Tuesday, June 26, 2012

Making Beirut v1.0


I was always frustrated of how the hardware and the DIY community is still small in Lebanon. This keeps reminding me of how we are brought up into thinking that we are not made for it. It is just not meant to be: we are too busy with our social, political and economic  problems that for some reason we forgot a big problem- we just don't make stuff anymore we consume.

Obviously the community is there, it just need the right environment to grow. "Making Beirut v1.0" is the first actual gathering for the hardware maker community in Lebanon. In my opinion, Beirut is not ready for a Maker Fair <yet>, however, and as the name of the exhibition suggests, we would like to promote the maker culture, spread the knowledge and gather the community so that v2.0 will be closer to the full deal.

During four days many items will be exhibited. I, myself will be exhibiting a couple of items that can be found on my blog and elsewhere. And I can ensure the people attending the exhibition that they will also be an active part of the exhibition where they can play with robots, interact with tables, experiment with photography, and even play with electronics!

So get your geeky spirit ready, and join the makers at karaj and learn how you can promote and meet a community that is hacking its way into the city as they want to see it.


Tuesday, June 5, 2012

The ShakerBOT: Snakeboard inspired robot

When one thinks about robot locomotion, the first thing that comes to mind are bipedal robots or mobile wheeled robots. This is not the case with Sevag Babikian. As part of a research done by the Mechanical Engineering department at the American University of Beirut, Sevag built a wheeled robot which motion is inspired from the snakeboard. He called it the ShakerBot.




What is the ShakerBot made of? 

As we can see above, the Shakerbot is made up of the following components:
- A plexiglass laser cut chassis
- A central DC motor connected to a 2kg metallic flywheel
- A couple of DC motors (steering motors) on the front and back. These motors are called steering motors and they are connected to an axle which in turn is connected to friction wheels to guide the robot.
- A couple of castor wheels on both sides of the robot to support its weight.

All the motors are connected to quadrature encoders to compute their instantaneous position and speed.  Each motor is driven using an L298 based motor driver circuit, capable of driving up to 4A continuously.The brain of the Shakerbot is an Arduino Mega board. The Arduino Mega communicates wirelessly via bluetooth (ARF32 module) to a PC for teleoperation.

So, how is motion generated on this ShakerBot? 

 

Have you ever seen a snakeboard? Or have you ever felt the urge to kneel on a rotating chair and start turning in order to experience the effects of inertia, or those of dizziness? Well, ShakerBot operates on the same principle. The flywheel generates momentum which drives the robot around. Steering motors, as well as the flywheel, move in a sinusoidal fashion. The motion pattern of the flywheel and of the steering motors are what generate the different robot motions (forward, backward, rotation, parallel park etc.). The mathematics are quite complicated and can be fully understood in this publication by Lewis A. et al (1993).

The following video explains the mechanism better


The Arduino Mega board does all the complex mathematical and trigonometric equating and controls the DC motors accordingly.

How does the ShakerBot communicate with the PC? 

 

As mentioned above, the computing is done on the Arduino Mega board. However, it is required to have a wireless connection with a PC in order to teleoperate the ShakerBOT and tell it where to go. A couple of months ago I received a bluetooth module from Farnell electronics. It is the low cost ARF7044A based on the ARF32 bluetooth module manufactured by Adeunis (you can find it on the Farnell Electronics website). I decided to help Sevag out in implementing the bluetooth communication on the ShakerBot using this board. For 23£ I can tell you that this chip worked like a charm. We were able to achieve instantaneously a wireless communication, simply by wiring it to the serial Tx and Rx of the Arduino Mega and by connecting it to our laptop's bluetooth.
The ARF7044 connected to the arduino shield
I will be using more of this ARF7044 in the future and I will post whatever I find. 
  
On another note, for all the electronics makers, geeks and hackers out there, I discovered lately a website with a large  community powered by Farnell electronics that you should check out. It is called element14

Sevag and his ShakerBOT

Concluding thoughts

 

The easiest mechanism for robot locomotion is the differential drive mechanism. However if we look at humans we see that we use bipedalism very efficiently. We can walk, run and even climb with minimal energy consumption. This is because we make use of gravity to ease up the locomotion. Up until now, every attempt to mimic human bipedalism on humanoid robot has been very inefficient. This might change as technology as we learn how to fully harbor the physics and dynamics of the system. Same thing can be thought about this ShakerBOT. Humans use snakeboard efficiently, they harbor the momentum generated by their bodies in order to propel. Maybe this ShakerBOT and after plenty of modifications and improvements will turn out to be an efficient locomotion method after all.

Finally, I am very excited to see the maker movement growing fast in Lebanon. First Mounir and his Octocopter and now Sevag and his ShakerBOT. I can ensure you that there many more creative people just waiting to expose their work!

Monday, April 16, 2012

Lebanese OCTO Copter built by Mounir Zoorob

A few days ago, I bumped into Mounir Zoorob's OCTO copter project. It is a very impressive flying monster that Mounir designed entirely by himself. It is 1m in diameter and it has a 3 axis camera Gimbal, all designed from scratch. Apparently he has spent over 4 months very hard at work to finish it on time. I must say he did a pretty amazing job. So I invited Mounir on DepotBassam to write a small review of his OCTO copter flying machine, and here is his post:

Before starting, I would like to mention that the materials used are not the best choice. However, since there was nothing available in this part of the world and shipping carbon fiber parts was not possible I had to go with aluminum and Plexi glass instead. (on that subject, review DepotBassam's post on Lebanese electronics shops for more info)
I used 2cm * 2cm * 1 mm aluminum square tubes and the motors are from DIY drones with 35cm wires 2836/9. Each engine has a thrust of 1300g approximately.


I'm using Ardumega from DIY Drones as the main controller with magnetometer + sonar. So far it has proven to be the best thing I have ever bought for this hobby. i enjoyed it so much i bought it as a kit and soldered everything together


I designed and laser cut the case from a 3mm black plexiglass to hold both the Ardumega and the receiver.


As for the motor controllers, I bought 8 25AMP Turnigy ESC's from HobbyKing.
I am currently using 11*4.7 props but will go with the 12 later on down the road. All well balanced


Ardumega will be responsible for the compensation on the roll/pitch axis at the moment. Later on, I will upgrade it to control all three axis.

This is my camera gimbal. It currently has 2 active axis , but later on I will upgrade it to 3 axis. Currently I'm working on finalizing roll and pitch, but I am still waiting for the right parts to arrive.   
Wires were also taken into consideration during the design phase :) very neat :) 
Wires from the ESC's  to main power source are all well soldered and added heat shrink.
Here's the OCTO almost ready for a test flight :)

Here is the OCTO after couple of flights. I modified the design of the Gimbal and I integrated a new landing gear design on it
I promise the next design will be more elegant. With the cash at hand and the time this is the best I was able to come up with.

Here is a sample picture from the video I'm taking from the OCTO


Here is the first video from the OCTO, of course it looks better now but this is just a sample.



For those who love beer, here's one for you :) Note: I got rid of that beard
Feel free to ask me anything, your feedback is important to me. It better be a good one though!

Saturday, April 14, 2012

Wall Mounted Double Pendulum for Experimental Photography

(or how we went to outer space shot some galaxies and came back)
Through the lens of Abir Ghattas

My first interest in chaotic behavior can be traced back to this post. This time however, instead of simply developing a simulator I decided to build a real double pendulum. Watching a double pendulum dance erratically was worth a million simulation. If you are follower of this blog you will realize instantly that I could never let this opportunity pass without transforming it into some sort of a crazy experiment (-mostly photographic-).
 
The first step in the process was the design of the pendulum. The dimensions were chosen such as to maximize the chaotic behavior. Click here to download the AutoCAD .dwg file.

All dimensions are in cm
The material was chosen to be transparent 2mm thick plexiglass (4mm would have been ideal-but it was not available). The reason I chose to use a transparent material was so that the light can pass through in photography. I would definitely choose another material if I was using the pendulum for decorative purposes.

As for the components needed:
- 6mm ball bearings x4
- 6mm Hex Screw with nuts and washers  x2
- 3mm wall mounting screws and screw anchors x2

The following slideshow displays the assembly process


Here's a video of the double pendulum in action


After the assembly, Abir Ghattas and Patrick Abi Salloum came over for the photoshoot. We used LEDs of different colors connected to 3V coin batteries and we took long exposure pictures in the dark.
Left to Right: (1) Abir painting the pictures with LEDs (2)focusing (3) Patrick vs. Abu Ali
Courtesy of Patrick Abi Salloum

"Angel of Death" courtesy of Patrick Abi Salloum
For the result check Abir's website: http://abirghattas.com/double-pendulum-experimental-shoot/
and Patrick's flickr: http://www.flickr.com/photos/patrickas/7072749767/in/photostream