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Stair Climbing RobotTeam 7
Senior Design ProjectDalhousie UniversityDept. of Mechanical EngineeringWinter 2009
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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
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DesignFall final design
This is where we were at the end of last semester…Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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Design…and where we are now
• 5 Major Component Groups
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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Design
• 5 Major Component Groups• Tri-Wheels
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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Design
• 5 Major Component Groups• Tri-Wheels• Drive System
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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Design
• 5 Major Component Groups• Tri-Wheels• Drive System• Leveling System
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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Design
• 5 Major Component Groups• Tri-Wheels• Drive System• Leveling System• Frame
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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Design
• 5 Major Component Groups• Tri-Wheels• Drive System• Leveling System• Frame• Controller
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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DesignComponents – Tri-wheels
•Tri-Wheel Components• Faceplates• Gears and Wheels• Cantilever Mount
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
+-
+-
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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.
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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TestingAscent & Descent - 25 lb Weight
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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TestingMaximum Payload Weight
• Incremented weight up to 115 lb payload (almost 5x design requirement)
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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! )
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
Introduction
Design
Testing/Performance
Design Requirements
Budget
Future Work
Thanks
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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
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Stair Climbing RobotTeam 7
Senior Design ProjectDalhousie UniversityDept. of Mechanical EngineeringWinter 2009
Questions?