Load transportation system based on autonomous small size helicopters

This paper is devoted to modelling and control algorithms for a..ing load transportation system composed or one or multiple dicopters, where the load is coupled by the means of flexible ropes cc Fig. I). The coupled helicopter system overcomes the payload nitation of a single small size helicopter, while keeping most of its.vantages: small costs of operation, low maintenance costs and creased safeness. Therefore, the system can be utilised whenever c use of full size helicopters is impossible, too expensive or 'ohibited by law. We focus on the deployment and repairing of stributed sensor networks, using a transportation system based on ultiple small size helicopters. A possible real world application is c deployment of fire fighting equipment, where space limitation of c fire trucks prohibits the application of bigger UAVs and using II size helicopters is too dangerous. The problem of load transwtation using one or two full size helicopters (twin lift helicopter 'stem), connected to the load by means of flexible ropes, has been scussed in the aerospace research community at least since 1960. 'e have shown in our previous work that there is a fundamental ITerence in the mathematical description between small and full ze helicopters. Therefore, also the control design for the case of nall size helicopters needs to be different. To our knowledge, the mtrol of a slung load transportation system composed of multiple nall size helicopters has not been studied until now. In this paper, c complete mechanical setup of the slung load transportation 'stem based on one or more small size helicopters is presented. us includes a short description of the used UAVs, the additionally quire(' sensors, and how the load is mounted. A model of one/multiple he transporting a load is introduced. This model is used in a simplified form for the controller design and in full form for simulation. The controller for one and two helicopters. which is based on a state feedback controller, as well as the controller for three and more helicopters, which is based On a non linear controller, are explained in detail. Both controllers utilise an underlying non-linear orientation controller. We proposed feedback loop, based on forces measured in the ropes, to compensate for the influence of the rope. The controllers were tested in simulation and in real flight experiments. The world wide First flight experiment with three coupled helicopters was successfully conducted at the end of 2007.