AC Servo principle
What is a Servo?A servo is a device which controls the angle of a piece of machinery. A motor attached to the servo controls a rotating shaft which changes the angle of the shaft. Servo originates from Latin
Servus. (English as
Slave)
The function of a
Slave is to work with loyalty under his lord?s orders.

Servo system can be briefly classified into following parts:
1.Order part?Movement instruction signal output device.
2.Drive part?A device that receives the output signal from the Order part and drives the execution machinery. ( e.g. servo motor)
3.Feedback part?A device that inspects execution machinery or load status.
4.Execution machinery: A device that receives the output signal from Drive part and generates rotation torque, position status etc.,
AC servo system control structure
Servo driver Internal structure
Servo motor could be classified as follows:Synchronized type: Applied with PM servo motor. Because of power generation effect when stops, it is easier to brake. (Rotator:
PM Stator: Windings)
Inductive type: The structure is like synchronized type servo motor. It has good torque performance at high speed. However, it is easier to generate heat. (Rotator & stator: windings)
DC type: DC servo motor. As carbon brush will generate powder while rotation, it is not suitable for locations with dust-free
requirement. It is mainly used for small capacity. (Rotator: windings; Stator: PM)
Synchronized AC servo motor
Characteristics:1.Maintenance free
2.Good environment adaptability
3.Good torque performance
4.Easier to brake
5.Smaller dimension, lighter weight
6.High efficiency
Shortcomings:1.AMP is more complicated than DC?s
2.Motor could only be driven with relevant power AMP.
3. PM is possible to demagnetize
Inductive servo motor
Characteristics:1.Maintenance free
2.Good environment adaptability
3.Good torque performance
Shortcomings:1.Low efficiency
2.AMP is more complicated than DC?s
3.No DB brake
4.Performance will be effected by temperature
5.Motor could only be driven with relevant power AMP.
DC servo motor
Characteristics:1.Driver structure is simple.
2.DB brake
3.Smaller in volume, low price.
4.High efficiency
Shortcomings:1.Carbon brush will generate powder.The refore, it cannot be used in locations with dust-free requirement.
2.Poor torque performance at high speed.
3. PM is possible to demagnetize
Motor feedback parts
-incremental encoder
-absolute encoder
-resolver