A robust component mode synthesis method for stochastic damped vibroacoustics

In order to reduce vibrations or sound levels in industrial vibroacoustic problems, the low-cost and efficient way consists in introducing visco- and poro-elastic materials either on the structure or on cavity walls. Depending on the frequency range of interest, several numerical approaches can be used to estimate the behavior of the coupled problem. In the context of low frequency applications related to acoustic cavities with surrounding vibrating structures, the finite elements method (FEM) is one of the most efficient techniques. Nevertheless, industrial problems lead to large FE models which are time-consuming in updating or optimization processes. A classical way to reduce calculation time is the component mode synthesis (CMS) method, whose classical formulation is not always efficient to predict dynamical behavior of structures including visco-elastic and/or poro-elastic patches. Then, to ensure an efficient prediction, the fluid and structural bases used for the model reduction need to be updated as a result of changes in a parametric optimization procedure. For complex models, this leads to prohibitive numerical costs in the optimization phase or for management and propagation of uncertainties in the stochastic vibroacoustic problem. In this paper, the formulation of an alternative CMS method is proposed and compared to classical (u,p) CMS method: the Ritz basis is completed with static residuals associated to visco-elastic and poro-elastic behaviors. This basis is also enriched by the static response of residual forces due to structural modifications, resulting in a so-called robust basis, also adapted to Monte Carlo simulations for uncertainties propagation using reduced models.     

Robustness analysis by a probabilistic approach for propagation of uncertainties in a component mode synthesis context

Modelling uncertainties in an industrial application require a thorough knowledge of their sources and types. Uncertainties can be split into aleatory and epistemic types. Using parametric and non-parametric methods successively can be an adapted approach to model these uncertainties types on a given finite elements model (FEM). However, we propose in this paper to proceed more appropriately by introducing a hybrid approach combining the parametric and non-parametric methods. This approach consists of applying, on a given FEM, parametric and non-parametric methods simultaneously with respect to uncertainties types of each model region. Complexity and size of industrial FEMs often impose model reductions. This introduces necessarily the problem of reduction basis robustness. We are interested in the effectiveness of two methods for model reduction in the case of a hybrid model of uncertainties. We consider the case of component mode synthesis (CMS) based on normal modes of clamped interfaces components. Therefore, we analyze robustness of two methods based on improved Craig-Bampton's basis: the first one is enriched by static residual vectors (ESRV), the second one is a variant of the combined approximations method (VCA) adapted to CMS. Finally, a dynamic application on a railway electric motor stator, allows comparing methods' performances in terms of robustness and gain in computing time. Conclusion highlights relevance of the combined approximations method when using a hybrid approach for modelling uncertainties.     

A non-parametric approach for linear system identification using principal component analysis

This paper considers the applications of principal component analysis (PCA) for signal-based linear system identification. Linear time-invariant (LTI) single-input-single-output (SISO) and multi-input-multi-output (MIMO) system frequency response function (FRF) estimation problems are formulated on the basis of the eigen-value decomposition (EVD) of the input–output measurement spectral correlation matrix. It is demonstrated that resulting algorithms for the SISO and MIMO cases are equivalent to that of the maximum likelihood (ML) and the total least squares (TLS) approaches respectively. Originating from the proposed FRF estimation scheme, a moving-segment EVD procedure is developed for SISO time-varying transfer function estimation. Based on the sensitivity of the time-domain PCA to delays/shifts between signals, an extended lagged-covariance-matrix approach is introduced for delay detection from time series.     

双边遥操作系统二阶滑模控制器设计

一阶滑模控制方法由于需要大的带宽和高频切换信号,以及处理系统的参数不确定和强非线性,在双边遥操作的工程应用中难以推广。针对上述问题,将二阶滑模控制和阻抗控制联合起来,设计了大时延下的控制结构,并利用全维状态观测器对主从手机械臂的加速度、速度进行了观测,实现了双边遥操作系统的鲁棒平滑控制;在此基础上,分析了加入观测器后整个系统的闭环稳定性,给出了稳定性定理,并用李雅普诺夫函数方法进行了证明;最后分两种时延情况对闭环系统进行了仿真。实验结果表明,该方法可以使系统具有了较好的稳定性能。     

A functional approach for standard component reuse

This paper proposes a novel approach for standard component reuse in die design. In this approach, a standard component, or a subassembly of standard components, is represented by a unique name called the order name. The order name is derived by combining a manufacturer or supplier's name with the catalogue name used for ordering components from the supplier. In this system, the standard components are classified according to their generic information, i.e. their functions and the geometrical characteristics of their mating relationships with other components. When a user designs a particular die structure for a certain function, some design options and requirements are inputted. Using this information, the generic information of the standard component is derived and the order name is selected. The rules required for the selection procedures are stored in a knowledge-base shell. The shell is able to search data tables and retrieve parameters regarding the standard components. In this approach, the catalogue data and selection procedure are independent of the design system. It is concise and consistent with industry practice.     

A new approach for molding multi component parts

Injection molding has gained an enormous importance over the last twenty years. This is due both to the development of sophisticated products and to the efforts being generally made to the reduction of product weight specially in automobile industry. Developments aimed at creating innovative products are expected to broaden industrial implementation of their techniques. Establishment then requires the progressive development of existing mold techniques and engineering knowledge. This paper describes a successive process for molding multi component complicated products such as door trim, instrument panel and so on. Using an analytical model, the orthogonal experiment method (Taguchi method) and numerical simulation, an optimal process for simultaneous injection molding with “core-back” and “co-injection” technique is presented to produce such innovative products. Through practical tests, this process was verified in terms of applicability.     

A systematic approach to synthesis of a drive system

The problem of synthesis of a drive system consisting of a motor, a mechanism of motion translation, and a controlling system is discussed. A systematized procedure for determining rational parameters of drive systems based on the hierarchy of closed dimensionless mathematical models is suggested. From step to step, the precision of the model gradually increases due to the greater number of determining dimensionless factors taken into consideration.     

On a component mode synthesis on multi-level and its application to dynamics analysis of vehicle system supported with spring-stiffness damper system

The component mode synthesis (CMS) method on multi-level, called as recursive component mode synthesis (RCMS) method, is implemented for the free vibration analysis of a vehicle system supported on damper-controlled spring-stiffness suspension. The nonproportional damping is considered to describe the suspension system. The focus of the RCMS method is the out-of-core concept that uses disk space rather than memory when computing large scale vehicle FE models. After the eigensolutions are obtained, the mode superposition method is used to compute the dynamic response in the frequency domain. The proposed method can deal with a damped structural system with a general damping system. The performance and accuracy of the proposed method compared to the Lanczos method are demonstrated through an example FE model.     

晶圆制造物料运输系统性能分析建模方法

为在自动化物料搬运系统设计阶段快速有效地分析该系统的性能,提出一种扩展Markov模型的建模方法,该方法减少了自动化物料搬运系统性能分析模型的规模,避免了模型的状态空间规模爆炸.采用某晶圆制造企业的实际生产数据进行测试,并与仿真分析方法比较.结果表明,扩展Markov模型与仿真模型在自动化物料搬运系统搬运量、运输小车利用率和空载小车到达平均时间间隔等指标方面的相对误差值为96％,处于[-8％,10％]的区间范围;与仿真模型相比,扩展Markov模型的性能分析效率提高了600倍以上.由此验证了所提扩展Markov模型建模方法的有效性.     

A new history-independent modeling approach for feature-based design

The majority of current feature-based modeling systems employ model history to store feature creation operations and re-execute them sequentially after each modification, which is called history-based modeling. Due to the static feature creation order, history-based modeling causes some problems during the reevaluation of the model, such as the evaluated model does not correspond to its specification, the operation can only refer to the boundary entities created by the previous operations, high computation cost, etc. In this research work, a new history-independent modeling approach is proposed. For the “remove feature” operation, only boundary faces originating from the feature being removed, and the intersecting features are modified for updating the resulting BRep model. For the “modify feature” operation, the feature being modified is first removed from the product model and then re-added with the new specifications, thus its creation step in the model history is changed. As a result, some of the problems caused by the static feature creation order are solved. During the reevaluation, the computation time is dependent solely on the execution of the feature and its intersecting features being edited. The computational complexity of the boundary evaluation using the proposed method for three representative models has been analyzed based on Open CASCADE. A case model was studied in a proof-of-concept prototype system to demonstrate the proposed modeling approach.     

飞机液压附件综合测试系统设计

针对军用飞机修理厂对飞机液压附件修理后测试难的问题,按工厂要求设计制造了以计算机为核心的"飞机液压附件综合测试系统".该文介绍了该系统的基本组成、工作和技术特点.     

Systematic approach to realizing optimal moving order selection for multi-axis precise motion system

This paper presents a systematic approach for selecting the optimal moving order (MO) in a multi-axis precise motion system (MPMS). According to the proposed procedure, an optimal high-efficiency MO selection approach for high-efficiency and high-accuracy requirement is introduced. First, the characteristics of the giving MPMS are analysed, and the error model is established. The orthogonal test method is used to evaluate the influence on the MO caused by different MPMS configurations. Second, the number of possible MOs can be narrowed to limited and satisfied MO types. By calculating the deviations after each step, all directional movements can be arranged. Third, considering that both the accuracy and efficiency are important indexes, a series of systematic formulations are developed to select the optimal MO to balance accuracy and efficiency. A case for which a six-axis precise platform is adopted in an optoelectronic packaging system is implemented, and the methods of high-quality MO selection are verified by performing a series of experiments, and the methods are shown to be useful and effective. To balance the proportion of efficiency and accuracy, the formula and corresponding model are proposed to select the MO. The approach is not only beneficial to the accuracy improvement and trajectory planning of MPMS, but also helpful in terms of reducing the computational processing for the following algorithm. For the engineers using in precise industry area, the proposed approach can significantly improve the operative precision of MPMS with an optimal MO. This methodology of MO can also be the basis of references to error-related analyses on MPMS.     

复杂仿真系统建模与仿真可信性模糊综合评估

为保证复杂仿真系统建模与仿真可信性评估工作高效地完成,以贯穿复杂仿真系统开发全生命周期的校核与验证过程为基本框架,综合分析建模与仿真可信性评估在校核与验证过程中不同阶段的评价标准,提出可信性评估尺度,构建可信性评估指标体系;针对可信性评估所涉及的不确定性和模糊性因素,结合基于三角模糊数的模糊层次分析法和模糊综合评判建立了模糊综合评估模型,并以某飞行视景仿真系统的设计与开发为例,进行可信性模糊综合评估。应用实例表明,所建立的指标体系及采用的评估方法合理可行。     

A novel approach of fractional-order time delay system modeling based on Haar wavelet

In this paper, fractional-order time delay system modeling is presented using Haar wavelet operational matrix of integration. Therefore, it does not require any prior knowledge of transfer function structure or partial information about fractional differentiation order. It allows the estimation of the implicit time delay parameter together with other model parameters by utilizing new delay operational matrix of Haar wavelet based on Riemann-Liouville definition. The proposed technique reduces the complexity of identification by converting the complex fractional calculus equations into simple algebra. The efficacy of the approach is verified on various integer and non-integer (fractional) order systems in simulation. For realistic condition, proposed method is verified in the presence of noise in simulation and also demonstrated on the real-time process control temperature system.     

A modeling and analysis of spring-shaped torsion micromirrors for low-voltage applications

An electrostatic torsion micromirror is designed using the optimized spring-shaped torsion beams and U-shaped groove supporters. The main advantages of this design will be a reduction in the pull-in voltage for low-voltage applications and the function as a switch of the instability mode by adjusting the effective bending stiffness of the torsion beam. In this design, a theoretical model is developed to demonstrate the static characteristics of the electrostatic torsion micromirror. The pull-in effect is investigated specifically to predict the pull-in voltage, pull-in angle, and pull-in displacement. These parameters depend significantly on the electrode size and position, position of the groove, and ratio of the bending and torsion effect of the torsion beam. In addition, the effective torsion and bending stiffness model is provided using the energy method with the objectives to optimize the spring-shaped geometries of the torsion beams and to decrease the pull-in voltage below 2 V. The U-shaped groove supporters are applied in the theoretical model to adjust the effective bending stiffness of the torsion beam and to switch the instability mode of the torsion micromirror. The theoretical analysis is consistent with the numerical simulation using MEMCAD and experimental results measured by an optical projection method.     

基于自由端口通信的减震器多频试验台测控系统

分析了控制系统的程序设讦及数据通信的实现.以多频减振器试验台为应用背景,阐述了西门子S7-200 PLC与VB之间的自由端口串行通信编程原理.最终,控制系统完成了对减振器多频试验台的控制.实践证明,本测控系统工作可靠、稳定,上下位机通信数据运行良好,无错误码.     

A new continuous sliding mode control approach with actuator saturation for control of 2-DOF helicopter system

The 2-degree of freedom (DOF) helicopter system is a typical higher-order, multi-variable, nonlinear and strong coupled control system. The helicopter dynamics also includes parametric uncertainties and is subject to unknown external disturbances. Such complicated system requires designing a sophisticated control algorithm that can handle these difficulties. This paper presents a new robust control algorithm which is a combination of two continuous control techniques, composite nonlinear feedback (CNF) and super-twisting control (STC) methods. In the existing integral sliding mode (ISM) based CNF control law, the discontinuous term exhibits chattering which is not desirable for many practical applications. As the continuity of well known STC reduces chattering in the system, the proposed strategy is beneficial over the current ISM based CNF control law which has a discontinuous term. Two controllers with integral sliding surface are designed to control the position of the pitch and the yaw angles of the 2- DOF helicopter. The adequacy of this specific combination has been exhibited through general analysis, simulation and experimental results of 2-DOF helicopter setup. The acquired results demonstrate the good execution of the proposed controller regarding stabilization, following reference input without overshoot against actuator saturation and robustness concerning to the limited matched disturbances.     

A novel geometric error modeling optimization approach based on error sensitivity analysis for multi-axis precise motion system

Journal of Mechanical Science and Technology - In this paper, a novel error modeling approach for multi-DOF precise motion platform (MPMP) based on the error sensitivity analysis (ESA) is...     

一类变质心多体系统的建模方法

当前机械系统的构件越来越多,并且拓扑结构也越来越复杂,针对一类质心变化的多体系统,基于虚功率原理,建立了该系统非质心系动力学方程,所得到的动力学方程物理意义直观,形式简单.并与质心动力学方程进行了比较,证明了所得到的非质心系动力学方程与质心动力学方程的一致性.当系统质心变化时,质心坐标系也随之改变,因此应用非质心系动力学方程,可以避免由于质心变化而引起的繁琐的参数计算,所得到的方法适用于一般变质心多体系统动力学建模.