Aerial Vehicles

This book contains 35 chapters written by experts in developing techniques for making aerial vehicles more intelligent, more reliable, more flexible in use, and safer in operation.It will also serve as an inspiration for further improvement of the design and application of aeral vehicles. The advanced techniques and research described here may also be applicable to other high-tech areas such as robotics, avionics, vetronics, and space

Integration, Testing and Validation, of a Small Hybrid-Electric Remotely-Piloted Aircraft

Parallel hybrid-electric technology offers a wide variety of new mission capabilities including low-observable loiter operations and increased fuel efficiency for small remotely-piloted aircraft. This research focused on the integration, validation, and testing of a hybrid-electric propulsion system consisting of commercially available components to fabricate a small remotely-piloted aircraft capable of extended low-observable operation. Three novel aspects contributed to the success of the design: optimization of the propulsive components to the integrated system, torque control of the components for additive power, and a one-way bearing/ pulley mechanism (patent pending) mechanically linking the hybrid system components. To the knowledge of the author at the time of publication, this project represents the first functional parallel hybrid-electric propulsion system for a remotely-piloted aircraft. The integration phase entailed the selection, testing, and assembly of components chosen based on prior design simulations. The propulsion system was retrofitted onto a glider airframe with a 12 ft wingspan and a maximum takeoff weight of 35 lbs, also based on the initial design simulations. During the validation and testing phases, results from bench, ground, and flight testing were compared to the design simulations. The designed propulsion system was well matched to the power estimates of the design simulations. Bench and ground tests demonstrated that hybrid mode, electric only mode, combustion only mode, and regeneration mode are fully functional. Comparison of bench test results to an engine only variant of the airframe indicate the HE system is capable of flying the aircraft

An Omnidirectional Aerial Platform for Multi-Robot Manipulation

The objectives of this work were the modeling, control and prototyping of a new fully-actuated aerial platform. Commonly, the multirotor aerial platforms are under-actuated vehicles, since the total propellers thrust can not be directed in every direction without inferring a vehicle body rotation. The most common fully-actuated aerial platforms have tilted or tilting rotors that amplify the aerodynamic perturbations between the propellers, reducing the efficiency and the provided thrust. In order to overcome this limitation a novel platform, the ODQuad (OmniDirectional Quadrotor), has been proposed, which is composed by three main parts, the platform, the mobile and rotor frames, that are linked by means of two rotational joints, namely the roll and pitch joints. The ODQuad is able to orient the total thrust by moving only the propellers frame by means of the roll and pitch joints. Kinematic and dynamic models of the proposed multirotor have been derived using the Euler- Lagrange approach and a model-based controller has been designed. The latter is based on two control loops: an outer loop for vehicle position control and an inner one for vehicle orientation and roll-pitch joint control. The effectiveness of the controller has been tested by means of numerical simulations in the MATLAB c SimMechanics environment. In particular, tests in free motion and in object transportation tasks have been carried out. In the transportation task simulation, a momentum based observer is used to estimate the wrenches exchanged between the vehicle and the transported object. The ODQuad concept has been tested also in cooperative manipulation tasks. To this aim, a simulation model was considered, in which multiple ODQuads perform the manipulation of a bulky object with unknown inertial parameters which are identified in the first phase of the simulation. In order to reduce the mechanical stresses due to the manipulation and enhance the system robustness to the environment interactions, two admittance filters have been implemented: an external filter on the object motion and an internal one local for each multirotor. Finally, the prototyping process has been illustrated step by step. In particular, three CAD models have been designed. The ODQuad.01 has been used in the simulations and in a preliminary static analysis that investigated the torque values for a rough sizing of the roll-pitch joint actuators. Since in the ODQuad.01 the components specifications and the related manufacturing techniques have not been taken into account, a successive model, the ODQuad.02, has been designed. The ODQuad.02 design can be developed with aluminum or carbon fiber profiles and 3D printed parts, but each component must be custom manufactured. Finally, in order to shorten the prototype development time, the ODQuad.03 has been created, which includes some components of the off-the-shelf quadrotor Holybro X500 into a novel custom-built mechanical frame

Aeronautical engineering: A continuing bibliography with indexes (supplement 223)

This bibliography lists 423 reports, articles, and other documents introduced into the NASA scientific and technical information system in January, 1988

Aerodynamic Sensing for Autonomous Unmanned Aircraft Systems.

Autopilots currently rely on a single set of air data probe plus inertial measurements fed into linearized models to predict the aerodynamic forces and moments acting on a flight vehicle. While this approach is well suited to most aerospace applications, emerging flapping and fixed-wing unmanned aircraft systems (UAS) operated at post-stall conditions introduce aerodynamic forces that are complex and difficult to predict with such models and measurements. This research investigates the use of distributed pressure sensing for real-time aerodynamic force and moment characterization on flapping wing and small fixed wing UAS platforms. Flapping flight is first considered. A flapping wing test platform has been built with pressure based instrumentation embedded in rigid wings along with an integrated force-torque sensor. Through a series of vacuum chamber and wind tunnel experiments, time-resolved aerodynamic loads generated by a rigid flapping wing at a Reynolds number of approximately 4500 have been measured using both sets of instrumentation. At hover, key parameters such as phase and peak magnitudes measured by force-torque and pressure sensors agreed to within 10%, providing cross-validation and showing that the embedded pressure sensing concept is suitable for future flight control applications. Expanded aerodynamic data acquisition for a fixed wing UAS maneuvering in unsteady, post-stall flow conditions is also explored. This thesis introduces a reformulation of the steady fixed-wing flight equations for operations at high thrust, low airspeed conditions. A wind tunnel test system was developed around an existing flight vehicle with a 1.8m wingspan. Measurements of the pitch and yaw moments due to the tail surfaces were collected directly through embedded pressure measurements and indirectly through a custom air data probe measuring propeller backwash near the tail. Test data was acquired to determine the in-flight aerodynamic pitch and yaw moments due primarily to propeller backwash when the UAS operates past stall. Through comparisons with torque-transducer measurements, both methods are shown to provide moment estimates within one standard deviation of transducer measurements at hover. Model coefficients or slopes in data trends also compared favorably over all other tests.PhDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/102304/1/dyeo_1.pd

Lessons learned and unlearned, the theory and practice of employing airpower in small wars, the RAF, 1910 – 2010.

Since the end of The First World War, airpower has been used extensively by some states in unconventional operations. Surprisingly, very little has been written about this role of airpower in comparison to conventional operations, both by historians and theorists, and even more surprisingly by air forces themselves. Historians have tended to focus on large scale airpower centric events, such as the Battle of Britain, the strategic bombing campaigns of the Second World War, cold war dog fighting in Korea etc, while theorists have in the main focused on the strategic level, in particular the nuclear dimension. Historians for their part have focused on large scale airpower centric events due to the large quantities of primary source material available, and also undoubtedly due to the apetite for output related to these well known events in history. Unsurprisingly air forces have tended to focus their attention on the ability of airpower to provide an edge over their traditional opponents (i.e. other air forces). This was also a feature of early naval theorists.3 This focus by air forces can be explained due to the need for air foces of all sizes to justify the heavy investment required by states to maintain a modern, capable air component. These large budgets can be justified by planning for large scale conventional conflict against a peer, not so much for countering insurgents in second and third world countries. In contrast, this work will shine a light on the topic of airpower in small wars, in particular focusing on the relationship between the theory and the practice of deploying airpower in small wars and thus look to fill the gap in historiography, as highlighted above. It will achieve this by focusing on several research areas. Firstly, it will examine the development of air power theory and doctrine during this period, providing a high level overview of the entirety of airpower theory, and then focusing specifically on doctrine and theory relevant to the utilisation of airpower in small wars . Secondly, it will examine the practical application of air power in small wars during this period, and throughout it will use organizational learning as an analytical framework to determine whether or not during this period the RAF can be considered a learning organisation. By undertanding this a better determination can be made as to the effectiveness of the RAF in a small wars environment in the past, and its ability to be succesful in current and future operations. This determination will be based on an understanding of whether or not theory and doctrine impacted practical application, and whether lessons learned through practical application impacted subsequent theory and doctrine. The outcome of this research will provide information of relevance to both the professional and academic fields within this area and will undoubtedly have policy relevance to air forces and governments around the world. Furthermore, the focus on organizational learning will have broader appeal as the outcome will have applicability in several fields and allow organizations of all types to become more efficient and effective at learning and adapting. The following section outlines the structure of this work and provides a chapter outline

Aeronautical Engineering: A continuing bibliography, supplement 124

This bibliography, lists 450 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1980

Design and control of a spherical VTOL vehicle

This research presents the design of a spherically shaped Unmanned Aircraft System (UAS) called the All-Terrain Land and Air Sphere (ATLAS). ATLAS is designed to include competing design requirements necessary for operating in an indoor cluttered environment for emergency response and inspection applications, particularly around people, including the ability to hover, execute coordinated maneuvers with translational flight, land on uneven terrain, and return to flight. The spherical frame can interact with the environment and land without the need for coordinated vertical landing maneuverability such as other rotary winged devices, including multi-rotors or helicopters. One of the features that sets ATLAS apart from other similarly sized drones is the capability to roll on the ground to maneuver to a new location and avoid obstacles before executing an upright maneuver for recovery to flight. These features make ATLAS suitable as a search and rescue platform in supporting both aerial and ground operations. The diameter and payload capability of the ATLAS is scalable depending on the mission requirements. While multiple sizes have been developed, the primary system presented herein has a diameter of 40 cm (16 inch) and weighs about 900 grams (2 lbs).The first part of this study investigates the characteristic of a passive flight control mechanism made up of eight movable hinged arc vanes positioned radially around the propeller tips. Such passive devices are not presented in any open propeller platform. Each vane is hinged and mechanically restricted to rotate between 0 to 90 degrees. A series of bench testing results show that these passive control surfaces generate an upward or downward force depending on the proximity and strength of the airflow interaction coming toward the propeller during flight conditions. These passive vanes can also help stabilize the vehicle in contrast to an open propeller setup.The second part of this study evaluates control schemes for a single propeller with multiple control surfaces. Unlike ducted fans and multi-rotor platforms, the control vanes are strongly coupled to provide stability and control along all principal axes while counteracting the induced torque effects generated by a single pitch propeller. ATLAS has demonstrated stable flight tests by using a Proportional-Integrator-Derivative (PID) control based on the proposed control scheme and can successfully perform flight recovery from in-flight disturbances through the implementation of a non-linear model using the Newton-Euler formulation. Ground maneuvers are made possible by reversing the propeller direction to provide sufficient reverse thrust without the need for a variable pitch propeller