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Thread: Maxwell: A Mobile Manipulator

  1. #1
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    Maxwell: A Mobile Manipulator

    I wanted to briefly introduce the robot I've been working on for the past couple weeks. Maxwell is a human-scale mobile manipulator powered by ROS and an ArbotiX.



    A cool feature of this bot is that not only does it sport lots of sensory and a cool arm, but Maxwell breaks down into short sections that fit in a Pelican case. It only takes about 5 minutes to break down or assemble the robot:



    I've posted more pictures and details on my blog: http://www.showusyoursensors.com/201...g-maxwell.html for now, I'll expand this post shortly.

    -Fergs

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    Re: Maxwell: A Mobile Manipulator

    You never stop to impress me with all your projects.
    This one looks very interesting.
    You say that the wrist has a roll function too? It was very hard to see it on the pictures though.

    Looking forward see your next post.
    Kåre Halvorsen aka Zenta
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    Re: Maxwell: A Mobile Manipulator

    Is the arm made up of mostly RX servos? And then a couple of AX's at the gripper? Must have some good stability in the arm from the upgraded servos.

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    Re: Maxwell: A Mobile Manipulator

    Looks really cool, and some very very nice servos :-)
    How hard is it to get ROS working with your own gripper?
    What library will you/ can you use for that?

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    Re: Maxwell: A Mobile Manipulator

    Quote Originally Posted by Zenta View Post
    You never stop to impress me with all your projects.
    This one looks very interesting.
    You say that the wrist has a roll function too? It was very hard to see it on the pictures though.

    Looking forward see your next post.
    Yep, there is an AX12 right behind the 2 AX-12s used for the gripper fingers. It allows the wrist to rotate to grasp an object from different angles. I'll try to get a better picture up soon, but you can sorta see the top side of the servo in this pic (the horn of the AX-12 is connected to the RX-64 hinge bracket):



    Quote Originally Posted by elaughlin View Post
    Is the arm made up of mostly RX servos? And then a couple of AX's at the gripper? Must have some good stability in the arm from the upgraded servos.
    Yep, my blog post had a bit more detail: "Maxwell's arm is constructed from 2 EX-106 (shoulder lift and elbow flex), 2RX-64 (shoulder pan and wrist flex), and and 3 AX-12s (one for wrist roll, and two to form a gripper). In all honesty, it only needs the one EX-106 in the shoulder, but I didn't have any brackets that fit the RX-64 at the moment. The actual gripper fingers are temporary, I have much better ones in the works."

    Quote Originally Posted by Amp View Post
    Looks really cool, and some very very nice servos :-)
    How hard is it to get ROS working with your own gripper?
    What library will you/ can you use for that?
    Thanks. I'm not going to lie: getting a custom manipulator up and running in ROS is a bit of a task. I'm using the arm_kinematics package to do IK -- with my own wrapper around it do deal with the 5DOF-ness of the arm. I'm then using the collision_environment to apply collision free kinematics (still in progress), and tying it all together with my own simple version of move_arm (eventually I'd like to use the actual move_arm -- but it currently has some PR2 dependencies I'm avoiding).

    The good news is: I firmly believe in open source. All of the trajectory planning aspects will be integrated into upcoming ArbotiX package releases for ROS. This should make it fairly straight forward to create a custom URDF+YAML description of your AX/RX servo arm, connect it to an ArbotiX and go forward with arm planning. Maxwell's description files will also be posted shortly (some already are, but it's somewhat of a mess, I was working rapidly over the weekend to get him operational for a full day of demos today).

    -Fergs

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    Re: Maxwell: A Mobile Manipulator

    constructed from 2 EX-106 (shoulder lift and elbow flex), 2RX-64 (shoulder pan and wrist flex), and and 3 AX-12s
    Multi-servo-type approach makes a lot of sense to me, especially when I look at my own arm which has one of the biggest muscles in the body to move arm(proper) and so much smaller muscles to move my fingers.

    This setup still a lot more affordable than $160k(?) price tag of Barrett arm too.

    Too bad ArbotiX can't do RX and AX at the same time...

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    Re: Maxwell: A Mobile Manipulator

    Quote Originally Posted by RobotNV View Post
    Too bad ArbotiX can't do RX and AX at the same time...
    Stick around..... there's a super secret prototype in the base of Maxwell....

    -Fergs

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    Re: Maxwell: A Mobile Manipulator



    -Fergs

  9. Re: Maxwell: A Mobile Manipulator

    You have done a great job with Maxwell. There could be commercial potential for such a robot.

    May I ask what material the base is made of?

    Also, are you concerned with the height of the arm that the robot, even having a low center of gravity, will easily tip over when the arm is grabbing an item?

    Kevin

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    Re: Maxwell: A Mobile Manipulator

    Quote Originally Posted by maitri982 View Post
    You have done a great job with Maxwell. There could be commercial potential for such a robot.
    Thanks.

    May I ask what material the base is made of?
    It is laser cut ABS, mostly 3/16" thick but the top piece is 1/4" thick.

    Also, are you concerned with the height of the arm that the robot, even having a low center of gravity, will easily tip over when the arm is grabbing an item?
    Not really -- Maxwell is about 15lbs fully loaded, 10 pounds of that is in the base. His rear end may tip up just a bit, but by keeping the arm speed slow, he doesn't get enough momentum to carry all the way to a tip over.

    He probably won't be able to negotiate ramps as well as something like a PR2 -- but that is not an issue in the environments I'm working in currently. Maxwell has successfully negotiated a number of very large door and carpet transition thresholds without incident.

    -Fergs

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