Loki Arm Mechanical

13 Responses to Loki Arm Mechanical

  1. Robert says:

    Dave,

    Just wondering how you routed the wiring through Loki’s arm? Especially around the wrist joint that rotates. It is not very clear in the pics and I will be facing this problem shortly with my Herbert.

    Bob

  2. Mohamed says:

    Hi Dave I was wondering if you could send me instructions on how to build the arm .please email me at Mohamedrahimtola@gmail.com by the way your work is an inspiration to all wish some day I can send pics of my robot to you.thanks

  3. Chris says:

    Hi Dave, another question… Do you have drawings for the way you built Loki’s arms? Preferably the newer version with the single dynamixel elbow joint? Thanks

    Chris

  4. Bob says:

    Hi Dave,

    I am rebuilding Herbert’s arm, using a hollow tube for the shoulder joint as well as using a “box” construction to mount the sprockets and motor etc. Hopefully this will be more sturdy and flex less.
    My question is more of sensing. When you instruct Loki to “take this” how did Loki find the object and then how did he move his arm components to that location? I don’t have Kinect either so it would have to be accomplished with video or other sensors.

    • dshinsel says:

      Hi Bob,
      “take this” is easy; (picking up an object from the ground is much harder). He just moves his arm to a pre-programmed position, and waits to see an object placed in his hand. To sense the object, I have:
      1. a short range Sharp IR sensor mounted on the “wrist” servo. this is the most reliable.
      2. short range IR sensors in each fingertip; these sometimes work, sometimes not
      3. pressure sensors in the fingertips to tell if he “got something”
      4. check torque reported by the Dynamixel servo to see if he “got something”.

      hope this helps

      • Bob says:

        Dave,

        Thanks for writing back. I was hoping the “take this” command was a bit more that going to a predetermined position, but that is easy enough to institute.
        Which method for sensing the presence of an object did you find most relilable? I was thinking of mounting an ultrasonic sensor within the gripper to measure relative distance to the object and I was planning on pressure sensing strips mounted to the “claws” of the gripper for force.
        I am also working with vision software to hopefully identify objects (roborealm) and other navigation efforts. Have you had any experience with vision systems?

        Bob

        PS> I guess no more robot fighting. It’s funny but my daughter wants to make a battle bot and already has some designs in her head. She is not into robotics or electronics but for some reason feels inspired. I myself feel I put way too much work into a robot to go and have it destroyed in a war.

      • Bob says:

        Dave,

        I was hoping the “take this” command was a bit more that going to a predetermined position, but that is easy enough to institute.
        Which method for sensing the presence of an object did you find most relilable? I was thinking of mounting an ultrasonic sensor within the gripper to measure relative distance to the object and I was planning on pressure sensing strips mounted to the “claws” of the gripper for force.
        I am also working with vision software to hopefully identify objects (roborealm) and other navigation efforts. Have you had any experience with vision systems?

        Bob

        PS> I guess no more robot fighting. It’s funny but my daughter wants to make a battle bot and already has some designs in her head. She is not into robotics or electronics but for some reason feels inspired. I myself feel I put way too much work into a robot to go and have it destroyed in a war.

        • dshinsel says:

          Regarding robot fighting, I heard they are lining up another season of battlebots 🙂 I agree, hard to build a robot and watch it get destroyed!

          for the servos, you just need to walk through the startup code; look at RobotCmdView.cpp.
          Blue means that “SUBSYSTEM_DISABLED == g_DynaSubSystemStatus” (search for this). I think this may be getting set in SetupView.cpp, so search there for “g_DynaSubSystemStatus”. Hope this helps!

          if( g_DynaSubSystemStatus != LastConnectedToDyna )
          {
          if( SUBSYSTEM_CONNECTED == g_DynaSubSystemStatus )
          strText.Format( _T(“Ready”) );
          else if( SUBSYSTEM_DISABLED == g_DynaSubSystemStatus )
          strText.Format( _T(“Disabled”) );
          else if( SUBSYSTEM_WAITING == g_DynaSubSystemStatus )
          strText.Format( _T(“Initializing”) );
          else
          strText.Format( _T(“ERROR”) );
          SetDlgItemText( IDC_DYNA_STATUS, (LPCTSTR)strText );
          LastConnectedToDyna = g_DynaSubSystemStatus;
          }

  5. Danny says:

    Hi Dave,

    I am getting on the dynamixel and kerr flashing red error then it turns green. what will cause this?

    thank you
    Danny

  6. Chris says:

    Dave,

    On your elbow rotation joint dynamixel there appears to be a metal bushing attached to the servo horn itself. Was this a custom made adapter? And also the bearing at the elbow itself.. Where is that from? Thanks. Chris

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