Stair Climbing Robot

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Stair Climbing Robot Team 7 Senior Design
Project Dalhousie University Dept. of Mechanical
Engineering Winter 2009
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Introduction
Introduction
Design
Testing/ Performance
Design Requirements
Team members
Janet Conrad, Jason Lee, Stanley Selig, Evan
Thompson, Dylan Wells
Supervisor
Budget
Dr. Ya-Jun Pan
Future Work
Thanks
3
Design Fall final design
This is where we were at the end of last semester
Introduction
Design
Testing/ Performance
Design Requirements
Budget
Future Work
Thanks
4
Design and where we are now
Introduction
Design
Testing/ Performance
Design Requirements

• 5 Major Component Groups

Budget
Future Work
Thanks
5
Design
Introduction
Design
Testing/ Performance
Design Requirements

• 5 Major Component Groups
• Tri-Wheels

Budget
Future Work
Thanks
6
Design
Introduction
Design
Testing/ Performance
Design Requirements

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

Budget
Future Work
Thanks
7
Design
Introduction
Design
Testing/ Performance
Design Requirements

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

Budget
Future Work
Thanks
8
Design
Introduction
Design
Testing/ Performance
Design Requirements

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

Budget
Future Work
Thanks
9
Design
Introduction
Design
Testing/ Performance
Design Requirements

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

Budget
Future Work
Thanks
10
Design Components Tri-wheels

• Three-wheeled design
• Planetary gear configuration driven by central
  gear from drive-train
• Will drive along flat ground by spinning all
  wheels

Introduction
Design
Testing/ Performance
Design Requirements

• Front wheel climbs stairs when contacting stair
  due to friction
• Entire tri-wheel rotates about its axis,
  mounting the stair

Budget
Future Work
Thanks
11
Design Components Tri-wheels
Introduction
Design
Testing/ Performance
Design Requirements

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

Budget
Future Work
Thanks
12
Design Components Tri-plates

• Profile designed to avoid interference with
  stairs right angle
• Complex profile cut from 3/16 Al sheet metal at
  L.E. Cruickshanks Sheet Metal Ltd. using a plasma
  cutter

Introduction
Design
Testing/ Performance

• 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

Design Requirements
Budget
Future Work
Thanks
13
Design Components Gears Wheels

• 20 pitch, hardened steel, turned down to reduce
  weight
• Idler gears bored out to seat bearings which
  rotate on fixed posts

Introduction
Design
Testing/ Performance
Design Requirements

• Wheels are Abec 11 Flywheels skateboard wheels
• 97mm, chosen for high coefficient of friction
• Fixed rigidly to wheel shafts

Budget
Future Work
Thanks
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Design Components 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
15
Design Components 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

Introduction
Design

• Lateral mounting of motors allows skid steering
• Shafts made of steel, with custom threading and
  keying

Testing/ Performance
Design Requirements
Budget
Future Work
Thanks
16
Design Components Leveling System

• Finite element analysis used in design
• Curves designed for ISO stair angles
• Curved rails fabricated using roller mill at
  L.E. Cruickshanks

Introduction
Design
Testing/ Performance
Design Requirements

• Platform keeps payload level during ascent and
  descent of stairs
• Platform covered with high-friction liner to
  prevent payload from sliding

Budget
Future Work
Thanks
17
Design Components Frame
Introduction
Design
Testing/ Performance
Design Requirements

• 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

Budget
Future Work
Thanks
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Design Control system
Transmitter
Introduction
Design
Receiver

• Sabertooth speed controller controls motors on
  each side
• Permits skid steering and straight driving

Testing/ Performance

-
Motor Driver
Design Requirements

• Controlled with an RC transmitter
• Operated from safe position

Budget

-
Future Work
Motor
Motor
Battery
Thanks
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Testing Summary

• 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
20
Testing Summary

• 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
21
Testing Control 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.

Introduction
Design
Testing/ Performance

• Placed ammeter in motor circuit
• Maximum current draw was 8 A.

Design Requirements
Budget
Future Work
Thanks
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Testing Ascent Descent Tile Surface
Introduction

• Tested climbing stairs around campus
• Not enough friction generated at wheel/stair
  interfaces
• Front wheel skids instead of locking

Design
Testing/ Performance
Design Requirements

• Motor power transmitted to spinning front wheels
• Locked gears to test concept
• Tri-wheel pivoted as expected

Budget
Future Work
Thanks
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Testing Ascent 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

Introduction
Design
Testing/ Performance
Design Requirements

• Climbed the 7 stair flight from bottom to top
• Repeatability will be discussed after testing
  video

Budget
Future Work
Thanks
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Testing Ascent Descent - 25 lb Weight
Introduction
Design
Testing/ Performance
Design Requirements
Budget
Future Work
Thanks
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Testing Ascent Descent Payload Leveling
Introduction
Design
Testing/ Performance
Design Requirements

• 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

Budget
Future Work
Thanks
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Testing Repeatability

• 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

Introduction
Design
Testing/ Performance
Design Requirements

• 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

Budget
Future Work
Thanks
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Testing Maximum Payload Weight
Introduction
Design
Testing/ Performance
Design Requirements
Budget
Future Work

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

Thanks
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Design Requirements
Introduction
Design
Testing/ Performance
Design Requirements
Budget
Future Work
Thanks
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Design Requirements
Introduction
Design
Testing/ Performance
Design Requirements
Budget
Future Work
Thanks
30
Design Requirements
Introduction
Design
Testing/ Performance
Design Requirements
Budget
Future Work
Thanks
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Budget Overview

• 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/levelupgro
  up

Introduction
Design
Testing/ Performance
Design Requirements
Budget
Future Work
Thanks
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Future Work/Considerations
Introduction

• 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

Design
Testing/ Performance
Design Requirements
Budget
Future Work
Thanks
33
Thanks
Introduction
Design
Testing/ Performance
Design Requirements
Angus, Albert, and Mark Jon MacDonald, Dylan
Scott, Julian Ware, Colin OFlynn Peter Jones
Dr. Ya-Jun Pan Dr. Julio Militzer
Budget
Future Work
Thanks
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Stair Climbing Robot Team 7 Senior Design
Project Dalhousie University Dept. of Mechanical
Engineering Winter 2009
Questions?