full report exp 10

CHAPTER 1

INTRODUCTION

1.1 Introduction

Model SPC211 is developed to study the application of Single Loop controls of some

common simulated processes (Flow and Level). The key topics are how to identify and

characterize some real plant processes available at some physical Plants and how to tune their

control loops using the Ziegler- Nichols, Cohen-Coon and IMC etc Tuning techniques for

Quarter Decay Ratio (QDR) or other performance criteria. Model SPC211 was developed to help

teach these key topics in Process Control and to provide the hands-on opportunity for controller

tuning skills to be acquired.

The Simulated Gas Flow Process consists of a main pipeline where process air

representing gas/vapour flows and then discharge to atmosphere via the process vent manual

valve VF. The process air that flows into the system is conditioned to have air temperature of

100°C. With reference to the dynamic graphic of the Simulated Gas Mass Flow Process at Model

SPC211, for PID control, mass flowrate measured by Gas Mass Flowmeter (FE91/FT91), is the

measurement input into PID Flow controller FIC91A which in turn throttles the Control valve

FCV91, via a Current-to-Air Converter (I/P), FCY91, and a Positioner (PP).

Table 1: Instrumentation and control configuration for gas mass flow process

Measurement FE91/ FT91 FT91 represents the gas mass

flowmeter

Control Type FIC91A PID Controller configured at DCS

Control Output FCY91 Current-to-Air Converter (I/P)

PP Pneumatic Position

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FCV91 Air Mass Flow Control Value.

Air-to-close (ATC) type

Figure 1: Simulated gas mass flow process diagram

1.2 Objective

The objective of this experiment is toanalyze the behaviour of the gas mass flow process by

simulation.

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CHAPTER 2

LITERATURE REVIEW

2.1 Literature Review

A proportional–integral–derivative controller (PID controller) is a generic control loop

feedback mechanism (controller) widely used in industrial control systems – a PID is the most

commonly used feedback controller. A PID controller calculates an "error" value as the

difference between a measured process variable and a desired set point. The controller attempts

to minimize the error by adjusting the process control inputs. In the absence of knowledge of the

underlying process, PID controllers are the best controllers. However, for best performance, the

PID parameters used in the calculation must be tuned according to the nature of the system –

while the design is generic, the parameters depend on the specific system.

Figure 2: PID Controller

Source: Industrial/Aerospace/Military Specifications by John T. Jackson retrieved online at

http://jrmagnetics.com/mtrctrl/mtrctrlpid.php

2.2 Proportional Term

The proportional term (sometimes called gain) makes a change to the output that is

proportional to the current error value. The proportional response can be adjusted by multiplying

the error by a constant Kp, called the proportional gain.

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A high proportional gain results in a large change in the output for a given change in the

error. If the proportional gain is too high, the system can become unstable (see the section on

loop tuning). In contrast, a small gain results in a small output response to a large input error, and

a less responsive (or sensitive) controller. If the proportional gain is too low, the control action

may be too small when responding to system disturbances.

Figure 3: Proportional Control



2.3 Integral Term

The contribution from the integral term (sometimes called reset) is proportional to both

the magnitude of the error and the duration of the error. Summing the instantaneous error over

time (integrating the error) gives the accumulated offset that should have been corrected

previously. The accumulated error is then multiplied by the integral gain and added to the

controller output. The magnitude of the contribution of the integral term to the overall control

action is determined by the integral gain.

The integral term (when added to the proportional term) accelerates the movement of the

process towards setpoint and eliminates the residual steady-state error that occurs with a

proportional only controller. However, since the integral term is responding to accumulated

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errors from the past, it can cause the present value to overshoot the setpoint value (cross over the

setpoint and then create a deviation in the other direction). For further notes regarding integral

gain tuning and controller stability, see the section on loop tuning.

Figure 4: Integral Control



2.4 Derivative Term

The rate of change of the process error is calculated by determining the slope of the error

over time (i.e., its first derivative with respect to time) and multiplying this rate of change by the

derivative gain Kd. The magnitude of the contribution of the derivative term (sometimes called

rate) to the overall control action is termed the derivative gain, Kd.

The derivative term slows the rate of change of the controller output and this effect is

most noticeable close to the controller setpoint. Hence, derivative control is used to reduce the

magnitude of the overshoot produced by the integral component and improve the combined

controller-process stability. However, differentiation of a signal amplifies noise and thus this

term in the controller is highly sensitive to noise in the error term, and can cause a process to

become unstable if the noise and the derivative gain are sufficiently large. Hence an

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approximation to a differentiator with a limited bandwidth is more commonly used. Such a

circuit is known as a Phase-Lead compensator.

Figure 5: Derivative Control

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CHAPTER 3

METHODOLOGY

1. The operator workstation is switched ON. (Acknowledge button was pressed to silence the

alarm buzzer sound).

2. Gas Mass Flow Process was selected.

3. The following Preliminary Exercises are for Dynamic Graphic is checked for the Simulated

Gas Mass Flow Process.

a) Familiarize and identify the single loop simulated plant process at Model SPC211.

Single Loop Simulated Process Simulated Process at Syntek

MODEL SPC211

Gas Mass Flow Process Simulated Gas Mass Flow Process

b) For the Single Loop Simulated process, its control loop was identified (i.e. measuring

instrument, controller and final control element with the tag name).

c) The engineering units for the measured variable (PV), setpoint (SP) and controller

output (MV (OUT)) for the process at the DCS Controller is checked.

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4. The following Preliminary Exercises are for dynamic behaviour of the process when the

controller output is changed (Operating Data Check) at the Simulated Gas Mass Flow

Process.

a) The dynamic graphic of the Simulated Gas Mass Flow Process at the operator

workstation of Model SPC211 was viewed.

b) Solenoid valve SV90 at the dynamic graphic page was OPEN. It should be green in

colour.

c) The PID control scheme was selected; call up the controller FIC91A Faceplate. The

controller FIC91A to Manual (MAN) mode is switched. Quickly step change the

controller output, MV (OUT) to 100%.

d) Call up the Process History View from the FIC91A Faceplate to observe the gas mass

flow response (red trend). Wait till the flow response reaches a new steady state (check

the PV value). Note the steady state air mass flowrate.

e) Then, step change MV (OUT) to 50%. Note that FIC91A is still in Manual (MAN)

mode. At the Process History View, the gas mass flowrate (red trend) was observed

until it increases. Note the steady state air mass flowrate.

f) Step change the controller output, MV(OUT) further to 0% with FIC91A still remain

in Manual (MAN) mode. At the Process History View, the gas mass flowrate (red

trend) was observed until it increases. Note the steady state gas mass flowrate.

g) ‘Print screen’ the observed gas mass flow response and enclose together with the

results sheets.

h) With FIC91A in Manual (MAN) mode, step change the controller output, MV(OUT)

back to 100%.

5. Observations and Results of Experiments.

The DCS trending records at the Process History View of each respective controller

constitute the results of the experiments. During any experiments, note down the

observations corresponding to the obtained response. The OBSERVATIONS AND

RESULTS SECTION is checked for the types of results to observe collect and submit them

as results of your exercise and experiments.

6. To Shut down Model SPC211

a) All the windows (including DeltaV Operate page) at the operator workstation is closed.

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b) Log Off from the operator workstation.

c) Shut down the operator workstation.

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CHAPTER 4

RESULT & DISCUSSION

4.1 Result

Table 2: Dynamic Graphic Check (Visual and Static Check)

Single Loop Simulated

PlantProcess

Process Control Loop Engineering units

Gas Mass Flow Process Tag

Name

Process

Parameter

Units

Measuring

Instrument

FT 91 PV Kg/h

Controller FIC 91 SP m/h

Final Control

Element

FCV 91 MV(OUT) %

Table 3: Dynamic Behaviour of the process (Operating Datas Check)

Actions Observations Remarks

With FIC91A in Manual (MAN) mode,

i) at MV (OUT) = 100% What is the current air

mass flowrate at steady

state?

1. 0 kg/h

2. Is the control value

FCV91 fully shut?

Yes

ii) at MV (OUT) = 50% What is the air mass

flowrate at steady state?

3. 34.1 kg/h

iii) at MV (OUT) = 0% What is the air mass


4. 38.7 kg/h


FCV91 fully open?

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Yes

4.2 Discussion

I. From the result obtained, discuss the dynamic behavior of the process (i.e order of

the response)

In this particular experiment, the behavior of the gas mass flow rate that is operating under first

order process is observed. The changes of this process are basically much related to the changes

of MV at the FIC 91.The process input is a step input. Step input was characterized as an

industrial process that can be subjected to a sudden and sustained input change.

II. Give suggestions to improve the process performance.

In this experiment, the process performance can be improved by introducing feedback controller.

The proportional control should be introduced to the process. The key concept in proportional

control are that the controller gain can be adjusted to make the controller output changes as

sensitive as desired to deviation between set point and controlled variable. The gain can be

chosen to make the controller output increase or decrease as the error signal increases.

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CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION

Based from the results and observations, the objective for this experiment is successfully

achieved since the behavior of the gas mass flow process has been analyzed and identified. Here,

we can conclude that when the FIC91 in Manual (MAN) mode as the value decreases, the values

of gas mass flow rate are increased. At the value of MV (OUT) which is 100 percent, the control

value FCV91 is fully shut. For the value of MV (OUT) is equal to 0 percent, the control value

FCV91 is fully opened.

5.2 RECOMMENDATION

The tuning process should be done uniformly according to the timing process. Make sure

the graph of the tuning is constant at steady state to get the actual value as the set point. Do not

overdo the simulation as it could affect the readings.

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CHAPTER 6

REFERENCES

Franklin et al. (2002). Feedback Control of Dynamic Systems (4 ed.). New Jersey:

Prentice Hall.

Christopher Kilian (2005). Modern Control Technology. Thompson Delmar Learning

Levine, William S. et al (1996). The Control Handbook. New York: CRC Press

‘Industrial/Aerospace/Military Specifications’ by John T. Jackson retrieved online at

http://jrmagnetics.com/mtrctrl/mtrctrlpid.php on 18/3/2011

‘Open-Loop Control System’ by Electrical Engineering Training Service retrieved online

at http://www.tpub.com/content/neets/14187/css/14187_92.htm on 19/3/2011

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CHAPTER 7

APPENDIX

Table 2: Dynamic Graphic Check (Visual and Static Check)

Single Loop Simulated

PlantProcess

Process Control Loop Engineering units

Gas Mass Flow Process Tag

Name

Process

Parameter

Units

Measuring

Instrument

FT 91 PV Kg/h

Controller FIC 91 SP m/h

Final Control

Element

FCV 91 MV(OUT) %

Table 3: Dynamic Behaviour of the process (Operating Datas Check)

Actions Observations Remarks

With FIC91A in Manual (MAN) mode,

i) at MV (OUT) = 100% What is the current air

mass flowrate at steady

state?

1. 0 kg/h


FCV91 fully shut?

Yes

ii) at MV (OUT) = 50% What is the air mass


3. 34.1 kg/h

iii) at MV (OUT) = 0% What is the air mass


4. 38.7 kg/h


FCV91 fully open?

Yes

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full report exp 10

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