Participating at ‘Explore Science’

‚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’”

Calculating the Feasibility of the Soccer-Bot

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.

Sketch of experiment for calculating the friction

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Collecting Ideas for the Fuel Cubes

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

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.

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Prototyping the Back of the Fuel Cube Collector: Conveyor

After having proved that our mechanism for the fuel cube collector using the pulleys works, we decided to build a better designed and stronger prototype.

The general idea for the construction sketched out in the picture below.

Sketch of the frame

For this we first had to plan out the construction. We wanted to drive one conveyor belt with one motors. For this we planned on connecting both sides with a chain underneath that runs underneath the cubes. The pulleys are mounted underneath the topmost extrusion to make building a joint easier. Continue reading “Prototyping the Back of the Fuel Cube Collector: Conveyor”

Testing Servo Joints for the Back of the Fuel Cube Collector

The ramps on which the fuel cubes will be transported to the goals needs to be longer than 50cm, so we will need something capable of unfolding.

For this we tested out several ways to build a joint with a servo. Some of them are more reliable than others, but sometimes require more space and material.

The first idea is built using the servo shaft adapter. The servo is simply mounted onto one extrusions and the other is connected by a hex-shaft and hex-pillow.

This is the most simple joint one can build, and it doesn’t require much space. However it is a bit flimsy and probably not enough for the rather big weight it must be able to lift.

Joint using servo shaft adapter

Continue reading “Testing Servo Joints for the Back of the Fuel Cube Collector”

Proof of Concept: Fuel Cube Collector

Today we attached the pulley-belt mechanism to the chassis.

From the side: Pulley belt mechanism attached 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.

Motor attached 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.

 

Whole robot with the fuel cube collector

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.

Constructing the Front of the Fuel Cube Collector

First we built a poly-cord pulley belt, to transport the cubes.

Cube in a proof of concept for the fuel cube collector

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.

Sketch of the general idea

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.

Fuel cube collector with wheels on arms pressing against a fuel cube
Close shot of the wheel and the arm. Instead of the medical tubing in the kit, we used a green theraband

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.

Fuel cube collector with wheels attached stiffly to the frame

For testing purposes, we just drove the wheels directly with motors attached beneath them.

Close shot of the wheel and the motor

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.