Classification of errors

1. Gross error 
2. Systematic error 

• Instrumental error
• Environmental error
• Observational error  

     3. Random error

Gross errors:

• These errors occurs due to human mistakes in reading instruments and recording and calculating results of measurements
• Impossible to eliminate gross error completely
• Mathematical analysis of gross error is impossible.
  These errors can be avoided by 2 means

1. Immense care should be taken while taking the reading and recording the data
2. Two THREE OR EVEN MORE READING should be taken for the quantity being measured

Systematic error:
 These are mainly due to the short comings of the instruments and the characteristics  of the material used in instruments such as defective or worn parts environmental effects etc.
    A constant uniform deviation of the operation of an instrument is known as systematic error
There are 3 types of systematic error

1. Instrumental error
2. environmental error
3. Observation error

1. Instrumental errors:
   These errors arise due to
   Inherent short coming in the instruments,misuse of the instruments,loading effects of the instruments
   
   Misuse of instruments : A good instrument used in an unintelligent way may give erroneous result
   
    
2. Environmental error:
   These errors are due to condition external to the measuring device
   ex: Effects of pressure, temperature dust,humidity
   
   These errors can be eliminated by the following  measure

• using instruments in controlled condition
• apply suitable correction to instruments reading 
• apply combated correction
• using sophisticated devices

     3.  Observational errors: These errors occurs due to carelessness of operators
Reasons:

• Working scale reading and working reading of data
• Inaccurate estimations of average reading
• In correct conversion of units 
• Tendency to read high or low.
   

    4.Random errors:
            Some errors still result though the systematic and instrumental errors are reduced or atleast accounted for.
The cause of such errors are unknown and hence the errors are called random error

These errors are generally due to the accumulation of large number of small effects.These errors are generally small,Hence these errors are of real concern only when the high degree of accuracy is required.

Modes of measurements

1. Primary measurement 
2. Secondary measurement
3. Tertiary measurement 

1. Primary measurement: 

•  In this case sought value of parameter is determined by comparing it directly withing reference standard 
• There is no conversation of measurand in terms of length
  1. measurement of time by counting the number of stroke of the clock.
  2. Matching of 2 length when determining the lenght of an object with a ruler
  3.   Matching of 2 colors when judging the temperature of a red hot steel.
     

2.Secondary measurement:

The indirect measurement ,these involving 1 translation. 

•  temperature measurement by  mercury in glass(Thermometers)
• pressure measurement by manometer.
  
  

3.Tertiary measurement:

The indirect measurement ,these are involving 2 translations

• The measurement of temperature of an object by thermocouple.

Standards of measurement

1. Primary standard
2. Secondary standard
3. Working standard 

1. Primary standard: The highest standard of either a base unit or a derived unit is called as primary standard.These standard are copies of international prototypes and are kept by national standard laboratory. These standardized units are quite stable independent invariant.The primary standards constitute the ultimate bases of the references and are used for the reference verification and calibration of secondary standards.The primary standard are not available for the use outside the national laboratories
   
   
2. Secondary standard: These are the reference calibrated standard designed and calibrated from the primary standards.These are sent periodically to the national standard laboratory for their calibration.These standard are kept by the measurement laboratories and the industrial organization
   
   
3. Working standard: These standard have an accuracy one order lower than that of the secondary standard.These are normal standard used by the workers and technician who actually carry out measurement.

Fundamental measuring process, Significance of measurements

The basic requirement for getting meaning full result or measurement are:

1. The standard employed for comparison purpose must be accurately defined and should be commonly acceptable
2. The standard must be of the same character as the measurand 
3. Standard is prescribed and defined by a legal or recognized agency  or organization example: INDIAN bureau of standards, ISO
4. The apparatus used and method adopted for the comparison purpose must be prove able

Significance of measurements:

1. Measurement plays a very significant role in every branch of scientific research and engineering processes which includes the following 

• Control system
• process instrumentation
• data reduction
• automation 

   2.  Through measurement a product can be designed or a process be operated with maximum efficiency minimum cost and with desired degree or reliability and maintainability

Measurement system

Measurement: it is the act or the result of a quantitative comparison between a pre-determined   standard and an unknown magnitude.
    The procedure and apparatus employed for obtaining the comparison must be prove-able the procedure  for this is called calibration.

         Measurand: The physical quantity or the characteristic condition which is the object of measurement in an instrument in an instrumentation system and it is variously termed as measurand or measurement  variable or instrumentation variable or process variable. The measurand may be fundamental or derived quantity. 


Fundamental quantity: It is the physical quantity which independent of any other quantities 

Derived quantity: It is the physical quantity which is derived from the fundamental quantity.
Eg. speed velocity acceleration. 

Instrumentation: The technology of using instruments to measure and control the physical and chemical properties of material is called instrumentation. 



Basic representation of measurement system 

Input signal===>measurement system===>output signal

Input to the measuring system is known as measurand ,output is called measurement 

Microsensors in Machatronics

The facilities which exist for the fabrication of miniature semiconductor components are adapted for  micro sensor design and development. The technology of sensor development is also known by the names micro mechanics and micro machining . 


     Micro sensor technology is an outgrowth of mechatronics industry because it uses the same materials and fabrication processes as integrated circuits. Fabricating a semi conductor device such as a transistor involves several processes

• Growing pure crystals of silicon
• growing layers of silicon dioxide
• Doping the silicon with impurities to change its semiconducting properties
• photo lithography
• etching.

Semiconductors are basically two-dimensional in nature and the devices are etched onto the top surface of silicon wafers. This technology has been extended to three dimensions in the case of micro sensors.


Sensing principle of micro sensors : 
     The primary characteristics of the micro sensors is that  it responds to a physical stimulus and transmits an impulse.
A signal is fed to the sensors that changes the form of energy, usually into electrical energy.The variable manipulation elements can convert the signal from analog to digital and can amplify or modulate the signal
Also contained in the sensing mechanism is a power supply for sensing and modulating purposes.

Manufacturing Management level and control level

Supervisory manufacturing is responsible for linking and co-ordinating the quality of production with the material , manufacturing process, energy and cost . These requirements are handled by sensors integrated with adaptive process control capability at plant level, manufacturing process and control level. 


      SENSOR LEVEL: 
At the sensory level, frequently required tasks in production processes are distance measurement, contour tracking, pattern recognition , identification of process parameters and machine diagnostics.

Sensors for condition monitoring

Condition monitoring is defined as determining the  machine status or the condition of a device and its changes with time in order to decide its condition at any given time. 
   The condition of the machine can be determined by physical parameters like tool wear, machine vibrations, noise, temperature,oil contamination. A change in these parameters provides an indication of the changing machine condition. 


   AUTOMATED FACTORY:

• An automated factory is required to have sensors at different levels in the production system
• The need for sensing and condition monitoring arises from the unexpected disturbances and tolerances vibrations in the manufacturing environment. 
• A major factor in the development of an intelligent and flexible mechatronics system is the concurrent use of automated diagnostic systems using sensors to handle machinery maintenance and process control operations.
• Sensors help to production process by compensating for unexpected disturbances any tolerance changes in the work pieces or other changes due to management decision 
• The data coming from different levels of the factory provide for support for automated manufacturing. 

Actuators

Actuators are another important components of a mechatronics system. Actuators are usually electrical,mechanical,fluid power or pneumatic based.They transform electrical inputs into mechanical outputs such as force,angle and position.


Actuators can be classified into 3 general groups: 

• Electromagnetic actuators 

eg: AC & DC electrical motors, stepper motor, electromagnets.

• Fluid power actuator:

eg: hydraulic, pneumatics 

• Unconventional actuators: 

eg: piezoelectric, memory metal. 

 

 

 

Mechatronics system employ actuators or drives that are part of the physical process being monitored and controlled. Actuation is the result of a direct physical action on the process, such as removed of a work piece from a conveyor system or application of a force,it has a direct effect upon the process.

 

 

    Actuators take low power signals transmitted from the computer and produce high power signals that are applied as input to the process. Electrical actuators converts electrical command signals into mechanical motions.

Sensors

In every applications sensors transform real world data into electrical signals. 
    
     A sensors is defined as follows: 
A device that produces an output signal for the purpose of sensing of a physical phenomenon. 
sensors are also referred to as transducers. A transducer is a device that converts a signal from one physical form to a corresponding signal that has a different physical form. 
     In a transducer, the quantities at the input level and the output level are different
A typical input signal could be electrical,mechanical,thermal or optical.Sensors are required to monitor the performance of machine and processes using a collection of sensors, one can monitor one or more variable in process. 

      The monitoring devices are generally located near the manufacturing process measuring the surface quality temperature vibrations and flow rate of cutting fluids . Some of the variables in mechatronics system are temperature,speed,position,force,torque and acceleration. 

    Micro sensors could be used to measure flow,pressure or acceleration of various chemical species in environmental and mechanical applications. The resonant micro beams are already being used to sense linear and rotational acceleration. 

Visual programming

A visual programming language is designed to be interactive. Using wires and pictures to represent equalities and functions instead of complicated text expressions 
    Block-diagram based visual programming ,  Block-diagram based visual language including matrix easy5 simulink vissim and lab view

    All block diagram languages consists of two fundamental objects: 

• Signal wires
• blocks 

1. Signal wire: A single wire transmits a signal or a value from its point of origination(block) to its point of termination(another block). The direction in which the signal flows is defined by an arrow head on the signal wire. Once the flow direction has been defined for given signal wire, signals may only flow in the forward direction. 
2. Block: A block is a processing element that operates on input signal and parameters or constant to produce output signals. 

There is a 3 block basics that all block diagram languages possess 

• summing junction
• gain
• integrator blocks 

Computer system

For mechatronics applications computer systems hardware is usually restricted to computer specific circuits and devices. These include logic networks, flip flops ,counters,timers,triggers,integrated circuit and microprocessor

Fast computer hardware is of little value without the appropriate software to operate it. Computers can be programed at several levels. 

Machine level:

• It is also called as chip level programming
• In machine language program all communication is in terms of ones and zeros
• Programming in machine language is a slow,tedious and error prone task  

Assembly language: 
The language consists of a collections of short acronyms or abbreviations like ADD, MUL, DIV. 


High level language: 
The languages like BASIC,FORTRAN,C and PASCAL which will not dependent on internal structure of CPU . Most high level language require that a compiler be used for machine code translation.    

Categories of electrical system

Power system: 

Power system are designed to transmit large quantities of electrical energy not information between points efficiency.Frequently rotating machines are used to convert the energy between electrical and mechanical domains.Generators convert energy from mechanical to electrical. Motors are used to converts energy from electrical to mechanical. 

Communication System:

These are designed to transmit information as low energy electrical signals between points.such functions as information storage,processing and transmission are common parts of a communication system.This area of electrical engineering is often called electronics...

Electrical system are integral parts of a Mechatronics application The following electrical components are frequently found in such applications 

• Motors and generator

• Sensors and actuators(transducer)

• Solid state devices including computer

• circuits(signal conditioning,impedance,amplifiers)

• Contact devices(relay,circuit breakers,switches,fuses)  

Electrical System

Electrical System are concerned with the behavior of three fundamental quantities like charge, current and voltage.

 

Charge:

The charge carried by electrons of an atoms is called electricity.And it is represented by Qunit of charge is coulomb 'c' .

Current:

Continuous flow of electrons in a conductor in a particular direction is called electric current. or 

Rate of flow charge in a conductor in a particular direction is called current (I)

It is represented by I. 

SI unit of current is Ampere. 

 

Voltage: 

It is the measure of electrical pressure between two points of a electrical circuit. 

When a current exists electrical energy is usually being transmitted from one part to another. 

 

 Electrical system consists of two categories: 

1.power system

2.communication system 

The principle Transmissibility

The principle Transmissible is the equilibrium or motion of a rigid body remains unchanged if a force acting at a given point is replaced by a force of the same magnitude and direction and direction , but acting at different point,provided that the two forces have the same line of action. 

        

           Conditions of equilibrium or motion are not affected by transmitting a force along its line of action.

 

 

System of Units:

3 types.

1. length 

2. mass

3. time 

• Meter(l)-kilogram(m)-second(t) [MKS] these are SI units 

Mechanical systems will be expressed in system international(s.i)

 

Mechanical systems:

Mechanical system are concerned with the behavior of matter under the action of forces.
    Mechanical systems are categorized as

• Rigid-body
• deformable body
• fluid system  

Rigid body system: A rigid body system assumes all bodies and connections in the system to perfectly rigid

Deformation: The actual systems are not rigid, some deformation always results as various load are applied.

                 Normally the deformation are small and do not appreciably affects the motion of                      the rigid body system .

 

Fluid system: The field of mechanics consists of compressible and incompressible fluids. An important subcategory of incompressible fluids is hydraulics, which is study of the forces,energy and pressure of liquid in motion. 

 

In mechanical systems few laws will come

1. Newtonian mechanics
2. Newton 1st law
3.  Newton 2nd law
4. Newton 3rd law
5. Newtons law of gravity
6. Parallelogram law for the addition of forces

Mechatronics key elements part 2

SIMULATION:
Simulation is the process of solving the model and is preformed on a computer
The process of simulation can be divided into 3 sectors:

• Initialization
• Iteration
• Termination or display  

If the starting point is a block diagram based  model description
In initialization section the equation for each of the block must be sorted according to hte pattern in which the blocks have been connected

Iteration section:  The iteration section solves any differential equation present in the model using numerical integration or differentiation

Display section:    the display section of a simulation is used to present and past process the output . output may be saved to file displayed as a digital reading or graphically displayed as a chart strip chart meter read out or even animation

Automatic control:  control is a general term and can occur in living beings as well as machines . The term automatic control describes the simulation in which a machine is controlled by another machine.
Control involves modification of a system behavior, a transfer function is used to represent a control system
The transfer function is the ratio of the output variable to the input variable

One of the crucial ingredient of automatic control is feed back.
It provides the mechanism for attenuating the effects of parameters variations and disturbances .

Mechatronics key elements(part 1)

1 . Information system: This includes all the aspect of information transmission from signal processing to control system to analysis techniques
An information system is combination of four disciplines:

1. Communication system
2. signal processing
3. control system
4. numerical system   

In mechatronics applications we are most concern with the modeling,simulation,automatic control and numerical method for optimization modeling

• Modeling:  

 Modeling is the process of representing the behavior of the real system by a collection of mathematical equation and logic

The term real system is nothing but a physical system that is a system whose behavior is based on matter and energy

Models can be broadly categorized as

1. Static model
2. dynamic model 

Static model:
 In a static model there is no energy transfer . Systems that are static , produce no motion heat transfer fluid flow traveling waves or  anything that changes.

Dynamic model:
A dynamic model has energy transfer that results in power flow.
power or rate of range of energy causes motion heat transfer and other phenomenon  that changes in time.

Intoduction to mechatronics

Mechatronics is a subject that is made up of Electronics, Mechanical,information technology and control system.
    It is also the future of the world all the modern  equipment and machines are controlled my mechatronics systems like CNC PLC etc 


Mechatronics is a methodology used for the optimal design of electromechanical products. A methodology is a collections of particles procedure and rules used by those who work in a particular branch of knowledge or disciple.

The mechatronics system is multidisciplinary embodying and fundamental disciplines like electrical,mechanical,computer science,and information technology

mechatronics is the result of applying information system to physical systems .The physical system consists of mechanical,electrical,computer system as well as sensors actuators and real time interfacing . This block is also called as electromechanical system

Mechatronics=information system+electromechanical system