This which calculates the error. 3.2 Analysis Procedure

This project is about using PID controller control the DC motor’s speed.
For that purpose, four circuits are used. These circuits are FVC (frequency to
voltage converter), Encoder (motor driver), Subtractor, and PID. Different
components like, resistors, capacitors, motor and IC’s are used in this
project.   

3.1          
Proposed Design Methodology

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Figure 1:
Proposed Design

+ –
 –
 

   PID

MOTOR DRIVER

      FVC

Y(t)

 

 

 

 

 

 

 

The reference input was given to the summer which subtracts the
error amount which is coming from the output and then gives that signal to the PID controller as
input. PID controller generates the signal as input to the motor driver circuit.
Tachometer is used to measure the speed in rpm, then FVC was used which converts
frequency into voltage. LM2907
IC was used for conversion purpose, it gives output to summer which calculates the
error.

3.2          
Analysis Procedure

We have to figure out a way
to control the speed of the small dc motor using 555 timers. Using a small
permanent magnet DC motor
to build small projects like, cars, robots, or quads, requires a speed controller
to make their work easier.

Figure 2:
Analysis Procedure

 

 

 

 

 

 

 

3.3          
Design of the Project Hardware/ Software            

The project has three main components for designing. All three of
them will combine to control the motor’s speed.

PID
controller
Encoder
(motor driver)
Frequency
to voltage converter circuit

3.3.1   
PID controller
design

PID is combination of three different
controllers which are following:

1.      Proportional controller

2.      Integral controller

3.      Differential controller

3.3.1.1             
Proportional Controller

In this controller, the output is proportional
to the error which is equal to the difference of the set point and the process
variable. The proportional controller has constant variable kp which is called proportional
gain. The rise time increases by the increment of proportional gain, and thus steady
state error decreases but it doesn’t
remove it completely 5.

Figure 3: Proportional Controller

The circuit diagram of proportional controller
is

 

 

 

 

 

3.3.1.2             
Integral controller

The
proportional controller did not remove steady state error completely. So for
removing steady state error integral controller is used, it removes the steady
error completely but it increases the rise time and induces the overshoot in
the system 5.

Figure 4:
Integral Controller

The circuit diagram of Integral
controller is

 

 

 

 

 

3.3.1.3             
Derivative controller

The derivative controller is used to decrease the overshoot, and for reducing the settling
time. This can be achieved by:

Increasing kd reduces the
rising time.
Increasing kd reduces the
settling time.

Where Kd is the gain of the derivative controller 5.

The circuit of the derivative controller
is

Figure 5:
Derivative Controller

 

3.3.2   
Encoder

A two wing fan is attached with the DC motor. A phototransistor
sensor is placed in front of a Led and the wings of the fan are in between the
sensor and led.  Whenever fan wings cuts
the LED, the sensor counts the rotation 6.

Figure 6:
Encoder

 

 

 

 

 

 

 

 

 

3.3.3   
Frequency to
voltage converter

The
circuit to convert the frequency to voltage is implemented by using IC LM 2907.

Figure 7: Frequency to
Voltage Converter

The input
frequency is coming from the tachometer and then the circuit converts that
frequency into voltage and gives it as feedback to the circuit 7.

3.4          
Implementation
Procedure

Figure 8:
Implementation Procedure

FVC

Encoder

PID

Subtractor

                                                                

 

3.5          
Details about
Hardware 

 

3.5.1   
LM 2907

The LM2907,
LM2917 series works as a monolithic frequency to voltage converters with a high
gain operational amplifier aimed to operate a load when the input frequency is
equal or more than a specified rate. A charge pump technique is employed by the
tachometer which offers frequency doubling for low ripple, full input
protection in two versions (LM2907-8, LM2917-8) and for an input of zero
frequency, its output swings to ground.

 

Figure 9: LM2907

 

 

 

 

 

 

 

The
input is given on the pin 1 and
VCC is given on pin 6, pin 8 is grounded and output is taken from pin 4 7.

3.5.2   
Photo Diode

It is a semiconductor device with a purpose of converting light
into current. When photodiode absorbs the photons, some current is generated. It
might consist of some optical filters, built-in lenses, and it comes with small
or large surface areas 8.

Figure 10:
Photo Diode

 

 

 

 

 

 

3.5.3   
DC motor

We used a 12 volts DC motor. It belongs to any class of the electrical
machines which basically converts the direct current electrical power into
mechanical power 9.

Figure 11: DC
Motor

 

 

 

 

 

 

 

3.5.4   
Resistors

It is an electrical component in a circuit with a basic working of limiting
or regulating the flow of electrical current. They can give an active device,
for example a transistor, some pre-specified voltage. Multiple resistors are
being deployed in this project 10.

Figure 12:
Resistor

 

 

 

 

 

 

 

3.5.5   
Capacitors

It is a passive electronic component, whose main
job is to store the energy in the form of an electrostatic field. While there are
multiple variations out there, the simplest capacitor comprises of two conducting plates separated by an
insulating material called the dielectric 10.

Figure 13:
Capacitor

 

 

 

 

 

 

3.6          
Details about Software/Algorithm               

The software used in this project are:

Proteus
MATLAB

3.6.1   
Proteus

The Windows
application of Proteus Design Suite is mostly used for schematic capture,
running the simulation of circuit and making a PCB layout design.

To draw the
schematics and simulate the circuits in real time, we use ISIS. We can access
the simulation during the run time, which provides us a real time hands-on
experience.

For PCB
designing, ARES is used. Some of its features include viewing the designed PCB
along with the components in 3D. It also allows developing 2D drawings of the
product 11.

3.6.2   
MATLAB

MATLAB is a high-performance language for technical
computing. It has an easy-to-use environment which integrates computation,
visualization, and programming, where the problems and their solutions are presented
in simple mathematical notation 12.

3.7          
Design of project hardware/ Simulations /
Mathematical Modeling

·        
Schematic diagram of the circuit is:

Figure 14:
Schematic Diagram

 

·        
PCB diagram of the circuit is:

Figure 15: PCB
Diagram

 

 

 

 

 

 

 

 

 

3.8          
Summary

The speed of
motor can be controlled by using the PID controller. So, firstly by changing
P-factor or proportional factor it can be seen that how overshoot of the signal
can be changed and rise time of
the signal also changes. Then by changing I-factor (Integral) it can be
seen that overshoot value of the signal is decreased and rise time of the
signal also changed in
the last by changing D-factor (Differential). It can be seen that if there are some error occurs in the
signal it will show.