Prepared by Mr. S Riyaz Ahammed & Mr. HusheinAssistant Professor, Mechanical DepartmentVelTech Dr.RR & Dr.SR Technical University

MECHATRONICS U5MEA22

Unit 1

Mechatronics:-

Mechatronics basically refers to mechanical electrical systems and is centered on mechanics, electronics, computing and control which, combined, make possible the generation of simpler, more economical, reliable and versatile systems.

•The term "mechatronics" was first assigned by Mr.Tetsuro Mori, a senior engineer of the Japanese company Yaskawa, in 1969.

• Mechatronics is the combination of mechanical, electronic, computer,control engineering's and system engineering to design and manufacture useful products.

Key Elements

Measurement system

Control SystemsControl Systems are mainly of Two Types • Open Loop Control Systems • Closed Loop control Systems

•An open-loop controller, also called a non-feedback controller.• Basic difference between two types of systems is closed loop systems have feed back which makes them to be good precise control systems or automated systems.•PID controller, a commonly used closed-loop controller

Water Level Controller

• Controlled variable- water level in tank• Reference value- initial setting of float, lever

position• Comparison element- Lever• Error signal- Difference between the actual

and initial settings of lever position

• Control unit- Pivoted lever• Correction unit- Flap opening or closing water

supply• Process- water level in the tank

Shaft speed control systems

Description

• Potentiometer is used to set the voltage to be supplied to the power amplifier.

• Differential amplifier is used to amplify and compare the feed back value and reference value.

• Amplified error signal is fed to the motor to adjust the speed of rotating shaft.

• Tachometer is used to measure the speed of rotating shaft and speed is fed to amplifier.

Washing Machine control

• Example of an event based sequential control system is washing machine. Each event of washing machine may consist of number of sub events or steps. For example pre wash cycle, rinse cycle, main cycle, spinning cycle.

• Following figures represent the various events of washing machine system.

•During Pre wash cycle operation, the inlet valve is opened when the machine is switched ON and the valve is closed when the required level of water is filled in the drum.Main wash cycle is then started by micro processor by operating the inlet valve to allow the water in to the drum.Water level sensor senses the water level in the drum and it closes the inlet valve after reaching certain level, Micro processor switches ON the heating coil in the drum.

AUTOMATIC CAMERA

• Basic elements of control systems used in automatic camera are body, lenses and flash.

• Depending up on mode selected, the required combination of aperture and shutter speed and focus are automatically taken care by the camera.

• A typical camera system comprises drives and sensors, interfaces for lenses, flash and the user.

• Micro processor systems for lenses, user and flash are incorporated for controlling various operations. Micro processor takes input from range sensor and sends output to lens.

• Position is fed back to micro processor and it modifies the same.

• Light sensor gives input to micro processor, When photographer selects shutter controller, shutter opens up for photograph to be taken.

Engine Management System

• System consists of sensors for supplying, after suitable signal conditioning, the input signals to micro controller, and its providing output signals via drivers to actuate actuators.

• Engine speed sensor is an inductive sensor and consists of a coil for which inductance changes as the teeth of the sensor wheel pass it and so gives oscillating output.

• Temperature sensor is usually a thermistor.• Mass air flow sensor may be a hot wire

sensor, as air passes over heated wire it will be cooled, the amount of cooling will depend on the mass rate of flow.

• Oxygen sensor is generally closed end tube made of zirconium oxide with porous platinum electrodes on inner and outer surfaces.

• Following figure represents an engine management system

Unit 2

MICROPROCESOR IN

MECHATRONICS

MICROPROCESSOR

• A microprocessor incorporates the functions of a computer's central processing unit (CPU) on a single integrated circuit (IC),or at most a few integrated circuits. Microprocessor is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and provides results as output

8085 ARCHITECTURE

INPUT AND OUTPUT PERIPHERAL CIRCUITS

• A peripheral is a device that is connected to a host computer, but not part of it. It expands the host's capabilities but does not form part of the core computer architecture. It is often, but not always, partially or completely dependent on the host.

• There are three different types of peripherals:• Input, used to interact with, or send data to the

computer (mouse, keyboards, etc.)• Output, which provides output to the user from the

computer (monitors, printers, etc.)• Storage, which stores data processed by the computer

(hard drives, flash drives, etc.)

COMMUNICATIONS-INPUT,OUTPUT AND MEMORY WITH TIMING

DIAGRAM• Input/output (I/O) scheduling is the method

that computer operating systems use to decide which order block I/O operations will be submitted to storage volumes. I/O Scheduling is sometimes called 'disk scheduling'.

PURPOSE

• I/O schedulers can have many purposes depending on the goal of the I/O scheduler. Some common ones are:

• To minimize time wasted by hard disk seeks• To prioritize a certain processes' I/O requests• To give a share of the disk bandwidth to each running

process• To guarantee that certain requests will be issued

before a particular deadline

A/D CONVERTER

• An analog-to-digital converter (abbreviated ADC, A/D or A to D) is a device that converts a continuous physical quantity (usually voltage) to a digital number that represents the quantity's amplitude.

• The conversion involves quantization of the input, so it necessarily introduces a small amount of error. Instead of doing a single conversion, an ADC often performs the conversions ("samples" the input) periodically. The result is a sequence of digital values that have converted a continuous-time and continuous-amplitude analog signal to a discrete-time and discrete-amplitude digital signal.

• An ADC may also provide an isolated measurement such as an electronic device that converts an input analog voltage or current to a digital number proportional to the magnitude of the voltage or current. However, some non-electronic or only partially electronic devices, such as rotary encoders, can also be considered ADCs. The digital output may use different coding schemes. Typically the digital output will be a two's complement binary number that is proportional to the input, but there are other possibilities. An encoder, for example, might output a Gray code.

• The inverse operation is performed by a digital-to-analog converter (DAC).

ELECTRICAL SYMBOL

• The key parameters to test a SAR ADC are following:

• DC Offset Error• DC Gain Error• Signal to Noise Ratio (SNR)• Total Harmonic Distortion (THD)• Integral Non Linearity (INL)• Differential Non Linearity (DNL)• Spurious Free Dynamic Range• Power Dissipation

D/A CONVERTER

• a digital-to-analog converter (DAC or D-to-A) is a device that converts a digital (usually binary) code to an analog signal (current, voltage, or electric charge). An analog-to-digital converter (ADC) performs the reverse operation. Signals are easily stored and transmitted in digital form, but a DAC is needed for the signal to be recognized by human senses or other non-digital systems.

• A common use of digital-to-analog converters is generation of audio signals from digital information in music players. Digital video signals are converted to analog in televisions and mobile phones to display colors and shades. Digital-to-analog conversion can degrade a signal, so conversion details are normally chosen so that the errors are negligible.

• Due to cost and the need for matched components, DACs are almost exclusively manufactured on integrated circuits (ICs). There are many DACarchitectures which have different advantages and disadvantages. The suitability of a particular DAC for an application is determined by a variety of measurements including speed and resolution.

RECENT DEVELOPMENTS IN MICROPROCESSORS AND CONTROLLERS

•The recent development In microprocessor technology makes Implementation of advanced control strategies feasible at the generating level. A self-tuning (ST) proportional-plus-lntegral-plus-derivative (PID) digital automatic voltage regulator (DAVR) for a large synchronous machine is proposed and the influence of this regulator on the generator dynamic and transient stability is investigated. The algorithm for this regulator combines a least-square estimator with a digital PID control algorithm. The parameters of the PID control algorithm are computed and updated according to the estimated model. The dynamic performance of the machine when equipped with a digital PID governor is also presented. A comparison of the computer results as obtained from the simulation study are compared with the available experimental results.

Unit 3

ELECTRICAL DRIVES AND CONTROLLERS

Electromagnetic principles• "When a conductor is exposed to a changing magnetic field, an

electric current will flow in the conductor."• This principle is the basis for the generation of electricity. In a

typical large-scale operating electrical generator, an armature coil (a coil of wire of many turns) is wrapped around a soft iron armature and forced to spin in a powerful electromagnetic field. The spinning is achieved by forcing high-pressure steam (in a thermal generator), fast-flowing water (in a hydro generator), or wind (in a wind generator) across a turbine (similar to a propeller blade) attached to the end of the armature. As the armature spins, an electric current is induced (forced) to flow in the armature coil where it is extracted and sent to the electricity grid that supplies electricity across a broad area (the province of Ontario and beyond, for example). It is the direction of flow of this induced current that is addressed by Lenz's law.

SOLENOIDS

• In physics, the term refers specifically to a long, thin loop of wire, often wrapped around a metallic core, which produces a uniform magnetic field in a volume of space (where some experiment might be carried out) when an electric current is passed through it. Solenoids are important because they can create controlled magnetic fields and can be used as electromagnets.

• In engineering, the term may also refer to a variety of transducer devices that convert energy into linear motion. The term is also often used to refer to asolenoid valve, which is an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid, or a linear solenoid, which is an electromechanical solenoid.

SOLENOID

RELAYS• A relay is an electrically operated switch. Many relays

use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the signal coming in from one circuit and re-transmitting it to another. Relays were used extensively in telephone exchanges and early computers to perform logical operations.

ELECTROMECHANICAL RELAY

• A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays".

STEPPER MOTORS

• A stepper motor (or step motor) is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can then be commanded to move and hold at one of these steps without any feedback sensor (an open-loop controller), as long as the motor is carefully sized to the application.

TYPES OF STEPPER MOTORS• There are four main types of stepper motors:[1]

• Permanent magnet stepper (can be subdivided into 'tin-can' and 'hybrid', tin-can being a cheaper product, and hybrid with higher quality bearings, smaller step angle, higher power density)

• Hybrid synchronous stepper• Variable reluctance stepper• Lavet type stepping motor

SERVO MOTORS• A servomotor is a rotary actuator that allows for precise

control of angular position, velocity and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. It also requires a relatively sophisticated controller, often a dedicated module designed specifically for use with servomotors.

• Servomotors are not a different class of motor, on the basis of fundamental operating principle, but uses servomechanism to achieve closed loop control with a generic open loop motor.

• Servomotors are used in applications such as robotics, CNC machinery or automated manufacturing.

PROGRAMMABLE LOGIC CONTROLLER

• A Programmable Logic Controller, PLC or Programmable Controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. The abbreviation "PLC" and the term "Programmable Logic Controller" are registered trademarks of the Allen-Bradley Company (Rockwell Automation).

• PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory. A PLC is an example of a hard real time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.

MEMORY- INPUT , OUTPUT MODULES

• In computer architecture, the combination of the CPU and main memory (i.e. memory that the CPU can read and write to directly, with individual instructions) is considered the brain of a computer, and from that point of view any transfer of information from or to that combination, for example to or from a disk drive, is considered I/O. The CPU and its supporting circuitry providememory-mapped I/O that is used in low-level computer programming, such as the implementation of device drivers. An I/O algorithm is one designed to exploit locality and perform efficiently when data reside on secondary storage, such as a disk drive.

TIMERS- INTERNAL RELAYS

• A timer is a clock that controls the sequence of an event while counting in fixed intervals of time

• A timer is a specialised type of clock for measuring time intervals

Counters – shift registers

• In digital circuits a shift register is a cascade of flip-flops , sharing the same clock, in which the output of each flip flop is connected to the data input of next flip flop in the chain resulting in the circuit that shifts by one position the bit array stored in it,shifting in the data present at its input and shifting out the last bit in the array, at each transition of clock input.

Counter- timing

PLC- USING LADDER DIAGRAM

A ladder diagram represents a program in “LADDER LOGIC”

A ladder logic is a method of drawing electrical logic schematics.

PLC WITH LADDER LOGIC

PLC - APPLICATIONS

Unit 4

Limit Switch

• A limit switch is an electromechanical device that consists of an actuator mechanically linked to a set of contacts.

• When an object comes into contact with the actuator, the device operates the contacts to make or break an electrical connection.

• It can determine the presence or absence of an object. It was first used to define the limit of travel of an object; hence the name "Limit Switch."

Basic Components• Actuator: The portion of the switch that comes in

contact with the object being sensed.• Head: It houses the mechanism that translates

actuator movement into contact movement. When the actuator is moved as intended, the mechanism operates the switch contacts.

• Contact Block: It houses the electrical contact elements of the switch. It typically contains either two or four contact pairs.

Basic Components (contd.)

• Terminal Block: The terminal block contains the screw terminations. This is where the electrical (wire) connection between the switch and the rest of the control circuit is made.

• Switch Body: The switch body houses the contact block in a plug-in switch. It and terminal block in the nonplug-in switch.

• Base: The base houses the terminal block in a plug-in switch. Nonplug-in switches do not have a separate base.

Type-1 Nonplug-in Housing

• They are box shaped with a separate cover.

• Seals between the head, body, and cover are maintained by an O-ring and a flat gasket.

Type-2 Plug-in Housing

• Developed to ease replacement of the switch if needed.

• Plug-in housing splits in half to allow access to the terminal block for wiring.

• A set of stabs in the switch body “plugs” into sockets in the base to make electrical connections between the contact block and the terminal block.

Encoders• What is an encoder? An encoder is a sensor for converting rotary motion or position to a

series of electronic pulses • Advantages

Simplicity of construction (low cost)High sensitivity (depending upon the supply voltage)

• Disadvantages It includes the familiar drawbacks related to contacting and

communicating devices like friction, wear, brush bounce due to vibration, signal glitches and metal oxidation due to electrical arcing.

The types of encoders• Absolute encoders • Absolute encoders have a unique code that can be

detected for each angular position • Absolute encoders are much more complex and expensive

than incremental encoders

The types of encoders

• Incremental encoders • Pulses from LEDS are counted to provide rotary position • Two detectors are used to determine direction (quadrature) • Index pulse used to denote start point • Otherwise pulses are not unique

Temperature Sensor

• Temperature sensors appear in building, chemical process plants, engines, appliances, computers, and many other devices that require temperature monitoring

• Many physical phenomena depend on temperature, so we can often measure temperature indirectly by measuring pressure, volume, electrical resistance, and strain

Temperature Sensor

• Bimetallic Strip

• Application– Thermostat (makes or

breaks electrical connection with deflection)

Metal A

Metal B

δ

)]T-(T1[ 00 LL

Temperature Sensor

• Resistance temperature device.

0

11

0

00 )]T-(T1[

TTeRR

RR

Position Sensors

Position Sensors is a device that provides the position measurement of a component. A position sensor can be:

1.Linear2.Angular3.Multi-axis

Some of the well-known position sensors are:Linear Variable Differential Transformer (LVDT)Hall Effect SensorProximity Sensor

LDVT-Configuration

• An alternating current is driven through the primary, causing a voltage to be induced in each secondary proportional to its mutual inductance with the primary. The frequency is usually in the range 1 to 10 kHz.

Hall Effect Sensor• The Hall effect was discovered by Edwin Hall in

1879; “electron” was not experimentally discovered; had to wait until quantum mechanics came

• Development of semiconductor compoundsin 1950's led to first useful Hall effect magneticinstrument

• In the 1960's, first combinations of Hall elements and integrated amplifiers

– Resulted to classic digital output Hall switch– In 1965, first low-cost solid state sensor

Theory of the “Hall Effect”Hall effect principle, no magnetic field

Hall effect principle, magnetic field present

Potential Difference (voltage) across output:

V = I * B

Basic Hall Effect Sensor• Hall element is the basic

magnetic field sensor

• Differential Amplifier amplifies the potential difference (Hall voltage)

• Regulator holds current value so that the output of the sensor only reflects the intensity of the magnetic field

• Types 1. Unipolar

2.Latching 3.Bipolar

Proximity Sensor• A proximity sensor is a sensor able to detect the

presence of nearby objects without any physical contact.

• These sensors use mutual inductance between a known inductor and a conductive material

• Commonly referred to as “eddy current” probes• Mutual inductance is a function of the distance

between the inductor and the material

How “Eddy Currents” Work• An inductive coil is placed near a

conductive surface• An AC voltage (typically around

2Mhz) is applied to the coil• Mutual inductance begins to

occur• The coil generates a magnetic

field• Circular or “Eddy Currents” begin

to flow in the conductive material• These currents resemble an eddy

in a stream of water

How “Eddy Currents” Work• The Eddy Currents

generate their own magnetic field

• These fields have interaction with the coil through mutual inductance

• This leads to a measurable result

What can be measured?

• Electrical conductivity and magnetic permeability of the target material

• The amount of material cutting through the coils of the magnetic field

• The condition of the material(whether it contains cracks or defects

• Lift-Off

Pressure Sensor• Two Main Types of Pressure Sensors

Capacitive Sensors – Work based on measurement of

capacitance from two parallel plates.– C = εA/d , A = area of plates d =

distance between.– This implies that the response of a

capacitive sensor is inherently non-linear. Worsened by diaphragm deflection.

– Must use external processor to compensate for non-linearity

Pressure Sensor

Piezoresistive Sensors• Work based on the piezoresistive

properties of silicon and other materials.

• Piezoresistivity is a response to stress.• Some piezoresistive materials are Si,

Ge, metals.• In semiconductors, piezoresistivity is

caused by 2 factors: geometry deformation and resistivity changes.

Pressure Sensing • Pressure is sensed by mechanical

elements such as plates, shells, and tubes that are designed and constructed to deflect when pressure is applied.

• This is the basic mechanism converting pressure to physical movement.

• Next, this movement must be transduced to obtain an electrical or other output.

• Finally, signal conditioning may be needed, depending on the type of sensor and the application. Figure 8 illustrates the three functional blocks.

Pressure

Signal Conditioner

Sensing Element

Transduction element

displacement

electric

V or I output

Sensing Elements

• The main types of sensing elements are Bourdon tubes, diaphragms, capsules, and bellows

• All except diaphragms provide a fairly large displacement that is useful in mechanical gauges and for electrical sensors that require a significant movement

Potentiometric Pressure Sensors• Potentiometric pressure sensors

use a Bourdon tube, capsule, or bellows to drive a wiper arm on a resistive element.

• For reliable operation the wiper must bear on the element with some force, which leads to repeatability and hysteresis errors.

• These devices are very low cost, however, and are used in low-performance applications such as dashboard oil pressure gauges

Inductive Pressure Sensors• Several configurations based on

varying inductance or inductive coupling are used in pressure sensors. They all require AC excitation of the coil(s) and, if a DC output is desired, subsequent demodulation and filtering. The LVDT types have a fairly low frequency response due to the necessity of driving the moving core of the differential transformer

• The LVDT uses the moving core to vary the inductive coupling between the transformer primary and secondary.

Capacitive Pressure Sensors. • Capacitive pressure sensors typically use a thin diaphragm as

one plate of a capacitor. • Applied pressure causes the diaphragm to deflect and the

capacitance to change. • This change may or may not be linear and is typically on the

order of several picofarads out of a total capacitance of 50-100 pF.

• The change in capacitance may be used to control the frequency of an oscillator or to vary the coupling of an AC signal through a network.

• The electronics for signal conditioning should be located close to the sensing element to prevent errors due to stray capacitance.

INTRODUCTION OF TRANSDUCERS

• A transducer is a device that convert one form of energy to other form. It converts the measurand to a usable electrical signal.

• In other word it is a device that is capable of converting the physical quantity into a proportional electrical quantity such as voltage or current.

Pressure Voltage

BLOCK DIAGRAM OF TRANSDUCERS

• Transducer contains two parts that are closely related to each other i.e. the sensing element and transduction element.

• The sensing element is called as the sensor. It is device producing measurable response to change in physical conditions.

• The transduction element convert the sensor output to suitable electrical form.

CHARACTERISTICS OF TRANSDUCERS

1. Ruggedness2. Linearity3. Repeatability4. Accuracy 5. High stability and reliability6. Speed of response7. Sensitivity8. Small size

TRANSDUCERS SELECTION FACTORS1. Operating Principle: The transducer are many times selected

on the basis of operating principle used by them. The operating principle used may be resistive, inductive, capacitive , optoelectronic, piezo electric etc.

2. Sensitivity: The transducer must be sensitive enough to produce detectable output.

3. Operating Range: The transducer should maintain the range requirement and have a good resolution over the entire range.

4. Accuracy: High accuracy is assured.5. Cross sensitivity: It has to be taken into account when

measuring mechanical quantities. There are situation where the actual quantity is being measured is in one plane and the transducer is subjected to variation in another plan.

6. Errors: The transducer should maintain the expected input-output relationship as described by the transfer function so as to avoid errors.

Contd.7. Transient and frequency response : The transducer should meet

the desired time domain specification like peak overshoot, rise time, setting time and small dynamic error.

8. Loading Effects: The transducer should have a high input impedance and low output impedance to avoid loading effects.

9. Environmental Compatibility: It should be assured that the transducer selected to work under specified environmental conditions maintains its input- output relationship and does not break down.

10. Insensitivity to unwanted signals: The transducer should be minimally sensitive to unwanted signals and highly sensitive to desired signals.

CLASSIFICATION OF TRANSDUCERS

The transducers can be classified as: I. Active and passive transducers.II. Analog and digital transducers.III.On the basis of transduction principle used.IV.Primary and secondary transducerV. Transducers and inverse transducers.

Unit 5

Stages in designing Mechatronics Systems

Traditional and Mechatronics Design

• system is partitioned into individual homogenous subsystems according to the disciplines,

• homogenous subsystems are designed by specialists from a design team,

• each homogenous subsystem is designed by traditional way,

• each product function is from the most part realized by only one homogenous subsystem,

• ¾ interactions are minimized, emphasis is mainly laid on common interfaces of the subsystems.

• more functions, • higher efficiency and

reliability, • lower demands on energy, • minimal size and weight, • lower cost.

Engine Management Systems1.Throttle position sensor2.EGO sensor3.MAP Sensor4.Temperature sensor5.Speed/Timing Sensor6.EGR diagnostic switch7.EGR valve position sensor

Sensors and actuators in EMS

Pick and Place Robot

• The robot has three axis about which motion can occur.• The following movements are required for this robot. 1. clockwise and anticlockwise rotation of the robot unit on its base. 2. Linear movement of the arm horizontally i.e., extension or

contraction of arm. 3. Up and down movement of the arm and

4. Open and close movement of the gripper.• The foresaid movements can be obtained by pneumatic cylinder

which is operated by solenoid valves with limit switches.• Limits switches are used to indicate when a motion is completed.• The clockwise rotation of the robot unit on its base can be obtained

from a piston and cylinder arrangement during pistons forward movement

• v Similarly counter clockwise rotation can be obtained during backward

• movement of the piston in cylinder.

Control circuit diagram of the pick and place robot

Automatic car parking system• Consider an automatic car park system with barriers operated by coin

inserts.• The system uses a PLC for its operation.• There are two barriers used namely in barrier and out barrier. In barrier is

used to open when the correct money is inserted while out barrier open when the car is detected in front of it.

• It shows a schematic arrangement of an automatic car park barrier. It consists of a barrier which is pivoted at one end, two Solenoid valves A and B and a piston cylinder arrangement

• A connecting rod connects piston and barrier as shown in fig below Solenoid valves are used to control the movement of the piston.

• Solenoid A is used to move the piston upward inturn barrier whereas solenoid B is used to move the piston downward.

• Limit switches are used to detect the foremost position of the barrier. When current flows through solenoid A, the, piston in the cylinder moves upward and causes the barrier to rotate about its pivot and raises to let a car through

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