Lite 6 oscillation when stopped

1

With a load of just over 500g, the end of the arm goes into oscillation, rocking backwards and forwards after stopping.

Even moving the arm slowly, it seems to detect its moved too far after stopping, tries to move back to compensate, moves too far, moves back again, moves too far, moves back again, etc…
It ends up rocking backwards and forwards.

Is there a way to turn off this compensation or do we need to use something like set_impedance_mbk(), ft_sensor_cali_load() or ft_sensor_set_zero()?
We’re using the python SDK 1.13.30

Many thanks, Pete.

2

Hi Peter,
Could you share us a video of the Lite 6 robot oscillation by Youtube link or Google driver link?
ft_sensor_cali_load() or ft_sensor_set_zero() are used for an 6 axis force torque sensor, which does not support Lite 6 and has nothing to do with robot oscillation.
Thanks

3

Hi Daniel, thanks for coming back to me.
This is a link to the video on youtube: https://youtube.com/shorts/lWuyNbYv--Q
Pete.

4

Hi Peter,
Thanks for the video
It seems the payload is heavier than 500g in the video. Could you let us know the exact weight of the payload? If you could measure the mass of center of the payload and let us know would be better.

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And does the robot works well if you remove all the payload of the robot?

5

Hi Daniel, thanks for your reply.

Yes, total weight is just over 600g with the centre of gravity approx 120mm from the end of the arm.
However, we still get the same problem with a mass of only 500g and a centre of gravity about 80mm from the end of the arm.
With the payload removed the oscillation doesn’t happen.

Overheating problem

We’re seeing servo 2 rapidly rise to 63 degrees using the code:
t = arm.temperatures[0:6]
We’ll collect a full set of data with some times…

The arm.motion_enable(servo_id=4,enable=False) function you suggested seems to work allowing the servo to cool, but there’s a bit of “clunk” as the arm drops slightly (we’re now doing each one in turn with a pause).

Pete.

6

Hi Pete,
We suspect the oscillation might come from J4 or J6, especially with a payload whose center of mass is far from the end flange. A wider-angle video showing the full arm and mounting orientation would help us better assess the issue.

As for the temperature: 63°C is normal. This value reflects the motor core temperature. The limit is 80°C — if exceeded, the joint will disable itself to protect the system.