Industrial Test Cases Research Articles

Simultaneous production and distribution of industrial gas supply-chains

In this paper, we propose a multi-period mixed-integer linear programming model for optimal enterprise-level planning of industrial gas operations. The objective is to minimize the total cost of production and distribution of liquid products by coordinating production decisions at multiple plants and distribution decisions at multiple depots. Production decisions include production modes and rates that determine power consumption. Distribution decisions involve source, destination, quantity, route, and time of each truck delivery. The selection of routes is a critical factor of the distribution cost. The main goal of this contribution is to assess the benefits of optimal coordination of production and distribution. The proposed methodology has been tested on small, medium, and large size examples. The results show that significant benefits can be obtained with higher coordination among plants/depots in order to fulfill a common set of shared customer demands. The application to real industrial size test cases is also discussed.

Sustainable supply chain optimisation: An industrial case study

Sustainability plays a key role in the management of a successful and responsible business. When trying to improve the sustainability performance of a business, there are three major challenges that need to be addressed. First, assessment of sustainability requires consideration of not just economic, but also environmental and social impacts. Second, we need to find appropriate sustainability indicators and gather the necessary data in order to quantify sustainability performance. Finally, sustainability has to be seen in the context of the whole system, i.e. it has to include all activities along the supply chain. In this work, we consider all three aspects and propose a multi-objective optimisation framework for the optimisation of a sustainable supply chain. Three sustainability indicators have been considered, namely the total cost, GHG emissions and lead time. We apply this framework to an industrial test case using real-world data drawn from a Dow Chemical business. The results show clear trade-offs between the three different objectives. However, we can also observe that typically a considerable decrease in GHG emissions or lead time can already be achieved by only a relatively small increase in cost. The proposed framework enables us to determine such trade-off relations and consequently make decisions that improve the sustainability performance of the supply chain.

Producing, storing, using and selling renewable energy: The best mix for the small medium industry

Over the last decades, the production of “sustainable energy” has provided a very fertile research field, involving aspects that are traditionally considered in an independent manner, namely renewable energy production, energy storage and efficient usage of available energy. A combined analysis of these three aspects within an industrial context is the main focus of this work.We provide an insight on the problems that a small or medium manufacturing firm can expect to address when it decides to move from traditional energy suppliers to an as much as possible autonomous energy production. In particular, we consider the contribution that ICT can offer in order to allow the firm to decide the best size and composition of its own “energy production plant”, based on data regarding its production needs and weather-related data.We propose an open source framework aimed at making it possible to model various systems including both energy production, storage and consumption elements. The framework also allows the use of different approaches to optimize and fine tune the system in terms of both design and usage costs. We show how the framework can be specialized in order to be used for a typical industrial test case representing a small medium manufacturing firm that decides to change its position from a pure energy consumer to an energy combined producer, storer and user.

Preconditioning for Efficiently Applying Algebraic Multigrid in Fully Implicit Reservoir Simulations

Summary Fully implicit black-oil simulations result in huge, often very-ill-conditioned, linear systems of equations for different unknowns (e.g., pressure and saturations). It is well-known that the underlying Jacobian matrices contain both hyperbolic and nearly elliptic subsystems (corresponding to saturations and pressure, respectively). Because a reservoir simulation is typically driven by the behavior of the pressure, constrained-pressure-residual (CPR)-type two-stage preconditioning methods to solve the coupled linear systems are a natural choice and still belong to the most popular approaches. After a suitable extraction and decoupling, the computationally most costly step in such two-stage methods consists in solving the elliptic subsystems accurately enough. Algebraic multigrid (AMG) provides a technique to solve elliptic linear equations very efficiently. Hence, in recent years, corresponding CPR-AMG approaches have been extensively used in practice. Unfortunately, if applied in a straightforward manner, CPR-AMG does not always work as expected. In this paper, we discuss the reasons for the lack of robustness observed in practice, and present remedies. More precisely, we will propose a preconditioning strategy (based on a suitable combination of left and right preconditioning of the Jacobian matrix) that aims at a compromise between the solvability of the pressure subproblem by AMG and the needs of the outer CPR process. The robustness of this new preconditioning strategy will be demonstrated for several industrial test cases, some of which are very ill-conditioned. Furthermore, we will demonstrate that CPR-AMG can be interpreted in a natural way as a special AMG process applied directly to the coupled Jacobian systems.

Using a Formal High-level Language to Instruct Manikins to Assemble Cables

In this paper, a formal high-level language is used to generate simulations where a manikin assembles flexible cables. The language generates assembly instructions for the manikin, which automatically performs the corresponding assembly motion with as good ergonomic as possible. Due to weight, stiffness and narrow regions, it may be difficult to perform an assembly of the cable. Our approach allows us to verify that it may be performed in an ergonomically sound way. The generated instructions are formally verified to ensure that assembly order is held and to prevent erroneous assembly states. The simulations have been made on industrial test cases.

A Decision Support Tool for Optimising Support Site Configuration of Functional Products

The customization of the support site configuration (including the number, locations and capabilities of sites where maintenance staff are based) is of critical importance to functional product providers, who must provide maintenance support services for products operated by their customers at different locations and ensure that contractual guarantees for functional availability are met whilst keeping support costs under control. Since contract fulfilment costs are performance based and long term, they are difficult to predict without modelling. This paper discusses a decision support tool designed for use by management and engineering personnel at Functional Product providers to analyse and optimize the performance of their support base configuration. It features a graphical user interface for configuration customization, simulation modelling to predict performance and outputs a wide range of analytics that can be used to compare and optimize configurations. The tool is demonstrated via application to an industrial test case.

Time-Domain Harmonic Balance Method for Turbomachinery Aeroelasticity

The present paper investigates a time-domain harmonic balance method as an alternative to classical time-marching schemes for stability studies of turbomachineries toward flutter. A weak-coupling approach is applied, which requires computing the fluid response to prescribed harmonic motions of the structure. The harmonic balance method, formulated in the arbitrary Lagrangian/Eulerian framework, is adapted to single-passage reduction using phase-lag boundary conditions expressed purely in the time domain. Validation against experimental data for the 11th standard configuration for aeroelasticity is performed, showing good agreement. Finally, an industrial test case is presented: a fan designed by Safran Snecma. The results show the good accuracy of the proposed harmonic balance method as well as significant reductions in computational time.

Non-nominal path planning for robust robotic assembly

In manufacturing and assembly processes it is important, in terms of time and money, to verify the feasibility of the operations at the design stage and at early production planning. To achieve that, verification in a virtual environment is often performed by using methods such as path planning and simulation of dimensional variation. Lately, these areas have gained interest both in industry and academia, however, they are almost always treated as separate activities, leading to unnecessary tight tolerances and on-line adjustments.To resolve this, we present a novel procedure based on the interaction between path planning techniques and variation simulation. This combined tool is able to compute robust assembly paths for industrial robots, i.e. paths less sensitive to the geometrical variation existing in the robot links, in its control system, and in the environment. This may lead to increased productivity and may limit error sources. The main idea to improve robustness is to enable robots to avoid motions in areas with high variation, preferring instead low variation zones. The method is able to deal with the different geometrical variation due to the different robot kinematic configurations. Computing variation might be a computationally expensive task or variation data might be unavailable in the entire state space, therefore three different ways to estimate variation are also proposed and compared. An industrial test case from the automotive industry is successfully studied and the results are presented.

Automatic assembly path planning for wiring harness installations

The automotive industry of today is becoming more focused on electrified and hybrid solutions, where both conventional combustion engines and battery supplied electrical engines need to fit in an already densely packed vehicle. Many quality problems are related do flexible parts. In particular, the assembly of electric cables and wiring harnesses is difficult due to its concealed routing, multiple branching points, weights and the flexibility in the material. To avoid late detection of assembly problems, the assembly aspect must be considered early during conceptual design and production preparation with respect to both feasibility and ergonomics. Development of automatic path planning methods in virtual manufacturing tools supporting deformable parts is therefore highly motivated.This article presents a novel method for automatically planning and finding a smooth and collision-free mounting of connectors in a wiring harness installation. Automatic path planning for deformable objects in general is widely acknowledged as a very difficult problem. To overcome this challenge, we propose a low-dimensional path planning algorithm that operates in the following way: constraint relaxation, handle path planning, unfolding, path smoothing and handle supplementation. The method has been implemented and successfully applied to an industrial test case.

Performance assessment of modelling tools for high resolution runoff simulation over an industrial site

Intense rainfall can generate storm sewer system failures along with large surface runoff events which represent an issue for industrial sites' security assessment. Numerical modelling tools, including standard bi-dimensional (2D) free surface flow models, are applied in a wide variety of flood risk practical studies straight from the purpose for which they had originally been designed. This study focuses on possibilities, performances and limits of the use of standard modelling tools for high resolution runoff simulations over an industrial site. Two categories of runoff scenarios are tested over this industrial site test case, with three modelling tools relying on different numerical schemes. Simulated water depth evolutions are found to be comparable between modelling tools, nevertheless, the possibilities of these modelling tools' optimal use with a highly refined topographical resolution for runoff scenarios are revealed to be unequal. Used indicators for computation reliability checks do not point out major inconsistencies in calculation under critical models' optimisation. Indeed, emphasis is placed on restrictive aspects to achieve with standard modelling tools a balance between computational stability, swift and precise in high resolution runoff modelling.

All-hexahedral meshing and remeshing for multi-object manufacturing applications

All-hexahedral meshing and remeshing algorithms giving support to finite element modeling of manufacturing processes require continuous development for improving its overall robustness and applicability. This paper draws from a previous all-hexahedral algorithm presented by the authors and proposes new developments related to the construction of adaptive core meshes and processing of multi-objects that are typical of manufacturing applications.Along with the aforementioned improvements there are other developments that will also be presented due to their effectiveness in increasing the robustness of all-hexahedral algorithms. These include identification and simplification of boundary features, reconstruction of vertices and edges with minimum element distortion, smoothing of nodal points along edges and topology based mesh repair procedures to ensure completeness of edge representation.The presentation is enriched with examples taken from pure geometry and metal forming applications, and a resistance projection welding industrial test case consisting of four different objects is included to show the capabilities of selective remeshing of objects while maintaining contact conditions and local geometrical details that are critical for electro-thermo-mechanical numerical simulations.

Synchronizing AMS Assertions with AMS Simulation

The verification community anticipates the adoption of assertions in the Analog and Mixed-Signal (AMS) domain in the near future. Several questions need to be answered before AMS assertions are brought into practice, such as: (a) How will the languages for AMS assertions be different from the ones in the digital domain? (b) Does the analog simulator have to be assertion aware? (c) If so, then how and where on the time line will the AMS assertion checker synchronize with the analog simulator? and (d) What will be the performance penalty for monitoring AMS assertions accurately over analog simulation? This article attempts to answer these questions through theoretical analysis and empirical results obtained from industrial test cases. We study logics which extend Linear Temporal Logic (LTL) with predicates over real variables, and show that further extensions allowing the binding of real-valued variables across time makes the logic undecidable. We present a toolkit which can integrate with existing AMS simulators for checking AMS assertions on practical designs. We study the problem of synchronizing the AMS simulator with the AMS assertion checker and demonstrate the performance penalty of different synchronization options.

Aspects of adaptive hierarchical RBF metamodels for optimization

Radial basis functions (RBFs), among other techniques, are used to construct metamodels that approximate multi-objective expensive high-fidelity functions from a finite number of function evaluations (design of experiments, DoE). Radial basis functions can be applied if the DoE covers the parameter space in an arbitrary though uniform manner. Leave-one-out strategies allow for computing tolerance limits. The approximated value and a certain tolerance can be interpreted as expectation and variance of a random experiment. Thus, model improvement as described for Kriging models in the literature can in principal be applied to RBF-based metamodels, too. We describe our adaptive and hierarchical metamodelling approach that deals with the specific problems that such metamodel adaptions pose to RBF-based models. We also briefly discuss implementation details and first industrial test cases.

SIMPLE‐type preconditioners for cell‐centered, colocated finite volume discretization of incompressible Reynolds‐averaged Navier–Stokes equations

SUMMARYThis paper contains a comparison of four SIMPLE‐type methods used as solver and as preconditioner for the iterative solution of the (Reynolds‐averaged) Navier–Stokes equations, discretized with a finite volume method for cell‐centered, colocated variables on unstructured grids. A matrix‐free implementation is presented, and special attention is given to the treatment of the stabilization matrix to maintain a compact stencil suitable for unstructured grids. We find SIMPLER preconditioning to be robust and efficient for academic test cases and industrial test cases. Compared with the classical SIMPLE solver, SIMPLER preconditioning reduces the number of nonlinear iterations by a factor 5–20 and the CPU time by a factor 2–5 depending on the case. The flow around a ship hull at Reynolds number 2E9, for example, on a grid with cell aspect ratio up to 1:1E6, can be computed in 3 instead of 15 h.Copyright © 2012 John Wiley & Sons, Ltd.

LOcal Uncertainty Processing (LOUP) method for multidisciplinary robust design optimization

In this paper, we develop an easy-to-implement approximate method to take uncertainties into account during a multidisciplinary optimization. Multidisciplinary robust design usually involves setting up a full uncertainty propagation within the system, requiring major modifications in every discipline and on the shared variables. Uncertainty propagation is an expensive process, but robust solutions can be obtained more easily when the disciplines affected by uncertainties have a significant effect on the objectives of the problem. A heuristic method based on local uncertainty processing (LOUP) is presented here, allowing approximate solving of specific robust optimization problems with minor changes in the initial multidisciplinary system. Uncertainty is processed within the disciplines that it impacts directly, without propagation to the other disciplines. A criterion to verify a posteriori the applicability of the method to a given multidisciplinary system is provided. The LOUP method is applied to an aircraft preliminary design industrial test case, in which it allowed to obtain robust designs whose performance is more stable than the one of deterministic solutions, relatively to uncertain parameter variations.

Memory efficient hybrid algebraic solvers for linear systems arising from compressible flows

This paper deals with the solution of sparse linear systems arising from design optimization in computational fluid dynamics. In this approach, a linearization of the discretized compressible Navier–Stokes equations is built, in order to evaluate the sensitivity of the entire flow with respect to each design parameter. This requires an efficient and robust parallel linear solver, to generate the exact flow derivatives: from the algebraic decomposition of the input matrix, a hybrid robust direct/iterative solver is generally defined with a Krylov subspace method as accelerator, a domain decomposition method as preconditioner and a direct method as subdomain solver. The goal of this paper is to reduce the memory requirements and indirectly, the computational cost at different steps of this scheme. To this end, we use a grid-point induced block approach for the data storage and the partitioning part, a Krylov subspace method based on the restarted GMRES accelerated by deflation, a preconditioner formulated with the restricted additive Schwarz method and an aerodynamic/turbulent fields split at the subdomain level. Numerical results are presented with industrial test cases to show the benefits of these choices.

$O(mn)$ Time Algorithm for Optimal Buffer Insertion of Nets With $m$ Sinks

Buffer insertion is an effective technique to reduce interconnect delay. In this paper, we give a simple O(mn) time algorithm for optimal buffer insertion, where m is the number of sinks and n is the number of buffer positions. When m is small, our algorithm is a significant improvement over the recent O(nlog2n) time algorithm by Shi and Li, and the O(n2) time algorithm of van Ginneken. For b buffer types, our algorithms runs in O(b2n+bmn) time, an improvement of the recent O(bn2) algorithm by Li and Shi. The improvement is made possible by an innovative linked list that can perform addition of a wire, addition of a buffer in amortized O(1) time, and smart design of pointers. We then present the extension of our algorithm for the buffer cost minimization problem, which improves the previous best algorithm. On industrial test cases, the new algorithms is faster than previous best algorithms by an order of magnitude.

ECOS: Stable Matching Based Metal-Only ECO Synthesis

To ease the time-to-market pressure and save the photomask cost, metal-only ECO realizes the last-minute design changes by revising the photomasks of metal layers only. This task is challenging because the pre-injected spare cells are limited in number and in cell types. Metal-only ECO has to implement these functional and/or timing changes using available spare cells. In this paper, we propose a stable matching based metal-only ECO synthesizer, named ECOS, that can implement the incremental design changes correctly without sacrificing timing and routability. The experiments are conducted on nine industrial testcases. These testcases reflect the real difficulties faced by designers and our results show that ECOS is promising for all of them.

Postgrid Clock Routing for High Performance Microprocessor Designs

Designing a high-quality clock network is very important in very large-scale integrated designs today, as it is the clock network that synchronizes all the elements of a chip, and it is also a major source of power dissipation of a system. Early study by Pham in 2006 shows that about 18.1% of the total clock capacitance was due to this postgrid clock routing (i.e., lower mesh wires plus clock twig wires). In this paper, we proposed a partition-based path expansion algorithm to solve this postgrid clock routing problem effectively. Experimental results on industrial test cases show that our algorithm can improve over the latest work by Shelar on this problem significantly by reducing the wire capacitance by 24.6% and the wirelength by 23.6%.

Role of the electro-thermo-mechanical multiple coupling on the operation of RF-microswitch

A phenomenological approach is proposed to identify some effects occurring within the structure of the microswitch conceived for radio frequency application. This microsystem is operated via a nonlinear electromechanical action imposed by the applied voltage. Unfortunately, it can be affected by residual stress, due to the microfabrication process, therefore axial and flexural behaviors are strongly coupled. This coupling increases the actuation voltage required to achieve the so-called “pull-in” condition. Moreover, temperature may strongly affect strain and stress distributions, respectively. Environmental temperature, internal dissipation of material, thermo-elastic and Joule effects play different roles on the microswitch flexural displacement. Sometimes buckling phenomenon evenly occurs. Literature show that all those issues make difficult an effective computation of “pull-in” and “pull-out” voltages or evenly distinguishing the origin of some failures detected in operation. Analysis, numerical methods and experiments are applied to an industrial test case to investigate step by step the RF-microswitch operation. Multiple electro-thermo-mechanical coupling is first modeled to have a preliminary and comprehensive description of the microswitch behavior and of its reliability. “Pull-in” and “pull-out” tests are then performed to validate the proposed models and to find suitable criteria to design the RF-MEMS.