DC MOTOR SPEED CONTROL USING P.

I CONTROLLER
SHADAB.N. SAYYAD

Department of Electrical Engineering, Government college of engineering, Aurangabad (M.S.),

MR. W. Gavhane
Professor, Department of Electrical Engineering, Government college of engineering, Aurangabad
(M.S.), India

Abstract:

DC motors are used in numerous industrial applications like servo systems and speed control
applications. For such systems, the Proportional + Integral controller is usually the controller of
choice due to its ease of implementation, ruggedness, and easy tuning. An optimal PI Controller for
speed controller of DC Motor using tuner method proposed towards transition model to provide
better performance over the usual case. The Motor which converts electrical to mechanical energy
with the speed markup ranges the controller provide a necessary operation to provide a speed
control strategy to meet at desired value. The objective to gain the speed performance with the time
response is an attempt to achieve at stable speed range to get less loss errors and model analysis
performance. The main objective of this paper is to minimize transient response specifications
chosen as rise time, settling time and overshoot, for better speed response of DC motor drive. The
speed control of DC motor is done using PI controller.

Keywords: DC motor, PI controller, MATLAB etc.

Introduction:

In this modern industrial age, there is hardly any industrial application in which DC motors are not
being used . This is so because of ease of control, low cost maintenance especially of brushless DC
motor type, low price, and ruggedness of DC motor over a wide range of applications. Some indus-
trial applications, which are worth mentioning, in which DC motors are being used widely are ma-
chine tools, paper mills, textile industry, electric traction, and robotics. The flexibility in controller
design of DC motors is due to the fact that armature winding and field winding could be controlled
separately . In most of the applications of speed control of DC motors, the current in field winding
is kept constant and the current in armature winding is varied or vice versa which gives excellent
speed control performance over a wide range of desired values. In these applications, the purpose is
to track the speed command by keeping output speed at desired level and to achieve desire speed or
position control in minimum time without having large overshoots and settling times .

There are different types of controllers like lead, lag, LQR (linear quadratic regulator), PI, and slid-
ing-mode control that could be incorporated in control applications. Among the few mentioned
types of controllers, PI controller is one of the earliest and best understood controllers which is in-
corporated in almost every industrial control application due to its efficiency and ease of imple-
mentation . Although there are many classical techniques for designing and tuning PI controller
parameters  which are widely understood and easily applied, one of the main disadvantages of these
classical techniques is that, for tuning PI controller through these techniques, expertise and experi-
ence are required. This is so because these methods provide a starting point and achieving desired
performance fine tuning of parameters through hit-and-trial method is required. However, meta-
heuristic techniques may be a good choice to its dynamic nature.

System developed:

Figure 1: simulation block Diagram

Working:

In this activity we will design and implement a speed controller for a simple DC motor. In particu-
lar, we will choose and tune the gains of a PI controller based on the effect of the gains on the sys -
tem's closed-loop poles while accounting for the inherent uncertainty in our model. We will design
the controller to achieve a desired level of transient response and will examine in detail the steady-
state error produced by the resulting closed-loop system, including in the presence of a constant dis-
turbance.
The purpose of this activity is to build intuition regarding the design and implementation of a PI
controller for the speed control of a DC motor in the presence of an array of real-world
complications. Specifically, we will consider how to design the controller when we have an
uncertain plant model and are limited in the amount of control effort we can supply. Furthermore,
we will analyze our system's performance in the presence of unwanted exogenous inputs, which in
this case will be a constant disturbance.

PI controller
P.I Controller is a feedback control loop that calculates an error signal by taking the difference
between the output of a system, which in this case is the power being drawn from the battery, and
the set point. The set point is the level at which we’d like to have our system running, ideally we’d
like our system to be running near max power (990W) without causing the limiter to engage.
It is important to point out that due the the complexity of the electronic components within the cir-
cuit path ( i.e ESC, power limiter, and motor) I was not able to accurately create model (transfer
function) for the system. Having a transfer function would have allowed me to simulate the system
in a software package such as MATLAB/Simulink and assist me in finding the right proportional
and integral constant parameters for the controller. Unfortunately, due to the lack of a model, the
parameters were obtained via a trial and error format.

Figure 2

The figure shows  a software level block diagram of the P.I control algorithm. The controller
receives a current and voltage measurement which it then uses to calculate the power being drained
from the battery.  Once the power is measured the error signal is calculated by taking the difference
between the set point and the power measured. The error signal then goes into the P.I control loop
where it gets multiplied by the proportional and integral constant.  The output of the P.I control is a
power value and in order to convert it to a quantity that is comparable to that of the control signal, it
goes through a power to PWM signal converter. The adjusted PWM signal ( output of PWM
converter) then gets compared with the throttle signal, which is also a PWM signal,  that is being
sent by pilot ,the least of the two gets sent to the controlled system. The controlled system block
encompasses the battery, motor, speed controller, and limiter.

Figure 3

Conclusion:
Accurate performance of a motor is desired feature for any industrial application. As the age of
motor increases its performance also deceases with aging, so it is desired to evaluate the
performance of motor from time to time for efficient operation The conventional method for
calculating output performance indices are quite time consuming. The PI based approach algorithm
worked satisfactory for the test system. The important observations made during the studies are
1) The solution time for proposed PI approach is only a fraction of time taken by conventional
algorithm.
2) A proportional controller Kp will have the effect of reducing the rise time and reduce but never
eliminate the steady state error.
3) An internal controller Ki will have the effect of eliminate the steady state error but it may make
the transient response worse.
4)A derivative controller Kd will have the effect of increasing the stability of the system and
reducing the overshoot and improve the transient response.
5)The output performance obtained by normalized value in PI is very close and near to accuracy.
6)MATLAB used for simulation of entire project is sophisticated and user friendly software. It must
be mentioned that the efficiency of the speed algorithm can be improved by using more efficient
learning techniques and dynamic weight selection algorithm

Reference:
[1] Fatiha Loucif “DC Motor Speed Control Using PID controller” depatment of electrical engg
and information, hunan university, Changsha, hunan, china(E-mail: fatiha2002@msn.com) in june
2-5 KINTEX, Innovative Systems Design and Engineering www.iiste.org ISSN 2222-1727 (Paper)
ISSN 2222-2871 (Online) Vol.4, No.6, 2013 - Selected from International Conference on Recent
Trends in Applied Sciences with Engineering Applications 28 Gonggi, kora in ICCAS2005
[2] Guoshing Huang, Shuocheng Lee Department of Electronic Engineering, National Chin-Yi
University of Technology, 35, Lane 215, Chung-Shan Rd., Sec. 1, Taiping, Taichung, Taiwan,
41111, ROC E-mail:hgs@ncut.edu.tw in PC-based PID Speed Control in DC Motor 2008 IEEE
page no 400-407
[3] Saffet Ayasun, Gu¨ Ltekin Karbeyaz Department of Electrical and Electronics Engineering,
Nigde University, Nigde 51100, Turkey 12 March 2007 Wiley Periodicals Inc
[4] Electrical machine by Dr.P S Bimbhra by Khanna publishers New Edition
[5] Automatic control systm by S Hasan saeed, published by S K Kataria vol vi
[6] Control system engineering, by Nagrath & Gopal, published by New Age International
publishers Fifth Edition