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Interpreting the Motor Curve with Practical Application

Steven Jorgensen Chani Martin. Interpreting the Motor Curve with Practical Application. Motor Characteristics. Stall torque – Maximum Torque output with 0 rotational speed. Stall Current – Current drawn at stall torque Free Speed – Fastest Free spin of the motor with 0 load.

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Interpreting the Motor Curve with Practical Application

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  1. Steven Jorgensen Chani Martin Interpreting the Motor Curve with Practical Application

  2. Motor Characteristics • Stall torque – Maximum Torque output with 0 rotational speed. • Stall Current – Current drawn at stall torque • Free Speed – Fastest Free spin of the motor with 0 load. • Motor Power- Mechanical power motor has.

  3. Motor Curve Demonstration • Look and explain F-P Motor Curve here • Show Graphical Representation • Stall Torque • Stall Current • Free Speed • Maximum Power

  4. Designing Around Motor Specifications • Calculate Power Requirement • Select Appropriate Motor • Find the Working Torque and Apply Gear Ratio • Calculate Effective(Actual) Gear Ratio • Calculate Effective (Actual) Power Output

  5. FRC Problem • Lift a 5lb Ball 7ft in the Air within 6 seconds

  6. Step 1: Power Requirement • Power = Torque * Angular Velocity • P = Τω = (69N-m)(0.393rad/s) = 27.117 Watts • Arm Parallel to Ground requires most torque

  7. Step 2: Select Appropriate Motor • Maximum Available Power for 2010 Motors • CIM (337 Watts at 2655rpm, 172oz-in) • Fisher Price (185 Watts) • Denso (22 Watts) • Mabuchi Motor (30 Watts)

  8. Step 3: Working Torque w/ Gear Ratio • Gear Ratios – Transmit Loads at the Gear’s Teeth • F-P Stall Torque = 63.4 oz-in • Design around 20%-50% of stall torque so that gear ratio reflects a torque load on the motor that is near max power. • 45% Stall Torque = 28.98oz-in • 630 oz-in / 28.98 oz-in = • 21.74:1 Gear Ratio • With this Gear Ratio F-P motor only experiences 28.98oz-in of load

  9. Step 4: Effective Gear Ratio • Effective Gear Ratio = Motor Power * Total Component Efficiency • Each Gearing Stage Loses 10% Efficiency • Two Stages (7:1 to 4:1) • 7*90% * 4 * 90% = 22.68:1 Effective Gear Ratio

  10. Step 5: Effective Power • F-P Motor Experiences 28.98 oz-in • Refer to Motor Curve to find Power Output of F-P motor at this torque input. • Power @ 28.98 oz-in Torque = 180 Watts • Effective Power = Motor Power * Efficiency • E.P = Motor Power * (Gear Ratio Efficiency) * (Motor Efficiency) • E.P. = 180 * (0.9*0.9) * (0.5) = 72.9 Watts • Lifting Ball only requires 27.11 Watts

  11. Conclusion • Power Requirement • 27.11 Watts • Select Appropriate Motor • F-P motor (190 Watts Available) • Working Torque • 28.98 oz-in Working Torque. Needs 21.74 GR • Calculate Effective(Actual) Gear Ratio • 22.68 G.R. After Efficiency Loss • Calculate Effective (Actual) Power Output • 71.9 Watts Available after Efficiency Loss

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