• Perry posted an update 6 years, 11 months ago

    Here is my version of the forearm. Basically trying the same as Marten. I wanted a straight run for the tendons so I would not need the tensioning spring system. Kept Gael’s servo holder and guide system. Also the wrist drive is in line and not offset which I think makes it a little more robust. Used a slimmed down version of Marten’s…[Read more]

    • Looks awesome Perry !
      It’s a nice option to use the default servo’s 🙂

      And are you happy with the mechanical results ?
      For you it’s better to see and feel the results instead of the default setup 🙂

      • Thanks Marten. I like it a lot. There is still a bit of tuning to do but the geometries are good and the wrist rotation is solid. I may still put an inline tension spring in place but not sure. Time will tell if it is needed.

    • Great Perry, I see that there is many inventors around!

  • Alan Timm posted an update 7 years ago

    • Proof-of-concept for adding force control/feedback to Servos using the InMoov Finger Starter.

      Modified the kit to accept an FSR. The servo is modified and mounted that it can slide a bit in the direction of force. As the finger tightens, it forces the servo case against the FSR, which is then read. Basic force control written in Arduino as proof…[Read more]

    • juerg replied 7 years ago

      simply fantastic! Looks very responsive. Will you share more details about it and the code to run it? As you say it’s controlled by the arduino some more cables to route to the hand or are you thinking about a separate nano controlling each hand?

    • Great project Alan!!
      As mentionned Joel had done a great research on the hall effect sensors. The FSR are not very responsive unless pressure is applied. How did you manage to fix the two kapton copper wiring? Won’t they brake/tear after long term running?

      • Hey Gael, Thanks!

        These FSRs are the exact same ones that many people are using for autolevelling 3d printers, I haven’t heard of them breaking under similar use. Here’s the exact ones that I’m using. https://www.sparkfun.com/products/9375

        Because of their placement next to the servo housing they end up being very sensitive relative to the…[Read more]

        • Thanks for the extra pictures, it gives a good idea about the process!
          What is nice with this setup, is that it avoids having cables running within the fingers. (Which is not easy to work with);
          The servo bed would need a bit of modfication, but all together, it’s not so much work and it could even be applied to forarms that have already been…[Read more]

          • juerg replied 7 years ago

            right, big thing, no need to take too much apart.
            My question however is unanswered – I assume the finger tester code reads back the status of the FSR and repositions the finger? This will need 5 more cables from the forearm to the arduino and a modified finger service to take this into account? Or am I (once more) wrong again? Tell me I am…[Read more]

            • The Nervo board can handle the sensors. In my tutorial I explain how to set an extra ribbon dedicated to the sensors. Inded the service will need to be adapted which I have been waiting for ever since I have added the sensors in the fingers. 🙂
              Time to take that in a serious matter!

            • juerg replied 7 years ago

              Right, your finger sensor has been in place for a long time but it just looked too fragile to me to build it into the hand. And as you say it never got respected in the servo service?

    • I hadn’t seen this, but there’s a guy out there by the name of Clement Vella who has also worked out a solution using FSRs, not sure if they’re hand made or not, but he a sensor for each direction of force and integrated it into the pulley.

      His video also confirms one of my questions, that maybe applying PID to the control code may work better…[Read more]