December 10, 2011 David Giandomenico - FIRST #846 DC Permanent Magnet Motors A tutorial winch design...
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Transcript of December 10, 2011 David Giandomenico - FIRST #846 DC Permanent Magnet Motors A tutorial winch design...
December 10, 2011 David Giandomenico - FIRST #846
DC Permanent Magnet MotorsA tutorial winch design
David Giandomenico
Lynbrook High School Robotics
FIRST Team #846
(408)343-1183
2010 Breakaway
December 10, 2011 David Giandomenico - FIRST #846
December 10, 2011 David Giandomenico - FIRST #846
2004 FIRST Frenzy: Raising the Bar
December 10, 2011 David Giandomenico - FIRST #846
What We Want.
• Weight:
• Distance:
• Time (speed):
130 lbs
1.5 feet
5 seconds
December 10, 2011 David Giandomenico - FIRST #846
What We’ve Got:Some of the Motors supplied in FIRST Robotics Kit
December 10, 2011 David Giandomenico - FIRST #846
“CIM” Motor Specification
December 10, 2011 David Giandomenico - FIRST #846
“CIM” Motor Performance
December 10, 2011 David Giandomenico - FIRST #846
“CIM” Motor Performance
StallTorque
StallTorque
No LoadCurrentNo LoadCurrent
No Load Speed
No Load Speed
StallCurrentStallCurrent
December 10, 2011 David Giandomenico - FIRST #846
FUSE Limits on Motor Power
StallCurrentStallCurrent
40 AFuse Limit40 AFuse Limit
~100 Oz-In~100 Oz-In
December 10, 2011 David Giandomenico - FIRST #846
Kit Motors – Which One?
Make / ModelMax Power
(Watts)Stall Torque
(oz-in) Free Speed
(RPM) Free Current
(A)Stall Current
(A)
BaneBots RS395 48.1 16.7 15,500 0.5 15
BaneBots RS540 123.5 39.5 16,800 1 42
BaneBots RS550 253.5 70.6 19,300 1.4 85
BaneBots RS775 83.1 61.1 7,300 1.1 30
CIM FR801-001 340.1 344.0 5,310 2.7 133
Denso 262100-3030-(Right) 23.5 1501.1 84 1.8 18.6
Denso 262100-3040-(Left) 23.5 1501.1 84 1.8 21
Fisher-Price 00801-0673-(2011) 291.6 75.4 20,770 0.82 108.7
Fisher-Price 00968-9015-(2010) 185.0 63.7 15,600 1.25 70
All Data at 12VDC
December 10, 2011 David Giandomenico - FIRST #846
Motors - Sorted by Power
Make / ModelMax Power
(Watts)Stall Torque
(oz-in) Free Speed
(RPM) Free Current
(A)Stall Current
(A)
CIM FR801-001 340.1 344.0 5,310 2.7 133
Fisher-Price 00801-0673-(2011) 291.6 75.4 20,770 0.82 108.7
BaneBots RS550 253.5 70.6 19,300 1.4 85
Fisher-Price 00968-9015-(2010) 185.0 63.7 15,600 1.25 70
BaneBots RS540 123.5 39.5 16,800 1 42
BaneBots RS775 83.1 61.1 7,300 1.1 30
BaneBots RS395 48.1 16.7 15,500 0.5 15
Denso 262100-3030-(Right) 23.5 1501.1 84 1.8 18.6
Denso 262100-3040-(Left) 23.5 1501.1 84 1.8 21
December 10, 2011 David Giandomenico - FIRST #846
Choosing a motor based onMaximum Output Power
1. Calculate Energy required to lift load.
2. Given the Time & Energy, calculate the mechanical Power required.
3. Boost Power requirement to adjust for Friction in the gearbox and elsewhere.
4. Choose a motor whose Maximum Output Power is at least 4/3 * (safety margin)
December 10, 2011 David Giandomenico - FIRST #846
Winch DesignInput parameters
Weight to lift (lbs) 130Height (ft) to lift in time T 1.5Time to lift seconds 5
Convert to MKS (metric system)Mass to lift (Kgs) 59.1Weight To lift (Newtons) 579.1Height (m) 0.457Time to Lift 5
Potential EnergyKp = mgh (Joules) 264.8
Power needed to gain above energy in time TP = Kp / T (Watts) 53.0
Weight & Mass conversions:1Kg = 2.2 lbs-mass
Weight in Newtons = mass x 'g'where g=9.8 m/s/sso a 1Kg mass weighs 9.8 Newtons
December 10, 2011 David Giandomenico - FIRST #846
Motor Selection
Make / ModelMax Power
(Watts)Stall Torque
(oz-in) Free Speed
(RPM) Free Current
(A)Stall Current
(A)
CIM FR801-001 340.1 344.0 5,310 2.7 133
Fisher-Price 00801-0673-(2011) 291.6 75.4 20,770 0.82 108.7
BaneBots RS550 253.5 70.6 19,300 1.4 85
Fisher-Price 00968-9015-(2010) 185.0 63.7 15,600 1.25 70
BaneBots RS540 123.5 39.5 16,800 1 42
BaneBots RS775 83.1 61.1 7,300 1.1 30
BaneBots RS395 48.1 16.7 15,500 0.5 15
Denso 262100-3030-(Right) 23.5 1501.1 84 1.8 18.6
Denso 262100-3040-(Left) 23.5 1501.1 84 1.8 21
Make / ModelMax Power
(Watts)Stall Torque
(oz-in) Free Speed
(RPM) Free Current
(A)Stall Current
(A)
CIM FR801-001 340.1 344.0 5,310 2.7 133
Fisher-Price 00801-0673-(2011) 291.6 75.4 20,770 0.82 108.7
BaneBots RS550 253.5 70.6 19,300 1.4 85
Fisher-Price 00968-9015-(2010) 185.0 63.7 15,600 1.25 70
BaneBots RS540 123.5 39.5 16,800 1 42
BaneBots RS775 83.1 61.1 7,300 1.1 30
BaneBots RS395 48.1 16.7 15,500 0.5 15
Denso 262100-3030-(Right) 23.5 1501.1 84 1.8 18.6
Denso 262100-3040-(Left) 23.5 1501.1 84 1.8 21
Make / ModelMax Power
(Watts)Stall Torque
(oz-in) Free Speed
(RPM) Free Current
(A)Stall Current
(A)
CIM FR801-001 340.1 344.0 5,310 2.7 133
Fisher-Price 00801-0673-(2011) 291.6 75.4 20,770 0.82 108.7
BaneBots RS550 253.5 70.6 19,300 1.4 85
Fisher-Price 00968-9015-(2010) 185.0 63.7 15,600 1.25 70
BaneBots RS540 123.5 39.5 16,800 1 42
BaneBots RS775 83.1 61.1 7,300 1.1 30
BaneBots RS395 48.1 16.7 15,500 0.5 15
Denso 262100-3030-(Right) 23.5 1501.1 84 1.8 18.6
Denso 262100-3040-(Left) 23.5 1501.1 84 1.8 21
December 10, 2011 David Giandomenico - FIRST #846
www.johnsonmotor.com
December 10, 2011 David Giandomenico - FIRST #846
2011 Fisher Price Motor
Make / ModelMax Power
(Watts)Stall Torque
(oz-in) Free Speed
(RPM) Free Current
(A)Stall Current
(A)
Fisher-Price 00801-0673-(2011) 291.6 75.4 20,770 0.82 108.7
All Data at 12VDC
Make / ModelMax Power
(Watts)Stall Torque
(N-m) Free Speed
(RPM) Free Current
(A)Stall Current
(A)
Fisher-Price 00801-0673-(2011) 291.6 0.532 20,770 0.82 108.7
Convert oz-in to N-m: 1 oz-in = 0.007061552 N-m
December 10, 2011 David Giandomenico - FIRST #846
Fisher Price Motor 2010
From FIRST_MOTOR_CALC.xls
V=12VDC
December 10, 2011 David Giandomenico - FIRST #846
What is Torque?
dFW inline
dFT
But isn’t that “Work”
December 10, 2011 David Giandomenico - FIRST #846
Units of Work vs. Torque
• Work (Energy)
• Torquepound feet(lbf-ft), ft-lbf, oz-in, N-m …
ft-lbf, Joules (=N-m), KWh, …
December 10, 2011 David Giandomenico - FIRST #846
Work in a Rotating System
€
W = Tθ
€
W =v F ×
r r θ
€
W = (v F ×
r r )θ
€
W =r F ⋅
r x Force
€
θr
T
December 10, 2011 David Giandomenico - FIRST #846
Power, Torque & Speed
TP
60
RPM 2TP
timedistForceP /
trFP /)( θtrFP /θ
December 10, 2011 David Giandomenico - FIRST #846From FIRST_MOTOR_CALC.xls
V=12VDC
(speed,torque)
Fisher Price Motor 2011
December 10, 2011 David Giandomenico - FIRST #846From FIRST_MOTOR_CALC.xls
V=12VDC
Fisher Price Motor 2011
December 10, 2011 David Giandomenico - FIRST #846
Normalized Speed vs Torque
0%10%20%30%40%50%60%70%80%90%
100%
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Torque (% Stall Torque)
% N
o L
oad
Spee
d
From FIRST_MOTOR_CALC.xls
V=Rated Voltage
December 10, 2011 David Giandomenico - FIRST #846
Speed & Torque in a DC PM Motor
• Let ={0,100%}
such that
)1()(
)(
)(
s
s
s
TT
NN
December 10, 2011 David Giandomenico - FIRST #846
Normalized Speed vs Torque
0%10%20%30%40%50%60%70%80%90%
100%
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Torque (% Stall Torque)
% N
o L
oad
Spee
d
From FIRST_MOTOR_CALC.xls
V=Rated Voltage
December 10, 2011 David Giandomenico - FIRST #846
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%
)()()( TP
Using calculus, Max Power occurs when:
)21()(
0
ssTd
dP
)1()( ssTP
December 10, 2011 David Giandomenico - FIRST #846From FIRST_MOTOR_CALC.xls
V=Rated Voltage
75%
December 10, 2011 David Giandomenico - FIRST #846
Max Power in a DC PM Motor
22ss
Max
TP
604
2 max
RPMs
Max
NTP
December 10, 2011 David Giandomenico - FIRST #846
2011 Fisher Price Motor
All Data at 12VDC
Make / ModelMax Power
(Watts)Stall Torque
(N-m) Free Speed
(RPM) Free Current
(A)Stall Current
(A)
Fisher-Price 00801-0673-(2011) 291.6 0.532 20,770 0.82 108.7
December 10, 2011 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
December 10, 2011 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
Current rises linearly with Torque
December 10, 2011 David Giandomenico - FIRST #846
Motor Current
Where α is the % No Load speed
)1)(()( oso IIII
December 10, 2011 David Giandomenico - FIRST #846
Electrical Power
VIP
December 10, 2011 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
Input power is Current X Voltage
December 10, 2011 David Giandomenico - FIRST #846
Fisher Price Motor 2010
From FIRST_MOTOR_CALC.xls
V=12VDC
December 10, 2011 David Giandomenico - FIRST #846
Fisher Price Motor 2010
From FIRST_MOTOR_CALC.xls
V=12VDC
December 10, 2011 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
December 10, 2011 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
December 10, 2011 David Giandomenico - FIRST #846
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.
December 10, 2011 David Giandomenico - FIRST #846
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%
December 10, 2011 David Giandomenico - FIRST #846
When x is small,
€
1− x( )n
≈1− nx
1x
December 10, 2011 David Giandomenico - FIRST #846
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
December 10, 2011 David Giandomenico - FIRST #846
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%
December 10, 2011 David Giandomenico - FIRST #846
Putting it all together
1. Choose a winch drum size
2. Calculate the drum rpm
3. Choose the % motor operating speed
4. Calculate the required gear reduction to operate at that speed
5. Verify the output winch line force meets or exceeds the original specification, including gear box losses
December 10, 2011 David Giandomenico - FIRST #846
Winch Design Specification
Input parametersWeight to lift (lbs) 130Height (ft) to lift in time T 1.5Time to lift seconds 5
Convert to MKS (metric system)Mass to lift (Kgs) 59.1Weight To lift (Newtons) 579.1Height (m) 0.457Time to Lift 5
December 10, 2011 David Giandomenico - FIRST #846
Winch Drum SpeedWinch Line Speed
Distance (m) 0.4572Time 5Speed (m/s) 0.0914
Drum size (dictated by factors such as cable)Diameter (inches) 6Diameter (m) 0.152Circumference (m) 0.479
Drum speedRevolutions / second 0.191Revolutions / minute (rpm) 11.46
December 10, 2011 David Giandomenico - FIRST #846
Determine the Gear ReductionDrum speed
Revolutions / second 0.191Revolutions / minute (rpm) 11.46
Motor spec at 12VDCNo load speed 20770 RPMStall Torque 75.4 oz0inStall Torque (1 Oz-In= 0.007061552 N-m) 0.532N-mMax Power Output 289.5 WFree Current 0.82 AStall Current 108.7 A
Operating Point at FUSE currentat 20A 17.8%at 30A 27.0%at 40A 36.3%
Select Motor Speed and Torque% motor speed 90%Motor current 11.6 AMotor Speed 18693 rpmTorque 0.0532 N-mPower out 104.2 WRequired Gear Reduction 1631.3
Required Gear Reduction 1631.3
Loss estimate assuming 'n' small gear setsIndividual gear set reduction ratio 4 times% Loss per gear set 5%
Number of gear reductions 5.336 setsTotal estimated gear efficiency 76.06%
December 10, 2011 David Giandomenico - FIRST #846
Gear Loss Estimate
Winch line output at speedMotor torque at speed (above) 0.0532 N-mTorque after gearbox (no loss) 86.86 N-m
After gear box losses 66.06 N-mForce on Line 866.92 NForce on Line (lbs) 194.61 lbs
December 10, 2011 David Giandomenico - FIRST #846
Verify We Meet or Exceed Pull Strength Specification
December 10, 2011 David Giandomenico - FIRST #846
Feat Accomplished!
194 lb exceeds required spec of 130lbs
December 10, 2011 David Giandomenico - FIRST #846
More than you wanted to know about
Robot Winch Design
David Giandomenico
Lynbrook High School Robotics
FIRST Team #846
(408)343-1183
December 10, 2011 David Giandomenico - FIRST #846
Addendum: Interest or Time permitting
December 10, 2011 David Giandomenico - FIRST #846
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December 10, 2011 David Giandomenico - FIRST #846
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December 10, 2011 David Giandomenico - FIRST #846
Pascal’s Triangle
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December 10, 2011 David Giandomenico - FIRST #846
Binomial Theorem
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