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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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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