折页式三自由度并联机构结构优化与固有频率研究

发布时间：2018-04-04 11:12

本文选题：并联机构　切入点：动力学　出处：《哈尔滨工业大学》2017年硕士论文

【摘要】：武器装备的性能、临战状态、可靠性试验、设备验收以及作战性能评估主要通过力学环境测试来完成。力学环境模拟实验台就是为武器装备提供相应的力学环境(如噪音、振动、摇摆、空间微重力以及碰撞)的设备。并联机构相对串联机构因为其机构简单紧凑、刚度大、无累积误差、精度高和承载能力强而在运动环境模拟方面得到了广泛应用。本文提出了一种折页式三自由度并联机构用于摇摆模拟,其具有承载能力强、运动范围大、刚度高等优点。鉴于它的这些优点,因此,有必要对它的结构、运动学、动力学、频率特性等基础理论进行研究,以便更快地实现工业应用。该折页式三自由度并联机构存在三个自由度的伴随运动和折页结构,导致机构分析变得复杂,其约束方程分为两种方式产生:折页长度约束和机构结构约束。针对这些问题,本文首先提出一种投影支链坐标系法用于机构运动学建模。基于此方法,使得运动学分析的计算过程得到大大简化,并将机构所有的构件的速度和加速度都表达为雅可比矩阵及其一阶导的组合结果,形式统一规整。然后,本文提出一种新的雅可比矩阵一阶导数的求解方法,该方法减少了计算量且便于程序实现。最后,基于Kane方法完成了机构的多刚体建模,通过这三个方面的建模使得机构的运动学和动力学模型独具有规整统一的形式,从而将机构动力学分析归结为:构建约束方程、求解雅克比矩阵及其一阶导和带入动力学方程这三个程式化过程。建立并联机构的模型并不是机构分析的最终目的,我们期望通过动力学模型完成机构特性分析、结构优化以及控制系统设计。因此,为了完成机构的优化,本文首先提出了并联机构的性能评价指标,如灵巧性、力传递特性、可达空间等。针对机构的可达空间这一性能指标,本文首先分析了结构参数对机构处于中位的可达空间边界的影响,并给出机构大范围运动的合适的结构参数范围。然后,研究了极限位姿下的雅可比矩阵条件数和作动器静态力的关系,给出了机构容易发生奇异的判断条件。最后,基于前述的结构参数围,以作动器最大行程、最大出力和结构紧凑为目标完成了机构结构参数优化过程,并对优化的结构参数进行了分析。当少自由度并联机构选择不同的广义速度建模时,发现其固有频率模型的维度并不同。为了清晰认识该问题,首先,本文在前面的结构参数的基础上设计了该并联机构的液压动力机构。然后,建立不同广义速度下的固有频率模型。最后,完成固有频率相关分析。多刚体动力学模型验证和固有频率模型验证分别在Sim Mechanics和Adams环境下完成验证。
[Abstract]:Weapon performance, combat condition, reliability test, equipment acceptance and combat performance evaluation are mainly accomplished by mechanical environment test.The mechanical environment simulation bench is a kind of equipment that provides the corresponding mechanical environment (such as noise, vibration, swing, space microgravity and collision) for weapon equipment.The parallel mechanism is widely used in the simulation of motion environment because of its simple and compact structure, high stiffness, no cumulative error, high precision and strong bearing capacity.In this paper, a folding 3-DOF parallel mechanism is proposed for rocking simulation, which has the advantages of strong bearing capacity, wide range of motion and high stiffness.In view of these advantages, it is necessary to study the basic theories of its structure, kinematics, dynamics, frequency characteristics and so on, in order to realize industrial application more quickly.There are three degrees of freedom adjoint motion and folding structure of the three degree of freedom parallel mechanism, which makes the analysis of the mechanism become more complicated, and the constraint equation can be divided into two ways: length constraint and structure constraint.In order to solve these problems, a projective branch chain coordinate system method is proposed for kinematic modeling of mechanism.Based on this method, the computational process of kinematics analysis is greatly simplified, and the velocity and acceleration of all components of the mechanism are expressed as the combined results of Jacobian matrix and its first order derivation.Then, a new method for solving the first derivative of Jacobian matrix is proposed.Finally, based on the Kane method, the multi-rigid-body modeling of the mechanism is completed. The kinematics and dynamics model of the mechanism has a unique and uniform form through the modeling of these three aspects, and the dynamic analysis of the mechanism is reduced to: constructing the constraint equation.Three formulaic processes of solving Jacobian matrix and its first order derivation and introducing dynamic equations.Establishing the model of parallel mechanism is not the ultimate purpose of mechanism analysis. We expect to complete the mechanism characteristic analysis, structure optimization and control system design through dynamic model.Therefore, in order to achieve the optimization of the mechanism, the performance evaluation indexes of the parallel mechanism, such as dexterity, force transfer characteristics, reachable space and so on, are put forward in this paper.Aiming at the performance index of the reachable space of the mechanism, this paper first analyzes the influence of the structural parameters on the boundary of the reachable space in the middle position of the mechanism, and gives the suitable range of the structural parameters for the large range motion of the mechanism.Then, the relation between the Jacobian matrix condition number and the actuator static force under the limit position and pose is studied, and the judgement condition of the mechanism being prone to singularity is given.Finally, based on the structural parameter circumference mentioned above, the optimization process of the mechanism structural parameters is completed with the aim of maximum stroke, maximum output force and compact structure of the actuator, and the optimized structural parameters are analyzed.It is found that the dimensions of the natural frequency model are different when different generalized velocity models are selected for the small degree of freedom parallel mechanism.In order to understand the problem clearly, firstly, the hydraulic power mechanism of the parallel mechanism is designed based on the structural parameters.Then, the natural frequency model with different generalized velocities is established.Finally, the inherent frequency correlation analysis is completed.The multi-rigid body dynamic model verification and the natural frequency model verification are carried out in Sim Mechanics and Adams environment, respectively.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TJ06;TH112

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