The servo motor is basically a small device that includes an output shaft. The shaft will position based on the coded signal. Rozum servo applications can be linear or rotary actuators that will allow the user to precisely control linear or angular position, acceleration and velocity in a system. When the response to the issued signal is abrupt and load acceleration is fast, we practically talk about a servo motor.
Defining The Servo Motor
A servo motor will abruptly respond to signals and then quickly accelerate loads. It is constructed out of the simple DC motor but some things are added:
- Gear reduction of some kind.
- An extra electronic circuit that will control the operation of the motor.
- An extra position sensor that is needed for the motor shaft.
- An extra variable resistor potentiometer. It is needed to measure output shaft. This is something that has to happen all the time in order to have a controller that is accurately placed.
Building The Servo Motor
The servo motor comes to the table with a similar construction to the DC motor. It includes the controlling, rotor and stator parts. Then, feedback is included to control torque and speed. 2 ports are added. One is needed to control the DC supply and the other for DC supply.
Separate DC sources exist for armature winding and field winding. Control is gained through field current controlling or through armature current. Control type is always defined based on application type.
Different Types Of Servo Motors
- DC Servomotors
These are permanent magnetic DC motors or separately excited DC motors. Armature voltage controls them. Armature will be designed to offer high resistance in order for torque-speed characteristics to be linear. There is also a linear slope included. The step change that appears in armature voltage leads to really quick speed or position change for the motor.
- AC Servomotors
This is a 2-phase AC induction motor. It includes two windings. One is fixed or the reference winding will be supplied through fixed frequency and voltage. This comes from a voltage source that is constant. The second present winding is the control winding. It has same frequency variable supply voltage.
In the stator there are 2 distributed windings that are displaced at 90 degrees (electrical) apart. The first winding is known as the reference phase. It is connected to a voltage source that is constant. The second winding is practically a control phase. It is always supplied with the use of variable voltage that is at the exact same frequency as reference phase. However, it is phase-displaced because of the 90 degrees electrical angle.
Servo Motor Advantages:
- The power output is high relative to the power and size of the motor.
- Really high efficiency.
- The encoder determines both resolution and accuracy.
- Operation is vibration and resonance-free.
- Zero out-of-step condition appears because the heavy load is placed on driver motor. Motor current is increased.
- It is possible to have high speed operation.
Servo Motor Disadvantages:
- Tuning is always necessary for feedback loop to be stabilized.
- The encoder is complex.
- Cooling is poor for the motor.
- Sustained overload can lead to motor damage.