Position Control

13 years 10 months ago #12617137 by clehmann
Position Control was created by clehmann

We are using a AX2550 with the encoder add-on module and I am trying to setup position control on a DC motor out of channel 2. My understanding from the manual is that (in testing anyway) I can move the slider to a set value and the motor will move until the encoder has passed the number * the distance divider as entered. Right now the motor will move one way or the other, but it just moves infinitely (as best I can tell). Other notes: The speed and RPM's seem to be reading right and the encoder counts is also moving correctly, but the Dist. field remains at zero no matter what. Is there somewhere I need to enable this field? Is it possible that I have something wrong enough that it's not even getting to count 1? Also, I have the channels set up as A speed, B position, closed loop (encoder selected for channel B). Help is appreciated. Thanks!

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13 years 10 months ago #12617294 by cosma
Replied by cosma on topic Re:Position Control
<P style="MARGIN: 0px">Verify and report the software revision of the encoder.
<P style="MARGIN: 0px">
<P style="MARGIN: 0px">Position feedback works in v1.7 of the Encoder firmware. If you have v1.0. You will need to update.
<P style="MARGIN: 0px">
<P style="MARGIN: 0px">If you already have v1.7 on the encoder, do not attempt to update the firmware.

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13 years 10 months ago #12617721 by clehmann
Replied by clehmann on topic Re:Position Control
I have encoder firmware version 1.0 4/17/04 currently. Which file should I use from the website to upgrade the firmware? Thanks!

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13 years 10 months ago #12618126 by cosma
Replied by cosma on topic Re:Position Control

The encoder firmware is at <A href=" dev.roboteq.com/dev1/files/software/roboenc17-020105.zip " target=_blank> dev.roboteq.com/dev1/files/software/roboenc17-020105.zip
<P style="MARGIN: 0px">You can use to upgrade from your current version.
<P style="MARGIN: 0px">
<P style="MARGIN: 0px">It should never be used to reload over an already installed v1.7 of the encoder firmware.

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13 years 10 months ago #12632135 by clehmann
Replied by clehmann on topic Re:Position Control

I have upgraded the firmware successfully to version 1.7 and now the Dist field is showing data. Now I am trying to get the slider position to correspond to a fixed position of rotation for my application. Is this possible? For counter values under 127 the Dist field will show the same as the counter value - OR the value (counter/dist. divider) - correctly, but once the motor turns past 127 or -127, it just keeps going and the motor won't stop. I feel like I'm missing something fundamental here, but I've gone through the editable options on the RoboRun utility and it seems that I'm on the right track. Help! Thanks!


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13 years 10 months ago #12633561 by cosma
Replied by cosma on topic Re:Position Control

If you have verified that you are in position mode, then not stopping at 0 is typically an indication that you are moving in the wrong direction. Try swapping the motor cables or swapping ChA and ChB of the encoders.

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13 years 10 months ago #12634716 by clehmann
Replied by clehmann on topic Re:Position Control

The rotation was correct, but I was using a closed loop setting and once I removed that and had everything correct, the motor started to behave as expected. When I move the slider, the motor turns until the (counter/dist. divider) is equal to the Dist field and the motor stops. We're making progress... My next issue is that I need the motor to make more revolutions for my application. Essentially I need a distance divider greater than 128. Is there a way to enter a greater value through RS232 commands? Another option I'm considering is just getting an encoder with fewer CPR so that when I hit the 16,000 counts (+127 x 128) the shaft will have turned futher. It seems like there would be a provision for this. Possibly only through RS232 commands?? Please let me know. Thanks for all the help...

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13 years 10 months ago #12635970 by cosma
Replied by cosma on topic Re:Position Control

Another way to extend the range is to play with the destination register.
<P style="MARGIN: 0px">You would leave the command to 0 and then load a value in the destination register. The distance is now = destination - 0 (command) / divider. Using this technique, you could position anywhere across the 2 billion points with a one count accuracy, theoretically.

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