototype (P-12) was developed that combined the flight performance of the P-11C Jetpack with the ability to carry a man or manned sized payload. The model was used to design the layout and to size the control vanes for the P-12 Jetpack. Further research was performed to design larger rotor and stator blades required for the P-12 Jetpack prototype. Abstract The developed model allows the user to efficiently evaluate various control methodologies and changes to key aerodynamic features of the aircraft to aid in the design and flying of the Martin Jetpack. Abstract The outcome of this research is a better understanding of the ducted-fan technology, and via the development of the Jetpack flight model, correctly applying this understanding to improve the Jetpack's flight performance.

<p>The ducted fan UAV is an unmanned aerial vehicle consisting mainly of a propeller enclosed in a open ended tube. The UAV has the same basic functions as an ordinary helicopter UAV but has several advantages to the same.</p><p>This thesis aims to estimate the performance of the concept of the ducted fan UAV. The company where this thesis has been written, DST Control AB, is currently investigating the economical possibilities to continue the development of this kind of UAV. This thesis shall provide DST Control AB with a theoretical as well as experimental ground for the investigation by estimation the lift capacity, position accuracy and wind tolerance.</p><p>A ducted fan UAV prototype and a mathematical model for that UAV have been developed by DST Control AB and a student project at Linköping University. The model is constructed through pure physical modeling. Several noise sources have been added to better fit the reality. Several experiments have been conducted to validate the model with satisfying results. Experiments to determine the lift capacity of the craft have also been conducted. These experiments showed a slightly smaller lift capacity than the theoretically calculated lift capacity. The wind tolerance has not been tested in experiments because of the lack of available wind tunnels but simulations have given an estimation of this tolerance.</p><p>To estimate the position accuracy, two different control systems have been implemented. The simplest control system is a system consisting of several PID controllers. The system is divided into two separate subsystems connected in cascade. The inner subsystem takes the pitch, roll and yaw angle as inputs and gives the rudder angles as outputs. The outer subsystem takes the inertial position as input and gives roll, pitch and yaw as outputs. Together, the two subsystems can be used to control the entire craft. The inner subsystem has also been replaced with a small LQ Compensator. An LQ Compensator for the entire system is also implemented giving about as good performance as the PID controller and better performance than the PID/LQ combination.</p>

The ducted fan UAV is an unmanned aerial vehicle consisting mainly of a propeller enclosed in a open ended tube. The UAV has the same basic functions as an ordinary helicopter UAV but has several advantages to the same. This thesis aims to estimate the performance of the concept of the ducted fan UAV. The company where this thesis has been written, DST Control AB, is currently investigating the economical possibilities to continue the development of this kind of UAV. This thesis shall provide DST Control AB with a theoretical as well as experimental ground for the investigation by estimation the lift capacity, position accuracy and wind tolerance. A ducted fan UAV prototype and a mathematical model for that UAV have been developed by DST Control AB and a student project at Linköping University. The model is constructed through pure physical modeling. Several noise sources have been added to better fit the reality. Several experiments have been conducted to validate the model with satisfying results. Experiments to determine the lift capacity of the craft have also been conducted. These experiments showed a slightly smaller lift capacity than the theoretically calculated lift capacity. The wind tolerance has not been tested in experiments because of the lack of available wind tunnels but simulations have given an estimation of this tolerance. To estimate the position accuracy, two different control systems have been implemented. The simplest control system is a system consisting of several PID controllers. The system is divided into two separate subsystems connected in cascade. The inner subsystem takes the pitch, roll and yaw angle as inputs and gives the rudder angles as outputs. The outer subsystem takes the inertial position as input and gives roll, pitch and yaw as outputs. Together, the two subsystems can be used to control the entire craft. The inner subsystem has also been replaced with a small LQ Compensator. An LQ Compensator for the entire system is also implemented giving about as good performance as the PID controller and better performance than the PID/LQ combination.

The motivation for this research is the need to improve performance of the autonomous flight of a tailsitter UAV. Tailsitter aircraft combine the hovering and vertical take-off and landing capability of a rotorcraft with the long endurance flight capability of a fixed-wing aircraft. The particular aircraft used in this research is the V-Bat, a tailsitter UAV with a conventional wing and the propeller and control surfaces located within a ducted-fan tail assembly. This research focuses on identifying the models and parameters of the V-Bat in hover and level flight as a basis for the design of the control systems for hover, level, and transition modes of flight.Models and parameters were identified from experimental data. Wind-tunnel tests, bench tests, and flight tests were performed in a variety of flight conditions. Wind tunnel tests yielded force and moment coefficients over the full flight envelope of the V-Bat. Models and parameters for longitudinal, lateral, and hover flight are presented. Bench tests were conducted to enhance understanding about the ducted-fan propulsion system and the effectiveness of the control surfaces. The thrust characteristics of the ducted fan were measured. Control derivatives were derived from force and moment measurements. Flight tests were completed to obtain dynamic models of the V-Bat in hover flight. Using frequency-domain system identification methods, frequency-response and transfer function models of roll, pitch, and yaw responses to aileron, elevator, and rudder control input were derived.The results obtained from these experimental tests were used to identify models and parameters of the V-Bat aircraft, giving insight into its behavior and enhancing the control analysis and simulation capabilities for this aircraft, thus providing the increased levels of understanding needed for autonomous flight.

Unmanned aerial vehicles (UAVs) are increasingly being used for both military and commercial applications to replace more costly and dangerous manned operations. Vehicles with vertical take-off and landing (VTOL) and hovering capabilities are of interest for functions such as surveillance and inspection where the ability to hold the position of the vehicle is desired. Ducted fan vehicles are of particular interest because of their high efficiency per unit diameter when compared to the more commonly seen multirotor vehicles. This makes ducted fan UAVs very well suited for size-constrained missions such as indoor inspection or urban reconnaissance. However, the advantages of ducted fans come at the cost of complex nonlinear dynamics which present challenging modeling and control problems. This thesis provides a detailed discussion of the instrumentation, modeling, and control of a ducted fan UAV. The dynamic model of the UAV is computed from a simplified parametric model. Unknown parameters of the model are found from system identification based on flight data. Synthesis of a linear state feedback controller based on this model is discussed, and it is demonstrated in hardware that this controller can effectively stabilize the vehicle. / Master of Science / Unmanned aerial vehicles (UAVs) are increasingly being used for both military and commercial applications to replace more costly and dangerous manned operations. Vehicles with vertical take-off and landing (VTOL) and hovering capabilities are of interest for functions such as surveillance and inspection where the ability to hold the position of the vehicle is desired. Ducted fan vehicles are of particular interest because of their high efficiency per unit diameter when compared to the more commonly seen multirotor vehicles. This makes ducted fan UAVs very well suited for size-constrained missions such as indoor inspection or urban reconnaissance. However, the advantages of ducted fans come at the cost of complex dynamics which present challenging modeling and control problems. This thesis provides a detailed discussion of the instrumentation, modeling, and control of a ducted fan UAV. The dynamic model of the UAV is computed from a simplified parametric model. Unknown parameters of the model are found from system identification based on flight data. Using this parametric model, development of a linear controller that uses feedback from the vehicle’s state is discussed, and it is demonstrated in hardware that this controller can effectively stabilize the vehicle.

This thesis extends the use of neural-network-based model reference adaptive control to systems that occur as cascades. In general, these systems are not feedback linearizable. The approach taken is that of approximate feedback linearization of upper subsystems whilst treating the lower-subsystem states as virtual actuators. Similarly, lower-subsystems are also feedback linearized. Typically, approximate inverses are used for linearization purposes. Model error arising from the use of an approximate inverse is minimized using a neural-network as an adaptive element. Incorrect adaptation due to (virtual) actuator saturation and dynamics is avoided using the Pseudocontrol Hedging method. Using linear approximate inverses and linear reference models generally result in large desired pseudocontrol for large external commands. Even if the provided external command is feasible (null-controllable), there is no guarantee that the reference model trajectory is feasible. In order to mitigate this, nonlinear reference models based on nested-saturation methods are used to constrain the evolution of the reference model and thus the plant states. The method presented in this thesis lends itself to the inner-outer loop control of air vehicles, where the inner-loop controls attitude dynamics and the outer-loop controls the translational dynamics of the vehicle. The outer-loop treats the closed loop attitude dynamics as an actuator. Adaptation to uncertainty in the attitude, as well as the translational dynamics, is introduced, thus minimizing the effects of model error in all six degrees of freedom and leading to more accurate position tracking. A pole-placement approach is used to choose compensator gains for the tracking error dynamics. This alleviates timescale separation requirements, allowing the outer loop bandwidth to be closer to that of the inner loop, thus increasing position tracking performance. A poor model of the attitude dynamics and a basic kinematics model is shown to be sufficient for accurate position tracking. In particular, the inner-outer loop method was used to control an unmanned helicopter and has subsequently been applied to a ducted-fan, a fixed-wing aircraft that transitions in and out of hover, and a full-scale rotorcraft. Experimental flight test results are also provided for a subset of these vehicles.

The technology of UAV (Unmanned Aerial Vehicle) has developed since its conception many years ago. UAVs have several features such as, computerised and autonomous control without the need for an on-board pilot. Therefore, there is no risk of loss of life and they are easier to maintain than manned aircraft. In addition, UAVs have an extended range/endurance capability, sometimes for several days. This makes UAVs attractive for missions that are typically

The Diploma thesis is concerned with aerodynamic designi of the ducted fan. The aim of this thesis is to compile the metod of the calculation for the effect of ducted fan. The thesis includes the statistical analysis of compare Rotorcraft, which is used to support the proposal of the basic design parameters. The next part of the thesis contains practical utilization, view of the possible pay load, view of the suitable engines and conrol units. The main part is concerned whit aerodynamic calculation of the stream and fan parameters. In the last part of the thesis, basic parameters of flight performances are calculated.

The military's desire for ducted fan vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs) stems from the vehicles' relatively small size, safety in tight quarters, increased payload capacity for their size, and their ability to hover for surveillance missions. However, undesirable aerodynamic characteristics are associated with these vehicles in crosswinds, namely momentum drag and asymmetric duct lift. Because the duct itself, and not the fan, is the root cause of these unfavorable aerodynamic attributes, various lip shapes were tested to determine the effects of leading edge radius of curvature and duct wall thickness. It was found that a lip with a small leading edge radius performed best in forward flight and crosswind conditions, while the performance of a lip with a large leading edge radius was enhanced in static conditions. Through tuft flow visualization and static pressure measurements it was determined that the reason for the difference in performance between the two lips was due to flow separation on the interior of the duct lip surface. Control vanes positioned aft of the duct were tested as the primary attitude control for the vehicle. An empirical control vane model was created based on the static data for the control vanes, and it was applied to wind tunnel test results to determine the required control vane angle for trim. Wind tunnel testing showed the control vanes were capable of trimming out the adverse pitching moment generated by the duct, but at some flight speeds large vane deflections were necessary. Additional control devices placed at the lip of the duct and stabilizer vanes positioned aft of the duct were tested to reduce the amount of control vane deflection required for trim. It was found that the duct deflector control effector had the largest impact on the adverse pitching moment, while the stabilizer vanes were only effective at low crosswind velocities. / Master of Science