Browsing by Author "Steele, Angus William Du Toit"

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    Development of a close quarters collision-protected aerial drone
    (Stellenbosch : Stellenbosch University, 2019-12) Steele, Angus William Du Toit; Engelbrecht, J. A. A.; Treurnicht, J.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: This thesis presents the design, implementation and verification of a close quarters, collisionprotected aerial drone. The ultimate goal of this work is to enable an unmanned aerial drone to navigate a given set of waypoints in a partially-known environment while avoiding collisions with unexpected obstacles. The airborne platform was selected and the avionics system was designed to satisfy the operational requirements for CECAD (Confined Environment Capable Aerial Drone), a collision-protected aerial drone that could be used for mapping partially-known and potentially hazardous spaces found in an underground mining environment. Following a survey of existing rotorcraft designs, an overlapping quadrotor configuration was selected for the vehicle, since it was deemed to be the most suitable for flight in narrow confined spaces. The PixHawk, open-source flight controller was chosen due to its integrated sensors and communication ports, well-developed open-source flight control software and its large community of users. Ultrasonics were chosen as the proximity sensors used for obstacle avoidance. Modelling and system identification of the actual vehicle were performed to create a representative mathematical model of the aircraft to be used for flight control design and verification. A complete flight control system was designed for the vehicle, and a waypoint navigation system with integrated obstacle avoidance was developed. The flight controllers were designed to provide tight position tracking and disturbance rejection, to enable stable flight and collision avoidance in a confined environment. A heading controller was added to keep the nose of the vehicle pointed generally in the direction of the vehicle’s direction of travel. The waypoint navigation system schedules a sequence of position waypoints for the flight controllers, while the integrated obstacle avoidance function superimposes an obstacle avoidance velocity command on the waypoint navigation velocity command. The system was implemented and verified in simulation using a simulation model that was created in Matlab and Simulink. Simulation models were created for the vehicle, the environment, the flight control system, and the waypoint navigation with obstacle avoidance. The simulation results show that the vehicle can successfully navigate waypoints in a partially-known environment while avoiding unexpected obstacles.