Choosing Servo/Stepper Motor

[Guest Guest1]

Hi, Anybody know when should we use Servo motor or Stepper motor? Any criteria to take notes ? Under what conditions? Please advice . Thank you.

[panic mode]

Hi Guest, What does this have to do with Mitsubishi PLCs? I would put it either in "General" or "All other equipment" section. Stepper motor is much slower than regular servo. It is normaly used in simpler systems, usually where position errors are not critical (stepper without feedback - just open loop control). Feedback can be added of course but if you do, why use stepper? Steppers normaly have relatively high torque and position info is result of counting command pulses. Frequency of pulses controls the speed. Major downside is if you do encounter situation where motor does not follow commands (either accel/decel too high or the torque is too low). For exa,ple you issue 100 pulses but because they ware too fast stepper made only 80 steps instead of 100. The difference of 20 counts becomes the positionin error. It might be ok for say home printer because nobody cares about time you spend to print something and cost of one misprinted sheet of paper is low enough - but you don't want that to happen in certain applications (anything critical). Another thing to note is that steppers tend to resonate on certain frequencies and can get real problem. servo is the best but it might not fit the bill for some applications (specially bigger size). chako, where do you get these emoticons? i find them soo cool...