CyclopsNXT

Greetings

It has been a long time since I posted any of my creations. This is because for the past few days, I had been working on possibly my most entertaining project to date: A NXT cyclops that can track faces! Before I get started, here are some pics.

Front View, base and cam

Side view, cam holder in detail

Gearing to turn the camera

I see you!

So to make this creation, I used the OpenCV wrapper for Java (JavaCV), Lejos as well as Java SE. This creations consists of two motors. One motor drives a set of gears which can tilt the camera up or down. Another set of gears rotates a geared base CW or CCW, which in turn rotates the camera. The camera itself is connected to a terminal, which is the only wired connection to an external terminal in the whole project. You can use Bluetooth webcams and do away with wires. The geared base, rotating motor and the NXT brick all sit on a pretty sturdy base, which rests on four wheels. The whole project is about 20x15x20 cm. So basically the camera has four degrees of freedom. So what does this project achieve and how does it do that? I wanted for a long time to be able to build a robot that could track objects in real time and this robot does just that. The camera gets input from the environment and sends it to the computer for processing. A Java/JavaCV program running on the computer processes this input video and draws a rectangle on all detected faces (program works with only one face though).
       Now a method in the program computes the distance of the edges of the box around the face to the edges of the video frame. If the distance from the left edge of the box to the left edge of the frame is different by more than 80px compared to the distance from the right edge of the box to the right edge of the frame, the JavaCV program on the computer sends a command to the NXT Brick to either turn left or right, so as to position the face in the center of the video frame. The same works in the y axis, where the distances from the top and bottom edges of the box around the face to the top and bottom edges of the video frame are compared. Again if the difference is more than 60px, the JavaCV program sends a command to the NXT to tilt the camera up or down depending on the scenario.
       So that is pretty much how the program works. I have posted links to the code below, from both the NXT and the Computer. It is annotated and licensed under the MIT OSI License. Feel free to go over the coed and edit it. Hopefully it is educational. If you are having problems building the robot itself, send me a message, and I can help you out.  I have posted pics above that can guide you. Oh and a huge thanks to Nashruddin whose blog taught me how to program face recognition in OpenCV! And finally here is a video showing the robot in action.

*LINKS*
Code on the NXT
Code on the computer
Classifier to detect faces, must be in the folder from which comp.class is running.

This is not the end...

Mindstorms liquid dispenser

Greetings

Here is a simple project that I had been working on for quite some time. It is a Mindstorms powered liquid dispenser. Essentially it is a simple liquid dispenser that works on the principal of a diaphragm pump. Here are some pics which will describe the apparatus better than I ever can hope to by writing

Side View

Front View

Rear View

Close up of the water delivery system

        So the principle behind the dispenser is simple. A small compressor is driven directly by two NXT motors, converting circular motion to linear motion needed to compress the air in the compressor( think pistons.) The compressed air gets pushed into an airtight water container via a small rubber tube. As the air gets pushed in, the pressure gets increased inside the container. Now there is a secondary rubber tube with one end inside the water and the other end connected to the nozzle through which water is dispensed. When the pressure inside the container increases, water gets pushed out of the container through the non air carrying tube into the open, via the nozzle. Therefore it is very important for the water container to be absolutely air tight to be able to maintain a constant pressure through expulsion of water.
        The design of the project too is nothing too complex, although it was made to make space use as efficient as possible. In the back, a small rectangular platform houses the water container, secured by two elastic restrainers. Right after that are the two motors in an upright position, directly driving the compressor. The NXT brick is situated right in front of these motors. Finally in the front is the push handle with touch sensor, along with a nozzle. Whenever the push handle is pressed, the touch sensor is also pressed, which causes the NXT to drive the motors, leading to flow of water through the nozzle. The handle returns back in place due to rubber bands. I designed the whole front setup to mimic and actual water dispenser.
        There is not a lot of programming involved in this project. The NXT runs the motors whenever the touch sensor is pressed. However, a lot of other sensors could be used. For example, the motors could start running whenever a cup is placed in the platform, with input provided to the NXT by an ultrasonic sensor. Or using a sound sensor, water could be dispensed by clapping of the hands and stopped again by doing the same. Like the Mindstorms motto, the possibilities are indeed endless!
        I have included links for the code for the NXT down below. There are three different files, one for using a touch sensor as input, the others for using a sound sensor and ultrasonic sensors as inputs. The code in all files is annotated. To compile and run these files, use the nxjc and nxj commands. If you are unsure on how to do this, here is a link that can help you out. As for the model itself, I might upload an LDD file of the model in the near future. In the mean time, you can look at the video below of the Mindstorms water dispenser in action and try to build your own version.

Link to the NXT program with the Touch Sensor
Link to the NXT program with the Sound Sensor
Link to the NXT program with the Ultrasonic Sensor

This is not the end.....

The NXT step

Greetings

For a long time, I wanted to use my programming abilities in robotics. I wanted to create a robot and program it myself to respond to stimuli, unlike the pre-programmed ones that were available in the market. This meant that I had to buy motors, PC boards, micro-controllers, switches and sensors independently, assemble them and then program them.  While I searched the net to buy these parts (A lot of companies did not ship to the Middle East, where I used to live), I started getting disheartened because of the nonavailability of the most basic micro-controllers and motors.
                Fortunately for me, Lego and MIT released the Lego Mindstorms Kit. While the NXT-G programming language was sufficient, Visual Programming lacked a certain something that had drawn me to textual programming languages. When the good guys at LeJOS released LeJOS v0.85, I immediately flashed my NXT to that version(The latest version at the time of writing is 0.90, refer to this page to see how to flash your NXT and get the LeJOS environment running on your computer) and began coding in sweet, sweet Java. I had always been fascinated by remote controlled cars, so the first thing I set out to do was to create a program to control my NXT vehicle via input from the keyboard. To do this, I created a small GUI based Java program(send.java) which acted as the control center. The program had a command log, connect, disconnect, shutdown and options(The options button has no functionality currently) buttons, and a text area to receive the input form the keyboard. The program sent commands from the keyboard to the NXT(running rec.java) via Bluetooth. The NXT acts as a slave(The main thread is pretty much stopped from executing, until a Bluetooth connection opens) and waits for input from the computer and acts accordingly. My program works in a simple manner. When I press the top arrow key, the key-code of that key specified by Java is sent to the NXT and the NXT knows to move forward, and so on. The idea is simple in concept, but it does have a few problems. One of the problems is that in this model, the sending of two commands simultaneously is a bit of a hassle. Right now, the robot can turn or move, but not at the same time. One possible solution would be to multiply the key-codes of the two arrows and  return the product as input for the NXT because for the key-codes 37, 38, 39, 40, the product of any two numbers is different from the product of any two other numbers in the set(note that the same cannot be said for addition.) In any case, the program does the work of successfully sending commands to the NXT, albeit not with a lot of options. This is just a test program, and I am working on another one with greater functionality(one that has a working options button!)
                 In any case I will put the files that run on the NXT and on the computer up for download. Please note that to run these files, you should have LeJOS installed on both the NXT and the Computer. The files to be run on the NXT will be called rec.java and the file to run on the computer will be called send.java.Here is what you have to do. Open up command prompt and and navigate to the folder where you have placed the two files. Then type in the following commands:

nxjc rec.java              (compile the rec.java file)
nxj rec                    (upload the rec.class file to the NXT)
Now go the NXT and execute the rec.nxj file. Go back to command prompt.
nxjpcc send.java           (compile send.java)
nxjpc send                 (run send.class, AFTER starting rec.nxj on the NXT)

I have once again annotated the code, explaining how and why it works. Please edit the code, add your own functionality and experiment with it. I am once again releasing the code under the MIT license.  You can use any NXT car creation you want to test out the program, but the model has to turn via a difference in the speeds of the different sets of wheels, like in a tank. I used the 30 minute model from Lego Mindstorms for testing purposes, here is a link to the instructions to build a similar model. You can replace the tracks with wheels if you want. Also, here is a video of the program and the NXT in action.

Here are the links for the two.java files. I have not created any JARs as they are really not needed.

rec.java (On the NXT)
send.java (On the computer)

This is not the end.......

What more can you ASCII for?

Greetings

I am not the artistic type, but that does not mean that I do not appreciate art. While I do like art created by others, I sometimes wish that I too was gifted with artistic abilities. Once again, using the awesome powers of Java, I was able to realize this dream. Using simple Java code, I created an image to ASCII converter program which takes an image and outputs a text file with ASCII characters, which looks like the input image when viewed all at once. In this post I will explain the basic principle behind computer generated ASCII art, and how to implement it using Java. I will release my own code for the program that I built, the program itself and a short video of the program in action. From now on, I will release all my code under the Open Source Initiative (OSI) MIT License (MIT), because the license is clean, short and easy to understand. Before I explain the principle behind ASCII art, here are some of the ASCII art created by the program: 

That's me!!

The Simpsons are ASCIIfied!

p-51 Mustang- A classic

The principle behind ASCII art is easy to understand. An image can be thought of as an 2 dimension array with rows and columns that correspond to the width and height of the image (In reality, it is more complex than that but this is a good enough understanding for the time being). Each cell in this array holds a pixel. When all these pixels are viewed together at once, you get an image. So a 400x400 image has 400 rows and 400 columns, and has 160000 pixels. Now to convert an image to text, the program has to iterate through all the pixels, get its RGB value, convert it to its gray scale value, and append a suitable ASCII character. Java has a class called the BufferedImage class, which has the methods necessary to obtain the RGB values of a pixel. Now once the RGB values(ranging from 0 to 255) of the pixel is obtained, there is a simple formula to convert it to a gray scale value. Simply take ~30% of the Red Value,  ~59% of the Green value and ~11% of the blue value and add them up together to a value ranging from 0 to 255, 0 being the darkest and 255 being the brightest. Don't worry, the BufferedImage class has the necessary methods to obtain these values,which you can see in my annotated code posted below.This value is your gray scale value. Generally gray scale value range from 0 to 1 with decimals in between, but there is no reason for them to be between 0 and 255. You could divide it by 255 to range it from 0 to 1, but why the extra hassle? After obtaining the gray scale values, the creative part begins. As you know, some ASCII characters appear darker than the others. For example, # appears darker than 0.So what the program does is obtain the gray scale value of each pixel, and according to the value, append an ASCII character to the text file. For example, if the gray scale value is in between 180 and 200(very bright), it appends a ".", and if it is 50 and 70(very dark), it appends  a "#". Currently there are nine different ASCII characters that the program chooses from to append. However, I urge you to edit the code and experiment by adding more characters, changing the existing characters, etc. For a detailed explanation, read the comments in my code which explain the function and workings of each method. The results are stored in a file called result.txt, and when viewing the results in a text editor, choose a small bold mono-spaced font, with word wrapping DISABLED. I recommend choosing images not bigger than 600x600 as the task will become more and more resource intensive with bigger images. While the current program does have an area where the results are appended, for spectacular results, open up the result.txt file and choose the best font and size to view the art. I find that Prestige Std Elite and OCR A work really well, almost giving the illusion of colors. This program is only a test, and soon I will be releasing code to a program with better GUI, more options and ultimately more robust. But until then, here is a small video below which runs you through the code of the program and explains how the program works. 

And finally here are the links to the code of the program and the actual program and the Netbeans Project. Please go through the code, experiment with it and hope you learn something out of this.

Link to code (only .java file)

Link to the Netbeans Project

Link to the program (only .jar file)

This is not the end

Aravind Rao

                  

Java to the rescue!

Greetings

Some time back, I decided to run for the position of secretary in the student council of my school. Being a secretary appealed to me; I did not want a position that was constantly in the limelight and I enjoyed tasks such as data handling and processing (student data and volunteer info). I was subsequently elected and while reviewing the duties of  a secretary, I realized that there was no real system in place to store, view and edit member data. I found out that previous secretaries had left this responsibility to the members themselves; that is the reporting of the hours volunteered and so on. It did not seem right to me to allow volunteers to self report theirs hours. However it was seemingly the only option considering there was no concrete system in place. One of my fellow student council members had the "bright" idea to use an excel document; At 300+ members and over 100 activities per year, the excel cells to be edited would exceed 30000. There had to be another method. Finally, it was Java that came to my rescue! I decided to create a Java GUI Swing App combined with a self written text file parser. Every time a new member is added, the app creates a new text file with name, grade, etc as well as a volunteer hours summary, edited to look like a table. Adding hours to members files involves using the text file parser. which searches for special indexes and edits the file accordingly. Since the data is stored as text files, it can be printed out and handed back to members to increase transparency. I set out to code the app and in about a week finished it. It was a mad rush of coding ~ 440 lines of Java. All the codes are in a single file, though looking back in retrospect, I should have used interfaces and abstract classes for more readable code. However, it was the best I could do in a week! In any case, it helped me tremendously in processing members and their hours. I also built upon this code to build a simple payroll program for a local dentist's office. Although I cannot release that code until they allow me, here is a screen shot below:

My more complex payroll app screenshot.

As you can see, it is a pretty complex app with over 1250 lines of code. I shall be however posting links for the source code and entire project of my Student Council Secretary App as well as the .jar file. I have annotated key parts of code, but if you have any questions, please post a comment question on this post. When using the app, he member files are created in the same directory as that of the app. Like always, you can use, modify and redistribute it without any license. If you do redistribute it, It would be nice if you could add my name somewhere in the file, but if you cannot, it is not really a problem. Here are the links:

Link to download zipped Netbeans project (source code in the Hours-src-hours folder.)

Link to download .jar executable file. (Not tested on Mac, but should work. Works in Ubuntu and Windows)

This is not the end...

Aravind Rao

Onto the NXT project

Greetings

Until the NXT time it is! If you picked up from the last post, you would have guessed that the NeXT post is going to something about Mindstorms NXT. And it is. In this post I am briefly going to talk about a technology which has united my two greatest passions: Programming and Robotics! Mindstorms, by Lego, is a Robotics Kit which one use to build and program fully or partially autonomous programmable robots (Robots including, but  not limited to bipedal humanoids). Lego Mindstorms was released following a collaboration between Lego and MIT's Media Lab. The Lego Mindstorms started out as Mindstorms v1.0 and the latest version now is the Mindstorms NXT v2.0, a huge leap from its predecessors in terms of processing power by the Mindstorms Brick and availability of different kinds of sensors. Lego Mindstorms NXT is programmable through the NXT-G programming software(simple programs can be built on the Brick itself), which supports Visual Programming. I, however owning to my hacker nature, decided to go one step forward and installed the LeJOS firmware on my NXT. LeJOS allows the NXT to execute special byte-code from LeJOS specific java programs! This means that you can code all you NXT programs in leJOS Java(similar to Java ME), convert it to special byte-code with the help of LeJOS NXJ on your computer(similar to the java  JDK) and transfer the byte-code to the NXT and execute it using the LeJOS Virtual Machine. As one can see, the ability to use such a powerful language greatly increases the possibilities of the Mindstorms NXT. Also LeJOS can be used to communicate(2 way data streams) with other Java programs, whether they reside in a computer, a smart phone or even another NXT! Using you cellphone to control your NXT or developing a Client-Server relationship between the NXT and the computer can be achieved through LeJOS. The methods of communication are BlueTooth and the USB specifications. LeJOS is the not the only custom firmware for the NXT; ROBOTC and BrickOS can be used to run c/c++ programs on the NXT. For now however,  I will be sticking to LeJOS. I will soon be posting a page on how exactly to get LeJOS on your NXT, as well as many clever, innovate programs for LeJOS NXT.  Until then, take a look at a list of useful sites that I have posted down below!

Never The End.

******************
**Some Useful Sites**
******************

The LeJOS API
The LeJOS PC API
Great NXT tutorials
A NXT LeJOS forum

Hello, World!

 Greetings

And here is the first post. *Drum roll*. This blog has finally taken off after...............3 weeks. I have finally found some time to post some material to this blog, thanks to the long weekend. Anyway now that things have been set in motion(perpetual, I hope), I will soon be posting links to my own programs and source code, and describe how they work, and why they work. You can download them, edit them, redistribute them(feedback them?).......the possibilities are endless. Most of my programs will be in c++ or Java, and for those out there with Lego Mindstorms NXT, I will be posting programs for the LeJOS OS on the NXT. I also always have a ton of doubts and if you are a person who is more knowledgeable than me in the field of programming(you only have to be ahead by a class), please help me out!

This is not the end...........

Aravind Rao