Joint Forces in Dynamics of a Spatial Parallel Manipulator

One of the research directions in recent decades is the construction of manipulators with parallel architecture. These mechanisms are closed-loop structures that consist of numerous separate serial chains acting in parallel and connecting the fixed base to the moving platform. Equipped with revolute or prismatic actuators, parallel manipulators have a robust construction and can move bodies of large dimensions with high velocities and accelerations. Among these, the class of manipulators known as Stewart-Gough platform focused great attention (Stewart [1]; Merlet [2]). Accuracy and precision in the direction of the tasks are essential since the positioning errors of the tool could end in costly damage. But, from the application point of view, the limited workspace and complicated singularities are two major drawbacks of these mechanical structures. The prototype of the Delta parallel robot (Clavel [3]; Tsai [4]) and the Star parallel manipulator (Hervé and Sparacino [5]) are equipped with three motors, which train on the mobile platform in a three-degrees-of-freedom translational motion. Angeles [6], Wang and Gosselin [7] analysed the kinematics, dynamics and singularity loci of Agile Wrist spherical robot with three actuators. The 3-RPS parallel mechanism, here analyzed, consists of a moving platform, a fixed base and three limbs of identical structure. Because the robot motion in the translation and orientation degrees of freedom are interconnected, this makes the