Type Synthesis of 3-DOF Spherical Parallel Manipulators Based on Screw Theory

Abstract

A spherical parallel manipulator (SPM) refers to a 3-DOF parallel manipulator in which the moving platform has only three pure rotational degrees of freedom of motion relative to the base. A method is proposed for the type synthesis of SPMs based on screw theory. The wrench systems of a spherical parallel kinematic chain (SPKC) and its legs are first analyzed. A general procedure is then proposed for the type synthesis of SPMs. The type synthesis of legs for SPKCs, the type synthesis of SPKCs, as well as the input validity check of SPMs are dealt with in sequence. SPKCs with and without inactive joints are synthesized. The number of over-constraints of each SPKC is also given. The phenomenon of dependent joint groups in a SPKC is revealed for the first time. The input validity check of SPMs is also simplified.

Structural Synthesis of Parallel Mechanisms That Provide Plane-Parallel Motion of the Output Link Based on the Theory of Screws and Virtual Kinematic Chains

“…Понятие траектории движения подвижной платформы содержит больше информации, чем число ее степеней свободы, и из-за потребности в параллельных механизмах с числом степеней свободы меньшим 6, структурному синтезу параллельных механизмов с заданной траекторией движения начиная с 1990-х гг. уделяется все большее внимание [3][4][5][6][7][8][9][10]…”

U-Joint Induced Torsional Instabilities of a Family of 3-DOF Partially-Decoupled Spherical Parallel Manipulators

“…Three-degree-of-freedom (3-dof) spherical parallel manipulators (SPMs), working as robotic joints [1], orientating device [9], and devices with remote center of motion [13], have been studied in the literature for several decades. Typical symmetrical SPMs, such as 3RRR 3 or 3UPU-S ones [3,10,20,21], usually have limited rotational capabilities, particularly, the torsional movement around the axis normal to the end-effector. In order to realize the unlimited rotation to extend the applications of the SPMs, an asymmetrical 2RRR-RUR-RPS SPM [24] as shown in Fig.…”

A non-overconstrained variant of the Agile Eye with a special decoupled kinematics

“…For example, Kong and Gosselin 4,5 proposed the type synthesis of 3-DOF spherical parallel manipulators by using screw theory. Generally, a kinematically non-redundant parallel orientation mechanism can be constructed in two different ways.…”