AGV / ASRSApril 12th, 2005

Student Names: Trevor Skipp and Albert ChungInstructor: A. A Arroyo

University of FloridaDepartment of Electrical and Computer EngineeringEEL 5666: Intelligent Machine Design Laboratory

Summary

• Concept

• Behaviors

• Implementation

• Communication protocol

• Conclusions

• Suggestions for future study

Inspiration

Current Standard Desired Attributes

•Poor warehouse utilization

•Dynamic storage

•Warehousing is a “middle-man” business

•Lower labor and insurance overhead

•Safety drawbacks •Reduce the risk of personal injury

Designers’Approach

• Divide tasks among two automated vehicles– AGV (Automated Guided Vehicle)

• Inexpensive, small, fast, and nimble

– ASRS (Automated Storage and Retrieval System)

• Expensive, tall, slow, and bulky

Behaviors

Design Specifications

• Operate in a 4’x8’ model warehouse

• Navigation

• Obstacle detection

• Queue

• Communication

• Mechanical fork lift

Model Warehouse

• Shipping and receiving docks

• Transition dock• Storage shelves

Navigation

• Follow a high contrast line

• Cartesian coordinate system

• Knowledge of current location, destination, and direction

Queue

• FIFO job processing

• Incoming pallets are marked with an age

• Outgoing pallets are delivered oldest first

• Application to food and other products that can expire

Communication

• User input– Notify that a pallet is entering the warehouse– Request a pallet to be shipped out

• Data link between vehicles– Assign tasks– Determine transition dock– Notify when a task is completed

IN OUT

Simulation

DOCKS

PurposePurpose♦♦ Transfer products Transfer products

safely safely on and off shelf on and off shelf

spacespace

SummarySummary

DOCK SHELVES

Implementation

Required Modules

• Fork Lift

• Power

• Motor Driver

• L.C.D.

• Sensors

• RF Transceiver

Fork Lift (ASRS)

• Capable of lifting pallets onto a 3 tier shelf

• Screw type powered by a 200 RPM motor

• Expensive

Fork Lift (AGV)

• One height• Tilt type powered by a

servo• Cheap

Interrupts

Low Priority

1. Remote control

2. RF data link

High Priority• Fork• RF Timer overflow

Power

• Required voltage levels:– 3.3V: Logic

– 5V: Motor driver, LCD, servo

– 12V: Gear head motors

Backbone Sensors

• Line follower: Optek OPB745 Reflective Object Sensors

• Obstacle detection: Sharp GPD2D12 infrared range finders

• Obstacle collision: Bump sensors

Line Follower Module

IR Detector

• Sony television remote (code #202)

Decoding Technique

Remote Button “3”

1 0 0 0 0 1 1 0 0 0 0 0 1 1

1 0 0 0 0 1 1 0 0 0 0 0 1 1

0 0 0 1 1

0 0 0 1 1

1 1 1 0 0

Initial Sample

Mask

Reverse

First Signal

Subsequent samples

ResultsRemote Button

Algorithm Result

0 0x0A

1 0x01

2 0x02

3 0x03

4 0x04

5 0x05

6 0x06

Remote Button

Algorithm Result

7 0x07

8 0x08

9 0x09

CH UP 0x11

CH DWN 0x12

VOL UP 0x14

VOL DWN 0x15

RF Transceivers

• Laipac TRF-2.4G– 1Mbps– Hardware CRC– Dual channel, full duplex– Two operating modes: Direct Mode and

Shockburst

Communication Protocol

Stop and Wait ARQ

• Error detection

• Positive acknowledgment

• Retransmission after timeout

• Negative acknowledgement and retransmission

Header Error Control

• Purpose: lost or damaged frames

|----------Header------------| |-----------Data-------------|

Frame # Check # I/O Dock #

1 bit 3 bits 1 bit 3 bits

Alternating Frame Numbers

Special Considerations

• Dynamic resynchronization

• Stations have different timeout lengths

• Lost connection

• Duplicate transmissions

Example• ASRS

– Places a command from the remote control onto the queue

– Sends command to the AGV through RF– Sets timer and waits for an ACK

• AGV– ACKs packet– Echoes packet back after the job is completed– Sets timer and waits for an ACK

• ASRS– ACKs packet– Updates queue

Conclusions

• Navigation

• Communication– Remote control– RF protocol

• Experience– Debugging– Design software: Eagle & AutoCAD

Suggestions for Future Study

• Sliding Window ARQ

• Larger warehouse with more shelves

• Swarm Approach: Multiple AGVs for every ASRS

• “Conveyor Belt” robot