多体动力学仿真软件 ADAMS 理论及应用研讨

系统地阐述了机械系统自动动力仿真软件ＡＤＡＭＳ的理论基础和求解方法。并结合建模工作，探讨了其应用方法和规律。     

数控机床全误差模型和误差补偿技术的研究

加工精度是数控机床必须保证的一项性能指标。提高机床精度是先进制造技术的重要课题，有误差避免和误差补偿两种方法。前者使机床造价大幅上升，而且精度的提高也有一定的限度。后者的精度提高几乎没有限制，对数控机床，计算机实时误差补偿技术是一种经济、有效的基本途径。基于多体系统理论，推导了多坐标数控机床，包含几何误差和热误差的全误差模型。文中介绍了坐标数控机床项误差的辨识方法(22线、14线和9线法)，还介绍了回转坐标6项误差的辨识方法。通过软件补偿，在3坐标联动和4坐标联动数控机床上实现了几何误差和热误差的补偿。实践结果表明误差模型的准确性和补偿方法的实用性。     

A benchmarking system for MBS simulation software: Problem standardization and performance measurement

Despite the importance given to the computational efficiency of multibody system (MBS) simulation tools, there is a lack of standard benchmarks to measure the performance of these kinds of software applications. Benchmarking is done on an individual basis: different sets of problems are used, and the procedures and conditions considered to measure computational efficiency are also different. In this scenario, it becomes almost impossible to compare the performance of the different available simulation methods in an objective and quantitative way.This work proposes a benchmarking system for MBS simulation tools. The structure of the benchmark problem collection is defined, and a group of five problems involving rigid bodies is proposed. For these problems, documentation and validated reference solutions in standard formats have been generated, and a procedure to measure the computational efficiency of a given simulation software is described.Finally, the benchmarking system has been applied to evaluate the performance of two different simulation tools: ADAMS/Solver, a popular general-purpose commercial MBS simulation tool, and a custom Fortran code implementation of an Index-3 augmented Lagrangian formulation with projections combined with the implicit single-step trapezoidal rule as integration scheme. Results show that the proposed problems are able to reach the limits of the tested simulation methods, and therefore they can be considered good benchmark problems.     

Multibody formalism for real-time application using natural coordinates and modified state space

The paper describes the multibody formalism based on natural coordinates and modified state space that is suitable for real-time applications. The complex multibody systems include closed loops and thus result into DAE equations. Their simulation then usually requires iterative stabilization. The described multibody formalism has two important properties making it suitable for real-time applications. Firstly, it provides the stable solution of DAE equations for multibody systems with kinematical loops without necessity of iterations. Secondly, it consists of system matrices with simple expressions (constant, linear or quadratic terms) for their elements and thus it is very suitable for massive parallelization. The resulting computational complexity is growing only linearly with the number of DOFs despite any occurrence of kinematical loops and it is about 5 times smaller than the recursive multibody formalisms.     

Performance of automatic differentiation tools in the dynamic simulation of multibody systems

Within the multibody systems literature, few attempts have been made to use automatic differentiation for solving forward multibody dynamics and evaluating its computational efficiency. The most relevant implementations are found in the sensitivity analysis field, but they rarely address automatic differentiation issues in depth. This paper presents a thorough analysis of automatic differentiation tools in the time integration of multibody systems. To that end, a penalty formulation is implemented. First, open-chain generalized positions and velocities are computed recursively, while using Cartesian coordinates to define local geometry. Second, the equations of motion are implicitly integrated by using the trapezoidal rule and a Newton–Raphson iteration. Third, velocity and acceleration projections are carried out to enforce kinematic constraints. For the computation of Newton–Raphson’s tangent matrix, instead of using numerical or analytical differentiation, automatic differentiation is implemented here. Specifically, the source-to-source transformation tool ADIC2 and the operator overloading tool ADOL-C are employed, in both dense and sparse modes. The theoretical approach is backed with the numerical analysis of a 1-DOF spatial four-bar mechanism, three different configurations of a 15-DOF multiple four-bar linkage, and a 16-DOF coach maneuver. Numerical and automatic differentiation are compared in terms of their computational efficiency and accuracy. Overall, we provide a global perspective of the efficiency of automatic differentiation in the field of multibody system dynamics.     

多体系统理论在机构运动分析中的应用

本文将多体系统理论用于机构的运动分析,理论分析和计算实例表明：多体系统理论用于机构的运动分析是行之有效的。     

基于模糊控制的旋转倒立摆稳定性仿真研究

倒立摆是一个复杂的、非线性、不稳定的系统,通常采用数学建模的方法研究倒立摆系统,该方法复杂繁琐且在建模过程中简化约束条件,使仿真结果存在一定误差。在Matlab Simulink环境中基于Simscape模块进行倒立摆系统的建模;根据倒立摆系统的运行特征设计了新的模糊规则表,并基于此表建立模糊控制器;采用该模糊控制器在不同的条件下对倒立摆进行控制,取得了良好的控制效果。     

STUDY ON NEW METHOD OF IDENTIFYING GEOMETRIC ERROR PARAMETERS FOR NC MACHINE TOOLS

0 INTRODUCTIONCorrectly identifying the geometric errorpararneters is one of the most fundamental and keytechniques for high accuracy software errorcompensation of NC machine tooIs. By analyzing theec'llTCcs of erro1 Nhich affects the process precision ofNC machine tools, the mathematical model fOrvolumetric error is built. Software error compensationcan improve the process precision by using thesoftware, which is develOped according to themodel. However, only with the accurate geomet…     

Flexible multibody dynamics based fixture-workpiece analysis model for fixturing stability

The machining force and torque exerted on a workpiece vary as the cutter moves along the tool path, therefore a dynamic approach is essential for fixturing stability analysis. This paper presents a technique to dynamically model and analyze the fixture-workpiece system subjected to time-varying machining loads. Combining the advantages of FEA (Finite Element Analysis) and nonlinear rigid body dynamics, a flexible multibody dynamic model is formulated to incorporate the overall interaction (clamping forces, machining loads, and contact friction) between flexible workpiece and compliant fixture elements. Three major parameters affecting the fixturing stability, namely the magnitude, application sequence, and placement of fixturing clamps, are analyzed. Additionally, the time dependent deformation of a flexible workpiece under clamping and machining loads is estimated. A scaled engine block with the 3–2–1 fixturing scheme subjected to face milling operation is given as an example. Comparison between the simulation result and experimental data shows a reasonable agreement.     

基于Hamilton原理的柔性多体系统动力学建模方法

首先基于Ｈａｍｉｌｔｏｎ原理建立起一般柔性体连续系统的动力建模方法,进而以水平面内作大范围回转运动的柔性梁为例,在Ｅｕｌｅｒ－Ｂｅｍｏｕｌｌｉ梁模型的假设前提下,根据轴向不可虎的柔性梁的几何约束条件,推导出作大范围刚体运动的柔性梁连续系统的一致线性化振动微分方程。