Industrial Robot Trajectory Stiffness Mapping for Hybrid Manufacturing Process

The application of using industrial robots in hybrid manufacturing is promising, but the heavy external load applied on robot system, including the weight of deposition extruder or the cutting force from machining process, affects the operation accuracy significantly. This paper proposed a new method for helping robot to find the best position and orientation to perform heavy duty tasks based on the current system stiffness. By analyzing the robot kinematic and stiffness matrix properties of robot, a new evaluation formulation has been established for mapping the trajectory¢‚¬„¢s stiffness within the robot¢‚¬„¢s working volumetric. The influence of different position and orientation for hybrid manufacturing working path in different scale has been discussed. Finally, a visualized evaluation map can be obtained to describe the stiffness difference of a robotic deposition working path at different positions and orientations. The method is important for improving the operation performance of robot system with current stiffness capability

Parallel Manipulators

In recent years, parallel kinematics mechanisms have attracted a lot of attention from the academic and industrial communities due to potential applications not only as robot manipulators but also as machine tools. Generally, the criteria used to compare the performance of traditional serial robots and parallel robots are the workspace, the ratio between the payload and the robot mass, accuracy, and dynamic behaviour. In addition to the reduced coupling effect between joints, parallel robots bring the benefits of much higher payload-robot mass ratios, superior accuracy and greater stiffness; qualities which lead to better dynamic performance. The main drawback with parallel robots is the relatively small workspace. A great deal of research on parallel robots has been carried out worldwide, and a large number of parallel mechanism systems have been built for various applications, such as remote handling, machine tools, medical robots, simulators, micro-robots, and humanoid robots. This book opens a window to exceptional research and development work on parallel mechanisms contributed by authors from around the world. Through this window the reader can get a good view of current parallel robot research and applications

Improved Industrial Robot Positional Accuracy for Machining with Bias Correction

Robotic machining has the potential to provide advantages as a substitute for conventional CNC machine tool operations. However, conventional industrial robots are restricted to low accuracy tasks due to their poor positional accuracy. This creates challenges in achieving the tolerances required for machining tasks. Data-based modelling of the positional error data is a potential solution which learns the positional errors in order to compensate and minimise them. There has been some success in improving industrial robot accuracy in research literature, by first calibrating the kinematic model and then using machine learning (ML)-based bias correction to learn the positional errors. However, the limitations of ML-based bias correction applied to the industrial robot positional accuracy problem have not been fully explored with the accuracies required to achieve tight machining tolerances. Mapping the positional errors with a greater resolution of training data, and reducing the burden on bias correction by calibrating the kinematic model with a higher level of calibration, are two examples which have the potential to improve accuracy. This thesis focusses on both training data resolution and bias reduction to maximise outcomes whilst informing trade-offs when using ML-based bias correction in this application. The key finding of this thesis is that substantial gains in accuracy can be achieved using ML-based bias correction and that the accuracy limit can be achieved with practicable amounts of data gathering and processing. Also that calibration prior to bias correction did not significantly improve overall accuracy for the cases investigated. This suggests that data may be better utilised in training the bias corrector rather than for calibration of the physical model. In conclusion, ML-based bias correction methods can provide a solution that provides substantial gains in positional accuracy for conventional industrial robots, bringing them to a level that may facilitate broader adoption in machining applications

Automatische Fehlerbehandlung in industriellen Montageszenarien auf Basis menschlicher Demonstrationen

Based on a scenario where humans and robots share their workspace, a system for automatically error handling during an automated industrial assembly is presented. If an error occurs, it is first detected and then classified. If it is a previously unknown error, the human closest to the robot will be asked to perform error handling by interacting with the robot. This interaction is recorded so that it can be reapplied if the same error occurs again. If the error is already known, an appropriate error handling is selected and applied without any further human interaction required. Thus, the interaction rate decreases over time and the system learns to handle more and more errors independently. In addition, it is presented how different recorded error handlings can be optimized according to given performance criteria. For this purpose, a suitable input device for performing the error handling is required first. In addition, the Hierarchical Decomposition (HD) is introduced as the abstract representation of an assembly operation. In this case, an assembly is subdivided into different states at multiple hierarchical levels. This is done by a domain export which also defines conditions for state transition. Thus, the HD allows assembly progress monitoring, error detection and classification as well as error prediction. A strategy presentation is introduced to store and reuse demonstrated error handling interactions. One particular feature of this representation is that a strategy is always related to the robot's end-effector pose at that point of time when an error occurs. Thus, a strategy describes the movements which have been performed for error handling. The strategy's invariance against rotation or translation allows significant reduction in the amount of strategies needed to be demonstrated by a human via interaction. Four selection criteria are introduced in order to decide if a strategy matches an error. Thereby, it is possible to make a selection based on one criterion or to perform a multi-criteria optimization using all available information. By introducing a strategy optimization approach, the overall system performance can be improved. In a subsequent experiment, it is shown that the presented error handling approach can be successfully applied.Ausgehend von einem Szenario, in dem sich Menschen und Roboter einen Arbeitsraum teilen, wird ein System zur automatischen Behandlung von Fehlerzuständen in automatisierten Montageprozessen vorgestellt. Tritt ein Fehler auf, so wird dieser erkannt und klassifiziert. Handelt es sich um einen bisher unbekannten Fehler, so wird der Mensch, welcher dem Roboter am nächsten ist gebeten, eine Fehlerbehandlung durch Interaktion mit dem Roboter durchzuführen. Diese Fehlerbehandlung wird aufgezeichnet, sodass sie bei einem erneuten Auftreten des gleichen Fehlers wieder angewendet werden kann. Ist der aufgetretene Fehler jedoch bereits bekannt, so wird eine dazu passende Fehlerbehandlung ausgewählt und ausgeführt, ohne dass es zu einer Interaktion kommt. Somit sinkt die Interaktionsrate über die Zeit betrachtet und das System lernt immer mehr Fehler eigenständig zu behandeln. Zusätzlich wird vorgestellt, wie verschiedene und aufgezeichnete Fehlerbehandlungen gemäß vorgegebenen Performancemaßen optimiert werden können. Zur Realisierung eines solchen Systems wird zunächst ein passendes Eingabegerät zur Durchführung der Fehlerbehandlung benötigt. Zusätzlich wird mit der Hierarchical Decomposition (HD) ein Ansatz zur abstrakten Beschreibung von Montagevorgängen vorgestellt. Des Weiteren wird eine Strategierepräsentation eingeführt, um demonstrierte Fehlerbehandlungen speichern und wiederverwenden zu können. Eine besondere Eigenschaft der vorgestellten Strategierepräsentation ist, dass eine Strategie immer auf die End-Effektor Pose des Roboters zu dem Zeitpunkt, an welchem der Fehler auftritt, bezogen ist. Somit beschreibt eine Strategie die Bewegungen, welche zur Fehlerbehandlung durchzuführen sind. Um Strategien auswählen zu können, werden vier Auswahlkriterien vorgestellt. Dabei ist es möglich, eine Auswahl nur auf Basis eines Kriteriums zu treffen oder alle zu berücksichtigen, in dem eine Multikriterienoptimierung durchgeführt wird. Durch die Einführung eines Verfahrens zur Optimierung von Strategien kann die Systemperformance bezüglich eines vorgegebenen Performancemaßes gesteigert werden. In einem anschließenden Experiment wird gezeigt, dass der vorgestellte Ansatz zur Fehlerbehandlung erfolgreich angewendet werden kann

Development of a Robotic Positioning and Tracking System for a Research Laboratory

Measurement of residual stress using neutron or synchrotron diffraction relies on the accurate alignment of the sample in relation to the gauge volume of the instrument. Automatic sample alignment can be achieved using kinematic models of the positioning system provided the relevant kinematic parameters are known, or can be determined, to a suitable accuracy. The main problem addressed in this thesis is improving the repeatability and accuracy of the sample positioning for the strain scanning, through the use of techniques from robotic calibration theory to generate kinematic models of both off-the-shelf and custom-built positioning systems. The approach is illustrated using a positioning system in use on the ENGIN-X instrument at the UK’s ISIS pulsed neutron source comprising a traditional XYZΩ table augmented with a triple axis manipulator. Accuracies better than 100microns were achieved for this compound system. Although discussed here in terms of sample positioning systems these methods are entirely applicable to other moving instrument components such as beam shaping jaws and detectors. Several factors could lead to inaccurate positioning on a neutron or synchrotron diffractometer. It is therefore essential to validate the accuracy of positioning especially during experiments which require a high level of accuracy. In this thesis, a stereo camera system is developed to monitor the sample and other moving parts of the diffractometer. The camera metrology system is designed to measure the positions of retroreflective markers attached to any object that is being monitored. A fully automated camera calibration procedure is developed with an emphasis on accuracy. The potential accuracy of this system is demonstrated and problems that limit accuracy are discussed. It is anticipated that the camera system would be used to correct the positioning system when the error is minimal or notify the user of the error when it is significant

Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version

Proceedings of the NASA Conference on Space Telerobotics, volume 3

The theme of the Conference was man-machine collaboration in space. The Conference provided a forum for researchers and engineers to exchange ideas on the research and development required for application of telerobotics technology to the space systems planned for the 1990s and beyond. The Conference: (1) provided a view of current NASA telerobotic research and development; (2) stimulated technical exchange on man-machine systems, manipulator control, machine sensing, machine intelligence, concurrent computation, and system architectures; and (3) identified important unsolved problems of current interest which can be dealt with by future research