Machinekit + Ros for Scorbot Er-3

[Tom M]

Hi Guys,

Members of our hackerspace Workshop 88 have acquired 3 Scorbot Er-3 with controllers.    We've tested them out and the bot's who we've named Huey, Dewey and Louie all seem to be working well.

We'd like to use Ros on those bots, but the issue is how to get there.

I was reading Alex Rössler post about machinekit and Ros at https://machinekoder.com/machinekit-ros-open-source-robots/ and it seems like this might be an approach worth trying.

Seb Kuzminsky used linuxcnc on a scorbot Er-3 with the existing control
https://github.com/LinuxCNC/linuxcnc/blob/master/src/hal/user_comps/scorbot-er-3.py

https://github.com/LinuxCNC/linuxcnc/tree/master/configs/by_machine/scorbot-er-3 I've been corresponding with him on this and he said that this approach resulted in jerky motion since linuxcnc was communicating of a 9600 baud serial line. He wound up replacing the control and creating a new controller with  Mesa 7i43 (EPP Hostmot2 card), a Mesa 7i54 (Six channel 3A 40V Servo interface), We've been toying with a couple approaches: One approach would be to replace the controller and build a servo interphase using arduino nano's and a L298 motor drivers: https://www.youtube.com/watch?v=vHufLMh4xEI and either use a pc or bbb to handle the motion planning. We've been studying the Scorbot controller and it is well made and fully socketed.   We were thinking that we could lobotimizing  the control by yanking the 8031 control.   15 pins basically access everything on the board.  It would be sort of cool, if we could create a cape and socket adapter and just plug in a bbb to the control and get it to run.  We're still in the process of figuring out the motor drivers and the encoders.   Have people done this sort of thing is a dumb idea?  Is machinekit via a BBB able to handle this type of multiplexing out of the box or with minor modification or would this be a major modification and a cludge not worth doing?  If there is a project that's done this already, could someone point me to a project that I could template from? Any thoughts on this would be appreciated, Thanks, Tom

[Charles Steinkuehler]

Well, I'd say if the controller is running an 8031, it's already been
lobotomized! :)

More seriously, unless there's a serious desire to work with the low
efficiency bipolar drive transistors and spend a bunch of time reverse
engineering the internal hardware, you'll be much better off just
scrapping the controller and hooking the 50-pin robot cable to something
much newer.

The Mesa 7i54 would be pretty much ideal and could connect directly to
the robot. Lots of other options are available depending on what you
want to use for motor drivers and where you want to close the servo loop.

On 5/3/2020 1:18 PM, Tom M wrote:
> Hi Guys,
>

> Members of our hackerspace Workshop 88 <http://www.workshop88.com/> have

--
Charles Steinkuehler
cha...@steinkuehler.net

[John Morris]

Hi Tom,

You've had some good advice on the low-level HAL integration already.

Once you have all your joints and I/O connected up to HAL and you're
ready to connect the robot up to MoveIt! and the rest of ROS, check out
the hal_ros_control software [1] that @luminize, @machinekoder and I
have written. It will hook into your `moveit_setup_assistant`
configuration with little fuss, and you'll be moving your robot through
RViz in no time.

Good luck!

[1]: https://github.com/zultron/hal_ros_control/

John

On 5/4/20 2:18 AM, Tom M wrote:
> Hi Guys,
>

> Members of our hackerspace Workshop 88 <http://www.workshop88.com/> have

> acquired 3 Scorbot Er-3 with controllers.    We've tested them out and
> the bot's who we've named Huey, Dewey and Louie all seem to be working well.
>
> We'd like to use Ros on those bots, but the issue is how to get there.
>
> I was reading Alex Rössler post about machinekit and Ros at
> https://machinekoder.com/machinekit-ros-open-source-robots/ and it seems
> like this might be an approach worth trying.
>
> Seb Kuzminsky used linuxcnc on a scorbot Er-3 with the existing control
> https://github.com/LinuxCNC/linuxcnc/blob/master/src/hal/user_comps/scorbot-er-3.py

> <https://github.com/LinuxCNC/linuxcnc/blob/master/src/hal/user_comps/scorbot-er-3.py>
>
> https://github.com/LinuxCNC/linuxcnc/tree/master/configs/by_machine/scorbot-er-3 <https://github.com/LinuxCNC/linuxcnc/tree/master/configs/by_machine/scorbot-er-3>

> --
> website: http://www.machinekit.io blog: http://blog.machinekit.io
> github: https://github.com/machinekit
> ---
> You received this message because you are subscribed to the Google
> Groups "Machinekit" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to machinekit+...@googlegroups.com
> <mailto:machinekit+...@googlegroups.com>.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/machinekit/2b219361-5664-4576-8e81-08c055309bb2%40googlegroups.com
> <https://groups.google.com/d/msgid/machinekit/2b219361-5664-4576-8e81-08c055309bb2%40googlegroups.com?utm_medium=email&utm_source=footer>.