pic: it's a Vex Holonomic Drive!

[artdutra04]

Originally Posted by sanddrag

Am I correct in saying it is NOT super easy to push around because the wheels are not all pointing in the same direction? BTW, have any videos of it driving?

It is somewhat easy to push around, as one of the Vex Squarebots from our team was able to push it pretty easily across the linoneum floor. It has a lot more traction on carpeted floor, and it becomes harder to push. Also, the weight really helps get it more traction. When it was only the basic chassis, the wheels would slip on smooth flooring, and it would not get good traction. But this was solved once I built all the manipulators onto the chassis.

EDIT: The robot uses seven motors - four for the drive, and three for the manipulators.

I should a video of it driving around some time soon, as I have been non-stop busy for like the past month. But, if anyone was every wondering how a holonomic drive robot would perform in snow, today's your lucky day!





I took these pictures this morning when a few snow showers brought us another 1 1/2 of snow. It works okay on the sidewalk, but it was sliding all over the place. I was able to tape a little kiddie snow shovel on the front, and I was able to try to shovel some snow. This makes me want to build one of these out of Vex parts next, so I can shovel my driveway from the park bench on my front porch.

[sanddrag]

That just looks like a very bad idea. Especially the wires dangling on the ground. Great fun though, until the magic smoke is released.

[CJO]

Oh, the magic smoke will just make make it seem a bit more like Christmas.

[Tom Bottiglieri]

Originally Posted by artdutra04

This makes me want to build one of these out of Vex parts next, so I can shovel my driveway from the park bench on my front porch.

Why not just retrofit a powered snowblower to drive autonomously?

[CmptrGk]

Originally Posted by Tom Bottiglieri

Why not just retrofit a powered snowblower to drive autonomously?

it might just be me, but i would be scared of an autonomous snowblower. just brings thoughts of it getting messed up and making one of the smaller neighborhood children into "ground beef".

[greencactus3]

Originally Posted by CmptrGk

"ground beef".

ground meat. unless you somehow hit a cow it wont be beef would it?

ew.

but how about a remote controlled one? maybe not autonomous..

[artdutra04]

Originally Posted by artdutra04

I should a video of it driving around some time soon, as I have been non-stop busy for like the past month.

Finally! I had a few free hours free after school today (what a novel idea ), so I decided to assemble the video of my Vex Holonomic Drive robot. All of the video was shot this past weekend at the Savage Soccer Demonstration at the WPI Robotnautica FLL Tournament. Many thanks to WPI for hosting the Savage Soccer competition, which presented a perfect excuse for me to build a holonomic drive. Here's the link:

17.9 Mb - Windows Media Video - http://www.team228.org/index/multime...omic-drive.wmv

Now onward, to another new Vex robot!

[skimoose]

Art, better get working on another white paper for this one.

[Rosiebotboss]

Art,

You have done it again..........The talk from the Vex guys during Rosie team meetings has always drifted to talking about what "Art from Gus" has done this week with his Vex kit. I can hardly wait to see the Vex snowcat. Will it be full size??

[ahecht]

Seeing this thing play Savage Soccer this past Saturday was a real treat. The looks on the FLL kids' faces when this thing started driving were priceless!

[Michael Leicht]

do you have the code for that robot?

i would like to make something like this. i was wondering if i could see your code for it.

[anna~marie]

oh dang that is sexy

[Tim Delles]

Any wanna help me talk Alex into letting me and him build a VEX Kiwi bot?

[artdutra04]

As requested, here is the code from EasyC ver 2.0 that I used for my Vex Holonomic Drive robot. The main drive controls are relative holonomic drive, which is relative to the current position of the robot. So if you push the left joystick to the left, the robot will go to its left. The code works well, and for a lot of people who I let drive this, it was a lot easiar for them to control than the tank drive on my Triple Play / Space Elevator vex robot.

Here's the code:

#include "Main.h"

void main ( void )
{
int LF; // Left Front
int RF; // Right Front
int LR; // Left Rear
int RR; // Right Rear
int leftx;
int lefty;
int rightx;
int spin;
      while ( 1 )
      {
            // Get Data 
            leftx = GetRxInput ( 1 , 4 ) ; // Left Joystick, X Axis
            lefty = GetRxInput ( 1 , 3 ) ; // Left Joystick, Y Axis
            rightx = GetRxInput ( 1 , 1 ) ; // Right Joystick, X Axis
            // Half the input signal (so code does not overflow past 255)
            leftx = leftx / 2 ;
            lefty = lefty / 2 ;
            spin = rightx / 2 ;
            // Drive Code Algorithim
            LF = RR = lefty - leftx + 127 ;
            RF = LR = 255 - lefty - leftx ;
            RR = 255 - RR ; // Reverse Direction of RR motor
            LR = 255 - LR ; // Reverse Direction of LR motor
            // Spin Code Algorithim
            RF = RF - spin + 63 ;
            RR = RR - spin + 63 ;
            LF = LF - spin + 63 ;
            LR = LR - spin + 63 ;
            // Code overflow prevention
            if ( LF < 0 )
            {
                  LF = 0 ;
            }
            else if ( LF > 255 )
            {
                  LF = 255 ;
            }
            if ( RF < 0 )
            {
                  RF = 0 ;
            }
            else if ( RF > 255 )
            {
                  RF = 255 ;
            }
            if ( RR < 0 )
            {
                  RR = 0 ;
            }
            else if ( RR > 255 )
            {
                  RR = 255 ;
            }
            if ( LR < 0 )
            {
                  LR = 0 ;
            }
            else if ( LR > 255 )
            {
                  LR = 255 ;
            }
            // Set Motors
            SetMotor ( 1 , RF ) ;
            SetMotor ( 2 , LF ) ;
            SetMotor ( 3 , LR ) ;
            SetMotor ( 4 , RR ) ;
      }
}

I may resurrect this robot (at least the drive platform) at some point over this summer and utilize the gyro from the FIRST KOP to make the robot a true absolute holonomic drive. But that will be added to my list of designs and ideas to try out, now that I have stock-piled enough Vex stuff in my fallout shelter to last through seven world wars.

I'm dead serious too - I really do have like $2000 worth of Vex stuff.

[Dmkaz]

I love bringing back up old topics =)

Anyways, I tried to import this code into EasyC 1.1 to see how it actually worked. To no avail though. After the code transfers to the controller, the motors seem to randomly spin at different times. I've tweaked this for numerous hours and still no luck. It would be great if someone could help on this issue. Thanks in advance

P.S. I apologize if I posted this in the wrong area. Didn't want to create a new topic for something that has been discussed numerous times.