Mission-Driven Simulation of a Multi-rotor Unmanned Aerial System for Energy Consumption Analysis

This paper presents a high-frequency dynamic model of a multi-rotor unmanned aerial system (UAS) that simulates mission-specific energy consumption and power-plant performance. The full aircraft model is discretized in blocks that model the subsystems, including the rotational dynamics, the propellers, motors and battery. Motors draw current from the battery to generate torque, resulting in rotation of propellers, which in turn generate thrust. The sum of each propeller thrust defines the attitude and motion of the aircraft. Energy losses are calculated for each subsystem, in order to accurately predict energy consumption and battery state-of-charge evolution. The dynamic model allows the inclusion of a cubic payload, which affects the drag and inertia of the vehicle. A mission controller accepts waypoints in three dimensional space as an input and low-level controllers control the speed of each propeller in order to produce the desired thrust. The model outputs the energy required to fulfill the given mission, as well as the states of each of the subsystems along the mission. Factors such as air density, temperature and stochastic atmospheric turbulence are modeled throughout the mission to include the effect of the environmental conditions. The UAS model is set up to simulate an actual hexacopter, running hover and cruise missions with various payloads carried in a box underneath the main body of the aircraft. The simulation results are then compared with the energy consumption values from real-world experiments. In the hover test, simulation results are within 4% of the experimental values. In the cruise test, the predicted energy consumption was relatively close to the experimental value, with a maximum discrepancy of 10% for the heaviest payload. It is therefore shown that the proposed mathematical model is capable of predicting mission-specific energy consumption within a low relative error range.