A 3-RER multi-mode parallel mechanism that has both shaky and regular operation modes

Multi-mode parallel mechanisms (PMs) are a class of reconfigurable PMs that can switch between different operation modes without needing to be disconnected and reassembled. This paper reveals that a 3-RER (or 3-UPU) PM, proposed in an earlier publication by the author, has both regular operation modes, where the moving platform has the same instantaneous degree-of-freedom (DOF) and finite DOF, and shaky operation modes, where the moving platform has different instantaneous DOF and finite DOF. The reconfiguration analysis, including the motion mode analysis using the primary decomposition of ideals and the instantaneous mobility analysis of the PM using screw theory, are presented. The analysis shows that the 3-RER multi-mode PM has nine operation modes, including four 3-DOF spatial translation modes, three 3-DOF planar operation modes, and two 3-DOF zero-torsion operation modes. Among the three operation modes that the PM can switch between without link interference, two are shaky, while the remaining one is regular. This work provides a starting point for further research on multi-mode PMs that have a shaky operation mode. • Introduced detection of shaky operation mode in the reconfiguration analysis. • Presented a parallel mechanism with both shaky and regular operation modes. • Identified all the operation modes of the multi-mode parallel mechanism. • Detected shaky operation modes via instantaneous mobility analysis. • Revealed how the parallel mechanism switches between different operation modes.