Electromechanical Systems

“Robotic Sorting System”

Brent Guy Jonathan Penney

ObjectivesObjectives

• Design a robotic sorting system

• Construct a routine to locate test tubes

• Ignores locations if shelf is empty

• Transport them from storage shelf to desired location

Design Specifications

Robotic arm has 2 major limitations:

• Rotational limits• Height constraints

Size of shelf compartments

Weight of test sample

Design EvolutionDesign Evolution

• Robotic arm with RGB sensor• 9 compartment shelf design• Puts samples on shelf

• Robotic arm with IR Sensor• 3 compartment shelf design• Takes samples from shelf

HardwareHardware

PIC Microcontroller

• 40-pin 16F877 embedded chip• Provides analog to digital conversion• Sends pulse waves to control servomotors

HardwareHardware

Servomotor

• Pulse-proportional servos move the links• 180 degree range of motion• Positions are based on incoming pulses

- 2500 units = 2.50 mS pulse

(1 unit = 0.09 degrees)

HardwareHardware

SSC-32 Servo Controller

• Integrated circuit board that controls servos• Servos plug into respective channels• Reads converted digital inputs from PIC

HardwareHardware

MAX232 Converter

• Adjusts voltage of signals so communication can take place between PIC and SSC-32

• SSC-32: -10 V for logic one, +10 V for zero• PIC: +5 V for logic one, 0 V for zero

HardwareHardware

IR Proximity Sensor

• Panasonic sensor with 2 LEDs• 4 – 26” range• Sensitivity adjusted by potentiometers• Information digitally sent to PIC

SoftwareSoftware

RIOS

• Allows user to configure servos• Define positional limits of servos

TTY

• Provides direct serial communication• Allows for quick alterations

* Final code produced in C

RIOS ScreenshotRIOS Screenshot

Programming a ServomotorProgramming a Servomotor

Format:

• # <Motor> P <Units> T<mSeconds>

- E.g. #0 P1000 T3000

Moves motor 0 to position 1000 in 3 seconds

Pseudo CodePseudo Code

• Set Initial Position

• Scan A– If object present, grip and drop– If not, continue to B

• Scan B – If object present, grip and drop– If not, continue to B

• Scan C– If object present, grip and drop– If not, Set Initial Position

Robot DemonstrationRobot Demonstration

DifficultiesDifficulties

• Missing link parts

• Faulty servomotors

• Short wires required splicing

• Friction of base plate (removed 3 spokes)

• Power source

RecommendationsRecommendationsFuture Use

• Keep robot within suitable range (cannot move shelf without re-programming)

• Infrared sensor has trouble detecting transparent tubes

Improvements

• RGB sensor• Add movement for transportation

• Wheels• Track

ConclusionConclusion

• Assembled Robot• Programmed• IR Sensor• Shelf Construction

• Resulting in a functional robot that

detects and transports test tubes for the biomedical industry