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Comparative Analysis of Energy Flow and Strength in Engineering Prototype Systems

This review discusses the energy flow, power consumption, and failure analysis of various engineering components in a prototype system. Key points include the assessment of shear and bending forces on axle braces, strengths of materials used (e.g., Core-Cell Foam, balsa wood, fiberglass, and carbon fiber), and electronics power consumption. Additionally, motor performance and CoT (Cost of Transportation) calculations are discussed to ensure efficiency. The suitability of materials and designs in achieving system goals while maintaining integrity and safety are highlighted.

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Comparative Analysis of Energy Flow and Strength in Engineering Prototype Systems

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  1. Week 7 Engineering Review Owen Accas - Dan Crossen - Rebecca Irwin - Madeline Liccione - Hao Shi

  2. Detailed Block Diagram

  3. Energy Flow Graph

  4. Double Stance Time Propagator (RK 4)

  5. Single Stance a o

  6. Current Prototype v.s. Proposed System Simulation Comparison

  7. Axle • 10mm diameter aluminum • Assume no tension/compression or insignificant tension/compression • Shear modulus = 26 GPa • Area = Pi*(.01m)^2=pi*10^-4 m^2 • Shear failure at ~204 million Newtons which is approximately 45.8 million lbs • This strength will more than account for the forces seen on the axle in shear

  8. Braces • Worst case: 1 plate rigid, 1 side has full torque • Full torque = (40 lbs/spring)*(2 springs)*1.5 in =120 in-lbs • Bending force on each brace =(120 in-lbs)/(14 inches)/(5 braces) =1.714 lbs/brace, therefore assume 2.5 lbs with a safety factor

  9. Choosing Braces • Shear Strength = 10,500 PSI • With 100 pounds, we would need a cross sectional area of .00952 in^2 or greater to avoid failure • With 2.5 lbs (calculated on previous slide), we would see no failure at all, as the pvc we are using has an area of .256 in^2 • These will ad .172 kg to entire frame, but add .0217 kg-m^2 of inertia (about 20% increase)

  10. Plate Selection (Core) • The core material we intend to use is Core-Cell Foam, a boat building and repair supply • Relatively inexpensive • Very strong • Readily attainable • Thin • Low density

  11. Plate Selection (Core) • Balsa wood is also a popular core material for composites applications • Deemed to be more expensive • Not as strong • Similarly thin • Higher density than Core-cell

  12. Plate Selection (Composite) • SAE Boeing Carbon fiber is our selected coat • Incredibly strong, especially in tension and compression (along the weave) • Very thin • Very consistent • Aesthetically pleasing • Would be expensive (~34.99 per 50” x 30”) • We have a free connection to needed amount

  13. Plate Selection (Composite) • Fiberglass was another option for our top coat • Less expensive than carbon, if we had to buy • Not quite as strong • Most fiber weaves are more random • Similar material properties, carbon is free

  14. Power Consumption of Electronics • 2 Gyroscopes (L3GD20) – 3.3 V @ 7 mA = .0462 W • 1 Encoder (E5)– 5 V @ 50 mA = .25 W • Current Sensor (ACS714) – .000012 V @ 10 mA = ~negligible • Microcontroller = 0.246mW Total Power = 0.307W

  15. Encoder • Requested Specs: <.5 Deg/Sec accuracy (doesn't make sense, since we will go through about 360 Deg in a second) • E5 Encoder: 1024 CpR=.35 Deg sensitivity • E5 Encoder: 292.9 RPS maximum (300KHz max count frequency)

  16. Gyroscope • Requested Specs: <.1 Deg/Sec accuracy    • L3GD20: +/- 500 Deg/Sec and 400kHz sampling means resolution of .00125 deg • This is the same Gyro as is currently used in the prototype

  17. Batteries • Using NiMH batteries for safety and for voltage matching (1.2V steps), as well as cost (<$3 per battery), ease of replacement, and rechargeablity.

  18. Current and Voltage Sensors • No specific specs provided • Sampling rate of 500 Hz depends upon processor • Using error of 2% as spec

  19. Motor (part 1) • 14.8 V @ 4.1 Amps • If this motor were on all the time, we would be looking at 61 W, and a cost of transport of approximately 3.36, way over our goal. • Therefore, we would like to estimate the CoT when our motor is only on for 1/10th of a second • CoT = .358

  20. Motor (part 2) • There are certain ways to obtain our goal of .05 CoT • We looked at getting a larger motor (increased performance & weight). This decreases the amount of time the motor must be active (1/40th of a second) and increases the denominator of CoT equation. • Can rotate ¼ turn in .00625, but we are accounting for negating torque so we assume .02 seconds (max of 2500 RPMs) • CoT= (90 W*(.02 s)+.5)/(51 N*.5 m)= .9

  21. Fasteners

  22. Microprocessor Selection

  23. Bill of Materials (1)

  24. Bill of Materials (2)

  25. Bill of Materials (3)

  26. Questions/Concerns?

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