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# Alternative rolling robot moon explorer

Gyroscopic propulsion (no, not reactionless)
 (+5, -1) [vote for, against]

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.
 — Ling, Dec 20 2004

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]

 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?

 [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.

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?
 — bungston, Dec 20 2004

[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.
 — Ling, Dec 20 2004

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.
 — Belfry, Dec 20 2004

//Some clever trickery would be needed for "up" detection, and calculation of the required movements (especially for compensation of the 90 degree force).//
 — Ling, Dec 20 2004

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?
 — bungston, Dec 20 2004

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.
 — bungston, Dec 20 2004

[bungston], take a look at the link.
 — Ling, Dec 21 2004

Tantalizing stuff. Too tantalizing.
 — bungston, Dec 21 2004

 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!

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.
 — bungston, Aug 13 2006

 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.

To work in water, the sphere would need to rotate like a paddle wheel.
 — Ling, Aug 13 2006

 /But I was my physics explicit!/

 what the heck does that mean?

The boat! If I stand on a skateboard holding a spinning gyroscope, and tilt the gyroscope, can I cause the skateboard to roll forward?
 — bungston, Apr 28 2010

 Yes. But if you continue the movement, the force will be reversed in the other half of the path.

 Gyroscopes can generate rotational movement but not translational movement.

Blah, blah, "reactionless drive", blah, "Non-Newtonian propulsion", blah.
 — 8th of 7, Apr 28 2010

 /Gyroscopes can generate rotational movement but not translational movement./

 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.

 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.

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.
 — bungston, Oct 07 2013

 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.

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.
 — scad mientist, Oct 07 2013

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.

 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.

I would think anything containing a spinning flywheel would also be subject to powerful gyroscopic effects, needed or not.
 — bungston, Oct 08 2013

//..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.