September 15, 2007 D.Giandomenico More than you wanted to know about Robot Winch Design David...
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September 15, 2007 D.Giandomenico
More than you wanted to know about
Robot Winch Design
David GiandomenicoLynbrook High School Robotics
FIRST Team #[email protected]
(408)343-1183
September 15, 2007 D.Giandomenico
A few common tasks robots might do:
• Robot may move itself
• Robot often has an arm to lift or grasp objects
• Robot might have to lift itself or pull an object
September 15, 2007 D.Giandomenico
Three functions we may consider:
• Design a robot arm• Design the drive train• Design a lifting winch
We will consider the winch, which is arguably the most simply specified of the three robotic functions.
September 15, 2007 D.Giandomenico
2004 FIRST National Robotics Competition
• Endgame Task: Robot must suspend itself from a bar located 10 feet above the floor
• Our task: Design a winch to lift robot
September 15, 2007 D.Giandomenico
Design Criterion for the Winch
• How much weight to lift?
• How far?
• How fast?
September 15, 2007 D.Giandomenico
What We Want.
• Weight:
• Distance:
• Time (speed):
130 lbs
1.5 feet
5 seconds
September 15, 2007 D.Giandomenico
What we have:(Some of the Motors supplied in FIRST Robotics Kit)
September 15, 2007 D.Giandomenico
All data approximate at 12 VOLTS
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Bosch, motor only - - 0.65 114 A 20,000 RPM 2.5 A 340 W
Bosch, motor/gearbox in high
20:1 80% 10 N-m 114 A 1,000 RPM 2.5 A 260 W
Bosch, motor/gearbox in low
64:1 70% 29 N-m 114 A 300 RPM 2.5 A 230 W
Fisher-Price, motor only - - .36 N-m 57 A 15,000 RPM ? 140 W
Fisher-Price, motor/gearbox
147:1 65% 35 N-m 57 A 100 RPM ? 91 W
Delphi Sliding Door Motor (Mfg: Taigene)
- - 35 N-m 40 A 75 RPM ? 69 W
Globe, motor only - - .21 N-m 21 A 11,500 RPM .82 A 63 W
Globe, motor/gearbox 117:1 77% 19 N-m 21 A 100 RPM .82 A 50 W
Delphi Seat Motor (Mfg: Keyang)
- - 2 N-m 20 A 600 RPM ? 31 W
Delphi Window Motor (Mfg: Valeo)
- - 12 N-m 20 A 70 RPM ? 22 W
data from www.usfirst.org
FIRST MOTOR COMPARISON (2002-2003)
All data approximate at 12 VOLTS
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Bosch, motor only - - 0.65 114 A 20,000 RPM 2.5 A 340 W
Bosch, motor/gearbox in high
20:1 80% 10 N-m 114 A 1,000 RPM 2.5 A 260 W
Bosch, motor/gearbox in low
64:1 70% 29 N-m 114 A 300 RPM 2.5 A 230 W
Fisher-Price, motor only - - .36 N-m 57 A 15,000 RPM ? 140 W
Fisher-Price, motor/gearbox
147:1 65% 35 N-m 57 A 100 RPM ? 91 W
Delphi Sliding Door Motor (Mfg: Taigene)
- - 35 N-m 40 A 75 RPM ? 69 W
Globe, motor only - - .21 N-m 21 A 11,500 RPM .82 A 63 W
Globe, motor/gearbox 117:1 77% 19 N-m 21 A 100 RPM .82 A 50 W
Delphi Seat Motor (Mfg: Keyang)
- - 2 N-m 20 A 600 RPM ? 31 W
Delphi Window Motor (Mfg: Valeo)
- - 12 N-m 20 A 70 RPM ? 22 W
data from www.usfirst.org
FIRST MOTOR COMPARISON (2002-2003)
September 15, 2007 D.Giandomenico
“CIM” Motor Specification
September 15, 2007 D.Giandomenico
“CIM” Motor Performance
September 15, 2007 D.Giandomenico
“CIM” Motor Performance
September 15, 2007 D.Giandomenico
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
September 15, 2007 D.Giandomenico
All data approximate at 12 VOLTS
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Bosch, motor only - - 0.65 114 A 20,000 RPM 2.5 A 340 W
Bosch, motor/gearbox in high
20:1 80% 10 N-m 114 A 1,000 RPM 2.5 A 260 W
Bosch, motor/gearbox in low
64:1 70% 29 N-m 114 A 300 RPM 2.5 A 230 W
Fisher-Price, motor only - - .36 N-m 57 A 15,000 RPM ? 140 W
Fisher-Price, motor/gearbox
147:1 65% 35 N-m 57 A 100 RPM ? 91 W
Delphi Sliding Door Motor (Mfg: Taigene)
- - 35 N-m 40 A 75 RPM ? 69 W
Globe, motor only - - .21 N-m 21 A 11,500 RPM .82 A 63 W
Globe, motor/gearbox 117:1 77% 19 N-m 21 A 100 RPM .82 A 50 W
Delphi Seat Motor (Mfg: Keyang)
- - 2 N-m 20 A 600 RPM ? 31 W
Delphi Window Motor (Mfg: Valeo)
- - 12 N-m 20 A 70 RPM ? 22 W
data from www.usfirst.org
FIRST MOTOR COMPARISON (2002-2003)
All data approximate at 12 VOLTS
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Sta
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Sta
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urr
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Bosch, motor only - - 0.65 114 A 20,000 RPM 2.5 A 340 W
Bosch, motor/gearbox in high
20:1 80% 10 N-m 114 A 1,000 RPM 2.5 A 260 W
Bosch, motor/gearbox in low
64:1 70% 29 N-m 114 A 300 RPM 2.5 A 230 W
Fisher-Price, motor only - - .36 N-m 57 A 15,000 RPM ? 140 W
Fisher-Price, motor/gearbox
147:1 65% 35 N-m 57 A 100 RPM ? 91 W
Delphi Sliding Door Motor (Mfg: Taigene)
- - 35 N-m 40 A 75 RPM ? 69 W
Globe, motor only - - .21 N-m 21 A 11,500 RPM .82 A 63 W
Globe, motor/gearbox 117:1 77% 19 N-m 21 A 100 RPM .82 A 50 W
Delphi Seat Motor (Mfg: Keyang)
- - 2 N-m 20 A 600 RPM ? 31 W
Delphi Window Motor (Mfg: Valeo)
- - 12 N-m 20 A 70 RPM ? 22 W
data from www.usfirst.org
FIRST MOTOR COMPARISON (2002-2003)
September 15, 2007 D.Giandomenico
Choosing a motor based onMaximum Motor Output Power
• The max power of a DC PM magnet motor cannot be sustained without burning out the motor!
• As a rule of thumb, operate motor at 70%-80% of theno-load speed.
• Power output = Pmax * 4(1-) where % no-load speed
• Coincidentally, At 75% no-load speed, Pout = 75% Pmax
• Need to consider losses in Gear sets
September 15, 2007 D.Giandomenico
All data approximate at 12 VOLTS
Ge
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Ge
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Sta
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Sta
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Fre
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urr
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Po
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Bosch, motor only - - 0.65 114 A 20,000 RPM 2.5 A 340 W
Bosch, motor/gearbox in high
20:1 80% 10 N-m 114 A 1,000 RPM 2.5 A 260 W
Bosch, motor/gearbox in low
64:1 70% 29 N-m 114 A 300 RPM 2.5 A 230 W
Fisher-Price, motor only - - .36 N-m 57 A 15,000 RPM ? 140 W
Fisher-Price, motor/gearbox
147:1 65% 35 N-m 57 A 100 RPM ? 91 W
Delphi Sliding Door Motor (Mfg: Taigene)
- - 35 N-m 40 A 75 RPM ? 69 W
Globe, motor only - - .21 N-m 21 A 11,500 RPM .82 A 63 W
Globe, motor/gearbox 117:1 77% 19 N-m 21 A 100 RPM .82 A 50 W
Delphi Seat Motor (Mfg: Keyang)
- - 2 N-m 20 A 600 RPM ? 31 W
Delphi Window Motor (Mfg: Valeo)
- - 12 N-m 20 A 70 RPM ? 22 W
data from www.usfirst.org
FIRST MOTOR COMPARISON (2002-2003)
All data approximate at 12 VOLTS
Ge
arb
ox
Ra
tio
Ge
arb
ox
Eff
icie
nc
y
Sta
llTo
rqu
e
Sta
llCu
rre
nt
Fre
eS
pe
ed
Fre
eC
urr
en
t
Pe
ak
Po
we
r
Bosch, motor only - - 0.65 114 A 20,000 RPM 2.5 A 340 W
Bosch, motor/gearbox in high
20:1 80% 10 N-m 114 A 1,000 RPM 2.5 A 260 W
Bosch, motor/gearbox in low
64:1 70% 29 N-m 114 A 300 RPM 2.5 A 230 W
Fisher-Price, motor only - - .36 N-m 57 A 15,000 RPM ? 140 W
Fisher-Price, motor/gearbox
147:1 65% 35 N-m 57 A 100 RPM ? 91 W
Delphi Sliding Door Motor (Mfg: Taigene)
- - 35 N-m 40 A 75 RPM ? 69 W
Globe, motor only - - .21 N-m 21 A 11,500 RPM .82 A 63 W
Globe, motor/gearbox 117:1 77% 19 N-m 21 A 100 RPM .82 A 50 W
Delphi Seat Motor (Mfg: Keyang)
- - 2 N-m 20 A 600 RPM ? 31 W
Delphi Window Motor (Mfg: Valeo)
- - 12 N-m 20 A 70 RPM ? 22 W
data from www.usfirst.org
FIRST MOTOR COMPARISON (2002-2003)
September 15, 2007 D.Giandomenico
Estimate gear loss for a large gear reduction
Consider a large gear reduction of 1200
First, estimate number of small gears sets(Typical gear sets might have a ratio of 3:1)
Second, estimate the loss in for n gear sets
September 15, 2007 D.Giandomenico
Gear loss estimate for a set of gears
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%
September 15, 2007 D.Giandomenico
Estimate of how many gears to make a large gear reduction.
• 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
In the final design, N must be an integer, but for the interim design, this method conveniently allows us to estimate the loss without committing to a specific gear selection.
September 15, 2007 D.Giandomenico
Gear loss estimate
From before, we need around n=6.45 gear sets. Assuming a loss of 4% for each gear set,
T = in
or
T = (1-4%)6.45 = 76.8%
September 15, 2007 D.Giandomenico
Fisher Price Motor Data 2004
All data approximate at
12 VOLTS
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Fisher-Price, motor only
- - .36 N-m 57 A 15,000 RPM 2 140 W
September 15, 2007 D.Giandomenico
Fisher Price Motor 2004
From FIRST_MOTOR_CALC.xls
SPEED
0.0
2000.0
4000.0
6000.0
8000.0
10000.0
12000.0
14000.0
16000.0
0.00
0.02
0.05
0.07
0.10
0.12
0.14
0.17
0.19
0.22
0.24
0.26
0.29
0.31
0.34
0.36
Torque (N-m)
Sp
ee
d (
RP
M)
V=12VDC
Speed decreases as motor is braked
September 15, 2007 D.Giandomenico
What is Torque?
dFW inline
dFT
But isn’t that “Work”
September 15, 2007 D.Giandomenico
Units of Work vs. Torque
• Work (Energy)
• Torquepound feet(lbf-ft), ft-lbf, oz-in, N-m etc.
ft-lbf, Joules (=N-m), KWh, etc.
September 15, 2007 D.Giandomenico
Power, Torque & Speed
TP
60
RPM 2TP
tdFP /
trFP /)( trFP /
September 15, 2007 D.Giandomenico
Fisher Price Motor 2004
From FIRST_MOTOR_CALC.xls
POWER
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
0.00
0.02
0.05
0.07
0.10
0.12
0.14
0.17
0.19
0.22
0.24
0.26
0.29
0.31
0.34
0.36
Torque (N-m)
Me
ch
an
ica
l Po
we
r (W
att
s)
V=12VDC
September 15, 2007 D.Giandomenico
Speed & Torque in a DC PM Motor
• Let ={0,100%}
such that
)1()(
)(
)(
s
s
s
TT
NN
September 15, 2007 D.Giandomenico
Fisher Price Motor 2004
From FIRST_MOTOR_CALC.xls
SPEED
0.0
2000.0
4000.0
6000.0
8000.0
10000.0
12000.0
14000.0
16000.0
0.00
0.02
0.05
0.07
0.10
0.12
0.14
0.17
0.19
0.22
0.24
0.26
0.29
0.31
0.34
0.36
Torque (N-m)
Sp
ee
d (
RP
M)
V=12VDC
September 15, 2007 D.Giandomenico
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
September 15, 2007 D.Giandomenico
Fisher Price Motor 2004
From FIRST_MOTOR_CALC.xls
POWER
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
0.00
0.02
0.05
0.07
0.10
0.12
0.14
0.17
0.19
0.22
0.24
0.26
0.29
0.31
0.34
0.36
Torque (N-m)
Me
ch
an
ica
l Po
we
r (W
att
s)
V=12VDC
September 15, 2007 D.Giandomenico
Max Power in a DC PM Motor
22ss
Max
TP
604
2 max
RPMs
Max
NTP
September 15, 2007 D.Giandomenico
Fisher Price Motor Data 2004
All data approximate at
12 VOLTS
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Fre
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Fre
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Fisher-Price, motor only
- - .36 N-m 57 A 15,000 RPM 2 140 W
September 15, 2007 D.Giandomenico
Fisher Price Motor 2004
From FIRST_MOTOR_CALC.xls
CURRENT
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
0.00
0.02
0.05
0.07
0.10
0.12
0.14
0.17
0.19
0.22
0.24
0.26
0.29
0.31
0.34
0.36
Torque (N-m)
Cu
rre
nt
(Am
ps
)
V=12VDC
September 15, 2007 D.Giandomenico
Power input into a DC PM Motor
Device Under Test (DUT) conditions:V = 12VDC (fixed)Load is varied using some type of brake
Under these conditions, a good model for the current is:
)1)(()( oso IIII
September 15, 2007 D.Giandomenico
Power input into a DC PM Motor
)]1)(([
)(
osoDCIN
DCIN
IIIVP
IVP
VIP
Power is small when =100%, and increases linearly as decreases
September 15, 2007 D.Giandomenico
Fisher Price Motor 2004
From FIRST_MOTOR_CALC.xls
CURRENT
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
0.00
0.02
0.05
0.07
0.10
0.12
0.14
0.17
0.19
0.22
0.24
0.26
0.29
0.31
0.34
0.36
Torque (N-m)
Cu
rre
nt
(Am
ps
)
V=12VDC
September 15, 2007 D.Giandomenico
Fisher Price Motor 2004
From FIRST_MOTOR_CALC.xls
POWER
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
0.00
0.02
0.05
0.07
0.10
0.12
0.14
0.17
0.19
0.22
0.24
0.26
0.29
0.31
0.34
0.36
Torque (N-m)
Me
ch
an
ica
l Po
we
r (W
att
s)
V=12VDC
September 15, 2007 D.Giandomenico
Fisher Price Motor 2004
From FIRST_MOTOR_CALC.xls
EFFICIENCY
0.0
10.0
20.0
30.0
40.0
50.0
60.0
0.00
0.02
0.05
0.07
0.10
0.12
0.14
0.17
0.19
0.22
0.24
0.26
0.29
0.31
0.34
0.36
Torque (N-m)
Eff
icie
nc
yV=12VDC
September 15, 2007 D.Giandomenico
DC PM Motor Summary
• Max Power occurs at 50% No-Load Speed
• Best efficiency typically occurs at about 75%-85% No-Load Speed
• Most DC PM Motors cannot sustain operating with full voltage applied at speeds less than 50% No-Load.
September 15, 2007 D.Giandomenico
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
September 15, 2007 D.Giandomenico
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
September 15, 2007 D.Giandomenico
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
September 15, 2007 D.Giandomenico
Determine the Gear ReductionDrum speed
Revolutions / second 0.191Revolutions / minute (rpm) 11.46
Motor spec at 12VDCNo load speed 15000 RPMStall Torque 0.36 N-mPout max 141.37 W
Motor speed and torque% motor speed 80%Motor Speed 12000Torque 0.0720 N-mRequired Gear Reduction 1047.2
September 15, 2007 D.Giandomenico
Gear Loss Estimate
Required Gear Reduction 1047.2
Loss estimate assuming 'n' small gear setsIndividual gear set reduction ratio 4 times% Loss per gear set 5%
Number of gear reductions 5.016Total estimated gear efficiency 77.31%
September 15, 2007 D.Giandomenico
Verify We Meet or Exceed Pull Strength Specification
Total estimated gear efficiency 77.31%
Winch line output at speedMotor torque at speed (above) 0.0720 N-mTorque after gearbox (no loss) 75.40 N-m
After gear box losses 58.29 N-mForce on Line 765.00 NForce on Line (lbs) 171.74 lbs
September 15, 2007 D.Giandomenico
Feat Accomplished!
• 171lb exceeds required spec of 130lbs
• What does this mean?• Things to think about:
– Could it be that we overdesigned the winch?
– How will the winch respond when lifting 130lbs if it is pulling with 171lbs?
– And of course, how do we build this winch?
September 15, 2007 D.Giandomenico
More than you wanted to know about
Robot Winch Design
David GiandomenicoLynbrook High School Robotics
FIRST Team #[email protected]
(408)343-1183