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Paper ThAP.55

Ryu, Hwan Taek (Hanyang University), Yi, Byung-Ju (Hanyang University), Choi, Youngjin (Hanyang University)

Natural Configuration Estimation of Elastic Wire with Consideration of Mass

Scheduled for presentation during the Poster session "Late Breaking Posters" (ThAP), Thursday, October 1, 2015, 09:45−10:00, Saal G1

2015 IEEE/RSJ International Conference on Intelligent Robots and Systems, Sept 28 - Oct 03, 2015, Congress Center Hamburg, Hamburg, Germany

This information is tentative and subject to change. Compiled on July 20, 2019

Keywords Underactuated Robots, Redundant Robots, Motion and Path Planning

Abstract

General elastic wires can be represented as continuum with uniform distribution of material. In nature, such continuum can be found in bodies of many kinds of insects, mollusk, and mammals. In biomimetic research, application of such continuum type manipulator is drawing much attention in robotics. An elastic wire or continuum body can be modelled as infinite number of links and joints connected by compliant elements. This structure is named as ‘kinematically redundant system’, where the number of input is more that the number of output. There have been quite a few researches in the area of kinematically redundant manipulator. Specially, in medical robot application, shape estimation algorithm of the flexible continuum body has been an important research topic these days. However, the previous works employed multiple sensors to estimate the configuration of the continuum body, but it is not practical approach because the size of the tool’s diameter gets larger due to attaching multiple sensors. FBG-based shape sensing approach is promising to resolve this problem. However, most of previous works were confined to small-sized flexible mechanism with small mass. Thus, the gravity load of the elastic tube was not considered in the deflection model of flexible mechanism, but it should not be ignored for some application such as the endoscope tube used for colonoscopy, which has a considerable mass. Jeon and Yi modeled the flexible endoscope as a kinematically redundant mechanism with multiple links ad joints connected by springs. The entire configuration of the flexible endoscope was estimated only by using one electromagnetic sensor with which the position and orientation information of the distal end and can be estimated. This method has advantage in that the diameter of the flexible endoscope does not get thicker by adding one sensor. By using redundancy control algorithm of mechanism, the shape prediction with consideration of mass was satisfactory. However, the effect of particular solution in the joint velocity resolution process was not deeply analyzed and thus it is prone to fall into non-optimal solution. In this paper, a new configuration estimation algorithm of elastic wire is presented which precisely estimates a natural configuration of elastic wire by minimizing the total potential energy of the system. Employing a partitioned matrix inversion technique, a weighted pseudo-inverse solution is obtained. It is found that the motion space due to elastic potential energy of the elastic wire is orthogonal to that due to gravitational potential energy. The effectiveness of the configuration estimation algorithm is proven by comparison of simulation and experiment results for several cases.

 

 

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