INDI Control for the ObliqueWing-Quad Plane Drone

A type of UAV sharing the advantages of rotorcraft and fixed wing vehicles is the hybrid vehicle. Hybrid UAVs can take-off and land vertically and fly fast and efficient in forward flight due to the presence of a wing generating lift. However, combining the fixed wing and rotorcraft concept ends up in a multi-rotor with large dimensions when landed, and catching a lot of gust when hovering. Therefore, the oblique wing-quad plane drone has been developed which can rotate its quad arm and wing such that the wing can be aligned with the fuselage in hover. The wing can be rotated to fixed wing position during fast forward flight, stowing away one quad-arm. An INDI inner and outer loop controller has been implemented for this platform. Successful flight tests proved the feasibility of this controller and drone concept which is patent pending NL 2031701, Aeronautical Vehicle and Method of Transitioning between Flight Modes for an Aeronautical Vehicle, April 26th 2022,Control & Simulatio

Design and testing of a remotely controlled surfkite for the Laddermill

This paper presents the design and testing of a remotely controlled surfkite for the Laddermill. The Laddermill is a novel concept to generate electricity from high altitude winds. It generates electricity by pulling a rope from a generator, with lift generated by kites. Part of the rope that is connected to the kites is wound around the generator. The kites pull the rope from the generator, thus driving it. Subsequently the kites fly down in a configuration that generates significantly less lift than during the ascent. This way the tether is retrieved and the process is repeated. The Laddermill concept allows very large single unit powers. For an early demonstration of the Laddermill principle, a commercially availably Peter Lynn surfkite is used. This surfkite is radio controlled, by means of drag creating actuators on the wing tips. This paper presents the actuator design and results of testing of the surfkite. Preliminary results of generation of Laddermill energy are also presented.Aerospace Engineerin

A Survey of Optimal Control Allocation for Aerial Vehicle Control

In vehicle control, control allocation is often used to abstract control variables from actuators, simplifying controller design and enhancing performance. Surveying available literature reveals that explicit solutions are restricted to strong assumptions on the actuators, or otherwise fail to exploit the capabilities of the actuator constellation. A remedy is to formulate hierarchical minimization problems that take into account the limits of the actuators at the expense of a longer computing time. In this paper, we compared the most common norms of the objective functions for linear or linearized plants, and show available numeric solver types. Such a comparison has not been found in the literature before and indicates that some combinations of linear and quadratic norms are not sufficiently researched. While the bulk of the review is restricted to control-affine plant models, some extensions to dynamic and nonlinear allocation problems are shown. For aerial vehicles, a trend toward linearized incremental control schemes is visible, which forms a compromise between real-time capabilities and the ability to resolve some nonlinearities common in these vehicles.Control & Simulatio

Incremental Nonlinear Dynamic Inversion controller for a Variable Skew Quad Plane

This paper presents the design of an Incremental Nonlinear Dynamic Inversion (INDI) controller for the novel, patent pending (NL 2031701) platform Variable Skew Quad Plane (VSQP). Part of the identified challenges is the development of a model for the actuator effectiveness and lift especially as a function of skew, the newly added degree of freedom. The models and assumptions are verified through static and dynamic wind tunnel tests at the Open Jet Facility (OJF) of TU Delft. Transition tests have been successfully performed thanks to an automatic skew controller derived from the proposed models and aimed to maximize control authority.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Control & Simulatio

Developing a modular tool to simulate regeneration power potential using orographic wind-hovering uavs

Applications of Unmanned Aerial Vehicles (UAVs) are often limited by flight endurance. To address the limitation of endurance, we propose a regenerative soaring method in this paper. The atmospheric energy from updraft generated by obstacles such as hills and ships can be harvested by UAVs using a regenerative electric drivetrain. With fixed-wing aircraft, the vehicle can hover with specific wind condition, and the battery can be recharged in the air while wind hovering. In order to research the feasibility of this regenerative soaring method, we present a model to estimate hovering locations and the amount of extractable power using the proposed method. The resulting modular regeneration simulation tool can efficiently determine the possible hovering locations and provide an estimate of the power regeneration potential for each hovering location, given the UAVs aerodynamic characteristics and wind-field conditions.Control & Simulatio

Design and joint control of a conjoined biplane and quadrotor

Unmanned Aerial Vehicles (UAVs) have the potential to perform many different missions, some of which may require a large aircraft for endurance and a small aircraft for manoeuvrability in a building. This paper proposes a novel combination of a quadrotor and a hybrid biplane capable of joint hover, joint forward flight, and mid-air disassembly followed by separate flight. We investigate cooperative control strategies during joint flight that do not require any communication between the quadcopter and the biplane. This means that the two aircraft have their own independent control strategy based on their own sensors. Secondly, to avoid communication the biplane leads the flight and the goal for the quadrotor is to help in producing thrust and increasing stability. Three control strategies for the quadrotor are compared: a proportional angular rate damper, a proportional angular acceleration damper, and constant thrust without attitude control. Simulation and practical tests show that for intentional attitude changes of the biplane, the quadrotor rate- and angular acceleration damper strategies lead to a small performance degradation. However, the angular rate damper strategy for disturbance rejection has the lowest roll angle error and requires the smallest input command. The in-flight release is successfully tested in joint hover up to a forward pitch angle of -18 [deg].Control & Simulatio

Flight code convergence: fixedwing, rotorcraft, hybrid

Rotorcraft, fixed wing and hybrid Unmanned Air Vehicles (UAV) each have applications in which they excel. Traditionally, dedicated autopilot control code is written to accommodate flight of each UAV type. This causes fragmentation of control code and may lead to performance differences or errors. In this paper, we propose to use the same INDI controller for rotorcraft, fixed wing and hybrid UAVs, with only parametric differences in control effective matrix definitions and roll, pitch and airspeed limits. The controller is based on earlier work, but relevant derivations are included in this paper. Successful test flights, performed with a Bebop2 quadrotor, a Disco fixed wing, and a Nederdrone tailsitter hybrid demonstrate the feasibility of this approach.Control & Simulatio

Modeling DelftaCopter from Flight Test Data

The DelftaCopter, a tilt-body tailsitter UAV, endures large gyroscopic moments due to the single helicopter rotor providing its thrust. In previous research by de Wagter et al.[1] the DelftaCopter’s attitude dynamics were modeled using a rigid rotor, as is customary for small helicopter modeling. A controller based on this model was unable to compensate coupling between pitch and roll rate caused by gyroscopic moments. In this paper, two models are compared for reproducing the attitude dynamics of the Delfta- Copter in hover. The Cylinder Dynamics (CD) model, used in the previous research, assumes a rigid rotor. The Tip-Path Plane (TPP) model incorporates flapping motion of the blades and was developed by Mettler[2]. The two models are compared by fitting each model’s parameters on flight data using chirps, sine waves with increasing frequency, as system identification maneuvers. The TPP model is shown to be much more accurate in reproducing the high-frequency attitude dynamics. An LQR controller directly based on the TPP model is shown to yield adequate tracking performance. This validates the applicability of this model to the DelftaCopter. For forward flight, an extension to the TPP hover model is proposed incorporating the aerodynamics of the wings and elevons. It is shown that with the extension, chirps in forward flight can be simulated with reasonable accuracy. This paves the way for a model-based controller in this flight state.Control & Simulatio

Force generation and wing deformation characteristics of the ’DelFly II’ MAV in hovering flight conditions

The study investigates the relation between wing deformation and unsteady force generation of the flapping-wing MAV DelFly II in hovering flight configuration. The three-dimensional wing deformation was measured with a stereo-vision system, while fluid forces were acquired simultaneously with a force sensor. Comparison of the results for different flapping frequencies reveals different wing kinematics and deformation characteristics. The high flapping frequency case produces higher forces throughout the complete flapping cycle. Moreover, a phase difference occurs in the variation of the forces, such that the low flapping frequency case precedes the high frequency case. A similar phase lag is observed in the temporal evolution of the wing deformation characteristics, suggesting that there is a direct link between the two phenomena.AerodynamicsControl & Simulatio

Dual-axis tilting rotor quad-plane design, simulation, flight and performance comparison with a conventional quad-plane design

In the last few decades, the UAV research has been focusing on hybrid vehicles with Vertical Takeoff and Landing (VTOL) capabilities. Opposed to copters, hybrid vehicles are highly influenced by wind disturbances. This paper presents a novel quad-plane design that uses four dual-axis tilting rotors to enhance the wind rejection capability of a conventional quad-plane vehicle. After the non-linear mathematical model derivation and the actuator identification, the performance of the vehicle is addressed and compared to a conventional quad-plane in simulation, showing a factor 3.4 improvement in linear acceleration reaction time and a reduction of the gust induced displacement of 80%. Free-flight wind tunnel experiments confirmed the simulation outcome and extended the vehicle wind rejection capabilities behavior also to the lateral gust scenario. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Control & Simulatio