Deon BlaauwModular Robot Design

University of StellenboschDepartment of Electric and Electronic Engineering

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

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

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

Enabling Motion

Four 12V DC Motors

Power to weight ratio - 213mW/g

Gear ratio – 25:1 Robot Weight –

2kg

Current System

Motor Driver Circuitry

Dual Full-Bridge Driver IC

Bi-directional motor motion

Differential steering

Internal Diagonally Opposed Switches are Pulsed

10kHz PWM Frequency

Current System

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

Current System

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

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

Current System

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

Distributed Voltage Regulation

Star Grounding Minimum of 1.6 Hour Battery

Life 7V – 16.5V Operating Voltage

Power Supply and Voltage Levels

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

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

Demonstration