Control, Energy and WSN: A Study on PID Controllers and Fuzzy Logic-Based Control for Single Tank System

CIS116-6 Wireless Embedded Systems
Assignment Part-I

Control, Energy and WSN
Solution A:
The basic control process is where single input and single output is present known as SISO
system. Here the task is also formulated as SISO system other process known as Multiple
Input Multiple Output (MIMO) system where the manipulating and disturbance parameters
are more than one. Most of industrial controller are relying on the concept of PID, in
process industry almost 95% of the controllers are PID. The key reason wide acceptance of
PID controller is, its design based only simplicity and the structure based on applicability to
different processes.
The whole concept of the controller depends on the manipulating the process error.
Ultimately the error is the difference of control variable and the desired value.
Err=PV-SP
There are variety of combination of the controller are involved which varies upon the type
of application for process industry below list shows the combination and frequency of use
P Sometimes use
PI Mostly use
PD Rarely use
PID Most often use
The purpose of the controller is to provide the signal that will cause the process to be
modified in such a way as to keep the set point (reference) and the process variable (actual
output) equal.
Any change in set point or the loads on the process should cause a change in the

Control, Energy and WSN
controller’s output to assure that the PV tracks SP.
Types of analog controller
1. simple ON/OFF controller (cycling or chatter)
2. proportional controller
3. Proportional Integral controller
4. PID controller (good transient & Steady state control)
The most important block in an analog controller is the ERROR AMPLIFIER
Proportional:
P controller widely use in the first order system to stabilize the unstable process. It helps in
decreasing the steady state error. with increase in gain of the system the steady state error
reduces. With high value of P it gives smaller amplitude and phase margin also reduce
noise signal
Drawback of proportional controller
The error can’t be eliminated completely. To reduces the error, the controller must raise its
output. But to raise its output, the controller must have some error. This residual error can
be reduced by increasing the gain but too much gain will cause the system to oscillate.
Derivative:
Integral control doesn’t provide capability to predict the future error of the system, so the
response is very normal even after the changes occur in set point (reference). The use of
derivative controller can avoid such issues by predicting the future response of the error
signal. The output of the plant or process dependent on the rate of change of the error signal
with time and whole things multiplied by the D-constant.
Integral:
To eliminate the residual system error, the controller’s response must be changed. In
proportional controller the output was proportional to the system error.
PID:

Control, Energy and WSN
PID controller helps in optimal control with no steady state error, zero oscillations, good
stability and fast response. With PI controller use of Derivative helps in eliminate the
overshoot and oscillations of the system of the output response. It also having advantage of
can be implemented for higher order system.
Tuning of PID controller:
The dynamics of process need to be controlled with the use of PID controller, each term of
PID controller have their own characteristics and properties. Without tuning PID controller
the response of the system may cause very high deviation and instability of the system.
Various tuning methods are used in field of control engineering namely few are trial and
error method, process reaction curve, Ziegler Nichols method and modern meta heuristic
based tuning. One of the best suitable method is fuzzy controller.
Trial and Error method:
The open loop response first recorded based on that PID controller is installed after that
tuning is the important process. In this method the parameter of PID are set to zero and
increase the value of Kp till the response attain oscillations. After oscillations occurs
Integral value also adjusted and finally Derivative to obtain the quick response.
Process Reaction Curve Method:
Ultimately, it’s the open loop method. The input is step unit signal and the response of the
system is recorded. Than from the slope of the curve we can find the value of P,I and D
parameters.
Normally the process in engineering may contains number of input and output variables.
Though only one or two of the parameters are needed to control the whole process of the
plant model. Such controlling parameters are known as manipulating variable, and other
may be uncontrollable which are known as the disturbance parameters. Generally, the
controller has the feedback system where output of system is taken and compared with the
desired or set value if any deviation found in the comparison, corrective action is taken
correspondingly.