Design of Super twisting Sliding Mode Controller for Hovering Stabilization of Tricopter UAV
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Date
2016-05
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Addis Ababa University
Abstract
Unmanned Aerial Vehicles (UAVs) have attracted growing attention in research due to their wide applications. UAVs include many devices such as qua-copter, hexa-rotor, heli-copter, Tricopter. Among them, Tricopter is proposed in this thesis. It has three rotor axes that are equidistant from its center of gravity. Tricopter UAV is multivariable, nonlinear, unstable and under-actuated system. This thesis concentrates on the control and simulation of a Tricopter unmanned aerial vehicle. First coordinate systems with transformation matrix and mathe-matical models are derived based on Newton-Euler formulation technique. By using these equations, we are able to derive the mathematical model to simulate in MATLAB/Simulink environment for the purposes of altitude and attitude control for hovering stabilization of the Tricopter. The Control strategy used is Proportional Integral Derivative (PID) and the Super Twisting Sliding Mode Control (STSMC). STSMC is a viable alternative to the conventional first order sliding mode control for the systems of relative degree-1 in order to avoid chat-tering without affecting the tracking Performance. The PID and STSMC are mathematically derived, and their performance is verified by simulation. Simula-tion results show that the PID controller can maintain the stability of the Euler angles (roll angle, pitch angle, yaw angle). STSMC has been implemented for altitude control. The altitude settles at approximately 2 seconds with no over-shoot and steady state error of 2mm. The proposed STSMC is robust against parameter variation of 10% and able to overcome disturbances and maintain a given height position for hovering Stabilization of Tricopter.
Key Words: Attitude Stabilization, PID controller, Super twisting Sliding Mode Control (STSMC), UAV Tricopter, Hovering.
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Attitude Stabilization; PID controller; Super twisting Sliding Mode Control (STSMC); UAV Tricopter; Hovering