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DC Permanent Magnet Motors A tutorial winch design

DC Permanent Magnet Motors A tutorial winch design. David Giandomenico Lynbrook High School Robotics FIRST Team #846 DGiandomenico@lynbrookrobotics.com (408)343-1183. 2010 Breakaway. 2004 FIRST Frenzy: Raising the Bar. What We Want. Weight: Distance: Time (speed):. 130 lbs 1.5 feet

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DC Permanent Magnet Motors A tutorial winch design

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  1. DC Permanent Magnet MotorsA tutorial winch design David Giandomenico Lynbrook High School Robotics FIRST Team #846 DGiandomenico@lynbrookrobotics.com (408)343-1183 David Giandomenico - FIRST #846

  2. 2010 Breakaway David Giandomenico - FIRST #846

  3. 2004 FIRST Frenzy: Raising the Bar David Giandomenico - FIRST #846

  4. What We Want. • Weight: • Distance: • Time (speed): 130 lbs 1.5 feet 5 seconds David Giandomenico - FIRST #846

  5. What We’ve Got:Some of the Motors supplied in FIRST Robotics Kit David Giandomenico - FIRST #846

  6. “CIM” Motor Specification David Giandomenico - FIRST #846

  7. “CIM” Motor Performance David Giandomenico - FIRST #846

  8. No Load Speed No Load Current Stall Torque “CIM” Motor Performance Stall Current David Giandomenico - FIRST #846

  9. FUSE Limits on Motor Power Stall Current 40 AFuse Limit ~100 Oz-In David Giandomenico - FIRST #846

  10. Kit Motors – Which One? All Data at 12VDC David Giandomenico - FIRST #846

  11. Motors - Sorted by Power David Giandomenico - FIRST #846

  12. Choosing a motor based onMaximum Output Power • Calculate Energy required to lift load. • Given the Time & Energy, calculate the mechanical Power required. • Boost Power requirement to adjust for Friction in the gearbox and elsewhere. • Choose a motor whose Maximum Output Power is at least 4/3 * (safety margin) David Giandomenico - FIRST #846

  13. David Giandomenico - FIRST #846

  14. Motor Selection David Giandomenico - FIRST #846

  15. www.johnsonmotor.com David Giandomenico - FIRST #846

  16. 2011 Fisher Price Motor All Data at 12VDC Convert oz-in to N-m: 1 oz-in = 0.007061552 N-m David Giandomenico - FIRST #846

  17. Fisher Price Motor 2010 V=12VDC From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  18. What is Torque? But isn’t that “Work” David Giandomenico - FIRST #846

  19. Units of Work vs. Torque • Work (Energy) • Torque ft-lbf, Joules (=N-m), KWh, … pound feet(lbf-ft), ft-lbf, oz-in, N-m … David Giandomenico - FIRST #846

  20. Work in a Rotating System Force T r David Giandomenico - FIRST #846

  21. Power, Torque & Speed David Giandomenico - FIRST #846

  22. Fisher Price Motor 2011 V=12VDC (speed,torque) From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  23. Fisher Price Motor 2011 V=12VDC From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  24. V=Rated Voltage From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  25. Speed & Torque in a DC PM Motor • Let ={0,100%} such that David Giandomenico - FIRST #846

  26. V=Rated Voltage From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  27. Speed & Torque in a DC PM Motor Or, w/o calculus, Max occurs between two roots of quadratic, at =0, =1 that is, =½ or equivalently, when=50% Using calculus, Max Power occurs when: David Giandomenico - FIRST #846

  28. V=Rated Voltage 75% From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  29. Max Power in a DC PM Motor David Giandomenico - FIRST #846

  30. 2011 Fisher Price Motor All Data at 12VDC David Giandomenico - FIRST #846

  31. Fisher Price Motor 2011 V=12VDC From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  32. Fisher Price Motor 2011 V=12VDC Current rises linearly with Torque From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  33. Motor Current Where α is the % No Load speed David Giandomenico - FIRST #846

  34. Electrical Power David Giandomenico - FIRST #846

  35. Fisher Price Motor 2011 V=12VDC Input power is Current X Voltage From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  36. Fisher Price Motor 2010 V=12VDC From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  37. Fisher Price Motor 2010 V=12VDC From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  38. Fisher Price Motor 2011 V=12VDC From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  39. Fisher Price Motor 2011 V=12VDC From FIRST_MOTOR_CALC.xls David Giandomenico - FIRST #846

  40. DC PM Motor Summary • Max Power occurs at 50% No-Load Speed • Best efficiency typically occurs at about 80%-93% No-Load Speed • Most DC PM Motors will overheat if operated continuously at speeds less than 50% when full voltage is applied. David Giandomenico - FIRST #846

  41. Gear Loss Estimate Suppose we have n=3 inline sets of gears, each with a 4:1reduction. What is the total efficiency if each gear set loses 4%? T = in or T = (100%-4%)3= 88.5% David Giandomenico - FIRST #846

  42. When x is small, David Giandomenico - FIRST #846

  43. Estimate of how many gear sets. • Suppose we want a gear reduction of 1200. How many gear sets with a reduction of 3 do we need? • Solve 3N = 1200 • N = ln(1200)/ln(3) = 6.45 David Giandomenico - FIRST #846

  44. Gear loss estimate We need 6.45 3:1 gear sets. Assuming a loss of 4% for each gear set, T = in or T = (1-4%)6.45= 76.8% David Giandomenico - FIRST #846

  45. Putting it all together • Choose a winch drum size • Calculate the drum rpm • Choose the % motor operating speed • Calculate the required gear reduction to operate at that speed • Verify the output winch line force meets or exceeds the original specification, including gear box losses David Giandomenico - FIRST #846

  46. Winch Design Specification David Giandomenico - FIRST #846

  47. Winch Drum Speed David Giandomenico - FIRST #846

  48. Determine the Gear Reduction David Giandomenico - FIRST #846

  49. Gear Loss Estimate David Giandomenico - FIRST #846

  50. Verify We Meet or Exceed Pull Strength Specification David Giandomenico - FIRST #846

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