Dynamic Modelling of Multi-Body Unmanned Airship with a Slung-Payload

Unmanned aerial vehicles (UAV) provide a conve-nient way to conduct experiments and simulations at a low cost. After a long period of being relinquished, interest in airships has resurged owing to stringent CO2 emissions regulations and the increasing market demand on air cargo. This paper discusses the application of Udwadia-Kalaba technique to model the dynamics of a reconfigurable unmanned airship. The investigated multi-body consists of an airship, a gondola, and a payload. The investigated airship is designed to have a movable gondola. This novel design overcomes a major issue that conventional airships encountered which is a mechanism to improve the manoeuvrability of the airship. Modelling of multi-body system can be difficult when non-holonomic constraints are present. Three constraints were identified for the investigated system. Position and orientation constraints between the airship and gondola were first derived. In addition, a length constraint between the gondola and slung-payload was enforced. Udwadia-Kalaba method was used to model the multi-body system. The equations of motion are solved numerically for a test case where a step side force is applied for 1 second. The resulting trajectory over a period of 7 seconds was presented and analysed. Physical modes such as pendulum-like behaviour of slung-payload and coupling between the multi-body components were captured in the simulations and discussed.