26,868 research outputs found
A geometrical non-linear model for cable systems analysis
Cable structures are commonly studied with simplified analytical equations. The evaluation of the accuracy of these equations, in terms of equilibrium geometry configuration and stress distribution was performed for standard cables examples. A three-dimensional finite element analysis (hereafter FEA) procedure based on geometry-dependent stiffness coefficients was developed. The FEA follows a classical procedure in finite element programs, which uses an iterative algorithm, in terms of displacements. The theory is based on a total Lagrange formulation using Green-Lagrange strain. Pure Newton-Raphson procedure was employed to solve the non-linear equations. The results show that the rigid character of the catenary’s analytical equation, introduce errors when compared with the FEA
Non-linear model-predictive-control for thermomechanical ring rolling
he authors present a new ring rolling variant that combines a semi-warm forming process of a bearing ring with controlled cooling directly followed by a cold forming process. The aim is to produce near net shape rings with a selected microstructure and high strength without additional consecutive heat treatment. To achieve this, a new and fast control strategy is necessary that not only controls the geometrical forming of the ring, but also considers temperature development and microstructure formation. The proposed control strategy is based on the application of a fast semi-analytical simulation model with a very short response time in combination with a FE-analysis of the thermomechanical ring rolling process. The semianalytical model is used as a predictor and a parallel FEA or experimental results as a corrector for the control model. The aim is to correctly identify transient process parameters needed to achieve defined product properties as a basis for a later implementation in a non-linear modelpredictive-control of thermomechanical ring rolling. The new approach will be described in detail and demonstrated numerically and experimentally
Non-Linear Model Predictive Control with Adaptive Time-Mesh Refinement
In this paper, we present a novel solution for real-time, Non-Linear Model
Predictive Control (NMPC) exploiting a time-mesh refinement strategy. The
proposed controller formulates the Optimal Control Problem (OCP) in terms of
flat outputs over an adaptive lattice. In common approximated OCP solutions,
the number of discretization points composing the lattice represents a critical
upper bound for real-time applications. The proposed NMPC-based technique
refines the initially uniform time horizon by adding time steps with a sampling
criterion that aims to reduce the discretization error. This enables a higher
accuracy in the initial part of the receding horizon, which is more relevant to
NMPC, while keeping bounded the number of discretization points. By combining
this feature with an efficient Least Square formulation, our solver is also
extremely time-efficient, generating trajectories of multiple seconds within
only a few milliseconds. The performance of the proposed approach has been
validated in a high fidelity simulation environment, by using an UAV platform.
We also released our implementation as open source C++ code.Comment: In: 2018 IEEE International Conference on Simulation, Modeling, and
Programming for Autonomous Robots (SIMPAR 2018
SEQUENTIAL NON-LINEAR MODEL UPDATING
The Ensemble Kalman Filter (EnKF) has become a popular method in reservoir modeling.
Several publications have demonstrated the use of EnKF, and suggested further developments of the
method. In this paper, a constant flow rate no flow bounded reservoir is used to explore the
applicabity of EnKF. The reservoir modeling and the solution will be discussed and play a role as
reservoir simulator. The sequential updating will be discussed and implemented in reservoir modeling.
The conclusion is that EnKF can provide satisfactory results compared with traditional reservoir
simulation updating method
A non linear model of the new economic geography for Portugal
With this work we try to present a non linear model for Portugal based on the new economic geography. We built the model taking into account an analyse about the agglomeration process in Portugal, using the New Economic Geography models, in a non linear way . In a non linear way, of referring, as summary conclusion, that with this work the existence of increasing returns to scale and low transport cost, in the Portuguese regions, was proven and, because this, the existence of agglomeration in Portugal.new economic geography; non linear models; Portuguese regions
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