replace servo motor with induction motor + encoder

[tingxing 1]

Hello, I wonder if in some cases servo motor can be replaced with induction motor + encoder. Because my primary concern is position accuracy, if the encoder is accurate enough, can stop position be adjusted anyway? I dont care much about speed. I expect to cut some cost by using this configuration. Thanks in advance. Ting

[ParaffinPower 13]

Hello Ting You can achieve excellent results with a flux-vector inverter (the 3G3RX family as you're posting in the Omron forum). It has built-in positioning and may do what you need. You need the additonal encoder card (3G3AX-PG01) I've used it by sending a position command (Modbus), although you can store 8 positions in the inverter, and select them with a binary pattern of inputs It can also use pulse and direction as a position command too; similar to a SmartStep. You'll need an encoder on your motor shaft, and possibly a force-vent fan for cooling. The 3G3MX2 inverter can do positioning, but it's open-loop so the positioning results aren't as good. Pp

[tingxing 1]

Thank you very much! I am new to inverter. Our current configuration depends on the encoder feedback to understand the position. I am afraid your recommendation might be expensive. Previously Servo was used, and position control seemed not to be a problem. when we begin to use an induction motor, position problem arises probably due to rotation can not stop immediately. A solution is to use other motors with "brake" function. But , I think this wont be necessary, because it seems we can compensate the error. 1 degree resolution is good enough, but now we are using E6C3-A, with 1024 divisions. Is E6C3A enough? Ting

[ParaffinPower 13]

You can't stop a motor instantly. You can slow down when you're 'near' then stop on the target, which is better. I don't know if 1024 pulses are enough. How are you controlling position? You're results will never be as good as closed loop.

[tingxing 1]

Thank you! My position control is realized only by reading the feedback from encoder. Just as you pointed out, slow down near the stop is a solution. Though not as good as closed loop, correction can be done according to encoder feedback, which might be just a kind of "close loop". 1024 pulse might be good enough - if 1 degree is necessary, 1024 division offers 360/1024= 0.35 degree resolution. where can I find some tutorial like materials so as to know how to use the devices(inverter) you recommended? Ting

[markjosol 0]

'near' then stop on the target, which is better. ______________________________________________ FIFA 14 Coins