提出了一类新的三自由度变几何桁架机器人。该机械手由一个八面体和三个平行连接的四面体组成，设计为可折叠对称。本文还提出了一种机器人位移分析的方法。正、逆位移分析的闭式解可以通过显式表达式得到。因此，该方法以最小的计算量产生精确的解。

A NEW CLASS OF 3 DOF VARIABLE GEOMETRY TRUSS MANIPULATORS IS PROPOSED. THE MANIPULATOR IS COMPOSED OF AN OCTAHEDRON AND THREE TETRAHEDRONS CONNECTED IN A PARALLEL FORM AND DESIGNED TO BE COLLAPSIBLE AND SYMMETRICAL. A METHOD FOR THE DISPLACEMENT ANALYSIS OF THE MANIPULATORS IS ALSO PRESENTED. THE CLOSED-FORM SOLUTIONS FOR THE FORWARD AND INVERSE DISPLACEMENT ANALYSIS CAN BE OBTAINED BY EXPLICIT EXPRESSIONS. THEREFORE, THE METHOD PRODUCES ACCURATE SOLUTIONS WITH MINIMAL COMPUTATION.