Mechatronics and Microprocessor- MEE561

Module- 1
Introduction to Mechatronic Systems: definitions, multi-disciplinary scenario, origin of
Mechatronics, engineering system, Mechatronic system, Measurement and its elements,
control systems open loop and closed loop control system, Their elements and functions,
Microprocessor based controllers- Program logic controllers (PLC). Review of sensors and
transducers, classification of sensors and transducers, light sensors, proximity sensors, Hall
Effect sensors.

Introduction to Mechatronic Systems:

Mechatronics definition

Mechatronics is “the synergistic (Together) combination of mechanical engineering,

electronic engineering, control engineering and systems thinking in the design of
products and manufacturing processes”
Examples: Robotic manipulators, aircraft simulators, electronic traction control systems,
adaptive suspensions, landing gears, air conditioners under fuzzy logic control, automated
diagnostic systems, micro electromechanical systems (MEMS), consumer products such as
VCRs, automatic washing machine, digital fuel injection system, engine management
system and driver-less vehicles

Multidisciplinary scenario
 The field of Mechatronics deals with the synergetic integration of mechanical
engineering, electronic engineering and control engineering in the development of
electromechanical products through an integrated design approach. Therefore, a
Mechatronic system requires a multidisciplinary approach for the design,
development and implementation of products
 A typical Mechatronics system consists of mechanical systems, electrical systems
and information technology. The domain of Mechatronics is as shown in figure
below and the next generation products will be integrated with these environments

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 Mechatronics and Microprocessor- MEE561

Fig: Domain of Mechatronics

 The concept of Mechatronics is to bring together the area of technology involving
sensors and measurement systems, drive and actuations systems, microprocessor
and control systems as shown in fig. below which depicts the various engineering
disciplines involved in Mechatronics system

Fig: Constituents of Mechatronics

 Servo motor and humanoid robot is an typical example of multidisciplinary
products it consists of mechanical elements, actuators, sensors, controllers, signal
conditioning devices, computer and software, interfacing and power devices
 Other examples of Mechatronic systems include Automobile electronic fuel injection
(EFI), Automatic teller machines (ATMs), microwave ovens, room air-conditioning
system, calculators, photocopier, sewing machines and even toys. The level of the
technology incorporated into these kinds of devices continues to increase

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 Mechatronics and Microprocessor- MEE561

Origin of Mechatronics
 Rapid advances in electromechanical devices were evident in 1950s, particularly use of
servomotors and automation/machine control systems
 Since 1960s have resulted in more rapid development in digital computer and
communication, Integrated circuit (IC) and microprocessor technology
 In 1969, Japan engineer Yaskawa coined the term “Mechatronics” and won the
rights to the term in 1973
 During 1970s, Mechatronics focused on servo technology which led to invention of
automatic door openers and auto-focus cameras
 The research in 1970s and 1980s paved way for evolution of Mechatronics with
development of automated transit systems and robots which spread through
Europe to other parts of world
 In 1980s, there was a veritable explosion in microprocessor-based products.
Microprocessors were embedded into mechanical systems to improve performance
such as anti-lock braking and electric seats
 In 1990s, Mechatronics centered on communication technology to connect products
into large networks, including production of air bags and other related technologies

Mechatronics today:
 As need of Mechatronics continues to expand. Two things that have contributed to
its growth are shrinking global market and need for reliable and cost effective
products
 Mechatronics assists rapid reaction to change, competitive product properties and
shortened product cycles- absolute necessities for any company
 Mechatronics melds new technologies to existing technologies and combines to
solve problems, create products and creates new ways of doing things
 For example, intelligent control and artificial neural network and fuzzy logic system
are extensively used
 Today we witness use of Mechatronics to products such as aircraft, automobiles,
manufacturing machines, office automation devices, etc.
 Bio-robotics is the new trend for applications in environmental control
 Micro-electromechanical systems with embedded sensors and nano-devices are fast
emerging in Mechatronics application in today’s world

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 Mechatronics and Microprocessor- MEE561

Future of Mechatronics:
 With rapidly changing time, the technology will have to improve
 In future, Mechatronics will increasingly focus on safety, reliability and affordability
 Mechatronics will also play a large role in the use of robotics to assist with
efficiency, productivity, accountability and control
 It is also projected to play a major role in the medical field, as well as in
computerized world and manufacturing and process industries

Evolution of Mechatronics
Mechatronics technology has evolved through several stages that are primarily defined in
terms of
 Primary level Mechatronics
In early days Mechatronics products were at the primary level. This level
encompasses input/output (I/O) devices such as sensors and actuators that
integrate electrical signaling with mechanical action at the basic control level.
Electrically controlled fluid valves and relay switches are two examples.
 Secondary level Mechatronics
Secondary level Mechatronics integrates microelectronics into electrically
controlled devices. Sometimes these products are stand-alone. An example is a
cassette tape player.
 Tertiary level Mechatronics
The Mechatronic systems at this level are called smart systems. The control strategy
uses microelectronics, microprocessors, and other application-specific integrated
circuits (ASIC) as bits and pieces for control realization. A microprocessor-based
electrical motor used for actuation purposes in typical industrial robots can be
considered as an example of tertiary level Mechatronic system.
 Quaternary level Mechatronics
This level attempts to improve smartness a step ahead by introducing intelligence
and FDI (Fault Detection and Isolation) capability into the systems. Example:
humanoid robot

Elements/Components of Mechatronic system

 The key elements of Mechatronic system can be classified under the following
categories:
 Information systems
 Mechanical systems
 electrical systems
 computer systems

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 Mechatronics and Microprocessor- MEE561

 sensor and actuators

 real-time interfacing
 Fig. below shows the key elements in a typical Mechatronic system

 From the above fig. the actuators and sensors form a mechanical system. The
actuators produce motion or cause some action where as the sensors detect the
state of the system parameters, inputs and outputs. The input signal conditioning
and interfacing systems provide connections between the control circuits and the
I/O devices. The overall control of the system is carried out by digital controls. The
graphical display of devices provides visual feedback to the users

Conventional design approach vs. Mechatronic design approach

Fig. below shows the design methodology integrating mechanical and electrical systems
(Mechatronic system design) in relation to conventional methods
Feature Traditional or Mechatronic design
Convention design
Design

Size Bulky Compact

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 Mechatronics and Microprocessor- MEE561

Movement Non- adjustable Programmable

Mechanisms Complex Simple
Drive Constant speed Variable speed
Synchronizat Mechanical Electronic
ion
Structure Rigid and heavy Lighter
Accuracy Determined by tolerance of Achieved by feed back
Mechanism
Control Manual Automatic/programmable

Objectives of Mechatronics
Mechatronics mainly focuses on:
 dependability and safety
 reliable integration
 affordability
 higher level control
 control of non-linear devices
 cost effective
 Serviceability, maintainability and upgradeability

Merits or Advantages of Mechatronics systems

 High level of integration
 Increased functionality and better design
 More use of electronics and software instead of mechanical function
 assumes responsibility for process and operation with little interference of
operators
 uses AI and intelligent process control
 Multisensory and programs environment
 high reliability, safety, improved and less expensive control

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 Mechatronics and Microprocessor- MEE561

Demerits or disadvantages or limitations of Mechatronics systems

 Initial cost is very high
 Complicated design and system
 Repair and maintenance is complex
 Replacement is difficult, to change old system to new system

Applications of Mechatronics systems

 Domestic applications: Fridges and freezers, microwave ovens, vacuum cleaners,
cookers, timers, mixers etc
 Domestic systems: AC units, security systems, automatic gate control systems
 Office equipments: laser printers, hard drive positioning systems, scanners,
photocopier, fax machines tape drives etc
 Retail equipments: Automatic labeling systems, bar coding machines etc
 Banking: cash registers, ATMs
 Manufacturing equipments: NC tools, AGVs, Robots
 Aviation system: flight control actuators, landing gear system

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 Mechatronics and Microprocessor- MEE561
Measurement and control systems- their elements and functions

Definition of System
 A system is a group of physical components combined to perform a specific function.
A system can be considered as a box that has an input and an output.
 Example: An electric generator (Fig. below) is a system which has mechanical
rotation as its input and electric power as its output.

MEASUREMENT SYSTEM

Definition:
 A measurement system can be considered as a system that is used to measure the
required parameter. The quantity being measured is given as input and the value of
that quantity is obtained as output.
 Example: A rotational speed measurement system- digital tachometer (Fig. below),
has the rotation of shaft as input and gives an output of a number on the LED
display.

Elements of generalized Measurement system

Generally a measurement system consists of 3 basic elements illustrated in Figure below.
1. Sensor/transducer.
2. Signal conditioner.
3. Display/read out devices.
In addition to the above, electrical power is also required.

The transducer senses the physical phenomenon to be measured and transform it from one form to
another form (generally electrical form). The output of this unit is input to the signal conditioner
which is next element.

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 Mechatronics and Microprocessor- MEE561

 The signal processor/conditioner performs senses the output signals of sensor and
converts it into suitable, measurable level of signals. The term sensor is often used to
refer to the transducer or to the combination of transducer and signal processor
. The following functions of signal conditioners are:
o Amplification of signals: the level of signals from the transducer may be of
low level for the next use and hence need to be amplified (increased).
o Attenuation: similarly the level of signals from the transducer may be of
higher level for the next use and hence need be attenuated (decreased).
o Filtering: signals from the transducer may contain some other undesirable
signals which need to be filtered or eliminated before it is used. Otherwise a
corrupt output will be generated.
o Analog to digital conversion (ADC): the signals from the transducer may be
analog in nature and if these signals were to be used as input to electronic
system/computer system, they need to be converting to digital form.
Similarly sometimes we use DAC.

 Finally, the recorder/display/read out is an instrument, a computer, a hard-copy

device, or simply a display that maintains the sensor data for online monitoring or
subsequent processing
Example: Measurement System—Digital Thermometer
The following figure shows an example of a measurement system. The thermocouple is a
transducer that converts temperature to a small voltage; the amplifier is a signal
processor/conditioner increases the magnitude of the voltage; the A/D (analog-to-digital)
converter is a device that changes the analog signal to a coded digital signal; and the LEDs
(light emitting diodes) display the value of the temperature.

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 Mechatronics and Microprocessor- MEE561

CONTROL SYSTEM

Definition:
A control system is a Device/system that is used to control the output of the system to a
desired value.
Example: A domestic AC system has the temperature required to the house as input and the
room temperature as its output.

Function of Control system:

 To minimize the error between the actual and the desired output
 To minimize the time response to load changes in the system

Requirements of Control system

 Stability: For any change in input signal, the output of the system reads or makes its
response at a reasonable value
 Accuracy: The closeness of the measured value to the true value is known as
accuracy. In practice, the measured value differs from the true value
 Response: The quickness with which an instrument responds to a change in the
output signal is known as response

Types of Control system

 Open loop or non-feedback control systems
 Closed loop or feedback control systems

Open loop control systems:

Fig. below shows the block diagram of open loop control system. A system in which
controlling action of input is independent of change in output is called open loop system.
There is no feedback signal to verify accuracy/error between input signal and the output.

Example 1: According to the input signal, the stepping motor rotates to actuate slides. At
the same time, when the gears rotate, the lead screw is turned. Thus, the slide moves. Due
to the absence of feedback signal, the required distance moved by the slide is not correctly
known.

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Controller is the drive adjustment of a stepping motor. The gears and lead screw act as
plant or process.

Example 2: Electric fire system (Room heating)

Controller is the switch. Electric power actuating fire is the plant or process

Advantages- Open loop system

 It is more suitable where accurate positioning of the tools is not required
 It is very simple
 It has better reliability and stability
 It is less costly

Disadvantages- Open loop system

 It is not suitable for rough work
 The error cannot be corrected
 The control action depends upon input command
 The presence of non- linearity can result in malfunctioning

Closed loop control systems:

Fig. below shows the block diagram/elements of closed loop control system. A system in
which controlling action of input is dependent of change in output is called closed loop
system. There is a feedback signal to compensate the error in output with respect to input
signal.

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The basic elements of a closed loop control system are:

1. Comparison element.
2. Control unit.
3. Correction unit.
4. Process unit.
5. Feedback unit/measuring device.
1. Comparison element: this unit compares the reference value with feedback value
and produces an error signal.
Error = reference value – feedback value
2. Control unit: Control unit analyses the error signal and decides what action is to be
taken.
3. Correction unit: the modified signal from the control unit will be received by the
correction unit which produces a change in the process to correct or change the
controlled condition.
4. Process unit: process unit is which variable is being controlled
5. Feedback unit/Measuring device: Produces a signal related to the variable being
controlled and is a feedback of output variable so that it can be compared with the
required value

Example 1: Room heating

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 It involve a thermostatic element which is sensitive to temperature and switches ON

when the temperature falls below the set value and OFF when it reaches it
 This temperature sensitive switch is then used to switch ON the heater
 The thermostatic element has the combined functions of comparing the required
temperature value and controlling operation of switch

Example 2: Water level controller of over head tank

Mechanical means of controlling water level

 Figure shows an example of a simple control system used to maintain a constant

water level in the tank
 The reference value is the initial setting of the lever arm arrangement

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 Mechatronics and Microprocessor- MEE561

 When the water is drawn from the tank the float moves downwards with the water
level. This causes lever arrangement to rotate and allows water to enter the tank
 This flows continues until the ball has risen to initial set level

Electronic means of controlling water level

 The overhead tank has a fixed contactor(sensor) fixed at the desired level inside
tank
 When the level of water in the tank falls, the float moves down and make contact
with fixed contactor (sensor) in turn it gives signal to pump to switch ON
 When the level of water rises the float moves up and breaks the contact and pump is
switch OFF. Thereby the required level of water is maintained in overhead tank

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 Mechatronics and Microprocessor- MEE561

Example 3: Hand reaching an object.

Example 5: Speed control of an Automobile

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 Mechatronics and Microprocessor- MEE561

Advantages- Closed loop system

 The feedback signal controls the table position accurately
 The system is used almost in all automation processes
 Change in the system is automatically taken care of
 Control action basically depends upon feedback

Disadvantages- Closed loop system

 System is complicated and expensive
 System may become unstable

Difference between open loop system and closed loop system

SL No Open loop control system Closed loop control system
1 Without feedback unit With feedback unit
2 Output is dependent on input Input is dependent on output
3 less accurate More accurate
4 Less expensive and easy to build Expensive and complex to build
5 slow in response to change in demand High in response to change in demand
6 stability can be ensured May be an unstable at times
7 Input factor is the sole factor for Control action is provided by the
providing the control action difference between the input command
and corresponding output
8 Control adjustment is depends upon the Control adjustment is depends upon
human adjustment and estimation output and feedback element
9 Any change in system component cannot Any change in system component can
be taken care automatically be taken care automatically
10 Example: ON/OFF of electric lamp, Example Automatic washing Machine,
Controlling of fan speed etc. digital camera, robots etc.

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 Mechatronics and Microprocessor- MEE561

Microprocessor based controllers

Programmable Logic Controller (PLC)
 Microprocessor based controller is a PLC- Programmable logic controller
 It is digital electronic device that uses a programmable memory to store instructions
and to implement functions such as logic, sequencing, timing, counting and
arithmetic in order to control machines and processes and has been specifically
designed to make programming easy.
 The term logic is used because the programming is primarily concerned with
implementing logic and switching operations.
 Input devices such as switch and output devices such as motors are being controlled
are connected to PLC and then the controller monitors the inputs and outputs
according to the program stored in the PLC by the operator and so control the
machine or process.

Examples of Microprocessor based controller or PLC

ENGINE MANAGEMENT SYSTEM. Fig.below shows the engine management system.

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 Mechatronics and Microprocessor- MEE561

 For ignition timing, the crankshaft drives a distributor which makes electrical
contact for each spark plug in turn and a timing wheel
 This timing wheels generates pulses to indicate the crankshaft position
 The microprocessor then adjusts the timing at which high voltage pulses are sent to
the distributor so they occur at the ‘right’ moments of time
 To control the A-F mixture entering a cylinder during the intake strokes, the
microprocessor varies the time for which a solenoid is activated to open the intake
valve on the basis of inputs received of the engine temperature and the throttle
position
 The amount of fuel to be injected into air stream can be determined by an input
from a sensor of the mass rate of air flow, or computed from other measurements
 the microprocessor then gives an output to control a fuel injection valve

SEQUENTIAL CONTROL
A system operating with sequential control is one where a number of prescribed
operations are performed in sequence. These systems are event based, where the next
action cannot be performed until the previous action is completed.

An example of event based sequential control system is a domestic washing machine. In

this system a number of operations or events have to carry out in correct sequence. The
various events of washing machine are as shown in figure 1 below. The block diagram of
washing machine is as shown in figure 2.

Figure 1: Various events of washing machine

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 Figure 2: Washing machine system

Sequences of operations are:

 During Pre-wash operation, the inlet valve is opened when machine is switched
ON and the valve is closed when the drum is filled with required level of water.
Water level is indicated by the water-level indicator sensor and gives feedback to
control unit. After completion of this operation, the micro-controller or control unit
operates the motor to rotate the drum. The outlet valve is opened and pump is
operated to drain water from drum after completing pre-wash cycle.
 The main wash cycle is then started by control unit by operating the inlet valve to
allow water to the drum. The water level indicator sensor indicates the water level
in the drum after reaching its required level. Now control unit switches ON the
heating-coil in the drum to heat the water. The temperature sensor gives feedback
to control unit after the water reaches its pre-set value. Then the control unit
operates the motor to rotate the drum. The motor rotates the drum to a pre-set
rotation and control unit switch OFF the motor. The control unit operates the pump
to drain water from the drum.
 The rinse cycle is started now; the operation is same as explained above. This cycle
is repeated two to three times
 The spinning cycle follows the rinse cycle. In this cycle, the control unit only
switches ON the motor, which rotates the drum at a higher speed than the other
cycles to drain the water from the clothes.

Mechanical Engineering Dept., NHCE, Bengaluru