Titel Deelnemers "Korte inhoud"
"AAA rational approximation for time domain model order reduction" "Giovanni Conni, Frank Naets" "In this paper an extension of the Adaptive Antoulas-Anderson (AAA) Model Order Reduction (MOR) method to time-domain data is defined, referred to as Time-Domain AAA (TDAAA). Inspired by other rational approximation time-domain MOR methods, like Time-Domain Vector Fitting (TDVF) and Time-Domain Loewner Framework (TDLF), TDAAA combines the adaptivity and flexibility of the AAA method in the frequency domain with an error minimization in the time domain. This combination makes the method an interesting alternative to fully time-domain or frequency-domain MOR methods. A combination of AAA and TDVF is also proposed, called AAA-TDVF, where the initial TDVF poles are selected by AAA. This new poles initialization improves both accuracy and convergence speed. Both TDAAA and TDVF are discussed in detail and their performance is compared on a benchmark LTI system."
"High-fidelity modelling of lubricated transmissions using a coupled finite element approach" "Sander Neeckx, Régis Boukadia, Frank Naets, Wim Desmet" "This work presents a high-fidelity lubricated transmission model, coupling Flexible MultiBody (FMB) dynamics with ElastoHydrodynamic Lubrication (EHL). The EHL model is discretised with a coupled finite element approach, in contrast with the more iteration-intensive finite difference approach using relaxation schemes. The finite element method yields nonlinear system matrices, requiring matrix reevaluation in each iteration. To mitigate computational overhead, tensorisation replaces integrals to compute the system matrices with tensor-vector multiplications. Furthermore, this work optimises the use of the discretised EHL model by scaling and reusing it across different contact conditions. Coupling of the contact force resulting from the EHL model with the rigid body displacement resulting from the FMB model enables the computation of steady-state equilibrium for a given torque applied to the gear pair. However, local deformations should be excluded from the FMB model to ensure proper coupling with the EHL model, which exclusively computes local deformation within the contact zone. Newly developed global line contact attachment modes allow the FMB model to exclusively calculate global tooth bending in response to a given contact force."
"System identification and force estimation of robotic manipulator using semirecursive multibody formulation" "Frank Naets"
"Dimensional reduction technique for the prediction of global and local responses of unidirectional composite with matrix nonlinearity and varying fiber packing geometry" "Frank Naets"
"Using high sensitivity DC accelerometers for torque estimation on a wind turbine gearbox" "Jelle Bosmans, Simone Gallas, Matteo Kirchner, Frank Naets" "In this paper we propose a novel approach to estimate the torque on a wind turbine gearbox using single-axis high sensitivity DC accelerometers. The torque estimator uses an Augmented Extended Kalman Filter (AEKF), combining physics-based models with measurement data. The accelerometer sensor model is derived by analysing the measurements, leading to the identification of two torque-driven acceleration contributions: acceleration due to force excitation and acceleration due to a change in measurement direction. For the latter, two different sources, with distinct frequency content, are capable of changing the measurement direction. The first source corresponds to rigid body motion (f < 0.15Hz), the second one to ring gear deformation (0.15 < f < 4Hz). Using this information, the measured signal can be filtered to target specific acceleration contributions. The first torque estimation approach targets frequencies from 0.15 to 4Hz and produces a Normalised Mean Absolute Error (NMAE) of 2.12%. The second approach targets frequencies up to 0.15Hz, and will estimate the rigid body deflection angle. The torque is calculated through a linear identified relation between the rigid body angle and applied input torque. This approach yields an NMAE of 2.59%. This leads to the conclusion that high sensitivity DC accelerometers are a valid option for estimating torque on a wind turbine gearbox. These torque monitoring approaches will pave the way for advanced condition monitoring strategies and the calculation of remaining useful lifetime of the gearbox."
"Guided optimization: a fast model-based nested cost optimization technique for existing product family designs" "Emin Oguz Inci, Martijn Vermaut, Frank Naets" "Cutting production costs is a crucial instrument for companies to increase profitability and remain competitive. However, companies aim to cut costs without compromising performance requirements of the products. Commonality between components reduces the costs, while diversity between them differentiates the key attributes of the products in a product family. This commonality-diversity trade-off is the essence of the product family design optimization. Current model-based methodologies consider optimizing the design for commonality rather than cost. This article proves that higher commonality does not always amount to minimal cost and, therefore, a simple commonality index cannot replace a cost model. A tunable cost model that includes simplified formulas for standardization benefits is introduced to be used by cost optimization techniques. Current product family optimization methods are often combinatorial and perform inefficiently due to searching large design space. These methods also optimize the product family design from scratch. This limits the applicability of the current methods in industrial settings that are typically complex and brownfield. This article proposes a model-based cost optimization methodology that accelerates the cost optimization by starting from an existing design. The proposed methodology is a two-stage nested optimization algorithm, in which the commonality matrix is optimized with sensitivity analysis on component types in the outer loop and the associated design variables are optimized in the inner loop. The methodology is numerically demonstrated on an industrial example and benchmarked against state-of-the-art cost optimization methods. The proposed methodology ensures a gradual improvement in cost reduction with a significant acceleration in performance."
"Product family design optimization considering manufacturing and assembly process costs" "Hendrik Devriendt, Frank Naets"
"Substructuring-based parametric reduced-order modelling for structural dynamic predictions of bolted assemblies" "Shuyang Zhang, Hendrik Devriendt, Lucas Van Belle, Wim Desmet"
"Framework for metamodel-based design optimization considering product performance and assembly process complexity" "Hendrik Devriendt, Frank Naets" "This paper proposes a method for simultaneous evaluation of the assembly process complexity together with the performance of the future product. It allows for product design optimization, considering different aspects of the future design at the early stage of the development process. The proposed method, embodied in a fully automated framework, substitutes the traditional sequential development process with a more efficient and rapid combined procedure, which addresses multiple design aspects simultaneously. Design for assembly (DFA) rules, used as quantitative metrics of the ease-of-assembly of the whole product and individual assembly operations, are automatically evaluated together with performance metrics, estimated based on finite element (FE) simulations. The direct solution to this optimization problem might be inefficient or impossible since it requires the recurrent evaluation of computationally expensive discrete and continuous functions with unknown behavior that represent the optimization objectives and constraints. For that reason, the proposed framework employs regression models based on the Gaussian process and artificial neural networks, thus achieving the optimal design of a product as a result of metamodel-based design optimization (MBDO). The suggested approach is demonstrated in the optimization of a gearbox assembly, considering its mechanical performance and assembly process. Comparing the results of the metamodel-based and direct design optimization shows that MBDO allows finding a better solution using a three times smaller computational budget. In addition, analysis of the results obtained using stationary sampling data sets of different sizes highlighted the limitations of the employed sampling procedure."
"Inertial parameter identification for closed-loop mechanisms: Adaptation of linear regression for coordinate partitioning" "Frank Naets"