Tools for the Conceptual Design and Engineering Analysis of Micro Air Vehicles

Micro Air Vehicles (MAV) are a subset of Unmanned Aircraft (UAS) that are up to two orders of magnitude smaller than manned systems. Near-Earth environments, such as forests, caves, tunnels and urban structures make reconnaissance, surveillance and search-and-rescue missions difficult and dangerous to accomplish. Therefore, MAVs are considered ideal for these types of missions. However, the data using full size aircraft is inadequate to characterize miniature aircraft parameters due to the lower Reynolds numbers and low aspect ratio (LAR) wings and impact of wing-propeller interactions. The main objectives of this research were to: collect and synthesize the available data/tools; create a statistically integrated database/tool set of MAV designs for conceptual design trades; validate the tool set using published experimental data; synthesize and model a prototype design using conceptual and empirical analysis; highlight MAV-specific design criteria and identify gaps in existing data for later research. The following design tools have constituted the starting point for creating a demonstration tool-set for MAV design: Digital DATCOM (aerodynamics), Athena Vortex Lattice (AVL) (stability and control), QPROP (propeller, motor, and energy requirement), MATLAB (various applications), Microsoft Excel (power/battery modeling) and Phoenix Integration Model Center (MC) as the executive control program (integration, sizing and trade studies). Validation cases were completed for the current level of the single-prop, fixed-wing design tool. A coaxial MAV prototype was evaluated and some parametric studies were conducted for QPROP performance

In-Mold Assembly of Multi-Functional Structures

Combining the recent advances in injection moldable polymer composites with the multi-material molding techniques enable fabrication of multi-functional structures to serve multiple functions (e.g., carry load, support motion, dissipate heat, store energy). Current in-mold assembly methods, however, cannot be simply scaled to create structures with miniature features, as the process conditions and the assembly failure modes change with the feature size. This dissertation identifies and addresses the issues associated with the in-mold assembly of multi-functional structures with miniature components. First, the functional capability of embedding actuators is developed. As a part of this effort, computational modeling methods are developed to assess the functionality of the structure with respect to the material properties, process parameters and the heat source. Using these models, the effective material thermal conductivity required to dissipate the heat generated by the embedded small scale actuator is identified. Also, the influence of the fiber orientation on the heat dissipation performance is characterized. Finally, models for integrated product and process design are presented to ensure the miniature actuator survivability during embedding process. The second functional capability developed as a part of this dissertation is the in-mold assembly of multi-material structures capable of motion and load transfer, such as mechanisms with compliant hinges. The necessary hinge and link design features are identified. The shapes and orientations of these features are analyzed with respect to their functionality, mutual dependencies, and the process cost. The parametric model of the interface design is developed. This model is used to minimize both the final assembly weight and the mold complexity as the process cost measure. Also, to minimize the manufacturing waste and the risk of assembly failure due to unbalanced mold filling, the design optimization of runner systems used in multi-cavity molds for in-mold assembly is developed. The complete optimization model is characterized and formulated. The best method to solve the runner optimization problem is identified. To demonstrate the applicability of the tools developed in this dissertation towards the miniaturization of robotic devices, a case study of a novel miniature air vehicle drive mechanism is presented

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

Aerodynamic Modeling of a Flapping Membrane Wing Using Motion Tracking Experiments

An analytical model of flapping membrane wing aerodynamics using experimental kinematic data is presented. An alternative to computational fluid dynamics, this experimental method tracks small reflective markers placed on two ornithopter membrane wings. Time varying three dimensional data of the wing kinematics and the corresponding aerodynamic loads were recorded for various flapping frequencies. The wing shape data was used to form an analytical aerodynamic model that uses blade element theory and quasi-steady aerodynamics to account for the local twist, stroke angle, membrane shape, wing velocity and acceleration. Results from the aerodynamic model show adequate correlation between the magnitude of lift and thrust produced but some phase errors exist between the measured and calculated force curves. This analytical model can be improved by comparison with a RANS CFD solver which provides insight into the fluid behavior. Implications on the membrane wing design are also presented

Selected Papers from the ICEUBI2019 - International Congress on Engineering - Engineering for Evolution

Energies SI Book "Selected Papers from the ICEUBI2019 – International Congress on Engineering – Engineering for Evolution", groups six papers into fundamental engineering areas: Aeronautics and Astronautics, and Electrotechnical and Mechanical Engineering. ICEUBI—International Congress on Engineering is organized every two years by the Engineering Faculty of Beira Interior University, Portugal, promoting engineering in society through contact among researchers and practitioners from different fields of engineering, and thus encouraging the dissemination of engineering research, innovation, and development. All selected papers are interrelated with energy topics (fundamentals, sources, exploration, conversion, and policies), and provide relevant data for academics, research-focused practitioners, and policy makers

Bio-Inspired Design of Vehicles that Operate in Complex Environments

This dissertation focuses on defining underlying mechanisms to enable the bio-inspired design of aerodynamic and/or hydrodynamic vehicles that operate within complex environments. This dissertation introduces four overarching research gaps found in current bio-inspired design research and four corresponding approach questions that guide the framework of the presented research. This research addresses the issues of a lack in determining “better” inspirational options for designers to use, a lack of automated methods within the field of bio-inspired design, a lack in a mechanical ranking system that is based on biology, and a lack of focus on capability an mobility linking the bio and mechanical world. This dissertation addresses these gaps through approach questions, used to design an Animal Specification Mobility Analysis (ASMA) methodology. This design methodology guides a designer to a potential bio-inspiration using simulations based on measurable specifications. These specifications help determine a score that represents the functionality of an animal within an environment. These scores supplement rank-able mobility characteristics that mathematically define what an animal may be capable of in terms of movement. The presented methodology is validated through three types of bio-inspired scenarios, each representing the current types of bio-inspired design processes

Prototype Development and Dynamic Characterization of Deployable CubeSat Booms

The current barrier to CubeSat proliferation is their lack of utility depth. These small satellites are exceptionally well suited for specific space missions such as space weather observation and other scientific data gathering exploits; however, they are not suited for every mission. The 10cm-cube form factor that gives the CubeSat its unique advantage is also its greatest hindrance. A potential bridge over this gap is the successful integration of deployable booms onto the CubeSat structure. With this research, the Air Force Institute of Technology (AFIT) explored the parameters of deployable tapespring booms using the triangular retractable and collapsible (TRAC) cross- sectional geometry developed by Air Force Research Labs (AFRL) and used on NASA’s CubeSat, Nanosail-D. These booms were augmented with reflective membranes and specifically designed to deploy on orbit for the purpose of ground observation; observations that could later be used to determine the deployed dynamics of the booms from optical data gained passively by solar illumination. Initially, the boom behavior at multiple frequency excitations was characterized so as to develop an accurate finite element model where further predictions could be determined without the costly attempt to simulate the often irreproducible environment of space. Nine total modal frequencies were detected and modeled below 25 Hz, which was to be expected as the gossamer-like structure of the beams is particularly susceptible to low-frequency excitations. In addition to stationary testing, deployment concept testing was also conducted to determine the viability of a novel boom and membrane deployment scheme developed in house. In concurrence with the finite element model, this data provides the foundation for the future development of deployable appendages onto the CubeSat platform here at AFIT

Nonlinear Fluid-Structure Interactions in Flapping Wing Systems

This work relates to fluid-structure interactions in the context of flapping wing systems. System models of flapping flight are explored by using a coupling scheme to provide communication between a fluid model and a structural model describing a flexible wing. The constructed computational models serve as a tool for investigating complex fluid-structure interactions and characterizing them. Primary goals of this work are construction of models to understand nonlinear phenomena associated with the flexible flapping wing systems, and explore means and methods to enhance their performance characteristics. Several system analysis tools are employed to characterize the coupled fluid-structure system dynamics, including proper orthogonal decomposition, dimension calculations, time histories, and frequency spectra. Results obtained from two-dimensional simulations conducted for a combination of a two-link structural system and a fluid system are presented and discussed. Comparisons are made between the use of direct numerical simulation and the unsteady vortex lattice method as the fluid model in this coupled dynamical system. To enable three-dimensional studies, a novel solid model is formulated from continuum mechanics for geometrically exact finite elements. A new partitioned fluid-structure interaction algorithm based on the Generalized-α method is formulated and implemented in a large scale fluids solver inside the FLASH framework. Consistent boundary conditions are also formulated by using Lagrangian particles. Several examples demonstrating the effectiveness of the methods and implementation are shown, in particular, for flapping flight at low Reynolds numbers. Unique experiments have also been undertaken to determine the first few natural frequencies and mode shapes associated with hawkmoth wings. The computational framework developed in this dissertation and the research findings can be used as a basis to understand the role of flexibility in flapping wing systems, further explore the complex dynamics of flapping wing systems, and also develop design schemes that might make use of nonlinear phenomena for performance enhancement