基于变胞铰链的并联机构结构设计与构型分析

Structural Design and Configuration Analysis of Parallel Mechanism with Metamorphic Joint

为了拓展变胞机构的种类,提出了一种变胞运动单元,该变胞单元采用三个旋转关节,并且三个旋转关节可以通过位置调节形成等效球铰、虎克铰以及转动副。与传统的锁定运动副来实现变胞功能的变胞单元相比,此变胞单元三种构型的切换只需对轴线位置调整,无需额外增加关节锁死电机。通过研究由线矢量构成的螺旋系统的相关性,揭示了变胞运动单元构态变化的基本原理。提出了可用于构造新型变胞并联机构的支链构型设计方法,并基于螺旋的互易性分析了各支链构型所必须满足的几何约束条件。提出了两种变胞并联机构,通过不同的支链装配形式可将其从6自由度构型转换为3自由度构型,并对支链安装形式进行改进,构造出了具有3自由度平移模式和3自由度转动模式的并联机构。对变胞支链作为中心支链组装而成的并联机构的构型及对应的运动类型进行了分析,获得了六种不同构型的并联机构。

In order to expand the types of metamorphic mechanisms,a metamorphic unit is proposed.A new family of metamorphic kinematic unit composed of three rotational joints is proposed,and the equivalent spherical joint,Hooke joint and rotational joint can be formed by adjusting the position of the rotational joint.Compared with the traditional metamorphic unit which realizes the function of metamorphic by locking the effective rotational joint,the configuration of the metamorphic unit can be switched only by adjusting the axis position,and no additional locking motor is needed.By analyzing the independence of the screw system composed of line vectors,the basic principle of the metamorphic unit is revealed.A limb configuration design method which can be used to construct a new type of metamorphic parallel mechanism is proposed.Based on the reciprocity of screw,the geometric constraints of each limb configuration are analyzed.Two kinds of metamorphic parallel mechanisms are proposed,which can be transformed from 6-DOF configuration to 3-DOF configuration through different limb assembly forms.The parallel mechanism with 3-DOF translational mode and 3-DOF rotational mode is constructed by improving the installation form of limb.The configuration and corresponding motion types of the parallel mechanism assembled by metamorphic limb as central limb are analyzed,and six different configurations of parallel mechanism are obtained.