Problem in dual speed/position mode

12 years 4 months ago #26121322 by blovegro
Problem in dual speed/position mode was created by blovegro
I have an AX3500 and two motors. If I select speed control for both motors, motor A works fine (closed loop, has a working encoder). If I set the mode to "A Speed, B position", motor A behaves very erratically and does random motions.

My students explored this last fall and were told it is a firmware problem. We are returning to this project now, and I need to know if there is any updated information. The firmware is 1.9d 10/23/07 and the encoder firmware is V1.7 02/01/05 which still appear to be the latest release.

Having motor A in speed control and motor B in position control is mandatory for our project, and if there is no solution we will have to switch controllers.

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12 years 4 months ago #26156749 by cosma
Replied by cosma on topic Re:Problem in dual speed/position mode
A speed and B position is a supported mode.

For motor A, are you running in open or closed loop mode? if closed loop, what kind of feedback?

For motor B in position mode, what feedback are you using?

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12 years 4 months ago #26195738 by blovegro
Replied by blovegro on topic Re:Problem in dual speed/position mode
A is closed loop with optical encoder feedback. It works great by itself if both channels are set in speed mode.

B is analog (potentiometer) feedback. It also works great by itself if both channels are set in position mode.

When we set A speed/B position, B still works correctly but A does random erratic motions.

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12 years 3 months ago #26326945 by blovegro
Replied by blovegro on topic Re:Problem in dual speed/position mode
More specifically, here is the bad behavior. Motor A oscillates, in larger and larger oscillations with each step, as if in position mode with a PID loop with way too much gain. Except A is supposed to be in speed mode.

Note that the manual says the same PID parameters are used for both channels, so this may be part of the problem if the two motors are in different modes.

Maybe doing both speed and position and both closed loop and one encoder and one analog input is more than the controller can handle?

Note that an answer is needed soon. Is it possible to talk to a live person about this?

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12 years 3 months ago #26327904 by cosma
Replied by cosma on topic Re:Problem in dual speed/position mode
The controller has no problem handling two separate closed loops but it is correct that the PID settings will be the same for both motors.

PID settings can be different for both channels but only in RS232 mode. In this case, the external computer needs to set both PID sets using commands at runtime. These settings are not saved in the controller after power is turned off.

You can verify if the problem is due to the different PIDs buy trying to find the good values exercising only motor 1 and values for motor 2

If you need help, email your phone number using our contact form at <A href=" dev.roboteq.com/dev1/contactus.html " target=_blank> www.roboteq.com/contactus.html

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