New Jersey Institute of Technology Digital Commons @ NJIT Dissertations Theses and Dissertations Spring 2016 A novel approach to user controlled ambulation of lower extremity exoskeletons using admittance control paradigm Kiran Kartika Karunakaran New Jersey Institute of Technology Follow this and additional works at: https://digitalcommons.njit.edu/dissertations Part of the Biomedical Engineering and Bioengineering Commons Recommended Citation Karunakaran, Kiran Kartika, "A novel approach to user controlled ambulation of lower extremity exoskeletons using admittance control paradigm" (2016). Dissertations. 71. https://digitalcommons.njit.edu/dissertations/71 This Dissertation is brought to you for free and open access by the Theses and Dissertations at Digital Commons @ NJIT. It has been accepted for inclusion in Dissertations by an authorized administrator of Digital Commons @ NJIT. For more information, please contact [email protected]. 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Please Note: The author retains the copyright while the New Jersey Institute of Technology reserves the right to distribute this thesis or dissertation Printing note: If you do not wish to print this page, then select “Pages from: first page # to: last page #” on the print dialog screen The Van Houten library has removed some of the personal information and all signatures from the approval page and biographical sketches of theses and dissertations in order to protect the identity of NJIT graduates and faculty. ABSTRACT A NOVEL APPROACH TO USER CONTROLLED AMBULATION OF LOWER EXTREMITY EXOSKELETONS USING ADMITTANCE CONTROL PARADIGM by Kiran Kartika Karunakaran The robotic lower extremity exoskeletons address the ambulatory problems confronting individuals with paraplegia. Paraplegia due to spinal cord injury (SCI) can cause motor deficit to the lower extremities leading to inability to walk. Though wheelchairs provide mobility to the user, they do not provide support to all activities of everyday living to individuals with paraplegia. Current research is addressing the issue of ambulation through the use of wearable exoskeletons that are pre-programmed. There are currently four exoskeletons in the U.S. market: Ekso, Rewalk, REX and Indego. All of the currently available exoskeletons have 2 active Degrees of Freedom (DOF) except for REX which has 5 active DOF. All of them have pre-programmed gait giving the user the ability to initiate a gait but not the ability to control the stride amplitude (height), stride frequency or stride length, and hence restricting users’ ability to navigate across different surfaces and obstacles that are commonly encountered in the community. Most current exoskeletons do not have motors for abduction or adduction to provide users with the option for movement in coronal plane, hence restricting user’s ability to effectively use the exoskeletons. These limitations of currently available pre-programmed exoskeleton models are sought to be overcome by an intuitive, real time user-controlled control mechanism employing admittance control by using hand-trajectory as a surrogate for foot trajectory. Preliminary study included subjects controlling the trajectory of the foot in a virtual environment using their contralateral hand. The study proved that hands could produce trajectories similar to human foot trajectories when provided with haptic and visual feedback. A 10 DOF 1/2 scale biped robot was built to test the control paradigm. The robot has 5 DOF on each leg with 2 DOF at the hip to provide flexion/extension and abduction/adduction, 1 DOF at the knee to provide flexion and 2 DOF at the ankle to provide flexion/extension and inversion/eversion. The control mechanism translates the trajectory of each hand into the trajectory of the ipsilateral foot in real time, thus providing the user with the ability to control each leg in both sagittal and coronal planes using the admittance control paradigm. The efficiency of the control mechanism was evaluated in a study using healthy subjects controlling the robot on a treadmill. A trekking pole was attached to each foot of the biped. The subjects controlled the trajectory of the foot of the biped by applying small forces in the direction of the required movement to the trekking pole through a force sensor. The algorithm converted the forces to Cartesian position of the foot in real time using admittance control; the Cartesian position was converted to joint angles of the hip and knee using inverse kinematics. The kinematics, synchrony and smoothness of the trajectory produced by the biped robot was evaluated at different speeds, with and without obstacles, and compared with typical walking by human subjects on the treadmill. Further, the cognitive load required to control the biped on the treadmill was evaluated and the effect of speed and obstacles with cognitive load on the kinematics, synchrony and smoothness was analyzed. A NOVEL APPROACH TO USER CONTROLLED AMBULATION OF LOWER EXTREMITY EXOSKELETONS USING ADMITTANCE CONTROL PARADIGM by Kiran Kartika Karunakaran A Dissertation Submitted to the Faculty of New Jersey Institute of Technology and Rutgers-The State University of New Jersey in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Biomedical Engineering Joint Program in Biomedical Engineering May 2016 Copyright © 2016 by Kiran Kartika Karunakaran ALL RIGHTS RESERVED . APPROVAL PAGE A NOVEL APPROACH TO USER CONTROLLED AMBULATION OF LOWER EXTREMITY EXOSKELETONS USING ADMITTANCE CONTROL PARADIGM Kiran Kartika Karunakaran Dr. Richard Foulds, Dissertation Advisor Date Associate Professor of Biomedical Engineering, New Jersey Institute of Technology Dr. Sergei Adamovich, Committee Member Date Associate Professor of Biomedical Engineering, New Jersey Institute of Technology Dr. Eugene Tunik, Committee Member Date Associate Professor of Rehabilitation and Movement Sciences Rutgers, The State University of New Jersey Dr. Gerard Fluet, Committee Member Date Assistant Professor of Rehabilitation and Movement Sciences, Rutgers, The State University of New Jersey Dr. Gail Forrest, Committee Member Date Assistant Professor of Neuroscience, Rutgers, The State University of New Jersey BIOGRAPHICAL SKETCH Author: Kiran Kartika Karunakaran Degree: Doctor of Philosophy Date: May 2016 Undergraduate and Graduate Education: Doctor of Philosophy, Biomedical Engineering; New Jersey Institute of Technology, May 2016 Master of Science, Electrical and Computer Engineering; New Jersey Institute of Technology, January 2006 Bachelor of Engineering, Electrical and Electronics Engineering; Annamalai University, May 2005 Major: Biomedical Engineering Presentations and Publications: Karunakaran, Kiran, Kevin Abbruzzese, Hao Xu, Naphtaly Ehrenberg, and Richard Foulds. "Haptic Proprioception in a Virtual Locomotor Task." In Engineering in Medicine and Biology Society (EMBC), 2014 36th Annual International Conference of the IEEE, pp. 3594-3597. IEEE, 2014. Karunakaran, Kiran K., and Richard Foulds. "Control of Foot Trajectory in Biped Robots." In Bioengineering Conference (NEBEC), 2013 39th Annual Northeast, pp. 203-204. IEEE, 2013. Abbruzzese,Kevin, Kiran Karunakaran, Hao Xu, Naphtaly Ehrenberg, and Richard Foulds.A 1-DOF Admittance Control Hand Exoskeleton for Grasp. In Engineering in Medicine and Biology Society (EMBC), 2014 36th Annual International Conference of the IEEE. IEEE, 2014. Agas, A.M.; Daitol, A.A.; Shah, U.B.; Fraser, L.J.; Abbruzzese, K.M.; Karunakaran, K.K.; Foulds, R., "3-DOF Admittance Control Robotic Arm with a 3D Virtual Game for facilitated training of the hemiparetic hand," iv In Biomedical Engineering Conference (NEBEC), 2015 41st Annual Northeast , vol., no., pp.1-2, 17-19 April 2015. v This dissertation is lovingly dedicated to my family, who has been with me through thick and thin. Everyone in the family pitched in to help in the best possible each of them can. Undoubtedly this dissertation wouldn’t have been possible but for the continued support, love and counsel of my father, Bala Chandra Karunakaran. To my sister, Keerthana Karunakaran, my best cheerleader who also loyally played the role of test pilot in my protocols (protocol was approved by IRB and she was not harmed in anyway). To my mother, Kasthuri Karunakaran and grandmother, Kunjammal who showed their love and support in the best way they know, by sending me some of the best home-made health foods across the ocean at every chance they got. To my grandfather Subramaniam and my late grandmother Janaki, I wouldn’t be where I am without you; I owe it all to you both. I am also thankful to all my friends who supported me throughout these years. Of course, I am also thankful to my extended family for all their affection and encouragement.