ENG342 - Liquid Level Control in a Tank: Electrical Control Report

This report presents a comprehensive analysis of liquid level control in a tank using proportional (P), integral (I), derivative (D), and combinations of these control methods (PI, PD, PID). The experiments conducted involved observing the system's response to different control configurations, with a foc...Read More

ELECTRICAL AND ELECTRONIC CONTROL
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List of Figures:
Figure 1. Edibon water level apparatus.....................................................................................4
Figure 2. Level control using a proportional controller.............................................................5
Figure 3. Level control using a PI controller...............................................................................6
Figure 4. Level control using a PD controller.............................................................................7
Figure 5. Level control using a PID controller............................................................................9
Figure 6. Level control using PID controller (2nd combination)................................................10
Figure 7. Reaction curve method.............................................................................................12
List of Tables:
Table 1. Optimum values of PID controller..............................................................................13

Contents
Executive summary.....................................................................................................................................2
Introduction.................................................................................................................................................2
Aims.............................................................................................................................................................3
Level Control Loop (Proportional Control)...............................................................................................4
Level Control Loop (PI Control)................................................................................................................5
Level Control Loop (PD Control)..............................................................................................................6
Level Control Loop (PID Control):............................................................................................................7
Reaction curve method...........................................................................................................................9
Conclusion.................................................................................................................................................13
REFERENCES..............................................................................................................................................14

Executive summary
The core objective of this particular experiment is to give a comprehensive observation of the
impacts of the combination of output when used in the liquid level of the tank. The observation
and subsequent analysis of different configuration were done while checking on the response of
the system. The observation that was made was that the response of the system was much stable
in the processes that included the use of proportional, integral and derivative controls. This
system of a combination is commonly known as the PID system. There was a use of the method
of the reaction curve in the determination of the maximum values of the PID in the control. The
values that were obtained were used in the laboratories for the analysis of the various responses.
The conclusion that was drawn was that the differences or the variance in the water level from

the set point were very much little. The used system showed the capability of recognizing the
changes very fast when the PID method was employed(Rus and Tolley 2015)
Introduction
The control of the water level in the container was the main objective of the project. The project
assisted in the analysis of the operation. The applied principles on these particular systems were
exploited in other places apart from the water level. Some of the areas of the applications include
the regulation of the temperatures and pressures. The level of water in the tank was monitored
using a system of sensors. The sensor system has been configuring with the actuating system to
make the operation of the control system much easier. In the final stages of the project, the
reaction curve method was used in the generation of the values of different variables for the PID
controllers (Adamski et al 2013).

Figure 1. Edibon water level apparatus.
Aims
This laboratory project has an aim of understanding the basic principles in the controlling the
liquid level in the tank by use of various control variables (Mathad et al 2013). The control
output was adjusted to ensure that liquid bevel in the tank was brought the desired set point. This
was done by the use of proportional (P), integral (I) and derivative (D) controllers in various
combination. The main reason for using these principles was to control pressure, temperature and
other variables as needed in different industries. The major reason for carrying out such
experiments was to aid in the understanding of the crucial principles of controlling the liquid
level within the tank while using variables of a different control. Through adjustment of the
output of the control, the liquid level in the tank(Zammit, Staines and Apap 2014).
Level Control Loop (Proportional Control)
In a part of this experiment, the tank liquid level was controlled using a sensor and a configured
controller for proportional output via the actuator. The configuration created an easier way of
studying the system dynamics and applied control action responses. By means of the controller
set which was proportional to output, the liquid level was regulated around 120mm set point. The
actuator set at 20% initially. Though there should have been an increment of 10mm after the
initial set reached and introduced to the initial set point band proportional controller (Kc) 0.5
parameter. The system feedback was given a careful observation while recording the result
obtained. The experiment was repeated using two different values of Kc=o.25 and 0.75 for the
achievement of different control responses. The system responses for three different Kc values
that were obtained were as shown in figure 2 below

Figure 2. Level control using a proportional controller
The graph above shows the result obtained. The observation was made after tank water level was
set at 114mm. There was 6mm water increment in the tank. This introduction was such that the
new system was adjusted to a set point of (120mm) based on the proportional output (Kc=0.25,
0.5 and 0.75) through the system responses very slow. The level of water rises above the set
point with a delay of approximately 60 sec at Kc=0.5 while with 80 sec at Kc= 0.25 and 0.75
before the system action to bring a level of water to the new set point was achieved. This was
due to dead time creating laxity between the change in variable and time of the changes
notification. In addition, the new setpoint variance was observed in the graph as an undershoot
and overshoot.
Level Control Loop (PI Control)
In this particular part of the experiment, the liquid rise in the tank was monitored by use of
sensor and a configured controller to ensure a proportional and integral actuator output. The
value of proportional was set to 0.5 whereas that of integral varied between 0.1,5 and 10. The

system response based on the various combination of proportional and integral control was
observed and the result shown in figure 3. Besides this, in this laboratory, there was a clear
observation of a lag time of 3 to 4 second between the actuator and the sensor in the apparatus.
Figure 3. Level control using the PI controller
The observation from the graph above was that through the use of an integral controller
additional with a proportional controller, the response of system has got better overall. The new
setpoint variance (135ml) was less where the proportional and integral control set at 0.1 and 10
respectively. In other hand System also has got a quick response as compared to the previous
laboratory. Conversely, if the proportional control value was set at 0.5 and the integral control
was at 5, the slow response of the system observed with the setpoint variance was high.
However, more time was taken for stabilization of the system as in the graph above (Mathad,
Ronad and Jangamshetti 2013).

Level Control Loop (PD Control)
In this project section, the tank liquid rose under the regulation of sensor and configured the
controller to produce proportional and derivative actuator output. The value of proportional was
set to 0.5 and the values of derivative vary between 0.25, 0.5 and 0.75. The careful system
response has done based on the various combination of controller output. In the laboratory, the
derivative effect on the control system has more evidence with respect to the abrupt system
adjustment to the new setpoint due to the introduction of the variance in the system. The
obtained results were as shown in figure 4.
Figure 4. Level control using PD controller.
It is very clear from the above graph that the derivative controller value is increasing while the
set variance from point (135mm) decreases significantly by –or + 3.3ml approximately. Besides,
the system response was observed to be quicker the than two previous laboratories which were
caused by the derivative control. The change recognized by a derivative takes a sudden action to

ensure that the liquid level is brought to the desired set point (Mathad, Ronad and Jangamshetti
2013).
Level Control Loop (PID Control):
In this part of the experiment, the container liquid though controlled by a sensor and the
controller configured to ensure proportional, derivative and integral actuator output. The
proportional controller value varied between 0.25, 0.5 and 0.75 while those of integral controller
varied between o.1, o.5 and 0.9 in this laboratory part, the integral and the derivative control was
characterized by the combination and the proportional controller for the system output
stabilization to ensure the desired level quickly while using less variance. The result obtained
from this laboratory is shown in figure 5 below
Figure 5. Level control using PID controller
The above graph is an evidence that the proportional controller value is 0.5, the value of integral
is set at 0.1 while the function of the derivative is 0.5, and the system reaction is little slower as
compared to the cases where proportional controller set at 0.25, Ti=0.5 and Td=0.25. in cases of
a higher proportional controller value like 0.75, a higher integral value number Ti=0.9 and a

higher derivative value Td=o.75 .is predicted in the system that variance slowly with according
to adjustment( the water level 123 shuts the valve 20 to 0 until 100mm water level reached. At
the same time, the opening of the valve continues to 100 till the level of water reached 2mm
above the setpoint and shuts again at zero).
The observation was that the system response with PID controller was better compared to the
other control combinations (Ortega, Perez, Nicklasson, and Sira 2013).
The response of the system increase with the introduction change and the water level variance
decrease significantly
Reaction curve method
The reaction curve assisted in the determination of the of the maximum value.In this specific
laboratory work, the controller that was used had the following features; integral controller part,
the proportional and derivative components were used in a combination set up. The parameter of
the system was obtained through calculation using the relevant software. It is upon the opened
loop that normally induces inputs into a quick exchange of the loop regulation. The results that
were generated were very crucial in the induced system.
The process specifically involved tangent line tracing in the inflection of the sigmoid point and
measure the value of R and L. The retard time (L) and the slope of tangent ras in the inflection of
curve point were noted (Rus and Tolley 2015).
Retard time Tuning Control Loops (Reaction Curve method) referred to the time taken between
the change instant in the step and the point of the tangent to the sigmoid cuts the former

controlled variable value. With DP the percentage of the variable position in the control, valve
aims in introduced the process steps as in the 6 below
Figure 6. Reaction curve method.
The optimum controller PID values were got by the responses of the system in this section as
shown in the figure 7 experiment. The introduction of a set of response and the tank water level
allowed rising for a long time thus obtaining reaction curve, therefore facilitating the use of the
reaction method allowing obtaining maximum PID controller figure. The tank water increment at
a slow pace smoothed the reaction curve as obtained in figure 7 to be used further to determine
the maximum of PID controller values.

Figure 7. Reaction curve from the system for tuning a control loop
The information in table 1 is used in the calculation of the highest PID controller figure
Values of xy of PID controller
L=140 sec ,dt=80 sec , change∈water level=0.02 litre
R= ( 100 ×0.02 ) × 80
3000 =0.053
 P= 100 ×0.053 ×140
45 =16.5
 P+ I = 110× 0.053 ×140
45 ≅ 18

With value based on the PID controller, the parameter obtained was set for integral,
proportional and derivative control while carefully observing the response of the system. The
obtained result of the values was recorded in figure 9 below.
Figure8. The response of the system with optimum PID values.
The PID controller optimum values in the above graph as obtained reaction method curve
showed that the system recognizes a quick change while adjusting a new set point (120). The
variance decreases from the set until the system reached the new set point that is observed in the

graph above (after 40 seconds). The stability of the system remains intact condition after then a
little variation that was only observed in the interval(Pimentel, Gonzalez and Barbosa 2016).
Conclusion
In order to conclude in the trial of the experiment, the response of a particular system of different
configuring with varied output was analyzed.The level of water in the tank was allowed to rise to
the point that had been already been set at 250mm. This was then followed by an increment of
5mm that was introduced at intervals. The observation was then made in order to establish the
reaction of the system in response to the values of the control. The values that were obtained
subsequently aided the production of the results. The results that beware obtained indicated that
the response of the system was relatively much efficient when proportional, derivative and
integral combinations were used in the process (Zammit et. al 2014)
At the end of the exercise, there was the use of the curve reaction to getting the maximum
variables of the PID control. These variables were found very useful in the laboratories for the
analysis of the response system. The observation made was that the response system was very
quick when the PID control was put into use. It was also observed that the variance from the set
point was very little. The experiment was found to be very useful since the underlying principles
could be applied in other sectors that include regulation of the temperatures and pressure.

REFERENCES
Adamski, M., Wiśniewska, M., Wiśniewski, R., and Stefanowicz, Ł., 2012. Application of
hypergraphs to the reduction of the memory size in the microprogrammed controllers with
address converter. Przegld Elektrotechniczny, (8), pp.134-136.C. Wind energy conversion
systems-a technical review. J. Eng. Sci. Technol, 8(4), pp.493-507.
Mathad, V.G., Ronald, B.F. and Jangamshetti, S.H., 2013. Review on a comparison of FACTS
controllers for power system stability enhancement. International Journal of Scientific and
Research Publications, 3(3), pp.2250-315.
Ortega, R., Perez, J.A.L., Nicklasson, P.J. and Sira-Ramirez, H.J., 2013. Passivity-based control
of Euler-Lagrange systems: mechanical, electrical and electromechanical applications. Springer
Science & Business Media.
Rus, D. and Tolley, M.T., 2015. Design, fabrication, and control of soft robots.
Nature, 521(7553), p.467.C. A new model for a PMSG-based wind turbine with yaw control.
IEEE transactions on energy conversion, 28(4), pp.929-937.
Pimentel, B.S., Gonzalez, E.S. and Barbosa, G.N., 2016. Decision-support models for
sustainable mining networks: Fundamentals and challenges. Journal of cleaner production, 112,
pp.2145-2157.

Zammit, D., Staines, C.S. and Apap, M., 2014. Comparison between PI and PR current
controllers in grid-connected PV inverters. WASET, International Journal of Electrical,
Electronic Science and Engineering, 8(2).