Functional Design and Optimization of a Novel 3-URU Multimodal Reconfigurable Robot

This paper presents the functional design and dynamics optimization of a reconfigurable 3-DoF parallel kinematics manipulator conceived for motions of pure rotations and pure translations. The main peculiarity of the device, indeed, is that of allowing changes of the mobility of its moving platform. The kinematic structure of the three identical legs is designed in a way that, when a particular configuration of the manipulator is reached, the transition between the working modes is possible through the reconfiguration of three metamorphic universal joints, which are used to connect each limb to the ground. This configuration allows to limit the weight of the moving bodies of the robot, with a consequent enhancement of the dynamic performance. The kinematics of the parallel robot is introduced in the very first part of the work as a necessary preamble to the optimization of the manipulator geometry, which has been performed in two steps: at first, the Jacobian matrices which characterize the two working modes were used as performance indices for the preliminary functional optimization of the device; subsequently, an optimization of the dynamic behaviour was performed to obtain a complete characterization of the robot in both its modes.