Creation of helicopter dynamic systems digital twin using multibody simulations

International audienceThis paper presents a new approach to develop digital twins of helicopter dynamic systems. Helicopter industries attach growing attention to the development of digital twins to be more predictive of mechanical parts lifetime. The number of sensors available to measure loads during flights is limited. Complementary simulations are necessary to compute all the loads that the mechanical parts undergo. A new process is described to build these simulations fed with flights data records. Complexity of helicopters dynamics systems leads to create several local models of subsystems using a multibody dynamic formalism. A study focused on a swashplate rotor assembly is presented to illustrate this approach, including a new model of bearing and its validation based on bench tests

Evaluating Process-Based Integrated Assessment Models of Climate Change Mitigation

Process-based integrated assessment models (IAMs) analyse transformation pathways to mitigate climate change. Confidence in models is established by testing their structural assumptions and comparing their behaviour against observations as well as other models. Climate model evaluation is concerted, and prominently reported in a dedicated chapter in the IPCC WG1 assessments. By comparison, evaluation of process-based IAMs tends to be less visible and more dispersed among modelling teams, with the exception of model inter-comparison projects. We contribute the first comprehensive analysis of process-based IAM evaluation, drawing on a wide range of examples across eight different evaluation methods testing both structural and behavioural validity. For each evaluation method, we compare its application to process-based IAMs with its application to climate models, noting similarities and differences, and seeking useful insights for strengthening the evaluation of process-based IAMs. We find that each evaluation method has distinctive strengths and limitations, as well as constraints on their application. We develop a systematic evaluation framework combining multiple methods that should be embedded within the development and use of process-based IAMs

Enhancing global climate policy ambition towards a 1.5 °C stabilization: a short-term multi-model assessment

The Paris Agreement is a milestone in international climate policy as it establishes a global mitigation framework towards 2030 and sets the ground for a potential 1.5 °C climate stabilization. To provide useful insights for the 2018 UNFCCC Talanoa facilitative dialogue, we use eight state-of-the-art climate-energy-economy models to assess the effectiveness of the Intended Nationally Determined Contributions (INDCs) in meeting high probability 1.5 and 2 °C stabilization goals. We estimate that the implementation of conditional INDCs in 2030 leaves an emissions gap from least cost 2 °C and 1.5 °C pathways for year 2030 equal to 15.6 (9.0–20.3) and 24.6 (18.5–29.0) GtCO2eq respectively. The immediate transition to a more efficient and low-carbon energy system is key to achieving the Paris goals. The decarbonization of the power supply sector delivers half of total CO2 emission reductions in all scenarios, primarily through high penetration of renewables and energy efficiency improvements. In combination with an increased electrification of final energy demand, low-carbon power supply is the main short-term abatement option. We find that the global macroeconomic cost of mitigation efforts does not reduce the 2020–2030 annual GDP growth rates in any model more than 0.1 percentage points in the INDC or 0.3 and 0.5 in the 2 °C and 1.5 °C scenarios respectively even without accounting for potential co-benefits and avoided climate damages. Accordingly, the median GDP reductions across all models in 2030 are 0.4%, 1.2% and 3.3% of reference GDP for each respective scenario. Costs go up with increasing mitigation efforts but a fragmented action, as implied by the INDCs, results in higher costs per unit of abated emissions. On a regional level, the cost distribution is different across scenarios while fossil fuel exporters see the highest GDP reductions in all INDC, 2 °C and 1.5 °C scenarios

Geometry of GL_n(C) on infinity: complete collineations, projective compactifications, and universal boundary

Consider a finite dimensional (generally reducible) polynomial representation \rho of GL_n. A projective compactification of GL_n is the closure of \rho(GL_n) in the space of all operators defined up to a factor (this class of spaces can be characterized as equivariant projective normal compactifications of GL_n). We give an expicit description for all projective compactifications. We also construct explicitly (in elementary geometrical terms) a universal object for all projective compactifications of GL_n.Comment: 24 pages, corrected varian

Concurrent process mapping, organizations, project and knowledge management in large-scale product development projects using the Design Structure Matrix method

Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (p. 149-152).Sustainable success in product design and development relies not only on technical expertise and creativity within the company but as crucially, if not more, on an intelligent design of the development process, an appropriate and dynamic management of organizations, a realistic and disciplined project management, and on efficient knowledge generation, conservation and distribution techniques. These non-engineering skills pose serious challenges to companies designing complex systems like airplanes or automobiles. As these systems have gotten tremendously more complex, their design has kept involving more people, from different working cultures inside and outside the company, all within tighter time constraints. Adaptation to this new context of product development has nevertheless often been very slow because of persistent corporate traditions inherited from the past. The purpose of this thesis is to demonstrate that Process Mapping and Improvement, Organizations Management, Project Management and Knowledge Management can be reconciled and performed all at once using the Design Structure Matrix (DSM) Method, enabling large and relatively easy improvements of the design activity's efficiency. The state-of-the-art in each of the four mentioned fields is first reviewed. The methodology used throughout this thesis, the Design Structure Matrix (DSM) is then presented. The DSM method and some issues of knowledge management are illustrated in a short case study conducted in January 2002 at PSA Peugeot-Citroen in Paris, France. The promising unifying benefits of the DSM method are then thoroughly described through a large project that took place in Summer 2002 at Ford Motor Company in Dearborn, Michigan. It exhibits how DSMs can provide permanent system-level knowledge, guide the design practitioner through a complex process that would hardly be understood otherwise, enable a dynamic management of organizations and open opportunities for process improvement and redesign. The lessons learned finally lead to recommendations on the practice of the DSM method as well as product development in general.by Antoine D. Guivarch.S.M