Robust nonlinear trajectory tracking and control of quadrotor UAV

Unmanned Aerial Vehicles(UAVs) provide a versatile platform for the automation of a wide variety of tasks such as powerline inspection, border interdiction, search and rescue e.t.c. The success of these UAV platforms relies heavily on the development of control algorithms that can cope with the harsh and uncertain environments in which the UAVs will operate in. This dissertation focuses on the development of robust trajectory tracking control algorithms for a quadrotor UAV platform. Robustness in this context refers to the ability of the controller to guarantee system performance in the presence of uncertainties such as unknown system parameters or some other unmodeled e ects. By exploiting the strict feedback form of the quadrotor dynamics a backstepping based control strategy for the system which comprises of two sub-controllers namely a translational controller and an attitude controller is developed. For the translational controller of the UAV a novel robust bounded controller is developed. This novel controller is developed by combining A.R Teel's nonlinear saturated controller with sliding mode techniques to achieve bounded error tracking in the presence of disturbances while at the same time ensuring bounded control which captures the limited nature of the UAV's thrust actuators. Additionally conditions on the controller parameters are identi ed which ensure that the UAV does not overturn during flight. The controller for the vehicle attitude is based on a modified backstepping method. Conventional backstepping control is formulated under the implicit assumption of a perfectly known system, thus in instances where uncertainty exists the performance of conventional backstepping deteriorates. To improve on the robustness of conventional backstepping control, methods of combining it with adaptive and/or sliding mode techniques are considered. Adaptive backstepping control is robust against parametric uncertainty however its performance deteriorates in the presence of disturbances. An adaptive backstepping controller with nonlinear damping is proposed as a solution to this problem, Lyapunov based analysis shows that this controller achieves bounded error tracking in the presence of parametric and non-parametric uncertainty. A second modi cation of the backstepping method that is considered involves combining sliding mode control with conventional backstepping control. Sliding backstepping control is a powerful control method in that it is able to achieve asymptotic tracking in the presence of uncertainty. However this is only achieved if the upper bounds of the uncertainty are known a priori, this requirement is very di cult to meet in practice. Thus an adaptive sliding backstepping controller is proposed which removes the requirement of a priori knowledge of the upper bounds. In conclusion the key features of this work are a novel robust bounded translational controller, an adaptive backstepping attitude controller with nonlinear damping and an adaptive sliding backstepping attitude controller with guaranteed asymptotic tracking. Thus a comprehensive robust trajectory tracking controller for a quadrotor UAV is developed

Sliding Mode Control

The main objective of this monograph is to present a broad range of well worked out, recent application studies as well as theoretical contributions in the field of sliding mode control system analysis and design. The contributions presented here include new theoretical developments as well as successful applications of variable structure controllers primarily in the field of power electronics, electric drives and motion steering systems. They enrich the current state of the art, and motivate and encourage new ideas and solutions in the sliding mode control area

MODELING AND INTELLIGENT CONTROL OF A DRONE

This thesis tackles the modeling, design, and control of a Quadrotor unmanned aerial vehicle, with a focus on intelligent control and smart applications such as obstacle avoidance, robust trajectory tracking, visual soft landing, and disturbance compensation. It details the mathematical modeling opted for the simulation and the control. Furthermore, It describes the classic control methodology for both linear and nonlinear control techniques with interpreted simulations; The methodology is subsequently applied to develop an open-source autonomous quadrotor miniature model. In addition, advanced control theory has been applied using Adaptive Linear Quadratic Gaussian, Model predictive control, and intelligent Radial basis functions neural network for the robust tracking of generated trajectory for either obstacle avoidance or bio-inspired soft landing on a specially designed landing pad. The thesis depicts as well the adaptive optimal observation by an enhanced Kalman filter combined with Madgwick sensor’s data fuse. Control laws were mainly either mathematically derived or adaptively generated based on stability analysis using Lyapunov theory, The simulation incorporated several analytical comparisons to prove efficiency and compare the performance

The numerical simulation of plate-type windborne debris flight

Wind borne debris is one of the principal causes of building envelope failure during severe storms. It is often of interest in windstorm risk modelling to estimate the potential flight trajectories and impact energy of a piece of debris. This thesis presents research work aimed at the development and validation of a numerical model for the simulation of plate-type windborne debris. While a number of quasi-steady analytical models are available at present, these models are unable to account for the fluid-plate interaction in highly unstable flows. The analytical models are also limited to simple launch flow conditions and require extensive a-priori knowledge of the debris aerodynamic characteristics. In addition, the use of Euler angle parametrisations of orientation in the analytical models results in mathematical singularities when considering 3D six degree-of-freedom motion. To address these limitations, a 3D Computational Fluid Dynamics (CFD) model is sequentially coupled with a quaternion based singularity-free six degree of freedom Rigid Body Dynamics (RBD) model in order to successfully simulate the flight of plate-type windborne debris. The CFD-RBD model is applied to the numerical investigation of the flow around static, forced rotating, autorotating and free-flying plates as well as the treatment of complex launch conditions. Key insights into the phenomena of plate autorotation are highlighted including the genesis of the aerodynamic damping and acceleration torques that make autorotation possible. The CFD-RBD model is then validated against measurements of rotational speed and surface pressure obtained from recent autorotation experiments. Subsequently a general 3D spinning mode of autorotation is demonstrated and the CFD-RBD model is extended to include plate translation in order to simulate windborne debris flight. Using the CFD-RBD flight model, a parametric study of windborne debris flight is carried out and four distinct flight modes have been identified and are discussed. The flight results are contrasted against available free-flight experiments as well as predictions from existing quasi-steady analytical models and an improved quasi-steady force model based on forced rotation results is proposed. The resulting CFD-RBD model presents the most complete numerical approach to the simulation of plate-type windborne debris, directly simulating debris aerodynamics, and incorporates complex launch flow fields in the initial conditions

A novel dual-spin actuation mechanism for small calibre, spin stabilised, guided projectiles

© Cranfield University 2022. All rights reserved. No part of this publication may be reproduced without the written permission of the author and copyright holderSmall calibre projectiles are spin-stabilised to increase ballistic stability, often at high frequencies. Due to hardware limitations, conventional actuators and meth ods are unable to provide satisfactory control at such high frequencies. With the reduced volume for control hardware and increased financial cost, incorporating traditional guid ance methods into small-calibre projectiles is inherently difficult. This work presents a novel method of projectile control which addresses these issues and conducts a systems level analysis of the underlying actuation mechanism. The design is shown to be a viable alternative to traditional control methods, Firstly, a 7 Degree-of-Freedom (DoF) dynamic model is created for dual-spin pro jectiles, including aerodynamic coefficients. The stability of dual-spin projectiles, gov erned by the gyroscopic and dynamic stability factors is given, discussed and unified across available literature. The model is implemented in a Matlab/Simulink simulation environ ment, which is in turn validated against a range of academic literature and experimental test data. The novel design and fundamental operating principle are presented. The actuation mechanism (AM) is then mathematically formulated from both a velocity change (∆V ) and a lateral acceleration (a˜) perspective. A set of axioms are declared and verified using the 7-DoF model, showing that the inherently discrete system behaviour can be controlled continuously via these control variables, ∆V or a˜. Control state switching is simplified to be instantaneous, then expanded to be generically characterised by an arbitrarily complex mathematical function. A detailed investigation, parametric analysis and sensitivity study is undertaken to understand the system behaviour. A Monte Carlo procedure is described, which is used to compare the correction cap abilities of different guidance laws (GLs). A bespoke Zero-Effort-Miss (ZEM) based GLis synthesised from the mathematical formulation of the AM, with innately more know ledge of the system behaviour, which allows superior error correction. This bespoke GL is discussed in detail, a parametric study is undertaken, and both the GL parameters and PID controller gains are optimised using a genetic algorithm. Artificial Intelligence (AI) Reinforcement learning methods are used to emulate a GL, as well as controlling the AM and operating as a GL, simultaneously. The novel GLs are compared against a traditional proportional navigation GL in a nominal system and all GLs were able to control the AMs, reducing the miss distance to a satisfactory margin. The ZEM-based GL provided superior correction to the AI GL, which in turn provided superior correction over proportional navigation. Example CAD models are shown, and the stability analysis is conducted on the geometry. The CAD model is then used in CFD simulations to determine aerodynamic coefficients for use in the 7-DoF dynamic model. The novel control method was able to reduce the 95% dispersion diameter of a traditional ballistic 7.62mm projectile from 70mm to 33mm. Statistical data analysis showed there was no significant correlation or bias present in either the nominal or 7-DoF dispersion patterns. This project is co-sponsored by BAE Systems and ESPRC (ref. 1700064). The con tents of this thesis are covered by patent applications GB2011850.1, GB 2106035.5 and EP 20275128.5. Two papers are currently published (DOI: 10.1016/j.dt.2019.06.003, the second DOI is pending) and one is undergoing peer review..PH

1999 Flight Mechanics Symposium

This conference publication includes papers and abstracts presented at the Flight Mechanics Symposium held on May 18-20, 1999. Sponsored by the Guidance, Navigation and Control Center of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination, and control; attitude sensor calibration; attitude determination error analysis; attitude dynamics; and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers

The numerical simulation of plate-type windborne debris flight

Wind borne debris is one of the principal causes of building envelope failure during severe storms. It is often of interest in windstorm risk modelling to estimate the potential flight trajectories and impact energy of a piece of debris. This thesis presents research work aimed at the development and validation of a numerical model for the simulation of plate-type windborne debris. While a number of quasi-steady analytical models are available at present, these models are unable to account for the fluid-plate interaction in highly unstable flows. The analytical models are also limited to simple launch flow conditions and require extensive a-priori knowledge of the debris aerodynamic characteristics. In addition, the use of Euler angle parametrisations of orientation in the analytical models results in mathematical singularities when considering 3D six degree-of-freedom motion. To address these limitations, a 3D Computational Fluid Dynamics (CFD) model is sequentially coupled with a quaternion based singularity-free six degree of freedom Rigid Body Dynamics (RBD) model in order to successfully simulate the flight of plate-type windborne debris. The CFD-RBD model is applied to the numerical investigation of the flow around static, forced rotating, autorotating and free-flying plates as well as the treatment of complex launch conditions. Key insights into the phenomena of plate autorotation are highlighted including the genesis of the aerodynamic damping and acceleration torques that make autorotation possible. The CFD-RBD model is then validated against measurements of rotational speed and surface pressure obtained from recent autorotation experiments. Subsequently a general 3D spinning mode of autorotation is demonstrated and the CFD-RBD model is extended to include plate translation in order to simulate windborne debris flight. Using the CFD-RBD flight model, a parametric study of windborne debris flight is carried out and four distinct flight modes have been identified and are discussed. The flight results are contrasted against available free-flight experiments as well as predictions from existing quasi-steady analytical models and an improved quasi-steady force model based on forced rotation results is proposed. The resulting CFD-RBD model presents the most complete numerical approach to the simulation of plate-type windborne debris, directly simulating debris aerodynamics, and incorporates complex launch flow fields in the initial conditions

Design and performance simulation of a hybrid sounding rocket.

Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2012.Sounding rockets find applications in multiple fields of scientific research including meteorology, astronomy and microgravity. Indigenous sounding rocket technologies are absent on the African continent despite a potential market in the local aerospace industries. The UKZN Phoenix Sounding Rocket Programme was initiated to fill this void by developing inexpensive medium altitude sounding rocket modeling, design and manufacturing capacities. This dissertation describes the development of the Hybrid Rocket Performance Simulator (HYROPS) software tool and its application towards the structural design of the reusable, 10 km apogee capable Phoenix-1A hybrid sounding rocket, as part of the UKZN Phoenix programme. HYROPS is an integrated 6–Degree of Freedom (6-DOF) flight performance predictor for atmospheric and near-Earth spaceflight, geared towards single-staged and multi-staged hybrid sounding rockets. HYROPS is based on a generic kinematics and Newtonian dynamics core. Integrated with these are numerical methods for solving differential equations, Monte Carlo uncertainty modeling, genetic-algorithm driven design optimization, analytical vehicle structural modeling, a spherical, rotating geodetic model and a standard atmospheric model, forming a software framework for sounding rocket optimization and flight performance prediction. This framework was implemented within a graphical user interface, aiming for rapid input of model parameters, intuitive results visualization and efficient data handling. The HYROPS software was validated using flight data from various existing sounding rocket configurations and found satisfactory over a range of input conditions. An iterative process was employed in the aerostructural design of the 1 kg payload capable Phoenix-1A vehicle and CFD and FEA numerical techniques were used to verify its aerodynamic and thermo-structural performance. The design and integration of the Phoenix-1A‟s hybrid power-plant and onboard electromechanical systems for recovery parachute deployment and motor oxidizer flow control are also discussed. It was noted that use of HYROPS in the design loop led to improved materials selection and vehicle structural design processes. It was also found that a combination of suitable mathematical techniques, design know-how, human-interaction and numerical computational power are effective in overcoming the many coupled technical challenges present in the engineering of hybrid sounding rockets