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introduction to mechatronics

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Mechatronics

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introduction to mechatronics

  1. 1. Introduction to Mechatronics After mid Prepared by Imran khan 13me12 Introduction to mechatronics (by Imran khan 13me12) 1
  2. 2. Actuators • Actuators • An actuator is a device that is responsible for moving or controlling a mechanism or system. It is operated by a source of energy, which can be mechanical force, electrical current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion. An actuator is the mechanism by which a control system acts upon an environment. The control system can be simple (a fixed mechanical or electronic system), software-based (e.g. a printer driver, robot control system), a human, or any other input. • An actuator is a type of motor that is responsible for moving or controlling a mechanism or system. • It is operated by a source of energy, typically electric current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion. An actuator is the mechanism by which a control system acts upon an environment. The control system can be simple (a fixed mechanical or electronic system), software-based (e.g. a printer driver, robot control system), a human, or any other input. Introduction to mechatronics (by Imran khan 13me12) 2
  3. 3. Introduction to mechatronics (by Imran khan 13me12) 3
  4. 4. Introduction to mechatronics (by Imran khan 13me12) 4
  5. 5. •Selection of Actuators:- • By the type of movement • Multi-turn. • Quarter-turn. • Linear. • Lever. Introduction to mechatronics (by Imran khan 13me12) 5
  6. 6. • By the energy source • Manual • Electric: they can be derived by direct and alternate current. • Pneumatic: they use pressured air or gas to create motion. They are widely used in the industry due to their low cost. In case of failure they are easy to diagnose or repair in field, rather than electric actuators. • Oleo-Hydraulic Introduction to mechatronics (by Imran khan 13me12) 6
  7. 7. • Functionality • On / Off valve service • Positioning to % open • Modulating to control changes on flow conditions • Emergency Shut Down (ESD) Introduction to mechatronics (by Imran khan 13me12) 7
  8. 8. Types:- • Hydraulic • A hydraulic actuator consists of a cylinder or fluid motor that uses hydraulic power to facilitate mechanical operation. The mechanical motion gives an output in terms of linear, rotary or oscillatory motion. Because liquid is nearly incompressible, a hydraulic actuator can exert considerable force, but is limited in acceleration and speed. • The hydraulic cylinder consists of a hollow cylindrical tube along which a piston can slide. The term double acting is used when pressure is applied on each side of the piston. A difference in pressure between the two side of the piston results in motion of piston to either side. The term single acting is used when the fluid pressure is applied to just one side of the piston. The piston can move in only one direction, a spring being frequently used to give the piston a return stroke. Introduction to mechatronics (by Imran khan 13me12) 8
  9. 9. • Electric • An electric actuator is powered by a motor that converts electrical energy to mechanical torque. The electrical energy is used to actuate equipment such as multi-turn valves. It is one of the cleanest and most readily available forms of actuator because it does not involve oil. • Recently, new type of actuators which can be actuated by applying thermal or magnetic energy have drawn many interest and attention and in many commercial applications, due to their superior and unique properties (i.e. more compact, lightweight, high power density and economical).[1] This actuators are using shape memory materials (SMMs), such as shape memory alloys (SMAs) or magnetic shape-memory alloys (MSMAs) Introduction to mechatronics (by Imran khan 13me12) 9
  10. 10. • Mechanical • A mechanical actuator functions by converting rotary motion into linear motion to execute movement. It involves gears, rails, pulleys, chains and other devices to operate. An example is a rack and pinion. Introduction to mechatronics (by Imran khan 13me12) 10
  11. 11. • LINEAR ACTUATORS - CALCULATING STROKE LENGTH AND FORCE • The first step in determining the size of a linear actuator needed to move a specific load requires the user to calculate translational force. To calculate translational force, four components must be considered: mass, friction, gravity and other counter-forces within the system. Each component must be solved for in the equation to yield the appropriate sized actuator. A sample calculation will be provided to help users determine the size of the actuator. A list of terms related to the calculation is also necessary from proper understanding of the variables in the equations. Introduction to mechatronics (by Imran khan 13me12) 11
  12. 12. • Variables in the Linear Actuator Equation • The terms and variables related to determining the size of linear actuators are explained below to help you understand the equation that follows: • T = Total Linear Force (lbf) Ff = Force From Friction (lbf) Fa = Acceleration Force (lbf) Fg = Force Due to Gravity (lbf) Fp = Applied Force (lbf) WL = Weight of Load (lbf) U = Angle of Inclination (lbf) ta = acceleration time (sec) v = final velocity µ = coefficient of sliding friction g = acceleration of gravity = 386.4 in/sec. • Sample Calculation for Actuator Selection Introduction to mechatronics (by Imran khan 13me12) 12
  13. 13. • Select the Appropriate Automation Device • Now that the force required for this application has been calculated, the proper actuator can be selected. In this instance, actuators with a rating up to 200 pounds would suffice. Standard linear actuators would be required. Typically, standard linear actuators can withstand forces between 150 and 400 pounds. Introduction to mechatronics (by Imran khan 13me12) 13
  14. 14. Introduction to mechatronics (by Imran khan 13me12) 14
  15. 15. • Examples and applications • In engineering, actuators are frequently used as mechanisms to introduce motion, or to clamp an object so as to prevent motion. In electronic engineering, actuators are a subdivision of transducers. They are devices which transform an input signal (mainly an electrical signal) into motion Introduction to mechatronics (by Imran khan 13me12) 15
  16. 16. • Examples of actuators • Comb drive • Electric motor • Electroactive polymer • Hydraulic piston • Piezoelectric actuator • Pneumatic actuator • Relay • Servomechanism Introduction to mechatronics (by Imran khan 13me12) 16
  17. 17. Motor • Motor • An electric motor is an electric machine that converts electrical energy into mechanical energy. • In normal motoring mode, most electric motors operate through the interaction between an electric motor's magnetic field and winding currents to generate force within the motor. In certain applications, such as in the transportation industry with traction motors, electric motors can operate in both motoring and generating or braking modes to also produce electrical energy from mechanical energy. Introduction to mechatronics (by Imran khan 13me12) 17
  18. 18. • Application of Motor • Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives, electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as from the power grid, inverters or generators. Small motors may be found in electric watches Introduction to mechatronics (by Imran khan 13me12) 18
  19. 19. Types of Electric Motors Introduction to mechatronics (by Imran khan 13me12) 19
  20. 20. DC motor • Definition:- • A DC motor is any of a class of electrical machines that converts direct current electrical power into mechanical power. The most common types rely on the forces produced by magnetic fields. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current flow in part of the motor. Most types produce rotary motion; a linear motor directly produces force and motion in a straight line. • DC motors were the first type widely used, since they could be powered from existing direct-current lighting power distribution systems. A DC motor's speed can be controlled over a wide range, using either a variable supply voltage or by changing the strength of current in its field windings. Small DC motors are used in tools, toys, and appliances. The universal motor can operate on direct current but is a lightweight motor used for portable power tools and appliances. Larger DC motors are used in propulsion of electric vehicles, elevator and hoists, or in drives for steel rolling mills. The advent of power electronics has made replacement of DC motors with AC motors possible in many applications. Introduction to mechatronics (by Imran khan 13me12) 20
  21. 21. • Electromagnetic motors • A coil of wire with a current running through it generates an electromagnetic field aligned with the center of the coil. The direction and magnitude of the magnetic field produced by the coil can be changed with the direction and magnitude of the current flowing through it. • A simple DC motor has a stationary set of magnets in the stator and an armature with one or more windings of insulated wire wrapped around a soft iron core that concentrates the magnetic field. The windings usually have multiple turns around the core, and in large motors there can be several parallel current paths. The ends of the wire winding are connected to a commutator. The commutator allows each armature coil to be energized in turn and connects the rotating coils with the external power supply through brushes. (Brushless DC motors have electronics that switch the DC current to each coil on and off and have no brushes.) • The total amount of current sent to the coil, the coil's size and what it's wrapped around dictate the strength of the electromagnetic field created. • The sequence of turning a particular coil on or off dictates what direction the effective electromagnetic fields are pointed. By turning on and off coils in sequence a rotating magnetic field can be created. These rotating magnetic fields interact with the magnetic fields of the magnets (permanent or electromagnets) in the stationary part of the motor (stator) to create a force on the armature which causes it to rotate. In some DC motor designs the stator fields use electromagnets to create their magnetic fields which allow greater control over the motor. Introduction to mechatronics (by Imran khan 13me12) 21
  22. 22. • Brushed • A brushed DC electric motor generating torque from DC power supply by using an internal mechanical commutation. Stationary permanent magnets form the stator field. Torque is produced by the principle that any current-carrying conductor placed within an external magnetic field experiences a force, known as Lorentz force. In a motor, the magnitude of this Lorentz force (a vector represented by the green arrow), and thus the output torque, is a function for rotor angle, leading to a phenomenon known as torque ripple) Since this is a single phase two-pole motor, the commutator consists of a split ring, so that the current reverses each half turn ( 180 degrees). • The brushed DC electric motor generates torque directly from DC power supplied to the motor by using internal commutation, stationary magnets (permanent or electromagnets), and rotating electrical magnets. • Advantages of a brushed DC motor include low initial cost, high reliability, and simple control of motor speed. Disadvantages are high maintenance and low life-span for high intensity uses. Maintenance involves regularly replacing the carbon brushes and springs which carry the electric current, as well as cleaning or replacing the commutator. These components are necessary for transferring electrical power from outside the motor to the spinning wire windings of the rotor inside the motor. Brushes consist of conductors. Introduction to mechatronics (by Imran khan 13me12) 22
  23. 23. • Brushless • Typical brushless DC motors use one or more permanent magnets in the rotor and electromagnets on the motor housing for the stator. A motor controller converts DC to AC. This design is mechanically simpler than that of brushed motors because it eliminates the complication of transferring power from outside the motor to the spinning rotor. The motor controller can sense the rotor's position via Hall effect sensors or similar devices and can precisely control the timing, phase, etc., of the current in the rotor coils to optimize torque, conserve power, regulate speed, and even apply some braking. Advantages of brushless motors include long life span, little or no maintenance, and high efficiency. Disadvantages include high initial cost, and more complicated motor speed controllers. Some such brushless motors are sometimes referred to as "synchronous motors" although they have no external power supply to be synchronized with, as would be the case with normal AC synchronous motors. Introduction to mechatronics (by Imran khan 13me12) 23
  24. 24. • Shunt Wound DC Motor:- • The shunt wound DC motor falls under the category of self-excited DC motors, where the field windings are shunted to, or are connected in parallel to the armature winding of the motor, as its name is suggestive of. And for this reason both the armature winding and the field winding are exposed to the same supply voltage, though there are separate branches for the flow of armature current and the field current as shown in the figure of DC shunt motor below. Introduction to mechatronics (by Imran khan 13me12) 24
  25. 25. • Separately excited dc motor:- • In this section we will discuss about the separately excited dc motor. Like other DC motors, these motors also have both stator and rotor. Stator refers to the static part of motor, which consists of the field windings. And the rotor is the moving armature which contains armature windings or coils. Separately excited dc motor has field coils similar to that of shunt wound dc motor. The name suggests the construction of this type of motor. Usually, in other DC motors, the field coil and the armature coil both are energized from a single source. The field of them does not need any separate excitation. But, in separately excited DC motor, separate supply provided for excitation of both field coil and armature coil. Figure below shows the separately excited dc motor. • Here, the field coil is energized from a separate DC voltage source and the armature coil is also energized from another source. Armature voltage source may be variable but, independent constant DC voltage is used for energizing the field coil. So, those coils are electrically isolated from each other, and this connection is the specialty of this type of DC motor. Introduction to mechatronics (by Imran khan 13me12) 25
  26. 26. • Series Wound DC Motor:- • A series wound DC motor like in the case of shunt wound DC motor or compound wound DC motor falls under the category of self-excited dc motors, and it gets its name from the fact that the field winding in this case is connected internally in series to the armature winding. Thus the field winding are exposed to the entire armature current unlike in the case of a shunt motor. Introduction to mechatronics (by Imran khan 13me12) 26
  27. 27. • Construction of Series DC Motor • Construction wise this motor is similar to any other types of DC motors in almost all aspects. It consists of all the fundamental components like the stator housing the field winding or the rotor carrying the armature conductors, and the other vital parts like the commutator or the brush segments all attached in the proper sequence as in the case of a generic DC motor. Yet if we are to take a close look into the wiring of the field and armature coils of this DC motor, it’s clearly distinguishable from the other members of this type. Introduction to mechatronics (by Imran khan 13me12) 27
  28. 28. • Compound DC motors:- • DC compound motor is essentially a combination of Series DC motor and Shunt DC motor Introduction to mechatronics (by Imran khan 13me12) 28
  29. 29. • Construction • In a compound motor, we have both series winding and parallel winding. A winding is connected in series with the armature as in a Series DC motor. Another winding is connected in shunt with the armature as in a Shunt DC motor. This combination presents us the double advantage of having the torque characteristics of a series motor and the constant speed characteristic of a shunt motor in one compound wound motor. Introduction to mechatronics (by Imran khan 13me12) 29
  30. 30. Introduction to mechatronics (by Imran khan 13me12) 30 • Permanent Magnet DC Motor or PMDC Motor • Electric current carrying conductor is placed inside a magnetic field, there will be mechanical force experienced by that conductor. All kinds of DC motors work in this principle only. Hence for constructing a dc motor it is essential to establish a magnetic field. The magnetic field is obviously established by means of magnet. The magnet can by any types i.e. it may be electromagnet or it can be permanent magnet. When permanent magnet is used to create magnetic field in a DC motor, the motor is referred as permanent magnet dc motor or PMDC motor. Have you ever uncovered any battery operated toy, if you did, you had obviously found a battery operated motor inside it. This battery operated motor is nothing but a permanent magnet dc motor or PMDC motor. These types of motor are essentially simple in construction. These motors are commonly used as starter motor in automobiles, windshield wipers, washer, for blowers used in heaters and air conditioners, to raise and lower windows, it also extensively used in toys. As the magnetic field strength of a permanent magnet is fixed it cannot be controlled externally, field control of this type of dc motor cannot be possible. Thus permanent magnet dc motor is used where there is no need of speed control of motor by means of controlling its field. Small fractional and sub fractional kW motors now constructed with permanent magnet.
  31. 31. Ac motor • An AC motor is an electric motor driven by an alternating current (AC). The AC motor commonly consists of two basic parts, an outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft producing a second rotating magnetic field. The rotor magnetic field may be produced by permanent magnets, reluctance saliency, or DC or AC electrical windings. Introduction to mechatronics (by Imran khan 13me12) 31
  32. 32. • The two main types of AC motors are classified as induction and synchronous. The induction motor (or asynchronous motor) always relies on a small difference in speed between the stator rotating magnetic field and the rotor shaft speed called slip to induce rotor current in the rotor AC winding. As a result, the induction motor cannot produce torque near synchronous speed where induction (or slip) is irrelevant or ceases to exist. In contrast, the synchronous motor does not rely on slip-induction for operation and uses either permanent magnets, salient poles (having projecting magnetic poles), or an independently excited rotor winding. The synchronous motor produces its rated torque at exactly synchronous speed. The brushless wound-rotor doubly fed synchronous motor system has an independently excited rotor winding that does not rely on the principles of slip-induction of current. The brushless wound-rotor doubly fed motor is a synchronous motor that can function exactly at the supply frequency or sub to super multiple of the supply frequency. Introduction to mechatronics (by Imran khan 13me12) 32
  33. 33. Induction motor • An asynchronous motor type of an induction motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor as are found in universal, DC and synchronous motors. Introduction to mechatronics (by Imran khan 13me12) 33
  34. 34. • Stepper motor • 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. • Switched reluctance motors are very large stepping motors with a reduced pole count, and generally are closed-loop commutated. Introduction to mechatronics (by Imran khan 13me12) 34
  35. 35. • Servo System • A servo drive receives a command signal from a control system, amplifies the signal, and transmits electric current to a servo motor in order to produce motion proportional to the command signal. Typically the command signal represents a desired velocity, but can also represent a desired torque or position. A sensor attached to the servo motor reports the motor's actual status back to the servo drive. The servo drive then compares the actual motor status with the commanded motor status. It then alters the voltage frequency or pulse width to the motor so as to correct for any deviation from the commanded status. • In a properly configured sp control system, the servo motor rotates at a velocity that very closely approximates the velocity signal being received by the servo drive from the control system. Several parameters, such as stiffness (also known as proportional gain), damping (also known as derivative gain), and feedback gain, can be adjusted to achieve this desired performance. The process of adjusting these parameters is called performance tuning. • Although many servo motors require a drive specific to that particular motor brand or model, many drives are now available that are compatible with a wide variety of motors. Introduction to mechatronics (by Imran khan 13me12) 35
  36. 36. • Universal motor • The universal motor is so named because it is a type of electric motor that can operate on AC or DC power. It is a commutated series-wound motor where the stator's field coils are connected in series with the rotor windings through a commutator. It is often referred to as an AC series motor. The universal motor is very similar to a DC series motor in construction, but is modified slightly to allow the motor to operate properly on AC power. This type of electric motor can operate well on AC because the current in both the field coils and the armature (and the resultant magnetic fields) will alternate (reverse polarity) synchronously with the supply. Hence the resulting mechanical force will occur in a consistent direction of rotation, independent of the direction of applied voltage, but determined by the commutator and polarity of the field coils. • Universal motors have high starting torque, can run at high speed, and are lightweight and compact. They are commonly used in portable power tools and equipment, as well as many household appliances. They're also relatively easy to control, electromechanically using tapped coils, or electronically. However, the commutator has brushes that wear, so they are much less often used for equipment that is in continuous use. In addition, partly because of the commutator, universal motors are typically very noisy, both acoustically and electromagnetically. Introduction to mechatronics (by Imran khan 13me12) 36
  37. 37. • Ques1: A 3 φ (phase) 4 pole 50 hz induction motor runs at 1460 rpm. find its %age slip. • Formula • N s = 120f/p Solution N s = 120f/p = 120*50/4 = 1500r.p.m. Running speed of motor = n= 1460r.p.m. Slip S=( N s–N)/ N s*100 =(1500-1460) x 100 / 1500 = 2.667% Introduction to mechatronics (by Imran khan 13me12) 37
  38. 38. • Ques2: A 12 pole 3 φ(phase) alternator driver at speed of 500 r.p.m. supplies power to an 8 pole 3 φ induction motor. If the slip of motor is 0.03p.u, calculate the speed. Solution Frequency of supply from alternator, f=PN/120 =12*500/120 = 50hz where P= no of poles on alternative N=alternator speed is rpm. Synchronous speed of 3 φ induction motor N=120f/Pm =120*50/8 = 750 rpm. Speed of 3 φ induction motor N=Ns (1-s) =750(1-0.03) = 727.5 rpm. Introduction to mechatronics (by Imran khan 13me12) 38
  39. 39. • Ques3: A motor generates set used for providing variable frequency ac supply consists of a 3-φ(phase) synchronous and 24 pole 3 φ synchronous generator. The motor generate set is fed from 25hz, 3 φ ac supply. A 6 pole 3 φ induction motor is electrically connected to the terminals of the synchronous generator and runs at a slip of 5%. Find a) the frequency of generated voltage of synchronous generator b) the speed at which induction motor is running Solution Speed of motor generator set Ns=(120*f1(supply freq))/(no of pole on syn motor) =120*25/10 = 300 rpm. (a) frequency of generated voltage fz=speed of motor gen set voltage *no of poles on syn gen/120 = 300*24/120 = 60hz (b) Speed of induction motor , Nm=Ns(1-s) =120 fz /Pm(1-s) = 120*60/6(1-0.05) = 1140 rpm. Introduction to mechatronics (by Imran khan 13me12) 39
  40. 40. • Ques4: A 3-φ(phase) 4 pole induction motor is supplied from 3φ(phase) 50Hz ac supply. Find (1) synchronous speed (2) rotor speed when slip is 4% (3) the rotor frequency when runs at 600r.p.m. Solution 1) Ns =120f/p =120*50/4 = 1500 rpm. 2) speed when slip is 4% or .04 N=Ns (1-s) =1500(1-0.04) = 1440 rpm. 3) slip when motor runs at 600 rpm. S’=(Ns –N)/Ns =(1500-600)/1500 = 0.6 Rotor frequency f’ = S’f = 0.6*50 = 30Hz. Introduction to mechatronics (by Imran khan 13me12) 40
  41. 41. Introduction to mechatronics (by Imran khan 13me12) 41
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  43. 43. • Q15. A moving coil instrument gives a full scale detection of 20mA. When a potential difference of 50mV is applied. Calculate the series resistance to measure 500V on scale? Answer. Im = 20mA V = 250V Vm = 50mV R= V/Im - Rm = (500/20) x 103 - 2.5 = 25000 - 2.5 R = 24997.5 Ω Introduction to mechatronics (by Imran khan 13me12) 43
  44. 44. Interfacing Ports Introduction to mechatronics (by Imran khan 13me12) 44 • Interfacing Ports • The I/O ports are very essential in any computer system because they enable the user to communicate with the system. In this experiment, we will design and implement a very simple form of I/O ports (switches for input and LEDs for output). • The input port should be designed to pass the data on the input switches to the data bus if and only if an input instruction (I/O read cycle) is executed by the CPU. This can be achieved using a tri-state buffer that will be enabled only during I/O read cycles. The output port should be capable of storing the data on the bus when the CPU performs an output instruction (I/O write cycle). In this case, a latch can be used to store the output data and supply it continuously to the LEDs. The latch should be enabled to pass its input to the LEDs only when the CPU is writing to the output port (i.e. I/O write cycle). Just as each memory location has its own (memory) address, each I/O port has its own (port) address. However, since we are using only one input port and one output port, we will not assign any addresses to our I/O port. Thus, I/O instructions can use dummy addresses to access our I/O ports.
  45. 45. • Objective • Interfacing simple I/O ports the 8086 microcomputer system Introduction to mechatronics (by Imran khan 13me12) 45
  46. 46. • Input/output port • Alternatively referred to as I/O address, I/O ports, and I/O port address, the input/output port is what allows the software drivers to communicate with hardware devices on your computer. In your computer there are 65,535 ports that are numbered from 0000h to FFFFh. • The I/O port assignment can be made either manually using DIP switches or automatically using PnP. When configuring the I/O port of any device in your computer, it is important that it does not share the same I/O port as another device or you will encounter a hardware conflict. Introduction to mechatronics (by Imran khan 13me12) 46
  47. 47. Introduction to mechatronics (by Imran khan 13me12) 47
  48. 48. • Analog-to-digital converter • 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 been converted from a continuous-time and continuous-amplitude analog signal to a discrete-time and discrete-amplitude digital signal. • An ADC is defined by its bandwidth (the range of frequencies it can measure) and its signal to noise ratio (how accurately it can measure a signal relative to the noise it introduces). The actual bandwidth of an ADC is characterized primarily by its sampling rate, and to a lesser extent by how it handles errors such as aliasing. The dynamic range of an ADC is influenced by many factors, including the resolution (the number of output levels it can quantize a signal to), linearity and accuracy (how well the quantization levels match the true analog signal) and jitter (small timing errors that introduce additional noise). The dynamic range of an ADC is often summarized in terms of its effective number of bits (ENOB), the number of bits of each measure it returns that are on average not noise. An ideal ADC has an ENOB equal to its resolution. ADCs are chosen to match the bandwidth and required signal to noise ratio of the signal to be quantized. If an ADC operates at a sampling rate greater than twice the bandwidth of the signal, then perfect reconstruction is possible given an ideal ADC and neglecting quantization error. The presence of quantization error limits the dynamic range of even an ideal ADC, however, if the dynamic range of the ADC exceeds that of the input signal, its effects may be neglected resulting in an essentially perfect digital representation of the input 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). Introduction to mechatronics (by Imran khan 13me12) 48
  49. 49. • Digital-to-analog converter • In electronics, a digital-to-analog converter (DAC,D/A, D2A or D-to-A) is a function that converts digital data (usually binary) into an analog signal (current, voltage, or electric charge). An analog-to-digital converter (ADC) performs the reverse function. Unlike analog signals, digital data can be transmitted, manipulated, and stored without degradation, albeit with more complex equipment. But a DAC is needed to convert the digital signal to analog to drive an earphone or loudspeaker amplifier in order to produce sound (analog air pressure waves). • DACs and their inverse, ADCs, are part of an enabling technology that has contributed greatly to the digital revolution. To illustrate, consider a typical long-distance telephone call. The caller's voice is converted into an analog electrical signal by a microphone, then the analog signal is converted to a digital stream by an ADC. The digital stream is then divided into packets where it may be mixed with other digital data, not necessarily audio. The digital packets are then sent to the destination, but each packet may take a completely different route and may not even arrive at the destination in the correct time order. The digital voice data is then extracted from the packets and assembled into a digital data stream. A DAC converts this into an analog electrical signal, which drives an audio amplifier, which in turn drives a loudspeaker, which finally produces sound. Introduction to mechatronics (by Imran khan 13me12) 49
  50. 50. • Multiplexer • In electronics, a multiplexer (or mux) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. A multiplexer of 2n inputs has n select lines, which are used to select which input line to send to the output. Multiplexers are mainly used to increase the amount of data that can be sent over the network within a certain amount of time and bandwidth. A multiplexer is also called a data selector. • An electronic multiplexer makes it possible for several signals to share one device or resource, for example one A/D converter or one communication line, instead of having one device per input signal. • Conversely, a de-multiplexer (or demux) is a device taking a single input signal and selecting one of many data-output-lines, which is connected to the single input. A multiplexer is often used with a complementary demultiplexer on the receiving end. • An electronic multiplexer can be considered as a multiple-input, single-output switch, and a demultiplexer as a single-input, multiple-output switch.[3] The schematic symbol for a multiplexer is an isosceles trapezoid with the longer parallel side containing the input pins and the short parallel side containing the output pin.[4] The schematic on the right shows a 2-to-1 multiplexer on the left and an equivalent switch on the right. The seal wire connects the desired input to the output. Introduction to mechatronics (by Imran khan 13me12) 50
  51. 51. Logic Gates • Logic Gates • A logic gate is an elementary building block of a digital circuit. Most logic gates have two inputs and one output. At any given moment, every terminal is in one of the two binary conditions low (0) or high (1), represented by different voltage levels. Introduction to mechatronics (by Imran khan 13me12) 51
  52. 52. Truth Table Introduction to mechatronics (by Imran khan 13me12) 52 • AND Gates • The AND gate is a basic digital logic gate that implements logical conjunction - it behaves according to the truth table to the right. A HIGH output (1) results only if both the inputs to the AND gate are HIGH (1). If neither or only one input to the AND gate is HIGH, a LOW output results. • The AND gate is so named because, if 0 is called "false" and 1 is called "true," the gate acts in the same way as the logical "and" operator. The following illustration and table show the circuit symbol and logic combinations for an AND gate. (In the symbol, the input terminals are at left and the output terminal is at right.) The output is "true" when both inputs are "true." Otherwise, the output is "false.“ Input 1 Input 2 Output 0 0 0 0 1 0 1 0 0 1 1 1
  53. 53. • NAND Gates • The NAND gate operates as an AND gate followed by a NOT gate. It acts in the manner of the logical operation "and" followed by negation. The output is "false" if both inputs are "true." Otherwise, the output is "true." Truth Table Introduction to mechatronics (by Imran khan 13me12) 53 Input 1 Input 2 Output 0 0 1 0 1 1 1 0 1 1 1 0
  54. 54. • OR Gates • The OR gate gets its name from the fact that it behaves after the fashion of the logical inclusive "or." The output is "true" if either or both of the inputs are "true." If both inputs are "false," then the output is "false.“ Truth Table Introduction to mechatronics (by Imran khan 13me12) 54 Input 1 Input 2 Output 0 0 0 0 1 1 1 0 1 1 1 1
  55. 55. • XOR Gates • The XOR ( exclusive-OR ) gate acts in the same way as the logical "either/or." The output is "true" if either, but not both, of the inputs are "true." The output is "false" if both inputs are "false" or if both inputs are "true." Another way of looking at this circuit is to observe that the output is 1 if the inputs are different, but 0 if the inputs are the same. Truth Table Introduction to mechatronics (by Imran khan 13me12) 55 Input 1 Input 2 Output 0 0 0 0 1 1 1 0 1 1 1 0
  56. 56. • NOR Gates • The NOR gate is a combination OR gate followed by an inverter. Its output is "true" if both inputs are "false." Otherwise, the output is "false." Truth Table Introduction to mechatronics (by Imran khan 13me12) 56 Input 1 Input 2 Output 0 0 1 0 1 0 1 0 0 1 1
  57. 57. • XNOR Gates • The XNOR (exclusive-NOR) gate is a combination XOR gate followed by an inverter. Its output is "true" if the inputs are the same, and "false" if the inputs are different. Truth Table Introduction to mechatronics (by Imran khan 13me12) 57 Input 1 Input 2 Output 0 0 1 0 1 0 1 0 0 1 1 1
  58. 58. • NOT Gates • A logical inverter , sometimes called a NOT gate to differentiate it from other types of electronic inverter devices, has only one input. It reverses the logic state. Truth Table Introduction to mechatronics (by Imran khan 13me12) 58 Input Output 1 0 0 1
  59. 59. • Using of Combination of Gates • Using combinations of logic gates, complex operations can be performed. In theory, there is no limit to the number of gates that can be arrayed together in a single device. But in practice, there is a limit to the number of gates that can be packed into a given physical space. Arrays of logic gates are found in digital integrated circuits (ICs). As IC technology advances, the required physical volume for each individual logic gate decreases and digital devices of the same or smaller size become capable of performing ever-more-complicated operations at ever-increasing speeds. Introduction to mechatronics (by Imran khan 13me12) 59
  60. 60. Encoders Encoders:- • An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security or compressions. Introduction to mechatronics (by Imran khan 13me12) 60
  61. 61. • Types of Encoders • Software for encoding audio, video, text into standardized formats: • A compressor encodes data (e.g., audio/video/images) into a smaller form (See codec.) • An audio encoder may be capable of capturing, compressing and converting audio • A video encoder may be capable of capturing, compressing and converting audio/video • An email encoder secures online email addresses from email harvesters • A PHTML encoder preserves script code logic in a secure format that is transparent to visitors on a web site • A multiplexer combines multiple inputs into one output. • 8b/10b encoder used for fast speed in communication system Introduction to mechatronics (by Imran khan 13me12) 61
  62. 62. Encoder: • An encoder is a combinational logic circuit which converts non-digital data to digital data. • An encoder has 2n input lines and n output lines. The output lines generate a binary code corresponding to the input value. • For example a single bit 4-to-2 encoder takes in 4 bits and outputs 2 bits. An encoder combinational circuit that performs the inverse operation of a decoder. The truth table of an encoder is shown in Table 13-16 Introduction to mechatronics (by Imran khan 13me12) 62
  63. 63. Encoder Introduction to mechatronics (by Imran khan 13me12) 63
  64. 64. Decoder • Decoder is combinational logic circuit multiple-input, multiple-output logic circuit which converts digital data to non-digital data. • A 3-to-8 decoder is implemented using three inverters and eight 3-input AND gates, as shown in Fig. 13-21. The three inputs A, B, C are decoded into eight outputs. Each one of the AND gates produce one main terms of the input variables. Introduction to mechatronics (by Imran khan 13me12) 64
  65. 65. Introduction to mechatronics (by Imran khan 13me12) 65

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