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ros-industrial / staubli_val3_driver

ROS-Industrial (simple message) driver for Stäubli CS8 and CS9 robot controllers (VAL 3 application)
Apache License 2.0
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On-line joint motion control using VAL 3 driver #20

Closed sonny-tarbouriech closed 4 years ago

sonny-tarbouriech commented 4 years ago

Hi there,

I'm trying to find a solution to perform a reactive control on a Staubli tx2 robot using ROS. From what I understand, the driver provides a FollowJointTrajectory action server which intends to execute a pre-calculated joint trajectory on the robot.

Would there be a way to use/implement a "low" level controller allowing to execute dynamic motions instead of pre-defined trajectories?

Thank you in advance for your help.

Sonny

gavanderhoorn commented 4 years ago

From what I understand, the driver provides a FollowJointTrajectory action server which intends to execute a pre-calculated joint trajectory on the robot.

Yes, that is correct.

Would there be a way to use/implement a "low" level controller allowing to execute dynamic motions instead of pre-defined trajectories?

Well, not without changes to the source.

The modifications needed would be similar to ros-industrial/motoman#215, which essentially adds a topic interface which accepts individual points.

No one has released this for the generic clients though, which this driver uses.

The controller itself would certainly support it -- as long as the motion queue is kept non-empty, motions should remain continuous. What you could expect in terms of latency I couldn't predict.

SinaMirrazavi commented 4 years ago

Hi,

In case one do the modifications, I was wondering what would be the maximum update rate for on-line planning? Is it 250 Hz?

Best, Sina

gavanderhoorn commented 4 years ago

I can't say anything conclusively.

Perhaps @marshallpowell97 could comment on that.

gavanderhoorn commented 4 years ago

Also: closing this due to inactivity.

SinaMirrazavi commented 4 years ago

Thanks a lot. @marshallpowell97 , I just need an approximate number, no need for the accurate one.

marshallpowell97 commented 4 years ago

@sinamr The arm uses a boxcar filter which changes the update frequency of the arm. The filter length is not necessarily the same on each arm, so the update frequency will not always be the same. There are ways to bypass the boxcar filter (I.E. using a pre-calculated spline trajectory) but all require an additional license from Staubli.

I looked into adding something like this to the driver, but it did not make sense to add something here that would only be usable with an additional (paid) license.