We propose a safety control approach based on the online optimal scaling of the size of bounding volumes used as dynamic safety zones for collaborative robotics. Intersection tests between bounding volumes surrounding robot and human allow the safety controller to identify possible collisions. Our proposed approach optimizes online smooth stop trajectories, to be engaged if a potential collision is detected. Unlike other approaches, the robot dynamics and its torque constraints are here considered to plan optimal trajectories that minimize the size of safety zones surrounding the robot. Simulation results on a validated model of a robot with seven degrees-of-freedom verify the feasibility of the proposed approach.

In this paper, we present a new family of overhead traveling cranes based on variable radius drums (VRDs), called cable-based robotic cranes (CBRCs). A VRD is characterized by the variation of the spool radius along its profile. This kind of device is used, in this context, for the development of a cable-robot, which can support and move a load through a planar working area with just two degrees of freedom. First we present the kinematic analysis and the synthesis of the geometry of a VRD profile. Then, the schema of a bidimensional horizontal moving mechanism, based on the VRD theory, and an experimental prototype of a three-dimensional CBRC are presented. The features of this wire-based overhead crane and an analysis of cables tensions are discussed. Finally, the performance of this mechanism is evaluated, demonstrating a deviation between the end-effector and the nominal planar surface of less than 1% throughout the whole working area.