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DC Permanent Magnet Motors A tutorial winch design. David Giandomenico Lynbrook High School Robotics FIRST Team #846 [email protected] (408)343-1183. 2010 Breakaway. 2004 FIRST Frenzy: Raising the Bar. What We Want. Weight: Distance: Time (speed):. 130 lbs 1.5 feet - PowerPoint PPT Presentation
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David Giandomenico - FIRST #846
DC Permanent Magnet MotorsA tutorial winch design
David Giandomenico
Lynbrook High School Robotics
FIRST Team #846
(408)343-1183
August 10, 2013
2010 Breakaway
August 10, 2013 David Giandomenico - FIRST #846
August 10, 2013 David Giandomenico - FIRST #846
2004 FIRST Frenzy: Raising the Bar
August 10, 2013 David Giandomenico - FIRST #846
What We Want.• Weight:
• Distance:
• Time (speed):
130 lbs
1.5 feet
5 seconds
August 10, 2013 David Giandomenico - FIRST #846
What We’ve Got:Some of the Motors supplied in FIRST Robotics Kit
August 10, 2013 David Giandomenico - FIRST #846
Kit Motors – Which One?All Data at 12VDC 2013 choices (partial list!)
Make Model
Max Power (W)
Stall Torque (oz-in)
Free Speed (rpm)
Free Current (A)
Stall Current (A)
AndyMark am-0912 179 61 16000 1.2 64
AndyMark am-0915 45 1209 198 0.6 22
BaneBots M7-RS775-18 273 113 13000 1.8 87
BaneBots M5-RS550-12 M5-RS550-12-B
254 71 19300 1.4 85
BaneBots M5-RS540-12 123 39 16800 1 42
BaneBots M7-RS775-12 83 61 7300 1.1 30
BaneBots M5-RS545-12 74 24 16800 0.9 21
BaneBots M3-RS395-12 48 17 15500 0.5 15
CIM FR801-001 337 343 5310 2.7 133
VEX Mini CIM 217-3371 229 198 6200 1.8 86
VEX bag motor 217-3351 149 57 14000 1.8 41
August 10, 2013 David Giandomenico - FIRST #846
Motors - Sorted by PowerMake Model
Max Power (W)
Stall Torque (oz-in)
Free Speed (rpm)
Free Current (A)
Stall Current (A)
CIM FR801-001 337 343 5310 2.7 133
BaneBots M7-RS775-18 273 113 13000 1.8 87
BaneBots M5-RS550-12 M5-RS550-12-B
254 71 19300 1.4 85
VEX Mini CIM 217-3371 229 198 6200 1.8 86
AndyMark am-0912 179 61 16000 1.2 64
VEX bag motor 217-3351 149 57 14000 1.8 41
BaneBots M5-RS540-12 123 39 16800 1 42
BaneBots M7-RS775-12 83 61 7300 1.1 30
BaneBots M5-RS545-12 74 24 16800 0.9 21
BaneBots M3-RS395-12 48 17 15500 0.5 15
AndyMark am-0915 45 1209 198 0.6 22
August 10, 2013 David Giandomenico - FIRST #846
“CIM” Motor Specification
August 10, 2013 David Giandomenico - FIRST #846
“CIM” Motor Performance
August 10, 2013 David Giandomenico - FIRST #846
“CIM” Motor Performance
StallTorque
No LoadCurrent
No Load Speed
StallCurrent
August 10, 2013 David Giandomenico - FIRST #846
Current Limits (fuse) on Motor Power
StallCurrent
40 AFuse Limit
~100 Oz-In
August 10, 2013 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)
August 10, 2013 David Giandomenico - FIRST #846
www.johnsonmotor.com
August 10, 2013 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
August 10, 2013 David Giandomenico - FIRST #846
Motor SelectionMake Model
Max Power (W)
Stall Torque (oz-in)
Free Speed (rpm)
Free Current (A)
Stall Current (A)
CIM FR801-001 337 343 5310 2.7 133
BaneBots M7-RS775-18 273 113 13000 1.8 87
BaneBots M5-RS550-12 254 71 19300 1.4 85
VEX Mini CIM 217-3371 229 198 6200 1.8 86
AndyMark am-0912 179 61 16000 1.2 64
VEX bag motor 217-3351 149 57 14000 1.8 41
BaneBots M5-RS540-12 123 39 16800 1 42
BaneBots M7-RS775-12 83 61 7300 1.1 30
BaneBots M5-RS545-12 74 24 16800 0.9 21
BaneBots M3-RS395-12 48 17 15500 0.5 15
AndyMark am-0915 45 1209 198 0.6 22
Make Model
Max Power (W)
Stall Torque (oz-in)
Free Speed (rpm)
Free Current (A)
Stall Current (A)
CIM FR801-001 337 343 5310 2.7 133
BaneBots M7-RS775-18 273 113 13000 1.8 87
BaneBots M5-RS550-12 254 71 19300 1.4 85
VEX Mini CIM 217-3371 229 198 6200 1.8 86
AndyMark am-0912 179 61 16000 1.2 64
VEX bag motor 217-3351 149 57 14000 1.8 41
BaneBots M5-RS540-12 123 39 16800 1 42
BaneBots M7-RS775-12 83 61 7300 1.1 30
BaneBots M5-RS545-12 74 24 16800 0.9 21
BaneBots M3-RS395-12 48 17 15500 0.5 15
AndyMark am-0915 45 1209 198 0.6 22
Make Model
Max Power (W)
Stall Torque (oz-in)
Free Speed (rpm)
Free Current (A)
Stall Current (A)
CIM FR801-001 337 343 5310 2.7 133
BaneBots M7-RS775-18 273 113 13000 1.8 87
BaneBots M5-RS550-12 254 71 19300 1.4 85
VEX Mini CIM 217-3371 229 198 6200 1.8 86
AndyMark am-0912 179 61 16000 1.2 64
VEX bag motor 217-3351 149 57 14000 1.8 41
BaneBots M5-RS540-12 123 39 16800 1 42
BaneBots M7-RS775-12 83 61 7300 1.1 30
BaneBots M5-RS545-12 74 24 16800 0.9 21
BaneBots M3-RS395-12 48 17 15500 0.5 15
AndyMark am-0915 45 1209 198 0.6 22
August 10, 2013 David Giandomenico - FIRST #846
What is Torque?
dFW inline
dFT
But isn’t that “Work?”
August 10, 2013 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, …
August 10, 2013 David Giandomenico - FIRST #846
Work in a Rotating System
Force
rT
August 10, 2013 David Giandomenico - FIRST #846
Power, Torque & Speed
TP
60RPM 2TP
timedistForceP /
trFP /)( trFP /
0.00 0.10 0.20 0.30 0.40 0.50 0.600
5000
10000
15000
20000
25000
Speed vs Torque
Torque (N-m)
Spee
d (R
PM)
August 10, 2013 David Giandomenico - FIRST #846From FIRST_MOTOR_CALC.xls
V=12VDC
(speed,torque)
Where is Max Power?Fisher Price Motor 2011
August 10, 2013 David Giandomenico - FIRST #846From FIRST_MOTOR_CALC.xls
V=12VDC
0.00 0.10 0.20 0.30 0.40 0.50 0.600
50
100
150
200
250
300
350
Output Power vs Torque
Torque (N-m)
Mec
hani
cal P
ower
(Wat
ts)
Maximum PowerFisher Price Motor 2011
Standardize through Normalization
August 10, 2013 David Giandomenico - FIRST #846
http://www.mabuchi-motor.co.jp http://www.johnsonmotor.com
August 10, 2013 David Giandomenico - FIRST #846
http://www.mabuchi-motor.co.jp
http://www.johnsonmotor.com
Simplified through Standardization
August 10, 2013 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 Lo
ad S
peed
V=Rated Voltage
85%+15%=100%
30%+70%=100%
50%+50%=100%
August 10, 2013 David Giandomenico - FIRST #846
Speed & Torque in a DC PM Motor
• Let ={0,100%}
such that
)1()(
)()(
s
s
s
TT
NN
August 10, 2013 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:
August 10, 2013 David Giandomenico - FIRST #846
Max Power in a DC PM Motor
604 2 max
RPMs
MaxNTP
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%0%
20%
40%
60%
80%
100%
120%
Output Power vs % Stall Torque
Torque (% Stall Torque)
Pow
er O
ut (%
Max
Pow
er)
August 10, 2013 David Giandomenico - FIRST #846
V=Rated Voltage
75%
August 10, 2013 David Giandomenico - FIRST #846
2011 Fisher Price Motor
All Data at 12VDC
Make / Model Max 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
0.00 0.10 0.20 0.30 0.40 0.50 0.600
50
100
150
200
250
300
350
Output Power vs Torque
Torque (N-m)
Mec
hani
cal P
ower
(Wat
ts)
August 10, 2013 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
0.00 0.10 0.20 0.30 0.40 0.50 0.600
200400600800
10001200140016001800
Input Power vs Torque
Torque (N-m)
Inpu
t Ele
ctric
al P
ower
(Wat
ts)
August 10, 2013 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
Current rises linearly with Torque
August 10, 2013 David Giandomenico - FIRST #846
Motor Current
Where α is the % No Load speed
)1)(()( oso IIII
August 10, 2013 David Giandomenico - FIRST #846
Electrical Power
VIP
0.00 0.10 0.20 0.30 0.40 0.50 0.600
200
400
600
800
1000
1200
1400
Input Power vs Torque
Torque (N-m)
Inpu
t Ele
ctric
al P
ower
(Wat
ts)
August 10, 2013 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
Input power is Current X Voltage
0.00 0.10 0.20 0.30 0.40 0.50 0.600
50
100
150
200
250
300
350
Output Power vs Torque
Torque (N-m)
Mec
hani
cal P
ower
(Wat
ts)
August 10, 2013 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
August 10, 2013 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
0.00 0.10 0.20 0.30 0.40 0.50 0.600
200
400
600
800
1000
1200
1400
Electrical Power In & Mechanical Power Out vs Torque
Torque (N-m)
Elec
trica
l Pow
er In
&
Mec
hani
cal P
ower
Out
(Wat
ts)
0.00 0.10 0.20 0.30 0.40 0.50 0.600%
10%20%30%40%50%60%70%80%
Efficiency vs Torque
Torque (N-m)
Effic
ienc
y
August 10, 2013 David Giandomenico - FIRST #846
Fisher Price Motor 2011
From FIRST_MOTOR_CALC.xls
V=12VDC
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%0%
10%20%30%40%50%60%70%80%
Efficiency vs Normalized Torque
Torque (% Stall Torque)
Effic
ienc
y
7%-15%
August 10, 2013 David Giandomenico - FIRST #846
Fisher Price Motor 2011
V=12VDC
August 10, 2013 David Giandomenico - FIRST #846
Normalized Efficiency for IDEAL motor
Max Efficiency
August 10, 2013 David Giandomenico - FIRST #846
Operating Point:
Efficiency:
0% 2% 4% 6% 8% 10%50%
60%
70%
80%
90%
100%
Io / Is
Bes
t Ope
ratin
g Po
int
...simplifying yields:
Derivation of: Max Efficiency
August 10, 2013 David Giandomenico - FIRST #846
Find Maximum :
Efficiency: Where:
Use Quadratic Formula to find roots:
August 10, 2013 David Giandomenico - FIRST #846
Derivation of: Max Efficiency continued
Substitute for (1-α) to get:
August 10, 2013 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.
August 10, 2013 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%
August 10, 2013 David Giandomenico - FIRST #846
When x is small, 1x
August 10, 2013 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
August 10, 2013 David Giandomenico - FIRST #846
Gear loss estimate
We need 6.45 3:1 gear sets. Assuming a loss of 5% for each gear set,
T = in
or
T = (1-5%)6.45 = 71.8%
August 10, 2013 David Giandomenico - FIRST #846
Putting it all together1. 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
August 10, 2013 David Giandomenico - FIRST #846
Winch Design SpecificationInput 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
August 10, 2013 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
August 10, 2013 David Giandomenico - FIRST #846
Determine the Gear Reduction
Required Gear Reduction 1021.0
Loss estimate assuming 'n' small gear sets
Individual gear set reduction ratio 4 times% Loss per gear set 5%
Number of gear reductions 4.998 setsTotal estimated gear efficiency 77.39%
August 10, 2013 David Giandomenico - FIRST #846
Gear Loss Estimate
Winch line output at speedMotor torque at speed (above) 0.0798 N-mTorque after gearbox (no loss) 81.47 N-m
After gear box losses 63.05 N-mForce on Line 827.41 NForce on Line (lb) 185.75 lb
Margin
Weight of load 130 lbMargin (force:load at target speed) 1.43 : 1
August 10, 2013 David Giandomenico - FIRST #846
Verify We Meet or ExceedPull Strength Specification
August 10, 2013 David Giandomenico - FIRST #846
Feat Accomplished!185 lb exceeds required spec of 130lbs
August 10, 2013 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
August 10, 2013 David Giandomenico - FIRST #846
Addendum: Interest or Time permitting