EDR

VEX Worlds 2017 – Robotics Competition

Posted on by burf2000

Sorry for the late post about VEX Worlds, I thought I would have more time after worlds to catch up with stuff, sadly (well not really), the kids have been mega active.  My eldest son played his first football tournament, had a holiday, lots of family stuff!

So, VEX Worlds, what an amazing experience, I went along for the VEX EDR side of the competition (this year it was split EDR / IQ) as I was showing off the EDR Tank.  Sadly I had to leave the US early as my son, Max was ill.  Still a very cool experience!

So, the EDR tank, well it performed really really well in remote control mode.  I mean the thing was fairly slow but must have covered MILES!  The batteries never died on me, nor did any motors!  I did kill a few Omniwheels, however, that’s to be expected.   Even though I left early, the EDR tank did not and so others drove it around.  I have not received it back yet to see how bad it is now, but I am sure it will be fine.

The autonomous side was a bit of a failure, to be honest, and looking back I had set up myself to fail and I will explain why.  The autonomous side was using ROS (Robotic operating system) which is an industry standard.  I was using a Neato Lidar system which is awesome however it only had a range of 5 meters and SLAM (simultaneous localization and mapping) to work out where I was, and where I needed to go via building up a map.  SLAM works by detecting features of the surrounding area to work out where it is.  When you’re in a hall that’s hundreds of meters wide with very little features, a sensor with a range of 5 meters is practically useless.  In the end, I just showed kids how it worked on my laptop using RVIZ.  If I had to do this properly I would need to invest in a proper LIDAR system with a much greater range.  Another aspect which makes this very hard is all the people moving around, how can SLAM pick up features if they are constantly moving!

Overall, the EDR tank was hugely popular, I gave tons of fist bumps, high fives, etc, people just thought it was cool, just a little slow.

Next year, if I did a vehicle again, I would have to make it a lot faster and forget about advance sensors etc!

Here are some videos of VEX World and the EDR TANK:

The VEX EDR Tank

Posted on by burf2000

Over the last few month’s, I have been building a vehicle out of VEX EDR with the aim of it to self-drive. This is my first big project with VEX EDR, I usually build large stuff out of LEGO Mindstorms or VEXIQ. My view was that VEX EDR would be easier as it is a) made out of metal as opposed to plastic, and b) more powerful. I thought it would take me a week to make the vehicle, and the rest of the time would be on software. I had to also learn ROS (Robotic Operating System).

It actually turned out more challenging than I expected. Due to my lack of experience with EDR, I just assumed metal would just be stronger, and the motors would just work. However the first version of the Tank collapsed under my weight, and it took around 10 versions to get it to move me (95kg) without the motors shutting down after 5 seconds. Unlike LEGO and VEXIQ, EDR motors had a protection circuit in (PTC) which shut down the motor if it gets too hot or draws too much power. This is, of course, a good feature to protect the motor, however, it made my project very difficult.

I went from 8 motors, direct drive to 14 motors geared down to 2.44. The 8 motors could move me at a rapid speed but would just shut down after a few second.

Here is the progress of how it went

Current state

So I managed to get the Tank to a point where it worked, it was not as fast as I hoped however it seems reliable.  Next is the software.  ROS is a big subject to learn, there are lot of books on it and it is not the easiest thing to learn.  I have actually made some good progress on this thanks to the community.  Stay tuned to my next post about ROS.