This paper presents a three Degrees of Freedom (DOFs) parallel manipulator with no rotational capacity. Planar kinematic pairs (revolute joint and prismatic joint) are exclusively employed in this parallel structure. The parallelogram joint in each kinematic chain assists to ensure the moving platform’s orientation is constant throughout the reachable workspace. Unlike the general parallel mechanisms, three identical kinematic limbs are degenerated to two kinematic limbs through merging two passive prismatic joints with same movement. Three active sliding joints are still required to drive this special parallel structure. Its mobility characteristic is firstly studied in detail and all possible singularity configurations are discussed by means of screw theory. The Lagrangian formulation is employed to compute the mathematical model of the inverse dynamic problem. The reachable workspace is obtained based on the inverse kinematic solutions. The distributions of the maximum joint force effect and maximum joint velocity effect are conducted. An example is provided to illustrate their trends under preset motion of the mobile platform.

本文介绍了一种没有旋转能力的三自由度 (DOF) 并联机械手。平面运动对（旋转关节和棱柱关节）仅在此平行结构中使用。每个运动链中的平行四边形接头有助于确保移动平台的方向在整个可到达的工作空间中保持恒定。与一般的并联机构不同，三个相同的运动肢通过合并两个相同运动的被动棱柱关节退化为两个运动肢。仍然需要三个主动滑动关节来驱动这种特殊的平行结构。首先详细研究了它的移动特性，并通过螺旋理论讨论了所有可能的奇点配置。拉格朗日公式用于计算逆动力问题的数学模型。可达工作空间是基于逆运动学解决方案获得的。进行了最大关节力效应和最大关节速度效应的分布。举例说明移动平台预设运动下它们的变化趋势。