Let's Make Robots!

JORGEroamer Tri-Wheel Robot

Roams using touch sensors

JORGEroamer is a modified A-Robot from Arrick Robotics. A sturdy and practical platform, this tri-wheel robot affords a unique chassis and steering system. The front wheel motor drive runs forward and reverse while steering is accommodated by the two rear wheels via a center mounted servo. The result is an efficient platform that is easy on the batteries.  These vids show JORGEroamer loaded with fairly simple wandering code using whiskers and later revised to employe a bump plate. This robot is truly a joy to work with. To date, I've modified JORGEroamer with a second level, touch sensor system and, of course, custom paint job. The first vid shows his early life as a roamer. His last vid shows that JORGEroamer has finally figured out how to find his way to his bedroom. I've got plans for this little bot just as soon as I can find more time to play. Thanks to Roger Arrick for offering such a cool kit.

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Yup, this one is good. First one on LMR as well, I think. I have seen a few 3-wheelers here (I am "working" on one) but they all steer by way of the third wheel. IgnobleGnome (man, I think it was him) is working on one, trying to balance 2 powered wheels and a servo-steered nosewheel. At any rate, I have never seen 3rd wheel-powered-and-fixed with front-wheels-steering, this is a great setup. I am a airplane guy as well so I gotta love those big dubro tires and all your steering linkages. Just great.

You need to see this one through. --Get a sonar sensor on it, etc.

Fantastic bot.

The A-Robot platform is great to work with...it's drive system makes it fairly easy to program.  You don't see many of these around, however.  Most tri wheel platforms, as you suggest, are designed to steer at the forward wheel with a bi directional rear wheel config.  Roger Arrick got this one right, I think.  I do plan to include some nav sensors beyond tactile.  Thanks for the comment.

CtC is referring to Why Tri, who is coming along nicely. As he points out, this is very different from what you have here.

The ackerman style steering combined with a single rear drivewheel on JORGEroamer is a nice approach. You don't have to mess with differential speeds, like you would if you had two drive wheels in back.

How have you found steering control with your set up? Do you typically steer to specific angles or do you just turn full-left and full-right most of the time?

I have another project with two front wheel steering (Yard Gnome). He's no where near done, but I'm interested in understanding the programming required for this type of steering. Even though Yard Gnome has two rear drive wheels with differential gearing, the turning should be fairly similar to what you have.

I checked out Why Tri and Yard Gnome.  Is Yard Gnome bi directional drive or is it similar to Jorge?  I'm just sayin'...this tri wheel stuff is trickier than it looks.  This is why I prefer the Ackerman Drive Geometry.  I truly think Ackerman is under utlilized in robotics...for whatever reason.  Maybe it's because linkages just aren't as sexy as direct drive platforms.  Who knows.  For me, it's simply because I don't claim to be any sort of a programmer.  I'm a tinkerer.  In any case, this is why I was attracted to the Arrick Robotic's A-Robot platform.

The steering, to begin with, was simply pulsing the servo left/right/center.  In tandem, the drive wheel runs forward/stop/reverse.  Once the steering geometry is applied to the chassis, it's easy to see where the adjustments in code are needed.  I definately want to include at least one more nav sensor in addition to touch. 

ANYTHING with ANY kind of linkage, belt, chain or lever is WAY more sexy than direct-drive! I mean, c'mon --everyone and their brother has a "regular" differential-drive, wheel-on-each-side, robot. I wanna see pivots! I wanna see pushrods! I wanna see dubro parts!

 

I agree totally.  All that mechanical assembly stuff running off the original motor.  I mean from the motor to the gears to linkages to the usual useless thingy that works and looks cool with bright lights and stuff.  I totally concur.  But then why is the whole linkage thing seemingly limited to remotes like aircraft, cars, boats, etc.  Seems hobbyist robotics developers are missing some efficiency here.

Yard Gnome is based on a drive motor and rear axle of a mobility scooter.  There's a differential gearbox built into the shaft. One motor spins both rear wheels, but they allow for turning at different rates like a car. All the steering is done with linkages at the front two wheels.

Something I'm trying with Why Tri is smoother steering that responds with sharper or more gentle steering depending on what is needed. The ultimate would be to steer at any angle, but right now he just has 90 degree, sharp, gentle and straight positions defined. It is still an improvement over left/center/right steering.

That sounds cool.  Nice platform too.  You won't likely have issues with your motors wearing out for sure.