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1、Confi guration and Joint Feedback for Enhanced Performance of Multi Segment Continuum Robots Andrea Bajo Roger E Goldman and Nabil Simaan Abstract Multi segment continuum robots offer enhanced safety during surgery due to their inherent passive compliance However they suffer poor position tracking p
2、erformance due to fl exibility of their actuation lines structural compliance and actuation coupling effects between segments The need for control methods addressing accurate tracking for multi segment continuum robots is magnifi ed by increased precision requirements of surgical procedures employin
3、g these structures To address this need this paper proposes a tiered controller that uses both extrinsic and intrinsic sensory information for improved performance of multi segment continuum robots The higher tier of this controller uses confi guration space feedback while the lower tier uses joint
4、space feedback and a feed forward term obtained with actuation compensation techniques We prove the stability of this controller using Lyapunov s direct method and experimentally evaluate its performance on a three segment multi backbone continuum robot Results demonstrate its effi cacy in enhancing
5、 regulation and tracking performance It is shown that the controller mitigates the effects of actuation coupling be tween robot s sub segments and decreases phase lag These results suggest that this tiered controller will enhance telemanipulation performance of multi segment continuum robots I INTRO
6、DUCTION In the past decade continuum robots gained popularity in the medical robotics community for their dexterity and innate compliance These devices address a growing need to reach deeper into the human anatomy while minimizing or eliminating skin incisions The development of new surgical paradig
7、ms such as Minimally Invasive Surgery MIS in deep surgical fi elds and Natural Orifi ce Transluminal Endoscopic Surgery NOTES emphasize this need Current designs of continuum robots that provide deep access into the human body continue to present new theoretical and practical chal lenges These desig
8、ns include wire actuated articulated robots 1 and 2 passively fl exible stems with wire actuated wrists 3 rigid fl exible locking access sheaths 4 7 steerable robots 8 10 and multi backbone continuum robots 11 and Fig 1 These robotic slaves offer advantages in terms of miniaturization while supporti
9、ng multiple applications 12 and 13 However they require novel control algorithms in order to meet the desired accuracy The lack of accuracy is due to friction extension and torsion of their actuation lines shape discrepancy from nominal kinematics and actuation coupling between segments This work wa
10、s supported by NSF Career grant IIS 0844969 A Bajo and N Simaan are with the Departmentof Mechanical Engineering Vanderbilt University Nashville TN 37212 USA e mail andrea bajo nabil simaan vanderbilt edu R E GoldmaniswiththeDepartmentofBiomedicalEngi neering ColumbiaUniversity NewYork NY10027 USA e
11、 mail reg2117 columbia edu corresponding author Fig 1 The experimental setup consist of a nine axis actuation unit a 3 segment continuum robot a magnetic fi eld generator and four magnetic sensors attached to the robot s base 0 the end disk of the fi rst segment 1 the end disk of the second segment
12、2 and robot s end effector 3 The theoretical foundations of kinematics and dynamics of continuum robots are built upon the work on hyper redundant robots by Chirikjian and Burdick 14 16 Previous works on control of continuum robots include the work of Gravagne and Walker 17 on asymptotic regulation
13、for wire actuated continuum segments the work of Webster et al on kinematics and visual servoing for concentric tube robots 18 and the work of Dupont et al on design and control of concentric tube robots 19 Several other researchers focused on overcoming fl exibilities friction backlash and hysteres
14、is in continuum robots For example Xu and Simaan 20 presented a model based recursive estimation framework that uses extrinsic mea surements of the end effector orientation for multi backbone continuumsegments Simaan et al 12 extended this approach to multi segment multi backbone continuum robots us
15、ing a hybrid approach The nominal parameters of the robot were corrected based on joint space information for each segment of a multi segment robot Additional coupling effects between segments were overcome by confi guration space compensa tion Agrawal et al 21 designed a feed forward smooth backlas
16、h inverse and a recursive estimator for unknown pa rameters in wire actuated robots Kesner and Howe 22 used 2011 IEEE International Conference on Robotics and Automation Shanghai International Conference Center May 9 13 2011 Shanghai China 978 1 61284 385 8 11 26 00 2011 IEEE2905 a model based actuation compensation technique in bowden wire actuated catheters Camarillo et al 23 used vision feedback with wire actuated multi segment catheters Croom et al 24 investigated the use of self organizedma
