Development of a close quarters collision-protected aerial drone

Steele, Angus William Du Toit (2019-12)

Thesis (MEng)--Stellenbosch University, 2019.

Thesis

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.

AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwerp, implementering, en verifikasie van ’n naby-kwartiere, botsingbeskermde hommeltuig. Die uiteindelike doel van die navorsing is om ’n onbemande hommeltuig in staat te stel om ’n gegewe stel wegpunte in ’n gedeeltelik-bekende omgewing te navigeer en terselfdertyd botsings met onverwagte hindernisse te vermy. Die lugraam is gekies en die vlugelektronika is ontwerp om die operasionele vereistes te bevredig vir CECAD ("Confined Environment Capable Aerial Drone"), ’n botsing-beskermde onbemande hommeltuig wat gebruik kan word om gedeeltelik-bekende en potensieël gevaarlike ruimtes in ’n ondergrondse myn omgewing te karteer. Nadat ’n studie gemaak is van bestaande rotortuig ontwerpe, is ’n oorvleuelde, vier-rotor konfigurasie gekies as die mees geskikte konfigurasie vir vlug in smal inperkende ruimtes. Die PixHawk oopbron vlugbeheerder is gekies op grond van sy geïntegreerde sensore en kommunikasiepoorte, goed-ontwikkelde oopbron vlugbeheer sagteware, en sy groot gebruikersgemeenskap. Ultrasoniese sensore is gekies as die nabyheid sensore wat gebruik sal word vir hindernisvermyding. Modellering en stelselidentifikasie van die werklike voertuig is uitgevoer om ’n verteenwoordigende wiskundige model van die onbemande voertuig te skep, sodat dit gebruik kan word vir vlugbeheer ontwerp en verifikasie. A volledige vlugbeheerstelsel is ontwerp vir die voertuig, en ’n wegpunt navigasie stelsel met geïntegreerde hindervermyding is ontwikkel. Die vlugbeheerders is ontwerp om goeie posisievolging en steurseinverwerping te verskaf, ten einde stabiele vlug en botsingvermyding in ’n inperkende omgewing moontlik te maak. ’n Gierhoek beheerder is bygevoeg om die neus van die voertuig gemiddeld in dieselfde rigting as die voertuig se rigting van beweging te hou. Die wegpunt navigasie stelsel skeduleer ’n reeks van posisie wegpunte vir die vlugbeheerders, terwyl die geïntegreerde hindernisvermyding funksie ’n hindernisvermyding snelheidsvektor superponeer op die wegpunt navigasie snelheidsbevel. Die stelsel is geïmplementeer en geverifeer in simulasie deur gebruik te maak van ’n simulasiemodel wat geskep is in Matlab en Simulink. Simulink modelle is geskep vir die voertuig, die omgewing, die vlugbeheerstelsel, en die wegpunt navigasie stelsel met hindernisvermyding. Die simulasie resultate wys dat die voertuig suksesvol die wegpunte kan navigeer in ’n gedeeltelik-bekende omgewing terwyl dit onverwagte hindernisse vermy.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107108
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