Vex Robotics Blog

Vex Clean Sweep Animation

2009-08-25T13:39:00.005-04:00

I have just been looking around the VEX Robotics site when I found the newly added VRC 2009-2010 animation. It looks really good, and does an excellent job of explaining of how clean sweep works. Great job by Cody Smith for putting it together.

Here is the LINK to the rest of the vex competition page, which also has the video in High Res and mobile formats.

Scoring Methods

2009-08-23T18:12:00.016-04:00

Recently I have been thinking about the vex clean sweep wold championships. In particular I was thinking of how I could help get my team there. From what I saw last year careful planning and good strategizing was a key aspect of the team so naturally this year was going to be no exception. One of the most basic things to consider is going to be our scoring method.

(you can click on the diagram for a higher resolution version)

As you can see clean sweep offers players a lot more choice when it comes to choosing you scoring method. If you played last years game Elevation, there really was little choice on how you went about scoring. As different as all the robot designs were, most every team had to be able to score into the triangular goals in order to be at all effective. In clean sweep there is only on objective, that is get the balls off your side and onto the opposing alliance. However, how you go about that can vary. to better understand the different scoring method options here is a chart from the VEX competition section about clean sweep.

VEX Robotics Competition - VEX Clean Sweep Scoring

VEX Clean Sweep Action	VEX Clean Sweep Points
Each Small Ball Scored	1 point
Each Small Ball Locked Up	3 points
Each Medium Ball Scored	5 points
Each Large Ball Scored	10 points
Autonomous Period Bonus	5 points

Now most teams are not going to consider focusing on the small balls. Here is why:

1 small ball = 1 point

There are only 25 balls available at the start of the match some if the other teams dont dump any of their small balls then you can only score 25 points.

Only 5 of the medium balls would equal 25 points.

Even If you somehow managed to moved all the 42 small balls on the other side of the field you would get the score equivalent of just 9 medium balls, and there are 19 on them.

Now a little math and logic would stop a team from building a robot that can only manipulate the small balls. But how about 'locking' small balls. Since each small ball can yield 3 points if scored into the triangular goals. Lets test this strategy.

17 balls available right away (not counting the 8 balls that are in the wall slots)

If all 17 are scored then you would get 51 points and if you manage to get the extra 8 you would get a total of 75 points. Not bad, since we are not counting the balls that start on the opposing alliance's field and have the opportunity to end up on yours.

Right of the bat this seems like a good idea since 51 points scored would mean a 102 points difference in total scores. I thought is was a good idea but then it hit me. How many balls can fit into the goal? All these little calculations neglect to consider the possibility that the triangular goals can fill up before you score your 25 small balls. So how big are these goals.

According to the Vex field specs that can be found on their clean sweep page, the triangular goals are made up of 3 boards each 8'x18'.

If the small balls are 4 inches in diameter 18/4 would give us 4 small balls in the goal fully and I assume at least 1 more that can be half way in. For a total of 5 balls in one goal, and 10 in total.

Now this idea doesn't seem so good. If 10 small balls can be locked then only 30 points can be earned. Leaving you robot to score 1 point at a time.

I think it's fair to assume that focusing on the small balls will be a mistake. I for one do not see anyway you can win (against a robot that scores medium balls) with a "small-ball-bot". It would be nice to be able to lock balls as a secondary method of scoring but the meduim balls will be an inevitable part of the 2009-2010 vex clean sweep games.

My next blog post will be about the pick up systems and what some of the obvious choices are as well as their "ups" and "downs"

Size isn't everything

2009-08-16T22:37:00.005-04:00

As i said before i was looking at the scrimmage competitions that took place in New Zealand earlier this august. There were a few very good robots there and also a few pretty shabby ones. However i was surprised to see that a robot i though would win didn't. Team 2911a in my opinion had the best robot or at least the best idea. As you will see in the video below vex team 2911a had a very effective "shovel/scoop" pickup system and an even more effective bucket. However they experienced what i think was a little bit of greed or just a faulty strategy. Rather than picking up 2 or 4 balls like most team they had the capacity to pick up 6 or 8 at a time, and they did. There is nothing wrong with being able to pick up huge amounts of vex competition balls but you don't win a competition by keeping them. So for a better understanding of what i am talking about here is the VEX Clean Sweep 2009-08-09 Semi final match 1:

You could definitely hear some team members or bystanders screaming for the robot to dump, however the robot seemed to be a bit clumsy at moving around and all the balls that the robot picked up made the whole lift-and-drop-system very slow. I think that the robotics team at Avondale college are on top of that problem at will lighten their whole bucket as well as their scoop which also seemed to be functioning rather slow.

On the other hand team 2901 from Rangitoto college took a slightly different approach to the bucket and scoop idea. Rather than having a giant bucket that took the whole match to fill up, team 2901 created a light system which carried a few balls but picked them up and dumped them really fast. This won them the vex robotics competition but in the future i am really interested to see what type of robot would claim the first spot in the Vex World championship.Who knows, maybe the winning team will use a completely different approach.

If you want to see all the videos from the New Zealand scrimmage then RoboticsAtRangitoto has done everyone a huge favor for posting them on Youtube just remember to click on the column "More from RoboticsAtRangitoto" and you will see all the Vex competition videos.

Here is the LINK

Just a heads up for my later blog post I will be talking about what choices teams will have when it comes to scoring in the clean sweep games.

Team 478 Mustang Robotics in VEX Robotics Competition

2009-08-15T17:58:00.010-04:00

I have been browsing Youtube for some Clean sweep videos to show you guys and to comment on good and bad aspects of their designs but all that is coming in a later blog post. However I stumbled on two videos that I nearly forgotten about and after watching them all the memories of last years game of Elevation rushed back to me. So I decided to post them here so that you can all see what we did last year and how good our robot actually was.

The first one is a promo video that a retired member of the team made for us before the World championships.

The second is a Drivers challenge video which was also made not too long before the VEX robotics World Championships in Dallas.

Vex Robotics Drive system for Clean sweep

2009-08-15T14:22:00.001-04:00

I have been reading some posts on the VEX forums about people wondering if a Holonomic drivetrain system is better for this years game, Clean Sweep. For those of you who are new to this, a Holonomic drive system is a system that allows the vex robots and any robots to travel in any direct without having to turn in one direction or another.
You can think of a normal drive system as a skate board and a Holonomic one as a snowboard. A snowboarder can twist his or her snowboard sideways and still continue to travel downhill while a skateboard can only travel in a (more or less) straight line. This presents an advantage especially to this years game as you would want to be able to move quickly around your side of the field without having to waist time turning around. The simplest way to build a Holonomic drive system is by using Omni-wheels and positioning them at 45 degree angles at the corners of the chassis. There is an excellent video on Youtube which shows a simple Holonomic drive system.

As you seen in the video there is a definite advantage to having your Vex robot using such a system but what about traction. In the last year's game such a system would not have been a very smart idea. Since last year, the game evolved an undivided field which meant definite contact with the opposing alliance. A robot with a Holonomic drive system would have had very little luck in being able to defend itself against even some of the less "beefy" robots. This year the field is divided and its highly unlikely that you will have to be able to push your self out a jam.

So far there doesn't seem to be any reason NOT to make a Holonomic drive system but what about space? Well by space i mean space for your very creative pick up system. If you noticed in the video above there doesn't seem to be any opening in the front, or in the sides of the chassis. Now that wasn't a problem for the man who build it because he was building simply building a Holonomic drive train. However for someone who has created a pick up system that picks up from the floor this can be a problem. unfortunately there is no quick fix for this, hopefully you understand the way a Holonomic drive works and if you do then you can experiment with different configurations of the chassis and the Omni-wheels.

If you aren't 100% on how exactly the Holonomic system works then there is an AMAZING video by one Cody Smith on the VEX Forums. The video is nearly an hour and it goes over how to program your Holonomic system, but the first 5 -10 minutes or so explain the basics of the system very well. I STRONGLY RECOMMEND IT

Click HERE for the video
Click HERE for the Thread that contains the video and some support files
Video posted on VEX Forums by: Smartkid