Electrical and Electronic Control Lab Report: PID Control and Tuning

This report details an electrical engineering laboratory experiment focused on liquid level control using Proportional-Integral-Derivative (PID) controllers. The experiment investigated the effects of proportional (P), integral (I), and derivative (D) control actions, both individually and in combination, on the stability and response time of a liquid level control system. The methodology involved observing the system's response to step changes in set points and varying the controller gains (Kp, Ki, Kd). The report presents the results through graphs illustrating the system's behavior under different control configurations, including proportional, PI, PD, and PID control. Furthermore, the report explores controller tuning using the reaction curve method to determine optimal PID controller values. The findings demonstrate the effectiveness of PID control in achieving stable and responsive liquid level control, with the PID combination providing the best overall performance. The report concludes that the PID controller effectively minimized deviations from the set point and achieved a quick response to changes, with the reaction curve method providing effective tuning parameters.

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

Contents
Executive Summary.....................................................................................................................................3
Introduction.................................................................................................................................................3
Aim..............................................................................................................................................................4
Level control loop....................................................................................................................................4
Level Control loop....................................................................................................................................5
Level control loop....................................................................................................................................6
Level Control Loop...................................................................................................................................7
Tuning Control Loop................................................................................................................................7
Conclusion.................................................................................................................................................11

Executive Summary
The core objective of this particular experiment was to make observation on the different
impacts of the control output on the level of the liquid that was found in .The tank was under the
study. For different control arrangements, the system response was actually observed and later
subjected to the analysis. The observation made was that there was a stable response in the cases
where the combination of the system was used. The combination of the system included the use
of proportional, integral and derivative control. This has been commonly known as PID.Finally
there was use of the curve method in the determination of the values of the PID control. The
obtained values were used for the process of analysis in the laboratory. The conclusion that was
drawn was that the variance or the deviation of the water level from the point that had been set
was very little and the system was able to recognize a change quickly in the cases where there
was PID applications.
Introduction
The focus in this particular laboratory work was on the controlling level of the liquid. The
laboratory work has helped in the understanding of the ways to control the level of the liquid that
was found within the tank and its subsequent analysis. It was found that the same principle can
find its application in the areas that include control of the flow of the liquids and determination
of the temperature. The water level in the tank was regulated using a system of the sensors
through tuning of the PID control parameters. The behaviour of the system was carefully
observed. In the later hours, there was determination of the values of different variables while

using the controller of PID.In this particular case, Edibon water level apparatus was used.
Figure 1. Edibon water level apparatus.
Aim
The core aim of the experimental work was to comprehend the primary principles that are used
in the process of controlling the level of liquid in the container. This was done while using
different variables. The volume of water was brought to the desired point through adjustment of
the control output. The adjustment was achieved through using the PID combination. The similar
combinations can be applied in the control of the temperatures, pressures and other parameters of
different control systems in the industries.

Level control loop
This was also known as the proportional control loop. In this section of the experiment, the liquid
level within the container was regulated while using a system of sensors. The sensor was
configured using a controller connected to the output. This was meant to control the actuating
system of the requirements. The type of the configuration was meant to make it easier in the
study of the dynamics of the system. This was then followed by the application of the response to
the applied actions. The set point for the controller was at a point of 120mm when the output was
regulated using the proportional output. The initial point for setting was found to be at
approximately 20%.After reaching the initial set point, an increment of 10mm was introduced to
the initial set point and proportional controller ( Kc) value was set to 0.5. The reaction of system
was observed carefully, and the results obtained were recorded. The study was repeated for two
different values of Kc = 0.25 and 0.75 trying to achieve different control response. The reactions
of the system for the 3 different values of Kc are shown in Error: Reference source not found.
Figure 2. Level control using proportional controller.

The results that were extracted from the system were as indicated in the above graph. From the
graph, it is very visible that the level of the water in the tank was at 114mm after the increment
of 6mm was made. The system tried to shift to the point that had been set and that was 120mm
which was based on the water level rising above the set point. There was a time delay of
approximately 60 seconds (for kc=0.5) and 80 seconds (for kc=0.25 and 0.75) before the system
acted to bring the water level to new set point. This particular reason can be related to the dead
time. The dead time is normally considered as the delay that exists between the period when a
process of the changes in the variable are noticed and when the changes impacts are observed.
Also there is an obvious observation of the deviation of the new set point from the graph with
values being undershoot or overshoot.
Level Control loop
The level of the liquid within the container under study was monitored using a system of the
controllers and sensors in this particular section of the experiment. The setting of the
proportional value was at 0.5 while the integral values changed from 0.1 to 10.There were
observation of the system under the influence of the combination that had been stated before.
The results that were obtained were indicated in the figure 3.There was also an observation on
the experimental work regarding the approximation of the lagging time. The time was found to
be between 3-4 seconds for the apparatus of the sensor and the actuator.

Figure 3. Level control using PI controller.
From the above graph, it can be observed that through use of the integral controller alongside the
proportional, the overall system got batter. The variance from new set point (135ml) is less when
proportional and integral controller is set at 0.1 and 10 respectively. Also the response of the
system was very fast as opposed to the previous results. In contrary to the other results, when
proportional control value was set at 0.5 while integral control value is set at 5, the response of
the system was sluggish and the deviation from set point was high. It is important to note that the
system even took more time to response through stabalization.This is very evident from the
graph.
Level control loop
It is also known as the PD control. In this specific part of the experiment, the control of the water
level within the tank was done while using a system of the sensors and the controllers. The
control output was configured using actuating system. The response of the set up was put into
consideration while using different combinations. In this particular section the effect was very

evident as the system quickly shifted to the new point that had been set as the deviation was
introduced.
Figure 4. Level control using PD controller.
As can be seen in the graph, the values of the derivative controller are greatly increased from the
initial set point that was approximately 135ml.There was a general deviation of positive or
negative 3.It is important to note that the system response was faster as compared to the
previously obtained results.
Level Control Loop
The component of the proportional is dependent on the variation that exists between the set point
and the variable in the process. This variation is referred to as the error. The integral component
adds the error over time. The variation of even a very small error will cause a variation of the
component to slowly increase. There will be a continuous increase overtime of the error unless
the error reduces to zero. This will possibly give a steady state.

Figure 5. Level control using PID controller.
From the graph it is very evident that when the value of proportional controller was 0.5, the
integral value was 0.1 and the derivative value was 0.5, the system reacts little slower as
compared to the cases when proportional controller is set at 0.25, T i=0.5 and T d= 0.25.This could
be translated to be the case for other similar results. The response from the system was very
quick when the changes were introduced.
Tuning Control Loop
It involved the use of the control curve to determine optimum values of proportional, derivative
and integral controller. This is normally an open loop method that consists of the opening control
valve. This includes introduction of very small changes in the system. The obtained results from
this system was used to calculate the optimum values of the variables.The entire process
involved drawing of a tangent line in the inflection point of sigmoid and the values of R and L
are measured. L is the retard time of the process while R is the slope of the tangent in the
inflection point of the curve. The time of retardation was the defined as the period between the
instant changes of the setup. The percentage of the position was determined at these particular

points and was later used in the control of the valve. This was the DP percentage and its process
was as shown.
In order to obtain the maximum PID controller, a step response was introduced which allowed
the level of water in the tank to rise. This was used to obtain the period or the duration of the
rise, since the rise of the water level was allowed to raise slowly, the smooth reaction curve was
obtained as indicated in the figure below. The optimum values of the PID controller was then
determined. It is very possible to use the curve reaction method to obtain the maximum values of
the PID controller.

Figure 6: Reaction curve method.
The optimum values of the PID controller were as illustrated below
Table 1. Optimum values 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
 P+ I+ D= 83 ×0.053 ×140
45 ≅ 14
According to the above values the analysis of the results using the PID control system could be
presented using a graph that has been shown below.
Figure 7: Level control using PID controller (2nd combination).
From the graph it is quite obvious that the optimum values of the PID controller were calculated
from the curve of the reaction method. The system was so quick to recognize the changes and

tried to adjust to the new point that had just been set. The new point was at 120ml.The deviation
from this particular new point was very little. The system adjusted to the new point after a period
of 40seconds.After this period of time, the system remained in a stable condition with little
variations being observed at the respective intervals. This shows that the values of the
approximation that were obtained from the curve correction methods were relatively correct.
Although the curve was obtained using the reaction curve method, the values that were obtained
were higher and the stability of the system was much better.
Conclusion
There was analysis of the response of the system for different configuration to produce the
output. The initial set point of water was at 250mm.This was followed by an increment of
5mm.Observation was made in regard to the response of the system before comprehensive
analysis could be effected. From the analysis, it was found that the system response to the
changes or increments was very much better in the combination. The end curve method assisted
in the obtaining of the optimum values that were used in the analysis. The analysis done
indicated that the system response was quick with very little deviation from the set point. The
experiment was found to be very useful and its principles can be applied to other industrial
processes of controlling pressure and temperature.