Mechanism for active Î -joint as an equivalent to the combination of revolute joint and proximal fixed-length link

The Pa or Π-joint, as a planar parallelogram four-bar linkage, is of particular interest and importance for parallel kinematic mechanisms. With the idea of replacing the combination of an active revolute joint and of a proximal fixed-length link with an active (powered and controlled) Π-joint, a new parallelogram-based one-degree-of-freedom (1-DOF) mechanism has been developed. The paper describes the structure of the mechanism, modeling approach and analysis as well as the developed active Π-joint laboratory prototype.