1. D E S I G N
D
E
A
S
I
N
G
N
D
A
A
N
P
D
P
A
L
P
I
P
C
L
A
I
C
T
A
I
T
O
I
O
N
N
S
SOFFINID
N
U
D
S
U
T
R
S
I
T
A
R
LR
IA
O
L
B
O
R
T
O
SB OT S
S A B A R
S
I
A
G
B
I
A
R
R
I
I
V
G
A
I
R
S
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V
A
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S
A
.
RN.R
I S B N 9
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7
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B
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8
9
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0
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8
1
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9
6
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8
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6
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8
8
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0
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8
4. POWER TRANSMISSION
SYSTEMS
2. 2
Power Transmission Systems
1. Power transmission systems are used to
transmit motion from the prime mover to
the end equipment.
2. They are also used for motion conversion
like rotary to linear and vice versa.
3. Power transmission systems widely used in
robotics are
a) Gears
b) Belts
c) Chains
d) Shafts
3. 3
Gears
1. Gears are devices that have teeth cut on them
at regular intervals for transmitting motion
without slipping.
2. Gears are used for transmitting motion when
distance between two shafts are small.
3. Gears have higher transmission efficiency
and higher load carrying capacity.
4. Cast iron and high strength alloy steels are
used for making gears. Nylon is also used.
4. 4
Classification of Gears
1. Based on arrangement of teeth for engaging
with another gear
a) External gears
b) Internal gears
2. Based on teeth design
a) Spur gears
b) Helical gears
c) Bevel gears
d) Worm gears
e) Racks
13. 13
Belts
1. Belts are used when distance between two
shafts are very large.
2. Belts run over friction pulleys mounted on
ends of both the shafts.
3. Rubber belts woven with nylon fibres are
most widely used.
4. Woven nylon fibres provide adequate
mechanical strength to the belt.
20. 20
Chains
1. Chains are metal structures made up of
many links joined serially to form a closed
loop.
2. They are used for transmitting higher load
over long distances without slipping.
3. Sprockets are fitted on both the shafts for
engaging the chain.
4. Bush roller chain is widely used.
23. 23
Shafts
1. Transmission shafts are used to transmit
motion from one end to the other.
2. Solid and hollow cylindrical shafts are
widely used.
3. Transmission shafts should have high
strength and high wear resistance.
4. They should be capable of resisting the twist
to transmit higher torque.
5. Couplings and Bearings are used to connect
and support the shafts.
24. 24
Couplings
1. Couplings are used to connect two different
shafts.
2. Couplings are used to connect prime mover
to the actuator and other intermediate
transmission systems.
3. A coupling should transmit power without
loss.
4. They should be easily assembled and
disassembled.
25. 25
Types of couplings
Couplings are of two types
1. Rigid coupling
a) Flange coupling
b) Split muff coupling
c) Sleeve coupling
2. Flexible coupling
a) Universal joint coupling
b) Oldham coupling
34. 34
Bearings
1. Bearings are used to provide frictionless
free movement to the joints in the robot.
2. Bearings are also used to support the
transmission shafts.
3. They helps to reduce wear between moving
parts.
35. 35
Classification of Bearings
1. Based on direction of loading
a) Radial bearings
b) Thrust bearings
2. Based on contact condition
a) Sliding contact bearings
• Journal bearing
a) Rolling contact bearings
• Ball bearings
• Roller bearings
37. 37
Ball Bearings
1. Ball bearings have hardened steel balls in
between the stationary and moving members.
2. Balls are held in place by a ball cage.
3. Types of Ball bearings
a) Single row radial ball bearing
b) Double row radial ball bearing
c) Single direction thrust bearing
d) Double direction thrust bearing
e) Double direction angular contact thrust bearing
40. 40
Roller Bearings
1. Roller bearings have hardened steel rollers in
between the stationary and moving members.
2. Rollers are held in place by a cage.
3. Types of Roller bearings
a) Cylindrical roller bearing
b) Needle roller bearing
c) Tapered roller bearing
d) Spherical roller bearing
e) Double row spherical roller bearing
42. 42
Motion Conversion
1. Motion conversion is the process of
transforming the motion from the primer
mover to the required form to actuate the
final end equipment.
2. Types of conversion
a) Rotary to rotary motion conversion
b) Rotary to linear motion conversion
c) Linear to rotary motion conversion
43. 43
Rotary to Rotary Motion Conversion
1. Input rotary motion is converted to output
rotary motion but with different speed and
torque levels.
2. Widely used conversion systems
a) Gear trains
b) Harmonic drives
44. 44
Gear
Trains
1. Gear train is a series of gears connected so
that each gear turns proportionally when
driven by a prime mover.
2. Output speed and torque can be increased
or decreased using gear trains.
3. Step up gear train increases output speed
and reduces torque.
4. Reduction gear train reduces output speed
and increases torque.
45. 45
Types of Gear
Trains
Widely used types of gear trains are
1. Simple gear train
2. Compound gear train
3. Planetary gear train
51. 51
SimSpimlepGleeaGreTarrain
Number of teeth on pinion
Number of teeth
Ton
rg
aea
ir
n = 21
= 11
Gear as Driving Wheel
Gear Ratio = / = 21 / 11 = 1.909
So, 1 gear revolution = 1.909 pinion revolutions
Pinion as Driving Wheel
Gear Ratio = / = 11 / 21 = 0.524
So, 1 pinion revolution = 0.524 gear revolution
62. 62
Backlash in Gears
1. Backlash is the total distance of excessive play
produced at the meshing point between the
teeth of two meshing gears.
2. Backlash reduces positioning accuracy.
3. Backlash is eliminated by using anti backlash
gears.
4. Anti backlash gears has two gears loaded by
a spring in such a way that the teeth and slot
alignment of both gears are displaced.
67. 67
Harmonic Drives
1. Harmonic drives use elastodynamic properties
of metals for its operation.
2. It consists of three main parts namely circular
spline, flexspline and wave generator.
3. They offer very high reduction ratios and have
good positioning accuracy.
4. They have extremely low backlash as the
flexspline compensates the backlash
automatically.
70. 70
Rotary to Linear Motion Conversion
1. Input rotary motion is converted into
output linear motion.
2. They are used with rotary prime movers to
operate linear joints.
3. Widely used conversion systems
a) Lead screw mechanism
b) Rack and pinion mechanism
c) Belts and chain mechanism
d) Slider crank mechanism
e) Cam and follower mechanism
71. Lead Screw Mechanism
1. It has a long screw supported by bearings on
either ends, engaged with a suitable nut.
2. The nut has suitable provisions for mounting
the carriage and it is guided by guide shafts
while moving.
3. When the screw is rotated the nut moves
back or forth based on the direction of
rotation.
4. Acme and square thread types are usually
employed in lead screws.
5. Recirculating ball screws offer higher
transmission efficiency. 71
77. 77
Rack and Pinion Mechanism
1. The pinion is mated to a suitable rack fixed
to the system.
2. The pinion is connected to the motor and
the rack provides the linear motion as
output.
3. It is a two way motion conversion system.
It can also be used to convert linear to
rotary motion.
80. 80
Belts and Chain Mechanism
1. Belt mechanism has two pulleys over which the
belt rides.
2. The two ends of the belt is attached to a
carriage fixed suitably in a guide way.
3. When one of the pulley is rotated the carriage
translates back or forth according to the
direction of rotation.
4. To transmit higher load chain is used. Instead
of pulleys sprockets are used for engaging the
chain.
5. The two ends of the chain are connected to the
carriage.
87. 87
Cam and Follower Mechanism
1. Cam is a specialized structure that has a profile
corresponding to the path that the follower
should take.
2. When the cam is moved the follower moves
according to the cam profile.
3. Types of Cam and follower mechanism
a) Radial cam
b) Linear cam
c) Closed track radial cam
d) Closed track linear cam
e) Drum type cam
