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In lugnet.technic, Tom Beattie wrote:
> Fantastic Miguel!
Hi Tom - thank you very much!
> I have been working a similar Rover concept for the last few months,
It took me about 3 months to complete this one. I ended up pulling an
all-nighter to finish the Ldraw file in time for the contest!
> although I
> must confess, that I have focused on the brute strength approach
I orginally wanted to enter at least 2 rovers in the contest. I started working
on a regular wheeled skid-steerer. However, I soon found out that countering the
lateral friction on the wheels while the vehicle turns is no easy matter if the
setup includes 4 wheels placed at the end of relatively thin arms that held then
quite distant from each other. That is when I switched to the differential idea,
that I already had in mind. One objective was to build something that did not
look like a tank (IOW, combined sheer body bulk with multiple wheels placed
closely together). Using the "differential steering" allows for that.
> - with motors
> located at each wheel. My Rover is RCX controlled and has four wheel steering
> just like yours – although at last count it had 6 motors and a rotation >sensor.
NASA's MER (which should be launching any minute now) uses 6 wheels, with one
motor per wheel and a similar steering configuration.
Unfortunately, it is really hard to get images of this feature - here is a
hi-res image of the rover in which you can see part of the mechanism (notice how
thin are the arms holding the wheels)
http://athena.cornell.edu/images/wallpaper/MER_800_600.jpg
Joe Nagata has a new MOC which seems to have similar capabilities (but is it a
skid-steerer?) - it uses 4 wheels, 3 motors and an RCX - check it out
http://member.nifty.ne.jp/mindstorms/gallery/k081e.html
>
> I must say that your approach to driving each wheel assembly is quite innovate.
> It reminds me of those little wind-up toys that move around the floor , and when
> faced with an obstruction, automatically change direction – Quite a fascinating
> approach.
I've only learned about an antartic exploration vehicle called Nomad *after* I
made Differyimento. Take a look at this - and try not to fall off your chair!
http://www.frc.ri.cmu.edu/projects/meteorobot/Nomad/transforming_chassis.html
>
> I wonder if a similar behavior could be modeled in the RCX using the Voltage
> monitoring functionality of NQC (when a driving motor is stalled it will attempt
> to draw more power from the RCX batteries resulting in a change in voltage) to
> trigger such a change in steering configuration. I will have to investigate!
Let me know how it goes. I definitely want to do a second version with a Scout.
I could simply attach a scout (and at least 1 touch sensor to monitor the
correct alignment of the wheels when centered) to the existing model. However,
one very cool feature of Differtimento is that its weight is placed relatively
low, specally if we consider that it has quite a bit of ground clearance. It can
climb fairly steep hills without turning over, and can go over obstacles roughly
half the height of its wheels. Making a completely new version around the Scout
will hopefully allow me to keep these features and further enhance them
(suspension, computer-asssited steering, etc.) But I am very intrigued by the
functionality of the differential, which in my opinion is the most important
feature of the model.
>
> My site should be ready in a week or so, so you can check out my version of a
> Mars Rover – It too is modeled in LDraw as well as an ABS version – It would be
> interesting to compare sizes, wheel base etc…
Did you enter it in the Lego mars rover contest?
> I look forward to further discussion.
Me too!
Cheers
PS: The video image has been slightly accelerated - Differtimento is too slow
for my taste. Maybe something to correct in the next version too.
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Message has 1 Reply:
 | | Re: MOC Differtimento
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| Hello Miguel, I downloaded your DAT file of Differtimento and it seems to use some parts I don't have. Primarily the Vision Command camera and the newer type of wheels. Can you point me in the right direction to where I might be able to down load (...) (21 years ago, 11-Jun-03, to lugnet.technic, lugnet.robotics, lugnet.cad)
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Message is in Reply To:
| | Re: MOC Differtimento
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| (...) Fantastic Miguel! I have been working a similar Rover concept for the last few months, although I must confess, that I have focused on the brute strength approach - with motors located at each wheel. My Rover is RCX controlled and has four (...) (21 years ago, 10-Jun-03, to lugnet.technic, lugnet.technic, lugnet.cad)
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