Design and kinematic modeling of a concentric wire-driven mechanism targeted for minimally invasive surgery

In this paper, a concentric wire-driven mechanism (CWM) is presented. The CWM comprises of two nested wire-driven mechanisms (WDM). Each WDM contains a flexible backbone and a set of wires. The backbone bending is controlled by pulling the wires. The stiffness of the outer WDM is controllable and dominants that of the overlapped section. Therefore, in the overlapped section the inner WDM conforms to the shape of the outer WDM and the tip of the outer WDM serves as the base of the distal separate section of the inner WDM. Compared with conventional flexible mechanisms, i.e., tendon/wire/cable-driven mechanism and concentric tube mechanism, the CWM has a much wider workspace. This advantage is demonstrated by simulations based on kinematic modeling. A prototype is developed and the preliminary experimental results validate the design concept.