Mechanical Design and Analysis of a Novel 6-DOF Hybrid Robot With Large Orientation Workspace for Dental Application

A hybrid robot structure is capable of merging the advantages of both serial and parallel mechanisms, which guarantees its potential in medical robotic fields, especially in dental surgery applications. This paper presents a novel hybrid robot with three translational and three rotational movements. A systematic mechanical design methodology on the basis of the screw theory is proposed to comprehensively search for feasible five-degrees-of-freedom parallel structures. The usage of only planar kinematic joints is beneficial to large translation/rotation reachable workspaces. A parallel robot is chosen to construct a six-degrees-of-freedom hybrid structure. Both the position and velocity relations between the actuators and the mobile platform are established for the parallel unit. Sloping linkages in the curved shape instead of the straight shape are employed to improve the range of motion of the corresponding rotary joints. Both the translation/rotation workspaces are investigated and the manipulability measure is explored. The novel mean manipulator velocity ratio index is developed and examined on this parallel robot. A multi-objective optimization based on an evolutionary algorithm is conducted.