3-UCR三自由度并联机构瞬态运动学研究

针对一种特殊3-UCR并联机构，基于反螺旋理论与虚拟机构法对其瞬态运动特性进行了分析，利用支链与动平台的一阶影响系数矩阵之间的关系，建立了此并联机构在螺旋坐标系下的瞬态运动数学模型，得出了一阶影响系数矩阵只与机构输入参数、机构构型有关的结论，同样此建模方法适用于其它欠自由度并联机构的瞬态运动特性分析。通过此数学模型，研究得到任意瞬态的螺旋系节距，表明该机构具有两转动一平动的瞬态运动特性，并利用动静平台平行位姿时的具体数值实例，验证了此瞬态运动特性符合前述分析结果。

Instantaneous Kinematic Characteristic of 3-UCR Parallel Robot

Based on principal screw theory and imaginary mechanism method, the transient kinematic characteristics of a three degree-of-freedom spatial parallel manipulator with three UCR limbs are analyzed. According to the topologic structure of limbs, the screw coordinate system is set up and the kinematics of limbs are analyzed. By using the relation between the influence coefficient matrixes of limbs and moving platform, the transient kinematic model in the screw coordinate is established. It is shown that the influence coefficient matrix only depends on the inputs and the kinematic parameters, and the method is also fit for the transient kinematic characteristic analysis of other kinds of lower- DOF parallel manipulators. The gained transient pitches of principal screws show that the manipulator has three DOFs in one translation and two rotations. By numerical examples of moving platform paral- lel to the base, the kinematic characteristics of the parallel manipulator are verified.