Proposition of new workbench: Kinematic Scheme

[Mika38]

Hello,

I always found the concept of creating the parts, then create an assembly, not really the right way to do create a cad model. Especially when you don't know how the parts look like. There is case where, you are more interested by the way the parts move one from each other. So, I proposed you to create the joints first then to connect them. In other words, creating the kinematic scheme before the parts.

- What? A proposition of new feature in FreeCAD: kinematic scheme workbench, can be also kinematic diagram
- For Who? The designer of mechanism, mechanical student, hackers
- Why? Help the creation of mechanism
- What is the main concept behind the feature? New way to look at an assembly, focus on the joints and not in the parts. The joints are created first the part follow.

- Should it be 2D or 3D? Even if most of the mechanisms can be represented in a plane, I think making it in 3D will be more simple to code. Also FreeCAD is a 3D software, why developing a 2D workbench when a 3D one is useful? Also animation will be in 3D and not 2d.
- Isn’t it the robot workbench? Yes and no. Yes because the kinematic scheme workbench can represent a robot. No because you can not create a loop of joint with the robot workbench.
- Workbench or macro? Macro for start, workbench in the future.
- Does it already exist in FreeCAD? No, there is no answer for “kinematic scheme” with the FreeCAD forum search engine.

- How would it work?
-- The user places different joints.
-- He connect them together.
-- He can constraint the position of the joint one from each other.
-- He animate the mechanism by locking connectors(s) and forcing the movement of joint(s).
-- He can modify the relative position of the joints, and the type of joints
-- He can send the cinematic scheme to the assembly workbench. In the assembly workbench, the parts are generated, the constrains between the part are also automatically created.

- What additional feature would be appreciated?
-- Having a library of mechanism
-- Display the number of degree of freedom, like in sketcher.
-- Display which loop of the mechanism is over-constrain and in which direction.
-- Same if it not enough constrain.
-- Trace the position of one element during a animation.
-- Measure the kinematic characteristic of a part.
-- Possibility to measure the value of each dof(Degree Of Freedom) of each joint.
-- Possibility to change position of the joint the mechanism then save as a new file.
-- Automatically generate the constrain between each joint.
-- Mechanical solver to deduce the force, torque, speed and acceleration.
-- Generate automatically the kinematic scheme from an assembly

Challenges :
- Representation of joint in 3d. Should it follow the Norm? Used a better design? Closer to reality? Have a 3d printable design? The easiest way to code?
- How the connectors are created. The shortest road? automatic? Manual? From the axis of the joint? Using a 3D grid?
- How does the part with three joints look like? Three connectors? Only Two? From which joint the the constrain should be created?
- Same question with more joints inside of one part?
- When the user drag a joint, does the dofs (Degrees Of Freedom) of the joints change or the relative position between joints change?
- represent a complete joint

So, what do you think?
Could it be interesting to make a kinematic scheme workbench?

Mika

Illustration: 2d kinematic diagrams

[Kunda1]

Checkout the FEM subforum. I saw a recent animated gif that looks similar to what you are looking for...

[Kunda1]

Here is the specific thread: https://forum.freecadweb.org/viewtopic. ... ed#p158672

[PrzemoF]

Interesting idea! What is in the fem thread is way more complicated as it's a real life simulation. Making joints with defined DOF should be much easier. I'd start with checking what animation workbench can do.

[microelly2]

I'd start with checking what animation workbench can do.

Animation wb can only animate, no simulation and no constraints solver

[r-frank]

Hello.

For 2D you could take a look at Linkage.

For 3D you could have a look at Solvespace Linkages.

Perhaps some of the ideas presented there could serve as Input here ?

BTW: great idea, i would LOVE to have such a workbench, i wish my programming skills were better so that i could contribute ...

Roland

[microelly2]

For 3D you could have a look at Solvespace Linkages.

Solvespace is GPL3 and opensource, so the easiest way is to write an interface to delegate the jobs from freecad to solvespace.

[efyx]

Are you able to perform such WB? I am waiting for this almost as for full functional TechDraw

[triplus]

This could end up being different effort but likely Assembly/Kinematic will end up sharing common things. And if a good coder with sensible ideas takes the job likely up to 2 years of work needed. For first production ready results to emerge.

[ulrich1a]

Does it already exist in FreeCAD? No, there is no answer for “kinematic scheme” with the FreeCAD forum search engine.

Yes a kinematic scheme may not exist. But there is the sketcher. And the sketcher can do all the linkages shown on the sample image. They can be animated by dragging with the mouse or with a simple script.
Even the model shown in this thread, was made first as a sketch: https://forum.freecadweb.org/viewtopic. ... ed#p158672

The linkage is then essentially in a plane, but the plane can be put everywhere in 3D-space. So for a start, most of the needed items are there. Just a kinematic chain working out of plane need something different.

Ulrich