Doctoral Degrees (Electrical and Electronic Engineering)

Permanent URI for this collection

https://scholar.sun.ac.za/handle/10019.1/327

Browse

Browsing Doctoral Degrees (Electrical and Electronic Engineering) by Subject "Aeronautics -- Safety measures"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Cooperative collision avoidance strategies for unmanned aerial vehicles
    (Stellenbosch : Stellenbosch University, 2021-12) Meiring, Lauren; Engelbrecht, Japie; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: In this dissertation, a trajectory planning based cooperative collision avoidance system is proposed that provides integrated aircraft-to-aircraft collision avoidance and terrain avoidance for multiple independent UAVs. The UAVs use horizontal, vertical or three- dimensional manoeuvres to avoid short-term collisions with one another, with static ter- rain and with dynamic obstacles while minimising the deviation from their planned long term flight paths. Two existing strategies, namely a centralised strategy and a decoupled strategy, are ap- plied and a novel semi-centralised strategy is developed. The semi-centralised strategy is a hybridisation of the centralised and decoupled strategies. The semi-centralised strategy creates groups of UAVs involved in the same potential collisions and performs centralised trajectory planning for each group. The semi-centralised strategy is further developed into two variants, a semi-centralised expanding strategy and a semi-centralised token-passing strategy. The four cooperative collision avoidance strategies are implemented and tested in a sim- ulation environment. Monte Carlo simulations are performed to evaluate and compare their performances statistically. The trajectory planning strategies are compared using three performance metrics: their success rate at finding solutions, the optimality of the solutions in terms of the chosen cost function, and the time taken to find the solution. The results of the Monte Carlo simulations show that, given enough time, the centralised strategy always finds a solution, if it exists, and finds the optimal solution. However, it takes longer to find a solution. The decoupled strategy finds solutions the fastest. However, the decoupled strategy is not guaranteed to find a solution as its success is dependent on the UAV priority order used. The two semi-centralised strategies have a higher success rate and provide more optimal solutions than the decoupled strategy while finding solutions significantly faster than the centralised approach.