Robobee - A Bee Size Microdrone

Credit: seas.harvard.edu

Scientists for the last couple of decades had been trying to mimic the flight of insects. Ultimately they developed 'Robobee', a bee sized machine that can fly like an insect .Bees are incredible flying machine. Like bees, robobees have tiny bodies & can fly for at least 15 minutes maintaining stability during wind gusts & avoid predators. Further like bees robots can think on their own using miniature sensors & processors to process environmental cues to make decisions what to do next.

 Consider a rescue team of a box full of 500 robobees-a package weighing about 500 g is released at the site of the natural disaster to locate the survivors. Sensing the heat, sound or exhaled CO2 signature of survivors they would locate the survivors & send their coordinates to the central control station. The robotic group would coordinate their actions without relying on a single leader. If only, say, three of the robots accomplish their tasks while other fails, this is a success for the swarms. The cost of operation is very small compared to conventional method.

While analyzing the flight mechanism of a hovering moth in a wind tunnel , the researchers find that there is a tornado like vortex that run outwards along the leading edge of the wings. The remarkable stability of this leading edge vortex enables the wings of a bee to operate at angles of attack at which there is more lift . But at the same angle of attack an aircraft would stall. The robobees flap its wings at a frequency of only once in every 3 seconds which is calculated to reproduce the airflow & lift force of a hovering moth.

Presently robobees are having a wing span of about 160 mm, weighing about 50 gm & can fly for 15 minutes. It can perform vertical landings & take off & fly forward like a bee. Due to higher power requirement, spinning motors & gearbox cannot be used, instead piezoelectric actuators are used. One large power actuator oscillates the wings while smaller control actuators fine tune wing motions to generate torque for control & maneuvering. The wings can move in two ways : stroking back & forth & rotating their pitch. Piezo materials are a special type of ceramic that expands or contracts when a voltage is applied, generating motion & force. A solid-oxide micro fuel cell is the best device to power the robobees. In order to take stock of the situation & to decide on the best course of action & control its flight mechanism an electronic nervous system is integrated with the robobees. It handles basic control functions & a programmable electronics cortex to make high level decisions. They make the first real time computations required by the feedback control loop for stable flight while also staying within the strict power budget. High resolution camera is fitted in the front to take the picture & send it to the control station. When there is a swarm of robobees, operating them individually is not possible. A system is developed in which when an individual robobee is in switched on  position ,  it communicates with other members & make them active. Robobees could be released at the disaster site to locate the survivor, hunt the terrorists hidden in the jungle or in a building & also for commercial pollination in agriculture.

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