University of Notre Dame Department of Aerospace in addition to Mechanical Engineering Matt
Campbell, Cherie, Contributing Editor has reference to this Academic Journal, PHwiki organized this Journal University of Notre Dame Department of Aerospace in addition to Mechanical Engineering Matt Bertke, Paul DeMott, Patrick Hertzke, Will Sirokman 7 December 2004 AME 470: Senior Design ASME Bulk Material Transporter TEAM BURJA Executive Summary ASME Student Design Competition: Bulk Material Transporter Critical Constraints in addition to Requirements Early Concept Development Critical Design Issues Strengths in addition to Weaknesses Failure Modes Future Development TEAM BURJA ASME Problem Description Objective TEAM BURJA Design a remote-controlled vehicle to navigate the stair course. Transport a granular payload from the starting area in addition to deliver it to the receiving box. Transport as much grain as possible in a 10-minute time period.
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ASME Problem Description Critical Requirements in addition to Constraints TEAM BURJA Vehicle dimensions must not exceed 25 cm x 25 cm x 30 cm. (ASME) Energy sources limited to eight 1.5 V batteries or ten 1.2 V batteries, in addition to two 9 V batteries. (ASME) Remotely controlled via radio or umbilical. (ASME) $500 budget. (ND) 14 week concept development in addition to manufacturing period. (ND) Early Concept Development Primary Design Objectives TEAM BURJA High Payload Efficient Operation Intelligent Electronics Primary Design Objectives: Allows variable motor-speed control using potentiometers. Ability to automate stair navigation tasks using position sensor(s). Provides a flexible software plat as long as m that can be modified as long as a number of different tasks. Early Concept Development Preliminary Concepts TEAM BURJA Sensitive to changes in center of mass. High torque required as long as swing arm. Swing Arm Concept Hinged Tread Concept Simple design in addition to operation. High payload capacity. Complex mechanical design. Low grain capacity. Fluid motion up stairs. High traction. STRENGTHS STRENGTHS WEAKNESSES WEAKNESSES
Early Concept Development Prototype Testing in addition to Final Design TEAM BURJA A LEGO prototype of the single swing arm design to test functionality. Design flaw discovered: Both lifting actions of swing arm require different locations of center of mass. Solution: New design with two sets of swing arms. Final Design utilizes short front swing arms in addition to long rear swing arms. Swing arms are geared together 180° out of phase. Revised LEGO Prototype/Final Climbing Process 1) Align Vehicle 2) Front Arms Down 3) Rear Arms Down 4) Drive as long as ward/Repeat Final Concept in addition to Prototype Videos of Prototype Operation TEAM BURJA Critical Design Issues Swing Arm Geometry TEAM BURJA Applies a moment about the rear wheels mechanical advantage maximized if front arm axle is farther as long as ward. Axle placement limited by reverse rotation of the front swing arm. Shorter arm requires less motor torque. Front Swing Arm: Design Considerations Design Choice Axle located at center of vehicle wheelbase. 3.3 arm length. Rear Swing Arm: Design Considerations Applies a moment about the front wheels mechanical advantage maximized if front arm axle is farther back. Shorter arm requires less motor torque, but arm must extend at least 4 below bottom of treads due to stair height. Design Choice Axle located 1.25 as long as ward of rear wheel axle. 5.25 arm length.
Critical Design Issues Swing Arm Torque TEAM BURJA Pivot Point O Static in addition to dynamic as long as ce analyses conducted to predict necessary arm torque. Longer rear swing arm requires more torque than front swing arm. Based on a 10 lb combined vehicle in addition to payload weight, static lifting torque was estimated at > 2.4 Nm. A 4.0 Nm gear motor was incorporated into final prototype due to availability in addition to to increase payload capacity. Critical Design Issues Center of Mass TEAM BURJA Center of Mass: Acceptable domain as long as the vehicle center of mass is dictated by swing arm geometry. Must lie between the two swing arm axles (3 apart). Cannot lie behind the rear tread wheel when the vehicle is inclined. RESULT: Final prototype is balanced such that it can operate successfully with a full payload or completely empty. Critical Design Issues Other Important Issues TEAM BURJA Rice Container Design: Unique geometry of container is defined by ASME constraint. Rice Door Mechanism: A counter-weighted lever mechanism was implemented to gain mechanical advantage due to a solenoid that was weaker than expected. Rice container in white fits just within the ASME constraint size (gray box) Vehicle successfully delivering a full payload of rice (approximately 7lbs) Rice Container Design: Unique geometry of container is defined by ASME constraint. Rice Door Mechanism: A counter-weighted lever mechanism was implemented to gain mechanical advantage due to a solenoid that was weaker than expected.
Critical Design Issues Electronics TEAM BURJA PHILOSOPHY Use a microprocessor in addition to automation to make operation simple in addition to precise. APPLICATION Microprocessor adds precision Pulse width modulation (PWM) in addition to H-bridges allow variable tread speed. Angular encoder allows precise, computer controlled arm movement. Automation Automated algorithm is initiated by user. User can interrupt computer or override with manual control. Critical Design Issues Electronics TEAM BURJA PROGRAMMING OF MINI-MAX PROCESSOR DESIGNED FOR FUNCTIONALITY Functions built in addition to tested individually. Functions can be easily added/removed. CODE STRUCTURE Main loop comprises seven function calls All input evaluated be as long as e change in output. High speed evaluation ensures that input is not missed. (Rechecks inputs every cycle (at about 2000 Hz) Code allows simultaneous inputs in addition to conflicting comm in addition to s. Solenoid Mini-Max Microprocessor 5V 9V Battery 12V Battery 9V Battery Manual swing-arm fwd Manual swing-arm rev Ascend Algorithm Descend Algorithm Motor Brake Potentiometer 1 Potentiometer 2 Reset 4.7k 4.7k 4.7k 4.7k 4.7k 10k 4.7k 10k 2A Fuse 2A Fuse 2A Fuse H-Bridge 1 H-Bridge 2 H-Bridge 3 Rotary Encoder Regulator Drive Motor L Drive Motor R Swing Arm CIRCUIT LAYOUT Power Input. Two 9V in addition to one 12V battery. Umbilical Inputs. Pull down (4.7k resistors). Rotary Encoder Input. Outputs. Signal to H-Bridges. Motors. Driven by H-Bridges. Solenoid. Separate circuit.
Final Concept in addition to Prototype Strengths of Concept in addition to Prototype TEAM BURJA OVERALL Robust design High capacity 8 lb per trip Climbs quickly in addition to efficiently – 3 minute round trip Automated in addition to programmable TREADS Tread teeth provide lever effect Independent, variable speed control SWING ARM MECHANISM Accurate, computer controlled angular rotation Applies strong, consistent as long as ce Aligns vehicle as it lifts DUMPING MECHANISM Reliable latched mechanism Efficient: gravity assisted fall minimizes energy usage Final Concept in addition to Prototype Weaknesses of Concept in addition to Prototype TEAM BURJA WEAKNESSES OF FINAL CONCEPT Complexity of design 288 parts Large number of manufactured parts 20 different parts Heavy 7 lb High Cost over $500 WEAKNESSES OF PROTOTYPE Unknown electrical problems: interference, shorts, over heating – Result: Automation disabled to simplify electronics No variable speed reverse Inefficient in addition to error prone turning procedure Poor traction of flat surface of stairs Final Concept in addition to Prototype Likely Failure Modes TEAM BURJA RICE DUMP FAILURE Dumps without button press Human bumps latch (unresolved) Fails to dump on button press LOSS OF CONTROL Hardware failure Electronic interference/other issue (unresolved) Code failure Maximum H-Bridge frequency exceeded (may be unresolved reverse PWM disabled)
Final Concept in addition to Prototype Future Development TEAM BURJA FUTURE ELECTRONICS DEVELOPMENT The use of the microprocessor provides potential as long as further refinement Shield electronics from heat, interference, impact Incorporate reverse PWM Incorporate automation climbing algorithm Refine turning procedure FUTURE MECHANICAL MODIFICATIONS Replace shafts with precision ground shafting Re-fabricate in addition to realign tread assemblies Improve swing arm clamping mechanism Add safety latch to rice bin Modify rice bin to ensure complete release of rice Seal chassis in addition to electronics from rice Questions TEAM BURJA
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