Article

Stiffness Control of Surgical Continuum Manipulators.

Med. Sch., Cardiac Surg. Dept., Harvard Univ., West Roxbury, MA, USA
IEEE Transactions on Robotics (Impact Factor: 2.57). 01/2011; 27:334-345. DOI: 10.1109/TRO.2011.2105410
Source: IEEE Xplore

ABSTRACT 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.

0 Bookmarks
 · 
98 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: A position/force hybrid control system based on impedance control scheme is designed to align a small gripper to a special ring object. The vision information provided by microscope vision system is used as the feedback to indicate the position relationship between the gripper and the ring object. Multiple image features of the gripper and the ring object are extracted to estimate the relative positions between them. The end-effector of the gripper is tracked using the extracted features to keep the gripper moving in the field of view. The force information from the force sensor serves as the feedback to ensure that the contact force between the gripper and the ring object is limited in a small safe range. Experimental results verify the effectiveness of the proposed control strategy.
    International Journal of Automation and Computing 08/2013; 10(4):360-367.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Continuum manipulators offer a means for robot ma-nipulation in a constrained environment, where the manipulator body can safely interact with, comply with, and navigate around obstacles. However, obstacle interactions impose constraints that conform the robot body into arbitrary shapes regardless of ac-tuator positions. Generally, these effects cannot be wholly sensed on a continuum manipulator and, therefore, render model-based controllers incorrect, leading to artificial singularities and unstable behavior. We present a task-space closed-loop controller for contin-uum manipulators that does not rely on a model and can be used in constrained environments. Using an optimal control strategy on a tendon-driven robot, we demonstrate this method, which we term model-less control, which allows the manipulator to interact with several constrained environments in a stable manner. To the best of our knowledge, this is the first work in controlling continuum manipulators without using a model.
    IEEE Transactions on Robotics 08/2014; 30(4):880-888. · 2.57 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Most devices for single-site or natural orifice transluminal surgery are very application specific and, hence, capable of effectively carrying out specific surgical tasks only. However, most of these instruments are rigid, lack a sufficient number of degrees of freedom (DOFs), and/or are incapable of modifying their mechanical properties based on the tasks to be performed. The current philosophy in commercial instrument design is mainly focused on creating minimally invasive surgical systems using rigid tools equipped with dexterous tips. Only few research efforts are aimed at developing flexible surgical systems, with many DOFs or even continuum kinematics. The authors propose a radical change in surgical instrument design: away from rigid tools toward a new concept of soft and stiffness-controllable instruments. Inspired by biology, we envision creating such soft and stiffness- controllable medical devices using the octopus as a model. The octopus presents all the capabilities requested and can be viewed as a precious source of inspiration. Several soft technologies are suitable for meeting the afore- mentioned capabilities, and in this article a brief review of the most promising ones is presented. Then we illustrate how specific technologies can be applied in the design of a novel manipulator for flexible surgery by discussing its potential and by presenting feasibility tests of a prototype responding to this new design philosophy. Our aim is to investigate the feasibility of applying these technologies in the field of minimally invasive surgery and at the same time to stimulate the creativeness of others who could take the proposed concepts further to achieve novel solutions and generate specific application scenarios for the devised technologies.
    Soft Robotics. (SoRo). 06/2014;

Full-text

View
5 Downloads
Available from