This the field of electronic, robotics and automation system,

This Chapter is about literature review of our project. DC motors are widely used in many applications that we use in our
daily life. They can be found everywhere, from house appliances to our
vehicles, desktops and laptops, and industrial applications such as production
lines, remote control airplanes, automatic navigation systems and many other
applications.

There are two types of positional rotation servo motor which are DC
servo motor that is controlled by DC, and Alternating Current (AC) servo motor
which is controlled by AC. The servo motor “internal” positional feedback
consists of either encoder feedback or voltage feedback.

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The built-in encoder inside the servo motor provides a pulse signal that
is processed by the servo controller to get the position feedback. The voltage feedback
consists of a built-in potentiometer which is coupled with the servo motor axis
to get the relative angular position depending on the value of the
potentiometer. In particular, the DC servo motor is mostly utilized in the
field of electronic, robotics and automation system, especially for special
types of applications where the rotation of the motor only requires a certain
angular movement such as for robot arm, robot gripper, and etc.

 

2.1    Historical
Background

 

Electric
motors came to fruition due to the invention of the battery (A. Volta, 1800),
the electro magnet (W. Sturgeon, 1825) and the discovery of a magnetic field
from electric current (H. C. Oersted, 1820). The first working rotating
electric motor was introduced in May 1834 by Moritz Jacobi. In 1838, Jacobi
reintroduced an improved and more powerful motor. However, these electric
motors were large and weak compared those we use today. Servo motors works
within a closed-loop control system. These motors provide precise control of
position (angular or linear), velocity, and acceleration. These devices are rarely
seen  but an average person uses them
daily : The sliding doors at the supermarket; the power windows in a car; the
elevator at the office, and the ice delivery system on a refrigerator. Servo
motors are so sophisticated that they are used in robotic manufacturing, such
as those used to assemble automobiles. 3

 

2.2    Types of Servo
Motor

These
motors are classified into different types based on their application like
Brushless DC, AC, continuous rotation, linear and positional rotation, etc. 4

2.2.1  DC Servo Motor  

 

Generally, this
motor has a distinct DC source in the winding and the armature winding field.it
can be controlled by adjust the field or armature current. Field control has some
profits over armature control. Similarly, armature control comprises some
benefits over field control

 

 

2.2.2  Synchronous DC
Motor

 

Encoder which is
used with
controllers in this motor for giving closed loop control and also response.
This motor works to high accuracy and also controlled exactly as required.
Often these motors have advanced designs of patience or better bearings and
some simple designs also achieve greater torque on higher voltage. 

 

2.2.2.1 Positional Rotation Servo
Motor

This is a most common type of motor and the
o/p of the shaft rotates in about 180. It encompasses physical stops situated
in the gear device to stop rotating outside limits to defend the rotation
sensor.

 

2.2.2.2 Continuous Rotation Servo
Motor

the common positional rotation servo motor
is linked up with this motor and it can move in any direction indefinitely. As
per the speed & direction of rotation, the control signal rather than set
the stationary position of the servo is expected.

 

2.3    Limitations

 

·         
Since the servomotor tries to
rotate according to the command pulses, but lags behind, it is not appropriate
for accuracy control of rotation.

·         
Higher cost.

·         
When stopped, the motor’s rotor
continues to move back and onward one pulse, so that it is not appropriate if
you need to prevent vibration.

 

2.4    Summary

 

This chapter presented the literature review of
servo motor Controller, and the project and research that are related to
Controller have been reviewed. The limitations  of servo motors controllers have been
outlined.