"ordinary" DC motor vs DC "servo" motor?
Bookmark this page:
 Yahoo!
 Google
 Windows Live
 del.icio.us
 digg
 Netscape
|
|
||||||||||||||||||||||
|
Posted by on October 13, 2004, 5:12 pm
Please log in for more thread options "servo" motor? Does adding a quadrature encoder to the ordinary DC motor convert it to a DC sevo motor? | ||||||||||||||||||||||
|
Posted by John Popelish on October 13, 2004, 11:47 am
Please log in for more thread options Ordinary brush type DC motors come in several flavors. Series wound motors (also called universal wound because they can run on AC) have the field windings wired in series with the armature, so that the torque produced is proportional to the square of the current (the armature current reacts against the equal field current). Since these produce torque in the same direction, regardless of the direction of current (hence the usability on AC). So these are not usable as servo motors. Shunt wound motors have the field winding either wired in parallel with the armature, or excited by a separate current, entirely. The separately excited shunt wound motors can be used as servo motors, since their torque is essentially proportional to armature current and their speed is approximately proportional to armature voltage. Permanent magnet field motors are very similar in character to separately excited wound field motors, since their field's magnetic strength is not related to armature current. They are commonly used as servo motors. Any motor that can produce torque in either direction can, in theory, be made into a servo motor if you can measure its speed to be used by the servo loop controller. Being able to measure the torque is very handy, also, so motors that have torque proportional to armature current make this easy. Strictly speaking, a servo is a motor application, not a type of motor. -- John Popelish | ||||||||||||||||||||||
|
Posted by peterken on October 13, 2004, 7:11 pm
Please log in for more thread options Ordinary brush motors are just motors starting to turn when a voltage is
applied Stepper motors can be indicated to be servo motors http://www.seattlerobotics.org/guide/servos.html On the other hand, also ordinary motors may be indicated to be servo motors, depending on their application http://www.aptronix.com/fuzzynet/applnote/servo.htm Also more generic info at: http://users.telenet.be/educypedia/electronics/motorservo.htm As stated above, depending on their application adding an encoder *might* turn an ordinary motor into a servo motor <DCServoMotor> wrote in message
What is the difference between a brush type "ordinary" DC motor and DC
"servo" motor? Does adding a quadrature encoder to the ordinary DC motor convert it to a DC servo motor? | ||||||||||||||||||||||
|
Posted by Eric R Snow on October 13, 2004, 12:58 pm
Please log in for more thread options wrote:
>Ordinary brush motors are just motors starting to turn when a voltage is
Another requirement of a servo motor used for precise postioning is
>applied > >Stepper motors can be indicated to be servo motors >http://www.seattlerobotics.org/guide/servos.html > >On the other hand, also ordinary motors may be indicated to be servo motors, >depending on their application >http://www.aptronix.com/fuzzynet/applnote/servo.htm > >Also more generic info at: >http://users.telenet.be/educypedia/electronics/motorservo.htm > >As stated above, depending on their application adding an encoder *might* >turn an ordinary motor into a servo motor > > ><DCServoMotor> wrote in message >What is the difference between a brush type "ordinary" DC motor and DC >"servo" motor? >Does adding a quadrature encoder to the ordinary DC motor convert it to a DC >servo motor? > > it's predictable and consistent response throughout it's operating range. So if it is poorly built it may react to the same voltage and current differently as it spins. This means that the motor may pulse as it spins. It is very hard to control the motor when it acts this way. Modern motors are often built very well because the methods used in production require repeatability. So even cheap motors can often be used as servos if feedback is used. Especially if the application is not very demanding. The servos used for RC models use a potentiometer for position feedback and these devices are inexpensive and robust considering what they cost. ERS | ||||||||||||||||||||||
|
Posted by Mikal Hodvik on October 13, 2004, 11:55 pm
Please log in for more thread options I'm no expert on this, but I'm under the impression that it's primarily LOW
INERTIA that distinguishes a servomotor from the ordinary. Cheers, Mikal Hodvik <DCServoMotor> wrote in message
> What is the difference between a brush type "ordinary" DC motor and DC > "servo" motor? > Does adding a quadrature encoder to the ordinary DC motor convert it to a > DC sevo motor? > > | ||||||||||||||||||||||
| Similar Threads | Posted |
| "ordinary" DC motor vs DC "servo" motor? | October 13, 2004, 5:12 pm |
| Motor Drivers vs Motor Controllers | August 16, 2006, 2:11 pm |
| -- Magnetic motor 1, the static magnetic field 1) Motor | October 2, 2006, 2:50 pm |
| 1 -- Motor magnetic field, static magnetic field 1) motor | November 24, 2006, 12:34 pm |
| DC motor | December 3, 2004, 11:33 am |
| DC motor | April 19, 2005, 6:42 pm |
| DC motor help | April 27, 2005, 1:21 am |
| 50 hz motor on 60 hz | May 12, 2006, 9:26 pm |
| 0.5 rpm motor | October 7, 2007, 9:24 am |
| Fan Motor | April 21, 2008, 11:47 am |
| DC Motor overvoltage | August 19, 2004, 8:16 pm |
| electric motor | September 22, 2004, 2:15 pm |
| How do I hook up 5 hp motor | November 28, 2004, 8:37 pm |
| DC motor controller 24 V, 30..50 A | January 31, 2005, 11:14 pm |
| PWM for a high amp motor? | February 15, 2005, 2:48 am |
> What is the difference between a brush type "ordinary" DC motor and DC
> "servo" motor?
> Does adding a quadrature encoder to the ordinary DC motor convert it to a DC
> sevo motor?