AX2550 - resets under load

11 years 3 months ago #29525028 by Steve
AX2550 - resets under load was created by Steve
We are currently testing our second AX2550 (first is back for repair at the moment).

The application is a remote controlled outdoor vehicle.
A micro-controller on the vehicle generates RC signals to control the AX2550 in mixed speed format.

Under load, the AX2550 appears to reset itself (motors freewheel, LCD shows solid 8, then starts the \"no ctrl\" message, then comes online again).

The controller logic (yellow/black wires) is powered from a separate 12V battery - motors are connected to a 24V pack - so I don\'t think it is undervoltage resetting the drive.

I\'ve got the current limit set to 60A, but have previously tried it on 105A and 120A.

I\'m reading the RS232 diagnostics back into Roborun via a pair of Bluetooth modules.

FET temperatures appear OK (both around 40 deg C).
Internal 12V appears steady
Battery voltage appears steady.

Even on the 60A limit, I am seeing battery current spike to 80-100A under load.

Motor current is very erratic, but appears to approach the 120A capacity of the drive just before each reset.

Is there any way to find out why the drive is resetting?

Regards

Steve

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11 years 3 months ago #29525029 by cosma
Replied by cosma on topic Re:AX2550 - resets under load
The amps limiting correction is very quick and will from time to time cause serious oscillation depending on the load characteristics.

When this occurs, large current swings, and therefore electical noise is generated.

We have just released a new version of the firmware with an Amps limiting algorithm that much more smoothly. Please download and try dev.roboteq.com/dev1/files_n_images/file...roboup19f-052509.zip

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11 years 3 months ago #29525030 by Steve
Replied by Steve on topic Re:AX2550 - resets under load
We are already using the 19f firmware update.

The current does not appear to be hitting a limit - the drive just resets when under load.

The reset happens \"instantly\" (i.e. <1 sec) after applying the load.

Any ideas?

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11 years 3 months ago #29525031 by cosma
Replied by cosma on topic Re:AX2550 - resets under load
Is the current erratic at the limit with v1.9f?

At what load level does the controller reset?

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11 years 3 months ago #29525032 by Steve
Replied by Steve on topic Re:AX2550 - resets under load
The current doesn\'t appear to be erratic.

When the vehicle is moving, it appears to be under control and reasonably smooth.

On some slopes or climbing over rough ground, the drive just resets itself. Some times it handles the same slopes and rough ground fine.

I didn\'t notice any difference in behaviour from 1.9e (as shipped) to 1.9f firmware.

The reset happens most often when setting off from stationary, but can happen whilst moving.

Any ideas why the drive is resetting?

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11 years 3 months ago #29525034 by cosma
Replied by cosma on topic Re:AX2550 - resets under load
This normally never happens.

We have seen an occasional MCU reset under extreme noise condition, but these are very rare events. Your case appears to be systematic.

The only way this can happen is for the power supply to momentarily dip below 5V or so. Since you have a separate 12V supply on your controller, this should not be happening.

Another way to reset the mcu is by sending the sequence %rrrrr via the rs232 port. This is practically impossible to have this generated randomly, however.

Try getting more clues as to the precise conditions this is happening.

Try reinstalling the firmware in case the previous install was flawed.

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11 years 3 months ago #29525036 by Steve
Replied by Steve on topic Re:AX2550 - resets under load
cosma wrote:


Try getting more clues as to the precise conditions this is happening.


What other clues can I provide?
The drive resets when it should be current limiting - as the motor currents approach 120A, it resets.

I\'ll try reloading the firmware, but doubt this has anything to do with it. Both our drives (the one currently back for repair, plus this new one) have behaved the same, using firmware versions 1.9d, 1.9e and 1.9f

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11 years 3 months ago #29525037 by Steve
Replied by Steve on topic Re:AX2550 - resets under load
How is the current limit meant to work?

I understand from the manual that the user specified current limit refers to the battery current.

If the motor current hits 120A, should it limit to 120A? For how many seconds should the drive be able to apply the full 120A before overheating or shutting down?

Regards

Steve

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