Sensor Emplacement on Vertical Surfaces for a Biologically Inspired Morphing from Bats

S ITUATIONAL awareness is a criticality for decision-making that affects operations in urban environments. Accordingly, information about the system must be available through real-time measurements. Sensors can often be placed throughout a region using a mix of static mounts and moving vehicles; however, the ability to dynamically mount a sensor at any location in response to an event is difficult. A mission of particular interest is sensor emplacement onto vertical surfaces. Valuable information may be obtained from measurements, such as acoustic signatures or thermal images, from vantages that observe or overlookwindows and buildings along with areas of high traffic. Some obvious applications of surveillance include homeland security, fire monitoring, search and rescue, and analysis of structural integrity. In each situation, sensors must be strategically placed to provide the type of information from a specific aspect to maximize the situational awareness. A bat provides an obvious source of inspiration for this mission of sensor emplacement onto vertical surfaces within an urban environment. Its size and agility are ideal for maneuvering in small spaces. Most important, a bat is able to fly toward a wall or grating and attach itself to that surface. The bat undergoes a series of physical alterations as it transitions from flapping flight to gliding flight while approaching the wall. These alterations are mainly changes to the shape and configuration of the wings relative to the body. This concept of morphing to alter the physical configuration in flight is being incorporated into aircraft [1]. Incorporating actuators and other mechanisms can enable vehicles to vary parameters, such as sweep [2,3] and dihedral [4,5], duringflight. The resulting range of configurations will have an associated range of flight dynamics and, consequently, maneuvering. A micro air vehicle (MAV) is ideally suited for consideration of this mission and especially appropriate for consideration of a biologically inspired design given the similarity in size and airspeed to bats. Optimal design of such vehicles is generally difficult given the uncertainties associated with low Reynolds numbers [6,7]; however, adopting shapes from biological systems has generated some effective designs. Obviously, aerodynamics are an important feature of many biological systems [8], as demonstrated by testing in wind tunnels [9]. The concepts from avian systems have been studied for flight by considering pitching [10], expandable span [11], twojoint sweep [12], and even high-frequency flapping [13]. In each case, the study showed the efficiency and performance of the biological concept but were unable to realize the concept through an actual flight vehicle. ThisNote considers the design of amicro air vehicle using a bat for inspiration on morphing. The design does not consider the entire flight regime of a bat; rather, the design limits attention to the specific maneuver of sensor emplacement on a vertical surface. The effect of morphing the wings in a manner similar to bats is investigated and shown to be highly effective in achieving themaneuver. In particular, the aerodynamics are shown to alter by increasing agility in pitch and roll but remaining stable in yaw as a result of the morphing.