Automated landing of a quadrotor Unmanned Aerial Vehicle on a translating platform

Moller, Paul Daniel Stefanus (2015-12)

Thesis (MSc)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: In this thesis the design, implementation and practical testing of an autolanding system responsible for landing a quadrotor Unmanned Aerial Vehicle (UAV) on a moving platform are presented. The goal of the system was to land the quadrotor used in the Surface Launched Aerial Decoy electric (SLADe) project autonomously on the deck of a moving ship. The quadrotor, which is designed completely in-house in the Electronic Systems Laboratory at the University of Stellenbosch, has full autonomous flight capabilities and has a payload carrying capacity of 6 kg. This thesis specifically concentrates on the translational movement of the ship deck, and not rolling, pitching and heaving motion. The goal of the project was successfully obtained through modification of the quadrotor’s flight control system as well as the Differential Global Position System (DGPS) sensing method of the platform and the UAV, and through implementation of a state machine that guided the aircraft through the autolanding procedure. The flight control system of the UAV was thoroughly analysed, and shortcomings in the control system for this project were identified. The flight control system was not capable of tracking a moving platform with zero steady-state error and lacked disturbance rejection. The shortcomings were amended by modifying the architecture and increasing the bandwidth of the control loops responsible for horizontal velocity and horizontal position control of the UAV. A fundamental change was made to the aircraft’s positional sensing method, expanding the DGPS capabilities of the vehicle. The DGPS, which is manufactured by Novatel, was modified to provide centimetre-level accurate relative position measurements between the platform and the UAV. The modifications allowed for accurate control of the position of the UAV relative to the moving platform. A state machine was implemented to safely guide the quadrotor through the landing procedure. The state machine consists of four consecutive states, and incorporates several safety checks to ensure that the quadrotor touches down safely within the required bounds. The quadrotor successfully performed autonomous landings on a translating platform at speeds of 10, 20 and 30 km/h, and touched down within 36 cm of the designated landing mark.

AFRIKAANSE OPSOMMING: In hierdie tesis word die ontwerp, implementering en praktiese toetsing aangebied van ’n outomatiese landingstelsel wat verantwoordelik is vir die landing van ’n vierrotor- onbemande vliegtuig op ’n bewegende platform. Die doelwit van die stelsel was om die vierrotor wat in die projek genaamd "Surface Launched Aerial Decoy electric"(SLADe) gebruik is, outonoom op die dek van ’n bewegende skip te land. Die vierrotor, wat in sy geheel in die Universiteit Stellenbosch se Elektroniese Stelselslaboratorium ontwerp is, het ten volle outonome vlugvermoë en ’n loonvrag-drakapasiteit van 6 kg. Hierdie tesis konsentreer spesifiek op die translasionele beweging van die skipdek, en nie die rol-, hei- of dein-bewegings nie. Die doelwit van die projek is suksesvol bereik deur aanpassings te maak aan die vierrotor se vlugbeheerstelsel asook aan die Differensiële Globale Posisioneringstelsel-waarnemingsmetode van die platform en die onbemande vliegtuig, en deur die implementering van ’n toestandsmasjien wat die vliegtuig deur die outomatiese landingsprosedure kon lei. Die vlugbeheerstelsel van die onbemande vliegtuig is deeglik ontleed, en tekortkominge in die beheerstelsel van die projek is geïdentifiseer. Die vlugbeheerstelsel was nie in staat om ’n bewegende platform te volg met ’n bestendigetoestandsfout van nul nie, en het ’n gebrek aan steuringsverwerping getoon. Die tekortkominge is aangespreek deur die argitektuur aan te pas en die bandwydte te verhoog van die beheerlusse wat verantwoordelik is vir die horisontale snelheid en horisontale posisiebeheer van die onbemande vliegtuig. ’n Fundamentele verandering is aan die vliegtuig se posisiewaarnemingsmetode aangebring om die DGPSvermoë van die voertuig uit te brei. Die DGPS, wat deur Novatel vervaardig word, is aangepas om relatiewe posisiemetings met sentimetervlak-akkuraatheid te kan voorsien tussen die platform en die onbemande vliegtuig. Die aanpassings het die akkurate beheer van die posisie van die onbemande vliegtuig relatief tot die bewegende platform moontlik gemaak. ’n Toestandsmasjien is geïmplementeer om die vierrotor veilig deur die landingsprosedure te lei. Die toestandsmasjien bestaan uit vier opeenvolgende toestande, en inkorporeer verskeie veiligheidstoetse om te verseker dat die vierrotor veilig binne die vereiste grense land. Die vierrotor het suksesvol outonome landings op ’n translerende platform uitgevoer teen 10, 20 en 30 km/h, en het binne 36 cm van die aangewese landingsmerk neergestryk.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98014
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