Amphibious Spherical Explorer Kaiwen Chen, Zhong Tan, Junhao Su ECE 445 Spring 2016, Project 30 TA: Luke Wendt May 1, 2016

Contents  Introduction  Objectives  Design  Requirements and Verification  Conclusion  Potential Applications and Future work

Introduction – Inspiration Source: Source:

Introduction – Our Robot

Contents  Introduction  Objectives  Design  Requirements and Verification  Conclusion  Potential Applications and Future work

Objectives – Analysis on Spherical Robots  Advantages –High surface adaptability: can travel across hard ground, mud, desert, wetland, or even water. –Durable: no protrusions on outer surface; most uniformly loaded shell.  Disadvantages –Need for heavy pendulum: low mechanical efficiency. –Hard to control: wobbliness.

Objectives – Our modifications  Compact design and mass arrangement.  Smooth movement (acceleration, deceleration, turning and free of wobbliness).

Contents  Introduction  Objectives  Design  Requirements and Verification  Conclusion  Potential Applications and Future work

Design – System Overview

Design – Mechanical design Generic Model

Design – Mechanical design *Timeline created using readwritethink.org

Design – Mechanical design  First design  Why it failed –Gear complexity –Poor center of mass position control –Inability to incorporate magnetic encoder

Design – Mechanical design  New design  Benefits –Gears removed –PCB becomes the mass –Magnetic encoder added  Problems and concerns –Fixing axle to shell –Water resistance

Design – Mechanical design  T-Bar design  Issues addressed –Water resistant design –Easy to open  Still have problems! –Aesthetically unpleasant –Physically constrained

Design – Mechanical design  Final version  Machine shop’s assistance –Thanks to Glen Hedin and Scott McDonald  Issues addressed –Still water resistant –Still easy to open –Aesthetically pleasant

Motor Driver Wi-Fi Microcontroller Design – Circuit  Main board schematic

Design – Circuit  Main board PCB

Design – Circuit  Sensor board schematic Magnetic Encoder IMU

Design – Circuit  Sensor board PCB

Design – Rotary Magnetic Encoder  Sensor to measure the relative angle  Differentiation of the angle: angular speed → linear speed. Image courtesy of [Austria Microsystems (AMS) ] at sensorsportal.com

Design – Rotary Magnetic Encoder  Roll-over effect

Design – Rotary Magnetic Encoder  Differentiation noise –Use first-order Butterworth filter.

Design – Inertial Measurement Unit (IMU)  Accelerometer –Accurate for low frequency signal. –Suffers from noise from motion.  Gyroscope –Accurate for high frequency signal. –Suffers from the drift of low frequency signal.

Design – Inertial Measurement Unit (IMU)  Solution: complementary filter

Design – Inertial Measurement Unit (IMU)  Complementary filter implementation

Design – Control panel  Command line control  Gamepad control  Data feedback and analysis

Design – Control system  Actuators –DC motor, servo  Controller –Roll controller: PID controller –Pitch controller: P controller –Speed controller: PI controller –Antilock Brake System (ABS)

Design – Control system  Positive feedback compensation on servo –Effective actuation angle = Actuation angle - Roll angle –Actuation angle = Effective actuation angle + Roll angle

Design – Control system

Contents  Introduction  Objectives  Design  Requirements and Verification  Conclusion  Potential Applications and Future work

R & V – Modular test  WiFi connection –packet loss rate = 0 < 10% (distance: 20 m).  Microcontroller task scheduling –frequency of a task cycle = 100 Hz > 20 Hz.  Magnetic encoder –Relative error = 1% < 50%  IMU attitude measurement –Relative error = 8.9% < 20%

R & V – Speed/acceleration  Max speed = 2 m/s > 1m/s  Rising time = 4.37 s < 15 s  Overshoot = 0.5% <50%

R & V – Wobbliness

 Oscillations: 2 times < 20 times

Contents  Introduction  Objectives  Design  Requirements and Verification  Conclusion  Potential Applications and Future work

Conclusion  Achievement –Good control on wobbliness Industry (2015) Source: Academia (2009) Source: Our design –No unnecessary mass added to the robot.  Things we have no time to do –Camera –Tuning controller based on learning.

Contents  Introduction  Objectives  Design  Requirements and Verification  Conclusion  Potential Applications and Future work

Potential Applications and Future work  Future Work –Add flying wheels to the pendulum for larger driving torque. –Add real-time video system.

Potential Applications and Future work  Potential applications –Home monitor. –Smart fishing float. –Military use and related ethical issues.

Questions

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