Stiffness Control of Surgical Continuum Manipulators

Med. Sch., Cardiac Surg. Dept., Harvard Univ., West Roxbury, MA, USA
IEEE Transactions on Robotics (Impact Factor: 2.43). 04/2011; 27(2):334-345. DOI: 10.1109/TRO.2011.2105410
Source: DBLP


This paper introduces the first stiffness controller for continuum robots. The control law is based on an accurate approx- imation of a continuum robot's coupled kinematic and static force model. To implement a desired tip stiffness, the controller drives the actuators to positions corresponding to a deflected robot con- figuration that produces the required tip force for the measured tip position. This approach provides several important advantages. First, it enables the use of robot deflection sensing as a means to both sense and control tip forces. Second, it enables stiffness con- trol to be implemented by modification of existing continuum robot position controllers. The proposed controller is demonstrated ex- perimentally in the context of a concentric tube robot. Results show that the stiffness controller achieves the desired stiffness in steady state, provides good dynamic performance, and exhibits stability during contact transitions.

Download full-text


Available from: Pierre E Dupont, Jul 06, 2015
  • Source
    • "For more complicated tasks such as retraction or grasping, the manipulator also needs to be able to modulate its stiffness and thus actively exert a force when necessary; for example, for lifting and supporting an organ. The need for stiffness control in robots presenting a continuum or soft structure has been addressed in[22], where a stiffness controller based on the kinematics of robots is presented. A step further is proposed in[23], where the issue of monitoring the contact with a compliant environment is addressed. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents the concept design of a modular soft manipulator for minimally invasive surgery. Unlike traditional surgical manipulators based on metallic steerable needles, tendon driven mechanisms, or articulated motorized links, we combine flexible fluidic actuators to obtain multidirectional bending and elongation with a variable stiffness mechanism based on granular jamming. The idea is to develop a manipulator based on a series of modules, each consisting of a silicone matrix with pneumatic chambers for 3-D motion, and one central channel for the integration of granular-jamming-based stiffening mechanism. A bellows-shaped braided structure is used to contain the lateral expansion of the flexible fluidic actuator and to increase its motion range. In this paper, the design and experimental characterization of a single module composed of such a manipulator is presented. Possible applications of the manipulator in the surgical field are discussed.
    Full-text · Article · Jan 2016 · IEEE Transactions on Robotics
  • Source
    • "To achieve the best aspects of rigid and compliant structures in a single robot, actuation strategies for effectively modulating manipulator stiffness have been the subject of several recent research efforts. Active model-based impedance control using sensor measurements of actuator force and robot deflection has also been shown to address the compliance/strength tradeoff from a higher level control framework [99], [100], but flexibility may still limit the maximum force the robot can apply. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we describe the state of the art in continuum robot manipulators and systems intended for application to interventional medicine. Inspired by biological trunks, tentacles, and snakes, continuum robot designs can traverse confined spaces, manipulate objects in complex environments, and conform to curvilinear paths in space. In addition, many designs offer inherent structural compliance and ease of miniaturization. After decades of pioneering research, a host of designs have now been investigated and have demonstrated capabilities beyond the scope of conventional rigid-link robots. Recently, we have seen increasing efforts aimed at leveraging these qualities to improve the frontiers of minimally invasive surgical interventions. Several concepts have now been commercialized, which are inspiring and enabling a current paradigm shift in surgical approaches toward flexible access routes, e.g., through natural orifices such as the nose. In this paper, we provide an overview of the current state of this field from the perspectives of both robotics science and medical applications. We discuss relevant research in design, modeling, control, and sensing for continuum manipulators, and we highlight how this work is being used to build robotic systems for specific surgical procedures. We provide perspective for the future by discussing current limitations, open questions, and challenges.
    Full-text · Article · Nov 2015 · IEEE Transactions on Robotics
  • Source
    • "While position control of such flexible robots has been well covered in the current state-of-the-art, the attention to force control has been scarce. Examples of force control for continuum robots include the stiffness control presented in [15] and force control for single DoF(degrees of freedom) catheter [13]. The aforementioned approaches have limited flexibility with respect to the capability of describing task objectives in terms of constraints to be enforced on pose and force of the tool (and other robot links) such as no-go zones, entry-point or trocar constraints, force references and limits, etc, that often arise in surgical scenarios. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper introduces a framework for constraint-based force/position control of robots that exhibit large nonlinear structural compliance and that undergo large deformations. Controller synthesis follows hereto the principles of the Task Frame and instantaneous Task Specification using Constraints (iTaSC) formalisms. iTaSC is found particularly suitable due to its ability to express and combine control tasks in a natural way. Control tasks can be formulated as combinations of target positions, velocities, or forces expressed in an arbitrary number and type of coordinate frames. The proposed framework is applied to a mixed mechatronic system composed of a traditional rigid-link robot whose end-effector is a continuum (flexible) link. A selection of different position/force control tasks is prepared to demonstrate the validity and general nature of the proposed framework.
    Full-text · Article · Oct 2015 · IEEE Transactions on Robotics
Show more