Quantitative Analysis of Non-Linear Probabilistic State Estimation Filters for Deployment on Dynamic Unmanned Systems

The work conducted in this thesis is a part of an EU Horizon 2020 research initiative project known as DigiArt. This part of the DigiArt project presents and explores the design, formulation and implementation of probabilistically orientated state estimation algorithms with focus towards unmanned system positioning and three-dimensional (3D) mapping. State estimation algorithms are considered an influential aspect of any dynamic system with autonomous capabilities. Possessing the ability to predictively estimate future conditions enables effective decision making and anticipating any possible changes in the environment. Initial experimental procedures utilised a wireless ultra-wide band (UWB) based communication network. This system functioned through statically situated beacon nodes used to localise a dynamically operating node. The simultaneous deployment of this UWB network, an unmanned system and a Robotic Total Station (RTS) with active and remote tracking features enabled the characterisation of the range measurement errors associated with the UWB network. These range error metrics were then integrated into an Range based Extended Kalman Filter (R-EKF) state estimation algorithm with active outlier identification to outperform the native approach used by the UWB system for two-dimensional (2D) pose estimation.The study was then expanded to focus on state estimation in 3D, where a Six Degreeof-Freedom EKF (6DOF-EKF) was designed using Light Detection and Ranging (LiDAR) as its primary observation source. A two step method was proposed which extracted information between consecutive LiDAR scans. Firstly, motion estimation concerning Cartesian states x, y and the unmanned system’s heading (ψ) was achieved through a 2D feature matching process. Secondly, the extraction and alignment of ground planes from the LiDAR scan enabled motion extraction for Cartesian position z and attitude angles roll (θ) and pitch (φ). Results showed that the ground plane alignment failed when two scans were at 10.5◦ offset. Therefore, to overcome this limitation an Error State Kalman Filter (ES-KF) was formulated and deployed as a sub-system within the 6DOF-EKF. This enabled the successful tracking of roll, pitch and the calculation of z. The 6DOF-EKF was seen to outperform the R-EKF and the native UWB approach, as it was much more stable, produced less noise in its position estimations and provided 3D pose estimation

2020 NASA Technology Taxonomy

This document is an update (new photos used) of the PDF version of the 2020 NASA Technology Taxonomy that will be available to download on the OCT Public Website. The updated 2020 NASA Technology Taxonomy, or "technology dictionary", uses a technology discipline based approach that realigns like-technologies independent of their application within the NASA mission portfolio. This tool is meant to serve as a common technology discipline-based communication tool across the agency and with its partners in other government agencies, academia, industry, and across the world

Dynamics Of Reconfigurable Multibody Space Systems Connected By Magnetic Flux Pinning

Many future space systems, from solar power collection satellites to sparseaperture telescopes, will involve large-scale space structures which must be launched in a modular fashion. Currently, assembling modular structures in orbit is a challenging problem in multi-vehicle control or human-vehicle interaction. Some novel approaches to assembling modular space structures or formation-flying space systems involve augmenting the system dynamics with non-contacting force fields such as electromagnetic interactions. However, familiar divergenceless forces are subject to Earnshaw's Theorem and require active control in 6 DOF for stability. This study proposes an approach to modular spacecraft assembly based on the passively stable physics of magnetic flux pinning, an interaction between superconductors and magnetic fields which is not limited by Earnshaw's Theorem. Spacecraft modules linked by flux pinning passively fall into stable, many-degree-of-freedom basins of attraction in which flux pinning holds the modules together with stiffness and damping but no mechanical contact. This dissertation reports several system identification experiments that characterize the physical properties of flux pinning for spacecraft applications and identify avenues for design of flux-pinning space hardware. Once assembled in orbit, altering a spacecraft to effect repairs or adapt to new missions presents significant control challenges as well. Flux-pinning technology also offers exciting possibilities for new spacecraft-reconfiguration techniques, in which a spacecraft changes structure and function at the system level. Flux-pinned modular spacecraft can reconfigure in such a way that the passive physics of flux pinning and the space environment govern the low-level dynamics of a reconfiguration maneuver, instead of full-state feedback control. These reconfiguration maneuvers take the form of sequences of passively stable evolutions to equilibrium states, with joint kinematics between modules preventing collisions. This dissertation develops a theory for multibody spacecraft reconfiguration controllers that take a high-level, hybrid-systems approach in which a pre-computed graph structure stores all the reachable configurations that meet certain design-specified criteria. Edges of the graph carry mission-related weights so that a space system can optimize power consumption, robustness measures, or other performance metrics during a maneuver. These technologies and control strategies may provide opportunities for versatile space systems that can accomplish a wide variety of future missions

Minimising vibration in a flexible golf club during robotic simulations of a golf swing

Robots are widely used as substitutes for humans in situations involving repetitive tasks where a precise and repeatable motion is required. Sports technology is an area which has seen an increase in the implementation of robots which simulate specific human motions required for a sport. One purpose is to test sports equipment, where the requirement is for a motion to be performed with consistent variables. One issue which has arisen frequently in the robot simulation of humans is the inherent presence of vibration excited in a flexible object being manipulated by a robot, and this issue is not unfounded in the situation presented in this research, of a golf robot manipulating a flexible golf club during the simulation of a golf swing. It had been found that during robotic simulations of golf swings performed with the Miyamae Robo V at the Sports Technology Institute at Loughborough University, swing variables such as shaft deformation and clubhead orientation were dissimilar to those measured for human golf swings. Vibrations present in the golf club were identified as the key cause of the disparity between human and robot swing variables. This research sought to address this issue and find a method which could be applied to reduce clubhead vibrations present in robot simulations of a golf swing to improve their similarity to human swings. This would facilitate the use of the golf robot for equipment testing and club fitting. Golf swing variables were studied and measured for 14 human subjects with the aim being to understand the motion that the robot is required to simulate. A vibration damping gripper was then fitted to the robot to test the effect that changing the interface between the robot-excited vibrations and the club would have, this was achieved with a selection of silicone sleeves with differing material properties which could be attached to the club. Preliminary results showed a noticeable reduction in clubhead vibrations and this solution was investigated further. Mathematically modelling the robot was seen as the most suitable method for this as it meant the robot remained functional and allowed a number of solutions to be tested. Several iterations of a mathematical model were developed with the final model being structurally similar to the robot with the addition of a compliant grip and wrist. The method by which the robot is driven was also recognised as having a large effect on the level of vibration excited in the clubhead and the methodology behind generating smooth robot swing profiles is presented. The mathematical model was used to perform 6 swings and the resulting shaft deformation and clubhead vibration were compared with data from human swings. It was found that the model was capable of producing swing variables comparable to human swings, however in the downswing portion of the swing the magnitude of these variables were larger for the simulations. Simulations were made which sought to demonstrate the difference between the model replicating the rigid robot and a compliant system. Reductions in vibration were achieved in all swings, including those driven with robot feedback data which contains oscillations excited by the method with which the robot is driven

Robot Manipulators

Robot manipulators are developing more in the direction of industrial robots than of human workers. Recently, the applications of robot manipulators are spreading their focus, for example Da Vinci as a medical robot, ASIMO as a humanoid robot and so on. There are many research topics within the field of robot manipulators, e.g. motion planning, cooperation with a human, and fusion with external sensors like vision, haptic and force, etc. Moreover, these include both technical problems in the industry and theoretical problems in the academic fields. This book is a collection of papers presenting the latest research issues from around the world

Automated Rendezvous and Docking Sensor Testing at the Flight Robotics Laboratory

The Exploration Systems Architecture defines missions that require rendezvous, proximity operations, and docking (RPOD) of two spacecraft both in Low Earth Orbit (LEO) and in Low Lunar Orbit (LLO). Uncrewed spacecraft must perform automated and/or autonomous rendezvous, proximity operations and docking operations (commonly known as Automated Rendezvous and Docking, (AR&D).) The crewed versions of the spacecraft may also perform AR&D, possibly with a different level of automation and/or autonomy, and must also provide the crew with relative navigation information for manual piloting. The capabilities of the RPOD sensors are critical to the success of the Exploration Program. NASA has the responsibility to determine whether the Crew Exploration Vehicle (CEV) contractor-proposed relative navigation sensor suite will meet the CEV requirements. The relatively low technology readiness of relative navigation sensors for AR&D has been carried as one of the CEV Projects top risks. The AR&D Sensor Technology Project seeks to reduce this risk by increasing technology maturation of selected relative navigation sensor technologies through testing and simulation, and to allow the CEV Project to assess the relative navigation sensors

Technologies for digital twin applications in construction

The construction industry is facing enormous pressure to adopt digital solutions to solve the industry's inherent problems. The digital twin has emerged as a solution that can update a BIM model with real-time data to achieve cyber-physical integration, enabling real-time monitoring of assets and activities and improving decision-making. The application of digital twins in the construction industry is still in its nascent stages but has been steadily growing over the past few years. A wide variety of emerging technologies are being used in the development of digital twins in diverse applications in construction but it is not immediately clear from the literature which ones are key to the successful development of digital twins, necessitating a systematic literature review with a focus on technologies. This paper aims to identify the key technologies used in the development of digital twins in construction in the existing literature, the research gaps and the potential areas for future research. This is achieved by conducting a systematic review of studies with demonstrative case studies and experimental setups in construction. Based on the observed research gaps, prominent future research directions are suggested, focusing on technologies in data transmission, interoperability and data integration and data processing and visualisation

Multi-scale metrology for automated non-destructive testing systems

This thesis was previously held under moratorium from 5/05/2020 to 5/05/2022The use of lightweight composite structures in the aerospace industry is now commonplace. Unlike conventional materials, these parts can be moulded into complex aerodynamic shapes, which are diffcult to inspect rapidly using conventional Non-Destructive Testing (NDT) techniques. Industrial robots provide a means of automating the inspection process due to their high dexterity and improved path planning methods. This thesis concerns using industrial robots as a method for assessing the quality of components with complex geometries. The focus of the investigations in this thesis is on improving the overall system performance through the use of concepts from the field of metrology, specifically calibration and traceability. The use of computer vision is investigated as a way to increase automation levels by identifying a component's type and approximate position through comparison with CAD models. The challenges identified through this research include developing novel calibration techniques for optimising sensor integration, verifying system performance using laser trackers, and improving automation levels through optical sensing. The developed calibration techniques are evaluated experimentally using standard reference samples. A 70% increase in absolute accuracy was achieved in comparison to manual calibration techniques. Inspections were improved as verified by a 30% improvement in ultrasonic signal response. A new approach to automatically identify and estimate the pose of a component was developed specifically for automated NDT applications. The method uses 2D and 3D camera measurements along with CAD models to extract and match shape information. It was found that optical large volume measurements could provide suffciently high accuracy measurements to allow ultrasonic alignment methods to work, establishing a multi-scale metrology approach to increasing automation levels. A classification framework based on shape outlines extracted from images was shown to provide over 88% accuracy on a limited number of samples.The use of lightweight composite structures in the aerospace industry is now commonplace. Unlike conventional materials, these parts can be moulded into complex aerodynamic shapes, which are diffcult to inspect rapidly using conventional Non-Destructive Testing (NDT) techniques. Industrial robots provide a means of automating the inspection process due to their high dexterity and improved path planning methods. This thesis concerns using industrial robots as a method for assessing the quality of components with complex geometries. The focus of the investigations in this thesis is on improving the overall system performance through the use of concepts from the field of metrology, specifically calibration and traceability. The use of computer vision is investigated as a way to increase automation levels by identifying a component's type and approximate position through comparison with CAD models. The challenges identified through this research include developing novel calibration techniques for optimising sensor integration, verifying system performance using laser trackers, and improving automation levels through optical sensing. The developed calibration techniques are evaluated experimentally using standard reference samples. A 70% increase in absolute accuracy was achieved in comparison to manual calibration techniques. Inspections were improved as verified by a 30% improvement in ultrasonic signal response. A new approach to automatically identify and estimate the pose of a component was developed specifically for automated NDT applications. The method uses 2D and 3D camera measurements along with CAD models to extract and match shape information. It was found that optical large volume measurements could provide suffciently high accuracy measurements to allow ultrasonic alignment methods to work, establishing a multi-scale metrology approach to increasing automation levels. A classification framework based on shape outlines extracted from images was shown to provide over 88% accuracy on a limited number of samples