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.

Motor Power- Mechanical power motor has.

Motor Curve Demonstration

  Look and explain F-P Motor Curve here Show Graphical Representation  Stall Torque  Stall Current  Free Speed  Maximum Power

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

FRC Problem

 Lift a 5lb Ball 7ft in the Air within 6 seconds

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

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)

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

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

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

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