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Thread: RCMP

  1. #1
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    RCMP

    Introducing RCMP (Royal Canadian Mechanized Police). This one is getting flashing Red & Blue LEDs.

    Woodstock was fun and a great learning experience. I love the idea of biped Mechs. I'm hoping to vastly improve things in this new project.

    I think the biggest problem with most biped robots (and Mechs especially) is that they are way to top heavy. Not an easy problem to alleviate since the robot only has 2 legs to support the weight and the obvious direction to build is up. With this in mind, I aimed to greatly lowered the COG and maximize carrying capacity over Woodstock while leaving potential to look cool.

    I have been intrigued by all the PLM designs coming out over the past year, their strength & stability is fantastic. I didn't pursue a PLM design at the time, as I was happy with the leg design I had and opted to develop it further. For this project, I've merged the two design concepts into what I hope will be a competitive biped.



    Here's a closeup of the ball linkage I used.



    I kept the overall design of the 3DOF foot I came up with on Woodstock as I found it to be way more stable to balance on. So far the new variation seems better, but I haven't been walking on them yet. The front toes might have too much flex to them, but I'll know for certain soon enough.



    Here's a closer look at the hip/turret section in it's current state. I'm not sure how useful the turret rotation will be just yet. My thinking is that it will primarily be to keep the video image parallel to the ground, but may also help with balance (while shifting weight) once the guns are mounted on the bottom.



    I have mounted the batteries since taking these pictures, they are on the rear of the lower leg and blend in very well. I really didn't like the look the batteries on Woodstock's legs, but it was the only place I found to effectively place them on the leg to keep him from getting too top heavy.

    Insanity? Probably. Fun? Absolutely!

    More soon!

    Cheers!



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    Re: RCMP

    Are there 21 servos in there? That thing is a beast. Can't wait to see it walk.

    Looks like some sort of sci-fi creature with the long backwards legs, and then then torso head hangs down in front. Pretty cool design, I hope it works out.

  3. Re: RCMP

    To be honest, my first thoughts when the image popped up: WTF?

    It looks like a very interesting project, I'm really looking forward to seeing what can be done with such a design, in term of movements, payload, stability, etc.
    Also very curious about how the toe+heel foot will turn out.
    ---
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    Re: RCMP

    One of the first things to come to my mind was this . Very cool looking bot.

    Definitely a compliment, my mind just goes some weird places sometimes... most times actually.
    Last edited by tician; 05-05-2011 at 10:16 PM.
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    Re: RCMP

    [On Woodstock it seemed that the foot design was stable, but that there wasn't much lift elevation; if that was the case will that be addressed with RCMP (cool name btw, reminds me of Fon Davis's Morav project)?] What variant of AX-12's are they? Darn fun looking project kamondelious!
    Last edited by Stobs; 05-05-2011 at 07:43 PM.

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    Re: RCMP

    Quote Originally Posted by elaughlin View Post
    Are there 21 servos in there? That thing is a beast. Can't wait to see it walk.

    Looks like some sort of sci-fi creature with the long backwards legs, and then then torso head hangs down in front. Pretty cool design, I hope it works out.
    hehe, I considered beast as a name. There are 22 servos actually.
    Thanks I hope it works too.


    Quote Originally Posted by Xevel View Post
    To be honest, my first thoughts when the image popped up: WTF?

    It looks like a very interesting project, I'm really looking forward to seeing what can be done with such a design, in term of movements, payload, stability, etc.
    Also very curious about how the toe+heel foot will turn out.
    hahaha, when I first sketched this design up my first impression was, "that is absurd".
    The PLM legs really seem to lift with solidly, I'll have to do some weight lifting test (caught on video) and get a feel for what it can do. The leg is 7DOF, so mobility should be pretty good providing I can do the balancing right. The heel + toe seemed pretty effective on my previous project, but was prone to sudden fall-overs if weight shifted too suddenly to the heel. I think I've improved the design enough that that will be less of an issue, but I definitely need to take care with that.

    Quote Originally Posted by tician View Post
    One of the first things to come to my mind was this . Very cool looking bot.
    lol, thanks, I think. I might have to put a diaper on it and take a picture.


    Quote Originally Posted by Stobs View Post
    [On Woodstock it seemed that the foot design was stable, but that there wasn't much lift elevation; if that was the case will that be addressed with RCMP (cool name btw, reminds me of Fon Davis's Morav project)?] What variant of AX-12's are they? Darn fun looking project kamondelious!
    Woodstock's foot was actually posed about 1" off the ground for his walking gait. The lack in elevation in his step was all gear backlash. This should less of an issue on RCMP as the PLM design helps eliminate some of that. I'd very much like to make a generation 3 police MORAV. Those are so cool looking.
    The 8 servos making up the ankles & feet are AX-12+ and the rest are original AX-12's.

    Thanks everyone for the kind words and interest in my project.

    Cheers!


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    Re: RCMP

    That thing is scary lol :P

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    Re: RCMP

    I came to a couple interesting realizations today.

    First off, the bracket that the linkages on the legs connect to are of no benefit.
    Secondly, I'm not using a PLM design. I have 2 servos doing the job of one. PLM actually provides a mechanical advantage, mine does not.

    I might change the leg configuration in time to actually be PLM, but I'll wait and see how the current setup performs.

    From testing over the weekend, doing a proper (lift a foot off the ground) walking gait would be very difficult. The hips have way too much gear backlash.
    To fix this, I have connected the tops of the hip servos (spanning the turret) with a metal plate so that the turret pitch servos don't effect the legs.
    I have added 2 additional servos to the hips to assist the hip roll servos, but still need to link them to the existing servos.
    The ankle pitch was also a weak point under load, so I've double those up as well.

    Up to a whopping 26 servos, yikes!

    All in all, I'm still feeling good about this design, but that doesn't stop me from feeling like a tool for my mistakes. Doh!

    More pics soon. Video too, if I make it do anything worth looking at.

    Cheers,


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    Re: RCMP

    Good observations about the leg design. I'm looking forward to seeing it walk. It really reminds me of Mr. Snuffleupagus for some reason.

    http://muppet.wikia.com/wiki/Mr._Snuffleupagus

    Edit: I also love the way that it looks like it's carrying it's own brain (Arbotix).
    Last edited by jes1510; 05-11-2011 at 10:04 PM.
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    Re: RCMP

    RCMP looks awesome! Cool name too.

    I am very curious to see how it looks now that you have added more servos to it.

    How do you plan on controlling the legs? Inverse kinematics, static poses or something in between?

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