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Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14901/696

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Browsing Scopus İndeksli Yayınlar Koleksiyonu by Author "Acar, L."

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    Article
    Citation - WoS: 15
    Citation - Scopus: 23
    Hybrid Consensus-Based Control of Nonholonomic Mobile Robot Formation
    (Springer, 2017) Guzey, Haci Mehmet; Dierks, T.; Jagannathan, S.; Acar, L.
    This paper addresses the hybrid consensus-based formation keeping problem for nonholonomic mobile robots in the presence of a novel time-varying, composite, nonlinear velocity-tracking error system. First, continuous-time regulation and consensus-based formation controllers are developed for a group of wheeled mobile robots. These controllers are then used to create a hybrid automaton, which drives the robots to their goal positions while maintaining a specified formation.In order to avoid the hard switches between regulation and formation keeping controllers, a novel blended velocity tracking error approach is proposed in this work to create nonlinear, time-varying velocity error dynamics. Therefore, the hybrid controller consists of two discrete modes, each with continuous dynamics, and the novel blended velocity tracking error approach provides a smooth transition between each mode. The controller in the regulation mode drives the robot to a goal position while the formation keeping controller ensures that the robots achieve a specified geometric formation prior to reaching their goal-position. Time-varying Lyapunov functions are used to rigorously demonstrate that the formation errors converge to a small bounded region around the origin and the size of the bound can be adjusted by using the switching conditions. Convergence to goal position while in formation is also demonstrated in the same Lyapunov analysis illustrating that the robots are converging to their goal positions while operating in both regulation and formation keeping mode. Simulation results verify the theoretical conjectures.
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    Article
    Citation - WoS: 35
    Citation - Scopus: 49
    Modified Consensus-Based Output Feedback Control of Quadrotor UAV Formations Using Neural Networks
    (Springer, 2019) Guzey, H. M.; Dierks, T.; Jagannathan, S.; Acar, L.
    In this paper, a novel nonlinear output feedback neural network (NN)-based consensus controller is developed for a group of quadrotor unmanned aerial vehicles (UAVs). One UAV in the group tracks a desired trajectory while the rest of the group uses consensus-based formation controllers without knowledge of the desired trajectory. Each UAV estimates its own and its neighbor's velocities through a novel nonlinear NN-based observer by using position and orientation information. Neighboring UAV positions and orientation information is assumed to be available via wireless communication or obtained through local sensors. Since quadrotor UAVs have six degree of freedom with only four control inputs, the UAV's pitch and roll angles are utilized as virtual control inputs to bring all UAVs to consensus points along x and y directions. The Lyapunov stability theorem is utilized to demonstrate that all the position errors, orientation errors, velocity tracking errors, observer estimation errors, and NN weight estimation errors are semi-globally uniformly ultimately bounded (SGUUB) in the presence of bounded disturbances. The effectiveness of our consensus-based output feedback formation control of quadrotor UAVs is demonstrated in simulation validating our theoretical claims.