Lab # 3:The Programmable Robot

General Engineering Polytechnic University

• Types of Gears

• Simple Gear Train

• Compound Gear Train

• Gear Ratio and Velocity Ratio

• Accuracy and Precision

• Objectives• Procedure• Distance Test• Angle Test• Time Test• Proficiency Test #2:

Excel• Closing

Overview

Spur Gear

• SPUR GEAR: gear wheel having radial teeth parallel to axle

Crown Gear

• CROWN GEAR: gear wheel with teeth set in rim perpendicular to its plane

crown gear

Pinion Gear

• PINION: small cogwheel, teeth of which fit into those of larger gear wheel

piniongear

Idler Gear• Between two other gears to transmit motion

from one to other• Changes direction of rotation• No effect on ratios• ODD number

= reverse rotation• EVEN number =

same rotation idler gear

Simple Gear Train

1” 2” 4”

Output

Input

2

1

4

2

4

1 *

Velocity Ratio

n1 n2 n3

n

n

n

n

n

n *

1

2

2

3

1

3

Gears with the same size teeth, ratio equal to ratio of number of teeth (n) on each gear.

Compound Gear Train

Output

Input

Velocity Ratio

n

n*

n

n

n

n1

2

3

4

5

6* n

n 7

8*

n1

n2 n5

n6

n3n4 n7

n8

Angular velocities of all gears are equal to that of the shaft on which they are mounted

Gear Ratio andVelocity Ratio

Gear Ratio =

Input

OutputVelocity Ratio =

Output

Input

Simple Gear Train

Compound Gear Train

Driving

DrivenGear Ratio =

Driven

DrivingVelocity Ratio =

Accuracy and Precision

AccuratePrecise

InaccuratePrecise

AccurateImprecise

InaccurateImprecise

Objectives

• Suggest improvements to assembly instructions

• Learn importance of understanding instructions and components BEFORE assembly

• Understand related concepts

• Troubleshoot

• Write/Test programs to evaluate performance

• Make necessary calculations

Procedure• Take notes as you work to help you answer

questions

• Refer to assembly instructions throughout lab

• Analyze components

• Assemble robot

• Understand gear linkages

• Determine gear ratio

• Perform three tests

Distance Test• Draw expected straight line path

• Run robot for 3 units of time

• Standard = (Distance traveled by 3) / 3

• Distance robot should run for 5 units of time = standard value * 5

• Repeat 10 times:

– Run robot for 5 units of time

– Measure the distance

START END

Angle Test

• Use data from the distance test

• Draw straight lines from origin to points

• Measure each angle of deviation ()

• Determine accuracy and precision

• Determine standard

START END

Time Test

• Choose distance for robot to travel (should be more than 2 feet)

• Set robot to run on straight path infinitely

• Measure amount of time robot takes to travel chosen distance (first trail is standard)

• Repeat 10 times using same distance

START END

Proficiency Test #2Excel

• Use results of all three tests

• Follow format in manual

• Include:– Title page (include source of data)– Chart comparing your data to someone else’s– Legends with charts (not illustrated in manual)– Table of ONLY your data for each test

(more trials may be included)

Closing

• If failed, discuss possible reasons for failure

• Include recorded observations:– All written observations– Sheets with plotted data

• Original data must be signed by TA

• Use Excel to organize report data

• Make sure ALL questions are answered