Quadcopter

Introduction

The quadcopter rig consists of a quadcopter mounted on a stanchion. The control objective is to regulate the speed of the motors to maintain a hover position that is horizontal to the rig's base plate.

2018 - Jonathan van Niekerk

Build The quadcopter is based on a commercially available F450 frame and Arduino Uno controller. A LiPo battery provides flight autonomy of about 15 min and the high current capacity required by the motors. The motors are fitted with 1045 propellers capable of providing the required thrust force to overcome gravity. Electronic speed controllers convert pulse width modulated signals from the Arduino Uno to 3-phase alternating current signals required to drive the motors. The measured angles are derived from a gyroscope and accelerometer mounted on the quadcopter base. The gyroscope and accelerometer needs to be calibrated after power is lost to the inertial measurement unit. The rig is required to prevent the quadcopter from damaging itself during trials, to prevent injury to students and to harness the quadcopter should the control system fail and the system become unstable.

Modelling The quadcopter is modelled mathematically from angular velocity, Euler kinematic, velocity and position state equations. A linear model is derived based on small angle deviations around the point of equilibrium. Equilibrium is when the roll, pitch and yaw angles are zero. Step test experiments are performed to validate the mathematical model, and curves are fitted to obtain the transfer function models.

Control Controllers were designed based on the H-inf mixed sensitivity and SIMC methods. Controllers based on the fitted transfer functions achieved better results that those based on mathematical models.