A working prototype!

We are happy to announce that we now have a working prototype. Our robot can scan its surroundings and return data to a server which in turn visualizes it.



This was the try ever in creating a real map, and the results aren't very impressive. Fortunately we've already managed to improve it quite a bit from that, although there is still very much left to be done.



A simple AI controls the robot to reach around to be able to scan. Because of bugs in the current release of leJOS we have been unable to use the Compass Sensor and the as a consequence the accuracy has been suffering. This is something we hope will improve fairly soon.

Also, the AI is so far very simple, but thanks to the behavior based programming we're using, it will be relatively simple to continue working on what we have and expanding it until we some day will have an algorithm which can tackle most problems with reasonable accuracy.



The bar to the left is a control bar which shows some data from the robot and also has options for what you want to be painted. The labels are pretty self-evident, save for "Bumps" which is simply when a behavior has taken over from the default forward in a straight line. Blue indicates that the ultrasonic scanner in front has detected an obstacle and red that the robot has crashed into something with its bumper.

The arena of today was a (roughly) 3 by 1.5 meter rectangle, and you can clearly see the shape of the area, although it's far from perfect. Considering how early in the project we are we're quite satisfied. In fact, we're following our schedule pretty nicely. This far was about what we planned to be by the end of next week.

Now we will continue to work on mainly the AI, to give it an intelligent algorithm instead of the almost random we have now. Naturally we will continue to improve the other aspects as well, so stay tuned!

/Josef and Peter

New Robot

As promised we have constructed a new robot that probably will be the one, or at least very similar to the final product. It is based on the Explorer robot from Nxtprograms.



Our requirements for the physical units was that it has to be able to rotate around its own axis (a requirement for the leJOS navigation classes) and that the IR sensor has to have a 360 degree field of view. A bonus with this model compared to others we have considered is that the IR sensor rotates directly on a motor. In earlier versions we had to convert between the rotation of the motor and the sensor, something we don't have to worry about anymore.


Aside from changing the sensor on top to our IR sensor, we have added a compass sensor and fitted the Ultrasonic sensor in front instead. We also slightly modified the top motor and sensor so that its rotational axis is between the wheels, something that will facilitate calculating the position of obstacles.

Today we have also done several tests to determine how accurate the navigation classes are, and the results are somewhat disappointing. For some reason navigation with the help of the compass sensor is actually less accurate than a simple tacho navigator that only uses the rotation of the wheels to navigate. Also, bugs with both classes severely limits the amount of methods we can use and still maintain a reasonable accuracy. For now we have settled on using Forward(), Backward() and Rotate(), which is accurate enough for our needs. Hopefully we (or leJOS, which is still in beta after all) will solve some of the problems and we won't limited to these forever.

/Josef and Peter

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

New release of leJOS firmware

I've now updated the robot and the computers to leJOS 0.85.
According to http://lejos.sourceforge.net/ the changes are:

• better support and documentation for MAC OS X, including the Fantom USB driver
• a Netbeans plugin
• improved JVM speed and many more amazing improvements by Andy
• support for the new LEGO color sensor in the NXT 2.0 set
• now supports the instanceof keyword
• detection of rechargeable batteries and improved battery indicator
• nanosecond timers and improved timer support with the Delay class.
• % operation on floats and doubles
• Class, including the isAssignableFrom(Class cls) method
• display of LCD screen in ConsoleViewer
• major speed and accuracy improvements to the Math class from Sven
• platform independent lejos.robotics packages
• new navigation proposal (work in progress) that is platform independent, supports more vehicles, has better localization support, and new concepts of pose controllers and path finders
• preliminary support for probabilistic robotics, including general purpose KalmanFilter class using matrix algebra
• reworking of the Monte Carlo Localization classes
• limited java.awt and java.awt.geom classes

Sounds good :)

/Peter F

Old memories

Before NXT there was RIS with RCX and I have two of those.
A couple of years ago me and a friend built two robots that were able to find eachother, dock and then exchange a ball.

One of them has a lamp and the other one has a lightsensor. The "child" scans 360° to find the lightest point and then head for that direction. On his way he is doing small adjustment to always head for the lightest point, in other words the "mother".

Here is a video showing the docking process:


It's a little bit sad that I've lost the latest version of the program that contains the "ball exchanging" part (and I haven't got the time to rewrite it) so the video dosn't show that.

This isn't actually part of PenemuNXT, just fun to show the world :)

/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

Description document

Today we published two PDF-documents describing our project PenemuNXT more in detail. One in Swedish and one in English.

You can download them from here:

PenemuNXT - Swedish
PenemuNXT - English