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Thread: Handmade 5DOF Manipulator with tactile feedback

  1. Talking Handmade 5DOF Manipulator with tactile feedback




    Materials List:


    Polystyrene sheets: 0.5mm, 1.5mm and 2mm thick (Evergreen Models).

    Polystyrene tubing: Various


    Brass sheet: 0.5mm thick


    Brass tubing: Various


    Servos & Motors
    :

    2 x HS-805BB (Shoulder yaw & pitch joints)


    1 x HS-485HB (Elbow joint)


    1 x HS-322HD (Wrist joint)


    DC motor with 300:1 gearbox (Gripper)


    Tactile Feedback: Quantum Tunnelling Composite (QTC)


    1 x custom-made Electrical Rotary Union (Elbow-to-Wrist joint)


    1 x SKF Thrust Bearing (AXK 2542) + 2 x SKF Thrust Washers (AS 2542)


    Various springs


    Polystyrene glue


    Epoxy glue


    Heat glue


    Multi-strand wire


    Heat-shrink



    Tools List

    Scalpel

    Studding knife


    Small saw


    Small files – various cross-sections


    Sanding paper


    Dremmel


    Hand-drill


    Vice


    M3 & M4 taps


    Heat-gun


    ….generally speaking the more the better!



    This is a project I’ve been working on, for a solid month. It is a 5 DOF manipulator arm which has been designed and built entirely in my livingroom without any CAD / CAM. In other words all parts are designed and cut by hand. The material I used was styrene.

    A few words about Styrene

    The main construction material used is Polystyrene (or simply Styrene), which is widely available on most hobby stores. For bulk quantities or for those coming from the States, you can contact Evergreen Models – they will stock every styrene sheet / tubing you will ever need.


    Styrene is a soft, normally white plastic, which is very easy to handle and will bond very nicely when glued with polystyrene glue. I normally design the part I want to make directly onto the styrene sheet and cut it off using scissors. For internal cut-outs I use my Dremmel with a 2.5mm diameter Carbide cutter. If I need my part to be thicker than the sheet’s thickness, I make multiple identical parts and glue them together. When you make parts like that, make sure you leave the drilling for the end - this will ensure holes are aligned across all glued sheets.












    This manipulator arm has been built without CAD drawings; entirely with the method described above. It comprises 5 DOFs: a yaw and pitch root (shoulder joints), an elbow joint, a wrist joint and a gripper. The wrist joint is fitted with a custom-made electrical rotary union that will allow for continuous rotation of the end-effector (gripper) without electrical connectivity problems. Basically the electrical rotary union eliminates the need for cables between rotating mechanical assemblies.





    The gripper comprises two fingers each fitted with a Quantum Tunnelling Composite (QTC) pressure sensor. These sensors are basically pressure sensitive resistors that under pressure change from insulators (R >10 M?) to conductors (R < few Ohms). The two sensors are wired in series and the signal is fed directly to the controller of the wrist joint.











    A few words on the control


    Each axis of motion is controlled via a 'Supermodified' combo. The arm was built using the first generation of Supermodified controllers which work in conjunction with a magnetic encoder (1024ppr) (
    http://forums.trossenrobotics.com/showthread.php?t=3924). The second generation comes with 4 times the resolution (4096ppr) (http://forums.trossenrobotics.com/showthread.php?t=4021) so i am really looking forward to try out those babes on the second generation 6DOF manipulator. Supermodified controllers are direct replacement boards for the original servo electronics, that allow full PID speed and position control of the servo. Based on the ATMega 368P (fully Arduino compatible with half the footprint of Arduino nano and 4MHz faster) also allow for controlling 4 digital IOs, as well as 4 analog inputs.

    So for example the gripper’s pressure sensors need not be fed back to the main controller, since the Supermodified controller board of the gripper can handle the analog signal from the sensors and report back to the main controller (in the video that would be the PC). The Arduino merely plays the role of a USB to I2C bridge. Btw the gripper’s DC motor has been a recent addition since its predecessor - a tower pro 90 micro - proved inadequate. The tiny DC motor powers the dual parallel-link finger assembly by using a tiny pulley system having an extra-strong thread acting as its timing belt
    )).

    The remaining servos have all been “Supermodified”. The joint hierarchy is as follows:


    Shoulder (yaw) -> Shoulder (pitch) -> Elbow -> Wrist -> Gripper


    The wiring is fairly simple and straightforward since each Supermodified controller can be ‘daisy-chained’ with other Supermodified controllers, minimising complexity and offering a neat end-result. The whole manipulator arm wiring effectively comprises a single 4 core cable (Power and I2C comms), running from one servo to the next according to the hierarchy above. I2C comms are then fed to the Arduino, which for the time being acts as a USB (com) to I2C communication-bridge between the host computer and the Supermodified servo controller network.
    Last edited by Antonb; 05-17-2010 at 10:29 AM.

  2. #2

    Re: Handmade 5DOF Manipulator with tactile feedback

    Very impressive work. Bonus points for style and being handmade.

  3. #3

    Re: Handmade 5DOF Manipulator with tactile feedback

    That a very nice arm and control system. I really like the rotary gripper.

    I per-ordered supermodified v2 a while back with the plan is to build a 6 axis robotic arm.

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  5. Re: Handmade 5DOF Manipulator with tactile feedback

    Thanks for the positive feedback. Just to let you know im currently working on a 6DOF manipulator based on the Supermodified and I am soon going to release the designs online

  6. #5

    Re: Handmade 5DOF Manipulator with tactile feedback

    Cool... My son and I visited the local hardware store this weekend to pick up materials to build the links.

    Do you have the Supermodified v2 boards? I pre-order them a month or two ago and I'm still waiting.

    Anyway, the idea is to wire up an embedded web server.

  7. #6
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    Re: Handmade 5DOF Manipulator with tactile feedback

    Beautiful work! I love the aesthetics. It comes off pretty biological without looking too freaky or industrial. I like!
    "If A is a success in life, then A equals x plus y plus z. Work is x; y is play; and z is keeping your mouth shut."
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  8. Re: Handmade 5DOF Manipulator with tactile feedback

    Quote Originally Posted by MikeG View Post
    Cool... My son and I visited the local hardware store this weekend to pick up materials to build the links.

    Do you have the Supermodified v2 boards? I pre-order them a month or two ago and I'm still waiting.

    Anyway, the idea is to wire up an embedded web server.
    The Supermodified arrived today straight from the assembly line

    We will be sending-out invoices by Friday. I am pretty pleased so far

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    Re: Handmade 5DOF Manipulator with tactile feedback

    Very nicely done, quite impressive to me! Makes me contemplate as to whether I'm going to hack my very first servo or not! Ah, decisions, decisions!

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    Re: Handmade 5DOF Manipulator with tactile feedback

    Hi, Anton.

    That's a quite amazing project you built.
    I'm curious about the tactile sensor do you use.
    Could you tell what brand, spec and where I can buy it?
    I'm planning to make a manipulator with compliance control ability.
    Looking forward for your reply.
    Thanks

  11. #10
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    Re: Handmade 5DOF Manipulator with tactile feedback

    hats off to your hardwork, dude. i can see a lot of passion and time went into the design and cutting each part.

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