Modelling and trajectory generation of lighter-than-air aerial robots - Invited paper

Abstract

Lighter-than-air vehicles suit a wide range of applications, ranging from advertising, aerial photography, and survey work tasks. They are safe, cost-effective, durable, environmentally benign and simple to operate. Since their renaissance in early 1990's, airships have been increasingly considered for varied tasks such as transportation, surveillance, freight carrier, advertising, monitoring, research, and military roles. What makes a vehicle lighter than air is the fact that it uses a lifting gas (i.e. helium or hot air) in order to be lighter than the surrounding air. The principle of Archimedes applies in the air as well as under water. The difference between airships and balloons is that: balloons simply follow the direction of the winds; in contrast, airships are powered and have some means of controlling their direction. Non rigid airships or pressure airships are the most common form nowadays. They are basically large gas balloons. Their shape is maintained by their internal overpressure. The only solid parts are the gondola, the set of propeller (a pair of propeller mounted at the gondola and a tail rotor with horizontal axis of rotation) and the tail fins. The envelope holds the helium that makes the airship lighter than air. In addition to the lift provided by helium, airships derive aerodynamic lift from the shape of the envelope as it moves through the air. The most common form of a dirigible is an ellipsoid. It is a highly aerodynamic profile with good resistance to aerostatics pressure. © Springer-Verlag London Limited 2007.