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?
I believe the manuevering method described is called synchro drive, and there is even a Youtube video of a Lego version, though it has all the turning mechanisms geared together.
It is useful with maintaining facing an object directly while manuevering around it, if the wheels are independantly turnable.
Four wheel drive using electric drive has been done a few times, there are a number of research robots and indeed a number of security/transporter robots which use the arrangment. The syncronisation of the motors is not a major problem electric motor motors are compliant, RPM and Load is easy with these motors.
Years ago Leyland did a 4 wheel drive Mini Moke by just fitting another engine in the back, it was reported to be interesting to drive as they had syncronisation issues and throttle sticking, the Army decided not to proceed with them.
The control laws are complex, for example in Cars the steering is an interesting problem because what you need to do at low speed is different to that at high speed, at low speed the rear wheels may turn to the outside (i.e. turning left, front wheels turn to the left rear to the right) at high speed this is unstable as anyone who have driven a forklift will attest.
i saw the same show except i 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
I saw this idea on Blue 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?
What I’m saying 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 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’.
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…
