Backstepping Control Design for the Coordinated Motion of Vehicles in a Flowfield

Motion coordination of autonomous vehicles has applications from target surveillance to climate monitoring. Previous research has yielded stabilizing formation control laws for a self-propelled vehicle model with first-order rotational dynamics; however this model does not adequately describe the rotational and translational dynamics of vehicles in the atmosphere or ocean. This thesis describes the design of decentralized algorithms to control self-propelled vehicles with second-order rotational and translational dynamics. Backstepping controls for parallel and circular formations are designed in the absence of a flowfield and in a steady, uniform flowfield. Backstepping and proportional-integral controllers are then used to stabilize yaw in a rigid-body model. Feedback linearization is used to attain the desired forward speed. These formation control laws extend prior results to a more realistic vehicle model. Aside from the addition of new sensing and communication requirements, the second-order control laws are demonstrated to have comparable performance to the first-order controllers. The theoretical results are illustrated by numerical simulations

Automatic Collision Avoidance for Teleoperated Underactuated Aerial Vehicles using Telemetric Measurements

The paper deals with the obstacle avoidance problem for unmanned aerial vehicles (UAVs) operating in teleoperated mode. First, a feedback controller that we proposed recently for the stabilization of the UAV's linear velocity is recalled. Then, based on sensory measurements, a control strategy is proposed in order to modify the reference velocity on-line in the neighborhood of obstacles so as to avoid collisions. Both cases of telemetry and optical flow sensors are addressed. Stability properties of the proposed feedback controller are established based on a Lyapunov analysis. Simulations results are reported to illustrate the approach

Cascaded control for balancing an inverted pendulum on a flying quadrotor

SUMMARYThis paper is focused on the flying inverted pendulum problem, i.e., how to balance a pendulum on a flying quadrotor. After analyzing the system dynamics, a three loop cascade control strategy is proposed based on active disturbance rejection control (ADRC). Both the pendulum balancing and the trajectory tracking of the flying quadrotor are implemented by using the proposed control strategy. A simulation platform of 3D mechanical systems is deployed to verify the control performance and robustness of the proposed strategy, including a comparison with a Linear Quadratic Controller (LQR). Finally, a real quadrotor is flying with a pendulum to demonstrate the proposed method that can keep the system at equilibrium and show strong robustness against disturbances.</jats:p

Analysis and Realization of a Dual-Nacelle Tiltrotor Aerial Vehicle

Unmanned aerial vehicles are a salient solution for rapid deployment in disaster relief, search and rescue, and warfare operations. In these scenarios, the agility, maneuverability and speed of the UAV are vital components towards saving human lives, successfully completing a mission, or stopping dangerous threats. Hence, a high speed, highly agile, and small footprint unmanned aerial vehicle capable of carrying minimal payloads would be the best suited design for completing the desired task. This thesis presents the design, analysis, and realization of a dual-nacelle tiltrotor unmanned aerial vehicle. The design of the dual-nacelle tiltrotor aerial vehicle utilizes two propellers for thrust with the ability to rotate the propellers about the sagittal plane to provide thrust vectoring. The dual-nacelle thrust vectoring of the aerial vehicle provides a slimmer profile, a smaller hover footprint, and allows for rapid aggressive maneuvers while maintaining a desired speed to quickly navigate through cluttered environments. The dynamic model of the dual-nacelle tiltrotor design was derived using the Newton-Euler method and a nonlinear PD controller was developed for spatial trajectory tracking. The dynamic model and nonlinear PD controller were implemented in Matlab Simulink using SimMechanics. The simulation verified the ability of the controlled tiltrotor to track a helical trajectory. To study the scalability of the design, two prototypes were developed: a micro scale tiltrotor prototype, 50mm wide and weighing 30g, and a large scale tiltrotor prototype, 0.5m wide and weighing 2.8kg. The micro scale tiltrotor has a 1.6:1 thrust to weight ratio with an estimated flight time of 6 mins in hover. The large scale tiltrotor has a 2.3:1 thrust to weight ratio with an estimated flight time of 4 mins in hover. A detailed realization of the tiltrotor prototypes is provided with discussions on mechanical design, fabrication, hardware selection, and software implementation. Both tiltrotor prototypes successfully demonstrated hovering, altitude, and yaw maneuvering while tethered and remotely controlled. The developed prototypes provide a framework for further research and development of control strategies for the aggressive maneuvering of underactuated tiltrotor aerial vehicles