Let's Make Robots!

4 wheels with 180 degrees turning

I saw a future concept car on a presentation on a documentary on Discovery Channel.

It had 4 motorized wheels, One in each corner (like a conventional car). But each wheel could turn 180.

It would mean that your car could drive in any direction, and rotate on the spot. Here's a link to a similar concept

It struck me that that would be nice to make with four GM10s mounted on four servos. One servo in each corner, and a wheel on each GM10. But then it struck me, WHY? OK, you would get sideways mobility, but that's the only advantage over the StartHere-design, or tracks. It might be cheaper than meccanum wheels, but the amount of coding to get it rolling glitch free seems staggering.

These are my first thoughts on the subject, what do you think?

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I still think 90 degrees would be enough as you could make your bot double ended. As in there is no 'front' and 'back', so no matter which way it is pointing it would be able to move off and continue it's programming and have sensors at both ends. I suppose it would be trickier to program than having a 'front' and a 'back'.

But I would imagine a sensor head on a servo that rotates 180 degrees and then faces the new 'front' and drives off. Perhaps bumper switches at each end of the bot that when activated would change the current 'front' to the 'back' of the bot and 'back' to the 'front'.

Does this make sense? 

I understand what your saying, and to a small degree the no front idea will apply.

Since I'm building a small scale navigation robot. My plan is to drive sideways/backwards to avoid objects while navigating to my way points. But my concept picture doesn't fully show the present robot design as I've evolved it since then. 

I've now put the battery's under the chassis, and got rid of the servo mounted sensors. These sensors are now fixed mounted (there's no need when I can zero point turn the robot to detect an object) and a couple other changes....

I'll be adding more pictures under this topic, since our conversation is kind of off topic from the original post.  http://letsmakerobots.com/node/6890



If you have forward and Reverse, you would only need 90 degree pivot movement.
are you sure? I thought you needen 180° with forward and reverse to cover all 360°...
Is that if your motors move in forward and reverse then you would only need 90 degrees. If your motors can only be used in forward then you would need to pivot them through 180 degrees.

Mine goes forward/reverse and steers 180 degrees per servo. Its needed in order to allow it to zero point turn without skid steering, or maintain its heading while driving in any direction, or (with a bit of deep programming) it could drive one constant heading while rotating the chassis in circles.

But I chose my design because I wanted to build something a little different.

I'm already building a nav robot with this type of steering/drive, only with 6 wheel drive/steering.

Here's a design picture, and a progress picture.



I saw this idea on Blue Peter (a UK TV prog for children) when my age was measured in single digits and TV came in shades of grey only. Some French bloke had built a car that looked like a soap bubble floating above four small road wheels. The car was shown driving round Paris, and, predictably, easing sideways into very small parking spaces. Is there any other point to cars with wheels that turn other than parking?
and maybe drive-in cinema
i saw the same show except i think the car was only ment to be practical in cities where parking is tight, and high manuverability is needed. The design would seem to be very inefficeient because the amount of matinence required to the the wheels perfectly inline with each other at each turn seems very difficult