Stepper control w/CJ1M CPU22

[garagon 0]

I am a self taught PLC programmer working in the textile industry. I have programmed a few Omron PLC's, i.e. CQM1's, CJ1M's, CPM1A, to control manufacturing machinery to different processes. I have recently been asked to construct an XY cutting table using stepper motors, a touch screen and two MCG Stepper drives with encoders attached to the stepper motors. We would like to position the cutting head with a joystick and imput the size of the cut on the touchscreen. I would also like to do a compare before the cut cycle to see if there is sufficient room on the table to make a successful cut. I have not had any experience with stepper control from a PLC, and I am having a bit of trouble getting started on the motion control section of the ladder program. We purchased a CJ1M CPU22 and an NS5 Touchscreen, along with MCG stepper drives. Any help would be greatly appreciated.

[BITS N BYTES 66]

For starters go to this link. http://forums.mrplc.com/index.php?act=Downl...&CODE=02&id=268 Very helpful to get the motion working!! Hope this helps.

[Jay Anthony 118]

Unfortunately, I already sent him to this link over at PLCs.net. He says he needs more basic support like hookups, wiring, etc....

[Nibroc 4]

Hi... Where do you intend to connect the encoders? - the CJ1M built in I/O pulse output system is not designed for closed loop control - ie the pulse outputs for controlling the steppers do not require encoder feedback. Note that the stepper motor should rotate a 'discrete' amount for each pulse output from the PLC. It should not be necessary to use feedback encoders with the CJ1M as the PLC can keep track of each axis 'position', although you will need to be careful how you program the joystick operation. However I think this is possible. You will need to run 'absolute' positioning, this will allow the PLC to 'know' where the physical limits are at all times. Hence the PLC 'can calculate if there is sufficient room for a cut'. The System will need to perform an 'Origin' Search occasionally, this functionality is built in to the CJ1M. Some difficulty may be in keeping track of the absolute position juring joystick operation. Although I can think of a couple of ways to do this. What type of Joystick do you intend - digital / analog ? Probably a Digital Joystick would be the choice for this application. ... Nibroc

[BITS N BYTES 66]

Good call Nibroc! The stepper outputs on the CJ1M series are just that. OUTPUTS! Whether the motion commands in the program are "absolute" or "relative" the PLC only "thinks" it knows where it is. Providing there are no missed steps in the stepper drive then that's OK. Some stepper drives are capable of operating in closed loop mode by using the encoder feedback from the stepper motor. The stepper drive can be configured to provide an output signal to the PLC and/or declare a position fault if the position error is too great. Another method would be is to connect the encoders to the high speed counter inputs on the base CJ1M PLC. After an initial homing [origin search] routine is performed the PLC knows the position [as long as it is powered up!]. [For encoder hookups see the Omron OPERATION MANUAL Cat. No. W395-E1-03 CJ-series Built-in I/O CJ1M-CPU21/22/23 CJ1M CPU Units]. After an initial homing [origin search] routine is performed the PLC knows the position [as long as it is powered up!]. You could of course do both the above and you would really have a tight system!

[garagon 0]

Gentlemen, All good information, thanks. I will be using a digital joystick and the encoders will be hooked up to the built-in high speed counters. Again, guys, thanks for reading and responding to my post. garagon