control of temperature system 2

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University of Jordan

Faculty of Engineering and Technology

Mechatronics Engineering Department

Measurements and Control Lab (EE 448)

Experiment no. 3

Control of Temperature SystemPrepared by: Eng. Rasha Noufal


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Experiments No. 2 Control of Temperature System

Measurement and Control Lab Page 2

Control of Temperature SystemObjectivesIn this experiment, the students will learn the basic operation of a temperaturecontrolled system and will also learn the static and transient behaviour of thetemperature process.

Following are the objectives of the experiment:- Study the effect of flap, ventilator-motor, and input power over the

temperature output.- Evaluation of the step response of the temperature process.- Find the transfer function of the temperature process.- Design a suitable PID controller for the system.

Introduction:The objective of any automation is to be able to efficiently and reliably controlthe behaviour ofthe process. Temperature systems are widely used in real life asin industrial applications, domestic domain (home, office), medical andbiological process engineering The basic operation of a temperature-controlledsystem is analyzed in this experiment.Further, we should understand the system and determine the mathematicalmodel of the process (Transfer function). This transfer function is used todesign a PID controller that improves the performance of the system in closedloop.

Components and Equipments:1 Refererence variable generator 73402

1 Power amplifier 734131 Power Supply +/- 15 V 726861 Temperature controlled system 734121 Two position controller 734011 P controller 734031 I controller 734041 D controller 734051 CASSY-interface with Compute

Set of bridging plug.Cassy lab software


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1-Reference variable generator 73402

Description/functionIf switch S1 (1) is in the lower position, the following signalmay be tapped at output (2):

1. with a bridging plug connected to (3): 10 V to + 10 V2. with a bridging plug connect to (7): 0 V to + 10 V

If switch S1 (1) is in the upper position, a reference voltage orreference variable may be connected to input (6).

If connections (5) and (7) are plugged in, then positive stepchanges from 0 V to the set end value are generated by the switch (1).Positive or negative outgoing step functions can be suppliedwith connection (5) and (3).

The voltage value is determined by the setting of the referencevariable generator (4). Output (2) is buffered.

Technical dataPower supply: 15 V

Input and output signal range: 10 V

2-Stabilized power supply 15 V/3 A 72686Read the instruction sheet carefully before putting the device into operation!

Safety instructions- Never connect an external voltage source to the sockets.- Switch off the device when replacing the mains fuse.- This device may only be operated in the upright position in the panel

frame provided for its operation (cooling).- If you assume that safe operation is no longer possible (e.g. in the case

of visibledamage), then the device must be switched off immediatelyand secured to prevent it from being accidentally put back intooperation.


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Description/function(1) Mains switch, illuminated

(2) Mains fuses M 1.0(3) Safety sockets, (+15 V DC) for tapping of the output voltage(4) Safety sockets, (0V) for tapping of the output

voltage +15 V DC(5) Safety sockets, (15 V DC) for the tapping of the

output voltage(6) LED, for monitoring the output voltage +15 V DC(7) LED, for monitoring the output voltage 15 V DC(8) Connection socket

Technical dataInput voltage: 230 V AC, 50...60 HzOutput voltage: 15 V DC/3 A stabilizedFuse: Mains fuse M 1.0Output: 8 safety sockets, 4 mmConnection: Mains connection cable with earthing-pin plug

3-Temperature controlled system 73412

Description/functionThe temperature controlled system as an oven with timer bell contains ahalogen lamp 124V, and is equipped with a heat sink. Thus, the first storageelement and resistor are realized.A PTC sensor (2) with its mass andthe thermal resistor between heat sourceand sensor forms the second storage element of the PT-2 controlled system.The entire arrangement consists of a ventilator motor (3) whose outputpower can be adjusted using the potentiometer (4) .adjustable flap (5).The entire system is arranged in a transparentchannel (6).The heating power (7) is supplied by the power amplifier 734 13 via adiode, so that it is guaranteed that the control loop is operated only in the firstquadrant (+U; +I) and that positive feedback is not transformed into negativefeedback in the controller.


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The oven temperature is measured with a PTC sensor (2) and converted viatransducers in either 2 mA/10C or 1 V/10C: The operation mode isselected using the switch (8).Output (9) : the controlled variable x.The ventilator (3) is located at the beginning of the controlled system. It issupplied via an electronically stabilized voltage source so that constantdisturbance variables z1 can be set using the potentiometer (4).The flap (5) has calibrated positions (z2) at the end of the controlled system.

Recommended settings:Motor: 2 scale divisionsFlap: 2 scale divisions

Technical dataPower supply: 15 VTemperature: max. 100 CDelay time TV: approx. 10 sCompensation time TG: approx. 120 s


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4-Two position controller 73401

Description/functionThe two position controller has one non-inverting input (1), and oneinverting Input (2), which lead to a differential amplifier at the input of thecontroller.The difference can be tapped at (3). If the reference variable W is fed tothe (+) input and the controlled variable X to the () input, the error signalXe = W X = Xw is formed.Here Xw is the control deviation.The controller is designed as a comparatorwith adjustable hysteresis (max. 2.5 V) (4).The output signal at output (5)is 0 or 10 V, and 0 or 5 V at output (6).

Technical dataPower supply: 15 VInput voltage: 10 VOutput voltage: 0/+10 V, 0/+5 VHysteresis: 2.5 V


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5-P controller 734 03Description/function

The P controller has two non-inverting inputs (1)and outputs (2).The amplification factor (proportional-action coefficient) Kpcan be adjusted roughly with (3) in steps of x 0.1; x 1 and x 10and finely and continuously from 1 to 10 with (4).Correcting range: 0.1 Kp 100 .Outputs (2) are operational amplifier outputs (I 20 mA).If the modulation limit is exceeded (of the proportional band),the LED (5) lights up.

Critical frequency fg 4 kHz for Kp = 100 and U2 = 10 Vpp.A smaller value for Kp produces a correspondingly highervalue for fg. The controller can therefore also be used invery fast control processes.

Technical dataPower supply : 15 VInput and output signal range : 10 VKp : 0 ... 100

6-D controller 734 05

Description/functionThe D controller operates non-inverting via inputs (1)and outputs (2) .It is switched on and off with switch (3).The derivative-action coefficient KD (unit: seconds)can be roughly adjusted in steps of x 0.1; x 1; x 10with switch (5) and fine, continuous adjustment is made with

potentiometer (4) from 0.02 to 0.2.Correcting range: 2 ms KD 2 sThe outputs (2) are buffered. If the circuit is overdriven,this is indicated by the OVER LED (6).

Technical dataPower supply: 15 VInput and output signal range: 10 V


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7-I controller 734 04

Description/function

The I controller operates non-inverting via inputs (1) andoutputs (2). The off input (3) leads to the reset switch of theintegral-action capacitor and is required when operating withthe test function generator 734 40.This ensures that the starting condition Ua = 0 is restoredafter each recording period.Switch S2 (4) is connected in parallel to the automatic reset switch.The integral-action capacitor can only be charged in positionON. The integral-action coefficient KI (unit: second s1) can

be roughly adjusted in steps of x 0.1; x 1;x 10 with switch (6)and fine, continuous adjustment is made with potentiometer (5)from 1 to 10:Correcting range:

If the circuit is overdriven, the OVER LED (7) lights up.This condition can be remedied by discharging theintegral-action capacitor: switch S2 (4) to off.The integral action capacitor can beshort-circuitvia the input (3): initial condition NULL.

Technical dataPower supply: 15 VInput and output signal range: 10 V


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Experiment Instructions:

A. Static Performance

Static testStatic test is performed to check the linearity of the equipment under test. Ifwe want to test the input power we need to keep the ventilator-motor, andflab at constant values and vary the input power scale.

Experiment:- Connect the Temperature Control System Block Diagram (Figure 1)

to the Power Supply unit and with the Reference Variable generator.

- Set the output switch to 1V/10C.- Make sure that the temperature of the process settles at room

temperature ( Output voltage = the room temperature ).

Figure .1

1. Effect of input power over temperature- Keep the flap at scale 2 and ventilator potentiometer at scale 3.- Record the temperature ( using multimeter to reading

the output voltage ) of the system at inputs 0, 2, 4, 6, and 8 Volts.

Input Voltage(V)

0 2 4 6 8

Temperature(C)


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2. Evaluation- Plot the temperature versus the input power.

- Label your scales very carefully.

B- System Identification.

The dynamic model of the temperature process can be described as first orderlinear transfer function:

Where K is the DC gain defined as the ratio of output voltage to input voltage.

y() = final (steady state) value of the outputu() = input to the system

: time constant when the output reaches 63% of the final value.L : velocity lag (time delay) pure time delay (dead time), The time required

for the system to start responding to the input change. as shown in Figure2

Figure 2 Representation of transient response

A linearized quantitative version of this model can be obtained with an open-loop experiment, by using the following procedure:

1. With the plant in open loop, take the plant manually to a normaloperation point. Assume that the plant output settles at y(t) = y0 for aconstant input 0 u(t) =u .

2. At an initial time 0 t , apply a step change to the plant input, from 0 uto u .


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the channel initially appears automatically in the table (5) and in thediagram (6) .

And will appear the box Allows you to change the settings of measuringparameters which control the actual measurement.

put the Meas. Time to 200 s

When you want to start measurement just press to , Starts and stops anew measurement. You can use the right mouse button to open the tabledisplay menu in the table and the evaluation menu in the diagram.

4- Using Cassy lab software, Record the transient behaviour for thefollowing case:( Step input ):

1. Cool down the system at room temperature ( remove the inputpower from the temperature system open flab to 4 and increasethe potentiometer to 10 to increase speed of motor until theoutput voltage equal the room temperature ).

2. After cooling the system restore the input power, Set the flap atscale 2 and ventilator potentiometer at scale 3.

3. Start with Reference voltage = 6 V until you reach a steady state.


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4. Record the time required to achieve this state, name it T.

Figure 3

5- From the transient responses in above case, deduce the open looptransfer function of the temperature process (identify the parameters K,

and L from the obtained response).

6- Comment all of your result.

__________________________________________________________________________________________________________________

______________________________________________________

C. Open-Loop Two-Position Control

The main targets of the previous Parts were to have an understanding ofmodelling concepts in terms of static and transient performance. Thetemperature process was used in its open-loop form.In this Part will introduce the idea of open and closed-loop control.

Following are the objectives of this Part:- Study the two-position (discontinuous) controller.- Examine the effect of hysteresis on the temperature process.- Maintaining output temperature close to a reference (set point) value.

There are many controllers that could be used to perform the task. They differin simplicity and configuration.


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In this part, the two-position controller is introduced as the regulator. Thiscontroller will recognize only two states and will have only two actions: On orOFF.

Figure 4 shows a block diagram of the circuit under study:

Figure 4: Block diagram of a closed loop two-position controller.

The controller that we will study can have hysteresis effects, by examining theblock diagram, we can easily deduce that:

e(t) = r(t) y(t)

If there is no switching hesteresis (h = 0), the two stales of the controller are:

However, if there is switching hysertersis h, the two states:

Experiment:1- Cool down the system at room temperature ( remove the input power

from the temperature system open flab to 4 and increase the

potentiometer to 10 to increase speed of motor until the output voltageequal the room temperature ).2- Set up the experimental arrangement as shown in the block diagram of

Figure 53- Keep the same settings as before (switch off).4- Disconnect the feedback path from the output to the input of the

controller.5- Setting fan potentiometer to 2-scale division and the flap to 2-scale.6- Set the reference to 6 V.


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7- Set the switching hysteresis to 0 V and plot the reference and the outputon the same graph.

Figure 5

D. Closed-Loop Two-Position Control

Experiment:

1- Cool down the system at room temperature ( remove the input powerfrom the temperature system open flab to 4 and increase thepotentiometer to 10 to increase speed of motor until the output voltageequal the room temperature ).

2- Set up the experimental arrangement as shown in the block diagram ofFigure 5

3- Setting fan potentiometer to 2-scale division and the flap to 2-scale.

4- Set the reference to 6 V.

5- Plotthe output and control signalfor the following values of hysteresis:

1) h = 0 V 2) h = 0.5 V

Observe the behaviour of the lamp!, Deduce the frequency of thecontrol signal.

6- Comment your results.


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____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

7- Discuss the difference between the open-loop and the closed-loop two-position controller.

8- Discuss the effects of the hysteresis on the output and control signal.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Note : All the plots must be Labeled.

E. PID-Controller:

So far, a simple control technique has been evaluated: the two-positioncontrol. This part will introduce another type of controller; which is calledPID (Proportional, Integral and Derivative). This control approach is one ofthe oldest and most popular techniques used in the industry, because it is

simple and effective.Figure 6 shows a block diagram of this control.

Figure 6

In this part, we will see two methods to design a PID controller.

First: Cohen and Coon method.

The model obtained (transfer function) can be used to derive various tuningmethods for PID controllers. Cohen and Coon proposed one of these methods.The suggested parameters are shown in table 1.

Table 1


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The PID controller is given by:

Experiment:The connection for this experiment is given below Figure 6:

1. Cool down the system at room temperature ( remove the input powerfrom the temperature system open flab to 4 and increase thepotentiometer to 10 to increase speed of motor until the output voltageequal the room temperature ).

2. Set the flap and ventilation pot to div 2 and power supply to 6 V.

Figure 6


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A.Effect of KP, KI, and KD :A proportional controller (Kp) will have the effect of reducing the risetime and will reduce ,but never eliminate, the steady-state error.

An integral control (Ki) will have the effect of eliminating the steady-state error, but it may make the transient response worse .A derivative control (Kd) will have the effect of increasing the stabilityof the system, reducing the overshoot, and improving the transientresponse.

Study the Effects of change each of controllers Kp, Kd, and Ki on aclosed- loop system and summarized it in table shown below:

B.General tips for designing the PID controller:When you are designing a PID controller for a given system, follow thesteps shown below to obtain a desired response:

1. Obtain an open-loop response and determine what needs to beimproved.

2. Add a proportional control to improve the rise time (Kp = 1, 10).

3. Add a derivative control to improve the overshoot.

4. Add an integral control to eliminate the steady state error.

5. Adjust each of the KP, KD and KI until you obtain a desired overallresponse.

Important Notes:1. Use the table to decide which KX where X=P, I or D to increase

or decrease.2. Probably, you dont need to implement all the three controllers.

Plot and evaluate the response in terms of speed, steady state error,

overshoot etc

control of temperature system 2

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