Autonomous Following RObotCritical Design Review

James Tse (Leader)Wei Dai

Travis FreckerPeter Verlangieri

Professor John JohnsonECE 189A Fall 2012

Critical Design Review: Project Description

● A robot that follows and traces existing lines.● Applications:

○ Redrawing existing sports fields, e.g. basketball, tennis, football, soccer

○ Repainting fading street lines○ Perimeter security○ Warehouse item retrieval/storage

Critical Design Review: Project Description (II)

● Base proof of concept goals: ○ Following a line with high precision and accuracy.○ Using a set of rules to be able to find and trace

existing lines, without user input.○ Navigating to specific coordinates of a grid.

Critical Design Review: Project Description (III)

● Combination of sensors and positioning systems:○ IR Sensors○ Sonar○ Reflectance Sensor Array○ Digital Compass○ Rotary Encoders

James (leader) - schematic/PCB, optical sensorWei - schematic/PCB, digital compassTravis - mechanical - servo, reflective sensor, powerPeter - mechanical - motors,wheels, rotary encoders, power

All: chassis design/fabrication, schematic, processor

Critical Design Review: Subsystem Development Responsibility

Critical Design Review: Block diagram

Critical Design Review: Basic Design

1. Reflectance Sensor Arrays2. Ultrasonic/IR Sensors3. Freewheels4. Wheels5. Rotary Encoders6. Processor, SDRAM, compass, motor controller.

Critical Design Review: Chassis Design

● NXP LPC2478 ARM7 Processor○ External memory interface○ Integrated ADC○ I2C Bus○ PWM Output○ UART

Parts: Processor

● Micron 16bit 128Mb SDRAM○ 2 MEG X 16 X 4 BANKS○ 54-PIN TSOP Package○ Connects to LPC2478 external memory interface

Parts: SDRAM

Parts: Reflectance Sensor Arrays

● 2 x QTR-8RC Reflectance Sensor Array○ 16 total IR Emitters/Detectors will allow us to

detect the lines.○ Consistently polled by the processor○ Sensing distance: 3-9.5mm to ground○ Direct digital interface to processor through GPIO○ Metal Shade will go over them to minimize effects

of ambient light.

Parts: Digital Compass

● LSM303DLHC High Performance E-Compass○ Outputs heading via I2C○ 5V voltage only○ Polled by processor

● The servo is used to position a marker for drawing lines.

● HS-55 Micro Servo Motor○ 3-5V Operation○ PWM Enable control signal from processor○ Running Current: 150mA○ Idle Current : 5.4mA○ $9.99

Parts: Servo Motor

● Sharp GP2Y0A21YK0F IR Range Sensor○ Object avoidance ○ Detects objects of distance from 10cm to 80cm (4''

to 32'').○ Output: Analog to Digital ○ 4.5 - 5.5V, supply current: 30mA○ Data Polled by processor

Parts: IR sensor

● Maxbotix LV-MaxSonar-EZ0○ Object avoidance○ Detects objects of distance from 0 to 6.45 meters.

(0 to ~21 ft).○ RS-232○ 2.5 - 5.5V, at 5V - 3mA○ Polled by processor

Parts: Ultrasonic Sensor

● 2x Pololu 12V Metal Brushless DC Gear Motors○ 67:1 Gear Ratio○ 250mA Free-Run Current○ Forward/Backward/Brake/Pivot○ 75rpm free run speed○ 0.40m/s using 100mm diameter wheels.

Parts: Motors

● Rotary encoders provide feedback to the microprocessor via GPIO.

● Frequency of output signal provides speed of the motor and distance traveled.

● Using encoders on both the right and left wheel allows the microprocessor to calculate and correct offset in traveling in the straight line.

Parts: Rotary Encoders

● Acts as intermediate device between processor, power supply and motors.

● Provides the high voltage and current requirement the motors need and protects the processor from back EMF

● Solarbotics L298 Compact Dual Motor Driver Kit○ Two independent PWM enable signals○ 4 GPIO logic singles control rotational direction

Parts:Motor Controller

6V Battery

6V -> 5VLM317 1.5Amp 3-Terminal Adjustable Regulator

R1 = 240ohmR2 = 720ohm

5V ->3.3VLM117 0.5 Amp 3-Terminal Adjustable Regulators

R1 = 240ohmR2 = 394ohm

Vout = 1.25V(1+R2/R1)

Parts: Voltage Regulators

● All of the peripherals will be mounted onto chassis.● Jumper cables will be used to attach the devices to

connectors on the board.○ Cost!!○ Ability to rearrange parts on chassis and test

individual device.

Parts: Connectors

Schematic rev. 1.9

Schematic rev. 1.9

Schematic rev. 1.9

Schematic rev. 1.9

Schematic rev. 1.9

Schematic rev. 1.9

Schematic rev. 1.9

Critical Design Review: Bill of Materials

Quantity Part Unit Cost Total Cost

1 Digital compass $19.95 $19.95

2 Reflectance sensor array $14.94 $29.88

1 Ultrasonic sensor $26.95 $26.95

3 IR Sensor $13.89 $26.90

2 Motor and Rotary Encoders $39.95 $79.90

1 Motor Controller $18.28 $18.28

1 Servo Motor $9.99 $9.99

Voltage Regulators, Passive Components ~$30.00

Connectors ~$20

Chassis, Wheels, Mechanical Component, Batteries ~$100

Total $361.85

Software:○ GCC toolchain:

■ Yagarto ■ WinARM■ GNUARM

○ QP-Nano ARM7 Framework○ Eclipse

Critical Design Review: Software Overview

● Motor control ○ Keeping the bot in a straight path to avoid rough

traces.● Reflectance Sensor Array

○ Being able to detect a line in an outdoor environment and use that data to accurately position AFRObot.

Critical Design Review: Critical Elements

Questions?Suggestions?