Analysis of nonlinear structural dynamics by the concept of stability measure

Engineering structures may collapse under dynamic loading, resulting in large displacement motions. The generation of the equations of motion, and an approach for the stability assessment of nonlinear vibrations are presented. The Duffing oscillator is used as an example for the application of the method presented.     

Dynamic simulation of crankshaft multibody systems

General multibody system approaches are often not sufficient for specific situations in applications to yield an efficient and accurate solution. We concentrate on the simulation of the crankshaft dynamics which is characterized by flexible bodies and force laws describing the interaction between the bodies. The use of the floating frame of reference approach in our model leads to an index-2 DAE system. The algebraic constraints originate from the reference conditions and the normalization equation for the quaternions. For the time integration of this system, two aspects have to be taken into account: firstly, for efficiency exploiting the structure of the system and using parallelization. Secondly, consistent initial values also with respect to a related index-3 system have to be computed in order to compute missing initial velocities and to reduce transient phenomena. The work of C.B. Drab, J.R. Haslinger, and R.U. Pfau is supported by the “Bundesministerium für Wirtschaft und Arbeit” and by the government of Upper Austria within the framework “Industrielle Kompetenzzentren und Netzwerke”.     

On the effect of linear algebra implementations in real-time multibody system dynamics

This paper compares the efficiency of multibody system (MBS) dynamic simulation codes that rely on different implementations of linear algebra operations. The dynamics of an N-loop four-bar mechanism has been solved with an index-3 augmented Lagrangian formulation combined with the trapezoidal rule as numerical integrator. Different implementations for this method, both dense and sparse, have been developed, using a number of linear algebra software libraries (including sparse linear equation solvers) and optimized sparse matrix computation strategies. Numerical experiments have been performed in order to measure their performance, as a function of problem size and matrix filling. Results show that optimal implementations can increase the simulation efficiency in a factor of 2–3, compared with our starting classical implementations, and in some topics they disagree with widespread beliefs in MBS dynamics. Finally, advices are provided to select the implementation which delivers the best performance for a certain MBS dynamic simulation.     

可变形多体系统动力学及接触力学在凸轮机构学中的应用述评

高速、高精度控制与传动中凸轮机构仍然具有无可替代的优越性。但当前面临的问题往往是加工精度已经达到，而速度比国外产品低得多，迫切要求深入分析机构的动态特性。为此必须借助可变形多体系统动力学及接触力学的最新成果。本文结合弹性动力学与接触力学介绍凸轮机构动力学的若干前沿课题。评介已进行的工作，并整理资料为有关研究提供素材。对机构学其他领域的研究也有参考价值。     

柔性多体系统动力学单向递推组集建模方法

提出了一种柔性多体系统动力学计算机辅助建模方法，即单向递推组建模方法。在运动学正向递推过程中程式化地组集建立链状，树状及含闭环的柔性多体系统用铁相对坐标及模态坐标表达的动力学方程，且有传统的绝对坐标方法及铰相对坐标方法的优点并克服了它们的不足。结果的形式同多刚体系统动力学方程兼容，并适合处理变结构多体机械系统的仿真。由于各条链上递推组集的独立性，本方法极易并已发展为并行计算方法。     

A new solution for mechanisms including Coulomb friction

This paper presents a new solution method for the analysis of multibody systems with Coulomb friction. Complete equations of motion and reaction forces are derived by using Lagrangian formulation and the traditional friction circle concepts for the analysis of Coulomb friction. The numerical solutions by the new method, as well as the conventional method for comparision, are illustrated. The new method saves considerably the computer execution time to solve equations of motion and reaction forces compared with the conventional method for same accuracy. The higher the coefficient of friction is, the more the computation time of the conventional method is needed but the computation time of the new method is nearly independent on the coefficient of friction.     

基于多体模型的汽车半主动悬架控制方法研究

针对半主动悬架控制中的两个重要问题——系统模型的建立和控制策略的确定进行了深入的研究,建立了汽车的多体动力学方程,提出了半主动悬架模糊神经网络控制方法,设计了控制系统,应用遗传算法优化了控制器的参数和结构,用基于变尺度的BFGS算法优化神经网络权值,在仿真研究的基础上进行了试验研究,结果表明提出的方法能明显改善悬架性能。     

车下设备悬挂参数与车体结构之间的匹配关系研究

本文通过建立等效欧拉梁车体与设备垂向耦合振动模型,研究了车下设备刚性悬挂与弹性悬挂对车体振动的影响。研究结果表明,车下设备采用弹性悬挂的设计方式能够有效抑制车体的弹性振动。为了研究车下设备弹性悬挂参数与车体结构之间的匹配关系,本文基于模态叠加法原理法建立了考虑车体弹性振动和车下设备的高速动车组刚柔耦合动力学模型。通过该三维模型分析了车下设备质量偏心和弹性悬挂参数对车体振动响应的影响规律。仿真结果表明,车下设备横向偏心主要影响车体的横向振动特性,而车下设备纵向偏心主要影响车体的垂向振动特性;当车下设备的悬挂频率接近车体的垂向弯曲频率时能够降低车体的整体振动水平,而当车下设备的悬挂频率低于车体的垂向弯曲频率时,提高车下设备弹性悬挂系统的阻尼能够一定程度上抑制车体的弹性振动。