Department of Informatics

Progress Report: Path Planning of

Soft Manipulator

Ahmad Ataka Awwalur Rizqi

June 30, 2015

KING’S COLLEGE LONDON, DEPARTMENT OF INFORMATICS

Progress Report: Path Planning of SoftManipulator

Ahmad Ataka Awwalur Rizqi

July 1, 2015

1 PROJECT DESCRIPTION

The research will be focused on the real-time path planning and navigation strategy ofmulti section continuum manipulator in the cluttered dynamic environment for surgicalapplication.

2 PROPOSED RESEARCH QUESTION AND METHODOLOGY

Nowadays, the continuum manipulator, largely inspired by an octopus arm, has gainedmuch popularity in the field of robotics. The flexibility of the manipulator, compared to thestandard rigid manipulator, becomes one major reason behind its popularity. Researchersin recent years tried to implement the continuum manipulator in the field which mightpose high risk if handled by the rigid manipulator, such as surgery and other medical-related problems. However, although the robot’s ability to bend at any point along thebackbone makes it particularly safer to be used in the medical field, the automation is stillneeded to ensure safety. The need of the autonomous continuum manipulator which hasan ability to move around an unknown and dynamic environment automatically to reachcertain predefined goal is vital, especially in the surgical process.The idea of continuum robot started in Anderson and Horn’s work back in 1960s [5], butit was not developed further until the beginning of 1990s when Chirikjian proposed thekinematics and dynamics model of the hyper-redundant manipulators [6] and Hirose anal-ysed the movement of snake-like robots based on the real snake [7]. In the last decade,

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Figure 2.1: Three segments STIFF-FLOP manipulators.

the continuum robot design has been implemented in several works such as an octopusarm robot OctArm [8], a soft worm-like robot Meshworm [9], a caterpillar-inspired GoQBot[10], NASA’s minimally invasive for in-space-inspection Tendril [11], and snake-arm OCRobotics [12]. Works on the kinematic modeling, Jacobian, dynamic modeling, and controlof continuum manipulator start to appear as reported in Webster’s review [13]. However,works on continuum manipulator’s navigation is still very limited, largely because of itscomplexity and uncertainty in its dynamic modeling.One recent work on continuum manipulator’s path planning is reported in Duindam’s work[14]. He proposed simple and fast geometrical inverse kinematic solution of a constant-curvature steerable needle to do a path planning. However, this work is designed specif-ically to produce control input for the steerable needle and only suitable for static kine-matics model of other continuum manipulators. This method also can’t be used to dealwith the dynamic environment with an unknown obstacle for it needs a global coordinateof environment to do obstacle avoidance. Other work by Duindam [15] which incorporatesoptimization to avoid obstacle also suffers from the same drawback.To design robust, reliable, and fast navigation strategy for continuum manipulator, wecan modify similar well-established works on rigid body counterparts. One of the popu-lar works on this field is to use artificial potential field firstly introduced by Khatib [1]. Inthis method, the manipulator is treated as a point in the configuration space C filled withartificial field which can attract the system to a desired goal configuration while avoidingobstacle in C-Space. It is largely used in several applications such as rigid manipulator,highly-redundant manipulator, mobile robot, and formation control because of its sim-plicity, elegance, and straightforward way. Although the algorithm does not ensure globalconvergence which makes it suffer from local minima, the global map of environment isnot needed and hence, it can be used for dynamic and unknown environments. However,the availability of global map if possible can be easily combined with this local method tosolve local minima and even optimize the path.One of the artificial potential field applications for continuum robot is the one used by DiMaio [3] to plan the movement of steerable needle in soft tissue. He computes the potentialfield in workspace and converts it to the needle’s C-Space by means of inverse Jacobian.However, he does not mention the way to detect the obstacle or sense the environment.Other works reported by Godage [16] incorporates the way to detect the obstacle by means

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Figure 3.1: RViz Simulator showing the environment of Continuum manipulators with dy-namic obstacles around.

of modelled sensor embedded in the backbone of multi section continuum arm and alsoexploits the null space of the highly redundant model based on Maciejewski’s work for kine-matically redundant manipulator. Although does not specifically use the terms "potentialfield", Godage’s work can be further improved and combined with more sophisticated po-tential function.The research will be focused on how to construct path planning and navigation strategy formulti section continuum manipulator. The researcher will try to combine a global and localapproach to construct the free-obstacle path from initial configuration to the final config-uration. This local planner is important to enable the manipulator to move autonomouslyin the cluttered and dynamic environment. The global planner is designed to exploit theglobal map if available, to ensure the manipulator moves in the optimum path and avoidlocal minima problem. The overall strategy will be implemented in the STIFF-FLOP ma-nipulators in Figure 2.

3 PROGRESS

During this months, I have read a lot of literatures about continuum manipulators as wellas robotics path planning in general, both from the papers and the classic literatures suchas Latombe’s Robot Motion Planning and the more recent Choset’s Principles of Robot Mo-tion. In the software side, I have already built the path planning environment for con-tinuum manipulators using the constant-curvature kinematics model via MATLAB, RobotOperating System, and R-Viz Simulator. The system built on MATLAB is useful to do prelim-inary test of the algorithm. The simulator in ROS and R-Viz enable me to test local planneralgorithm such as the potential field in real-time.The user can specify target point and move point of obstacles around the robot using joy-stick and observe the movement of the manipulator in the simulator. It also supports data-recording to be analysed further. The codes were written in C++ and python. In the hard-ware side, I also tested the ROS-Matlab bridge such that it will be easier to send the resultproduced by MATLAB code directly to the ROS-compatible hardware. The communication

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Figure 3.2: Simple Obstacle Avoidance for Three Segment Continuum Manipulators.

was tested in the STIFF-FLOP manipulators and can be used in the future if needed.Besides, I also took some courses as follows:

• Leadership Skills for Research Students

• Writing for Publication

4 PROBLEMS AND ISSUES

One obvious issue is the fact that STIFF-FLOP manipulator does not have proximity sensorsused to measure the distance to the surrounding environment. This information is neededto detect unknown and dynamic obstacles and avoiding them using the potential-field-based local planner. Other issue is possibly the limited number of Aurora tracker as well asits magnetic field generator. The sensor is needed to estimate the continuum manipulator’spose. The fact that many students and research associates also use the sensors will evencomplicate things.About the proximity sensors, I will try to focus on the implementation of the algorithmitself, with the assumption that the global map is available. Hence, the availability of thesensors is not urgent now. However, the availability of the sensors in the future will openthe possibility to investigate the path planning with uncertainty. Concerning the Aurora, itwill be useful to have schedule on when everybody will use the sensors such that it will beeasier for each student to organize their experiment plan.

5 FUTURE PLAN

Since the ROS-based-simulation is ready, I will try to implement several types of potential-field-based planner in the constant-curvature continuum manipulators. I will also imple-ment several techniques on how to deal with the redundancy of the system, mainly derivedfrom the techniques used in the hyper-redundant manipulator. Several types of potentialfield and redundancy-exploiter technique will be compared in the simulation and will befinished by the end of June.

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REFERENCES

[1] Oussama Khatib, Real-time Obstacle Avoidance for Manipulators and Mobile Robots,Proceedings 1985 IEEE International Conference on Robotics and Automation, vol.2,no., pp.500,505, Mar 1985

[2] Robert J Webster and Bryan A. Jones, Design and Kinematic Modeling of Constant Cur-vature Continuum Robots: A Review, The International Journal of Robotics Research,November 2010; vol. 29, 13: pp. 1661-1683., first published on June 10, 2010.

[3] DiMaio, S.P.; Salcudean, S.E, Needle steering and motion planning in soft tissues,, IEEETransactions on Biomedical Engineering, vol.52, no.6, pp.965,974, June 2005.

[4] Anthony A. Maciejewski and Charles A. Klein, Obstacle Avoidance for Kinematically Re-dundant Manipulators in Dynamically Varying Environments, The International Jour-nal of Robotics Research, September 1985; vol. 4, 3: pp. 109-117.

[5] Anderson, V. and Horn, R, (1967). Tensor arm manipulator design. ASME Transactions,67-DE-57(2): 1-12.

[6] Gregory S. Chirikjian, 1992. Theory and Application of Hyper-redundant Robotic Ma-nipulators. PhD Thesis. Department of Applied Mechanics, California Institute of Tech-nology,

[7] Hirose, S. (1993). Biologically Inspired Robots, Snake-Like Locomotors and Manipula-tors. Oxford, Oxford University Press.

[8] McMahan, W.; Chitrakaran, V.; Csencsits, M.; Dawson, D.; Walker, I.D.; Jones, B.A.;Pritts, M.; Dienno, D.; Grissom, M.; Rahn, C.D., "Field trials and testing of the Oc-tArm continuum manipulator," Robotics and Automation, 2006. ICRA 2006. Proceed-ings 2006 IEEE International Conference on , vol., no., pp.2336,2341, 15-19 May 2006

[9] Sangok Seok; Onal, C.D.; Kyu-Jin Cho; Wood, R.J.; Rus, D.; Sangbae Kim, "Meshworm: APeristaltic Soft Robot With Antagonistic Nickel Titanium Coil Actuators," Mechatronics,IEEE/ASME Transactions on , vol.18, no.5, pp.1485,1497, Oct. 2013

[10] Huai-Ti Lin, Gary G Leisk, Barry Trimmer. (2011) GoQBot: a caterpillar-inspired soft-bodied rolling robot. Bioinspiration and Biomimetics 6026007.

[11] Mehling, J.S.; Diftler, M.A.; Chu, M.; Valvo, M., "A Minimally Invasive Tendril Robot forIn-Space Inspection," Biomedical Robotics and Biomechatronics, 2006. BioRob 2006.The First IEEE/RAS-EMBS International Conference on , vol., no., pp.690,695, 20-22Feb. 2006

[12] R. Buckingham. "Snake arm robots". Industrial Robot International Journal. 29(3),242-245 (2002)

[13] Webster, Robert J and Jones, Bryan A. "Design and Kinematic Modeling of ConstantCurvature Continuum Robots: A Review". The International Journal of Robotics Re-search. 2010.

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[14] Duindam, V.; Xu, J.; Alterovitz, R.; Sastry, S. and Goldberg, K. Y. (2010), ’Three-dimensional Motion Planning Algorithms for Steerable Needles Using Inverse Kinemat-ics.’, I. J. Robotic Res. 29 (7) , 789-800 .

[15] Duindam, Vincent; Alterovitz, R.; Sastry, S.; Goldberg, K., "Screw-based motionplanning for bevel-tip flexible needles in 3D environments with obstacles," Roboticsand Automation, 2008. ICRA 2008. IEEE International Conference on , vol., no.,pp.2483,2488, 19-23 May 2008

[16] Godage, I.S.; Branson, D.T.; Guglielmino, E.; Caldwell, D.G., "Path planning for mul-tisection continuum arms," Mechatronics and Automation (ICMA), 2012 InternationalConference on , vol., no., pp.1208,1213, 5-8 Aug. 2012

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