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Thread: choosing platform for project (biped, torque control servo, advanced kinematic)

  1. Question choosing platform for project (biped, torque control servo, advanced kinematic)

    I'm choosing platfom for my project - biped robot with advanced kinematics.
    And want to concentrate mostly on kinematics controller (I consider it to be well thoretically developed ).

    Robot
    • biped (6 DOF per leg + 2 for body/head)
    • 3 force resistors on each foot (2nd stage of project)
    • 1 gyro + 1 3D accelerometer on body/head (2nd stage of project)


    I need to perfom 2 kinds of control
    1st "common"
    • read positions from servo for building frames
    • basic (position) control over servos

    2nd "advanced"
    • torque control over servo (torque as input, position/velocity as output, servo tries to reach and 'hold' torque )
    • feedback from all sensors (force resistors, gyro, accellerometer)
    • lot's of real-time computation on PC for kinematics (later maybe moved to robot, but it's a question 2-3 stages ahead)

    My background
    • no robot building experience (as more from-the-shelf platform as better)
    • programming .net mostly (netduino?)



    appriciate any suggestions or help

  2. #2

    Re: choosing platform for project (biped, torque control servo, advanced kinematic)

    Can you narrow the options a bit for us ?

    What size/height ?

    Any additional payload ( large processor, cameras, guns, etc) ?

    What price range ?


    Whatever, I would recommend something around Robotis servos (Bioloid Premium, Bioloid GP). The standard firmware has limited control of torque, but alternative servo firmware has been developed for more direct control of servo parameters.

  3. Re: choosing platform for project (biped, torque control servo, advanced kinematic)

    >>What size/height ?
    some "common" size
    (20-80cm)

    >>Any additional payload ( large processor, cameras, guns, etc) ?
    No additional payload.
    Large processor in PC (see below)

    >>What price range ?
    <1k is good
    1-2k acceptable
    2k+ have to think

    >>Whatever, I would recommend something around Robotis servos (Bioloid Premium, Bioloid GP). The standard firmware has limited control of torque, but alternative servo firmware has been developed for more direct control of servo parameters.
    could you give any link to alternative firmware? (fast search didn't help)

    I consider Bioloid as primary option.
    Question is how I can online control Bioloid from PC? Hardware?
    (servo torque control + sensors feedback = consider amount of data)
    Software? .net with appropriate libraries?

    Project is about 'simple' movements like straight walking, no AI-related tasks.

  4. #4

    Re: choosing platform for project (biped, torque control servo, advanced kinematic)

    If you think standard servo firmware will not meet your needs, start here:
    http://robosavvy.com/forum/viewtopic.php?t=7021

    or here:
    http://robosavvy.com/forum/viewtopic.php?t=6832

  5. Re: choosing platform for project (biped, torque control servo, advanced kinematic)

    I guess that's exactly what i need. Thanks!

  6. Re: choosing platform for project (biped, torque control servo, advanced kinematic)

    Bioloid platform is my choice.

    One more moment. I need feeadback from biped feet
    - moment it touches/leaves ground
    - how foot is touching ground (heel or toe, righ or left part : 3 points is enough)
    - touch force approximate mesurement is advantage (but not necessary)

    What sensors should I choose - FSR, Positional Feedback Sensors, Touch Sensors?
    Any Bioloid projects with such sensors? Do I need any special controller?

  7. #7
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    Re: choosing platform for project (biped, torque control servo, advanced kinematic)

    Here is a link to something...

    http://www.huv.com/blog/2007_05_01_archive.html

    Hope this helps.

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    Re: choosing platform for project (biped, torque control servo, advanced kinematic)

    The stock foot plates sold by Robotis have indentations for four 0.2 inch FSR. Unfortunately the CM-510 and CM-700 are the only two controllers they sell that have Analog to Digital Converter pins but both have only six of them, so you could not directly sense all four corners of both feet using just a Robotis controller. If you are not using the default Humanoid configurations (using Bioloid frames and designs), the RoboPlus Motion software is not going to be very helpful and would not anyway if you really are serious about making your own IK engine. The Arbotix does appear to have 8 ADC pins available and has been used extensively by many many other users on these forums, with some IK running onboard (just search for "arbotix" or "pypose"). All you would need to do to use the FSRs is make a voltage divider circuit with an FSR and an additional resistor, connecting their common electrical connection to an ADC pin.

    Kind of pointless if you go with the Arbotix, but included for completeness.
    If you wanted a device on the dynamixel bus, I would recommend Jon Hylands' board. Unfortunately, it has been discontinued and the only place I have found any in stock is a single foot at RobotShop. Fortunately, Jon has most or all of the source code on his repository (see here for more) and the board's design files and list of materials may also be there if you want to try building your own.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    [git][mech][hack]
    gives free advice only on public threads

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