Control Lab

An-Najah National University Faculty of Engineering & IT Department of Mechatronics engineering

2018

Table of Experiments No. of experiment Exp. 1 Exp. 2 Exp. 3 Exp. 4 Exp. 5 Exp. 6 Exp. 7 Exp. 8 Exp. 9 Exp.10

Prepared by: Eng. Waleed Abuzaina

Experiment Name

Page

General Instructions Level-Pressure Level-Pressure Transducer Transducer and control

3 4

Luminosity Luminosity Transducer Transducer and and control control Temperature transducer and control

14 24

Pressure transducer and control Speed and Position transducer and control 3-Phase Induction Motor speed control PWM Speed Regulator of a DC Motor

31 38 53 61

Stepper Motor Control Flow Rate Transducer and control Process control simulation

69

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General Instructions

1- It's 1- It's forbidden to enter the Lab. without lab. Supervisor or class teacher. 2- Computers 2- Computers must be turned off safely after its use. 3- It's 3- It's forbidden to take anything from Lab. without supervisor permission. 4- It's 4- It's forbidden to put your things (bags, clothes, jacket) on Lab. table. 5- Any Any visit in the lab and in the the duration of lab work is forbidden forbidden even for a short time. 6- It's 6- It's forbidden to play or joke in the Lab. 7- Read 7- Read the experimental manual before applying it, understand supervisor's orders, be sure that you understand the procedure of doing the experiment 8- It's 8- It's forbidden to play or even touch any device does not relate to your experiment.

Safety Instructions 1- Use 1- Use tools and devices with full responsibility and awareness. 2- Students 2- Students must be conscious while being in the Lab. 3- Do 3- Do not turn on a device without the supervisor permission. 4- In 4- In case of fault and/or bad operation, turn off the equipment and do not tamper it after ask the supervisor


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Ex eriment 2 1: Experiment

Level Level Pressure Transducer Pressure And control (G30A and Transducer And control G30B)

(G30A and G30B)


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1. Introduction: 1.1 Level Pressure Transducer (Module G30A): 1.1.1 DESCRIPTION OF THE EQUIPMENT: Module G30A together with unit TY30A/EV creates an educational system for the analysis of the transducer techniques of physical variables such as LEVEL. Module G30A includes all that part of electronics dealing with the conditioning, control and display of the physical variables under test while unit TY30A/EV generates these physical variables. Unit TY30A/EV is also provided with sensors (a level). The module is divided into 8 parts each performing a different function. Each part is limited by a dotted line which encloses the electrical diagram of the block. In the right side of the module, there are two parts for the connection to unit TY30A/EV and to the external computer. In the top angle at right there are the terminals to power the module: the module needs two voltages equal to 12Vdc 0.5A, a voltage equal to 5Vdc 1A for the logic part and interfacing to the computer and a voltage equal to +12V dc with current equal to 1.5 A to supply the pump of unit TY30A/EV. The connection of the module to the unit is made via a red and a black terminal and an 8-poles socket of din type: the terminals and the sockets are fitted on the side of unit TY30A/EV and on the left part of the module. The two terminals are used to power the pump which takes the water from the tank which is under the upper vertical one and the din socket is used to connect the signal of the transducers to the module. Figure1.1 shows the silk screen diagram of the module while Figure 1.2 shows unit TY30A/EV.

Fig 1.1


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Fig 1.2

1.1.2MEASUREMENT OF LEVEL AND PRESSURE: (Analog Type Output): With pressure and level measurements, the pressure sensor set at the bottom of the vertical column of unit TY30A/EV is used.

Definition of an Analog Variable : An analog measurement ring permits the generation of a D.C. voltage which behavior follows the water level in the column; this means that each value of the column corresponds to only one value of the output voltage. So there is analogy between the level and the variable representing it (output voltage of the measurement system). We can say that a variable or information is analog when it varies in continuous, or when, it cannot be discontinuous by its own nature. This means that an analog variable (in our case, the water level of the column) can take infinite values.

The Pressure Sensor: Under static condition, the level of a liquid is linked to pressure, according to a law of proportionality. If "L" represents the level, which is the height, of a liquid in a tank, the pressure at the bottom will be given by: P = L. g. M S where: p = pressure (Pa = Pascal = N.m -2 = 105 bar) L = level (m) g = acceleration of gravity (g = 9,81 m·s -2) Ms = specific mass of liquid (kg·m-3). Prepared by: Eng. Waleed Abuzaina

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Consequently, it is sufficient to measure the pressure to obtain the level. Among the different available pressure transducers, the STRAIN GAUGE ones have become the mostly used. The operating principle of these transducers is the piezoresistivity (property of the materials which change their resistance as function of the deformation to which they are subjected). The four resistors connected at Wheatstone's bridge are taken from a silicon diaphragm (fig 1.3). The diaphragm is then welded on a glass ring which supports it. The bridge is powered on a diagonal by a constant voltage generator and a voltage variable with pressure which acts on the diaphragm is taken from the opposite diagonal.

Fig 1.3 The strain gauges are resistors, whose resistive value depends on the deformations they are subjected. In the sensor used, the resistors are connected with a Wheat stone's bridge, so the output voltage VO varies proportionally with pressure. The sensor used in our system has an operation range ("pressure range") which varies from 0 to 0.07 bar. The dynamic of the output voltage of the last circuit is of 42 mV (which represents the Full-Scale Output), when there is a power voltage of 10V. This device is available as differential sensor or, in this case, as absolute pressure sensor. In module G30A, the connection between level sensor and its signal conditioner is carried out via a cable to be inserted on the 8-pin DIN sockets marked as "TRANSDUCERS".

1.2 Level - Pressure Control (Module G30B): 1.2.1 DESCRIPTION OF THE EQUIPMENT: Module G3B enables the experimental analysis of automatic control techniques and, together with module G30A carries out the automatic control of level. It consists of a synoptic panel showing the electrical diagram of each single block composing the whole circuit, the connections between the different blocks and the measurement points. Fig 1.3 shows the silk screen printed diagram of the module. It is evident that the module is divided into 3 function blocks which include the same number of the electrical circuits. These electrical circuits have precise functions inside the whole circuit and so they are schematically separated.


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Fig 1.3

Description of the blocks: The level controller G30B is composed by the following blocks

-

Setpoint. Error amplifier. PID controller. Power Amplifier.

Setpoint: it is the block used to set the wished value to the output variable. Error Amplifier: it compares the value set using the setpoint and the one actually obtained across the output. PID controller: it processes the error signal (output of the block error amplifier) so that the output takes the wished behavior. Power Amplifier: it doses the electrical power supplied by the power supply of the actuator to vary the value of the output variable.

1.3 Regulation with PID controllers: 1.3.1 Regulation with P controller: With this kind of regulator the output signal of the controller is proportional to its input signal : the variable which can be varied in this case is the constant of proportionality, e.g. the ratio between output and input. There is a value of the output signal for each value of the input signal: this value is determined by the constant of proportionality. The above side is true only if the controller is ideal; with a real controller, if the constant of proportionality is too big or if the constant or proportionality is too high, there is saturation and consequently a nonlinear behavior. It is obvious that the behavior is linear only for a limited band of input values (proportional band). Refer to fig 1.4, to see this fact better. Fig 1.4 Prepared by: Eng. Waleed Abuzaina

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The error signal, obtained by the comparison between the reference signal (wished value for t he output) and the signal supplied by the signal conditioner of the transducer (value effectively obtained across the output), normally constitutes the input signal of the controller; this signal, on passing across the proportional controller, is amplified by the constant of proportionality (K P ). Outside the proportional band (where the behavior is linear) the controller determines a production of ON/OFF power, e.g. the actuator is applied all the power available or nothing, while inside it the power is modulated. Once the transistor are modulated, the power supplied by the amplifier of the actuator, depends on the power supplied by the load and by the efficiency of the same actuator. The main characteristic of this controller is to have an error always deferent from zero; we can affirm that the error is proportional to the gain of the regulator and depends on the coefficient K P increases, if the error diminishes; the system gets toward unstable condition. According to the proportional band set there are different behaviors of the controlled variable (in this case level) as function of time. Fig 1.5 shows different behavior of automatic control of level with: a) Too large Bp. b) Correct Bp. c) Too narrow Bp.

Fig 1.5

1.3.2 Regulation with PI and PID controllers: In the integrative controller, the output voltage is the integral of the input voltage. The main disadvantage of the controller with proportional action is that it always needs an input voltage different from zero (and consequently an error different from zero in close loop control systems) to have an output voltage different from zero. With the integrative action, there can be an output different from zero with null output and then the error with at steady state can be reduced to zero. Then, the great advantage of the integrative controller is to reach a steady state with null error. Anyway, if the inertia of the system is high or if the time constant of the integrative action is high, it may happen that the system is taken unstable conditions (oscillations). To solve this problem, we can put together the proportional and the integrative actions, in order to exploit the advantages of both regulations and reduce the introduced problems. If the oscillations remain, you can add the derivative action, together with the proportional – integrative one: the effectiveness of the derivative action depends largely on the controlled variable. In the derivative controller the output is the derivate of the input function and so it has a high influence on the signals which rapidly vary. As limit case with constant input voltage, its output is null. While the process evolves, the derivative action decades and the integrative one takes its place to reduce the regulations error to zero in respect to the steady state value. We will see, that in case of Prepared by: Eng. Waleed Abuzaina

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level and position regulation, the influence of the derivative action is very poor due to the fact that the variables under test very slowly.

3. Exercises: 3.1 Characteristic of the Level Transducer with 7-segment Display Output and characteristic curve between level and V output: Procedure: 1-Connect terminal +12V, ground, -12V and +5, ground and +12, ground of panel to regulated power supply. 2- Connect the digital voltmeter between terminal 6 and ground. 3- Connect between terminal 6 and analog In 0 and ground from board to the ground of terminal board TB1. 4- Switch I1 to the position "LEVEL". 5- Switch I3 to the position "FREQUENCY". 6- Discharge valve of the vertical tank closed. 7- Valve in series with the open pump. 8- Carry out the jumpers indicated in Figure 3.1. 9- Turn on the board and fill (charge) the tank using I4 on with every step 50mm and fill the result in table 1.

Fig 3.1 Table 1 Actual Level (mm) 0 50 100 150 200 250 300 350 400 450 500 Prepared by: Eng. Waleed Abuzaina

Measured Level (mm)

V output from multimeter (volt)

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3.2 Close loop control system with P controller: 1- Carry out the circuit of the fig 3.2. 2- On the PID controller block, turn the PROPORATIONAL knob to the half value. 3- Connect all the necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table2 by the knob, and use multimeter to check the value.

Fig 3.2 6- Measured the value of the error from output of error amplifier (use Multimeter) and Level from LCD 7 - segment. 7- Fill the result in table 2. Table 2 Setpoint Error Level (volt) (volt) (mm) 0 2 4 6 8 8- Plot a Cartesian graph, where the setpoint is on the x-axis and level is on the y-axis. 9- Plot another Cartesian graph, where the setpoint is on the x-axis and error is on the y-axis.

3.3 Close loop control system with PI controller: 1- Carry out the circuit of the fig 3.3. 2- On the PID controller block, turn the PROPORATIONAL knob to the half value and INTEGRATIVE knob to half value. 3- Connect all the necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table3 by the knob, and use multimeter to check the value.


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Fig 3.3 6- Measured the value of the error from output of error amplifier (use Multimeter) and Level from LCD 7 - segment. 7- Fill the result in table 3. Table 3 Setpoint Error Level (volt) (volt) (mm) 0 2 4 6 8 8- Plot a Cartesian graph, where the setpoint is on the x-axis and level is on the y-axis. 9- Plot another Cartesian graph, where the setpoint is on the x-axis and error is on the y-axis.

3.4 Close loop control system with PID controller: 1- Carry out the circuit of the fig 3.4. 2- On the PID controller block, turn the PROPORATIONAL knob to the half value, INTEGRATIVE and DERIVATIVE knob to half value. 3- Connect all the necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table4 by the knob, and use multimeter to check the value. 6- Measured the value of the error from output of error amplifier (use Multimeter) and Level from LCD 7 - segment. 7- Fill the result in table 4.


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Fig 3.4

Setpoint (volt) 0 2 4 6 8

Table 4 Error (volt)

Level (mm)

8- Plot a Cartesian graph, where the setpoint is on the x-axis and level is on the y-axis. 9- Plot another Cartesian graph, where the setpoint is on the x-axis and error is on the y-axis. 10- Compare between the graphs of error in 3 last parts and detect which one has a small error.

3.5 Variations of the PID CONTROLLER Constants: 1. Carry out the circuit of figure 3.4 2. Turn on the power supply and set the level at 300mm after that disconnect the connection between setpoint and error amplifier. 3. Set the function generator for a square-wave output with amplitude ranging from 0 and +4 Volt and frequency of 100 Hz and apply this signal between terminal 2 and ground. 4. Apply one probe of the oscilloscope to the output of the signal generator 5. Set the PID CONTROLLER to operate with the three actions inserted contemporarily 6. Apply the second probe of the oscilloscope to terminal 12 and check the system response to the input stress. 7. Turn on the power supply 8. Using the oscilloscope, put the two signals on top of each other 9. Set all Kp, Ki and Kd to minimum and record the results. 10. Set Kp to half position and record the results 11. Set Ki to half position and record the results 12. Set Kd to half position and record the results 13. Change the values of Kp, Ki and Kd until he system will become stable and then discuss the results. Prepared by: Eng. Waleed Abuzaina

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Experiment Ex eriment 2:2:

Level Pressure Transducer Luminosity Transducer And control (G30A and and Control (G13) G30B)


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1. Description of the Module: Module G13 with unit TY13/EV enables the study of light transducers and carries out the automatic control of light. Module G13 consists of 7 separate blocks (see spaces enclosed inside dotted lines in figure 1.1).

Fig 1.1 These blocks are: Set-point PID Controller Error Amplifier Power Amplifier Signal Conditioners Photoresistor Conditioner Photodiode Conditioner Phototransistor Conditioner We are going to analyze the operation of all these blocks in the following chapters, from an electrical point of view and also as a system (input/output ratio and transfer function). Module G13 is powered by a dual voltage equal to ±12 Vdc 0.5A and a voltage equal to 30Vde 0.5A. The external unit TY13/EV (see fig 1.2) contains the actuator (3-Watt incandescent lamp), 3 different light transducers (photodiode, phototransistor, photoresistor) and a second actuator t o generate a trouble signal. The connection between unit TY13/EV and module G13 is achieved via a cable with a 8-pole socket and two unipolar wires: the power amplifier is connected to the actuator via these two wires, while the module powers the transducers and receives their output signals via the 8 -pole cable. The connection between the two parts is achieved by inserting the proper cables on the right side of module G13 (which is called LIGHT PROCESS UNIT).


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Fig 1.2

2. Light Transducers: Light transducers are devices which transform the light radiation into an electrical quantity (resistance, current) and can be used in industry as light transducers and also as indirect transducers of other physical quantities such as position, angular speed and so on. A light radiation is that region of the electromagnetic spectrum which includes the infrared, visible and ultraviolet components. Part of the light radiation can be detected by the human eye and is defined as visible radiation or “Light”. The human eye, anyway, is differently affected by the different wave -lengths of the visible radiation. Interacting with substance, the light radiation produces different effects. Among which, there is the “Photoelectric Effect” which consists in the liberation of electrons by electromagnetic radiation incident on a metal surface and in case of semiconductors, in the generation of electron hole pairs. The first phenomenon is called photoemission and is applied to phototubes, photomultipliers and so on. As far as concerns the photoelectric effects on semiconductors, they can be divided into two kinds and precisely: 1. Photoconductive Effect The conductivity of a semiconductor bar depends on the intensity of the light radiation which strikes it. 2 Photoelectric effect on the junction (Photovoltaic Effect) The current across a reversely biased P-N junction depends on the intensity of the light radiation. If the junction is not biased, an electromotive force is generated across it (Photovoltaic effect). Devices belonging to the first category are called photoresistor, while those belonging to the second are called photodiodes, photoelectric cells and phototransistors. Hereafter follow a detailed analysis of these devices.


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2.1 Photoresistors: The photoresistor is a passive semiconductor component without junction. Figure 2.1 shows the resistance-irradiation characteristic curve of the photoresistor, with related symbol. When crossed by a light radiation, it varies its resistance as a result of the photoconductive effect: the resistance drops when the light increases. In dark conditions, the photoresistor practically acts as an insulating piece, as it has resistance values measured in M  (dark resistance); if strongly illuminated it has very low resistance values measured up to some tens of  . The material used for a photoresistor determines the wavelength at which the device presents the maximum sensitivity. The following materials are used as photo sensible materials: crystal of cadmium supplied or lead for sensors within the visible range and crystal of cadmium solenoid for sensors in the infrared range. The parameters of a photoresistor are, in addition to the characteristic curve or the resistive values related to determine light values, are: • The wavelength at which it presents the maximum sensitivity. • The maximum power which can be dissipated. • The maximum voltage peak. The photoresistor used in unit TY13/EV has the following main characteristics (see data sheet for details): • Resistance (10.76 Lux) 100 K  • Resistance (1076 Lux) 2400  • Minimum dark resistance 4 M 

Fig 2.1

2.2 Photodiode: The photodiode is a device which structure is similar to a common semiconductor diode, with a P-N junction, and, for this kind of use, it is reversely biased. In dark conditions, the photodiode operates as a common semiconductor diode, while, when the junction is crossed by a light radiation, the reverse current increases. Fig 2.2 shows a typical relation between illumination and reverse current together with the symbol of the device. Prepared by: Eng. Waleed Abuzaina

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The reverse current of photodiodes can take values ranging inside some nA and some tens of mA and the mostly used semiconductor materials are silicon, germanium, gallium arsenide and other semiconductor compounds. Particularly, silicon photodiodes have the maximum sensitivity to light radiations with wavelength ranging within 0.8 and 0.9 m, while germanium photodiodes within 1.6 and 1.8 m, i.e. in the region of the infrared. The characteristics can be improved with a P-I-N structure, i.e. interposing a not doped semiconductor (Intrinsic) between the two doped semiconductors P and N. If a photodiode, which is not biased and without load, is illuminated, it is crossed by a voltage generated inside the junction by the interaction between the light radiation and the semi conductive material (photovoltaic effect). If, then a load is applied to the photodiode, there is a passage of current and , in this way , a generator of electrical energy is created. The above said is the operating principle of “Photovoltaic cells” (further details on these devices can be found in specialized literature). The typical parameters of photodiodes, beside the characteristic curve or the resistive values concerning some light values, are: • The maximum reverse voltage which can be applied across it. • The maximum power which can be dissipated. • Maximum switching speed (rise and fall times). The photodiode used in unit TY13/EV is P-I-N silicon type has the following characteristics (see data sheet for details): • Maximum reverse voltage: 32 Vdc • Maximum sensitivity 0.9 um • Maximum dark current 30 nA • Reverse current with illumination equal to 1mW/cm2:50 uA • No-load voltage (1000 Lux): 350 mV • Rise and fall times 50 ns.

Fig 2.2


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2.3 Phototransistor: The phototransistor is a device with a structure similar to the one of a standard transistor, but with a photo sensible base. It is generally NPN kind, it is powered with a positive voltage between Collector and Emitter and the Base can be left open or connected to the emitter with a resistor. In this second case, the sensitivity of the phototransistor can be adjusted by varying the value of the resistor used. On dark conditions, the current of the collector Ic is minimum and increases with illumination. Fig. 2.3 shows the symbol with the typical diagram of the connection of the phototransistor; furthermore it shows the characteristic curve with the relation between the variations of Ic and the variations of the illumination E. The main parameters of a phototransistor, in addition to the characteristic curve, are: • The maximum dark current • The wavelength of maximum sensitivity • The switching speed (rise and fall times) • The maximum admitted values of current, voltage and power. The phototransistor used in the equipment has the following main characteristics (see data sheets for details): • Dark current 20 uA • Rise time 8 ms • Fall time 6 ms • Vceo max 30 Vdc

Fig 2.3


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3. Exercises: 3.1Detection of the Characteristic Curve of the Photoresistor: The purpose of this exercise is to determine the characteristic curve of the photoresistor at variation of the illumination.

Procedure: 1- Carry out the circuit of figure 3.1. 2- Set the switch of the PHOTORESISTOR CONDITIONER block to the position A 3- Set the multimeter to measure the resistance and connect it between terminals 16 and 17. 4- Connect module G13 to all the necessary supplies. 5- Set the lamp to the maximum distance with the slide. 6- Set the potentiometer of the SET-POINT block to the maximum value (300 Lux). 7- Move the lamp near the light transducers with the slide and in correspondence to the divisions shown on the panel of unit TY13/EV, read the resistance value indicated by the multimeter and report them in table 1. 8- Plot a graph with illumination on the x-axis and resistance on the y-axis and draw the points detected. 9- The characteristic curve of the transducer is obtained by joining these points. 10- Remove the multimeter from terminals 16 and 17, take the switch to B and insert the multimeter, selected as voltmeter for DC voltage, between terminal 18 and ground. Fig 3.1 11- Repeat all the last measurements: in this case measure the response of the transducer together with the one of the signal conditioner. Plot a graph with illumination on the x-axis and voltage on the y-axis and draw the points detected. 12- The characteristic curve of the transducer together with its signal conditioner is obtained by joining these points. 13- Confront the quality of the two graphs. Table 1 Illumination Resistance Voutput (Lux) (ohm) (volt) 1200 612 370 248 177 133 104 83 62 57


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3.2 Closed-loop Automatic Control of Light: P controller 1. Carry out the circuit of figure3.2:

Fig3.2 2. Set the slide of unit TY13/EV to the position 300 lux and the switches of the signal conditioner of the PHOTODIODE to the position B 3. Insert only the proportional action of the controller (connect only terminals 4 and 5) and take the PROPORTIONAL handle to the minimum value 4. With the set-point knob, apply a voltage of 1 Volt and measure the voltage of terminal 15 (output of the error amplifier) which corresponds to the difference between the set-point and the obtained output quantity 5. Repeat the previous step while increasing the set-point voltage from 1 to 8 Volt and fill the results in the table 2. 6. Repeat the previous steps after changing PROPORTIONAL handle to half position.

Setpoint (volt)

Table 2 Kp at minimum value Error V output (volt) (volt)

Kp at half value Error V output (volt) (volt)

0 1 2 3 4 5 6 7 8


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3.3 Closed-loop Automatic Control of Light: P controller 1. Carry out the circuit of figure3.3:

Fig3.3 2. Set the slide of unit TY13/EV to the position 300 lux and the switches of the signal conditioner of the PHOTODIODE to the position B 3. Insert the proportional action and integrative action of the controller and take the PROPORTIONAL handle to the half value and take the INTEGRATIVE handle to the min. value 4. With the set-point knob, apply a voltage of 1 Volt and measure the voltage of terminal 15 (output of the error amplifier) which corresponds to the difference between the set-point and the obtained output quantity 5. Repeat the previous step while increasing the set-point voltage from 1 to 8 Volt and fill the results in the table 2. 6. Repeat the previous steps after changing Integrative handle to half position. Table 3 Setpoint (volt)

Ki at minimum value Error V output (volt) (volt)

Ki at half value Error V output (volt) (volt)

0 1 2 3 4 5 6 7 8


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3.4 Variations of the PID CONTROLLER Constants: 1. Carry out the circuit of figure 3.4

Fig 3.4 2. Set the slide of unit TY13/EV to the position 300 lux and the switches of the signal conditioners (PHOTORESISTOR, PHOTODIODE, PHOTOTRANSISTOR CONDITIONER) to the position B 3. Set the function generator for a square-wave output with amplitude ranging from 0 and +4 Volt and frequency of 100 Hz and apply this signal between terminal 14 and ground. 4. Apply one probe of the oscilloscope to the output of the signal generator 5. Set the PID CONTROLLER to operate with the three actions inserted contemporarily 6. Apply the second probe of the oscilloscope to terminal 11 and check the system response to the input stress. 7. Turn on the power supply 8. Using the oscilloscope, put the two signals on top of each other 9. Set all Kp, Ki and Kd to minimum and record the results. 10. Set Kp to half position and record the results 11. Set Ki to half position and record the results 12. Set Kd to half position and record the results 13. Change the values of Kp, Ki and Kd until he system will become stable and then discuss the results.

3.5 Tuning the PID controller using computer software: 1- Remove All connections that connected above except necessary supplies to the module. 2- Turn on the computer software (Visual Designer). 3-In Visual Designer open the file G13 PID CONTROLLER. 4- Press to connect icon and follow the instructions that written into it. 5- Turn on the power supply and Run the program 6- change the values of Kp,Ki,Kd until the response will become stable. 7- Record best values of Kp , Ki ,Kd. And take the result after and before.


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Level Pressure Transducer Temperature And control (G30A and Transducer and Control G30B)

(G34)


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1. Introduction: Temperature is one of the indicators which represent the state of the system. The unit of temperature used in the International System is the Kelvin (K). In the Kelvin temperature scale, absolute zero corresponds to 0 K. Two other temperature scales are normally used: the Celsius or centigrade scale (°C) and the Fahrenheit scale (°F) the relationship between the centigrade and Kelvin show in the equation: °C = ° K - 273.1 Conversion from Centigrade to Fahrenheit is based on the following equation: °F = 1.8°C +32 The experiments described in this handbook use the Centigrade scale, which is perhaps the most practical of the three, as 0°C corresponds to the temperature of melting ice and 100°C to the boiling-point of water at sea-level. In industrial and domestic applications, temperature is measured by numerous different types of transducers of varying complexity and accuracy. The most commonly used are semiconductor transducers, thermo resistance and thermocouples, as this offer a high degree of accuracy together with simple construction and ease of use. These types of transducers can also be very small, and are therefore easy to insert directly into the process.

1.2. Temperature Transducers: 1.2.1Semiconductor temperature transducer: Semiconductor temperature transducers are based on the high degree of sensitivity of semiconductor materials to temperature. The temperature coefficient of a semiconductor temperature transducer is much higher than that of a thermo resistance, and it is much cheaper to produce. Its main disadvantages lie in a limited temperature range and lower linearity. Devices of this type may have one or two terminals, and are classified as follows: • Semiconductor resistive block • Junction between two semiconductors doped P and N (diodes) • Integrated circuit The first type of devices are the most simple in structural terms, and may have a positive or negative temperature coefficient of approximately 0.7%/°C and linearity of ±0.5% within a temperature range of – 65°C to +200°C. The law by which resistance varies with temperature is, in approximate terms, as follows: RT = RO·(1 + α·T) The transducer and the signal conditioner are generally connected by two wires. As t he temperature to which these wires are subjected varies, the overall resistance of the transducer + wires also varies. However, the measurement error caused by the wires is, in most cases, negligible.

Signal conditioner for semiconductor temperature transducer: Fig. 2.1 shows a detailed circuit diagram relative to the signal conditioner. The function of a signal conditioner in to establish the relationship between temperature variations of 0 to 150°C and an output voltage which can vary from 0 to 8V. Note the presence of the high-stability reference generator. An a three wire transducer is used, a differential amplifier (double-stage with operational amplifiers) is fitted in order to minimize the influence of the resistive value of the transducer wires. The circuit is completed by a temperature signaling device which causes a LED (located on the upper part of the STT conditioner) to Prepared by: Eng. Waleed Abuzaina

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flash when the temperature exceeds 150°C, thus informing the operator that the semiconductor transducer should be removed from the oven. Having decided that the temperature range of 0 to 150°C in to correspond to a voltage variation of 0 to 8V, the proportionality constant given by the relationship between the voltage and t he temperature in as follows: proportionality constant = 53.3 mV/°C

1.2.2 NTC THERMISTORS: Thermistors are resistance variation transducers constructed with materials of high temperature coefficient, and with very cheap manufacturing processes. These temperature sensors, considered semiconductor RTDs (Resistance Temperature Detectors), can determine negative (NTC) or positive (PTC) temperature coefficients, according to their composition. The resistance of NTC thermistors depends on absolute temperature R(T)=R0 exp(b/T) , exponentially; consequently, these detectors are characterized by a considerable nonlinearity, whereas their sensitivity varies inversely with the square of absolute temperature T. They offer ohmic values in a very wide range and being of very small size they can supply very fast responses. PTC thermistors have a constant thermal coefficient in a limited temperature range, showing a fairly good sensitivity.

PTC thermistors have a positive temperature coefficient and their characteristic will i ncrease as temperature rises, whereas NTC thermistors have a negative temperature coefficient and their resistance/temperature characteristic will show a decreasing trend as temperature rises. NTC thermistors can use various circuits to reduce their nonlinearity (e.g.: a resistor bridged with the sensor and another one series connected with it); or using a microprocessor will lead to digital linearization with interpolation of the calibration curve. Resistance and temperature of NTC thermistors will vary according to the following formula: RT = A * e B/T Where: • RT is the resistance of the material at the generic temperature T; • A and B are constants depending on the material with 200K < b < 5500K; • T is the generic temperature expressed in Kelvin degrees. The main relation between resistance of the thermistor R T and temperature T is: B (

− ∗

)

R T = R Ta * e where: • Ta is the reference temperature Ta=293K (Ta=20°C) • R TA is the resistance of the thermistor at the temperature Ta Prepared by: Eng. Waleed Abuzaina

| P a g e 26

• B is a constant depending on the material 200K < B < 5500K

The transducer examined with the module G34/EV shows the following characteristics: • R TA= 12.09 k Ω • B = 3435K ± 1% CONDITIONER FOR NTC THERMISTOR: A signal conditioner will relate the variation of temperature of 0 to 110 °C with an output voltage varying from 0 to 5.863 V. The same scale of the STT sensor is kept: a variation of temperature of 0 to 150 °C wil l lead to an output voltage of 0 to 8 V. The maximum temperature being borne by the NTC thermistors included in this module is 110 °C; when this value of temperature is reached, a circuit will be 13 enabled to indicate that the maximum temperature has been reached; as soon as this temperature is exceeded, the thermistors will be cooled and then it will be removed from the oven to avoid damages to the same sensor. This value sets the upper limit of the temperature range that can be measured with this NTC thermistors, indirectly; consequently, the range is limited to 0 to 110 °C. Factor of proportionality = 53.3 mV/°C However, the factor of proportionality is 53.3 mV/°C, corresponding to a temperature range varying from 0 to 150 °C and to a voltage range of 0 to 8 V, but the actual maximum value of the scale is 5.863 V (53.3 x 110 mV).

3. Exercises: 3.1 close loop control Temperature system with PID controller using NTC transducer and Plotting the characteristic curve of the NTC transducer: 1- Carry out the circuit of the fig 3.1.

Fig 3.1

2- On the PID controller block, turn the PROPORATIONAL knob to the half value, INTEGRATIVE and DERIVATIVE knob to half value. 3- Connect all the necessary supplies to the module. 4- Connect the output of set point to Temperature meter terminal 10. 5- Switch on the power supply. Prepared by: Eng. Waleed Abuzaina

| P a g e 27

6- Detect the ambient temperature use thermometer (Centigrade scale) and change the value of temperature setpoint to the value of ambient temperature using ambient temperature knob. 7- Change the value of the setpoint as shown in table1 by the knob. 8- Measured the value of the error from output of error amplifier (use Multimeter) and V output from output of signal condition (use multimeter). 9- Fill the result in table 1. Table 1 Setpoint (°C) Error (volt) V output Ideal V output (volt) (volt) 30 40 50 60 70 80 90 100 110 10- Plot a Cartesian graph, where the setpoint is on the x-axis and V output is on the y-axis. 11- Plot another Cartesian graph, where the setpoint is on the x-axis and error is on the y-axis. 12- Measured the ideal value of V output using this equation. V output = Value of setpoint * 53.3mv

3.2Determining the characteristics of the temperature process: 1-Power the logic section of module G34/EV (±12V) 2-Connect the SET-POINT output (jack 2) to the input of the POWER AMPLIFIER block (jack 11). 3-Connect the HEATER and COOLER outputs of the POWER AMPLIEIER block to the corresponding inputs on the TY 34/ EV. 4-Adjust the Set-point potentiometer to the maximum setting (+8V) 5-Connect the power supply (2x24V AC). 6-Fill the table 2 below. 7-Compile the table with the temperature read on the thermometer at regular intervals (e.g. 0.5min) Table2 n° 1 2 3 4 5 6 7 8 9 10 11 12

Time(minute) 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6


T(°C)

n° 13 14 15 16 17 18 19 20 21 22 23 24

Time(minute) 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12

T(°C)

| P a g e 28

8-For the sake of simplicity, it is assumed that the thermal constant of the thermometer is negligible with respect to the thermal constants of the transducers, and that the thermal characteristic measured for the process may therefore be considered as a real time value. 9-Plot the time (in minutes) and the temperature (°C) on a graph. 10-Draw a curve which best approximates the plotted values and determine the rise time of the process.

3.3Determining the time constant of temperature transducers: The purpose of this experiment is to determine the time constant of temperature transducers, which is necessary for the subsequent study of automatic process control systems. 1-Set up the apparatus as described in fig 3.2.

Fig 3.2 2-The purpose is to create a closed-loop control system using the STT, and then to measure the response speed of the silicon transducer by moving it from an area in which the temperature is known and stable into an oven. For the moment remove the silicon transducer from its well so that it remains at ambient temperature. 3-Adjust the Set-point to a temperature of 100°C. 4-Measure the output voltage of the NTC signal conditioner while the temperature of the oven stabilizes at 100°C. 5-Connect the semiconductor transducer to the relative signal conditioner, prepare to measure the voltage on jack 22, and introduce the transducer into the oven.

Time(second) 0 2 4 6 8 10 12 14 16 18 20 22

T(°C)


V output

Table 3 Time(second) 24 26 28 30 32 34 36 38 40 42 44 46

T(°C)

V output

| P a g e 29

6-Measure the temperature indicated by the transducer over a period of ti me, and compile a time/temperature table. 7-Plot these values on a graph and determine the temperature required to bring the transducer to a temperature of 63°C (see fig. 3.3) This measurement delay is referred to as the time constant of the transducer.

fig. 3.3


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Level Pressure Transducer Pressure Transducer and And control (G30A and Control (G35) G30B)


| P a g e 31

1.Inroduction: 1.1Semiconductor Pressure Transducer: The portioning principle of this type of transducer is based on the piezoresistivity (e.g. the property of materials whose resistance change as function of mechanical distortion) of a silicon support. Four resistors, connected as a Wheatstone bridge, are applied to a silicon diaphragm (see fig 1.1).the diaphragm is then soldered to a glass support ring.

Fig 1.1 One diagonal of the bridge is powered by a constant voltage generator; the opposite diagonal carries a voltage which varies proportionally with the pressure exerted on the diaphragm. The transducer used is of the differential type. If one of the ports is left open, the transducer can be used as a differential transducer. The structure of the transducer is shown in fig 1.2.

Fig 1.2

1.1 signal condition for semiconductor pressure transducer: This type of transducer requires a particularly stable signal generator (8V). For t his reason, this type of circuit is fitted to the signal conditioner. The transducer signal is then amplified (which is a simple operation, as this type of device has a high output signal) in order to make the measurement Prepared by: Eng. Waleed Abuzaina

| P a g e 32

signal easier to handle. An offset mulling circuit is then added (repeater block). A further amplifier ensures that the output signal is within the correct range. Here, too, the various circuits are filtered so that the signal conditioner is less susceptible to ambient noise. Fig 1.3 shows the diagram for a signal conditioner and the range of the output signals as a function of the pressure.

Fig 1.3

1.2. Pressure Process: 1.2.1 Description: Refer to fig 2.1, which illustrates the pressure unit supplied with model G35. The unit consists essentially of a process tank and a compressor with an electrical motor. The compressor provides the gas (e.g. air) required to generate and maintain the pressure. The actuator consists of an electrically – controlled proportional valve fitted to the outlet. A pressure transducer fitted on the tank side provides the feedback signal. A pressure gage is fitted on the top of the unit. A manually – operated restrictor valve on the tank side enables the user to vary the pressure load. Fig 2.1 The unit is completed by a safety pressure valve fitted on the derivative line. This valve prevents the pressure in the tank from building up to dangerous levels and blocking the compressor. The TY35 unit can operate with pressure of between 0 and 2 bar. Prepared by: Eng. Waleed Abuzaina

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1.2.2 Automatic Pressure Control: Automatic pressure control systems are widely used in industry. These systems are essentially identical to those used for the automatic control of other physical quantities, such as temperature, velocity, etc. Obviously, the actuator used in pressure control systems is different. In this case, the actuator is a proportional.

2. Exercises: 2.1 Measuring the characteristic curve of the pressure transducer: The purpose of this experiment is to determine the characteristic curve of transducer/signal conditioner used to measure relative pressure.

Procedure: 1- Connect all necessary supply to module. 2- Connect the output of the setpoint to the input of the power amplifier. 3- Switch the power on. 4- Adjust the setpoint so that the pressure inside the tank rises gradually, and measure the output voltage of the conditioner block. 5- List the increasing pressure levels and the corresponding output voltages of the conditioner blocks in a table 1. 6- Plot a graph with the pressure on the x-axis and the corresponding output voltage on the y-axis. Table 1 Pressure (bar) V output (volt) 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2

2.2 Close loop control system with P controller: 1- Carry out the circuit of the fig 3.1. 2- On the PID controller block, turn the PROPORATIONAL knob to the half value. 3- Connect all the necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table2 by the knob, and use multimeter to check the value.


| P a g e 34

Fig 3.1 6- Measured the value of the error from output of error amplifier (use Multimeter) and pressure from pressure gage. 7- Fill the result in table 2. Table 2 Setpoint Error Pressure (volt) (volt) (bar) 0 2 4 6 8

2.3 Close loop control system with PI controller: 1- Carry out the circuit of the fig 3.2. 2- On the PID controller block, turn the PROPORATIONAL knob to the half value and connect the capacitor of integrative action to R7. 3- Connect all the necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table3 by the knob, and use multimeter to check the value.

Fig 3.2 6- Measured the value of the error from output of error amplifier (use Multimeter) and pressure from pressure gage. 7- Fill the result in table 3. Prepared by: Eng. Waleed Abuzaina

| P a g e 35

Setpoint (volt) 0 2 4 6 8


Pressure (bar)

2.4 Close loop control system with PID controller: 1- Carry out the circuit of the fig 3.3. 2- On the PID controller block, turn the PROPORATIONAL knob to the half value and connect the all capacitors of integrative action and derivative action to R7. 3- Connect all the necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table4 by the knob, and use multimeter to check the value.

Fig 3.3 6- Measured the value of the error from output of error amplifier (use Multimeter) and pressure from pressure gage. 7- Fill the result in table 4. Table 4 Setpoint Error Pressure (volt) (volt) (bar) 0 2 4 6 8

2.5 Compare between 3 controllers: Plot Cartesian graph that contain the result above in sections 2.2, 2.3, 2.4 where the setpoint is on the x-axis and error is on the y-axis.


| P a g e 36

2.6 Tuning the PID controller using computer software: 1- Remove All connections that connected above except necessary supplies to the module. 2- Turn on the computer software (Visual Designer). 3-In Visual Designer open the file G35 PID CONTROLLER. 4- Press to connect icon and follow the instructions that written into it. 5- Turn on the power supply and Run the program 6- change the values of K p ,K ,K i d until the response will become stable. 7- Record best values of K p , K i ,K d d. And take the result after and before.


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Level Pressure Transducer Speed and Position And control (G30A and Transducer and Control G30B)

(G36A)


| P a g e 38

1. Description of the module: Module G36A consist consist of a front panel panel with test- point and silk silk screen printed printed electrical circuit circuit diagram, divided into blocks forming the control chain. Fig. 1.1 represents the modules silk screen printed diagram. You can easily see that there are ten blocks with ten electrical circuits, plus a part (the one at the extreme right) for the connection of the module to the external unit TY36A. These electrical circuits have a precise function inside the whole circuit and this explains why they t hey have been schematically separated. The terminals for the connections to the different power voltages are fitted in the upper right part : a voltage +12V ,and a voltage -12V are an necessary for the control section and a voltage +30V for the power section . Fig 1.1

On the right side of the module there are two terminals (a red one and a black one) for the connection between the module G36A and the motor of the external unit TY36 and an 8poles socket for the connector connector of the signal coming coming from the transducer transducer of the external external unit. The external unit TY36 consist of a permanent magnet DC motor, on whole axis a tachogenerator and disc with transparent / opaque radial sectors are fitted, so that it can be used as speed "photoelectric transducer" transducer" when connected to a photo transmitter /photo receiver, Prepared by: Eng. Waleed Abuzaina

| P a g e 39

while on the other side there is a motor reducer which permits a strong drop of the rotating angular speed, a display system of the angular position and a potentiometer for detection of the same position.

2. Angular Speed and Position Transducer: 2.1Speed Transducer: The strong motorization of industrial machines, have determined the parallel development of angular speed transducer. The international unit of measurement for angular speed is the radian per second [rad/sec], but the used of the revolution per minute [r.p.m] is also available, where one revolution corresponds to any 2.Π radian. The most used transducers for this variable are the following: 1- Tachogenerator. 2- A.C. Tachogenerator. 3- Digital Transducer. The main difference between the first couple is in the supplied wave form, which is continuous in the first type and alternating in the second, both with amplitude variable with speed. The A.C. tachogenerator has no commutator and so it requires less maintenance, but has the strong defect of needing a rectifier / leveler unit at the output. This is the reason why, at the moment the tachogenerator is the most used in industry. As far as concerns digital transducers, they are very simple and economic to construct, but they supply a pulse output (ON/OFF type) which cannot be directly used in close loop analog controls and requires, consequently , signal conditioners which can be quite complex. They are commonly used for their high precision. In case of D.C. electric motors, the armature feedback of the same motor, is often used as the counter electromotive force developed is directly proportional to the rotating speed. Following, the detailed analysis of the D.C. motor tachogenerators, digital transducers and armature feedback, which are the transducers available on module G36A.

2.1.1 Tachogenerator: The diagram of a standard tachogenerator is represented in fig 2.1. A U-type permanent magnet, whose polar expansions face each others, creates a magnetic field. In order to understand its operation let's consider a coil with angular speed rotation = ω. this coil is influenced by a flow variable according to the following relation: Ө = Өo.cos (ωt). And so the voltage across the coil is: E = -dӨ/dt = Өoωsin(ωt) Whose max. Value is proportional to the angular speed. Fig 2.1 Actually, a tachogenerator consist of stator, on which a permanent magnet is inserted and of rotor, on which N turns are wound, speed among each other by an angle of 2Π/Nω.


| P a g e 40

Fig 2.2 represents two shapes of the output voltage at angular speed variations. Note that the amplitude as well as the ripple is functions of ω.

Fig 2.2 An A.C. component, with frequency proportional to ω and amplitude inversely proportional to Nω, is generated together with D.C. component (proportional to ω). This A.C. component is an error, called ripple, which is usually very small in respect to the output voltage. The used tachogenerator has the following characteristics: No. of poles = 2 Tacho constant =3 mV/rpm Max. Current = 30mA

2.1.2 Armature Feedback: Consider the following relation which gives N = rotation speed (rpm) pf a DC motor as function of Va = voltage armature, of Ia = armature current, of Ra = armature resistance and Kφ =magnetic constant; =

 

=

∗ 

Where E is the electromotive force. If  is kept constant (as obtained in DC motor speed controls acting only on the armature current = Ia ) we must get Ra*Ia and subtract it from the Va, in order to determine N. These operations are performed by the signal conditioner for armature feedback which, in module G36, is fitted in the block called speed detector. Prepared by: Eng. Waleed Abuzaina

| P a g e 41

2.1.3 Digital speed Transducer: This definition includes all transducer that generates pulse outputs with frequency variable with speed. Pulses are usually sent to counters which, if the measurement in carried out in a due time, give the value of the speed directly in rpm. Photoelectric transducers, based on masked or perforated disk system or on reflection system, are the most popular digital speed transducers. The first type essentially consists in a disk, which is made to rotate on the axis of which we must know the angular speed show fig 2.3. The disk rotation produces a shuttering effect on the track of the light source to the light sensor, so that there is pulse corresponding to each hole Fig 2.3 or to each section. It is necessary to increase the number of holes (or of the sections) in order to obtain accurate system, especially at low speeds. The reflection photoelectric transducer uses a transmitter and a receiver separately. A mask with reflecting and opaque segments is uses instead of the perforated disk. When the light emitted from the transmitter tracks a reflecting surface is sent back to the receiver show fig 2.4.

Fig 2.4 The advantage of using this system is that it is sufficient to apply reflecting masks on the moving part, instead of using a special disk. Module G36A uses a transparent disk on which 3 not transparent black zones are applied. The uses emitter/photo transistor diode operates in the infrared range.


| P a g e 42

2.2 Position Transducer: The position transducers are used to detect the position of the movement of an object from a reference point. The movements can be linear or angular; consequently linear or angular transducers have been carried out according to the type movement.

2.2.1 Potentiometeric transducer: The Potentiometeric angular position transducer is at the same time very simple and accurate enough. It consists in a resistive potentiometer whose shaft is mechanically connected to the motor axis. The two terminals of the resistor which are the electrical part of the potentiometer, are connected to the two reference voltage (±8). Movements of the motor shaft make the position of the potentiometers cursor vary and consequently of the motor shaft can be detected from the voltage value obtained.

3. Angular Position and Speed Process: Ref. to fig3.1, showing the angular position and speed process unit supplied with module G36A (unit TY36A). it consist of permanent magnet, bidirectional DC motor with function of process actuator. There is a tachogenerator fitted on the motor shaft, and an alternating opaque and translucent disk, which, together with a U-shape photo coupler, constitutes an incremental encoder. On the other side, a motor reducer which reduces the speed a factor 50 is also mounted on the motor shaft: this means that a turn of the shaft toward the motor reducer is equal to 50 on the tachogenerator side. The shaft of the motor reducer controls the red pointer which is on the graduated scale. The position of the motor reducer shaft is transmitted to the potentiometer (which is the position transducer) through two gear wheels which ratio is 1:2. So, the ±180° shifting of the motor reducer produces a ±90° shifting on the potentiometer.

Fig 3.1 Prepared by: Eng. Waleed Abuzaina

| P a g e 43

The potentiometer has the characteristic of continuous rotation without damaging: this allow its connection during speed exercise where the motor rotates with continuity. The unit consist also of mechanical brake (which can be controlled from the side knob) to apply variable loads to the motor. The range of the angular speed process is: Range: -4000 – 4000 rpm. The range of the angular position process is: Range: 0° - 360°.

3.1 Speed process control: The speed process control supplied with module G36A is shown in the block diagram of fig 3.2.

Fig 3.2 The main elements of speed control are: 1-Set point: the set point block supplies the input signal for the whole circuit. 2-Error amplifier: is the block which compares the input value (set point) with the obtained output value. 3-PID controller: PID type which can be configurated in different ways: the three actions (proportional, integrative and derivative) can be controlled and inserted separately. 4-Current limit: That used to limit the maximum current across the motor. 5-PWM (Pulse Width Modulation): It consists of an H-Bridge made with 4 power MOS-FETS. The H-bridge permits bi directional operation. The power supplied to the motor is measured with the PWM system, which generates an output square wave whose duty cycle (ratio between the period in which the voltage is high and the one when it is low) depend on the comparison between a saw-tooth signal and variable signal according to the output value. 6-Power amplifier: It used to amplification the signal that out from t he PID and this signal inter to actuator.


| P a g e 44

3.2 control of the position process: The position process control of the module G36A shown in the block diagram of fig3.3.it is composed of the some blocks analyzed before in the speed process, but also of the following ones: Error amplifier 2: it has an analogous function to the Error amplifier .1, potentiometer position transducer seen before.

Fig 3.3


| P a g e 45

4. Exercises: 4.1Ploating of the characteristic curve of the Tacho-Generator: 1- Carry out the circuit of the fig 4.1.

Fig4.1 2- On the PID controller block, turn the PROPORATIONAL knob to the max. value. 3- Connect all the necessary supplies to the module. 4-Set the multimeter for D.C. voltage measurement and insert it between terminal 22 and ground. 5- Switch on the power supply. 6- Turn the set point knob completely clock wise. 7- Act on the knob of the tacho-genertor conditioner block until the display of the digital RPM meter reaches 4000 RPM. 8- Acting on the set point knob, set the speed value written on table 1, appearing on the 4-digit display of the photo electric transducer (digital RPM meter). 9- With a multimeter, measure the voltage supplied by the tacho-generator across each of the set values. 10- Fill table1 with the measured voltage values of the tacho-generator at each set speed. 11- Plot a Cartesian graph, where speed is on the x-axis and voltage is on the y-axis. Table 1 Speed 0 500 1000 1500 2000 2500 3000 3500


V output

| P a g e 46

4.2Ploating of the characteristic curve of the DC motor Armature Feedback: 1- Carry out the circuit of the fig 4.2. 2- On the PID controller block, turn the PROPORATIONAL knob to the max. value. 3- Connect all the necessary supplies to the module. 4- Set the multimeter for D.C. voltage measurement and insert it between terminal 24 and ground. 5- Switch on the power supply. 6- Acting on the set point knob, set the speed value written on table 2, appearing on the 4-digit display of the photo electric transducer (digital RPM meter). 7- With a multimeter, measure the voltage supplied by the speed detector at each of the set values. 8- Fill table2 with the measured voltage values of speed detector at each set speed. 9- Plot a Cartesian graph, where speed is on the x-axis and voltage is on the y-axis.

Fig 4.2 Table 2 Speed 0 500 1000 1500 2000 2500 3000 3500

V output

4.3Ploating of the characteristic curve of the Potentiometeric transducer: 1- Carry out the circuit of the fig 4.3. 2- On the PID controller block, turn the PROPORATIONAL and INTEGRATIVE knob to the max value. 3- Connect all the necessary supplies to the module. 4- Set the multimeter for D.C. voltage measurement and insert it between terminal 21 and ground. 5- Switch on the power supply. 6- Turn completely anti-clockwise the set point knob. Prepared by: Eng. Waleed Abuzaina | P a g e 47

7- Acting on the set point knob, set the angular position value written on table 3and display by the pointer indicator of unit TY36A. 8- With a multimeter, measure the voltage supplied by the Potentiometeric transducer /signal conditioner unit corresponding to each set value. 9- Fill table3 with the measured voltage values of the potentiometer at each set angular speed. 10- Plot a Cartesian graph, where the angular position is on the x-axis and voltage is on the y-axis.

Fig 4.3 Table 3 Angular Position V output 30 60 90 120 150 180 210 240 270 300 330 360

4.4Close loop automatic speed control with P controller: 1- Carry out the circuit of the fig 4.4. 2- Tack the PROPORATION knob to the max value. 3- Connect all necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table4 by the knob, and use multimeter to check the value. 6- Measured the value of the error from output of error amplifier (use Multimeter) and speed from 4 digit display. Prepared by: Eng. Waleed Abuzaina

| P a g e 48

7- Fill the result in table 4. 8- Plot Cartesian graph, where setpoint at x- axis and speed at y – axis.

Fig 4.4

Setpoint (volt) 0 1 2 3 4 5 6 7 8


Speed (RPM)

4.5Close loop automatic speed control with PID controller: 1- Carry out the circuit of the fig 4.5. 2- Tack the PROPORATION and INTEGRATIVE and DERIVATIVE knob to the max value. 3- Connect all necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table5 by the knob, and use multimeter to check the value. 6- Measured the value of the error from output of error amplifier (use Multimeter) and speed from 4 digit display. 7- Fill the result in table 5. 8- Plot Cartesian graph, where setpoint at x- axis and speed at y – axis.


| P a g e 49

9- Plot a Cartesian graph, where the setpoint on the x-axis and error on the y-axis for part 4.4 and 4.5.and compare between 2 curves which curve has a small error.

Fig 4.5

Setpoint (volt) 0 1 2 3 4 5 6 7 8


Speed (RPM)

4.6Close loop automatic position control with P controller: 1- Carry out the circuit of the fig 4.6. 2- Tack the PROPORATION knob to the max value. 3- Connect all necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table6 by the knob, and use multimeter to check the value. 6- Measured the value of the error from output of error amplifier (use Multimeter) and angular position from Graduation. 7- Fill the result in table 6. 8- Plot Cartesian graph, where setpoint at x- axis and angular position at y – axis.


| P a g e 50

Fig 4.6

Setpoint (Volt) -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8

Table 6 Error (Volt)

Angular position (degree)

4.7Close loop automatic position control with PID controller: 1- Carry out the circuit of the fig 4.7. 2- Tack the PROPORATION and INTEGRATIVE and DERIVATIVE knob to the max value. 3- Connect all necessary supplies to the module. 4- Switch on the power supply. 5- Change the value of the setpoint as shown in table7 by the knob, and use multimeter to check the value. 6- Measured the value of the error from output of error amplifier (use Multimeter) and angular position from Graduation. 7- Fill the result in table7. 8- Plot Cartesian graph, where setpoint at x- axis and angular position at y – axis. Prepared by: Eng. Waleed Abuzaina

| P a g e 51

9- Plot a Cartesian graph, where the setpoint on the x-axis and error on the y-axis for part 4.6 and 4.7.and compare between 2 curves which curve have small error.

Fig 4.7

Setpoint (Volt) -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8


Table 7 Error (Volt)

Angular position (degree)

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Level Pressure Transducer 3-Phase Induction Motor And control (G30A and speed control (G37) G30B)


| P a g e 53

1. Description of the module: Module G37, together with the external unit TY37, enables the experimental study of servomechanisms for 3-phase asynchronous motors. It consists in a silk- screen panel including the diagrams of each single block composing the whole circuit, the connections among the different blocks and the test points. Fig 1.1 shows the silk screen diagram module. As you can easily see, there are 7 blocks including the same number of electrical circuit plus a part (to the extreme right) dedicated to the connection between the module and the external unit TY37. These electrical circuits develop precise jobs inside the whole circuit and so they have been schematically separated.

Fig 1.1


| P a g e 54

2. The Asynchronous motor: This section analysis the parameters characteristic the asynchronous motor and related servomechanism.

2.1 Parameters which characterize the servomechanism of machine: The main variables characterizing the servomechanism of machine are: 1-The Torque (T) which can be : Resistant, Acceleration, starting or run, braking 2-The speed (ω). 3-The power (P) Among the last variables there is a link given by: P = T . ω The definition of the last variables can be expressed the machine. Torque: effort performed by the motor to action ate the machine. The torque can be: -Resistant (Tr) : the one the machine opposes to the motion. -Acceleration (Tacc): the one necessary to take the machine to the wished speed in the wished time. -Starting (Tavv): it is determined by the resistant torque and the acceleration torque: Tavv = Tr + Tacc. Speed: it is the rotation one of the motor shafts expresse d in rev/min (n) or in rad/sec (ω). ω (rad/sec) = n(rev/min)2Π/60 Power: it is expressed by the relation:

P = T. ω With P in watt, T in N.m, ω in rad/sec Suppose to consider as negative speed those which rotation direction is opposed to the one for which the speed is positive, then the diagram of fig 2.1 can be carried out.

Fig 2.1 In frames 1 and 3 there is positive power corresponding to an operation as "motor"; in this case the energy is supplied by the power supply network. Prepared by: Eng. Waleed Abuzaina

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In frames 2 and 4 there is negative power corresponding to an operation as "generator"; in this case the energy is supplied by the load.

2.2 The asynchronous motor and the speed variation: The asynchronous motor is composed by: -Stator: powered in 3-phase system, it generates a rotating field which speed is defined by synchronism speed. - Rotor: it is never powered and only in the case of the ring motor it is wired. In the squirrel cage motor, the rotor consists of conductive bars connected on two rings so to create a cage. This case today is usually obtained by pressure die-casting. The squirrel cage asynchronous motor is among the most used electrical machines because it is the simpler and the less expensive. The speed of a 3 – phase asynchronous motor is expressed by relation: n=

60 

(1- s) with s =

− 

. 100

where: n = nominal speed of the motor in rev/min. ns = synchronous speed. nr = rotational speed. f = frequency at which the stator is powered. s = normalized slip (0 to 1).

Fig 2.2: Mechanical Characteristic.

2.3 Waveform of the voltage supplied by the servomechanism: Fig 2.3 shows the electrical diagram of typical transistor bridge used in the inverters. In graph of figure 2.4 T1, T 2… T6 represent the sequence with which the transistors of the inverters stage of fig 2.3 are taken into conduction. V1 is the voltage concatenated on the output by a phase of the frequency converter and which results from a combination of the last graphs.


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Fig 2.2

Fig 2.3

2.4 Inverter drive:

The Inverter drive (variable frequency drive) controller is a solid state power electronics conversion system consisting of three distinct sub-systems: a rectifier bridge converter, a direct Prepared by: Eng. Waleed Abuzaina

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current (DC) link, and an inverter. Voltage-source inverter (VSI) drives are by far the most common type of drives. Most drives are AC-AC drives in that they convert AC line input to AC inverter output. However, in some applications such as common DC bus or solar applications, drives are configured as DC-AC drives. The most basic rectifier converter for the VSI drive is configured as a three-phase, six-pulse, full-wave diode bridge. In a VSI drive, the DC link consists of a capacitor which smooth out the converter's DC output ripple and provides a stiff input to the inverter. This filtered DC voltage is converted to quasi -sinusoidal AC voltage output using the inverter's active switching elements. VSI drives provide higher power factor and lower harmonic distortion than phase-controlled current-source inverter (CSI) and load-commutated inverter (LCI) drives. The drive controller can also be configured as a phase converter having single-phase converter input and three-phase inverter output. Controller advances have exploited dramatic increases in the voltage and current ratings and switching frequency of solid state power devices over the past six decades. Introduced in 1983, the insulated-gate bipolar transistor ( IGBT ) has in the past two decades come to dominate VFDs as an inverter switching device. In variable-torque applications suited for Volts per Hertz (V/Hz) drive control, AC motor characteristics require that the voltage magnitude of the inverter's output to the motor be adjusted to match the required load torque in a linear V/Hz relationship. For example, for 460 volt, 60 Hz motors this linear V/Hz relationship is 460/60 = 7.67 V/Hz. While suitable in wide ranging applications, V/Hz control is sub-optimal in high performance applications involving low speed or demanding, dynamic speed regulation, positioning and reversing load requirements. Some V/Hz control drives can also operate in quadratic V/Hz mode or can even be programmed to suit special multi-point V/Hz paths. The two other drive control platforms, vector control and direct torque control (DTC), adjust the motor voltage magnitude, angle from reference and frequency such as to precisely control the motor's magnetic flux and mechanical torque.

3. Exercises: 3.1 Ratio between the output voltages of the SPEED REGULATOR block and output frequency of V/F1 FCT: 1- Connect terminal 3 to 4 and 29 to 30 with cable. 2- Switch I1 to STOP, I2 to 50Hz, and the ACC and DEC potentiometers to the min value. 3- Power the module with necessary voltages. 4- Turn I1 to START. 5- With P1, take the voltage of terminal 38 to 0.5V. 6- With the multimeter, measure the frequency of terminal 17(output of the voltage to frequency converter VF1) and terminal 11 which is the signal driving the MOSFET. 7- Fill table 1 with the obtained measurements. 8- Report the values of the table on graph and check the linearity of the output signals of terminals 17 and11.


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Voltage terminal 38(volt) 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Table 1 Frequency terminal 17 (Hz)

Frequency terminal 11 (Hz)

3.2 Ratio between the output voltage of the SPEED REGULATOR block and the output frequency of V/F2 VCT: 1- Connect terminal 3 to 4 and 29 to 30 with cable. 2- Switch I1 to STOP, I2 to 50Hz, and the ACC and DEC potentiometers to the min value. 3- Power the module with necessary voltages. 4- Turn I1 to START. 5- With P1, take the voltage of terminal 38 to 0.5V. 6- With the multimeter, measure the voltage of terminal 20 and terminal 19 (output of the voltage to frequency converter VF2). 7- Fill table 2 with the obtained measurements. 8- Report the values of the table on graph and check the variations of the output frequency of V/F.

Voltage terminal 38(volt) 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Table 2 Frequency terminal 19 (Hz)

Voltage terminal 20 (volt)

3.3 Check the linearity between speed command and obtained speed: 1- Connect terminal 3 to 4 and 29 to 30 with cable. 2- Switch I1 to STOP, I2 to 50Hz, and the ACC and DEC potentiometers to the min value. 3- Power the module with necessary voltages. 4- Turn I1 to START. 5- With P1, take the voltage of terminal 38 to 0.5V. 6- Fill the result in table 3. Prepared by: Eng. Waleed Abuzaina

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7- Report the values of the table on graph and check the linearity between value set with P1 and reach speed. Table 3 Voltage Speed terminal 38(volt) (RPM) 0.5 1 1.5 2 2.5 3 3.5 4 4.5

3.4 Check the effect of variable voltage on variable frequency and speed: 1- Connect terminal 3 to 4 and 29 to 30 with cable. 2- Switch I1 to STOP, I2 to 50Hz, and the ACC and DEC potentiometers to the min value. 3- Power the module with necessary voltages. 4- Turn I1 to START. 5- With P1, take the voltage of terminal 38 to 1V. 6- Connect the oscilloscope between terminal 9 and ground and save the picture in flash memory. 6- Fill the result in table 4. 7- Compare between the results and explain how the voltage effect on frequency and speed. Table 4 Voltage Picture no. you terminal 38(volt) take 1.0 1.5 2.0 2.5 3 3.5 4.0


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Level Pressure Transducer PWM Speed Regulator And control (G30A and of a DCG30B) Motor (G14)


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1. Introduction: This unit is an example of the application of PWM techniques in the control of separate – excitation DC motors. As well as the PWM amplifier, the unit includes a closed loop control system for control of both speed and current. The motor is fitted with an adjustable mechanical brake, which facilitates the execution of tests and experiments under various load conditions. The first part of this manual introduces the static and dynamic characteristic of a DC motor; then the PWM technique is examined, with a detailed description of the circuit featured by this unit. This is followed by a description of the different close loop control techniques and an analysis of the control stability.

1.1 Separate excitation DC motor: The DC motor consists of a rotor which rotates within the magnetic field generated by the stator. When the rotor turns around at an angular velocity ω it produces an e.m.f. (electromotive force ); the value of the e.m.f. is :

e =K E . ω = K e.φ.ω Where: K E is a constant (voltage constant) depending on the inductor magnetic flux φ and the characteristic of the rotor winding; Ke depends only on the characteristics of the winding. When a torque T is applied to the motor, the motor absorbs current. In condition of equilibrium:

T = K T . ia = Kc φ ia Where: K T is a constant (torque constant) depending on the indicator magnet flux φ and the characteristics of the rotor winding, while Kc depends on the characteristics of the winding only. It is know that mechanical power is the product of torque and the angular velocity:

P = T . ω = K T . ia

 

=

 

. e. ia

If no losses occur, the input power is equal to the output power; therefore K E = K T , the voltage and torque constants are equal and therefore Ke = Kc.

1.2 Equivalent circuit on the DC motor: The equivalent circuit of the DC motor is shown in fig 1.1.

Fig 1.1


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Where: Ra = armature resistance. La = armature inductance. I F = excitation circuit current. E = armature e.m.f. (electric motive force) V = armature voltage. In steady- state, the equations of the motor armature circuit are: V = E + Ra Ia E= V – Ra Ia Therefore:

ω=

 

=

−  

1.3 External characteristics of the motor: Fig 1.2 shows the behavior of ω according to the variation of the armature current. It may be noted that the speed decreases as I a increase; this is due mainly to the armature resistance. It must be remembered that the speed drop is lower than that which would occur with drop R a . I a only. This is because the rotor current decreases the magnetic flux of the stator (armature reaction). Therefore, as the magnetic flux

φ depends on constant K e and remembering that ω =

−  

The effect is a partia l compensation of the decrease of ω caused by R a . I a. Fig 1.3 shows the characteristic torque T versus current Ia which, as T =K t . ia, is straight line. If the effect of the inductance reaction is consider, the resulting curve is shown by the dotted line.

Fig 1.2


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Fig 1.3

2. PWM (Pulse Width Modulation): 2.1PWM Regulator: In PWM regulators, power control is carried out b a transistor which operates as a switch at suitably high frequency (see fig 2.1). The power is regulated by varying the ON and OFF time of the transistor.

Fig 2.1 The power transistor therefore operates in saturation or in cut-off; the dissipated power will thus be very little. In this type of operation, the transistor can be shown as a switch which is closed or opened at fixed frequency (see fig 2.2).


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The load L will be powered by the entire voltage Va for the time period T on during which I is closed, while it will not be powered for time period T off is equal to the period of the squari driver wave. The power supplied to load L is proportional to the ratio T on / T. This ratio is the duty cycle which gives: Pu = Pmax T on /T = Pmax .DUTY CYCLE In which: Pmax is the power absorbed by the load if it is powered at a voltage of Va.

Fig 2.2

2.2Voltage and current in PWM system: In the case of a pure resistive load (R L), measurement of the voltage at the load terminals using average value and effective value voltmeters will give two different results. If the duty cycle is referred to as D.C.:

And since: V m = V a D.C.


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Therefore

As D.C. is always < 1, the average voltage is lower than the effective voltage. As the load resistive, the same considerations also apply to the current. The power on the load (except the losses) can also be measured using a standard voltmeter and ammeter. Connected as shown in fig 2.3. This gives:

Fig 2.3

3. Exercises: 3.1 Measurement of the open loop speed: 1- Connect point 1 to 18 and 22 to23. 2- Connect all necessary supplies to the module. 3- Switch on the power supply. 4- Connect the voltmeter between terminal 1 and ground and change the value of setpoint from 1-8 volt. Prepared by: Eng. Waleed Abuzaina

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5- Use multimeter to take the value of the output voltage from transducer, after that use the relationship between voltage and speed to detect the speed of the motor. 6- Fill the result in table 1.

Setpoint (volt) 1

Table 1 Voutput (volt)

Speed (RPM)

2 3 4 5 6 7 8

3.2 Voltage duty – cycle speed curve of the PWM regulator: 1- Connect point 1 to 18 and 22 to 23. 2- Connect the oscilloscope to the output of the PWM regulator (point20). 3- Connect the voltmeter between terminal 1 and ground. 4- Switch on the power supply. 5- Vary P1 from zero to +8V. 6- Take the time diagram of duty cycle from oscilloscope use flash memory. 7- Fill the result in table 2. 8- Measure the time of cycle (Ton + Toff) using the oscilloscope. 9- Calculate the duty cycle. Table 2 Set point Name of picture from T cycle (sec) (volt) oscilloscope Ton Toff 0 1 2 3 4 5 6 7 8


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3.3 Measurement of the closed loop speed: 1- Connect the instrument to the terminals on the panel and connect between terminal 22 and 23. 2- Carry out of the block diagram of the fig 3.1.

Fig 3.1 3- Switch on the power supply. 4- Change the value of the setpoint as shown in table 3 by the knob, and use the multimeter to check the value. 5- Use multimeter to take the value of the output voltage from transducer, after that use the relationship between voltage and speed to detect the speed of the motor. 5- Fill the result in table3. 6- Measured the speed of motor from the relationship between volt and speed (0- 8) volt → (0 – 3500)rpm. 7- Compare between close loop and open loop speed system.

Setpoint (volt) 0 1 2 3 4 5 6 7 8


Table 3 Voutput (volt)

Speed (rpm)

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Level Pressure Transducer Stepper Motor control And control (G30A and (G16) G30B)


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1. Introduction: A stepping motor translates digital information into proportional mechanical movement; it is an electromechanical device whose shaft rotates at discrete steps, thus following the control pulses for number and speed. Its simplicity of use, due to the fact that it does not need feedback, the precision and the positioning rapidity determine its large diffusion above all for the following applications: 1- Computer terminals such as printers, punch-readers, plotters …etc. 2- Machine tools. 3- Movie devices for transferring films and opening lens. 4- Medical device. 5- Industrial automation (textile, pharmaceutical and electronic industrial. 6- Office machine. 7- Measure instrument. The diffusion of stepping motors is linked to the fortune that digital and microprocessor controls have met in these last years.

2. Operation principles: The position of the shaft of a stepping motor depends the relation between number of stator poles and rotor. Since the rotor is a permanent magnet, its poles are fixing. On the contrary, the stator is constituted by several winding and its poles are determined by the current circulating into its windings. Powering the windings one by one, we create a magnetic rotating field which is followed by the rotor. The rotating speed is determined by the speed which the winding are switched with, and by the rotation direction of the switching sequence. There are two driving methods for stepping motors according to the way to reverse the current in their windings: unipolar and bipolar driving.

on

The description if facilitated by a 2-poles stepping motor (remember that these motors can have more than two poles; e.g. 24).


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2.1 Unipolar driving: Connect ends A1, A2, B1, B2 to the common point of a current generator and switch the current on the other ends according to the diagram of fig 2.1.

Fig 2.1 Note that the sequence repeats each 4 time intervals. During these 4 intervals, the rotor positions are those of fig 2.2

Note that the rotor fully rotates every 4 intervals. This is a wave unipolar driving, the term "unipolar" refers to the fact that current crosses the windings in one direction only, fig 2.3 shows a 2-phase driving.


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Fig Even here the rotor rotation defines in 4 steps (see fig 2.4).

Fig 2.4 With respect to the previous case, per each interval, 2 windings are interested and, then, torque is higher, thus increasing dissipated power. If the windings of the stepping motor powered according to the sequence of the wave driving, after each step, which is after each passage from a balancing position to the other, rotor and stator poles are aligned. On the contrary, in the 2 – phase driving, rotor poles set between the two poles of the stator. So, alternating the two driving systems, we have the half – step operation see fig 2.5.


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Fig 2.5 Fig 2.6 shows the rotor balancing position. Half – step driving is applied whenever it is necessary to reduce resonance during motor operation. Due to the inertia of the rotor and of it s load, at each step, the rotor oscillates around its balancing point. Above a certain operation frequency, which depends on motor characteristics and load, such is the oscillation amplitude that the rotor is not able to reach its balancing position before the following step arrives. In this case, motor loses the step.

Fig 2.6 Prepared by: Eng. Waleed Abuzaina

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2.2 Bipolar driving: Using the 2 – phase driving, operation characteristic are improved with respect to those of a wave operation because two windings on four, instead of one four are interested at the same time. A further improvement is obtained interesting all four windings. This is possible with a bipolar driving which sends alternatively current in the two winding directions. Fig 2.7 shows the current diagram for a 2- phase bipolar driving.

Fig 2.7

Connect the circuit as in fig 2.8

Fig 2.8


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Fig 2.9 shows the rotor positions.

Fig 2.9 The half – step bipolar driving keeps the same parallel connection of the windings, but currents must respect the diagram of fig 2.10.

Fig 2.10

Fig 2.11 shows the rotation positions.


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Control Lab

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