‚Explore Science‘ is a competition in Mannheim, Germany where students can participate and try to solve science and engineering tasks. The competition is organized by the Klaus-Tschira-Stiftung, a foundation from Klaus Tschira, one of the founders from SAP.
One of the tasks this year was collecting as many of 100 Ping-Pong-balls (each ball equals a point) as possible from a square wooden field with a side length of 1m and a 5cm high border. The robot had to fit completely on a DIN A3 paper, could not extend and had no height limitations. You can radio control the robot, however autonomously collected balls count twice for your score. Continue reading “Participating at ‘Explore Science’”
Before building a soccer bot, we wanted to calculate whether our motors are actually strong enough to slide the fuel-cubes for six metres.
First we did an experiment to find out the friction coefficient of the grass and the cube. For this we laid the grass on a tilted ramp. Then we slid down the cube. We then tested for the maximal angle at which the fuel-cube would stop sliding.
Up until now we have been trying to build a extendable ramp with polycord for lifting the fuel cubes to the goals. However in the mean time new ideas have sprung up, all of which we discussed extensively.
The ramp is the idea that we have been building so far. But instead of making the whole thing extensible, we have thought of accelerating the cubes at the end of the first ramp fast enough to shoot them into the goals. We would still use an extension, but it will only be a guide for the cubes.
We noticed that our robot tended to slip and didn’t have a good grip on the ground. Also despite using traction wheels at the front and the back our agility was quite good. That is why we decided to use only traction wheels, and also drive to make sure that at least one rotating wheel has contact with the floor. Continue reading “Improving the Chassis: Using only Traction Wheels”
Today we improved our front for the fuel cube collector. Previously, we had just mounted wheels on two motors on the frame directly. However the problem was pulling in cubes diagonally. We have thought about an arm tensioned by rubber bands/medical tubing.
Today we attached the pulley-belt mechanism to the chassis.
The slope is 60 degrees. We will probably need less in the finished construction. However proving that it will work with this slope assures us that it will work for less steep ones as well.
For testing purposes the motor was attached directly to the pulley-wheel.
The distance between the pulley-wheels is 19.5cm. The pitch between the big wheels in the front is 23.5cm.
Since this is a proof of concept it is very wobbly and very ugly. The extrusions are connected together without much thought and also without cutting them. However after testing we are able to decide, whether to build it anew, a pursue a different idea.
Testing it we found out, that collecting the cubes when they are inserted parallel to the robot works very well and reliably. However trying to collect them when they are diagonal to the robot jams our collector. One solution might be to use a spring-like mechanism with the medical tubing for the front wheels after all.
Also we will need to make sure that the whole slope can be tilted to adjust the height. Additionally we also need to attach the extension of the pulley belt for a proof of concept. The front wheels need to be improved as well.
After testing these things we can move to design and stability.
First we built a poly-cord pulley belt, to transport the cubes.
We tested this out, by rotating the wheels by hand, thus moving the poly-cord. The result: It works quite alright as soon as the cubes are inside. However the mechanism is unable to pull the cubes in.
That is why we thought about having wheels in the front pulling the cubes in and the pulley belt behind to transport the cubes inside the robot.
Therefore the next step was to attach wheels in the front of the robot.
We first thought about a mechanism that uses surgical tubing to press the wheels together, and only make them move apart when there is a cube pressing in. This idea is supposed to guarantee that there is always contact between the wheels and the cubes.
We built this by attaching arms to the front. The arms were held back with medical tubing, but could expand outwards when there was cube pressing against them.
However we soon noticed, that it might actually be overly complex. Since our goal is to build everything as simple as possible (it makes it more reliable), we decided to try the obvious and most simple thing. Just attaching the wheels stiffly.
For testing purposes, we just drove the wheels directly with motors attached beneath them.
We tested this out and it worked marvellously. The cubes are pulled in by just nudging them slightly into the wheels. However once they are inside, they aren’t really aligned. We’ll need to see whether this will be a problem in our pulley belt mechanism later.
Also note that everything is a proof of concept. We will after building most likely disassemble everything and reassemble it cleanly later.