| |
In lugnet.edu, Scott Arthur writes:
> I've thought about using two motors for steering.
>
> Do they turn at exectly the same rate?
Generally not. I've built robotic platforms that use a pair of motors to
drive the wheels so that the robot can move "straight" or turn in place. I've
found that the motors typically have large variations in speed that make the
robot veer to one side or the other when it is trying to go straight. I've
done experiments with angle sensors to try to detect navigation errors and
modulate the motor speeds accordingly, but haven't had much success so far.
The same motor also seems to run faster in one direction than the other. I
think I've heard that this is due to the internal gearing in the motor, but I
never quite wrapped my brain around how that could be... Anyway, most two-
motor-drive platform designs that I've seen have the motors oriented 180
degrees apart from one another, so in either forward or backward motion, the
motors will be turning in opposite directions, and the gearing problem will
drag you off course even with perfectly-matched motors.
Even so, I've been thinking that somebody needs to design an RCX dynamometer
and then we need to have a "motor matching" get-together. Everybody could
bring all their motors, we would spec them out, and try to send everyone home
with matching motors. (This idea is stolen from a foundation that helps
people with abnormal foot sizes exchange leftover shoes so that they don't
need to buy twice as many pairs as the rest of us.)
The RIS 1.0 CD-ROM has a movie of a simple robot that you can build. When
they show it running "straight" it also turns heavily to one side. I was kind
of surprised that they didn't find a pair of motors that were balanced better
for their display model! (They probably have a few spares lying around there,
one would imagine.) But again, if the internal gearing is the problem,
matched motors won't really help anyway.
|
|
Message has 3 Replies:
 | | Re: lego Technic "class"
|
| From: "Chris Phillips" <chris.phillips@comp...oards.com> (...) I've (...) the (...) I've (...) far. The adder/subtractor is an all mechincal design which handles this flaw. Take a look at (URL) I'm sure that others will chime in with their designs (...) (25 years ago, 29-Oct-99, to lugnet.robotics)
| | | Re: lego Technic "class"
|
| (...) *snip* As a somewhat Bizzare experiment, I have run a LEGO motor from the battery box controller as supplied with motor set 8735. The motor is placed next to a Pick-up on an electric guitar plugged into an electronic tuner. With the motor (...) (25 years ago, 29-Oct-99, to lugnet.robotics)
|
Message is in Reply To:
39 Messages in This Thread:
 
 
 
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
This Message and its Replies on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
