The HEBI Community Forum

Hi,

I have been using Igor, and without any apparent reason, its left hip actuator (X5-9) has changed the absolute zero position by about Pi/2. This is absurd for me, and because of this, even the demo example code cannot work. I have tried switching off and on, plugging out the battery etc but it didn't help.

Thank you for your support.

Sorry that you're having problems. There is a parameter in Scope that lets you adjust the internal reference point. Maybe someone set it by accident? You can get to it by enabling the "Params" mode on the Dashboard tab.



You can offset the internal reference point, or move the actuator to where you want the zero point to be and then set the position reference to zero.

I hope this helps!

Thanks, it fixed the issue

Interestingly, I've observed a similar behavior, only on one or two of the X5-9 modules.
I know no one changed it since I am the only one with access to it, and the change happened on a local network without internet access.
What I saw was that sometimes the zero reference point would vary by exactly pi/2 in between restarts of the module. Then when restarted, sometimes the reference point would return without my doing anything.
I figured something was working wrong, and since I had a spare on hand, I just put in the spare, tagged it and left it on my desk, and moved right along.
It's intermittent so its hard for me to pin down. I can't spend the time poking at it more right now, but now that I have seen someone else saw this too, I may look at it more in the future and try to gather more data on what's going on. I have other X5-9's which I have not seen this ever happen with. In case it ends up being related to the production batch, the serial on the one I saw this happen on is X-00055.

Update: another lab member was working with X-80656 (an X8-9 on a hexapod) and also observed that the position reference point jumped by exactly 90 degrees.
We are not sure yet what causes this but he did not change it deliberately.

Problems where the actuator output position jumps by 90º is a problem where there is mechanical backlash on the magnetic encoders that provide the multi-turn absolute sensing on the output.

If you can send us the actuator we can repair it. We can coordinate via support@hebirobotics.com.

Thanks,
-Dave

We are also using IGOR robot. One hip actuator (X5-9) also jumped by 90 degrees. Even though we offset the actuator as taught by Hebi Robotics Tech Support. It did work sometimes, but we needed to re-offset again and again.

Wei (and others),

We recently released a firmware update that should help the 90-deg jumping issue. If the problem still persists, let us know at support@hebirobotics.com and we can work to get you a replacement actuator.

Thanks,
-Dave