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A B S T R A C TContinuum robots have shown astounding abilities to assist surgeons reaching confined spaces in the human body. Thus, accurate control of these manipulators, and particularly concentric tube robots, is required in order to achieve intracorporeal microrobotic interventions. We present hereby an improvement of this kinematic structure based on embedded soft micro-actuators. Two models for single and double direction curvature control are introduced. We demonstrate that kinematics are enhanced with respect to the standard approach in terms of holonomy, actuation redundancy and workspace covering. Further kinematic analysis enables the detection of singular configurations. The number of the end-effector pose occurrences that can be reached in a given volume (one cubic millimeter) are computed as well. Finally, the advantages of the novel structures are proven using performance indices.

Abstract-This paper deals with the development of a visionbased controller for a continuum robot architecture. More precisely, the controlled robotic structure is based on threetube concentric tube robot (CTR), an emerging paradigm to design accurate, miniaturized, and flexible endoscopic robots. This approach has grown considerably in the recent years finding applications in numerous surgical disciplines. In contrast to conventional robotic structures, CTR kinematics arise many challenges for an optimal control such as friction, torsion, shear, and non-linear constitutive behavior. In fact, in order to ensure efficient and reliable control, in addition to computing an analytical and complete kinematic model, it is also important to close the control loop. To do this, we developed an eye-in-hand visual servoing scheme using a millimeter-sized camera embedded at the robot's tip.Both the kinematic model and the visual servoing controller were successfully validated in simulation with ViSP (Visual Servoing Platform) and using an experimental setup. The obtained results showed satisfactory performances for 3-degrees of freedom positioning and path following tasks with adaptive gain control.

In this paper, we provide an analytical formulation for the geometricostatic problem of continuum planar parallel robots. This formulation provides to an analytical computation of a set of equations governing the equilibrium configurations. We also introduce a stability criterion of the computed configurations. This formulation is based on the use of Kirchhoff's rod deformation theory and finite-difference approximations. Their combination leads to a quadratic expression of the rod's deformation energy. Equilibrium configurations of a planar parallel robot composed of two hinged flexible rods are computed according to this new formulation and compared with the ones obtained with state-of-the-art approaches. By assessing equilibrium stability with the proposed technique, new unstable configurations are determined.

Dexterity of robots is highly required when it comes to integration for medical applications. Major efforts have been conducted to increase the dexterity at the distal parts of medical robots. This paper reports on developments toward integrating biocompatible conducting polymers (CP) into inherently dexterous concentric tube robot paradigm. In the form of tri-layer thin structures, CP micro-actuators produce high strains while requiring less than 1 V for actuation. Fabrication, characterization, and first integrations of such micro-actuators are presented. The integration is validated in a preliminary telescopic soft robot prototype with qualitative and quantitative performance assessment of accurate position control for trajectory tracking scenarios. Further, CP micro-actuators are integrated to a laser steering system in a closed-loop control scheme with displacements up to 5 mm. Our first developments aim toward intracorporeal medical robotics, with miniaturized actuators to be embedded into continuum robots.

A novel structure of a 2 DoF telescopic soft robot using a tri-layer Polypyrrole (PPy) soft micro-actuator with deployment is presented in this paper. The kinematic model is introduced and the Position Based Visual Servo (PBVS) control with path-planning and obstacle avoidance algorithms is developed. A prototype is presented and the control schemes are validated experimentally. A satisfactory accuracy with a submillimetric positioning error is obtained namely 287.6 microns for a circular path and 210 microns for obstacle avoidance.