Biaosong Chen

A Novel Fast Model Predictive Control for Large-Scale Structures

To protect the engineering structures from natural hazards, especially for large-scale structures, a novel fast model predictive control (NFMPC) method is presented in this paper. Based on the second-order dynamic equation, a novel explicit expression form of Newmark-β method is first derived, from which the future states can be easily predicted without computing matrix exponential. By applying this explicit expression form into the standard model predictive control (MPC) method, the NFMPC method is developed. Based on the explicit expression form, the optimal control input can be computed by two off-line transient analyses and one on-line transient analysis at every sampling instant on the structure. For no computation of matrix exponential, the off-line computation efficiency of NFMPC is several orders of magnitude higher than that of MPC. And the small amount of on-line computation guarantees the on-line computation efficiency. Furthermore, the use of the Newmark-β method also guarantees the computation accuracy. At last, several typical numerical examples are carried out to verify the validity and high efficiency of NFMPC by the comparison with MPC.

Some Advances in Mathematical Programming Method for Numerical Simulation of Contact Problems

This paper reviews some advances and applications in mathematical programming method for numerical modeling of elastic-plastic contact problems. Emphases are on the parametric variational principle and quadratic programming method used for analysis of elastic-plastic contact problems with isotropic/orthotropic friction law. The contact problem with friction between two elastic-plastic Cosserat bodies is treated in the same way as that in the conventional plastic analysis. There is no available rule for choosing a reasonable value of the penalty factors for simulation of the contact problems of Cosserat materials, and they are therefore cancelled through a special technique so that the numerical results can be of high accuracy. Two numerical examples are presented to show the efficiency of the model and algorithm presented.

Explicit expression-based practical model predictive control implementation for large-scale structures with multi-input delays

In this paper, two practical model predictive control (MPC) implementation algorithms with multi-input delay (NFMPCMID1 and NFMPCMID2) are developed in discrete-time formulation for vibration control of large-scale structures. By introducing a particular augmented state vector, the controlled dynamic equation with multi-input delay is transformed into the standard form without any explicit time delay. Because of no approximation for multi-input delay involved, the system performance and stability are easily guaranteed. In order to solve the computation efficiency and memory requirement for large-scale structure, a novel explicit expression form of Newmark-β method is derived, from which the future states can be easily predicted without computing matrix exponential and its integration. By applying this explicit expression form into MPC, the control input of NFMPCMID1 method can be computed by some matrix–matrix multiplications, and also the control input of NFMPCMID2 method can be computed just by two off-line transient analyses and one on-line transient analysis at every sampling instant on the structure. For no computation of matrix exponential and its integration in NFMPCMID1 and NFMPCMID2 methods, the off-line computation efficiency is greatly improved, and the memory requirement is greatly reduced, especially for the NFMPCMID2 method. In additional, due to the small amount of on-line computation, the on-line computation efficiency is also guaranteed. At last, the stability, feasibility and efficiency of the proposed methods are verified by several typical numerical examples.

Dehydration of core/shell fruits

Dehydrated core/shell fruits, such as jujubes, raisins and plums, show very complex buckles and wrinkles on their exocarp. It is a challenging task to model such complicated patterns and their evolution in a virtual environment even for professional animators. This paper presents a unified physically-based approach to simulate the morphological transformation for the core/shell fruits in the dehydration process. A finite element method (FEM), which is based on the multiplicative decomposition of the deformation gradient into an elastic part and a dehydrated part, is adopted to model the morphological evolution. In the method, the dehydration pattern can be conveniently controlled through physically prescribed parameters according to the geometry and material of the real fruits. The effects of the parameters on the final dehydrated surface patterns are investigated and summarized in detail. Experiments on jujubes, wolfberries, raisins and plums are given, which demonstrate the efficacy of the method. Display Omitted A unified physically-based approach for modeling the deformation in a general dehydration process.A nonlinear finite element method to simulate the dehydration-induced morphological transformation.Simple parameters based on the geometry and material of the fruits to control the evolution of surface patterns.A looking-up table for efficient simulation.

Multilevel Adaptive Algorithm for Multiscale Analysis of Heterogeneous Materials

AbstractA multilevel adaptive FEM is proposed for multiscale mechanical analysis of heterogeneous materials. The algorithm is developed based on the extended multiscale FEM (EMSFEM), which has been proven to be an efficient method for multiscale mechanical analysis. A residual force-based error estimate is introduced, which is able to detect both global and local errors economically. The concept of microscopic numerical base function (NBF) is introduced, which can be used to refine the local results at the regions with a high-stress gradient level by level. Two efficient methods for updating the microscopic NBFs were developed, i.e., the hierarchical NBFs scheme and the residual force NBFs scheme. A hierarchical linear solver is designed to solve the multilevel equation system in each iteration step. In the algorithm, the calculations at the current iteration step take full advantage of the results of previous iteration steps, which is helpful to save computational resources. The numerical examples demons...