A Novel Reconfigurable 3-URU Parallel Platform

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

“…Unfortunately, the platform pose is out of control at a constraint singularity, and this simple method for reconfiguring the machine cannot be implemented. Carbonari et al [26] bypassed the problem by proposing a reconfigurable 3-URU that could switch from TPM to PW and vice versa at a given non-singular configuration. Their 3-URU ( Figure 8) satisfies conditions (a) and (b), and adopts an ad-hoc-conceived device, which modifies the geometry of the U-joints adjacent to the base.…”

“…A general analytic expression of Equation (20b) has been deduced in [21] where, by using the Rodrigues parameters [35] to parameterize the platform orientation, a fourth-degree polynomial equation in the three Rodrigues parameters has been obtained. [26]: Joint configurations A and B refer to the TPM and PW modes, respectively, the padlock denotes the locked R-pair, the darker R-pair is the actuated pair. Figure downloaded from [36] https://www.mdpi.com/2218-6581/7/3/42 and reproduced with the permission of the authors.…”

“…(22b) Figure 8. Carbonari et al reconfigurable 3-URU [26]: Joint configurations A and B refer to the TPM and PW modes, respectively, the padlock denotes the locked R-pair, the darker R-pair is the actuated pair. Figure downloaded from [36] https://www.mdpi.com/2218-6581/7/3/42 and reproduced with the permission of the authors.…”

“…The central issue for actually getting a reconfigurable 3-UTU is how to manage the passage through a singular configuration? In [26], Carbonari et al bypassed the problem by proposing a reconfigurable 3-URU ( Figure 8) that could switch from TPM to PW and vice versa at a given non-singular configuration through an ad-hoc-conceived device, which modifies the geometry of the U-joints adjacent to the base. In the same line, Sarabandi et al [27] presented a particular 3-UPU geometry that can switch from TPM to PW and vice versa by simply turning the platform assembly upside down.…”

Design of a Lockable Spherical Joint for a Reconfigurable 3-URU Parallel Platform

“…Consequently, the authors studied different topologies, which have in common with the 3-CPU manipulator the same types of mobilities [23] among them the 3-URU (Universal-Revolute-Universal) architecture was selected to design a novel reconfigurable manipulator [24,25]. The 3-URU manipulator can be derived from the 3-SRU (Spherical-Revolute-Universal) topology: the spherical joint connecting the leg to the fixed platform can be thought as the composition of three revolute joints with concurrent axes; locking one of them selectively, the joint turns into a universal joint with different sequences of rotations.…”