rozważania o CNC

AC Servo principle

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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.

(http://www.markcomp77.p9.pl/img/ac01.jpg)

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

(http://www.markcomp77.p9.pl/img/ac02.jpg)




Servo driver Internal structure

(http://www.markcomp77.p9.pl/img/ac03.jpg)




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

(http://www.markcomp77.p9.pl/img/ac04.jpg)

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

(http://www.markcomp77.p9.pl/img/ac05.jpg)

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

(http://www.markcomp77.p9.pl/img/ac06.jpg)

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

(http://www.markcomp77.p9.pl/img/ac07.jpg)

-incremental encoder
-absolute encoder
-resolver

AC Servomotor

Generally, modern servo motor refers to AC permanent magnet synchronous servo motor.

Consisted by:
1.Stator windings + rotor
2.Feedback units: Photoelectrical Encoder /Resolver

Characteristics:
1.Maintenance free
2.Good environment adaptability
3.Good torque performance
4.Easier to brake
5.Smaller dimension, lighter weight
6.High efficiency

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Structure types

Stator: distribution winding /concentration winding

(http://www.markcomp77.p9.pl/img/ac10.jpg)

Strengths?Smaller cogging torque
Shortcomings: Complicated technique, low production for slope slot

(http://www.markcomp77.p9.pl/img/ac11.jpg)

Strengths?High power consistency, simple technique, high production
Shortcomings?Without slope slot, cogging torque control needed

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Rotor: Inner PM(IPM)/Surface PM(SPM)

(http://www.markcomp77.p9.pl/img/ac12.jpg)

Strengths: high reliability, simple technic
Shortcomings: rotor leakage flux and inductance control needed.


(http://www.markcomp77.p9.pl/img/ac14.jpg)

Strengths: low leakage flux and inductance
Shortcomings: PM protector needed.

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AC 750W servo motor structure characteristics: Concentration winding stator + IPM