A hybrid serial-parallel mechanism for milling applications
Fernando Malvezzi1; Ricardo Cantagalli2; Rafael Belardo Filho2; Leonardo Aguiar1; Flavio Heiji Shigeoka1; Juliano Aparecido de Avila1
1 Instituto Mauá de Tecnologia; 2 B. GROB DO Brasil
doi:10.20906/CPS/COB-2015-0686
Resumo
Parallel mechanism is a mechanical system with independent kinematic chains, actuating in-parallel on the end-effector. The main advantages of this mechanism are high load capacity, high structural stiffness, low inertia, fast dynamic response and high accuracy. Because of these features, it has been employed in flight simulators, robotic manipulators and machine tools. This work presents a mechanism to be applied in milling applications. Topologically, it is a hybrid serial-parallel mechanism with 4 DOF. The proposed structure is based on a 3PRR planar parallel architecture, assembled on a serial base. The piece to be machined is fixed on the moving platform, which is capable to execute 3 translations and 1 rotation. The methodology applied in this work involves: the choice of the robotic structure, the development of the direct and inverse kinematic models, available workspace evaluation and singularity analysis. A prototype was built, which is formed by the following subsystems: mechanical, actuator and control. The mechanical subsystem is essentially the serial-parallel mechanism, which contains a base and a moving platform, both connected by three active kinematic chains. Three electrical DC servomotors and their respective drivers compose the actuator subsystem. Control subsystem includes a PC computer, three servomotor controllers, three angular encoders, a communication cable, and an inverse kinematics model, written in MatLab that calculates actuator displacements from a specified sequence of moving platform positions. This prototype was tested under the machining operations. The predicted workspace was approximately reached by the prototype and there is no singular configuration inside the specified workspace. Moreover, based on the kinematic behavior obtained by the built prototype, we conclude that there is a potential for this hybrid serial-parallel mechanism as a machine tool.
Palavras-chave: Parallel mechanism; Parallel robots; Kinematic; Milling; Machine tool