An Open-Loop Trajectory Implementation for Free Fall to Powered Flight Transition for Multirotor Aircraft
Open Access
- Author:
- Rosenberger, Tyler
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 10, 2020
- Committee Members:
- Jacob Willem Langelaan, Thesis Advisor/Co-Advisor
Amy Ruth Pritchett, Program Head/Chair
Eric Norman Johnson, Committee Member
Puneet Singla, Committee Member - Keywords:
- Particle Swarm Optimization
Trajectory Design
PSO
Heuristic
Quadcopter
Quadrotor
Gazebo
ROS
Controls
Implementation
Free Fall
Optimization
Open-Loop - Abstract:
- Parachute release of rotorcraft presents a relatively unexplored method of vehicle deployment. This release method presents significant challenges in both modelling and control of quadrotor vehicle motion. The largest of these problems involves the occurrence of vortex ring state during high-falling-velocity maneuvers. Without proper control methodology, a falling rotorcraft can become unstable - and in some cases uncontrollable - if vortex ring state is allowed to develop. This thesis seeks to stabilize and control a falling quadrotor through the use of an intermediate open-loop stage of control before passing full control over to a closed-loop controller. This is accomplished by pre-generating a trajectory maneuver involving a sequence of pitch and body z-axis acceleration commands in an attempt to regain thrust while rapidly descending. These trajectories are generated using a series of heuristically-motivated polynomial splines that seek to mimic the trained behavior of human helicopter pilots. Optimization of the governing trajectory parameters is then explored through the use of particle swarm optimization in MATLAB. The peak pitch angle and time of maximum thrust are found using the PSO algorithm, and the robustness of the solutions is then examined. Following MATLAB optimization, the trajectory is implemented within a Gazebo simulation environment through the use of ROS. The simulation environment and vehicle model are changed to match the flight conditions of a ready-to-fly testbed vehicle, the AVIA Lab-constructed Hoverfly. Multiple trials are conducted for various final conditions to test the effectiveness of the proposed open-loop control methodology. The presented open-loop control method is shown to allow successful control of a dropped quadrotor vehicle. The designed trajectories are shown to reliably and predictably force the vehicle into an easier-to-control state that allows a traditional closed-loop controller to achieve both a zero-velocity hover and forward-flight condition at the end of the maneuver.