Communication framework and a broken NXT

When I first bought the NXT the sound from its speakers were not good at all, at first I thought it was supposed to be like that, it's just Lego and probably a cheap speaker. Anyhow just a couple of days later there were no sound from it at all so for a couple of weeks ago I sent it in to be repaired/replaced and now the new one has arrived :) So that's why we haven't been able to do and write especially much the last time.

PenemuNXTFramework 0.1

Anyhow what I have done while the NXT was gone is that I've written a communication framework that's supposed to be a middle layer between the existing communication classes in leJOS and the programmer. It's based at some interfaces that you must implement and then it will handle a lot of stuff for you.

Some key features are:
Queue: Let you to setup a queue of set of data to send. This allows you to send data when the NXT has time, maybe there is much to do at the moment.
Priority: Give priority to a set of data, this means that it will be sent first of all items in the queue and it will be processed first at the receiver. Good to use for shutdown commands.
Consistent: The syntax and classes used is exactly the same ones at the NXT as at the PC.
Choose type: When you setup the communication you specify if to use USB or bluetooth. You only specify it once and you don't have to change anything else.

This is how the base part might look:
// Setup data factories
// They produce empty instances of the data objects
NXTCommunicationDataFactories DataFactories = new NXTCommunicationDataFactories(
new ServerMessageDataFactory(), new TiltSensorDataFactory());

// Setup ..
NXTCommunication NXTC = new NXTCommunication(true, DataFactories,
new NXTDataStreamConnection());

// .. and start the communication
NXTC.ConnectAndStartAll(NXTConnectionModes.USB);


// Setup a data processor
// It will be given the incoming queue of data and handle it
ServerMessageDataProcessor SMDP = new ServerMessageDataProcessor(NXTC, DataFactories);
SMDP.start();

//Add some data to the send queue
NXTC.sendData(new TiltSensorData(TS.getXTilt(), TS.getYTilt(), TS.getZTilt()))

A data factory might look like this:
public class SensorDataFactory implements INXTCommunicationDataFactory {
@Override
public SensorData getEmptyInstance() {
return new SensorData(NXTCommunicationData.MAIN_STATUS_NORMAL,
NXTCommunicationData.DATA_STATUS_EMPTY);
}

@Override
public INXTCommunicationData getEmptyIsShuttingDownInstance() {
return new SensorData(NXTCommunicationData.MAIN_STATUS_SHUTTING_DOWN,
NXTCommunicationData.DATA_STATUS_ONLY_STATUS);
}

@Override
public INXTCommunicationData getEmptyShutDownInstance() {
return new SensorData(NXTCommunicationData.MAIN_STATUS_SHUT_DOWN,
NXTCommunicationData.DATA_STATUS_ONLY_STATUS);
}
}

And part of a data processor like this:
@Override
public void ProcessItem(INXTCommunicationData dataItem,
NXTCommunication NXTComm) {
SensorData SensorDataItem = (SensorData) dataItem;

Acceleration.add(new AccelerationValues(SensorDataItem.getAccX(),
SensorDataItem.getAccY(), SensorDataItem.getAccZ()));
}

So it's not finished yet but soon I hope. Anyhow this will make things much easier for us when we want to share data to the computer and back.

Right now we are rebuilding the robot and hopefully we will upload some pictures later this evening.
We are basing the new model on the Explorer from NXTPrograms.com, it's much more stable the our previous construction.

/Peter Forss

AI and communication

While we still don't have anything new to show you right now, though that doesn't mean that we're slacking. We've started working on two different things that together should enable us to create a working prototype for our mapping robot.

I (Josef) am working on an AI for the robot so it can navigate through the room while scanning. I tried to create my own navigation class that would calculate the position of the robot based only on the rotation of the wheels, but for some reason it's not working. The algorithm to calculate the angle its facing seems to be working, but only certain values for some reason. Seems like a rounding error somewhere, but I don't know where.


public double getRobotangle(){
robotnewangle = robotangle - (Math.toRadians(CS.getDegreesCartesian()));
robotangle = (Math.toRadians(CS.getDegreesCartesian()));

leftwheelangle = ((Math.toRadians(Motor.A.getTachoCount())) - leftwheeloldangle);
rightwheelangle = ((Math.toRadians(Motor.B.getTachoCount())) - rightwheeloldangle);

leftdist = ((wheeldiameter*Math.PI)*leftwheelangle/(2*Math.PI));
rightdist = ((wheeldiameter*Math.PI)*rightwheelangle/(2*Math.PI));

return robotangle;
}


The algorithm to calculate it's position doesn't seem to work at all, even if I use values from the compass sensor. For some reason it never returns any data.


public Point getRobotpos() {
float x, y, hypotenuse;

hypotenuse = (float)(Math.sqrt((2*Math.pow((getRobotAverageDist()/robotnewangle),2))
-((2*Math.pow((getRobotAverageDist()/robotnewangle),2))*Math.cos(robotnewangle))));

x = (float)(robotpos.x + (Math.cos(getRobotAverageangle()*hypotenuse)));
y = (float)(robotpos.y + (Math.sin(getRobotAverageangle()*hypotenuse)));

robotpos.x = x;
robotpos.y = y;

return robotpos;
}


Feel free to check them both out on our Google Code site and come with tips if you have. Right now the code is a bit unstructured however. The algorithm to calculate the angle based on the rotation of the wheels is a comment right now in favor for a similar method that uses the compass sensor instead.

When my own class didn't work I was forced (for the time being anyway) to use the navigation class in leJOS, which unfortunately limits me to use only the methods provided by the class to navigate the robot. I'd rather be able to manipulate the motors at will, for example to be able to follow a wall easily.

I'm using behavior programming for my work, a really smart way of creating AI's, since it's so easy implementing, editing or removing different parts of it. I recommend reading the leJOS tutorial about it if you're interested.

Peter is working to improve our communication, which as you could see in our movie works already, but could be made a lot smoother and more structured. The idea of the new communication class is that you add data that you want to send to a queue. The class will then process one item at a time and send it over either USB or Bluetooth (depending on what you want to use). The receiver will add each received item to a list and you may then process them whenever you want. There is one client (NXT) part and one server (PC) part in this.

Hopefully, when we're done with these things, or at least got something that works, we can combine it with the scanning algorithm we already have and with small tweaks to the Graphic Interface a crude prototype that should be able to move around and scan a room, and in real-time paint it up on a computer screen.

/Josef