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A few years ago, micro-aerial vehicles were a model building affair, but things have since changed. The MD4-200 developed by the German company Microdrones is a state-of-theart achievement with eagle-eye performance.
(Published on June 2008 – JEC Magazine #41)
The insect-like exo-skeleton design of this microdrone uses composites because weight has a major impact on flight times.
The structural architecture of the MD4-200 uses epoxy resin reinforced with carbon fibre and carbon nanotubes (figure 1). The 700x700 mm structure (axis to axis) takes advantage of the composite’s high mechanical strength to reduce weight. The resin is formulated by the French Company Nanoledge which specializes in the integration of nanoparticles into composites. Nanoledge develops innovative new resin systems based on nanoparticles fillers to improve the damage tolerance and electrical conductivity of resins. The fillers used here are Baytubes® C 150 P from Bayer MaterialScience AG. Baytubes are multi-wall carbon nanotube agglomerates with a small outer diameter (an average of 13 to 16 nm in this case), a narrow diameter distribution and an ultrahigh aspect ratio (length-to-diameter ratio, here the length ranges between 1 and 10 μm). These carbon nanotubes show excellent tensile strength and E-modulus, as well as exceptional thermal and electrical conductivity. This carbon monoframe is already a perfect shield against electromagnetic interferences and nanotubes only improve on this characteristic (figure 2).
This rotary-wing aircraft is also equipped with four 370 mm long carbon blades. These blades are removed in case of impact to avoid injuring people. They can also be replaced easily and quickly.
The MD4-200 is a VTOL AUMAV. VTOL stands for Vertical Take Off and Landing, and AUMAV for Autonomous Unmanned Micro Aerial Vehicle. The machine weighs only 900 grams. Its Altitude and Attitude and Heading Reference System (AAHRS) uses accelerometers, gyroscopes and magnetometers, as well as air pressure, humidity and temperature sensors. Thus, it can be remote controlled and operated autonomously by GPS waypoint navigation. The machine can stabilise itself. Its security features, such as autonomous landing on low battery or missing radio signal, prevent it from crashing. According to Microdrones, even inexperienced people can learn to fly the machine in one hour. The highly effective propulsion system produces very little noise, less than 62 dBA at 3 metres distance. With the optional video glasses, the operating range can reach up to 500 metres. Depending on the payload and temperature, the flight duration can reach 20 minutes with its four Li-polymer batteries.
Flying eyes and more
Sharp pictures can be obtained under a wind of 4 metres per second. The drone is used in many different applications up to 150 m from the ground: aerial photography, archaeology, surveillance, plant inspection, fire and rescue services, border control, police, special forces, army, etc. A modular payload concept with a 200 gram capacity allows the drone to be individually equipped for different tasks, e.g.: with a high-resolution digital camera, a daylight colour video sensor, a video sensor near infra-red spectrum, a bolometer, a radio relay station, measuring instruments, etc. The video receiver with an optional notebook can be used for observing and recording any type of mission and duplicating the data on to a CD or DVD.