DOF minimization for optimized shape control under active constraints for a hyper-redundant flexible robot

Abstract

In robotic-assisted minimally invasive surgery, there are increasing interests in the use of articulated hyper-redundant robots to provide enhanced flexibility to conform to complex anatomical pathways without the constraint of accurate port placement. However, as the number of joints to be simultaneously actuated increases, so too does the complexity of the control architecture and the computational power required to integrate techniques such as adaptive force control and haptic feedback. In this paper, we propose a degree-of-freedom (DOF) minimization scheme for simplifying the control of a generic hyper-redundant articulated robot by identifying the minimum number of joints required to perform a specific task without compromising workspace limits. In particular, a time-varying instrument path is defined for realistic, in vivo settings involving tissue deformation. The minimum number of DOF is determined by the amount of angular displacement of the joints to ensure shape conformance and seamless trajectory manipulation. Dynamic active constraints are also imposed on the entire length of the flexible robot. Detailed simulation and preliminary experimental results are provided to demonstrate the practical application of the proposed framework. © 2011 Springer-Verlag.