Micro Air Vehicles
Micro Air vehicles (MAVs) can generally be defined as small unmanned aircraft that are easily carried and operated by one person. Various numerical definitions exist of which the most popular are from the U.S. DARPA. They define a MAV as an air vehicle with a maximum physical dimension lesser than 15 cm (about 6 inches). MAVs are in most cases used to gather information using some sort of sensor and can be either remotely piloted or autonomous.
The smaller, the cheaper, the better. The development and miniaturization of electronics is allowing smaller aircraft to perform tasks previously performed by manned aircraft or larger UAVs. Simply put, the primary interest of MAVs is to reduce the cost of all forms of airborne data collection. A MAV is inexpensive to manufacture, requires minimal maintenance, is handled by one person, can be deployed within minutes, and is, due to its small size, harmless to its surroundings. Another factor, important from military sources, is that the smaller an aerial vehicle is, the harder it becomes to perceive. The latter reason is driving a trend toward creating MAVs in insect sizes.
The small size and minimal cost of operating MAVs opens up the possibility for many interesting mission types, both from a military and civilian point of view. The typical mission is some form of aerial reconnaissance using optical imagers, such as visual or infrared video cameras, but MAVs could just as well be used to gather data using chemical, biological, acoustic, or electromagnetic sensors. Only the imagination limits the possible uses for such vehicles.
Examples of missions:
- Police (hostage situations, anti terrorism actions, traffic monitoring, etc)
- Civil Rescue (search and rescue, disaster response, fire monitoring)
- Agriculture (monitoring crop health)
- Geographic information science (mapping, cartography etc)
- Military (reconnaissance, surveillance, targeting, bio chemical sensing)
Micro air vehicles are due to their small size limited in payload capacity and performance. They also operate at very low Reynolds numbers where the aerodynamics is complex and the aerodynamic efficiency is reduced. In order to create MAVs with practically useful performance, design optimization is very important, where the entire MAV including all sub systems is optimized for its specific mission requirement. MAVs need to be tailored for the sensors and equipment available at the time of deployment. Therefore "design on demand" is very attractive. For each type of mission, and sensor package, there is a unique, optimal, MAV design. The challenge is to find the best method to obtain that optimal design.
MAV Research at Linköping University
The goal of the MAV research at Linköping University is to provide a process for MAV design automation, where MAVs are automatically created, including fabrication, tailored for its specific task. In order to keep the cost at a minimum, off the shelf components are used to maximum extent.
To achieve this task a design framework incorporating several software tools is continually being developed. The framework interfaces a simple to use spreadsheet with a CAD system, an aerodynamic analysis code, an optimization tool, and a database storing information of hundreds of off the shelf components. The design process is automated using a multi objective Genetic Algorithm. During the process the optimal propulsion system components are selected from the database, the airframe is aerodynamically optimized and internal components are automatically positioned to ensure that the vehicle is as compact as possible while maintaining a center of gravity for proper longitudinal stability.
The output result is a large database of optimal designs relating to the different design objectives. An example is shown in the figure below where for a given sensor payload, endurance is expressed as a function of weight.
Each dot in the figure represent a full CAD design, an optimal combination of “off the shelf” propulsion system components, while meeting mission related performance requirements such as cruise speed, payload capacity, stall speed etc.
Several techniques have been tested for fabrication (such as foam plastic or composite materials) and with various degrees of automation. One method that stands out as especially suited for design automation is fabrication using 3D printer. Several MAVs have been printed directly in the university’s 3D printer and have been used for flight testing. Some examples are shown below.
For more information on this research see this list of publications
Last updated: Tue Aug 16 16:59:34 CEST 2011