Actuators
&
Power Transmission Elements
.
Actuators
Introduction
• Actuators are the muscles of robots.
• links and the joints are the skeleton of the robot, the actuators act as muscles,
which move or rotate the links of the robots.
• The actuator must have enough power to accelerate and decelerate the links and
to carry the loads, be light, economical, accurate, responsive, reliable, and easy to
maintain.
Types of Actuators
1) Hydraulic Actuators (Uses pressurized oil)
1) Rotary type (Produce rotational motion)
2) Reciprocating type(Produce translational motion)
2) Pneumatic Actuators (Uses pressurized air)
1) Rotary type (Produce rotational motion)
2) Reciprocating type (Produce translational motion)
3) Electrical Actuators (Uses electric current).- Rotational motion alone
(Use mechanical transmission elements to get translational motion)
Types Hydraulic & Pneumatic Actuators
LINEAR ACTUATOR
PUMP
LOAD
PISTON & ROD
TO RESERVOIR
ROTARY ACTUATOR
PUMP
HYDRO MOTOR
Comparison
HYDRAULIC
ELECTRICAL
Speed
Speed
- High
Robot Size
- Large
PNEUMATIC
- Less
Robot Size
- Small
&Medium
Speed
- High
Robot Size
- Smaller
Floor occupancy - Large
Floor occupancy - Less
Floor occupancy - Very less
Accuracy
- High
Accuracy
- High
Accuracy
- Less
Maintenance
- Not Easy
Maintenance
- Easy
Maintenance
- Easy
Cost
- More
Cost
- Little less
Cost
- Cheaper
Preferred Envn. - Explosive
Preferred Envn. - Cleaner
Preferred Envn. - Designed
for less DoF
6
Power Transmission Elements
Gear drive
•
•
•
•
Spur Gears - Parallel
Helical Gears - Parallel
Bevel Gears - Perpendicular
Worm gears – Non parallel Non Intersecting
Gear drive
•
•
•
•
•
Less floor space
No possibility of slip
Easy to maintain
Difficult to construct
High cost
Belt drive
• Belt drive: Method of transferring rotary motion between two shafts.
• Construction: A belt drive includes one pulley on each shaft and one or more
continuous belts over the two pulleys.
• Principle: The motion of the driving pulley is, generally, transferred to the driven
pulley via the friction between the belt and the pulley.
• Belt: Looped strip of flexible material, used to mechanically link two or more
rotating shafts.
• Pulley: Wheel with a groove between two flanges around its circumference.
Pulleys are keyed to the shafts.
Belt Drives
• Inexpensive and Easy to design
• Maintenance is easy
• Elasticity present in the belts can provide damping and shock absorption which
results in less vibration
• Slip
• Huge in size
• Torque capacity is limited
Chain drives
• Chains are used for power transmission. The chain drives have some
features of both belt (flexibility of location of driver and driven) and gear
drives (ruggedness).
• A chain drive consists of an endless chain wrapped around sprocket
• The chain has a number of links connected by pins.
• The sprockets have teeth of special profile.
CHAIN AND SPROCKET
•
•
•
•
•
•
•
High Torque, Low Speed
Long as well as short center distance
More compact than belt or gear drives
Positive drive
Chain doesn’t require initial tension
Transmit more power than belt drives
Operate in any atmospheric conditions
•
•
•
•
•
•
Precise alignment of shaft required than belt drives
Not Suitable for non parallel shafts
High maintenance
Noisy Operation
Weight & Vibration
Complicated design
Thank You………