A Novel Four-DOF Parallel Manipulator Mechanism and Its Kinematics

Abstract

A novel 4-UPU parallel manipulator mechanism that can perform three-dimensional translations and rotation about Z axis is presented. The principle that the mechanism can perform the above motions is analyzed based on the screw theory, the mobility of the mechanism is calculated, and the rationality of the chosen input joints is discussed. The forward and inverse position kinematics solutions of the mechanism and corresponding numerical examples are given, the workspace and the singularity of the parallel mechanism are discussed. The mechanism having the advantages of simple symmetric structure and large stiffness can be applied to the developments of NC positioning platforms, parallel machine tools, four-dimensional force sensors and micro-positional parallel manipulators.

A Review of the Literature on the Lower-Mobility Parallel Manipulators of 3-UPU or 3-URU Type

“…From a geometric point of view, Equation (9) is satisfied when the three vectors h i , for i = 1, 2, 3, are coplanar (i.e., when all the intersections among the planes parallel to the U-joints' cross links are parallel lines). Consequently, if the unit vectors w 1i (w 4i ), for i = 1, 2, 3, are all parallel, this geometric condition is always satisfied 5 and a structural rotation (constraint) singularity occurs [29][30][31].…”

“…The resulting 4-UPU is a Shoenflies motion generator [28]. It was presented in [29] and studied in [30][31][32].…”

“…Eventually, structural singularities of 3-UPU architectures were used to ideate a Shoenflies motion generator [28] of 4-UPU type [29][30][31][32], and a rolling mechanism [33].…”

A new robotic horseback-riding simulator for riding lessons and equine-assisted therapy

“…2 Meanwhile, Chen et al designed a horseback-riding simulator with a classic 6-DOF Stewart platform and additional PC for virtual reality, 3 and Eskola and Handroos devised a simulator that realized three basic gaits: walking, trotting, and galloping based on a 6-DOF hydraulic Gough-Stewart platform. 4 However, since aircraft simulators form the basis for horseback-riding simulators, existing simulators commonly use parallel mechanisms [5][6][7] which generate larger forces than serial ones and have integral 6-DOF platforms operated by hydraulic or electric actuators. Although electric actuators have wider control bandwidth and higher accuracy than hydraulic actuators, 4 and so are preferred, their relatively high cost and low weight-thrust ratio are problematic.…”

“…However, since aircraft simulators form the basis for horseback-riding simulators, existing simulators commonly use parallel mechanisms 5 –7 which generate larger forces than serial ones and have integral 6-DOF platforms operated by hydraulic or electric actuators. Although electric actuators have wider control bandwidth and higher accuracy than hydraulic actuators, 4 and so are preferred, their relatively high cost and low weight–thrust ratio are problematic.…”