servo types

[confusion]

when we say DC servomotor,

does it means motor with closed loop control, 0-180deg rotation, 3wire (V+ , GND & control), control by sending PWM? (i know this is RC type servo)

do all DC servo have the same characteristic? i mean closed loop, 0-180....

[Al_The_Man]

Servo control is not limited to 180deg, can be any multitude of rotations through 360.
Servo is positioning by means of a feedback device.
Al.

[routerman]

Your confusing Radio Control 'servo' actuators which move an arm depending on a pulse width signal, to a motion control servo motor which is a closed loop motor and encoder.
Not the same thing at all.

[confusion]

i see! i get what you mean now...
if i rephrase it
SERVOMOTOR = MOTOR + CLOSE LOOP + ENCODER
is it correct? and the MOTOR can be brushed, brushless.....

[confusion]

so, how does a motion control servo motor control its shaft position? (like a rc servo is by PWM)

does it has a typical or common method? or it depends on the design for different types of servo which have different position control mechanism?

[Al_The_Man]

Originally Posted by confusion i see! i get what you mean now... if i rephrase it SERVOMOTOR = MOTOR + CLOSE LOOP + ENCODER is it correct? and the MOTOR can be brushed, brushless.....

A motion device does not even have to be electric motor, hydraulic actuators with encoder/scale feedback and hyd servo valve is also used.
The drive amplifier and its associated technology i.e. PWM, SCR, Step/dir is invisible to the motion controller.
The control puts out a command to the drive and receives position feedback from an encoder for e.g.
Technically a mechanism can be classified as servo without feedback device, as long as it can faithfully follow the command.
This is open loop servo.
The encoder provides closed loop system.
Al.