Chapter 6 Mechanical Actuation Systems
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Mechanical actuation system Mechanical actuation system Learning outcome At the end of the chapter, student should be able to: • Evaluate mechanical system involving: – linkages – cams – gears – ratchet and pawl – belt and chain drives
description
Mechatronics
Transcript of Chapter 6 Mechanical Actuation Systems
Mechanical actuation systemMechanical actuation system
Learning outcome
At the end of the chapter, student should be able to:• Evaluate mechanical system involving:
– linkages– cams– gears– ratchet and pawl– belt and chain drives
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• Provide function as:– Motion converters
• rotational to linear
– Force amplification • lever
– Change of speed• gears
– Transfer of rotation axis• timing belt
– Particular types of motion• quick return mechanism, cam
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Types of motion• Translational, rotational and its combination• Degree of freedom, dof
dof = 6 – number of constrain
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Types of motion• Translational, rotational and its combination• Degree of freedom, dof
– dof = 6 – number of constrain– For planar
dof = 3(N-1) – 2L where:
N = number of linkL = number of join
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Kinematic chains• A link is part of a mechanism• A joint is a connection between link• Kinematic chain is a sequence of
link and joints
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Kinematic chains– Open loop kinematic chain
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Kinematic chain– Slider crank mechanism
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Kinematic chain• The four bar chain• Grashof theorem• Lmax + Lmin La + Lb
• for one link to rotate
360 deg
Double crank
Double lever Lever crank
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Kinematic chainExample
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Cams• Rotates to provide reciprocating
motion to the follower
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• Cams
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• Cams
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Lower Wheel
Upper Wheel
Upper wheel axis of rotation
Lower wheel axis of rotation
Driving pin
• Mechanism is used for achieving intermittent motions. • The component has two wheels; upper & lower• Continuous rotational movement of the lower wheel • Intermittent motion of the upper wheel; rotates step-wise
Geneva wheel
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Gear trains• Used to change speed or torque of rotating device
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Gear trains• Used to change speed or torque of rotating device
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Gear trains• G = A / B = dB / dA= B / A
G = A / B x B / C = A / C
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Epycylic gear train• Consists of groups of gears• 3 possibility of gear ratios
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Ratchet and pawl• Used to lock a mechanism when its holding a load
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Belt and chain drives–Torque on A, A = (T1 - T2) rA
–Torque on B, B = (T1 - T2) rB
– Power = (T1 - T2)v
–where belt speed v = A rA
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Belt and chain drives• Reversing drive
