Article

Stiffness Control of Surgical Continuum Manipulators.

Med. Sch., Cardiac Surg. Dept., Harvard Univ., West Roxbury, MA, USA
IEEE Transactions on Robotics (Impact Factor: 2.65). 04/2011; 27:334-345. DOI: 10.1109/TRO.2011.2105410
Source: DBLP

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.

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    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. DOI:10.1109/TRO.2014.2309194 · 2.65 Impact Factor
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    • "Recently, the theory of Cosserat rod has been used to model backbones in large deflections.[21] [22] [23] [24] This theory is used to modelone-dimensional flexible objects, such as rope, wire, cable, and slender rods.[25] Although this model is accurate, it has been used not often, because of its massive numerical calculations. "
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    • "The Cosserat theory has been used for exact modeling of continuum robots, in all cases, such as spatial modeling of backbone [10], modeling actuation system [11], modeling in planar cases [12], surgical manipulators [13] and concentric tubes [14] [15]. "
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