1. Deon Blaauw Modular Robot Design University of Stellenbosch Department of Electric and Electronic Engineering

2. Why Design a Robot? During the Last Decade a Renewed Interest in the Field of Robotics – Most Research Involving Multi-Robot Teams Today, Robots are Used to Explore Terrain Dangerous or Inaccessible to Humans Aim is to Develop a Modular Embedded Autonomous Agent (Robot) that can be Upgraded and Expanded as needed Primary Goal – First Prototype Must Be Modular Enabling Different Versions with Different Capabilities to Be Developed from the Base Model Secondary Goal - First Prototype Will Demonstrate Engineering Principles to Prospective Students

3. Achieving Flexible Design The Current Robot Exists out of Layers, With Each Additional Layer Improving Overall Robot Functionality Layers are Asynchronous Modules Communicating With Each Other – Each Individual Module Possesses Some form of Computational Ability For the Robot to Achieve More Complex Tasks, Higher Level Modules With Extra Responsibilities can be Added The Result of the Design is a Very Flexible and Expandable Robotic Vehicle

4. Base Prototype Overview Commands Issued From Remote Control Station Drives Forward, Backwards or Steers Differentially Local Obstacle Detection – A Set of Proximity Sensors Prevents Collisions With Obstacles

5. Enabling Motion Four 12V DC Motors Power to weight ratio - 213mW/g Gear ratio – 25:1 Robot Weight – 2kg

6. Current System

7. Motor Driver Circuitry Dual Full-Bridge Driver IC Bi-directional motor motion Differential steering Internal Diagonally Opposed Switches are Pulsed 10kHz PWM Frequency

8. Current System

9. Embedded Motor Driver Controller dsPIC30F4011 Microcontroller 20MIPS Multi-Master CAN useful in Noisy environments UART Module allows PC to control Robot Motor Drivers Directly Voltage Feedback

10. Current System

11. Embedded Sensor and Radio Communication Controller Monitors Cheap Infrared Proximity Sensors – Detects Reflected Infrared Light from Objects Between 400mm and 600mm away. Every Sensor Has Unique Operating Frequency – This Limits Sensor Cross-Talk Sends Commands to Motor Controller Module via CAN at 833kbps Supports 1.25MHz SPI Interface for Radio Link UART Enabled Allowing Direct Computer Control of Sensors and Data Link

12. Radio Frequency Data Link Operating at 915MHz Byte Long Data Length sent From Monopole Antenna Re-transmission of data prevents information loss Ready for next command in 1.81ms

13. Current System

14. Remote Control Station Save Development Time by Using Same PCB as the one Monitoring the sensors Powered From 9V battery Range Confirmed at 10 meters Serial Communication with a PC Allows an alternative communication Method

15. Distributed Voltage Regulation Star Grounding Minimum of 1.6 Hour Battery Life 7V – 16.5V Operating Voltage Power Supply and Voltage Levels

16. Conclusion Highly Modular Design Approach Using a CAN Interface was Followed - Simplifies the Addition of Further Functionality and Allows Expansion of the Current Prototype  The Current Prototype Has Four Full-Bridge Drivers Controlled By a Dedicated Microcontroller  A Separate Microcontroller Controls Proximity Sensors Aiding in Collision Avoidance  An External Controller Communicates via Radio Link With Robot Receiver Sub-System. Able to Act as Test-Bed for a Variety of New Technologies and Clearly Illustrates a Broad Array of Applied Engineering Principles

17. Conclusion Some Engineering Principles Employed During Development:  Power Electronics  Embedded Programming  Digital Circuits  Analog Electronics  Radio Frequency Communication  Power Supply and Grounding Techniques  Physics  Mechanical Design Prospective Students are Shown that Applied Engineering Sciences can Lead to Exciting and Very Rewarding Projects

18. Demonstration