Application of the digital signal processing methodology (DSPM) for the design of time integration formulae

Although the existence of a close relationship between the areas of digital processing and time integration methodology has been established long ago, only recently a systematic application of the concepts and methods of the first area to the second has been attempted. The resulting Digital Signal Processing Methodology is applied in this paper to demostrate that time integration methods can be designed, displaying advanced performance in the computational analysis of large complex systems, with respect to accuracy, spurious oscillations damping, overshooting and asymptotic behavior for singular cases.     

An incremental finite element analysis of mechanisms and robots

In this paper, we present an incremental finite element method of analysis of mechanisms/robots. Our method is based on the idea to decompose any large displacement of a mechanism or robot arm in a series of successive small displacements, so small that the linear finite element method can be applied in their analysis between two successive positions. Evidently, at the end of any small displacement, the position of a deformed member of the mechanism gives us the initial conditions for the following small displacement. After presentation of all the theoretical background of the method, we illustrate it by application to the crank-slider mechanism and to the four-bar-linkage mechanism.     

Further research on the performance of consistent mass matrices using BEM for symmetric/nonsymmetric formulations

This paper deals with the performance of consistent mass matrices for the 2-D scalar wave propagation problem using the Boundary Element Method (BEM), and proposes a new global functional set of base functions capable of avoiding domain integrations, suitable for symmetric and nonsymmetric formulations. The method can be applied to arbitrary shaped two-dimensional domains divided into triangular, rectangular and arbitrary shaped quadrilateral linear or curvilinear (e.g. circular) internal cells. The theory is sustained by numerical results for a rectangular and a circular acoustical cavity under Neumann and Dirichlet boundary conditions.     

Application of N‐step‐ahead NeuroControl on articulated manipulators

The N‐step‐ahead control method, called chain‐back‐propagation, is applied to articulated manipulators. The method is based on a pair of neural networks—the neural controller and the neural emulator—and focuses mainly in the appropriate design of the various global and chain‐local penalty functions and the convergence control limitations, needed for the on‐line training of the controller. No reference models or paths are needed for the implementation of the method, only set‐points. The results, compared to conventional proportional‐derivative (PD) control and to traditional one‐step‐ahead neural control, are quite satisfactory, indicating improved accuracy, faster response, and greater overall efficiency. © 2000 John Wiley & Sons, Inc.     

Crypto-DOF finite elements

New finite elements, called crypto-DOF elements, are introduced, utilizing degrees of freedom that satisfy the differential equation but do not appear explicitly in the discrete equations. The crypto-DOF elements can be advantageous in adaptive finite element techniques, and to approximate singular-type eigensolutions (e.g. in convective diffusion or stress concentration problems) without altering the original mesh or introducing new degrees of freedom. In this paper the crypto-DOF elements, the construction of crypto-DOF element families and selected numerical results are presented.     

Tire lateral force estimation and grip potential identification using Neural Networks,Extended Kalman Filter,and Recursive Least Squares

This paper presents a novel hybrid observer structure to estimate the lateral tire forces and road grip potential without using any tire–road friction model. The observer consists of an Extended Kalman Filter structure, which incorporates the available prior knowledge about the vehicle dynamics, a feedforward Neural Network structure, which is used to estimate the highly nonlinear tire behavior, and a Recursive Least Squares block, which predicts the road grip potential. The proposed observer was evaluated under a wide range of aggressive maneuvers and different road grip conditions using a validated vehicle model, validated tire model, and sensor models in the simulation environment IPG CarMaker ^®. The results confirm its good and robust performance.

     

Review of topology optimisation refinement processes for sheet metal manufacturing in the automotive industry

Design can be viewed a sequential decision process that increases the detail of modeling and analysis while simultaneously decreasing the space of alternatives considered. In a decision theoretic framework, low-fidelity models help decision-makers identify regions of feasibility and interest in the tradespace and cull others prior to constructing more computationally expensive models of higher fidelity. The method presented herein demonstrates design as a sequence of finite decision epochs through a search space defined by the extent of the set of designs under consideration, and the level of analytic fidelity subjected to each design. Previous work has shown that multi-fidelity modeling can aid in rapid optimization of the design space when high-fidelity models are coupled with low-fidelity models. This paper offers two contributions to the design community: (1) a model of design as a sequential decision process of refinement using progressively more accurate and expensive models, and (2) a connected approach for how conceptual models couple with detailed models. Formal definitions of the process are provided, and several structural design examples are presented to demonstrate the use of sequential multi-fidelity modeling in determining an optimal modeling selection policy.     

A Galerkin method for the steady state analysis of harmonically excited non-linear systems

A Galerkin method for the computation of the steady state of harmonically excited non-linear systems in the frequency domain is presented. The non-linear differential equations of motion are transformed, via the Galerkin technique, to a minimized system of non-linear algebraic equations in the frequency domain. These equations are then solved by a specially developed iteration procedure based on Powell's minimization method. The solution technique proves to be suitable for non-linear systems with arbitrary and numerous non-linearities (e.g. joints with clearance, non-linear springs and dampers).     

Static analysis of thin-walled structures using polynomial and exact solutions. Application to thin-walled pipes

A new finite element procedure for the static analysis of beam thin-walled structures of open or closed cross-section is presented. The method is a combined or mixed one, based on the superposition of beam and shell strains and displacements. An essential part of this work is the development of new shape functions (which are either ‘exact’, or polynomial) for the interpolation of the shell displacements.The above method is applied to the thin-walled curved pipe problem and compared to the von Karman approach. Excellent results are obtained, as well as a drastic reduction of the total number of nodal variables.     

Analysis of 2D flexible mechanisms using linear finite elements and incremental techniques

In this paper, a fully linear method for the kinetoelastodynamic analysis of mechanisms of engineering praxis, characterized by large displacements and rotations (rigid body motion) but small elastic displacements and strains, based on the standard Euler–Bernoulli finite elements is proposed and investigated. The method is a co-rotational approach and relies on the principle to decompose the motion of a mechanism in a series of successive time steps, so small that the linear finite element method can be applied within each step, adding a correction procedure in order to compensate errors resulting from not incorporating the exact (non-linear) beam theory. After presentation of the method, we apply it to test cases well known in the literature and discuss its characteristics.