stair climbing robot team 7 senior design project dalhousie university dept. of mechanical...

Stair Climbing RobotTeam 7

Senior Design ProjectDalhousie UniversityDept. of Mechanical EngineeringFall 2008

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Introduction

Team members:

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

Supervisor:Dr. Ya-Jun Pan

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Design Requirements

•Robot Weight of 60 kgHeight/Width less than standard door

•Payload Weight of 12 kg Footprint of 400 X 400 mm

• Climb and descend stairs• Self-leveling payload platform• Powered by standard AC electricity• Safe 150 mm

300 mm

Major design considerations when designing alternatives

• Ability to carry payload • Speed and smoothness of climb• Weight• Weight distribution and tipping• Power needs and power distribution•Modularity

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Design SelectionMajor Considerations

(1) Linear Actuator• Sensors control platform angle• Pros – store-bought• Cons – difficult to code; costly

Design SelectionAlternatives – Payload Leveling System

(2) Cradle Leveler• Platform in cradle freely rotates• Pros – self levels; no programming• Cons – center of gravity; difficult to control damping

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

(1) Treads• Parallel treads• Pros – simple; store-bought• Cons – may slip; requires more power on flat plane

(2) Corkscrew• Small wheels in helix shape• Pros – ‘wow’ factor; unlikely to slip backward• Cons – construction; wobble

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Design SelectionAlternatives – Stair Climbing Drive

• The payload platform is automatically leveled by gravity using two curved guide rails fixed to the top of the frame.• As the robot climbs, the platform is free to roll within the rails and will remain level with the horizontal.

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Final DesignRail Leveling System

• The optimum radius calculated from this angle is 261 mm. • Opted to use θp = 50° to have sufficient moment arm length and to minimize θ associated with arc length (140 for θp = 50°) for decreased fabrication time, cost and difficulty.

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Final DesignRail Leveling System

• Finite Element Analysis in UG NX 5.0 used to determine dimensions of components based on maximum deflection• Performed mesh convergence studies to determine appropriate element sizes• Modeled rails and platform using 2D Thinshell elements

Rails• Determined that supports should be located on either side of applied force from platform to minimize deflection

Platform• Determined thickness of platform to be >2 mm to minimize centre deflection of plate with maximum payload

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Final DesignFinite Element Analysis of Leveling System

• The Tri-wheel assembly is motorized through a drive shaft connected to the central ‘sun’ gear

• All wheels are driven at equal speed via the rotation of the central gear

•Pros: smooth climbing; good lateral stability; maneuverability on flat ground

• Cons: complex design; difficult to manufacture

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Final DesignTri-wheel Stair Climber

The dimensions of all components must be contained within the faceplate dimensions to avoid interference with the stairs.

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Final DesignTri-wheel Stair Climber

• Wiper motors have been chosen to provide the motive power for the machine, due to their price, availability, pre-existing worm-gear reduction, and 2-speed setting.

• The wiper motors will be fixed to a 40 chain double sprocket, sending one chain to the front wheel and one to the back.

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Final DesignDrive System

The guide rail and the Tri-Wheel modules will be fixed to a robust aluminum skeleton using standard M8 nuts and bolts.

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Final DesignComplete Assembly

Maximum $2500

               Level Up Budget                     Item Cost/Unit # units Cost    Gears 25-40 28 940    Wheels 30 12 360    Bearings 10 36 360    Raw Materials 200 1 200    Drive Shaft 30 4 120    Speed Controller 100 1 100    Electric Motor 50 2 100    Replacement of Parts 100 1 100    Nuts/Bolts/Bits&Bobs 90 8 90    Chain Sprocket 10 8 80    Wiring/Chain/Cords 50 1 50                    

Total Cost $2,500 

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Budget

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Future Considerations

•Final torque and RPM values

•Frame support locations

•Controller device

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Conclusions

•Projected to satisfy all design requirements set out in September.

•Designed to test design concepts

•Design can be scaled up to carry a considerable amount of weight.

Introduction

Design Requirements

Design Selection

Final Design

Budget

Conclusions

Thank you

Shell Canada

Dr. Ya-Jun PanDr. Julio MilitzerL. E. Cruickshanks Sheet MetalDalhousie Mechanical Engineering Department

Stair Climbing RobotTeam 7

Senior Design ProjectDalhousie UniversityDept. of Mechanical EngineeringFall 2008

Questions?