Estimation of continuous-time linear system parameters from periodic data

The parameters of a continuous-time linear system are identified by use of integral functions satisfying periodicity conditions. Explicit equations are derived for the evaluation of integral functions in terms of measured periodic output data. It is shown that a Walsh function representation of the integral functions has modest computational requirements making implementation on a 16-bit microprocessor feasible. Simulation and experimental results are provided to illustrate truncation error, estimation accuracies, and output response errors.     

Heavy vehicle suspension parameters identification and estimation of vertical forces: experimental results

The aim of the present work is to estimate the vertical forces of heavy vehicle and identify the unknown dynamic parameters using sliding mode observer approach. This observation needs a good knowledge of dynamic parameters such as damping coefficient, spring stiffness, etc. In this paper, suspension stiffness and unsprung masses have been identified. Experimental results carried out on an instrumented tractor have been presented in order to show the quality of the state observation, parameters identification and force estimation. These estimation results are then compared to the measured one coming from the sensors installed in the tractor. Many scenarios have been tested. In this paper, the results coming from zigzag test have been shown and commented.     

Analysis of the biomechanical behaviour of gastrointestinal regions adopting an experimental and computational approach

An integrated experimental and computational procedure is provided for the evaluation of the biomechanical behaviour that characterizes the pressure–volume response of gastrointestinal regions. The experimental activity pertains to inflation tests performed on specific gastrointestinal conduct segments. Different inflation processes are performed according to progressively increasing volumes. Each inflation test is performed by a rapid liquid in-flaw, up to a prescribed volume, which is held constant for about 300 s to allow the development of relaxation processes. The different tests are interspersed by 600 s of rest to allow the recovery of the specimen mechanical condition. A physio-mechanical model is developed to interpret both the elastic behaviour of the sample, as the pressure–volume trend during the rapid liquid in-flaw, and the time-dependent response, as the pressure drop during the relaxation processes. The minimization of discrepancy between experimental data and model results entails the identification of the parameters that characterize the viscoelastic model adopted for the definition of the behaviour of the gastrointestinal regions. The reliability of the procedure is assessed by the characterization of the response of samples from rat small intestine.     

Concurrent manufacturing of parts and tools for the sheet-metal industry

The manufacturing of complex bent parts can be supported effectively by computer-aided planning methods. Software systems are already available for unfolding, laser cutting and bending sequence determination. The paper focuses on methods that support the design of non-standard bending tools and the flexible manufacturing of such tools using laminated object modelling (LOM) technology. The developed system allows for concurrent planning and manufacturing of bending parts and tools. Within the framework of this system, neural networks are applied for automated tool design.     

Particle swarm approaches using Lozi map chaotic sequences to fuzzy modelling of an experimental thermal-vacuum system

Particle Swarm Optimization (PSO) approach intertwined with Lozi map chaotic sequences to obtain Takagi–Sugeno (TS) fuzzy model for representing dynamical behaviours are proposed in this paper. The proposed method is an alternative for nonlinear identification approaches especially when dealing with complex systems that cannot always be modelled using first principles to determine their dynamical behaviour. Since modelling nonlinear systems is normally a difficult task, fuzzy models have been employed in many identification problems due its inherent nonlinear characteristics and simple structure, as well. This proposed chaotic PSO (CPSO) approach is employed here for optimizing the premise part of the IF–THEN rules of TS fuzzy model; for the consequent part, least mean squares technique is used. The proposed method is utilized in an experimental application; a thermal-vacuum system which is employed for space environmental emulation and satellite qualification. Results obtained with a variety of CPSO's are compared with traditional PSO approach. Numerical results indicate that the chaotic PSO approach succeeded in eliciting a TS fuzzy model for this nonlinear and time-delay application.     

Estimation of parameters in fractional subdiffusion equations by the time integral characteristics method

This paper presents an extension to the time integral characteristics method for estimation of parameters in fractional subdiffusion equations containing Riemann-Liouville and Caputo fractional time derivatives. The explicit representations of the fractional diffusion coefficient and order of fractional differentiation via a Laplace transform of the concentration field are obtained. A technique of optimal Laplace parameter determination by minimization of relative errors bounds is described. The effectivity of the proposed approach is illustrated by numerical example.     

Using coarse remote sensing radar observations to control the trajectory of a simple Sahelian land surface model

In the Sahel, land surface processes are significantly interacting with climate dynamics. In this paper, we present an original method to control a simple Sahelian land surface model coupled to a radiative transfer model (RTM) on the basis of ERS wind scatterometer (WSC) observations. In a first step, a sensitivity study is implemented to identify those parameters of the land surface model that can be estimated through the assimilation of WSC data. The assimilation scheme relies on evolution strategies (ES) algorithm that aims at solving the parameter evaluation problem. These algorithms are particularly well suited for complex (nonlinear) inverse problems. The assimilation scheme is applied to several study sites located in the Sahelian mesoscale site of the African Monsoon Multidisciplinary Analysis Project (Gourma region, Mali). The results are compared with ground observations of herbaceous mass. After the WSC data assimilation, the simulated herbaceous mass curves compare well with observations [187 kilogram of dry matter per hectare (kg DM/ha) of average error]. The simulated water fluxes exhibit a behaviour in agreement with ground measurements performed over similar ecosystems during the Hapex Sahel experiment. The accuracy of estimated herbaceous mass and water fluxes resulting from uncertainties on climatic forcing variable is evaluated using a stochastic approach. The average error on the herbaceous mass values mainly depends on the rainfall estimate accuracy and ranges from 139 to 268 kg DM/ha that compares well with a previous study based on the sole inversion of the radiative transfer model. Finally, this study underlines the need for a multispectral assimilation approach to get a better constraint on water fluxes estimation.     

On the existence of a global minimum in inverse parameters identification by Self-Optimizing inverse analysis method

In this paper, a mathematical proof of the existence of a global minimum of Self-Optim (Self-Optimizing Inverse Analysis Method) cost functional is presented based upon weak-solution theory of partial differential equations. The Self-Optim provides single global minimum rather than having multiple global minima corresponding to unrealistic solutions of the inverse problem. Furthermore, discrete approximation of the inverse problem and computational methods for the cost functional are proposed and the proof is numerically verified. This paper provides a rigorous mathematical foundation for applications of the Self-Optim method to various inverse problems in mechanics.     

System identification of the upper part of Murray River

Data based modelling is an important tool for obtaining models of rivers. In this paper we consider several identification methods, namely Prediction Error Method, Maximum Likelihood, continuous time system identification, Refined Instrumental Variable method (used within the context of Data-Based Mechanistic modelling) and Subspace Identification Method, and apply them to real data from the Murray River in Australia. Both Multiple-Input Single-Output models where the output is the water level in a lake and Multiple-Input, Multiple-Output models where in addition a flow is also modelled, are considered. The models are compared in terms of their accuracy on validation data and on how easily the methods can incorporate prior knowledge.     

进化粒子群优化算法及其在各向异性含水层参数估计中的应用

在粒子群算法的基础上,引入进化思想和组群思想提出一种新的智能优化算法———进化粒子群算法( EPSO)。基于抽水试验数据,将EPSO算法应用到各向异性含水层参数估计中,对算法性能进行研究并与其他算法进行了对比,发现标准粒子群算法及其一般改进算法已不能有效求解各向异性含水层参数,而EPSO算法进行多次计算后,1)结果可靠;2)目标函数值及待估参数稳定;3)对初始范围的鲁棒性好。结果表明EPSO算法对各向异性含水层参数估计问题具有可靠性、收敛性和鲁棒性,可望应用到更广泛的参数识别问题中。     

A least squares method in back fitting the data base of a simulation model

This article presents an application of the least squares method in a particular class of inverse problems. Knowing the solution from experimental measurements, what are the corrections we must apply to the data of the problem in order to make the result close as much as possible to it? Normally the data of the problem are state functions known with a given degree of precision and in solving this problem the precision can be enhanced. This kind of problem is felt in many fields of engineering and physics, where an adjustment of a mathematical model on experimental observation is needed. This article shows a method to determine some residual function to be added to the data in order to refine the predictive power of the numerical model. An example is shown in a simple but concrete application.     

An optimisation approach to the recovery of reflection parameters from a single hyperspectral image

In this paper, we present a method to recover the parameters governing the reflection of light from a surface making use of a single hyperspectral image. To do this, we view the image radiance as a combination of specular and diffuse reflection components and present a cost functional which can be used for purposes of iterative least squares optimisation. This optimisation process is quite general in nature and can be applied to a number of reflectance models widely used in the computer vision and graphics communities. We elaborate on the use of these models in our optimisation process and provide a variant of the Beckmann–Kirchhoff model which incorporates the Fresnel reflection term. We show results on synthetic images and illustrate how the recovered photometric parameters can be employed for skin recognition in real world imagery, where our estimated albedo yields a classification rate of 95.09 ± 4.26% as compared to an alternative, whose classification rate is of 90.94 ± 6.12%. We also show quantitative results on the estimation of the index of refraction, where our method delivers an average per-pixel angular error of 0.15°. This is a considerable improvement with respect to an alternative, which yields an error of 9.9°.     

在Maple平台上应用最小二乘法估算动力学参数

以大量实验数据为基础在Maple平台上运用最小二乘法,估算了气相苯加氢反应中反应速率常数及苯的吸附平衡常数,结果较为满意;并且估算了CO与Cl_2在活性炭表面上催化合成光气的反应中动力学的最优参数,计算值与实验值的最大相对误差不超过5%;最后推算了NO与H_2反应的反应速度方程式,计算值与文献值很相似。应用这种方法既克服手工计算的繁琐、工作量大的缺点,还能提高计算的精度,大大地方便了化学反应速率式的确定。     

Using Influence Diagrams to Aid the Management of Software Change

In a large software management programme, the number of software changes and enhancements requested for inclusion in the next software release often far exceeds the implementation resources available. Thus, during the preceding months before the final decision is made on which changes to include, there needs to be a way of incorporating all the different factors that influence these possible changes into a coherent set of information to enable good decisions to be made. This paper describes the use of influence diagrams to implement a risk model to formalise the combining of these different factors to aid the decision process. This model not only reflects the likelihood of all the necessary criteria for a requested change to be viable being met, but also considers the financial or other benefits to the organisation that would result from the change being included in the next software release.     

Homology modelling,docking, pharmacophore and site directed mutagenesis analysis to identify the critical amino acid residue of PknI from Mycobacterium tuberculosis

Tuberculosis is caused by Mycobacterium tuberculosis, an intracellular pathogen. PknI is one of the 11 functional Serine/Threonine Protein Kinases which is predicted to regulate the cell division of M. tuberculosis. In order to find newer drugs and vaccine we need to understand the pathogenesis of the disease. We have used the bioinformatics approach to identify the functionally active residues of PknI and to confirm the same with wet lab experiments. In the current study, we have created homology model for PknI and have done comparative structural analysis of PknI with other kinases. Molecular docking studies were done with a library of kinase inhibitors and T95 was found as the potent inhibitor for PknI. Based on structure based pharmacophore analysis of kinase substrate complexes, Lys 41 along with Asp90, Val92 and Asp96 were identified as functionally important residues. Further, we used site directed mutagenesis technique to mutate Lys 41 to Met resulting in defective cell division of Mycobacterium smegmatis mc². Overall, the proposed model together with its binding features gained from pharmacophore docking studies helped in identifying ligand inhibitor specific to PknI which was confirmed by laboratory experiments.     

Tomographic inversion of ocean bottom seismograph (OBS) data: Problems and solutions applied to the NW Svalbard Hydratech data set

The paper is aimed at discussing some problems that may arise in the tomographic inversion of data acquired with particular geometries, as vertical seismic profiles (VSP) or implying the use of Ocean Bottom Seismographs (OBS), and presenting the solutions used to solve them. One problem is due to the limited number of sensors (that may be even a single one) and of their sparseness. This affects the information distribution that is concentrated in the vicinity of each sensor. This fact, together with the second problem, i.e. the strong asymmetry of the ray path, may decrease the reliability of the inversion.Two procedures for irregular adaptive gridding of the reflecting interfaces and single ray datuming are proposed as possible solutions to overcome these obstacles, while obtaining a reliable and highly resolved velocity model in depth: the relative procedures are tested through synthetic models and on real data.     

背衬对埋入混凝土中压电陶瓷电-声特性的影响

传统超声脉冲法不能对混凝土质量进行实时健康监测,将压电陶瓷埋入混凝土中构成的压电埋入式混凝土机敏模块能够进行混凝土结构的在线监测,但由于压电陶瓷在埋人混凝土后其电-声性能受到较大影响,能够激励的声信号能量弱、信噪比低,很难应用于噪声干扰强、待检测结构厚的场合.针对这一问题,提出了通过在埋入混凝土中的压电陶瓷上层合金属背衬的方法,提高声能的利用率和指向性.分析了在不同背衬厚度和不同激励频率条件下接收信号的时、频域特征.结果表明,经过层合金属背衬处理后的超声信号的能量提高了2～6倍,且这种方法并没有影响超声检测信号的波形及频率成分,具有较高的可行性.     

Off-line compensation of the tool path deviations on robotic machining: Application to incremental sheet forming

In this paper, a coupling methodology is involved and improved to correct the tool path deviations induced by the compliance of industrial robots during an incremental sheet forming task. For that purpose, a robust and systematic method is first proposed to derive the elastic model of their structure and an efficient FE simulation of the process is then used to predict accurately the forming forces. Their values are then defined as the inputs of the proposed elastic model to calculate the robot TCP pose errors induced by the elastic deformations. This avoids thus a first step of measurement of the forces required to form a test part with a stiff machine. An intensive experimental investigation is performed by forming a classical frustum cone and a non-symmetrical twisted pyramid. It validates the robustness of both the FE analysis and the proposed elastic modeling allowing the final geometry of the formed parts to converge towards their nominal specifications in a context of prototyping applications.