Multirotors, including quadrotors, can be considered as the most widely used and commercial type of unmanned aerial vehicles (UAV) in recent years. Relatively simple structure, easy control and wide range of definable missions and reasonable price for this type of drones can be counted among the factors that have made them popular. Despite the listed advantages, this type of UAVs has disadvantages and limitations, including low flight endurance, weaker stability in the face of wind and disturbances, as well as less fault tolerance capability. In order to reduce the mentioned defects, a quadrotor with the ability to positioning its rotors has been introduced, and each of the rotors can be positioned linearly along the arm axis of that rotor. This feature Provides more flexibility to extends the effective value of the control inputs than the usual case where only the changes in the rotational speed of the rotors are possible. In the present study, at the beginning, the dynamic equations of motion of the proposed quadrotor have been extracted by considering that the rotor positioning capability, through calculating the derivative of the linear and angular momentums. In the following, two types of adaptive finite time sliding mode and fuzzy controllers are developed for this UAV and investigated and eva‎luated in different conditions. In the adaptive controller, rotor positioning is done by mapping from roll and pitch controller inputs in four stage filter. Using by four-step modification of this signal, the position and speed of each rotor are calculated and adjusted according to the limitations of the operators. In the second controller, which is developed based on the fuzzy law, the positioning of the rotors is done by employing the control allocation approach which bases on the log barrier convex optimization method. In addition, fuzzy fault tolerance by employing rotor positioning is also considered in the case with that fault leads to the decrease the lift force of the propulsion system. In the performed simulations, the positive effect of rotor positioning on energy consumption and quadrotor stability against disturbances compared to the conventional quadrotors are simulated. In addition, the positive effect of rotor positioning for higher fault tolerance is shown in the simulations. Moreover, by making a prototype of the rotor positionable quadrotor, experimental tests are also been performed and the results of the simulations in the field of energy consumption and stability in the presence of disturbance are confirmed.

محمد دانش

ايمان ايزدي نجف آبادي

مهدي كشميري , سعيد بهبهاني , حميدرضا كوفيگر