Reconfigurable Continuous Track Robot (RCTR)
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BEN-GURION UNIVERSITY OF THE NEGEV THE FACULTY OF ENGINEERING SCIENCES DEPARTMENT OF MECHANICAL ENGINEERING Reconfigurable Continuous Track Robot (RCTR) THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE M.Sc. DEGREE By: Tal Kislassi Supervised by: Dr. David Zarrouk September 2019 September 2019 BEN-GURION UNIVERSITY OF THE NEGEV THE FACULTY OF ENGINEERING SCIENCES DEPARTMENT OF MECHANICAL ENGINEERING Reconfigurable Continuous Track Robot (RCTR) THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE M.Sc. DEGREE By: Tal Kislassi Supervised by: Dr. David Zarrouk Author: Tal Kislassi Date: 26.9.2019 Supervisor: David Zarrouk Date: 26.9.2019 Chairman of graduate studies committee: ______________ Date: ____________23.12.19 September 2019 Abstract This research presents a minimally actuated Reconfigurable Continuous Track Robot (RCTR). The RCTR can change its geometry while advancing, thus enabling it to crawl and climb over different terrains and obstacles. The robot is fitted with a regular propulsion motor similar to a regular track and has a locking mechanism located at the front. The links have a unique design which allows them to be locked at a relative orientation of negative 20, 0, and positive 20 degrees to each other as they reach the front of the robot. A release mechanism, located at the back, passively unlocks the links. As a result, all the links in the lower part are locked whereas the top links are unlocked. First, a review of the crawling and reconfigurable robot will be presented, Followed by an explanation of the main concept and a description of design demands and requirements. It is important to note there have been several attempts to design this robot, but all failed. Next, we present the design of the robot and its mechanisms. The links of the closed loop continuous track, its’ main body with its mechanisms and the electronic parts are described. The robot was assembled by 3-D printed parts and additional elements that we ordered to complete the building process. Motors, batteries and a receiver were installed on the main body of the robot. The robot's performance was in line with expectations and all the mechanisms interacted properly with one another. Then, we created a kinematic and dynamic model of the robot’s movement and simulated the different obstacles that the robot can overcome. A quasistatic - ii - model of the robot was developed to examine its behavior while climbing over different obstacles and slopes. The model was integrated in a MATLAB simulation which displayed the robot's movement in real time and allowed the user to control the RTCR while examining its behavior. The simulation provided substantial data regarding the robot's ability to overcome various obstacles different in shape and difficulty. Lastly, we presented multiple experiments showing how this new robot can successfully navigate different obstacles. The experiments showed that the robot is capable of overcoming obstacles as the simulation predicted including climbing a high step, skipping an obstacle without touching it and passing a gap more than half of its length. Also, we have tested the robot in outdoor environments and proved that the robot can successfully crawl on challenging surfaces such as rocks, sand and grass. Key Words Robotics; Crawling Robot; Mechanical Design; Reconfigurable Robot; Rolling Motion; Motion modeling; - iii - Acknowledgments First, I would like to express my gratitude to my supervisor, Dr. David Zarrouk, for the guidance and encouragement during my research and thesis writing. I would like to thank him for all the support, patient advice and the trust he placed in me. A special thanks goes to my dear friends and colleagues, Lior Navon and Bar Keshet, for their collaboration and brain-storming on a daily basis, which made my work much more productive and a lot more fun than I thought it could ever be. I would also like to thank my friends and fellow Master's students for their support, the shared meals and laughter during our time on and off campus grounds. Finally, I would like to thank my family for loving and supporting me and for providing me with continuous encouragement throughout my years of studying and throughout the research process and the thesis writing. - iv - Table of Contents Nomenclature ......................................................................................................... vi List of Tables ......................................................................................................... vii List of Figures ....................................................................................................... vii 1 Introduction ..................................................................................................... 1 2 Background ..................................................................................................... 5 3 Design and Manufacturing .............................................................................. 9 3.1 Product Design Specifications ............................................................... 10 3.2 Robot Design ......................................................................................... 10 3.2.1 The Track Links and Locking Mechanism........................................ 10 3.2.2 The Main Body .................................................................................. 14 3.2.3 Advancing Mechanism ...................................................................... 15 3.2.4 Lock and Releasing Mechanism ....................................................... 15 3.3 Actuating and Control ............................................................................ 18 3.4 Manufacturing ........................................................................................ 18 4 Kinematics and Dynamic Analysis ............................................................... 20 4.1 Kinematic Analysis ................................................................................ 20 4.2 Position and Mobility of the Center of Mass ......................................... 21 4.3 The Maximum Height that the Robot Can Overcome ........................... 22 4.4 Torque Analysis ..................................................................................... 23 5 Simulations ................................................................................................... 26 6 Experiments .................................................................................................. 34 6.1 Horizontal Crawling in Rigid and Flexible Configurations on Curved Surface 34 6.2 Climbing and Descending a step obstacle ............................................. 35 6.3 Skipping over Obstacles and gaps ......................................................... 37 6.4 Running Over a Variety of Surfaces ...................................................... 38 7 Conclusions ................................................................................................... 40 8 References ..................................................................................................... 41 9 Appendices .................................................................................................... 45 - v - Nomenclature Symbol Units Meaning FF N Weight of the front component mass FMB N Weight of the main body FR N Weight of the rear component mass FTTL N Weight of the top track links H Cm Hight of the robot hmax Cm Maximum theoretical height that the robot can climb L Cm Length of the robot Length of the front side of the robot which is not in Lpitch Cm contact with the ground Length from the rear side of the robot to the last joint in Lrear Cm contact with the ground LSL Cm Length of the track link LTL Cm Length of the track link m Kg Total mass of the robot MF Kg Mass of the components at the front of the robot MR Kg Mass of the components at the rear of the robot mSL Kg Mass of a support link mTL Kg Mass of a track link nTL - Number of track links nTTL - Number of top track links A matrix containing the vectors of the joint's location at S(k) Cm step k si Cm Location of the bottom track link joint i so Cm Location of the last front joint in contact with the ground Tmotors Ncm Required torque of the robot W Cm Width of the robot αmax degrees Maximum pitch angle of the robot θj degrees Angle of joint j θmax degrees Maximum angle of climbing ρ Kg/cm Mass per length of the links and the support body - vi - List of Tables Table 3.1: Specifications. ...................................................................................... 19 List of Figures Figure 1.1: Snake-like robot [23] with one motor on each link. ............................. 1 Figure 1.2: Pine caterpillar at the top left, the model of the robot at the top right and the inchworm robot [27] at the bottom. ................................................................... 2 Figure 1.3: OUROBOT [32] uses a rolling motion. (a) Shows a close loop of 12 individual links (b). A presentation of one link with a single motor out of the 12 links in the OUROBOT. .......................................................................................... 3 Figure 1.4: The RCTR is a newly developed robot that can change its external geometry as it advances. The RCTR is actuated by three motors; two motors provide the thrust and the third controls the shape. ................................................. 4 Figure 2.1: The vision of the project. .....................................................................