Transcript 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.
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