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System identification and optimal control of a small-scale unmanned helicopter / Marthinus Christoffel Terblanche

The use of rotary winged unmanned aerial vehicles in military and civilian applications is rapidly
increasing. The primary objective of this study is to develop an automatic flight control system for a
radio controlled (RC) helicopter. There is a need for a simple, easy to use methodology to develop
automatic flight controllers for first-flight. In order to make the work accessible to new research
groups without physical helicopter platforms, a simulation environment is created for validation.
The size 30 RC helicopter in AeroSIMRC is treated as the final target platform. A grey box, timedomain
system identification method is used to estimate a linear state space model that operates
around hover. Identifying the unknown parameters in the model is highly dependent on the initial
guess values and the input data. The model is divided into subsystems to make estimation possible.
A cascaded controller approach is followed. The helicopter’s fast angular dynamics are separated
from the slower translational dynamics. A linear quadratic regulator is used to control the
helicopter’s attitude dynamics. An optimised PID outer-loop generates attitude commands from a
given inertial position trajectory. The PID controllers are optimised using a simplex search method.
An observer estimates the unmeasured states such as blade flapping. The controller is developed in
Simulink®, and a plug-in written for AeroSIMRC enables Simulink® to control the simulator
through a UDP interface to validate the model and controller.
The identified state space model is able to accurately model the flight data from the simulator. The
controllers perform well, keeping the helicopter stable even in the presence of considerable
disturbances. The attitude controller’s performance is validated using an aeronautical design
standard (ADS-33E-PRF) for handling qualities. The trajectory tracking is validated in a series of
simulator flight tests. The linear controller is able to sustain stable flight in constant winds of up to
60% of the helicopter’s maximum airspeed. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014
Date January 2014
CreatorsTerblanche, Marthinus Christoffel
Source SetsNorth-West University
Detected LanguageEnglish

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