Stability and active control of low altitude aerostats

Resumo

Low altitude aerostats are usually uncontrolled and dependent on passive stability solutions-sometimes they do not have any. However, their low speed, the high turbulence and the gusts present in the lower boundary layer, as well as their large surface area bring the stability solution's theme into a foreground. This paper aims to survey common approaches to the stability problem when the aerostat is subjected to turbulent winds and gusts and compare them with new active control techniques, especially for low altitude aerostats. Addressed topics are: the dynamic modeling of tether and aerostat; comparison between different positions of the tether confluence point and analyses of elevator control demands. Conclusions are given to make the use of aerostats more reliable for operations with diverse electronic equipment which have tight requirements for oscillation and altitude changes.