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Thread: Horus Mk. I Biped Robot

  1. Horus Mk. I Biped Robot

    Let me introduce Horus Mk. I, my Biped Robot

    It has been walking for few months and I still work on balance and speed improvements. It can walk forward, rearward and steer.

    Horus is equipped with 12 homemade articulation joints, driven with dsPIC. I use positions sensors (encoders and potentiometers) and force sensors (which contribute to balancing control).


    The Global Control is made with a mini PC communicating with joints with I2c Ports.


    I just opened a blog to describe how I build test this robot : http://www.avbotics.com





  2. #2

    Re: Horus Mk. I Biped Robot

    Very nice! You've got to give us more details! :-D

    Are you using springs to help the actuators hold default pose as well?
    How much current do those linear actuators draw? Are they voice coil-like? They seem to have none of the DC motor whir.

  3. Re: Horus Mk. I Biped Robot

    I use no springs to help the actuators. Actuators can produce enough torque (~10 N.m). I had to increase the DC motor size of the x2 hip axis (change motor size from RE 385 to RE 540).

    I do not have very precise measurement of linear actuators drawn current but it is around 1 A. The x2 Hip joints that hold the cantilevered lifted leg drag a little bit more current.

    Linear actuator are driven by standard DC motor with a 1:5 reducer and a screw. You can have more d├ętails about their design in my Blog : https://avbotics.com/linear-actuators/

    I avoided DC motor whir by applying 20 khz PWM on the motor H-Bridges inputs.

  4. #4

    Re: Horus Mk. I Biped Robot

    "A slot is machined all along the piston and a 3 mm headless screw with a 2 mm nipple, crossing both the aluminium tube and an end plastic bearing, prevents the piston from rotating."

    Interesting. An M3 grub screw is not very strong, especially when there is no axial thrust to force it against the threads (this is the main holding force for bolts as far as I know.)

    Have you seen any problems with the grub screws being effectively driven by the keyway in the piston, and unscrewing themselves?

  5. Re: Horus Mk. I Biped Robot

    You're right, that is the reason why I also use a lock nut, later I added thread lock, as unscrewing happened sometimes. I thought of press-fitting an aluminium collar on the Outside Diameter of the tube end, to increase thread length, but I still have to do it

  6. #6

    Re: Horus Mk. I Biped Robot

    I think a screw isn't the right choice for a key for a keyway. A pin, perhaps? You could secure it with a screw sideways, and you wouldn't have the same rotating/driving force on it.
    Or do it right and put a keyway in the cylinder, too, and insert a rectangular key to lock them together.
    Last edited by jwatte; 2 Weeks Ago at 04:00 PM.

  7. Re: Horus Mk. I Biped Robot

    Hello, I posted a new section in my blog dedicated to control of the joints position (https://www.avbotics.com/joints-control-system/). This includes explanations about how to use load cell in order to emulate a sprung / damped output. This can be useful for those interested in haptic interfaces.

    See how it works in the video below:

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