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Inspired by [spacemoggy].
A search on the net reveals all spherical robots to be pendulum based.
There are several problems with this type, which I propose to solve:
1. The pendulum motion can be upset when the sphere rolls uphill, sideways, or downhill suddenly. The pendulum can get
the wrong angle easily. I expect that the motion will be oscillatory after every disturbance.
2. There is a limit to the ability of climbing a slope. The position of maximum pendulum effect will be when it is horizontal. The centre of gravity will be well inside the sphere. Vertically down from the centre of gravity will be the point where the sphere cannot overcome the obstacle.
Consider this:
A gyroscope is installed on a 3 axis gimbal. The angle of the joints on the gimbal are driven by servo motors. The gimbal is mounted inside a sphere.
As the servo motors try to change the angle of the gyroscope, the gyroscope resists. Finally the sphere rotates instead.
Some clever trickery would be needed for "up" detection, and calculation of the required movements (especially for compensation of the 90 degree force).
Since the force that rotates the sphere depends on the servo motor force (and not the limit of a pendulum weight), then the sphere would have the capability to roll up a steeper incline, and even be able to push something else with considerable force.
Link to [spacemoggy]'s original idea
Rolling_20Robot_20Moon_20Explorer
With several links to robotic sphere solutions [Ling, Dec 20 2004]
For bungston
Enhanced_20gyroscopic_20force_20generator
A well known academic spent 20 years of his life on this type of concept. [Ling, Dec 21 2004]
Robots propelled by internal flywheels.
http://web.mit.edu/...ng-robots-1004.html
Is this not gyroscopic propulsion? The distinctions between a flywheel and a gyroscope are not clear to me. [bungston, Oct 07 2013]
[link]
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I can feel my brain heat up when I try to do thought experiments involving gyroscopes. To simplify the experiment, let's imagine a gyro mounted in a single gimbal which in turn is mounted inside a wheel. Will the wheel roll? To get the wheel to roll clockwise, I imagine the gimbal must be carried around by its servomotor in a counterclockwise motion. Won't the gyro just oppose the servomotor and make it work harder to turn the gimbal, leaving the wheel stationary? |
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[later] - opposing the servo will cause a force to be exrted on the servo mount, the wheel, so yes, the wheel will roll. So this would work. |
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If I were going to make a spherical robot, I would propel it like a hamster ball: a little car inside to drive in the desired direction. What is this pendulum thing about? |
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[bungston], I put several interesting links in the first "rolling robot moon explorer". The pendulum does the same thing as your little car, except that it is pivoted essentially from the centre of the sphere. The angle of the pendulum is maintained by a motor and gearbox, so as the sphere rolls the pendulum is lifted accordingly. But of course, the pendulum pivot has to be fixed to the sphere somehow, and that is what gets in the way. Hence the two axis solution in one of the links, with a gyro to turn left or right. |
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This wouldn't work with a spherical robot because of the way gyroscopes behave when you try to rotate them: if you rotated the gyroscope backwards to make the robot go forwards up an incline, it would do that 90 degree reaction thing (I can't remember the proper name) and roll to one side instead. I think this would work using a cylindrical robot though, or two wheels with seperate driving gyroscopes sharing a common passive axle. |
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//Some clever trickery would be needed for "up" detection, and calculation of the required movements (especially for compensation of the 90 degree force).//
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If this robot were in a zero-gravity situation, action of the servos would get the outer sphere revolving in the opposing direction. What if there were two gyroscopes side by side, revolving in opposite directions and they were tilted in the same direction? Would the robot fly thru space? |
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Looking forward to hearing about the spaceship. But it seems to me that you definitely could make a boat that was powered by an onboard gyroscope. The boat would move forward on tilting the gyro within its gimbals. This would obviate the need for messy propellers, oars, etc. A two-way gimbal could also obviate the need for a rudder. |
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[bungston], take a look at the link. |
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Tantalizing stuff. Too tantalizing. |
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I was thinking again about the
gyroscope powered boat. I checked the
links again but could not find an
explicit discussion of the boat. Perhaps
a boat is a more specific example of the
general principles dealth with, which I
admit are sometimes a tad beyond me.
But I was my physics explicit! |
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The boat would be good. The
gyroscopic bits would be high and dry,
without the mess of water interaction.
The bottom of the boat would be nice
and flat. |
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bungston, this idea does not use reaction-less force. To roll the sphere, the gyroscopes have torque applied, via a gimbal, by servo motors which are attached to the sphere. The gyroscopes resist the application of torque, which means two things happen: the servo motors starts driving the sphere in the other direction, and the gyroscopes tilt to one side. (I use plural, since there are likely to be 3 sets inside the sphere).
To keep the sphere rolling, the servos will now have to run at constant speed. |
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To work in water, the sphere would need to rotate like a paddle wheel. |
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/But I was my physics explicit!/ |
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what the heck does that mean? |
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The boat! If I stand on a skateboard holding a spinning gyroscope, and tilt the gyroscope, can I cause the skateboard to roll forward? |
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Yes. But if you continue the movement, the force will be reversed in the other half of the path. |
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Gyroscopes can generate rotational movement but not translational movement. |
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Blah, blah, "reactionless drive", blah, "Non-Newtonian propulsion", blah. |
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/Gyroscopes can generate rotational movement but not translational movement./ |
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AU CONTRAIRE MON FRERE! Marvel at linked cubical robots. I am glad those MIT layabouts finally got around to building little robots propelled by internal spinning wheels. Now if there is hair splitting as regards "flywheel" vs "gyroscopes" this must be followed by lengthy scholarly exposition, or it is all sour grapes. |
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I would like to see that same flywheel innards mounted in a rubber ball robot. It would be hamsterballerific! But I think the hopping would be hard for a sphere without an edge to push off from. |
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I suspect that those cubical robot videos are kind of like my own basketball videos. Only the scenes where the ball glides effortlessly through the net are kept. The one where the ball misses everything and knocks my Vespa down the hill is omitted. |
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Funny, as I was reading this idea and annotations I was thinking that it would simplify things and work just about as well to use flywheels rather than gyroscopes. You'd still need a pendulum based system to allow the flywheels to be accelerated without moving, but the flywheels could be used for limited time periods to allow for rapid acceleration, climbing short steep slopes, etc. |
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The MIT modular robots work similarly in concept: being able to accelerate the flywheel gradually because the cubes won't roll easily, but hitting the brakes hard to make the cubes roll. |
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Re: flywheel vs. gyroscope (IMHO):
A flywheel stores rotational kinetic energy, delivered via a shaft.
A gyroscope is essentially a "black box" that resists (or converts) motion about two axes. The fact that the "black box" contains a rotating element is largely irrelevent to it's use (the axis alignment needs to be know, but little else).
The little cube robots (which are awesome) use a flywheel, transferring the rotation of the flywheel into rotation of the robots frame. Dunno if they also use the gyroscopic effects of the flywheel in the control of the robot. |
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I see. So for optimal use a gyroscope stays spinning
at a constant rate, that its resistance to change of
position also stay constant. A flywheel would be
sped or slowed as energy is available or needed. |
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I would think anything containing a spinning
flywheel would also be subject to powerful
gyroscopic effects, needed or not. |
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//..also be subject to...//
Most definitely. It means you need to be very careful about where and how you mount a flywheel, say, in a vehicle. |
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