MECH 4240 - Concept Review

Corp_2 – Lunar Excavator Anna Holland

Kyle Otte Alex Hollis

Cody Salmon Han Cho

Outline

Concept Development

• Mission Objective

• Gantt Chart

• Subsystem Concepts

• Decision Matrix

• 3 Concepts

Concept Details

• Final Concept

• Drive System

• Scoop System

• Dump System

• Analysis & Testing

Mission Objective

Create an autonomous excavator that weighs less than 80 kg, can collect and deposit at

least 300 kg of lunar regolith within the 15 minute time limit, and that will win the 2012

Lunabotics Mining Competition. The overall size cannot exceed 0.75 m width x 1.5 m

length x 2 m height at the start of the competition. However, the length and width

constraints may be exceeded once the competition starts.

Gantt Chart

Concepts

Decision Matrix

+ Accomplishes Well - Accomplishes Poorly 0 Indifferent

Drive System

Weigh

t

Strength

Co

st

Co

mp

lexity

Effectiveness

Risk o

f Failure

Speed

Total

6 Wheels - + - + + + + 3

4 Wheels 0 0 0 + - + + 2

Tracks - + - - + - 0 -2

Scoop System

Bucket with actuator 0 0 + + + + 0 4

Grader + - + + - 0 - 0

Conveyer Belt - - - - + - + -3

Broom and Dust Pan 0 0 - - 0 0 0 -2

Pull Bucket - - - 0 + 0 0 -2

Auger + + - - - 0 + 0

Dump System

Dump hopper 0 + + + + 0 - 3

Auger + + - - + - - -1

Material

Fiberglass 0 + + 0 + 0 0 3

Aluminum - + 0 + + 0 0 2

Carbon fiber + - - 0 + - 0 -1

Conveyor Failing

Tracks Failing

Concept Option 1

Disadvantages: •Hard object could clog the auger •Regolith could clump and not be picked up by auger •Strong motor needed on the bucket (scooping system)

Drive System: 6 Wheel

Scoop System: Bucket

Dump System: Auger

Concept Option 2

Disadvantage: •Strong motor needed on the bucket (scooping system)

Drive System: 6 Wheel

Scoop System: Bucket

Dump System: Hopper

Concept Option 3

Disadvantages: • Small buckets take longer

to fill Hopper • Very complex design • Belts are less reliable

Drive System: 6 Wheel

Scoop System: Belt with small buckets

Dump System: Hopper

Final Concept

• 6 Wheels

• Regolith Storage Hopper

• Actuator Controlled Dump

System of Entire Storage Hopper

• Single Large Bucket for Mining

Regolith

• Rotational Joint on Bucket Arm

• 1 DOF Regolith Transfer

Solid Edge Simulation

Working Model Simulation

• Actuators strong enough for max loads

• Wheels have enough torque

• Reasonable actuator lengths

• System within size limitation

• Max dump angle ~55°

Drive Subsystem

• 6 motors to control wheels

• (6) 10” x 4” Polyethylene Wheels

•Skid steer system

•Frame Material: Fiberglass Tube

• 1 m x 0.4 m x 0.5 m frame box houses motors, Netbook, & electronics

Analysis & Testing

- Required motor torque can be reached with gearing

- 6 wheels provides enough traction

ARGO 6 Wheel System

• Proof of Concept

• No suspension

• Skid steer system

• Very stable

• Very powerful

Dump Subsystem

• Max Capacity: 150 kg

• Material: Aluminum bottom and front

Analysis & Testing

- 7000 N actuator strong enough to lift full load

- Length of Actuator is reasonable (12 in)

Scoop Subsystem

• Max Capacity: 17.5 kg

• 8.6 full scoops = 1 full hopper

• 18.75 small scoops = 1 full hopper

• Blade to cut through top layer

• Material: Aluminum bottom and back

Analysis & Testing

- Actuator strong enough to lift full load

- Length of actuator is reasonable (12 in)

- Arm length sufficient to reach hopper

Finite Element Analysis

• 10 kg in bucket distributed evenly

• All DOF constrained at end of arms

• Max Von Mises stress of 29.4 MPa

• Aluminum bucket & brackets

• Rigid Epoxy Arms

• Yield Strength of 6061 Aluminum ~200 MPa

USDA Testing

Speed Test Results

Weight Added Distance Time Avg. Velocity

0 kg 5 m 7.0 sec 0.714 m/s

95 kg 5 m 8.0 sec 0.625 m/s

196 kg 5 m 10.3 sec 0.485 m/s

• Motor performance not affected

• Velocity loss mostly due to 4 small wheels & ground clearance

• Issues with battery & Netbook housing

Electrical System

Issues from testing

• Battery and Netbook housing

• Loss of battery connection

Re-Design

• Incorporate specific housing to prevent battery from disconnecting

• Protect/cushion the Netbook from vibration damage

First Cut Economic Analysis

Estimated Mass Breakdown Mass Budget Tracking

Subsystem Component

Mass

(kg) Qty

Mass Total

(kg)

Scoop System Bucket 2.800 1 2.800

Actuator 2.500 2 5.000

Mechanical Arms 2.500 1 2.500

Drive System Wheel 3.100 6 18.600

Motor 0.920 6 5.520

Dump System Hopper 10.000 1 10.000

Actuator 6.800 1 6.800

Frame Body (tubing,

panels, etc) 12.000 1 12.000

Electrical Circuit

System 0.500 1 0.500

Batteries 2.700 2 5.400

Netbook 1.500 1 1.500

Miscellaneous Cameras 0.097 3 0.291

Fasteners 2.500 1 2.500

Total Weight (kg) 73.411

Critical Design Review

• Full failure analysis / Concept verification

• Scaled down mock up

• Further Testing

– Aluminum angle test

– 3 point bending test on fiberglass tubing

– Moment calculations for arms & actuators

– Finite Element Analysis

• Fully dimensioned CAD drawings

• Dissemble old excavator (Preserve Electrical)

Any Questions?