Symmetric Linear Systems

A major limitation to the use of helicopters in heavy construction has been that the masses that can be effectively and safely transported are restricted. One solution was the construction of the so-called heavy-lift helicopters. However it has been established that there are physical and economic limitations to the payload that can be transported. It has been proposed to circumvent this limitation by using multiple helicopters to move a single mass. The concept has been flight tested for two helicopters (twinlift) and the results were encouraging but showed that automatic control would be necessary to make the concept successful. In this paper the authors present some initial models and explore some of the control-theoretic problems inherent in the twinlift problem. A simplified linear model is examined, and it is shown that certain natural control schemes are not feasible, but that it is possible to control the linear model while preserving the essential characteristics of twinlift profile.