Analysis and Design of a 3-DOF Spatial Underactuated Differentially Flat Robot

Abstract

This paper deals with the extension of the differential flatness theory to spatial underactuated robots. A 3-DOF robot with a kinematic structure resembling the one of a 6-DOF industrial robot with spherical wrist is considered. The conditions that the mass distribution of the passive link has to satisfy to guarantee differential flatness are defined. A prototype is designed and built. Numerical simulations show that the robot is able to perform point-to-point motions with small oscillations of the end effector. Numerical results are corroborated by experimental tests.