Toufik Al Khawli

Meta-modelling techniques towards virtual production intelligence

Decision making for competitive production in high-wage countries is a daily challenge where rational and irrational methods are used. The design of decision making processes is an intriguing, discipline spanning science. However, there are gaps in understanding the impact of the known mathematical and procedural methods on the usage of rational choice theory. Following Benjamin Franklin’s rule for decision making formulated in London 1772, he called “Prudential Algebra” with the meaning of prudential reasons, one of the major ingredients of Meta-Modelling can be identified finally leading to one algebraic value labelling the results (criteria settings) of alternative decisions (parameter settings). This work describes the advances in Meta-Modelling techniques applied to multi-dimensional and multi-criterial optimization in laser processing, e.g. sheet metal cutting, including the generation of fast and frugal Meta-Models with controlled error based on model reduction in mathematical physical or numerical model reduction. Reduced Models are derived to avoid any unnecessary complexity. The advances of the Meta-Modelling technique are based on three main concepts: (i) classification methods that decomposes the space of process parameters into feasible and non-feasible regions facilitating optimization, or monotone regions (ii) smart sampling methods for faster generation of a Meta-Model, and (iii) a method for multi-dimensional interpolation using a radial basis function network continuously mapping the discrete, multi-dimensional sampling set that contains the process parameters as well as the quality criteria. Both, model reduction and optimization on a multi-dimensional parameter space are improved by exploring the data mapping within an advancing “Cockpit” for Virtual Production Intelligence.

Meta-modeling for manufacturing processes

Meta-modeling for manufacturing processes describes a procedure to create reduced numeric surrogates that describe cause-effect relationships between setting parameters as input and product quality variables as output for manufacturing processes. Within this method, expert knowledge, empiric data and physical process models are transformed such that machine readable, reduced models describe the behavior of the process with sufficient precision. Three phases comprising definition, generation of data and creation of the model are suggested and used iteratively to improve the model until a required model quality is reached. In manufacturing systems, such models allow the generation of starting values for setting parameters based on the manufacturing task and the requested product quality. In-process, such reduced models can be used to determine the operating point and to search for alternative setting parameters in order to optimize the objectives of the manufacturing process, the product quality. This opens up the path to self-optimization of manufacturing processes. The method is explained exemplarily at the gas metal arc welding process.

flapAssist: How the integration of VR and visualization tools fosters the factory planning process

Virtual Reality (VR) systems are of growing importance to aid decision support in the context of the digital factory, especially factory layout planning. While current solutions either focus on virtual walkthroughs or the visualization of more abstract information, a solution that provides both, does currently not exist. To close this gap, we present a holistic VR application, called Factory Layout Planning Assistant (flapAssist). It is meant to serve as a platform for planning the layout of factories, while also providing a wide range of analysis features. By being scalable from desktops to CAVEs and providing a link to a central integration platform, flapAssist integrates well in established factory planning workflows.

An integrated approach for the knowledge discovery in computer simulation models with a multi-dimensional parameter space

In production industries, parameter identification, sensitivity analysis and multi-dimensional visualization are vital steps in the planning process for achieving optimal designs and gaining valuable information. Sensitivity analysis and visualization can help in identifying the most-influential parameters and quantify their contribution to the model output, reduce the model complexity, and enhance the understanding of the model behavior. Typically, this requires a large number of simulations, which can be both very expensive and time consuming when the simulation models are numerically complex and the number of parameter inputs increases. There are three main constituent parts in this work. The first part is to substitute the numerical, physical model by an accurate surrogate model, the so-called metamodel. The second part includes a multi-dimensional visualization approach for the visual exploration of metamodels. In the third part, the metamodel is used to provide the two global sensitivity measures: i...

Advanced Metamodeling Techniques Applied to Multidimensional Applications with Piecewise Responses

Due to digital changes in the solution properties of many engineering applications, the model response is described by a piecewise continuous function. Generating continuous metamodels for such responses can provide very poor fits due to the discontinuity in the response. In this paper, a new smart sampling approach is proposed to generate high quality metamodels for such piecewise responses. The proposed approach extends the Sequential Approximate Optimization SAO procedure, which uses the Radial Basis Function Network RBFN. It basically generates accurate metamodels iteratively by adding new sampling points, to approximate responses with discrete changes. The new sampling points are added in the sparse region of the feasible continuous domain to achieve a high quality metamodel and also next to the discontinuity to refine the uncertainty area between the feasible and non-feasible domain. The performance of the approach is investigated through two numerical examples, a two- dimensional analytical function and a laser epoxy cutting simulation model.

Improving the laser cutting process design by machine learning techniques

In the field of manufacturing engineering, process designers conduct numerical simulation experiments to observe the impact of varying input parameters on certain outputs of the production process. The disadvantage of these simulations is that they are very time consuming and their results do not help to fully understand the underlying process. For instance, a common problem in planning processes is the choice of an appropriate machine parameter set that results in desirable process outputs. One way to overcome this problem is to use data mining techniques that extract previously unknown but valuable knowledge from simulation results. This paper presents a hybrid machine learning approach for applying clustering and classification techniques in a laser cutting planning process. In a first step, a clustering algorithm is used to divide large parts of the simulation data into groups of similar performance values and select those groups that are of major interest (e.g. high cut quality results). Next, classification trees are used to identify regions in the multidimensional parameter space that are related to the found groups. The evaluation shows that the models accurately identify multidimensional relationships between the input parameters and the output values of the process. In addition to that, a combination of appropriate visualization techniques for clustering with interpretable classification trees allows designers to gain valuable insights into the laser cutting process with the aim of optimizing it through visual exploration.

Virtual Production Intelligence (VPI)

The research area Virtual Production Intelligence (VPI) focuses on the integrated support of collaborative planning processes for production systems and products. The focus of the research is on processes for information processing in the design domains Factory and Machine. These processes provide the integration and interactive analysis of emerging, mostly heterogeneous planning information. The demonstrators (flapAssist, memoSlice und VPI platform) that are information systems serve for the validation of the scientific approaches and aim to realize a continuous and consistent information management in terms of the Digital Factory. Central challenges are the semantic information integration (e.g., by means of metamodeling), the subsequent evaluation as well as the visualization of planning information (e.g., by means of Visual Analytics and Virtual Reality). All scientific and technical work is done within an interdisciplinary team composed of engineers, computer scientists and physicists.

Meta-modelling, visualization and emulation of multi-dimensional data for virtual production intelligence

Decision making for competitive production in high-wage countries is a daily challenge where rational and irrational methods are used. The design of decision making processes is an intriguing, discipline spanning science. However, there are gaps in understanding the impact of the known mathematical and procedural methods on the usage of rational choice theory. Following Benjamin Franklin’s rule for decision making formulated in London 1772, he called “Prudential Algebra” with the meaning of prudential reasons, one of the major ingredients of Meta-Modelling can be identified finally leading to one algebraic value labelling the results (criteria settings) of alternative decisions (parameter settings). This work describes the advances in Meta-Modelling techniques applied to multi-dimensional and multi-criterial optimization by identifying the persistence level of the corresponding Morse-Smale Complex. Implementations for laser cutting and laser drilling are presented, including the generation of fast and fru...

Metamodeling of laser cutting

Laser cutting is a thermal separation process widely used in shaping and contour cutting applications. It is a very fast and at the same time very accurate technology with the optical tool laser not being exposed to any wear. There are, however, gaps in understanding the dynamics of the process, especially with regard to issues related to cut quality. Numerical modeling and simulation of the laser cutting process has shown to improve that understanding without the need for executing a lot of experiments in the real world.In this paper, the utility of a metamodeling technique in gaining valuable information relating to the optimization of a laser cutting process, where a CW laser is used to cut, is analyzed. The numerical simulation itself is characterized by a high dimensional input parameter set. Each parameter has its own range, and thus they are together forming the parameter domain space. The quality criteria, which are predicted with the numerical model, are analyzed together with the parameter domai...