Making a free-moving 360 degree robot?

So I was playing with an idea and it kind of came to a standstill recently. The idea was making a robot that would follow you but also have the movement capabilities of going sideways without moving it's front wheels. Sort of like going from front wheel drive for forward motion, into a 'side wheel' drive to move to the right.

I was thinking about ball bearing wheels and using some sort of dual X,Y axis to move forward and sideways. However it occured to me that this wouldn't work since you wouldn't be able to move the front 2 and the back 2 sets of wheels independently without them all moving the same direction at once.

A provided example of the problem would be to make a traditional right-angled turn like a car and have only the front side to guide the robot. But if you used 2 axises to move forward/back and right/left (driven by two motors) and had them attached to the 4 ball-bearinfwheels then it'd move the entirety of the robot sideways and forward at the same time.

The main goal would be able to make a robot that can move like a car, but also have the range of motion of a free-moving dolly. So if the robot is on a larger scale and is approached from the side, it could shift it's mass over without getting stepped on.

How feasible is this concept and what would be some creative ways to approach this? Would you have to use 4 motors with additional axises and/or wheels or is there a more efficient approach?

The simplest solution seems to be the ability to steer all wheels through 90°.

There are some (very expensive?) "wheels" that have the capability to move in any direction without steering - sorry, I have forgotten what they are called. I think Nasa devised them.

...R

Robin2: The simplest solution seems to be the ability to steer all wheels through 90°.

There are some (very expensive?) "wheels" that have the capability to move in any direction without steering - sorry, I have forgotten what they are called. I think Nasa devised them.

...R

Omni-wheels?

Robin2: The simplest solution seems to be the ability to steer all wheels through 90°.

There are some (very expensive?) "wheels" that have the capability to move in any direction without steering - sorry, I have forgotten what they are called. I think Nasa devised them.

...R

Oh wow. Those are really cool and well thought out. How would you drive them sideways though? You'd still run into the axis problem

There are online videos of things like forklift trucks and wheelchairs fitted with various flavours of omniwheels - well worth looking at for ideas.

AWOL: Omni-wheels?

Thanks for the link.

It was actually the Meccanum Wheel that I was thinking of. And now I can see that it was invented in Sweden, not by Nasa.

...R

The vehicle can move on screws rather than wheels or tracks. Changing the relative rotation of the screws would allow the vehicle to move forward or backwards or sideways.

Here is a Russion screw driven all terrain vehicle, it moves sideways at the start of the video and seems capable of handling a lot of ground a conventional 4x4 would have no hope on; https://www.youtube.com/watch?v=ETsL2EjZQGo