[Miss. Ori, Manager]
How should we differentiate the usage of Stepping Motor and AC Servo Motor ?
[Mr. Vex, Staff]
Mr. Vex: Look, Miss Ori, i got a request from product selection from our customer.
Miss Ori: Oh keep it up, vex! So how is the selection coming along?
Mr. Vex: Well, that is why i need your advice. I believe i should recommend stepping motor or servo motor since it is for positioning. But i am just not certain which one i should recommend.
Miss Ori: Hmm what is the mechanism? How about the driving pattern?
Mr. Vex: Conveying work by belt-pulley system. Both travel and positioning time are very short. For such cases, do you think i should recommend servo motor as it has better advantage in high speed operation?
Miss. Ori: It did sounds like stepping motor is a better choice
It did sounds like stepping motor is a better choice (Figure 1)
servo motor has smaller load inertia compared to stepping motor, therefore it is not suitable for system with larger load inertia, eg belt pulley mechanism. When Servo motor is used, you must used it's response according to the load inertia which is called 'gain adjustment'. But for systems with large load inertia, like belt-pulley, the response can not be raised.
Mr. Vex: Hmm,but if the work is lesser, inertia moment is inevitably smaller, then response could be raised for better performance even in the belt-pulley system, couldn't it?
Miss. Ori: You see in the belt-pulley system, the belt is constantly stretched or shrunk. The load inertia is very unstable for such low rigidity system and that is why gain adjustment is very difficult..
Mr. Vex: Really? i did not know that there is something that outperformed servo motors!.
Miss. Ori: Indeed stepping motor take less trouble for machine implementation as it can be used without the hassle of gain adjustment.
Mr. Vex:I see!
Miss. Ori:Additionally, both travelling and positioning time are shorter, servo motor's control time for monitoring motor operation by executing closed loop control will caused "delay", but you don't have to worry about the "delay" for the stepping motor as it operates simultaneously with pulse signals.
Mr. Vex:So it should not be selected with motor characteristics alone with characteristics of system such as rigidity as well, right?
Miss. Ori: Absolutely. It is better considering these facts when you select a motor.
Mr. Vex:I understand, Ms Ori explanation is always clear!