3. 1.DEFINITION
2.TYPES AND
CONSTRUCTION
3.WORKING
PRESENTATION 4.EQUIVALENT CIRCUIT
LAYOUT 5.CONTROLS
6.USES
7.ADVANTAGES AND
DISADVANTAGES
4. 2.TYPES AND 4.EQUIVALENT
1.DEFINITION CONSTRUCTION
3.WORKING
CIRCUIT
7.ADVANTAGES &
5.CONTROLS 6.USES
DISADVANTAGES
1.DEFINITION:
A servomotor (servo) is an electromechanical device in
which an electrical input determines the position of the
armature of a motor. Servos are used extensively in
robotics and radio-controlled cars, airplanes, and boats.
5. 4.EQUIVALENT
1.DEFINITION 3.WORKING
2.TYPES AND CIRCUIT
5.CONTROLS
CONSTRUCTION 6.USES
7.ADVANTAGES &
DISADVANTAGES
2.TYPES AND CONSTRUCTION:
TYPES:
There are two main types of servo motor:
1. Linear servo motor
I. Brush DC
II. Brushless DC
2. Rotary servo motor
I. Brush DC servo motor
II. Brushless DC servo motor
6. 4.EQUIVALENT
1.DEFINITION 3.WORKING
2.TYPES AND CIRCUIT
5.CONTROLS
CONSTRUCTION 6.USES
7.ADVANTAGES &
DISADVANTAGES
2.TYPES AND CONSTRUCTION:
TYPES:
1. LINEAR SERVO MOTOR:
A linear servo motor is a flattened out Servo Motor where the
rotor is on the inside, and the coils are on the outside of a
moveable u-channel
7. 4.EQUIVALENT
1.DEFINITION 3.WORKING
2.TYPES AND CIRCUIT
5.CONTROLS
CONSTRUCTION 6.USES
7.ADVANTAGES &
DISADVANTAGES
2.TYPES AND CONSTRUCTION:
TYPES:
I. Linear Brush DC:
1. The brushed linear servo motor is designed for long stroke servo applications. It
is ideal for direct linear motion without mechanical linkages in closed-loop
position packages.
2. The moving permanent magnet brush commutated DC linear motor consists of a
stationary primary and a moving secondary.
3. The stationary primary is a steel laminated core, with multiple coils inserted into
insulated slots. The ends of each coil are connected to a commutator bar that is
mounted on an aluminum angle.
4. The moving secondary features multiple permanent magnets and brushes for
commutation. A cable supplies power to the moving secondary. Mounting holes
are located on both the primary and secondary.
5. The magnetic-attractive force between the primary and secondary can be used as
a magnetic preload for the bearing system.
6. The customer-supplied bearing system must maintain an air gap of 0.064 cm
[0.025 inch] between the primary and secondary. The brush linear motor is
available in different cross sections to meet different force requirements.
8. 4.EQUIVALENT
1.DEFINITION 3.WORKING
2.TYPES AND CIRCUIT
5.CONTROLS
CONSTRUCTION 6.USES
7.ADVANTAGES &
DISADVANTAGES
2.TYPES AND CONSTRUCTION:
TYPES:
2.Linear BrushLess DC :
Brushless needs AC 3 phase supply for working.But some
Brushless DC also available, for these motors electronic circuitry is
available to provide 3 phase supply.
9. 4.EQUIVALENT
1.DEFINITION 3.WORKING
2.TYPES AND CIRCUIT
5.CONTROLS
CONSTRUCTION 6.USES
7.ADVANTAGES &
DISADVANTAGES
2.TYPES AND CONSTRUCTION:
TYPES:
2.Rotary servo motor:
A rotatory servomotor is a rotatory actuator that allows for
precise control of angular position.
10. 4.EQUIVALENT
1.DEFINITION 3.WORKING
2.TYPES AND CIRCUIT
5.CONTROLS
CONSTRUCTION 6.USES
7.ADVANTAGES &
DISADVANTAGES
2.TYPES AND CONSTRUCTION:
TYPES:
2.Rotary servo motor:
1.Rotary brush DC servo motor:
11. 4.EQUIVALENT
1.DEFINITION 3.WORKING
2.TYPES AND CIRCUIT
5.CONTROLS
CONSTRUCTION 6.USES
7.ADVANTAGES &
DISADVANTAGES
2.TYPES AND CONSTRUCTION:
TYPES:
2.Rotary servo motor:
2.Rotary brushless DC servo motor:
12. 2.TYPES AND 4.EQUIVALENT
1.DEFINITION 3.WORKING
CONSTRUCTION CIRCUIT
7.ADVANTAGES &
5.CONTROLS 6.USES
DISADVANTAGES
3.WORKING:
1. The servo motor has some control circuits and a potentiometer (a variable
resistor, aka pot) that is connected to the output shaft.
2. The potentiometer allows the control circuitry to monitor the current angle of
the servo motor. If the shaft is at the correct angle, then the motor shuts off.
3. If the circuit finds that the angle is not correct, it will turn the motor the correct
direction until the angle is correct.
4. The output shaft of the servo is capable of travelling somewhere around 180
degrees. Usually, its somewhere in the 210 degree range, but it varies by
manufacturer.
5. A normal servo is used to control an angular motion of between 0 and 180
degrees. A normal servo is mechanically not capable of turning any farther due
to a mechanical stop built on to the main output gear.
6. The amount of power applied to the motor is proportional to the distance it
needs to travel.
7. So, if the shaft needs to turn a large distance, the motor will run at full speed. If
it needs to turn only a small amount, the motor will run at a slower speed. This
is called proportional control.
13. 2.TYPES AND 4.EQUIVALENT
1.DEFINITION 3.WORKING
CONSTRUCTION CIRCUIT
7.ADVANTAGES &
5.CONTROLS 6.USES
DISADVANTAGES
3.WORKING:
1. The control wire is used to communicate the angle.
2. The angle is determined by the duration of a pulse that is applied to the control
wire. This is called Pulse Coded Modulation.
3. The servo expects to see a pulse every 20 milliseconds (.02 seconds). The
length of the pulse will determine how far the motor turns.
4. A 1.5 millisecond pulse, for example, will make the motor turn to the 90 degree
position (often called the neutral position).
5. If the pulse is shorter than 1.5 ms, then the motor will turn the shaft to closer to
0 degrees.
6. If the pulse is longer than 1.5ms, the shaft turns closer to 180 degrees.
14. 1.DEFINITION
2.TYPES AND
3.WORKING 4.EQUIVALENT
CONSTRUCTION
CIRCUIT
7.ADVANTAGES &
5.CONTROLS 6.USES
DISADVANTAGES
4.EQUIVALENT CIRCUIT:
15. 2.TYPES AND 4.EQUIVALENT
1.DEFINITION 3.WORKING
CONSTRUCTION CIRCUIT
7.ADVANTAGES &
6.USES
5.CONTROLS DISADVANTAGES
5.CONTROLS:
Control Pulse :
Control pulse is referred to the type of pulse used to
position the shaft. Two main types of control pulses used in
RC applications: center position in 1-2 ms and 1,25-1,75
ms.
for Servos
For servos pulse width modulation does not control power but
instead
sends information. In this case the frequency is 50 hz
corresponding to
a period of 20 ms, the pulse is varied from 1 ms to 2 ms. The
pulse
width represents the amount of rotation we want from the servo.
( The
duty cycle is from 2% to 4% for a servo. )
16. 2.TYPES AND 4.EQUIVALENT
1.DEFINITION 3.WORKING
CONSTRUCTION CIRCUIT
7.ADVANTAGES &
6.USES
5.CONTROLS DISADVANTAGES
5.CONTROLS:
Control Pulse :
Arduino and Pulse Width Modulation
There are many ways to do pulse width modulation with an arduino.
These fall into 2 classes, hardware assisted and straight software.
Hardware
The arduino hardware includes a unit that will produce pulse width
with essentially one command, and keep doing it with no attention
from the program. However this is easiest if the frequency is kept to
about 500 Hz and with 256 divisions of the duty cycle ( in about .004
percent steps ). It is not really useful for servos as the frequency is not
right and the control over the 1 to 2 ms range is not very high.
Software
Software modulation keeps the controller busy but allows pretty much
any frequency and duty cycle within a few micro seconds. It can fail if
the controller gets too busy, and it can be hard for the controller to do
other things at the "same time“
17. 2.TYPES AND 4.EQUIVALENT
1.DEFINITION 3.WORKING
CONSTRUCTION CIRCUIT
7.ADVANTAGES &
6.USES
5.CONTROLS DISADVANTAGES
5.CONTROLS:
Feed back control:
18. 2.TYPES AND 4.EQUIVALENT
1.DEFINITION 3.WORKING
CONSTRUCTION CIRCUIT
7.ADVANTAGES &
6.USES
5.CONTROLS DISADVANTAGES
5.CONTROLS:
Proportional Integral Derivative (PID) controllers:
PID Controller is a feed-back loop unit in the industries
control. The controller receives the command, subtracts it
with the actual value to create a “difference”. This
difference is then used to calculate a new input value
which allows the data of system to achieve or maintain at
the reference value. PID Controller. A PID feedback loop
can maintain the system stability, but other control
methods may lead to system that have stability errors or
repeated process.
19. 2.TYPES AND 4.EQUIVALENT
1.DEFINITION 3.WORKING
CONSTRUCTION CIRCUIT
7.ADVANTAGES &
5.CONTROLS
6.USES DISADVANTAGES
6.Uses:
1. In industry Robots
2. Inkjet printers
3. RC helicopters
4. Toys
20. 2.TYPES AND 4.EQUIVALENT
1.DEFINITION 3.WORKING
CONSTRUCTION CIRCUIT
5.CONTROLS 6.USES 7.ADVANTAGES
&
7.Advantages & Disadvantages: DISADVANTAGES
Advantages:
the low energy requirements (efficiency), the high torque,
TTL voltage level control, and even the physical properties –
servo motors are relatively small sized and have a low
weight.
Disadvantages:
1) Requires "tuning" to stabilize feedback loop.
2) Motor "runs away" when something breaks. Safety circuits required.
3) Complex. Requires encoder.
4) Brush wear limits life to 2,000 hrs. Service is then required. This system
causes friction between the brush and commutator, which requires replacing
and maintenance
5) Peak torque is limited to a 1% duty cycle.
6) Motor can be damaged by sustained overload.
7) Bewildering choice of motors, encoders, servo drives.
8) Power supply current 10 times average to use peak torque. See (5).
9) Motor develops peak power at higher speeds. Gearing often required.
10) Poor motor cooling. Ventilated motors are easily contaminated.
