Subject:
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proud of myself (+ some questions)
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Newsgroups:
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lugnet.robotics, lugnet.build
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Date:
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Fri, 17 Sep 1999 03:39:27 GMT
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Reply-To:
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mattdm@!AvoidSpam!mattdm.org
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Viewed:
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21 times
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So, I got sent home early from work today, due to the hurricane and all.
Good thing because 1) I'd left our windows open 2) Kenmore Square is
apparently flooded and it woulda been hard to get home later and, most
importantly, 3) I made a cool lego thing I'm happy with.
I've built quite a few Mindstorms projects, but they've all been either
stationary, or based on a simple tank-tread design. And usually, I they
feature a bulldozer-like "blade" in front, as a touch sensor.
Today, having a whole afternoon in front of me, I thought I'd try something
different. Instead of a bulldozer, I now have a small automobile-robot. It
uses one motor (through a differential) as a rear-wheel drive, and the other
for front-wheel steering. And rather than having a bumper, I used a rotation
sensor to provide "heartbeat" feedback. The drive motor is hooked to the
white slip-clutch gear, and the rotation sensor is after that. If the car
gets stuck against something, the slip-clutch slips and the heartbeat stops,
so the car knows to turn around.
Unfortunately, I don't have another rotation sensor, or another slip-clutch,
or a micromotor, so the steering part is less than my ideal, but still
worked out nicely. I used a touch sensor to determine the middle point, and
use a rack-and-pinion design, with the motor connected to a rubber band
(see, here's where the second slip-clutch would have been nicer) which slips
when the extremes are reached.
The whole thing works pretty nicely, and runs around my floor wonderfully --
it's much better at not getting stuck or confused, since it isn't limited by
a front-only bumper.
And, I've got a third output port and a third input, plus the port used for
the steering-centering could be reused for some function that wouldn't be
needed while turning.
I'll post pictures and code (NQC) once I get it a bit more polished.
So, questions:
Wow, I can sure tell that there's only one motor. While it works great on
wood floors, it barely moves on carpet. Is there a good way to add a second
motor? I hesitate to just link them to gears in serial -- it seems like
there must be a better way. What is it? :)
Ideally, it'd be cool to have the two motors at different gears, and
auto-switch between the two as needed. The software part of this is easy --
any suggestions for the physical part?
Also, is there any good source for white slip-clutch gears other than the
8735 motor set? I already have all of the (big-sized) motors I really need,
so I hesitate to buy another just for that.
--
Matthew Miller ---> mattdm@mattdm.org
Quotes 'R' Us ---> http://quotes-r-us.org/
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Message has 8 Replies:
 | | Re: proud of myself (+ some questions)
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| (...) If you have a fiber optic component from the Extreme Creatures or Space Shuttle sets, you could use that for the heartbeat instead, freeing up the rotation sensor for steering. It's ideal in this role because you don't need to know direction (...) (25 years ago, 17-Sep-99, to lugnet.robotics)
| | | Re: proud of myself (+ some questions)
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| (...) A differential can be used to add two motors together. One motor on each axle, then let the "shell" of the differential power the drivetrain (which of course has its own differential). (...) If you're adding them together with a differential, (...) (25 years ago, 17-Sep-99, to lugnet.robotics, lugnet.build)
| | | Re: proud of myself (+ some questions)
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| (...) The two motors drivetrain (coupled through a differential) that others suggested is a very practical and effective solution. If you want to try a "different" thing you can set up a vehicle with two or more gears. Less effective but fun to set (...) (25 years ago, 17-Sep-99, to lugnet.robotics, lugnet.build)
| | | Re: proud of myself (+ some questions)
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| (...) If you can accept having "discrete" steering positions, then you can use a touch sensor to mimic a rotation sensor. A line of 1-stud cylindrical elements moving past a touch sensor will give "0" when the sensor is exactly between two elements (...) (25 years ago, 17-Sep-99, to lugnet.robotics)
| | | Re: proud of myself (+ some questions)
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| (...) second (...) As part of a different project, I wrote a snippet of code that would maintain a specific speed regardless of the surface. It's based on a rotation sensor target vs. time. If it's going too slow, the motor speed is bumped up by (...) (25 years ago, 17-Sep-99, to lugnet.robotics, lugnet.build)
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