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1.
The objective of this study is to present an accurate and simple method to describe the motion of constrained mechanical or
structural systems. The proposed method is an elimination method to require less effort in computing Moore-Penrose inverse
matrix than the generalized inverse method provided by Udwadia and Kalaba. Considering that the results by numerical integration
of the derived second-order differential equation to describe constrained motion veer away the constrained trajectories, this
study presents a numerical integration scheme to obtain more accurate results. Applications of holonomically or nonholonomically
constrained systems illustrate the validity and effectiveness of the proposed method. 相似文献
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Although many methodologies exist for determining the constrained equations of motion, most of these methods depend on numerical
approaches such as the Lagrange multiplier’s method expressed in differential/algebraic systems. In 1992, Udwadia and Kalaba
proposed explicit equations of motion for constrained systems based on Gauss’s principle and elementary linear algebra without
any multipliers or complicated intermediate processes. The generalized inverse method was the first work to present explicit
equations of motion for constrained systems. However, numerical integration results of the equation of motion gradually veer
away from the constraint equations with time. Thus, an objective of this study is to provide a numerical integration scheme,
which modifies the generalized inverse method to reduce the errors. The modified equations of motion for constrained systems
include the position constraints of index 3 systems and their first derivatives with respect to time in addition to their
second derivatives with respect to time. The effectiveness of the proposed method is illustrated by numerical examples. 相似文献
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Salam Rahmatalla Eun-Taik Lee Hee-Chang Eun 《Journal of Mechanical Science and Technology》2013,27(4):941-949
Assuming that the existence of the constraints yields the change of the inertia force, this study derives the time-varying mass matrix for describing the constrained dynamic equation. It is displayed that the results corresponds with the ones by Udwadia and Kalaba. The numerical results obtained by integrating the constrained dynamic equation of second-order differential equations yield the errors in the satisfaction of the constraints. Modifying the derived dynamic equation this study presents a numerical algorithm to reduce the errors and to compute more precise motion. It is illustrated that the proposed method can be more precisely utilized in constrained mechanical systems through two applications of constrained nonlinear robotic systems. 相似文献
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The characteristics of dynamic systems subjected to multiple linear constraints are determined by considering the constrained
effects. Although there have been many researches to investigate the dynamic characteristics of constrained systems, most
of them depend on numerical analysis like Lagrange multipliers method. In 1992, Udwadia and Kalaba presented an explicit form
to describe the motion for constrained discrete systems. Starting from the method, this study determines the dynamic characteristics
of the systems to have positive semidefinite mass matrix and the continuous systems. And this study presents a closed form
to calculate frequency response matrix for constrained systems subjected to harmonic forces. The proposed methods that do
not depend on any numerical schemes take more generalized forms than other research results. 相似文献
5.
Jung Hun Park Hong Hee Yoo Yoha Hwang 《Journal of Mechanical Science and Technology》2000,14(2):159-167
A computational method for the dynamic analysis of a constrained mechanical system is presented in this paper. The partial velocity matrix, which is the null space of the Jacobian of the constraint equations, is used as the key ingredient for the derivation of reduced equations of motion. The acceleration constraint equations are solved simultaneously with the equations of motion. Thus, the total number of equations to be integrated is equivalent to that of the pseudo generalized coordinates, which denote all the variables employed to describe the configuration of the system of concern. Two well-known conventional methods are briefly introduced and compared with the present method. Three numerical examples are solved to demonstrate the solution accuracy, the computational efficiency, and the numerical stability of the present method. 相似文献
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提出一种直接应用力映射矩阵的加权广义逆求解一般被动过约束并联机构(指分支提供给动平台的约束力/力偶数目大于等于1的被动过约束并联机构)的超静定受力问题的方法。基于小变形叠加原理和螺旋理论得到了分支约束力螺旋系刚度矩阵的一般表达式。推导一般被动过约束并联机构的各分支约束力螺旋系幅值与六维外力之间的映射关系式,进而证明了该关系式恰好是力映射矩阵的加权广义逆,其中加权矩阵为各分支约束力螺旋系刚度矩阵组成的分块对角阵的逆。以3-RRC空间三自由度被动过约束并联机构和一个并联振动平台为例,直接应用加权广义逆求解了机构各分支约束力螺旋系的幅值,并进行仿真验证。基于加权广义逆求解被动过约束并联机构的超静定受力问题大大简化了求解过程且解的形式统一、简单。 相似文献
7.
Yong Liu Hai-Chuan Song Jun-Hai Yong 《The International Journal of Advanced Manufacturing Technology》2013,67(9-12):2225-2231
It is a fundamental problem to calculate Jacobian coefficients of constraint equations in assembly constraint solving because most approaches to solving an assembly constraint system will finally resort to a numerical iterative method that requires the first-order derivatives of the constraint equations. The most-used method of deriving the Jacobian coefficients is to use virtual rotation which is originally presented to derive the equations of motion of constrained mechanical systems. However, when Euler parameters are adopted as the state variables to represent the transformation matrix, using the virtual rotation will yield erroneous formulae of Jacobian coefficients. The reason is that Euler parameters are incompatible with virtual rotation. In this paper, correct formulae of Jacobian coefficients of geometric constraints with respect to Euler parameters are presented in both Cartesian coordinates and relative generalized coordinates. Experimental results show that our proposed formulae make Newton–Raphson iterative method converge faster and more stable. 相似文献
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A formulation which seeks steady-state equilibrium positions of constrained multibody systems driven by constant generalized
speeds is presented in this paper. Since the relative coordinates are employed, constraint equations at cut joints are incorporated
into the formulation. To obtain the steady-state equilibrium position of a multibody system, nonlinear equations are derived
and solved iteratively. The nonlinear equations consist of the force equilibrium equations and the kinematic constraint equations.
To verify the effectiveness of the proposed formulation, two numerical examples are solved and the results are compared with
those of a commercial program. 相似文献
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多指抓取的实时力优化算法 总被引:1,自引:0,他引:1
根据非线性摩擦约束与特定结构矩阵正定性之间的等价性,将多指抓取力规划问题描述为线性约束正定矩阵对应的平滑流形最优化问题,并且采用线性约束梯度流方法计算得到最优的抓取力。当手指数目较多时,高维描述矩阵限制了传统线性约束梯度流表达式的计算速度,为了解决该问题,基于力优化过程中描述矩阵的仿射约束特性,提出一种适合实时应用的基于抓取力矢量的线性约束梯度流算法。该算法取代描述矩阵,采用抓取力矢量表示线性约束梯度流,大大降低了线性约束梯度流表达式的维数和计算量。以摩擦点接触情况下的四指灵巧手为对象, 采用该算法进行抓取力计算,分析权重因子和步距因子对于计算结果和收敛速度的影响,证明该算法的正确性和实时性。 相似文献
11.
Dynamic modeling and simulation of multi-body systems using the Udwadia-Kalaba theory 总被引:2,自引:0,他引:2
Laboratory experiments were conducted for falling U-chain,but explicit analytic form of the general equations of motion was not presented.Several modeling methods were developed for fish robots,however they just focused on the whole fish’s locomotion which does little favor to understand the detailed swimming behavior of fish.Udwadia-Kalaba theory is used to model these two multi-body systems and obtain explicit analytic equations of motion.For falling U-chain,the mass matrix is non-singular.Second-order constraints are used to get the constraint force and equations of motion and the numerical simulation is conducted.Simulation results show that the chain tip falls faster than the freely falling body.For fish robot,two-joint Carangiform fish robot is focused on.Quasi-steady wing theory is used to approximately calculate fluid lift force acting on the caudal fin.Based on the obtained explicit analytic equations of motion(the mass matrix is singular),propulsive characteristics of each part of the fish robot are obtained.Through these two cases of U chain and fish robot,how to use Udwadia-Kalaba equation to obtain the dynamical model is shown and the modeling methodology for multi-body systems is presented.It is also shown that Udwadia-Kalaba theory is applicable to systems whether or not their mass matrices are singular.In the whole process of applying Udwadia-Kalaba equation,Lagrangian multipliers and quasi-coordinates are not used.Udwadia-Kalaba theory is creatively applied to dynamical modeling of falling U-chain and fish robot problems and explicit analytic equations of motion are obtained. 相似文献
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针对活动线缆在安装和服役过程中受到单面约束时的运动过程仿真问题,提出一种基于弹性细杆静力学理论的光滑平面约束下的活动线缆物性建模与仿真方法。该方法通过分析活动线缆在光滑平面约束下的受力情况,将活动线缆所受到的约束力用拉格朗日乘子表达,将节点与平面的相对空间位置关系作为限制活动线缆运动的约束方程,得到分布力作用下的活动线缆Kirchhoff平衡方程,并建立活动线缆的物理模型。进而采用非线性约束优化方法求解模型。最后根据不同假设条件进行算例测试,通过比较活动线缆的仿真形态和实际形态,验证模型和数值解法的正确性。结果表明,该模型和解法能充分真实地表达活动线缆的基本物理特性和活动线缆受到光滑平面约束时的形变特点。 相似文献
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新型基于6—PSS三维平台机构的并联微动机器人 总被引:10,自引:0,他引:10
提出一种新颖的基于6-PSS并联三维平台机的微动机器人并介绍其结构布局特点,应用Jacobian矩阵和力Jacobian矩阵的子阵,分别对其线速度与角速度和力与力矩的各项同性进行了分析计算,并建立显式的微位移正解和反解方程,为其设计和使用提供理论依据。分析计算结果表明,该微动机器人算法与控制简单,微位移解耦和速度与力向向同性,具有最佳的运动和力传递性能。 相似文献
16.
Parallel robots are widely used in the academic and industrial fields. In spite of the numerous achievements in the design and dimensional synthesis of the low-mobility parallel robots, few research ef... 相似文献
17.
简要介绍了Simulink与Simmechanics在六杆机构运动分析中的应用。以矢量法建立运动学矩阵方程,分别采用Simulink、Simmechanics进行运动仿真。这两种方法求解效率高,在机构性能分析中具有一定的应用价值。 相似文献
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The modal characteristics of constrained multibody systems undergoing constant accelerated motions are investigated in this
paper. Relative coordinates are employed to derive the equations of motion, which are generally nonlinear in terms of the
coordinates. The dynamic equilibrium position of a constrained multibody system needs to be obtained from the nonlinear equations
of motion, which are then linearized at the dynamic equilibrium position. The mass and the stiffness matrices for the modal
analysis can be obtained from the linearized equations of motion. To verify the effectiveness and the accuracy of the proposed
method, two numerical examples are solved and the results obtained by using the proposed method are compared with those obtained
by analytical and other numerical methods. The proposed method is found to be accurate as well as effective in predicting
the modal characteristics of constrained multibody systems undergoing constant accelerated motions. 相似文献