I’m working on an animation of a robotic arm in Bongo and need help with properly configuring the joints and constraints. Here’s a brief description of the setup:

Setup Description:

Model: Robotic arm with 4 segments (AB, BC, CD, DE), all parallel to the Z-axis.

Pivots:

AB rotates around the pivot at A on the Z-axis.

BC, CD, DE rotate around their pivots at B, C, and D on the X-axis respectively.

Control Point: A point, “Pcurva”, moves along a circular path (“Curve”) located along the Y-axis, a defined distance from point A, which is the center of the coordinate system.

Objective: I would like the DE segment to remain parallel to the Z-axis throughout the animation as it follows the circular path defined by “Pcurva”. Currently, I am having trouble maintaining this configuration as the DE segment tends to tilt out of alignment with the Z-axis during movement.

Question: How can I configure the joints or apply a constraint in Bongo to ensure that the DE segment remains parallel to the Z-axis while following the movement of “Pcurva” along the curve?

Any advice on setting up this type of animation or similar examples would be greatly appreciated!

You can keep the DE section upwards by making it child of the Simple Constrained point PCurva. Hence the DE section nicely rotates along. At its top it takes a point object with it in the merry go round.

To that point the rest of the robot arm can be constrained. Make Layer 01 visible in the attached model to get the idea. Libero.3dm (108.9 KB)

You have been very helpful, thank you so much for your suggestion.

Thanks to you, I was able to solve this problem that had been stalling me for three days.

However, I am trying to make the segment from Epoint to Dpoint, which is normal to the blue curve on the hemisphere, move along this curve while always remaining normal to it and connected to the entire DC-CB-DA arm, with point D overlapping in the animation constraints at Dpoint.

Could you provide some guidance on how to correctly configure the movement so that the segment follows the curve while maintaining the desired orientation and interacts correctly with the rest of the robotic arm?

Fortunately the curve lies on a hemisphere. Hence a normal will point to its center.
This makes that the Simple Constraint “Look At” comes in handy here. EPoint is not only Simple Constrained to the patch but also ‘Looks at’ the point in the center.

The rod makes some uncontrollable twists though. If you want to avoid them I think there is an alternative way to build your robot arm – but then you have to show me the design of the various hinges.

Thank you very much for your support; your assistance has been invaluable and has helped me solve numerous issues. Now, I would like to discuss a more general case with you: I would like the segment to follow the curve while remaining normal to a generic surface, in this specific case, an arbitrary surface and curve.

Could you provide further assistance to tackle this new challenge?

Since Bongo offers hardly any tools for perpendicularity, nor does Rhino offer surface normal instruments supported by History, some creative thinking was necessary.
I found a approximate approach in equipping the DE-rod with a triangular base, consisting of 3 point that are constrained to the surface (all 3).

Then, I turned the structure of the robot arm upside-down so that IK solving is done in one go. Sometimes Bongo gives a problem when one IK chain depends on another one - as I understand the order of solving various chains is kind of random – it will probably be corrected in 3.0.

Libero33 001.3dm (310.7 KB)
Of course this solution isn’t arithmetical 100% correct, but hopefully it can do for a animation.

I wonder if you have any more difficult challenges?
And is there ultimately a million euros to be won at the highest level?