Single-loop wrists which generate triangular structures

Closed kinematic chains (parallel architectures) allowthe actuators to be located on or near to the frame, which makes them much lighter and faster than their serial counterparts. Due to their multi-loop topology, these advantages are usually accompanied by reducedworkspaces and complex kinematics. The reduction of the closed-loop number could be a design rule to attenuate these drawbacks, provided the resulting architectures still keep the above-mentioned advantages. Here, some single-loop architectures for parallel wrists are presented which still allow the actuators to be located on or near to the frame.Moreover, the kinematic analysis of these architectures is studied in depth.