Past Research Projects

H-Infinity Controller Testing for Wind Disturbance Rejection of a Homogeneous Octorotor UAV

ME Research, 2022 – 2023

Junyi Chen. Supervisor: Karl Stol

Stable station keeping performance of UAVs is an area of interest for many close-to-environment applications, particularly when interaction between the UAV and its environment is involved. Conventional underactuated quadrotor UAVs have been found to be incapable of the stability required for these applications due to their inherently coupled dynamics. As such, alternative physical designs and control techniques must be considered.

A position controller designed through H-infinity methods has been found to be robust to external disturbances and able to take advantage of the over-actuated capabilities of drones designed with a fixed rotor cant angle. The intent of this research is to validate the performance of a controller designed through H-Infinity methods on a canted-rotor octo-rotor UAV in various wind conditions.

Related: Enabling Unmanned Aerial Vehicles (Drones) to use Tools in Complex Dynamic Environments

Autonomous Surveying of Plantation Forests using Multi-Rotor UAVs

PhD Research, 2018 – 2022

Tzu-Jui Lin. Supervisors: Karl Stol & Bruce MacDonald

Modern plantation forest procedures still rely heavily on manual data acquisition in the inventory process, limiting the quantity and quality of the collected data. This limitation in collection performance is often due to the difficulty of traversing the plantation forest environment on foot.

Thus, this work presents a UAV system capable of autonomously surveying a plantation forest environment using optimization-based trajectory planning and model predictive control based trajectory tracking. Finally, flight testing in an uncontrolled plantation forest validates the proposed systems in its intended operating environment.

Watch: Autonomous navigation through a plantation forest

Dynamics and Control of Aerial Vehicles for Prolonged Physical Interaction

PhD Research, 2018 – 2022

Pedro Mendes. Supervisors: Karl Stol & Jaspreet Dhupia

Aerial manipulation poses complex challenges for aircraft design, model, and control. This research investigates and presents solutions for compliant physical interactions when the coupled dynamics are distinctly different from free-flight conditions. Analytical, numerical, and experimental tools are used to develop aerial vehicles and controllers capable of accommodating these difficulties while maintaining performance and stability. Furthermore, a case study for tree branch manipulation demonstrates the practical feasibility and effectiveness of the designed platform and conceptual framework.

Watch: Asymmetric branch separation.

Watch: Rolled branch separation.

Related: Enabling Unmanned Aerial Vehicles (Drones) to use Tools in Complex Dynamic Environments

Wind Disturbance Rejection on an Over-Actuated Drone using Model Predictive Control

BE(Hons) Research Project, 2022

Caleb Probine & David Yang. Supervisors: Karl Stol & Nicholas Kay

Model Predictive Control makes predictions about the future trajectory of the drone and  finds the optimal input to achieve that prediction. This controller differs from others because it can see the physical constraint of the motors (i.e. maximum power they can output) and take that into account when finding the optimal solution. 

The objective of this project is to design such a controller for a planar octocopter, and compare it to previously developed control methods.

Watch: Wind tunnel test of Model Predictive Control.

Related: Enabling Unmanned Aerial Vehicles (Drones) to use Tools in Complex Dynamic Environments

Human Drone Physical Interaction

BE(Hons) Research Project, 2022

Iris Liu & Suvarna Swaraj. Supervisors: Karl Stol & Salim Al-zubaidi

Physical human drone interaction (PHDI) with underactuated drones has been widely explored due to its diverse applications from providing guidance to the visually impaired to virtual reality gaming. An opportunity exists in exploiting the decoupled translational and rotational dynamics of over-actuated drones for PHDI. 

This research aims to improve knowledge about an over-actuated drone’s estimation of and response to contact forces during an interaction through tuning parameters of an admittance control architecture.

Drone with Tilting-Rotor Configuration

BE(Hons) Research Project, 2022

Joshua Taylor & Matthew Edwards. Supervisors: Karl Stol & Salim Al-zubaidi

The ability to change direction quickly, referred to as agility, is crucial in a number of modern-day drone applications involving interaction and dynamic environments. While research exists on optimising the agility of the more commonly used fixed-tilt drone, improving agility by using variable-tilt drone designs remains unexplored.

This project involves building and testing a variable-tilt drone such that comparisons can be made to the performance of a fixed-tilt drone, in terms of its horizontal agility.

Related: Enabling Unmanned Aerial Vehicles (Drones) to use Tools in Complex Dynamic Environments

Measuring the Wind from a Drone

BE(Hons) Research Project, 2022

Ivan Rakich & Lynn May. Supervisor: Nicholas Kay

Numerical weather prediction models suffer from a lack of reliable coverage in remote and inaccessible areas. Employing a UAV to gather weather data within these regions could prove to be a low cost solution. However, a UAV is not a fixed platform, and moves in response to the wind which it is trying to measure. Furthermore, downdraft from the rotors adds an extra wind component to the measurements which is not reflective of the environment.

Consequently, this project attempts to measure the local wind vector by mounting an external flow sensor to a UAV. Using the drone’s inertial measurement unit and motion capture feedback, this project aims to produce a data correction methodology to replicate the true flow behaviour.

Watch: Wind measurement from a drone.