Introduction

A spherical robot shaped like a ball, where all the control devices and mechanical structures are placed inside the shell for protection. The spherical design provides holonomic motion, easy maneuverability, and omnidirectional travel. The shell of the robot acts as the moving mechanism of the robot. When compared with tracked robots and traditional wheeled robots the spherical shell of the robot protects the driving mechanism, sensory and control devices as they are placed inside the shell. Additionally, the stability of the robot can be restored after colliding with obstacles in brief irregular motions. A spherical robot when compared to tracked mobile robots or traditional wheeled robots can navigate efficiently without any hindrances in varying or unknown environments.

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Mechanical Design

Mechanical parts are linked together using a channel and placed inside the shell, this is known as the internal drive unit. Two DC motors consisting omni wheels are always in contact with the inner surface of the shell. Stability and frictional contact is increased inside the shell by using a very thin layer of rubber coating in the inner surface of the shell. Permanent magnets which are joined to the central shaft keeps the mechanism in balance providing a low center of gravity. Magnets using the force of attraction hold the head in place while the wheels having 2 DOF-enabled motion.

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Fabrication

E glass Fiber: Glass fiber being light in weight while having strong structural capabilities is used to absorb shocks and prevent damage to the inner drive unit and the electrical systems was used to build the outer shell. Fiberglass displays a wide range of functions such as being weatherproof, fire-resistant, having good electrical insulating properties, and with very low maintenance requirements. 

Epoxy resin: Used in a ratio of 3:1. 3 parts of epoxy mixed with 1 part of hardener. The solution is used as glue to stick the Glass fiber.

3D Printing: Fused Deposition Modelling (FDM) technique was used to print the head containing the servo motor. Omni wheels and the mounts for the wheels, motors, and servo motors were designed and 3-D printed. 

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Programming

C++ used to program on an Arduino board for motor control, PID control implementation using an IMU sensor and wireless control of the droid via Bluetooth using a mobile application. 

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Methodology

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