Optimal model-based path planning for the robotic manipulation of deformable linear objects

The robotic manipulation of deformable linear objects (DLOs), such as cables, is a valuable yet complex skill. In particular, to realize tasks like cable routing and wire harness assembly, it is required that two robotic arms, grasping the ends of a DLO, move it from an initial shape to a final one where cable assembly can be performed. The manipulation must be performed following a collision-free path and avoiding stretching and excessively deforming it. We address this problem by proposing an optimal model-based path planning strategy. Specifically, a hierarchical optimization strategy is defined to perform path planning, exploiting a mass–spring DLO dynamic model that we enhance to handle a generic equilibrium condition for the DLO. Furthermore, we model the interaction of the DLO with objects like clips used in assembly operations. We also deal with the estimation of the DLO stiffness to properly tune the model parameters. The effectiveness of our methodology is assessed via experimental tests, where a dual-arm robot executes the planned paths manipulating several DLOs with different mechanical properties. Finally, the method is exploited to execute a wire harness assembly task.