BATMAV: A Biologically-Inspired Micro-Air Vehicle for Flapping Flight - Kinematic Modeling
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2007-12-04
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Abstract
The main objective of the BATMAV project is the development of a biologically inspired bat-like Micro-Aerial Vehicle with flexible and foldable wings, capable of flapping flight. This phase of the project starts with an analysis of several small-scale natural flyers from an engineering point of view with the objective to identify the most suitable platform for such a vehicle. Bats are shown to be very agile and efficient flyers with mechanical parameters well-suited to be realized with currently available muscle wire actuators allowing for close bio-inspired actuation. The second part of this thesis focuses on the kinematical analysis of the wing motion with the intent to develop a smart material (shape memory alloy) driven actuator system mimicking the functionality of the bat's relevant muscle groups in the future.
In the past decade Micro-Aerial Vehicles (MAV's) have drawn a great interest to military operations, search and rescue, surveillance technologies and aerospace engineering in general. Traditionally these devices use fixed or rotary wings actuated with electric DC motor-transmission, with consequential weight and stability disadvantages. SMA wire actuated flexible wings for flapping flight are promising due to increased energy density while decreasing weight, increased maneuverability and obstacle avoidance, easier navigation in small spaces and better wind gust stability. While flapping flight in MAV has been previously studied and a number of models were realized using light nature-inspired rigid wings, this paper presents a platform that features bat-inspired wings with flexible joints and muscle-wire actuation to allow mimicking the kinematics of the real flyer.
The bat was chosen after an extensive analysis of the flight physics of birds, bats and large insects. Typical engineering parameters such as wing loading, wing beat frequency etc. were studied and it was concluded that bats are a suitable platform that can be actuated efficiently using micro-scale Flexinol muscle wires. Also, due to their wing camber variation, they can operate effectively at a large range of speeds and allow remarkably maneuverable flight, avoiding obstacles while flying in small spaces (i.e. search and rescue missions).
In order to understand how to implement SMA "mechanical muscles" on a bat-like platform, the analysis was followed by a study of bat flight kinematics. Due to their complexity, from the engineering point of view, only a limited number of muscles were selected to actuate the flexible wing. A computer model of BATMAV platform incorporating SMA wires, wings and platform body, was created using SolidWorks software. The skeleton was subsequently fabricated using rapid prototyping technologies, and a novel joint technology was introduced which, replaces the complicated morphology of the natural flyers by a combination of superelastic SMA wires as flexible hinges. An extended analysis of flight styles in bats coordinated with image processing and inverse kinematics theory for robotic manipulators resulted in a collection of data for joint angles variation of the wing bone structure. These data implemented into the direct kinematics of the "robotic-like wing arm" helped to mimic the wingbeat cycle of the natural flyer.
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MAV, bats, Denovit-Hartenberg notation, flapping flight, kinematic modeling, shape memory alloys
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Degree
MS
Discipline
Mechanical Engineering
