wmr
Registered: 12/03/08
Posts: 5
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Reply with quote | #1 |
Hello,
I am using an AX3500 in closed loop speed control mode to drive two motors independently.
At maximum load (stall conditions) the battery voltage drops to around 14 V (with up to 40 A current total, below the set current limit). The controller stops working (motor power cuts suddenly) suggesting the supply voltage is below the minimum which is fine, new batteries are being investigated. However, the battery voltage immediately rises to zero load level (24 V) but the controller does not re-start. The 7-segment display is switching rapidly between all-on (with dp) and as shown below (red is on).
Powering the controller off and back on corrects the problem. I cannot find this error message in the manual. Using the Roborun software, the controller is returning the low battery voltage reading even after the voltage has returned to the high level.
Is this error message the result of going under-voltage? Should the controller not restart when the voltage returns? I have tried connecting a steady supply (24 V) to the power control connection but still have this problem. Please can anyone with experience of this problem give some advice.
Thanks
EDIT: I was looking in the wrong manual and spotted what the display means now. Any help in overriding the encoder error protection would be appreciated
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cosma
Moderator
Registered: 04/10/04
Posts: 533
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Reply with quote | #2 |
This looks like another one of the safety features kicked in: encoder error, stall protection or short circuit protection. Try disabling them with roborun and test again.
Undervoltage activates below 10.5V and the controller immediately recovers when voltage rises again
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wmr
Registered: 12/03/08
Posts: 5
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Reply with quote | #3 |
It seems to be encoder error - switching off stall protection doesn't seem to help matters; and we can replicate the problem without a stall by disconnecting the encoders.
However, I can't find a GUI option to disable encoder error protection in the RoboRun software.
I've tried writing to address 04, i.e. reading the parameter with ^04 and writing it with ^04 00 then resetting the board but that doesn't seem to help.
I'm using firmware versions "RoboteQ v1.9d 10/23/07" and "RoboEnc v1.7 02/01/05" and the v.1.9d 02/15/08 version of RoboRun.
Thanks.
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cosma
Moderator
Registered: 04/10/04
Posts: 533
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Reply with quote | #4 |
The encoder safety check cannot be disabled, actually.
The way the check works is that the controller expects to see pulses generated by the encoder while the power level output to the motors is 50% or higher. If no pulse is seen after 0.5s at that power level, the protection kicks in.
In normal conditions, no motor movement at 50% power output would be a genuine fault. With batteries weak, this can happen, and probably does in your case.
We will soon release a software update and we'll incorporate that fix.
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wmr
Registered: 12/03/08
Posts: 5
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Reply with quote | #5 |
Quote: Originally Posted by cosma
In normal conditions, no motor movement at 50% power output would be a genuine fault. With batteries weak, this can happen, and probably does in your case.
Essentially our worry is we'll be ascending some steep terrain, we'll encounter a blockage that stalls the motors, the control board will cut out, and we'll roll backwards before we can restart the board. Obviously this is a problem when the batteries are weak, but it could be a problem when the batteries are fully charged too.
On the other hand I can see how the encoder protection could be useful for your other users. Perhaps there could be a configuration option to turn the encoder protection off? Or the encoder protection could set the PID target speed to zero for a few seconds instead of resetting the board?
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cosma
Moderator
Registered: 04/10/04
Posts: 533
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Reply with quote | #6 |
We are updating the firmware to allow this feature to be disabled. We'll also change the behavior so that after it triggers, returning command to stop will reset the fault. |
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wmr
Registered: 12/03/08
Posts: 5
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Reply with quote | #7 |
Thanks, just updated the firmware on our controller and it seems pretty useful.
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