Mechatronics Unit I
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Transcript of Mechatronics Unit I
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MECHATRONICS
UNIT I
INTRODUCTION
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MECHATRONICS
Integration of microprocessor control systems,
electrical systems and mechanical systems.
It brings together the areas of technology
involving sensors & measurement systems, drive
& actuation systems, analysis of the behaviour
of the systems.
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Mechatronics involves systems , measurement
system and control system.
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CLOSED LOOP CONTROL SYSTEM
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Closed loop control
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Shaft speed control
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Actuation systems
Elements of control systems which areresponsible for transforming the output of amicroprocessor or control system into a
controlling action on a machine or device.
Types:
Hydraulic actuators
Pneumatic actuators
Mechanical actuators
Electrical actuators
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Hydraulic Actuator
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Accumulator
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Pneumatic Actuator
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Directional control valve
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Used to direct the flow of fluid
through the hydraulic / pneumatic
system.
It cannot vary the rate of flow
of fluid.
But they are completely open or
completely closed.
eg. Spool valve
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Directional control valve
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Pressure Limiting valve
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Mechanical Actuator
To transform linear motion into rotational motion.
Motion in one direction into a rotation in otherdirection at right angle.
Linkages
Cams
Gears
Rack and pinion Chain drive
Belt drives
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Kinematic Chains
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Each part of a mechanism which has
motion relative to some other part is
termed a LINK.
Joint is a connection between two or more links
at their nodes.
Eg. Lever, crank, connecting rod etc.
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BEARINGS
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Bearing is used to guide
with minimum friction
and maximum accuracy.
Plain Journal Bearing
Used to support rotating
shafts which are located ina radial direction.
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Elements of ball bearing
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Inner race & outer race .
The rolling element of either balls or rollers
A cage to keep the rolling element apart.
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Types of Ball Bearings
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Types of Ball Bearings
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Types of Ball Bearings
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Hydrodynamic journal bearing
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Oil
It consists of the shaft rotating
continuously.
In oil in such a way that it rides on oiland is not supported y metal.
Load is carried by the pressure generated
in the oil as a result of the rotating.
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Transfer Function
Laplace transform of outputTransfer Function = Laplace transform of input
Laplace transform Transform differentialEqn.
into an AlgebraicEqn.
Blockdiagram
G(s) =
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G(s)X (s)Y (s) X (s)
Y (s)
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Control Modes
A control unit can react to an error signal andsupply an output for correcting elements:
Two-step mode : on/off signal
Proportional mode (P)
Derivative mode (D)
Integral mode (I)
Combinations of mode (PD), (PI), (PID)
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1. Two-step mode : on/off signal
Two step mode :
Control action is discontinuous.
eg: If the room temperature is above the required
temp. then the switch is in off position and the
heater is off.
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2. Proportional control (P)
Size of the controller output is proportional to the
size of the error.
i.e. correction element of the control system will
receive a signal which is proportional to the size of
the correction required.
+ E(s) X(s) -
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Kp G(s)
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3. Derivative control (D)
The change in controller output from the set pointvalue is proportional to the rate of change with timeof the error signal.
Iout Io = Kp de
dt
Where Io -- set point output valueIout output value that will occur when the error e
changes with time.
Kp constant of proportionality
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4. Integral controller (I)
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4. Integral mode (I)
.
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It consists of an operational amplifier
connected as an INTEGRATOR and followed
by another operational amplifier
connected to a SUMMERto add the integrator
output to that of the controller output.
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5. Proportional plus Integral control (PI)
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Error gives rise to a proportional controller output
which remains constant since the error does not change.
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7. PID controller (PID)
Combining all three modes of control
[Proportional, Derivative & Integral]
enables a controller to be produced whichhas no offset error.
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