Servo Motor Control


Thread Starter


Hi guys,

Can you output a predetermined pulse in GX developer to control a servo motor?
That's kind of an odd question. Here are a couple of possible answers:

- If using Q series hardware you can purchase pulse motion modules and program the trajectory and position and then trigger the moves.

- With any PLC you can use an output line to "trigger" a servo amp that has programmable moves (sometimes called indexer control).

- I believe many of the FX series can control one or two motors using specific high speed pulse and direction lines.

- Finally, the Q series has a fully functional motion control module that talks to Mitsubishi amps through their proprietary Fiber network, SSCNET.

All of the above methods have their own pros and cons depending on the application and your level of comfort. I wouldn't say any of the solutions are as flexible as a full featured dedicated motion controller. Like many things Japanese, the motion controller performs well spec-wise (motor response, settling, etc) but the software features are extremely register based and things like handling errors can be painful. Its not so bad when you have a handful of simple moves but try and do a lot of dynamic things like calculating position on the fly and you are stuck in register land having to keep track of 16bit and 32bit registers and strange scaling like inch units are programmed in 1e-5 units when dealing with registers but if you type them into a position block as a constant it is in floating point inches (with 5 digits to the right of the decimal since this is how they handle it under the hood). Things like that just make for a confusing experience. We tried the motion controller to get away from the Delta Tau PMAC complexity and at the end of the day it was just much different nagging complexity and in some cases we just couldn't do certain things that seemed trivial with other systems (Like following error is in units of integral motor rotations!!! No I'm not kidding!!) This is just my opinion, others may disagree.

Thank you for your insight.

That strange scaling is damn right confusing. Actually we will be using FX3U(C), and its brochure said it can control a servo motor. First I want to know what are the instructions/functions in GX Developer for controlling a servo motor? And the second part is how to integrate it to Omron servo driver.