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Identifying a Sand Burial Technique and Designing a Robo-Physical Model Inspired from Lizards’ Motion

Kharidar, Mohammad Mahdi | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54175 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Nejat, Hossein; Narimani, Roya
  7. Abstract:
  8. Turan Toad-headed Agama is a lizard (Phrynocephalus mystaceus) inhabiting in the deserts of the Middle East. In order to hide from predators, it laterally vibrates (and slightly oscillates around the dorsal axis) to descend beneath the sand. Despite its low density, toad-headed agama easily burrows beneath the sand. The purpose of this study is to initially determine 3D kinematics of the agama's burial technique (frequency, amplitude and position of critical points of the body). After determining the motion, we will figure how the motion interacts with granular media and enables the animal to burry. This includes simulating animal's motion within granular media using discrete element method software and a robo-physical model of the animal (which is a robot mimicking animal’s motion).The lizards’ burial technique was 3D captured by two differently angled cameras pointing at it. The videos were analyzed to generate 3D plots. A simple geometrical model was drawn based on the lizard measures to be used in simulations. The simplified lizard’s motion was applied to the geometry in the simulations to validate whether we successfully discovered the technique or not.The lenses were too distorted to capture appropriate videos regarding 3D plot generation. The burial technique was mostly discovered using the slow-motion videos rather than the 3D plots. Multiple simulations were conducted to achieve a successful technique. We figured weight distribution and undulations play important roles in breaking sand’s resistance, but to fully burrow beneath the sand, extra weight had to be added to the simulated geometry.Based on the results of the simulations a rob-physical model was designed. The robot was designed in a way to do the technique with minimum complexity and degrees of freedom. The robot stands on a flap the way the lizard stands on its hands and then shakes its back to penetrate the sand. The effectiveness of the robot motion was checked using simulation. We needed to add extra weight to the robot to be able to completely burrow beneath the sand. The design was prototyped and devolved by 3D printed parts and microcontroller modules. After testing different designs regarding the mechanisms and electrical components, the design was finalized.This study may not be a completely successful attempt to understand toad-headed agmas’ burial technique, but it introduces key features of the technique and a robotic mechanism to be developed later on
  9. Keywords:
  10. Bioinspired Design ; Self Burying Robot ; Biomimicking ; Toad-Headed Agama ; Vibration in Granular Media ; Burrowing

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