Modelling and Fast Terminal Sliding Mode Control for Mirror-based Pointing Systems

In this paper, we present a new discrete-time Fast Terminal Sliding Mode (FTSM) controller for mirror-based pointing systems. We first derive the decoupled model of those systems and then estimate the parameters using a nonlinear least-square identification method. Based on the derived model, we design a FTSM sliding manifold in the continuous domain. We then exploit the Euler discretization on the designed FTSM sliding surfaces to synthesize a discrete-time controller. Furthermore, we improve the transient dynamics of the sliding surface by adding a linear term. Finally, we prove the stability of the proposed controller based on the Sarpturk reaching condition. Extensive simulations, followed by comparisons with the Terminal Sliding Mode (TSM) and Model Predictive Control (MPC) have been carried out to evaluate the effectiveness of the proposed approach. A comparative study with data obtained from a real-time experiment was also conducted. The results indicate the advantage of the proposed method over the other techniques.Comment: In Proceedings of the 15th International Conference on Control, Automation, Robotics and Vision (ICARCV 2018

On data-driven modelling and terminal sliding mode control of dynamic systems with applications

University of Technology Sydney. Faculty of Engineering and Information Technology.This thesis addresses critical issues in system modelling and control with some applications to robotics and automation. The main content is divided into three parts, namely data-driven identification, fast terminal sliding mode control alongside underactuated crane control, and robotic pointing system for thermoelastic stress analysis (TSA). The first part is devoted to system modelling. A dynamic model can be identified from data collected (input and output data from the plant). However, the data obtained is often affected by noise. Hence, such algorithms for modelling the plant should be robust enough to accurately predict the dynamic behaviour of the system in the presence of noisy data. Taking this into account, this thesis focuses on subspace-based identification methods, and proposes an effective algorithm based on the Least-Square Support Vector Regression (LS-SVR). In the proposed algorithm, the system identification is formulated as a regression problem to be solved by applying multi-output LS-SVR. The second part of the thesis deals with the control of underactuated systems which are subjected to uncertainties including nonlinearities, parameter variations, and external disturbances. Among many control methodologies, Sliding Mode Control (SMC) is known for its strong robustness. Conventional SMC usually consists of linear sliding surfaces, which can only guarantee the asymptotic stability of the system, and hence, takes infinite time to reach the equilibrium. Requirements of finite-time stability can be fulfilled by adding the sliding function with a fractional nonlinear term to achieve the Terminal Sliding Mode, and using another attractor can lead to a faster response, called the Fast Terminal Sliding Mode (FTSM). FTSM is theoretically promising but it has limited application in real-time systems. This thesis is devoted to bridging this practical gap by developing a FTSM controller for underactuated mechanical systems. The third part of this thesis presents the applications of the proposed LS-SVR based identification algorithm and FTSM control scheme. Here, theoretical developments are implemented on a laboratorial gantry crane and an optical pointing system, respectively. Performance of both LS-SVR identification and FTSM control is verified through extensive simulation and experimental results. Notably, the work for this thesis has been applied to the RobotEye, an industrial pointing system of Ocular Robotics Pty. Ltd., which consists of a mirror integrated with other sensors such as laser sensors and vision cameras for robotic navigation or structural health monitoring with TSA

Line-of-sight-stabilization and tracking control for inertial platforms

Nowadays, line of sight stabilization and tracking using inertially stabilized platforms (ISPs) are still challenging engineering problems. With a growing demand for high-precision applications, more involved control techniques are necessary to achieve better performance. In this work, kinematic and dynamic models for a three degrees-of-freedom ISP are presented. These models are based in the vehicle-manipulator system (VMS) framework for modeling of robot manipulators operating in a mobile base (vehicles). The dynamic model follows the Euler-Lagrange formulation and is implemented by numeric simulations using the iterative Newton-Euler method. Two distinct control strategies for both stabilization and tracking are proposed: (i) computed torque control and (ii) sliding mode control using the recent SuperTwisting Algorithm (STA) combined with a High-Order Sliding Mode Observer (HOSMO). Simulations using data from a simulated vessel allow us to compare the performance of the computed torque controllers with respect to the commonly used P-PI controller. Besides, the results obtained for the sliding mode controllers indicate that the Super-Twisting algorithm offers ideal robustness to the vehicle motion disturbances and also to parametric uncertainties, resulting in a stabilization precision of approximately 0,8 mrad.Hoje em dia, a estabilização e o rastreamento da linha de visada utilizando plataformas inerciais continuam a constituir desafiadores problemas de engenharia. Com a crescente demanda por aplicações de alta precisão, técnicas de controle complexas são necessárias para atingir melhor desempenho. Neste trabalho, modelos cinemáticos e dinâmicos para uma plataforma mecânica de estabilização inercial são apresentados. Tais modelos se baseiam no formalismo para sistemas veículo-manipulator para a modelagem de manipuladores robóticos operando em uma base móvel (veículo). O modelo dinâmico apresentado segue a formulação analítica de Euler-Lagrange e é implementado em simulações numéricas através do método iterativo de Newton-Euler. Duas estratégias de controle distintas para estabilização e rastreamento são propostas: (i) controle por torque-computado e (ii) controle por modos deslizantes utilizando o recente algoritmo Super-Twisting combinado com um observador baseado em modos deslizantes de alta ordem. Simulações utilizando dados de movimentação de um navio simulado permitem comparar o desempenho dos controladores por torque computado em relação a um tipo comum de controlador linear utilizado na literatura: o P-PI. Além disso, os resultados obtidos para o controle por modos deslizantes permitem concluir que o algoritmo Super-Twisting apresenta rejeição ideal a perturbações provenientes do movimento do veículo e também a incertezas paramétricas, resultando em precisão de estabilização de aproximadamente 0,8 mrad

Virtual Dashboard for Tanker Truck

Society has been very concern about the new technologies that are increasing like mushroom lately. In addition, the replacement of hardware by software has been one of the major developments in the electronics industry for many years. However, it has basically been too small to be noticed by the end user. In this new age where everything is computerized, human become more curious to learn as well as make use of new application of the virtual dashboard as it grant a significant impacts on vehicle's users. Therefore, this report present information base on the research involves in Virtual Dashboard, which is purposely design for monitoring the performance of the truck. This report features the introduction that explains about background of study, problem statement, the significant of the project, objectives and the scope of study of the project research. There is also some part of studies for supporting information or reference to support the project research. Process of identification is in short talked about in order to entire the research and describe tools of hardware and software apply to design the product. The end-result of the research is the static virtual dashboard software prototype that caters the basic needs of virtual truck. In shorts, the 2D virtual dashboard is a replacing of the collector of mechanical instruments by software-configurable display. It enabled truck driver to maintain the truck's performance while driving. Hence, the interfaces need to be simple and intuitive to use in addition to provide interaction with the users, in order to increase operation efficiency. The virtual dashboard also provides a clear visualisation from the other part of the truck, in recognizable graphics and graphs. A message window indicates the gauges' performance as well as displaying warnings when the state values approach presets limits. With this, private, secure, fast digital connection from oil tanker will be directed to the knowledge of the user

Satellite technology : reinforcement of computer data transmission technology : implications for the maritime world communications, data transfer and maritime education

This dissertation is a study of the impact of data transmission via satellite on the maritime world of communication, data transfer and education. The aim of the study is to understand the technological reinforcement of the maritime industry and the changes taking place in it. With the avalanche of changes that are taking place in the field of information technology, they can be used to facilitate the shipping industry. This dissertation assists in understanding some of the technological evolution of satellite technology and data communication and in the needs of the maritime industry as well. This dissertation describes satellite technology and data communication and analyses the data communication software (protocols), compression software, and other application software combinations with maritime communication system provided to improve ship operation and management for safety. The conclusion and recommendations chapter examines the implications of the technology changes on developing countries, the need to be harmonised in training and education for the maritime industry, maritime communication systems and the equipment, policy of shipping companies and communication costs

AAS/GSFC 13th International Symposium on Space Flight Dynamics

This conference proceedings preprint includes papers and abstracts presented at the 13th International Symposium on Space Flight Dynamics. Cosponsored by American Astronautical Society and the Guidance, Navigation and Control Center of the 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 dynamics; and mission design

Development of a scanning system for use in the Terahertz region of the Electromagnetic Spectrum

This thesis concerned the development of a scanner system for use in the Terahertz region of the Electromagnetic spectrum. The approach used by the prototype developed, utilises two tilting mirrors for the purposes of scanning a target under investigation. An object is scanned by tilting an incident beam of radiation to a point of interest on the target, on this basis an image can be formed on a point by point basis. The Thesis begins with an Introduction to THz radiation and its associated properties. The need for a Terahertz scanner and the potential applications in the biomedical, security and space research are outlined. The reader is then introduced to various approaches utilised by currently existing scanners and the approach used for the work carried out in this thesis outlined in detail. The techniques used for computationally modelling diffraction limited optical systems are discussed namely Fresnel Diffraction, Gaussian Beam Mode Analysis (GBMA) and Physical Optics. The effectiveness of these techniques are highlighted by using each method to model elementary optical systems. The techniques are then used to computationally model the optical system used for the prototype developed and results presented. The final section is concerned with the development of the prototype including background theory on components used, implementation of the components and verification of alignment procedure. The development of the computer controlled tilting mirror system and its integration with the prototype is also outlined. Finally the results of the operational scanning prototype are presented and discussed

Development of a scanning system for use in the Terahertz region of the Electromagnetic Spectrum

This thesis concerned the development of a scanner system for use in the Terahertz region of the Electromagnetic spectrum. The approach used by the prototype developed, utilises two tilting mirrors for the purposes of scanning a target under investigation. An object is scanned by tilting an incident beam of radiation to a point of interest on the target, on this basis an image can be formed on a point by point basis. The Thesis begins with an Introduction to THz radiation and its associated properties. The need for a Terahertz scanner and the potential applications in the biomedical, security and space research are outlined. The reader is then introduced to various approaches utilised by currently existing scanners and the approach used for the work carried out in this thesis outlined in detail. The techniques used for computationally modelling diffraction limited optical systems are discussed namely Fresnel Diffraction, Gaussian Beam Mode Analysis (GBMA) and Physical Optics. The effectiveness of these techniques are highlighted by using each method to model elementary optical systems. The techniques are then used to computationally model the optical system used for the prototype developed and results presented. The final section is concerned with the development of the prototype including background theory on components used, implementation of the components and verification of alignment procedure. The development of the computer controlled tilting mirror system and its integration with the prototype is also outlined. Finally the results of the operational scanning prototype are presented and discussed

Morphometric Study of Longitudinal Ridges in Long Runout Landslides on Mars, Earth, and the Moon

Long runout landslides are hypermobile landslides ubiquitous in our solar system. The exact mechanism(s) that have to be invoked in order to explain their high velocity and exceptional travel distances over nearly horizontal surfaces has yet to be successfully determined. In this thesis I focused on the distinctive longitudinal ridges that mark the surface of long runout landslide deposits in the attempt to link these morphological features and their related internal structures to the mechanisms involved during the emplacement of such catastrophic events. I conducted a morphometric analysis of longitudinal ridges of three case studies: the Coprates Labes landslide in Valles Marineris on Mars; the El Magnifico landslide in Chile – on Earth; the Tsiolkovskiy crater landslide – on the Moon. For the first time in natural landslides, I found that the wavelength of the longitudinal ridges is consistently 2 to 3 times the thickness of the landslide deposit, in agreement with experimental work on rapid granular flows. The recurrence of the scaling relationship suggests a scale- and environment-independent mechanism. Therefore, I concluded that the existence of longitudinal ridges in long runout landslides cannot be used to infer the presence of specific lithologies forming the basal surface; nor environmental and climatic conditions at the time of landslide emplacement. Based on the agreement between the results obtained from my morphometric analysis and the laboratory experiments on rapid granular flows, I proposed that longitudinal ridges in long runout landslides are imparted by high-speed granular flow convection mechanisms. In order to ground truth such hypothesis, I conducted field work at the terrestrial El Magnifico landslide and studied the internal structures of the deposit and their relationship with the longitudinal ridges. I concluded that evidence cannot rule out a convection-style mechanism observed in laboratory experiments of granular flows but is also not equivocal in its support. I advanced an alternative hypothesis that longitudinal ridges may have formed by a mechanism that involves pattern-forming vibrations. Such proposed mechanism supports the existence of heterogeneous stress distribution and stress fluctuation within long runout landslide deposits, which are considered the hallmark of acoustic fluidization. I suggested the use of the scaling relationship between the wavelength of longitudinal ridges and the thickness of the deposit as a tool to infer the thickness of landslide deposits where its calculation is not otherwise possible using typical methods in geomorphology. I applied this novel idea to the Light Mantle landslide, Taurus-Littrow valley, at the Apollo 17 landing site: by calculating the representative wavelength of the longitudinal ridges I derived the thickness of its deposit, as it could not be derived through interpolation. I discussed the finding of my work within the context of the literature on frictional weakening in fault mechanics, on the similarity of weakening of shear zones in landslide and earthquake mechanics, and on the geomorphology of long runout landslide deposits. Following this, I defined a new framework under which the understanding of the formation mechanism of long runout landslides should be approached. Finally, I identified four possible directions for future work: extending the morphometric analysis of longitudinal ridges in martian double layer ejecta; investigating the importance of the roughness of the substrate in the formation of longitudinal ridges; performing friction experiments to study weakening mechanisms in lunar rock analogues; using martian long runout landslide deposits as stratigraphic markers in order to constrain the timing of geological processes

Haptic ankle platform for interactive walking in virtual reality.

This paper presents an impedance type ankle haptic interface for providing users with an immersive navigation experience in virtual reality (VR). The ankle platform actuated by an electric motor with feedback control enables the use of foot-tapping gestures to create a walking experience similar to a real one and to haptically render different types of walking terrains. Experimental studies demonstrated that the interface can be easily used to generate virtual walking and it is capable to render terrains such as hard and soft surfaces, and multi-layer complex dynamic terrains. The designed system is a seated-type VR locomotion interface, therefore allowing its user to maintain a stable seated posture to comfortably navigate a virtual scene