Control of Quadrotor Unmanned Aerial Vehicles with Saturation and Time Delay

• Author / Creator

  Cao, Ning

• Unmanned Aerial Vehicles (UAVs) are receiving increasing interest from industry and academia due to their wide application in search and rescue, infrastructure inspection, and surveillance. This thesis focuses on research in the area of nonlinear control for rotary wing UAVs. Throughout this thesis, we design the controllers based on the inner-outer loop structure. The outer loop stabilizes translational variables and generates a reference roll and pitch signal which is fed to the inner loop. The benefits of the cascade structure include simplicity of implementation and ease of tuning. Due to physical constraints of actuators, e.g. UAV rotor speed, we consider motion control with input and state constraints. This work considers bounds on thrust, roll, and pitch. Unlike most of the existing work we use a body-frame representation for the dynamics outer loop design. This allows us to specify independent bounds for roll and pitch. The global asymptotic stability of the nested saturation-based outer loop is proven, and the stability of the inner-outer closed-loop is analyzed.

  Time delay has practical significance given it can negatively affect the stability of the system. For example, latency in the UAV communication can cause delay. We analyze the robustness of the nested saturation controller with respect to time delay using the emulation approach. A sufficient condition for stability in terms of the upper bound of time delay is derived. Since there is no compensation for delay in the controller design, this method is suitable for smaller delays. We also deal with time delay using prediction method. In this case, we design a predictor-based control for both motion control and visual servoing problems. Parameter uncertainty is also considered. Sufficient conditions for stability are given in terms of linear matrix inequalities (LMIs) for both problems. The abovementioned control designs and theory is experimentally validated on the Applied Nonlinear Control Lab (ANCL) indoor quadrotor platform.

• Subjects / Keywords

  • Quadrotor
  • UAV
  • saturation
  • delay

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R36W96R6B

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.