Sometimes I build robots that attempt to solve real world challenges. Other times, robots are built based on random ideas. This robot is a case of solving a LEGO challenge – specifically, with their Technic tracks/treads #575518. At no fault of theirs, these plastic tracks are slippery on many surfaces. Great for carpets, flat areas, dirt (if you dare) – and great for turning as well. However, when you try to climb with them, they are as slick as ice.
If you Google them, you will find some great ideas on making these treads more ‘sticky’. Some have used 1/2 Technic pins (which fit nicely into the supplied holes), others have used elastics wrapped around them – all great ideas that work fine. I attacked the challenge from a different angle. The result is DG – or Dual Grip (yes, the name is somewhat plain). DG went through numerous revisions as I worked out kinks related to weight, stability, traction, sensors, flex etc. At the bottom I have included some pictures on previous versions of DG – some changes significant, others subtle.
The idea was to have a treaded robot that could navigate varying terrain, turn quickly and of course, climb. Based on my experience with my other robots using the same tracks (eg UNV and DynaTrax), I found that they were not very good when it came to inclines. I figured that the LEGO rubber wheels have great traction on most surfaces, so why not slap a set of them along with the treads. However, this posed another challenge. I did not want both wheel systems in contact with the ground at all times as this would make turning tougher and be redundant.
What better way to test a colour sensor then to create a brick sorting robot! After getting my hands on a HiTechnic colour sensor, I first took a stab at creating a robot that could navigate a room and detect colour. There was only one problem, it could not really do what I was hoping for. I was nieve in thinking that I could build this robot and it could detect colours from a distance. After reading the fine print on the provided documentation, I quickly realized that the colour sensor is only capable of reading colours at very close range (~ 1 cm). My bad. Of course, you could still build a robot that uses the ultrasonic or other sensor to get it close to objects, then read the colour… but that’s for another time.
BrickSorter uses this colour sensor to detect the colour of bricks and sort them into a variety of cups. The program is quite simple, gravity and studless beams allow for each brick to slide down the track on its own. when a brick is next, the colour sensor takes a reading (more on this later), the sort motor turns the sort rails to the correct cup, the sort rail motor changes its angle depending if the cup is close or far and finally the kicker motor kicks the brick in motion.
After a lot of fooling around with the cup placement (which seemed to be the hardest part of this project!), I managed to get the sorting pretty much bang on. Of course, the video shows some goofs, but that is mostly due to the small sized cups (its all I had!)… Anyway, I found the sensor to be accurate most of the time, but ambient light still influenced the readings at times and caused for the odd random missorting of a brick. I had to shoot the video about 10 times to get cup placement and sorting goofs worked out.
Your first question is probably “what does UNV stand for?”. Well, its nothing special – I simply could not come up with a name for it, so what better way to tag it then simply unnamed vehicle. After receiving a bunch of the new tread links, I wanted to create something grand with them. Scouting the web, I came across these multi-purpose robots (see below) that can be outfitted for police / bomb squad use, or for scientific work. Thought they looked pretty cool, so they were the inspiration. UNV was sitting around for months before I finally got around to taking pictures and a video of it. Read on for details…
Sometimes my robot building ideas are spurred by nothing more than wanting to make use of one or more cool items that I get from time-to-time. In this case it’s two – tread tracks that can be had if you own the Technic Snowmobile (8272) and a TechnoStuff Tilt/Accel Sensor. I was fortunate to have received a huge bag (a few hundred segments along with wheels) of the new tread tracks a while back and begun playing with them to see how they compare to their smaller black Technic counterparts. In a nutshell, I like these ones better as they are larger (more suited to the size of robots and Technic creations I build) and stronger – they dont come apart as easy. They also have pin holes in them to boot, so the sky is the limit for making large tracked vehicles.
Update: DominoBotNXT has been enhanced. See DominoBot2.
For those who do not know about the Lego Mindstorms Developer Program (MDP), back in January of 2006 Lego was seeking assistance from the Lego community on their next generation Mindstorms product (NXT). Approx 9600 people applied to become one of the 100 MDP’s. In late February, I received an invitation to participate and of course jump at the opportunity. For a few months, the group of us were under an NDA (Non-Disclosure Agreement) where we could not talk, show or discuss anything about what we had been working on in the MPD. Now that May 1 has passed, we can now open to discuss some of what we have been up to.
We all had an opportunity to participate in different areas of the testing/development process areas from software to Bluetooth to building robots. Initially, I wanted to get involved in more than one area, but time was limited, so I decided to focus on building only. I wanted to try and re-build my original DominoBot robot to see if I could make a better, more efficient version of it. I also wanted to test the new motors’ built-in rotation sensors – as I needed this functionality.
Pete @ Techno-Stuff has just sent me another new sensor from Techno-Stuff. This time it’s a Accelleration / Tilt sensor. Instead of going into great detail on how it works, I will quote from his site:
“ The Accel Sensor lets your robot measure it’s acceleration. The sensor can also be used to measure tilt. This is a two channel device that lets you measure acceleration or tilt along two perpendicular axis. Acceleration is a change in speed. When you push the gas pedal of a car, and the car speeds up, this is acceleration. The Dual Acceleration/Tilt Sensor (Accel) measures acceleration by it’s effect on a small mass. The sensing mass is also affected by gravity. Because of this, the sensor can be used to measure gravity. Gravity is constant, and points straight down. Since the Accel sensor can measure gravity, you can use it as a tilt sensor. The sensor is most sensitive to tilt when it is mounted so the sensing channels are perpendicular to gravity. (the electrical connector is horizontal) When mounted this way, the light sensor value will be 50, indicating zero acceleration. The value will increase or decrease depending on the direction of tilt. “
So, to put the sensor to the test, I thought what better way to do this than to use my NXT kit.