Sphere Bots Get Some New Skills


Spherical robots , or in this case RC vehicles are pretty versatile. They travel about the same on most terrains, including water in some cases. That’s not to say that they travel particularly well on those terrains though. The common problem is that they can’t really climb over bumps very well, until now. We’ve seen a few versions of sphere bots, but they all seem to need fairly level smooth surfaces, aside from that one that went in the water. We hadn’t seen any that really had the oomph necessary to climb stairs though. Actually, we still haven’t seen that, but he says it can in the interview you can watch after the break.


34 thoughts on “Sphere Bots Get Some New Skills

  1. cyc4015: Nah they seemed to be saying it uses gyroscopes to provide a kind of solid base to push off. I guess you could also use a momentum wheel in the same plane as the axle if you wanted. That might actually be easier.

  2. Agree with others previous comments – it’s easy to make a sphemical bot with plain motors and drive it around. You can never get great steering, or more importantly stopping control with these designs though

    This implementation really is excellent – the gyro seems to make it much more stable and controllable.

  3. @Greg: real nice !

    Is that the hydraulic door opener that uses the building water supply as a source? Great out-of-the-box thinking :D

    How do the gyroscopes help? Are you using two like this [http://blog.makezine.com/archive/2009/09/how-to_use_hard_drives_for_image_st.html] to add ‘inertia’ to the pendulum part? Or just electronic ones to do automatic closed-loop stabilisation?

  4. It certainly is. Making it hydraulic was more fun than just slapping an electric linear actuator on there. And it has the added benefit of being manually overridden and incredibly quiet in operation.

    The gyroscopes work by storing huge amounts of angular momentum. They are used in way that makes them whats called control moment gyroscopes (http://en.wikipedia.org/wiki/Control_Moment_Gyroscope). They arent used for stability like in that example with harddrives. Their stored angular momentum is dispensed to create extra torque.

  5. So your robot still changing the gravity center to move arround, but when is stuck in a hole or something similar you use the gyroscope to create extra torque and get out from there no?

    By the way, awesome robot where do you get the sphere?

  6. @Greg: indeed, hydraulics rock :)

    So I suppose (also from the pictures) there are two gyros spinning in the horizontal plane, I think you are only using them as a angular momentum storage, and then simply driving the ball against this momentum-heavy pendulum. (since attempting to tilt them will cause them to react by tilting left to right in opposite directions, which they cannot)

    But how about simply attaching the gyros to the inside of the sphere on left to right gimbals, without using a pendulum, and then tilting them?
    This should create forward torque I think, and would sound more like a CMG to me, no?
    Not sure about turning though…

  7. @Gizer20: Yes the robot still shifts center of mass for normal motion. The stored momentum gives the pendulum more than just gravity to push against to create torque. It uses both at the same time.

    The shell is actually a polycarbonate gumball machine globe.

  8. @Jonathan: The gyros are actively driven to rotate left/right to generate the precession torque. So they are in fact used like CMGs.

    The reason you can’t just use CMGs is because you can only store so much momentum. By conservation of angular momentum, you can only generate a certain amount of torque*time before your CMG system is ‘depleted’.

    Steering is accomplished using the pendulum, but can be supplemented by the CMGs as well (in a slightly different/more complicated configuration).

  9. @Mic: The control system for this robot is significantly more complex than for the segway. I’m building a custom system with an IMU and encoders on all the parts. I’m also developing the dynamic equations of motion mathematically, which are all delightfully non-linear. After that I’ll be able to write the software to cancel out all the wacky movements.

  10. @Greg: how is it that the gyro you have on the table is staying up? Is the lighting in the video obscuring something that I should be seeing or is it just a metal stick with the spinning ball parts on the end…and standing up on its own?

  11. Greg you’re absolutely right. What I meant to convey was the idea of compensation. You would obviously need a more complicated and specialized system, but my proposed concept has merit. Something designed to measure and compensate for g forces. I mean you’re right it is more complex, but you still need a computer to measure forces and to compensate for the ones that mess up your control inputs. That’s what I tried to say, but, a segway is a lame example as you have said =P Awesome creation, serious props man.

  12. @ Dan Cardin

    the stick with the ball has a gyro in the ball. when the gyro is spinning, it keeps itself positioned in relation to its original position and resists changes in yaw thereafter. once the gyro stops, the whole assembly falls.

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