Controling Axis1 Speed with Virtual Axis & MAG instruction

I am very new to programming Motion and am able to program a motor to spin (not that I understand all the parameters). The training kit that I am working with has a potentiometer that I have programmed to change the speed. However, this is not done "live." When the speed changes, in order for the motor to react you must re-push the start button.

I heard that you can use a virtual axis with a Motion Axis Gear instruction to control the Axis1 speed by making the virtual axis the "master". However, the error bit on my MAG instruction is constantly true. I have changed around some of the inside parameters to no avail. When programming, I referenced the Motion Reference Manual from the Rockwell website.

Can anyone give me some tips or ideas? I am really just doing this for my own benefit. My program is very simple, features MAH, MAS, and MAJ.

A couple comments (without seeing your program, I can't do much more).

1. A servo does exactly what it's told to do. If you tell it to Jog at a particular speed, it will jog at that speed until told to do something else. The jog command executes exactly once when the command goes true. Turning the MAJ false does not stop the motor from jogging - you must send a stop command. Similarly, if you want to change speeds, you need to give it another command(it does not constantly check for a new jog speed - it follows the speed that you told it to go when the MAJ command executed). The MCD (Motion Change Dynamics) works well to change the speed. Note, you would need to monitor your reference speed (pot?) and re-issue the MCD command everytime the reference speed changes.

2. Don't know what you're doing wrong with the MAG - just guessing - did you create a virtual axis? ie. it should be listed under your motion group as an axis.

Good luck

.ER is error
then look at motiontag.ERR for a number that will point you in a direction that is likely to assist

I tried using a MCD initally, you can see the speed changing on the screen but the motor does not react to the change. How do you link the two together? I am also using a Scale with Parameters (SCP) instruction to control my potentiometer.

Michael - This may be a dumb question, but I don't really understand Extended Error Codes. From where are you supposed to retrieve that value?

Mallorz: please doanload Publication MOTION-RM002A-EN-P, from ab.com go to Appendix A you will find error explanation over there.

I got it to work with using an MCD.

I put the MCD in front of the MAJ and then made a branch that skips over the original input instructions with the Axis1_MCD.DN bit to transition the state of the rung again to send a signal that checks for a change in status.

It's a bit sketchy because it is constatnly transitioning and probably not an ideal method but it works. Satisfies me enough!

MAJ

I use something similar to the following rung for continuously changing speed reference

NEQ --------------|/|-----|------ MAJ

Speedref         MAJ.EN   |       Speed Ref

LastMAJRef                |

                          |--MOV

                             SpeedRef

                             LastMAJRef 

When the reference changes perform a MAJ providing that last scan you did not perform the MAJ

Why not gear positions?

Integrate the speed reference. Wrap the reference position where necessary.