This is an idea for a robotic toy, consisting of a sturdy plastic sphere, which has one robot rolling around inside it, and one robot balancing on top of it, and of course a remote control.

The two robots have a lot in common with one another.

They both have holonomic drives, accelerometers, gyroscopes, a digital compass, a kalman filter or two, a radio receiver, and a proportional–integral–derivative controller.

Each bot's drive system is surrounded by a rigid airtight shell, the edge of which has a very tiny amount of clearance between itself and the ball. Each shell has a fan which constantly removes air from inside the shell, essentially making it into a suction cup. Atmospheric pressure on the outside of this shell pushes the shell (and the drive wheels!) firmly towards the ball.

This suction is similar to what allows wall climbing toy cars to work. It reduces the chance of accidental separation, and it means that the bots can position themselves *anywhere* on the ball, including at the balls horizontal equator, without falling off.

The remote controller has (at least) two two-axis control sticks, one controlling each bot. There's also a digital compass in it, like the one in the bots.

Each bot constantly tries to maintain a position on or in the ball at a specific angle -- namely, however much that bot's control stick is pushed away from the neutral position.

If either control stick is not being pushed at all, the corresponding bot will try to remain exactly at the top or bottom of the ball.

If either control stick is pushed all the way in any direction, then the corresponding bot will try to try to remain at the equator of the ball.

Each bot also has a target angle relative to north that it tries to seek -- this is the angle of the remote control relative to north *plus* the clockwise/counterclockwise angle of that bot's control stick.

Basically, if you face towards the bot, and push a control stick up (towards the bot), that bot will try to move to the side of the ball which is away from you. If you push a control stick rightwards, that bot will move the the side of the ball which is on your right side, etc.

If it's in the budget, there should be a camera on the outer bot, with a remote controlled pan motor which spins the head, and perhaps also a tilt motor which angles the camera up and down.

In case you're wondering, why *two* bots, the answer is simple -- it lets the bot move in one direction, while angling it's head in another, and perhaps pointing it's eye in a third. Just don't use this power to look up skirts, that would be mean. And silly.

This lets your BB8 or BB9E seem much more "alive" than what you can do with just one bot. Decorating the ball and outer bot to looks like one of these two Star Wars droids is, of course, absolutely mandatory.
-- goldbb, Nov 29 2017

Sphero BB8 http://www.sphero.com/starwars/bb8
Mostly baked...? [neutrinos_shadow, Nov 29 2017]

To allow the bot to do more extreme camera angles, and some silly poses, there might be a toggle switch on the remote which changes how the outer (head) bot orients itself.

When in the "up" position, the headbot operates normally.

When in the "down" position, the headbot's angular distance from vertical is doubled from normal.

This means if you've got it's control stick *halfway* from neutral, it puts itself on the ball's horizontal equator, and if the stick is more than halfway from neutral, it moves *below* the equator.

It's a good thing it's wheels are surrounded by a suction cup, right? Anyway, an added feature of this is, if the ball is stuck somewhere (perhaps in a sand dune?), the bot's head can be pushed against the ground to help unstick it.
-- goldbb, Nov 29 2017


//rigid airtight shell//
//removes air from inside the shell//
This could be a problem...
Also, if the "head" bot has full freedom (as it would seem from your description), you don't need the extra pan/tilt functionality; the movement of the head bot itself will take care of that. (I don't know why Star Wars needed to add the "non-spinning" collar to BB8; the head is free to move anywhere anyway.)
-- neutrinos_shadow, Nov 29 2017



random, halfbakery