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Developer(s) | Ansys Germany GmbH |
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Stable release | 23.2 / June 2023 |
Operating system | Cross-platform |
Platform | Intel x86 32-bit, x86-64 |
Available in | English |
Type | Simulation software |
License | Proprietary commercial software |
Website | optiSLang product page |
optiSLang is a software platform for CAE-based sensitivity analysis, multi-disciplinary optimization (MDO) and robustness evaluation. It was originally developed by Dynardo GmbH and provides a framework for numerical Robust Design Optimization (RDO) and stochastic analysis by identifying variables which contribute most to a predefined optimization goal. This includes also the evaluation of robustness, i.e. the sensitivity towards scatter of design variables or random fluctuations of parameters. [1] In 2019, Dynardo GmbH was acquired by Ansys. [2]
Representing continuous optimization variables by uniform distributions without variable interactions, variance based sensitivity analysis quantifies the contribution of the optimization variables for a possible improvement of the model responses. In contrast to local derivative based sensitivity methods, the variance based approach quantifies the contribution with respect to the defined variable ranges.
Coefficient of Prognosis (CoP) [3]
The CoP is a model independent measure to assess the model quality and is defined as follows:
Where is the sum of squared prediction errors. These errors are estimated based on cross validation. In the cross validation procedure, the set of support points is mapped to subsets. Then the approximation model is built by removing subset from the support points and approximating the subset model output using the remaining point set. This means that the model quality is estimated only at those points which are not used to build the approximation model. Since the prediction error is used instead of the fit, this approach applies to regression and even interpolation models.
Metamodel of Optimal Prognosis (MOP): [3]
The prediction quality of an approximation model may be improved if unimportant variables are removed from the model. This idea is adopted in the Metamodel of Optimal Prognosis (MOP) which is based on the search for the optimal input variable set and the most appropriate approximation model (polynomial or Moving Least Squares with linear or quadratic basis). Due to the model independence and objectivity of the CoP measure, it is well suited to compare the different models in the different subspaces.
Multi-disciplinary optimization:
The optimal variable subspace and approximation model found by a CoP/MOP procedure can also be used for a pre-optimization before global optimizers (evolutionary algorithms, Adaptive Response Surface Methods, Gradient-based methods, biological-based methods) are used for a direct single-objective optimization. After conducting a sensitivity analysis using MOP/CoP, also a multi-objective optimization can be performed to determine the optimization potential within opposing objectives and to derive suitable weighting factors for a following single-objective optimization. Finally this single-objective optimization determines an optimal design.
Robustness evaluation:
In variance-based robustness analysis, the variations of the critical model responses are investigated. In optiSLang, random sampling methods are used to generate discrete samples of the joined probability density function of the given random variables. Based on these samples, which are evaluated by the solver similarly as in the sensitivity analysis, the statistical properties of the model responses as mean value, standard deviation, quantiles and higher order stochastic moments are estimated.
Reliability analysis:
Within the framework of probabilistic safety assessment or reliability analysis, the scattering influences are modelled as random variables, which are defined by distribution type, stochastic moments and mutual correlations. The result of the analysis is the complementary of reliability, the probability of failure, which can be represented on a logarithmic scale.
optiSLang is designed to use several solvers to investigate mechanical, mathematical, technical and any other quantifiable problems. Herein optiSLang provides direct interfaces for external programs:
Since the 1980s, research teams at the University of Innsbruck and Bauhaus-Universität Weimar had been developing algorithms for optimization and reliability analysis in conjunction with finite element simulations. As a result, the software "Structural Language (SLang)" was created. In 2000, CAE engineers first applied it to conducted optimization and robustness analysis in the automotive industry. In 2001, the Dynardo GmbH was founded in 2003. Based on SLang, the software optiSLang was launched as an industrial solution for CAE-based sensitivity analysis, optimization, robustness evaluation and reliability analysis. In 2013, the current version optiSLang 4 was completely restructured with a new graphical user interface and extended interfaces to external CAE processes. [1]
Mathematical optimization or mathematical programming is the selection of a best element, with regard to some criterion, from some set of available alternatives. It is generally divided into two subfields: discrete optimization and continuous optimization. Optimization problems arise in all quantitative disciplines from computer science and engineering to operations research and economics, and the development of solution methods has been of interest in mathematics for centuries.
In mathematical optimization and decision theory, a loss function or cost function is a function that maps an event or values of one or more variables onto a real number intuitively representing some "cost" associated with the event. An optimization problem seeks to minimize a loss function. An objective function is either a loss function or its opposite, in which case it is to be maximized. The loss function could include terms from several levels of the hierarchy.
Multi-disciplinary design optimization (MDO) is a field of engineering that uses optimization methods to solve design problems incorporating a number of disciplines. It is also known as multidisciplinary system design optimization (MSDO), and multidisciplinary design analysis and optimization (MDAO).
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Stochastic approximation methods are a family of iterative methods typically used for root-finding problems or for optimization problems. The recursive update rules of stochastic approximation methods can be used, among other things, for solving linear systems when the collected data is corrupted by noise, or for approximating extreme values of functions which cannot be computed directly, but only estimated via noisy observations.
Probabilistic design is a discipline within engineering design. It deals primarily with the consideration and minimization of the effects of random variability upon the performance of an engineering system during the design phase. Typically, these effects studied and optimized are related to quality and reliability. It differs from the classical approach to design by assuming a small probability of failure instead of using the safety factor. Probabilistic design is used in a variety of different applications to assess the likelihood of failure. Disciplines which extensively use probabilistic design principles include product design, quality control, systems engineering, machine design, civil engineering and manufacturing.
Stochastic control or stochastic optimal control is a sub field of control theory that deals with the existence of uncertainty either in observations or in the noise that drives the evolution of the system. The system designer assumes, in a Bayesian probability-driven fashion, that random noise with known probability distribution affects the evolution and observation of the state variables. Stochastic control aims to design the time path of the controlled variables that performs the desired control task with minimum cost, somehow defined, despite the presence of this noise. The context may be either discrete time or continuous time.
IOSO is a multiobjective, multidimensional nonlinear optimization technology.
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SmartDO is a multidisciplinary design optimization software, based on the Direct Global Search technology developed and marketed by FEA-Opt Technology. SmartDO specialized in the CAE-Based optimization, such as CAE, FEA, CAD, CFD and automatic control, with application on various physics phenomena. It is both GUI and scripting driven, allowed to be integrated with almost any kind of CAD/CAE and in-house codes.
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Simulation-based optimization integrates optimization techniques into simulation modeling and analysis. Because of the complexity of the simulation, the objective function may become difficult and expensive to evaluate. Usually, the underlying simulation model is stochastic, so that the objective function must be estimated using statistical estimation techniques.
Probabilistic numerics is an active field of study at the intersection of applied mathematics, statistics, and machine learning centering on the concept of uncertainty in computation. In probabilistic numerics, tasks in numerical analysis such as finding numerical solutions for integration, linear algebra, optimization and simulation and differential equations are seen as problems of statistical, probabilistic, or Bayesian inference.
(Stochastic) variance reduction is an algorithmic approach to minimizing functions that can be decomposed into finite sums. By exploiting the finite sum structure, variance reduction techniques are able to achieve convergence rates that are impossible to achieve with methods that treat the objective as an infinite sum, as in the classical Stochastic approximation setting.