@article{AliMontenegro2016,
  author    = {Ali, Qasim and Montenegro, Sergio},
  title     = {Decentralized control for scalable quadcopter formations},
  series = {International Journal of Aerospace Engineering},
  volume    = {2016},
  journal   = {International Journal of Aerospace Engineering},
  doi       = {10.1155/2016/9108983},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-146704},
  pages     = {9108983},
  year      = {2016},
  abstract  = {An innovative framework has been developed for teamwork of two quadcopter formations, each having its specified formation geometry, assigned task, and matching control scheme. Position control for quadcopters in one of the formations has been implemented through a Linear Quadratic Regulator Proportional Integral (LQR PI) control scheme based on explicit model following scheme. Quadcopters in the other formation are controlled through LQR PI servomechanism control scheme. These two control schemes are compared in terms of their performance and control effort. Both formations are commanded by respective ground stations through virtual leaders. Quadcopters in formations are able to track desired trajectories as well as hovering at desired points for selected time duration. In case of communication loss between ground station and any of the quadcopters, the neighboring quadcopter provides the command data, received from the ground station, to the affected unit. Proposed control schemes have been validated through extensive simulations using MATLAB®/Simulink® that provided favorable results.},
  language  = {en}
}
@article{AliMontenegro2016,
  author    = {Ali, Qasim and Montenegro, Sergio},
  title     = {Explicit Model Following Distributed Control Scheme for Formation Flying of Mini UAVs},
  series = {IEEE Access},
  volume    = {4},
  journal   = {IEEE Access},
  number    = {397-406},
  doi       = {10.1109/ACCESS.2016.2517203},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-146061},
  year      = {2016},
  abstract  = {A centralized heterogeneous formation flight position control scheme has been formulated using an explicit model following design, based on a Linear Quadratic Regulator Proportional Integral (LQR PI) controller. The leader quadcopter is a stable reference model with desired dynamics whose output is perfectly tracked by the two wingmen quadcopters. The leader itself is controlled through the pole placement control method with desired stability characteristics, while the two followers are controlled through a robust and adaptive LQR PI control method. Selected 3-D formation geometry and static stability are maintained under a number of possible perturbations. With this control scheme, formation geometry may also be switched to any arbitrary shape during flight, provided a suitable collision avoidance mechanism is incorporated. In case of communication loss between the leader and any of the followers, the other follower provides the data, received from the leader, to the affected follower. The stability of the closed-loop system has been analyzed using singular values. The proposed approach for the tightly coupled formation flight of mini unmanned aerial vehicles has been validated with the help of extensive simulations using MATLAB/Simulink, which provided promising results.},
  language  = {en}
}
@inproceedings{AliMontenegro2015,
  author    = {Ali, Qasim and Montenegro, Sergio},
  title     = {A Simple Approach to Quadrocopter Formation Flying Test Setup for Education and Development},
  series = {INTED2015 Proceedings},
  booktitle = {INTED2015 Proceedings},
  publisher = {International Academy of Technology, Education and Development (IATED)},
  isbn      = {978-84-606-5763-7},
  issn      = {2340-1079},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-114495},
  pages     = {2776 -- 2784},
  year      = {2015},
  abstract  = {A simple test setup has been developed at Institute of Aerospace Information Technology, University of W{\"u}rzburg, Germany to realize basic functionalities for formation flight of quadrocopters. The test environment is planned to be utilized for developing and validating the algorithms for formation flying capability in real environment as well as for education purpose. An already existing test bed for single quadrocopter was extended with necessary inter-communication and distributed control mechanism to test the algorithms for formation flights in 2 degrees of freedom (roll / pitch). This study encompasses the domain of communication, control engineering and embedded systems programming. Bluetooth protocol has been used for inter-communication between two quadrocopters. A simple approach of PID control in combination with Kalman filter has been exploited. MATLAB Instrument Control Toolbox has been used for data display, plotting and analysis. Plots can be drawn in real-time and received information can also be stored in the form of files for later use and analysis. The test setup has been developed indigenously and at considerably low cost. Emphasis has been placed on simplicity to facilitate students learning process. Several lessons have been learnt during the course of development of this setup. Proposed setup is quite flexible that can be modified as per changing requirements.},
  subject      = {Flugk{\"o}rper},
  language  = {en}
}