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AUBURN MECH 4240 - Excavator Midterm Pres Summer 2011

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MECH 4240 - Concept Review Corp_2 – Lunar Excavator Anna Holland Kyle Otte Alex Hollis Cody Salmon Han ChoOutline Concept Development • Mission Objective • Gantt Chart • Subsystem Concepts • Decision Matrix • 3 Concepts Concept Details • Final Concept • Drive System • Scoop System • Dump System • Analysis & TestingMission 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 ChartConceptsDecision Matrix + Accomplishes Well - Accomplishes Poorly 0 Indifferent Drive System Weight Strength Cost Complexity Effectiveness Risk of 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 -1Conveyor FailingTracks FailingConcept 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: AugerConcept Option 2 Disadvantage: •Strong motor needed on the bucket (scooping system) Drive System: 6 Wheel Scoop System: Bucket Dump System: HopperConcept 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: HopperFinal 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 TransferSolid Edge SimulationWorking 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 tractionARGO 6 Wheel System • Proof of Concept • No suspension • Skid steer system • Very stable • Very powerfulDump 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 hopperFinite 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 MPaUSDA 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 housingElectrical 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 damageFirst Cut Economic AnalysisEstimated 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) 73.411Critical 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


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AUBURN MECH 4240 - Excavator Midterm Pres Summer 2011

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