Special foot with a double rotation

This is a new foot of poppy. This foot allowed dual rotation and improves stability. I just add a double rotation with MX28 and I modified a leg.

Here are several views with Solidworks:

Right view:

Front view:

View with rotation:

<img src="/uploads/poppy/27/5d14acb45db8b03d.PNG" width="348"height=“500”>

What do you think of the new foot?

Sound great idea to have a double rotation, that is more “Human like”

Maybe the ankle on the back (like human) could give better results.

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And maybe a spring to simulate the Achilles tendons like the two springs in the knee.

Really good design @Alexandre, I only have 2 comments.

  1. I’m agree with @aurelien, I would like to see the double-rotation placed in the other direction, with the sagittal DoF at the back and the lateral DoF on the front.
  2. I think the material placed here:

    Both limit the rotation amplitude and are not useful for the robustness of the part.
  3. Bonus :slight_smile: , you could reduce the gap between the foot and the motor:

    There is enough room for the motor to move and so you could reduce the torque applied by the feet on the motor by reducing the lever arm.

Taking in account these comments should produce a foot looking like this:

Also after these comments, you could add an extra feature :slight_smile:

This foot design is made to explore the balance of the humanoid robot. You just added a DoF and we (@Steve) will now be able to study how important this rotation is and what range of motion and torque are needed. Another interesting point is the position of the ankle, in particular along the length of the foot:

This could be easily done by allowing the double_rotation to be attached to the foot on several location (3 - 4 or +).

I make the modification

@Matthieu I can’t reduce the gap between the foot and the motor. I just 2mm margin. Looking the picture

If you really need more gap, maybe you can cut the U part in 2 part to let more space.
But if Humanely, you can’t make a 90° angle with your fit too … maybe 70° max too. So it’s pretty human and sounds good :slight_smile:

Yes, it’s true, so I make a modification. Now, the lateral Dof allows 25° max rotation, it’s more human.


I moved a post to an existing topic: New foot design

To integrate force sensors under such foot, maybe we should simply use the work done on DarwinOP ? In particular, they have an already designed and functional electronic board …


It seems to be a good device, but 400€… Each resistive sensor is 7.5€. 80€ of sensors ok but 300€ of electronic measuring resistance, I dont understand.

I guess it is the aluminium parts that are costly… As we are already using a lot of Robotis motors, maybe can we buy only the electronic

Yes, a good point I just saw is that it is seen as a Dynamixel servo motor according to connectics.