New goals for the project

After realizing a number of major difficulties with creating a lifting mechanism, we've decided to fall back on Lego's Tribot design for our project.

This decision will perhaps set us back a bit, but we're convinced that it will pay off in the end.

The altered problem is now defined as follows:

Two teams, red and blue, of modified tribot agents are collaborate in removing a number of blue and red items in a closed world. Only red team tribots can remove up red items, and the blue items can only be removed up by the blue team. If a tribot encounters an item which it is not permitted to remove, it must communicate the finding to the other tribots.

The world will start off being a simple grid made of isolation tape, where the agents can navigate around. When an agent is communicating it will be shown by an extra lightsensor being switched on and off, signaling red light, on the tribot.

Designing the mover

We've been spending some hours creating the NXTMover, which will end up representing the agents in our Multi-Agent system. The first prototype is seen below. We've used parts from the NXT box and most parts for the lift is from the Lego Technics Forklift kit.



We still some more stabilizing of the lift, but the prototype on the picture is probably not far from the final version.

Follow the black line, part 2

After having spend some hours on testing, we must conclude that it seems to be almost impossible to create a stable program that makes the NXT follow a line that curves both left and right by using bluetooth direct commands. We're using an approach that makes the NXT sweep first one way then the other, then double the distance and sweep again until the line is found again. The NXT's keeps on missing the line, and the amount of readings of the light sensor delays any other bluetooth commands to an extend which is not acceptable.

Therefore, we have decided to make the "Follow Line" program as a Lego Mindstorms NXT-G program, and execute it on the VM at the NXT. The result has shown to be very stable, and the fact that the execution of a program on the NXT still allows for direct commands over bluetooth to be received and executed. This is a feature which e.g. gives us the possibility of running the line following program on the NXT and then turning the NXT 180 degrees while the line follower is still running.

We shot a short video of two NXT's using the line following program:

NXTMover

Having the library NXTRemoteControl, we can now build another library using that.

The idea behind seperating these two levels, is that you can make countless configurations of a NXT. The NXTRemoteControl should be, and is, able to control each one of them. All you need, is to develop a library on top of it.

Our robot needs to be able to drive around and lift/move objects. Hence the name NXTMover. The library (NXTMover) will be action based, with each action running in a seperate thread. You will then be able to tell the NXTMover, to "move the robot along a line", "pick up object" or "go to this place".

Above this, we will implement some intelligence and multi agent abilities such that several NXTMovers can coorporate about moving object. More about this later. The figure below illustrates these concepts.