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Unread 19-03-2010, 09:54
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Re: fine control of robot with mecanum wheels

Quote:
Originally Posted by Ether View Post
...with the lack of fine control of robot movements...

~
Team 241 has 8" mecanum, direct drive toughboxes,
voltage control CAN interface

----
We are considering adding and tuning a speed control based on encoders that are already mounted.
----

There have been many factors that we have found seem to affect "the lack of fine control of robot movements..."

+ consistent CIM free run speed - (some CIMs are outliers)
+ consistent gearbox efficiency -
+ consistency of mecanum roller turn resistance- keeping these even have been a constant maintenance task for our mechanics
+ the designed lack of roundness in the 8" mecanums - at very low power, this non-linearity is noticeable.
+ weight distribution - get 4 scales one for each wheel.
+ suspension to keep all wheels firmly on the ground (we added this early based on academic research- so we really don't know how important it is to this game/surface... Are some teams with mecanums but without suspensions satisfied with the handling for the Breakaway arena?)

and probably most important-
+++ giving the driver enough practice time to truly have a chance of learning to predict the behavior of the robot based on the commands sent to it.
we locked in on using a single driver almost exclusively due to the lack of enough practice time available.


Our original optimistic plans were to have speed control (not voltage control) completed at least two week before the robot had to ship so the drivers would have substantial time to learn the machine.

We have portions of a second bot but we did not get to a cloned drivetrain (no mecanums, only 2 CIMs on it).

The teams with fields to practice on and have cloned second bots to practice with are strongly advantaged both in getting the control right and more importantly, in training the drivers to play the game well and making the most of the control that they have.

I am bit amazed on how well some drivers have done with so little driving practice especially with new mecanum drive systems.

IMO, the most important control system to tune is the one between the drivers ears...
 


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