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Thread: Best way to build a "Gorilla" fighter?

  1. Re: Best way to build a "Gorilla" fighter?

    I'm familiar with those bots, but I'm not looking for a modular design. I'm thinking something that would have more of a distinct difference between the arms and legs, but still have arms that could adapt to be used as rudimentary front legs when used as a quad. The one I'm thinking of would have a more mammalian-inspired construction - I was thinking something inspired by a werewolf (yes, I'm a nerd, and I'm proud of it) - something that still has an animalistic physiology but has been warped to stand upright. I'm thinking digitigrade legs would be a good way to illustrate this type of concept...

  2. Re: Best way to build a "Gorilla" fighter?

    That's idea questions my assumption that I should have stronger leg servos.
    ________
    Honda TL125
    Last edited by UncleBob; 01-20-2011 at 11:35 PM.

  3. #13
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    Re: Best way to build a "Gorilla" fighter?

    Quote Originally Posted by rudukai13 View Post
    I was thinking something inspired by a werewolf (yes, I'm a nerd, and I'm proud of it) - something that still has an animalistic physiology but has been warped to stand upright. I'm thinking digitigrade legs would be a good way to illustrate this type of concept...
    Ok then...Some questions...

    Are you thinking dynamixel or hobby servos? With hobby servos you could get away with weaker servos as you move down the arms, and relatively strong servos where needed in the legs and such.

    How big are we talking

    Lets just assume your talking hobby servos

    for the arms I would go with
    shoulder rotation
    Shoulder lift
    Elbow
    Wrist Tilt (NOT NECESSARY)
    Wrist lift (NOT NECESSARY)
    possibly gripper if you are talking about grappling. I would extend the arms between shoulder and elbow, and again between elbow and wrist. You could loose the wrist servos and just have the arms end in points for walking on. This would save weight, and take some of the strain off of the servos.

    I'm still thinking RX-24fs for this one. If you go with hobby servos HS 5990s? and hs 5645s...

    Legs, As short as possible
    Hip tilt
    Hip lift
    Knee
    Ankle lift
    Ankle tilt.

    The reason I brought up Gigerfu is because you could use long arms, coupled with shorter legs and then develope a mammilian inspired quad gate by leaning forward and using the arms for walking. I guess you could make the feet smaller because you wouldn't be balancing on them for walking.

    Again though your ankle and knee servos are going to take a pounding.

    Hope this helps.

    DB

  4. Re: Best way to build a "Gorilla" fighter?

    I'm liking the idea of keeping the arms fairly simple, just elongating the segments between the joints. That ought to help on the weight front. With the legs, however, I'm thinking I'll need to add one more joint between the knee and ankle for aesthetic purposes. I'd like to make the legs more canine-inspired, with the look of an animal that walks on it's toes. I'd definitely go with dynamixels.

  5. Re: Best way to build a "Gorilla" fighter?

    Wondering what would be the best way to construct the leg...Take a look at the following picture:



    The area of importance here is the leg area, but this is a hypothetical skeletal structure from a werewolf. Notice it's walking on it's toes. This is effectively the type of leg design I'd like to construct. It's naturally a very nimble and agile design (look at any fast-moving land mammal in our world and you'll see this type of physiology). This natural agility should certainly help it when moving about in a wrestling match, and should set it apart from the rest of the competitors. The problem is trying to figure out where to put the ankle servos - on the actual "ankle" joint of the leg, or simply where the leg connects to the "toe" section. Putting it in the toe joint will require adding a dof to each leg, but will make it overall more stable...So what does everyone suggest?

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    Re: Best way to build a "Gorilla" fighter?

    From my limited knowledge in robotics, I think this is a very daunting task.

    1) Making a reverse knee (werewolf style) robot,
    2) that has agility like a mammal

    Please take a look at Tybeius' Hagetaka Mech. It looks awesome, but was done with stonger servos.

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    Re: Best way to build a "Gorilla" fighter?

    Quote Originally Posted by rudukai13 View Post
    . Notice it's walking on it's toes. This is effectively the type of leg design I'd like to construct. It's naturally a very nimble and agile design (look at any fast-moving land mammal in our world and you'll see this type of physiology). This natural agility should certainly help it when moving about in a wrestling match, and should set it apart from the rest of the competitors.
    I don't think it makes sense to look at biological inspiration so much when your actuators are a far cry from those used in biological systems. Biological systems are lightweight, compliant, able to temporarily store energy, controlled with an incredibly good working mix of feedback and feedforward control etc., all of which you can't really do on a level even remotely comparable level to biological systems with affordable (and even non-affordable) servo systems
    Successful humanoid robots (for example in Robo-One and RoboCup) make good use of available servo tech, but they generally don't tend to be too bio-inspired (walking with bent legs, sidestepping etc.).

  8. Re: Best way to build a "Gorilla" fighter?

    So what I'm hearing you guys say is that it wouldn't create a positive effect to change the leg design. I guess then my question is would it do any harm to the stability of the robot? Hagetaka's leg design is just about exactly what I'd be going for.
    Last edited by rudukai13; 10-14-2010 at 07:22 PM.

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    Re: Best way to build a "Gorilla" fighter?

    Quote Originally Posted by rudukai13 View Post
    So what I'm hearing you guys say is that it wouldn't create a positive effect to change the leg design. I guess then my question is would it do any harm to the stability of the robot? Hagetaka's leg design is just about exactly what I'd be going for.
    I have to agree with S.K., that we shouldn't try to make robots look too much like biological counterparts. We *can* learn something from their dynamic nature and use of feedback, but yes, the servos are very different from nature's solution (especially in the power to weight ratios).

    As for Hagetaka, it's not a very efficient design (hence why Andrew has moved on). The big thing here is that 99% of bipedal robots are using some form of ZMP walking (zero-moment point), which generally consists of shifting weight from one foot to another while shifting the body forward. A robot with wide hips, such as Hagetaka, doesn't work too well with ZMP. Biological solutions don't walk like this -- they use active feedback, and are basically in a continuous state of falling. Creating such a system is non-trivial, as can be evidenced by the years of research that has failed to yield a real solution.

    -Fergs

  10. Re: Best way to build a "Gorilla" fighter?

    So what about creating an extended leg design without the wide hips of Hagetaka? Simply taking the usually humanoid leg design and adding an extra dof between the knee and ankle joint?

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