Dynamics of a 3-RRR Spherical Parallel Mechanism Based on Principle of Virtual Powers

Some recursive matrix relations for the geometric analysis, kinematics and dynamics of a 3-RRR symmetric spherical Agile Wrist parallel mechanism are established. The manipulator prototype is a three-degree-offreedom mechanical system with three parallel legs. Controlled by concurrent torques, which are generated by some electric motors, three active elements of the robot have three independent rotations. Supposing that the position and the rotation motion of the moving platform are known, an inverse dynamic problem is developed using the principle of virtual powers to compute actuating couples. Finally, some matrix relations and some graphs for the torques and the powers of the actuators are determined.