Robotic kinematics

JoergS5

@Toaster0042 I will make a release soon.

JoergS5

@Toaster0042 You can help me by providing

some pictures of the robot arm. Special interest is how the parallelogram is built, i. e. is it a triangle or some other solution. How is the parallelogram connected to the endpoint?
exact measures of arm lengths
to which parts are the steppers connected

This allows me to build the same and verify the code before publishing.

Toaster0042

@JoergS5 I can get the measurements to you a bit later but this is the arm I am using https://www.instructables.com/Build-a-Giant-3D-Printed-Robot-Arm/

JoergS5

@Toaster0042 I don't need the measurements, because it's not a 4 axis parallel robot.

It's like an industrial 6 axis robot, but without the 6th axis. Instead the 6th axis, the 6th actuator is used to grip.

I have code for the 6 axis robot, but not for your 5 axis plus gripper. I have to think about it. Your project is interesting, I want to support your robot type if possible. I will ask you to test code with your robot to verify the code.

Toaster0042

@JoergS5 ah ok, I tought it would fall under the 4 axis robot with an aditional rotating joint, I am fine with testing it I simply need to finish printing it as I have not finished it yet and was trying to get the firmware set before but I will be happy to test the code

JoergS5

I have time in May and June now to proceed developing robot kinematics. The order is

4 axis parallel (the black robot arm), probably as a quick-and-dirty approach first for @YuriConfessor
DWC plugin to design and analyse a given model
CoreXY/Prusa/Cartesian 5 axis AC and BC
6 axis robot
testing whether Qt is a possibility for a designer/slicer
elaborate tool design. My personal priority is using robot for CNC, so I'll work on support for different tools (tool shape etc).

I'll use 3.5.1 as basis.

Mummed

@JoergS5 Dear Joerg, thank you for sharing all of your hard work. I have this post and RepRap configuration regarding robot 3D printing. Since I am new to this topic, I may as you s question about configuring. Can we use the same procedure if we have a 6DOF robotic arm with its own controller and need to add an extruder to it?
from my understanding, most of the discussions in the forum and documentation focused on developing a robotic arm and its configuration however I couldn't figure it out how to synchronize robot motion and extruder commands for printing.

Thank you,
Mohamad

o_lampe

@Mummed You can define fans, heater and a tool same as any other 3D printer. But to make it work with a 6DOF arm, you'd need a matching slicer.

Toaster0042

@JoergS5 Hey! I just wanted to check back on this and see if you had made progress on this and if you had made the implementation of the new kinematics

JoergS5

@Toaster0042 you're right, I should inform, I will prepare an update.

JoergS5

I'm back with robotics. My partner passed away, I had to mourn, I have a new partner now since a few months, she will be on vacancy alone mid to end may. So this will be the time frame when I will work on robot kinematics again, based on RRF 3.6.

I will implement an idea I had last year and started implementing some time ago. Robotics solutions are be very different for forward and inverse kinematics. So I thought about a generic approach:

a forward chain to combine different drive movements into one movement chain, with one or multiple solutions
a backward (inverse) chain with the result of none to multiple solutions
forward and backward chains are stored in arrays which can be set by parameters with M669. Kinematic code will simply process the chains
to find the chain solutions, the user can think it through mathematically and set the parameters or he can use the to-be-programmed Qt based program to set solutions or simulate them and compare to measurements of the prototype
the chain elements are code fragements to implement mathematical solutions. The mathematicsal solutions can be augmented in future releases when necessary

That's my plan.

droftarts

@JoergS5 I'm sorry for your loss. I'm glad that you have been able to move forward and find a new relationship, and I look forward to more robotics development. I really must rebuild my robot arm...

Ian

jay_s_uk

@droftarts Looking forward to seeing pictures of you with your robot arm fitted...

o_lampe

@jay_s_uk Hmmm,
like Winter soldier?

T3P3Tony

@JoergS5 very sorry for your loss.

Thanks for the update on what you are planning.

droftarts

@o_lampe said in Robotic kinematics:

@jay_s_uk Hmmm,

My Bucky cosplay is at 1%.

Ian

droftarts

@JoergS5 Might this be useful in developing the reverse kinematics? https://hackaday.com/2025/06/03/simulation-and-motion-planning-for-6dof-robotic-arm/ which leads to https://hackaday.io/project/197770-manipylator/log/240946-manipylator-part-2-simulation-motion-planning
Though I think you may have progressed beyond this level already? Perhaps good as a starter for others getting involved.

Ian

JoergS5

@droftarts thank you Ian for the link. This approach is through Jacobian calculations. I started with this approach, but it takes too long time to calculate in Duet, because it needs iterations. Iterations are really bad for the resticted calculation resources of Duet and the approach described has a serious limitation of multiple singularity situations. Worse, sometimes I had no solution for the iterations. I changed to direct mathematical calculations instead and found screw theory and geometric algebra better suited.

As you told, the article is of course very good, e. g. to motivate starting oneself with robotics.