An Additive Manufacturing Path Generation Method Based on CAD Models for Robot Manipulators

Traditional extrusion based Additive Manufacturing (AM) is realized using a 3 Degrees of Freedom (DOF), translation only, 3D printer. Here, the printer must be larger than the printed part. One way of enabling AM in large-scale is to combine AM with robotics. By using a 6 DOF robot manipulator to extrude a fast-curing material, the workspace of the build would be greatly expanded and it would be possible to increase the flexibility of the building process itself since the structure would no longer have to be built from the bottom-up approach which is necessary for most existing forms of AM. This could possibly reduce the need for support structures to the point of only relying of anchoring and stabilizing. In this thesis, a method for generating a path for AM using robot manipulators that takes advantages of the robots DOF is presented. The path is generated based on simple surfaces in CAD models. First, the surface(s) is sampled and the samples are gathered in a point cloud. Then, a path is generated based on the point cloud using a path generation algorithm. Three different path generation algorithms was implemented and tested: greedy choice, weighted greedy choice and Travelling Salesman Problem (TSP). Out of the three algorithms, the weighted greedy choice algorithm shows the most promise. With this algorithm, paths that enable printing along curved surfaces and reducing the need for support structures was generated. The method is effective, and by interfacing with FreeCAD, it is easy to review the generated paths through visual aids. It is, however, important to mention that the method only generates paths based on simple surfaces and is based on the assumption of fast-curing material enabling mid-air printing

Exploring subset profile and validation procedures of geographical markup language (GML) for 3D areal plan information

In the paper we explain our experiences in the work towards a GML subset profile for Norwegian Areal Plan data sets, and how this GML subset profile together with requirements form the UML based conceptual application schema that can be used for data validation. GML is about to be the preferred exchange language for geographical information in Norway. One challenge using GML, slowing down the implementation of GML in Norway, is the complexity, e.g. the possibilities of representing the same information in multiple ways. In all digital information handling, automated validation is important. For data validation, both the digital data and the requirements to the data are needed in suitable languages/formats. ISO 19136 define the “ISO-certified” version of GML. The Annex G of ISO19136 have guidelines for defining GML subset profiles. Using GML subset profiles the unneeded complex parts and alternative solutions in GML can be removed, and data still be conformant to the full GML. Selected activities considering GML profiles are investigated: INSPIRE, CityGML and OGC GML SimpleFeatureProfile. The surprising finding from this investigation is the lack of formal GML profiles to be used for data validation. In all the three activities, subsets of GML are explained only using text for human reading, to some degree pointing to recommended UML modelling practice. None of the three activities have made available official XSD schema files for information validation following their text-based GML subset profiles. For the XML-based GML, the natural data validation start is XSD-based data structure validation against the formal XSD application schema. For validation of geometry (e.g. closure of polygons and solids) additional requirements to the “pure” XSD data structure rules are needed. Some geometry requirements can be derived directly from the GML semantics, e.g. a GML Ring should be a closed curve and a GML CompositeCurve should have only connected curve subparts. Some other geometry requirements are connected to the semantics of the defined feature types in the user application schema, e.g. the spatial extent of a county should be inside the spatial extent of the country. For geographic information described using UML and based on the ISO19109 General Feature Model, UML classes representing feature types are important modelling elements. We have added geometry requirements to UML-based feature types and made this available for validation on the dataset (GML) level. The geometry requirements are defined using the ISO19157 Data Quality / Data Quality Measure (DQM) principles. In the context of this paper, only quality category Logical Consistency DQMs are relevant. In the paper we explain the experience with defining and validating rather general geometry rules connected to polygon geometry; polygon/polygon relationships and polygon set/tessellations rules. The paper ends with conclusions and recommendations for further worksubmittedVersionThis is a submitted manuscript of an article published in International Multidisciplinary Scientific GeoConference SGEM, 201

How do age structure and urban form influence household CO2 emissions in road transport? Evidence from municipalities in Norway in 2009, 2011 and 2013

This article investigates the influence of age structure on CO2 emissions from household road transport by using an extended STIRPAT model plus data from 380 Norwegian municipalities for 2009, 2011 and 2013. After controlling for population, household income, age structures, household size, and different urban forms (urbanization, urban density, housing type, building density), the paper reveals that the age group responsible for the highest CO2 emissions is 50–69, followed by 20–34 and 35–49. Moreover, compared with other groups, the road transport activities of age group 35–49 are highly constrained by household income. The paper also shows that there is an inverted U-shape relationship between household CO2 road-related emissions and building densities. However, it indicates certain limitations on city planners when it comes to reducing household CO2 road-related emissions by bringing the downtown area closer. Moreover, the paper also identifies a so-called compensatory mechanism supporting the hypothesis that building densities have positive effects. Furthermore, the coefficient of low-density housing is positive and significant, implying that the private gardens of low-density housing might not be the reason for the hypothesized compensatory mechanism. However, this remains a question worth investigating.publishedVersionThis is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Evaluating the Arctic SDI: An Assessment of the Foundations needed for Success

The Arctic encompasses eight countries and has a population of over four million people. With datasets produced by private and public stakeholders all over the world and noted gaps in data for many parts of the region, there is an opportunity to collaborate and create a unified Spatial Data Infrastructure (SDI) for the Arctic. This research identified a set of criteria for evaluating the long-term efficacy of the Arctic SDI from an organizational perspective and not from a user’s perspective. Through the external assessment, half of the countries were found to be strong contributors - almost equally contributing in terms of deliverables, resources and leadership to the Arctic SDI. These three themes developed based on a critical evaluation of the existing SDI literature. While the other half countries contributed noticeably less - due to a lack of deliverables, less participation in working groups or little or no resource contributions. Complementing theses (external) assessments, also internal reviews were conducted via semi-structured interviews, which obtained the participants’ view of the Arctic SDI collaboration potential successes and shortcomings. The interviewees identified opportunities, limitations and risks as they perceived them. Most of the issues associated with the opportunities, limitations and risks could be cross-validated with the external assessment criteria. However, the importance of communication was strongly emphasized in the interviews and was not represented by the external assessment criteria. The completion of both the external and internal assessments led to the multi-view framework that can be used to assess the long-term potential of the Arctic SDI. This evaluation tool can also be used for defining tasks and clarifying responsibilities for the next 5-year Memorandum of Understanding (2019-2024) or to assess the Arctic SDI to identify challenges and mitigation measures that would assist in its longevity. This tool can also be used for other regional SDIs to define MoUs and assess the potential for success.publishedVersionThis work is licensed under the Creative Commons Attribution-Non commercial Works 3.0 Licens

Cascading trade-off studies for robotic deburring systems

Advanced manufacturing technologies play an important role in keeping production in high-cost countries. Due to their flexibility, robot-based solutions have been one of the major enablers in establishing advanced manufacturing capabilities in the traditional high-cost countries. This paper concerns the problem of automated deburring of cast parts. If performed manually, this operation introduces major health, safety, and environmental (HSE) concerns. As such, removal of highly variable casting burrs in the Norwegian context requires a solution based on robots, smart sensors, and advanced algorithms to tackle the problem in a flexible and cost-effective way. Due to the complexity of the task, one is confronted with a breadth of various alternatives to choose from when realizing the desired functionality. These alternatives expand as one considers a pipeline of the subtasks involved in the process. The decisions made in each step cascade throughout the whole pipeline. To tackle the complexity while developing a robotized deburring system, a systemic approach based on cascading trade-off studies is proposed in this paper. This paper is also a contribution to the gap in the literature for cases of trade-off studies in the domain of mechanical engineering. The SPADE (stakeholders, problem formulation, analysis, decision making, and evaluation) methodology has been used as a framework to resolve automation of complex mechanical engineering manufacturing process decisions. The systems engineering (SE) approach proved useful to identify and prioritize the stakeholders and their needs, as well as analyzing the different alternatives in a complex engineering system when dealing with cascading trade studies.publishedVersio

Data-driven control in marine systems

With the advent of cheap smart sensors installed on board marine vehicles and the increasing computational power of small embedded processors there is tremendous potential for the implementation of new strategies to control marine systems on the basis of input-output plant data. The emerging field of smart sensors affords a unique opportunity to have access to on-line measurement of dynamical systems’ variables seamlessly, at a low price. By applying a data-driven control algorithm to a marine vehicle, the paper introduces a new perspective on how data can be used in the control loop in marine systems. Classical control methodologies start by developing a model of the plant to be controlled, after which a number of control design techniques can be used. Recent advances in so-called model-free data-driven control methodologies, in particular unfalsified control, hold promise to merge the identification and control phases. Unfalsified control techniques build on the construction of a bank of controllers for a given plant, in which there exists at least one controller that meets the desired performance specification and a falsification unit. The latter is implemented using a cost function that directly evaluates the performance of the controllers (in and out of the feedback loop) using measured input and output data. At each sampling time, the performance of the controllers is assessed and the controllers that do not meet the pre-defined performance specification criteria will be falsified and removed from the bank of the controllers, after which an active controller will be selected among the unfalsified ones. In this paper, by presenting the results of the application of unfalsified control to the problem of Dynamic Positioning (DP) of marine vessels subjected to environmental forces, we aim to attract the attention of researchers in the field of marine control to the new perspective of using data to directly control marine system.acceptedVersion© 2018. This is the authors’ accepted and refereed manuscript to the article. Locked until 22.10.2020 due to copyright restrictions. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0

Overview of Emerging Technologies for Improving the Performance of Heavy-Duty Construction Machines

Construction equipment is one of the most significant resources in large construction projects, accounting for a considerable portion of the project budget. Improving the performance of heavy machinery can increase efficiency and reduce costs. However, research on boosting the machine efficiency is limited. This study adopts a mixed review methodology (systematic review and bibliometric analysis) and evaluates emerging technologies such as digital twin, cyber physical systems, geographic information systems, global navigation satellite systems, onboard instrumentation systems, radio frequency identification, internet of things, telematics, machine learning, deep learning, and computer vision for machine productivity, and provides insights into how they can be used to improve the performance of construction equipment. This study defined three major equipment operating areas—monitoring and control, tracking and navigation, and data-driven performance optimization—classified technologies and explored how they can increase machine productivity. Other circumstantial issues affecting machine operation and loopholes in the existing innovative tools used in machine processes have also been highlighted. This study contributes to the goal of deploying digital tools and outlines future directions for the development of automated machines to optimize project efficiency.publishedVersio

Habitat deterioration promotes the evolution of direct development in metamorphosing species

Although metamorphosis is widespread in the animal kingdom, several species have evolved life-cycle modifications to avoid complete metamorphosis. Some species, for example, many salamanders and newts, have deleted the adult stage via a process called paedomorphosis. Others, for example, some frog species and marine invertebrates, no longer have a distinct larval stage and reach maturation via direct development. Here we study which ecological conditions can lead to the loss of metamorphosis via the evolution of direct development. To do so, we use size-structured consumer-resource models in conjunction with the adaptive-dynamics approach. In case the larval habitat deteriorates, individuals will produce larger offspring and in concert accelerate metamorphosis. Although this leads to the evolutionary transition from metamorphosis to direct development when the adult habitat is highly favorable, the population will go extinct in case the adult habitat does not provide sufficient food to escape metamorphosis. With a phylogenetic approach we furthermore show that among amphibians the transition of metamorphosis to direct development is indeed, in line with model predictions, conditional on and preceded by the evolution of larger egg sizes