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In lugnet.org.ca.rtltoronto, Calum Tsang wrote:
> In lugnet.org.ca.rtltoronto, Wayne Young wrote:
>
> > > Can I ask a stupid question from a non-moving bot owner? Why do you need that
> > > much precision? The light readings are going to be pretty variable, and the
> > > robot targets and obstacles are all moving, so do you really need that much
> > > precision to know the general direction you need to be going in?
> > >
> > > Calum
> >
> > Are you thinking the robot could adjust its direction on the fly? In my limited
> > experience, precision matters when the robot is close to the TO, especially if
> > it can cover a lot of ground in the time it takes for the sensors to come back
> > with a reading (or to average a series of readings in my case).
>
> But if you are "close" to the TO...then your precision usually is higher
> anyways--less movement, less slop?
>
> Here's some made up numbers to illustrate what I don't understand...
>
> If I read at time 0 at 30 degrees, a "contact". By the time I come back to it,
> at time 20, the contact is likely at 60 degrees. Why should it matter that when
> I return at time 20, that I'm pointed to 31, 34 or for that matter 40? The
> target's already at 60 degrees--so far away, any precision is useless?
But suppose at time 20 your robot is pointed at between 10 and 30 degrees due to
the steering defect. Then it has lost even more ground to the moving target.
>
> Obviously the next step is to scan again and try and reacquire the light...every
> time I get scan, I should be getting closer, the final "steps", my turning
> accuracy should be higher if only for the fact I don't "lose" as much as a large
> turn. No need for high accuracy on large scans (eg, 360's)?
>
> Am I smoking crack here?
Your thinking is probably correct if the robot can sample the light reasonably
quickly, allowing it to rescan more and more often (and effectively take smaller
and smaller steps) as it gets closer to the TO.
Suppose the TO is stationary at 12 o'clock (or 0 degrees) relative to the robot.
If the robot can drive straight, then the path to the TO is a straight line.
Let's say the robot has a defect that causes it to steer in the same direction
away from its target every time it starts moving after a rescan. In this case
the path is a series of zigzags. If the sample time is small, then the zigzags
look more like a curve, and the robot will end up at the TO. If the sample time
is really large, then the robot will end up on one side of the TO. The extreme
case is where the sample time is greater than the time it takes the robot to
cover the distance from its starting point to the plane the TO is on. If the
robot was really close to the TO relative to the TO's width, then that's ok, the
block transfer mechanism will probably still be lined up with the hole.
You're probably thinking that it's ridiculous for the sample time to be so
large, and I'm thinking that I need to see if I can make my 'bot read the light
faster so it can make faster decisions while on the move.
But yeah, castors are evil.
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Message has 2 Replies:
 | | Re: Gear lash....
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| (...) One reason the sampling time can be high is a misguided attempt to "smooth" the times. I tried averaging out the last five values in a shift register and found it really slowed the thing down (my samples got really "steppy"). I switched to (...) (19 years ago, 3-Mar-06, to lugnet.org.ca.rtltoronto, FTX)
| | | Re: Gear lash....
|
| (...) No, that made a lot of sense. I get it. I looked at Dave's code--that helped too. (...) I've never used them. I don't really know why one would. I've always used those little 2x2 round pads. I've got a couple worn down by a millimeter which is (...) (19 years ago, 3-Mar-06, to lugnet.org.ca.rtltoronto)
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Message is in Reply To:
| | Re: Gear lash....
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| (...) But if you are "close" to the TO...then your precision usually is higher anyways--less movement, less slop? Here's some made up numbers to illustrate what I don't understand... If I read at time 0 at 30 degrees, a "contact". By the time I come (...) (19 years ago, 2-Mar-06, to lugnet.org.ca.rtltoronto)
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