Stair Climbing RobotTeam 7

Senior Design ProjectDalhousie UniversityDept. of Mechanical EngineeringWinter 2009

Introduction

Design

Testing/Performance

Design Requirements

Budget

Future Work

Introduction

Team members:

Janet Conrad, Jason Lee, Stanley Selig, Evan Thompson, Dylan Wells

Supervisor:Dr. Ya-Jun Pan

Thanks

DesignFall final design

This is where we were at the end of last semester…Introduction

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Design…and where we are now

• 5 Major Component Groups

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Design

• 5 Major Component Groups• Tri-Wheels

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Design

• 5 Major Component Groups• Tri-Wheels• Drive System

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Design

• 5 Major Component Groups• Tri-Wheels• Drive System• Leveling System

Introduction

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Design

• 5 Major Component Groups• Tri-Wheels• Drive System• Leveling System• Frame

Introduction

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Design

• 5 Major Component Groups• Tri-Wheels• Drive System• Leveling System• Frame• Controller

Introduction

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DesignComponents – Tri-wheels

• Three-wheeled design

• Planetary gear configuration driven by central gear from drive-train

• Will drive along flat ground by spinning all wheels

• Front wheel climbs stairs when contacting stair due to friction

• Entire tri-wheel rotates about its axis, mounting the stair

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DesignComponents – Tri-wheels

•Tri-Wheel Components• Faceplates• Gears and Wheels• Cantilever Mount

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DesignComponents – Tri-plates

• Profile designed to avoid interference with stair’s right angle

• Complex profile cut from 3/16” Al sheet metal at L.E. Cruickshanks Sheet Metal Ltd. using a plasma cutter

• One central bearing to facilitate rotation of the tri-wheel assembly about the main axis

• Three 3/8” bearings to support wheel shafts

• Bearing seats fixed to tri-plates

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DesignComponents – Gears & Wheels

• 20 pitch, hardened steel, turned down to reduce weight

• Idler gears – bored out to seat bearings which rotate on fixed posts

• Wheels are Abec 11 ‘Flywheels’ skateboard wheels

• 97mm, chosen for high coefficient of friction

• Fixed rigidly to wheel shafts

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DesignComponents – Cantilevered Pipe Mount

• Tri-wheel assembly rotates around the outside

• Drive shaft rotates inside supported by bearings at either end

• Attaches to underside of frame with carriage bolts

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DesignComponents – Drive train

• One windshield wiper motor from 1994 Ford Tempo mounted on each side

• ANSI 25 chain connects a small sprocket (14 tooth) to a large sprocket (26 tooth) for gear reduction

• Lateral mounting of motors allows skid steering

• Shafts made of steel, with custom threading and keying

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DesignComponents – Leveling System

• Finite element analysis used in design

• Curves designed for ISO stair angles

• Curved rails fabricated using roller mill at L.E. Cruickshanks

• Platform keeps payload level during ascent and descent of stairs

• Platform covered with high-friction liner to prevent payload from sliding

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DesignComponents – Frame

• Constructed of 1” aluminum square stock

• Lightweight frame

• Facilitates ease of mobility

• Modular design allows mounting of custom parts and different configurations

• Frame was welded together and is very robust

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DesignControl system

• Sabertooth speed controller controls motors on each side

• Permits skid steering and straight driving

• Controlled with an RC transmitter

• Operated from safe position

Receiver

Motor Driver

Transmitter

Motor MotorBattery

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+-

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TestingSummary

• Most tests conducted are qualitative, as most of the components of our robot are purely mechanical in nature

• Control tests included:• Connecting motors to battery

• Adjusting motor speeds with potentiometer

• Testing RC transmitter and receiver

• Measuring current draw from loaded motor

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TestingSummary

Climbing and drive tests included:

• Powering wheels while robot is on blocks

• Straight line motion test high/low speed

• Turning on the spot

• Turning while driving

• Stair descent & ascent - no payload

• Stair descent & ascent - required payload

• Determination of maximum payload weight

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TestingControl Tests

• Connected the motors and speed controller to a power supply and controlled with two potentiometers.

• Motors worked as expected for low-speed.

• Connected the receiver and transmitter to motor driver inputs.

• Robot controlled as expected. Some electrical interference.

• Placed ammeter in motor circuit

• Maximum current draw was 8 A.

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TestingAscent & Descent – Tile Surface

• Tested climbing stairs around campus

• Not enough friction generated at wheel/stair interfaces

• Front wheel skids instead of locking

• Motor power transmitted to spinning front wheels

• Locked gears to test concept

• Tri-wheel pivoted as expected

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TestingAscent & Descent - Concrete

• Attempted climbing another set of stairs with payload

• Found flight with appropriate dimensions for our robot

• Concrete stairs provided better friction and less traffic

• Climbed the 7 stair flight from bottom to top

• Repeatability will be discussed after testing video

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TestingAscent & Descent - 25 lb Weight

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TestingAscent & Descent – Payload Leveling

• High-friction liner used for damping and friction

• Minimal plate bending at operating loads

• ~5 deg change in plane during normal operation

• Dampens quickly with very little overshoot from center

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TestingRepeatability

• Ascended 7 stair flight in average time of 1 minute 34 seconds with 25 lb payload

• This represents travel time of 4.5 stairs per minute on average

Run # (Ascent) Time

1 1:33

2 1:20

3 1:50

Run # (Descent) Time

1 1:15

2 0:55

3 0:45

• Descended 7 stair flight in average time of 58 seconds with 25 lb payload

• This represents travel time of 7.2 stairs per minute on average

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TestingMaximum Payload Weight

• Incremented weight up to 115 lb payload (almost 5x design requirement)

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Design Requirements

Design Requirement Status Pass?

Robot must weigh less than 60kg

Weight – 29.5kg(2x lighter than required!)

Robot must fit through door (0.91m x 2.03m)

Width – 0.83mHeight – 0.53m

Robot must be less than 2m length

Length – 1.08m(Only ½ the maximum length!)

Robot must carry payload of 12kg

Payload - 52.5kg(4.5x heavier payload than required! )

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Design Requirements

Design Requirement Status Pass?

Robot must ascend stairs at a rate of no less than one stair per minute

4.5 stairs per min(4.5x faster than req’d!)

Robot must descend stairs at a rate of no less than one stair per minute

7.2 stairs per min(7.2x faster than req’d!)

Robot must be able to self-level a platform upon which a payload sits

Created, tested, and works

Robot must be able to carry a 400x400mm payload

Payload can fit on platform

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Design Requirements

Design Requirement Status Pass?

Robot must be user operated with handheld controller

RC transmitter tested and works

Power supplied from AC socket Battery powered – more mobility

An operations manual will be provided Ops manual written

1 year lifetime with no maintenance No failing components yet

Total Requirements Met:12/12

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BudgetOverview

• Budget awarded last semester was $2500

• Summary of the main expenses shown

• More than $500 under budget

• Savings from:• Better value components • Majority of raw materials

donated by L.E. Cruickshanks Sheet Metal Ltd.

• For more detailed budget, consult the final report on our website – www.tinyurl.com/levelupgroup

Cost791445336105

322

Budget

WheelsMotors

Main Expenses

ItemGearsControls

$2,500

Everything Else

Total Cost $1,999

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Future Work/Considerations

• Gear locking mechanism to rotate entire tri-wheel when desired

• Covering to protect/weatherproof electronics

• High quality receiver to allow wireless high/low speed switches

• Damping mechanism for guide rails

• Payload platform walls/ straps

• Mount batteries on frame

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Thanks

Angus, Albert, and MarkJon MacDonald, Dylan Scott, Julian Ware, Colin O’Flynn Peter Jones Dr. Ya-Jun PanDr. Julio Militzer

Introduction

Design

Testing/Performance

Design Requirements

Budget

Future Work

Thanks

Stair Climbing RobotTeam 7

Senior Design ProjectDalhousie UniversityDept. of Mechanical EngineeringWinter 2009

Questions?