Online Cortex Thoughts on Science and Technology

I have just submitted my first Google Gadget.
It is called Bird of the Day, and it simply presents a photo of a new bird species each day. The photo is a public domain image from Wikipedia, and I link back to it so that you can get more information.

Here it is:

You can put it on your iGoogle page by clicking here…

I am going to write a few other versions that will complement my BirdPlanner.com site. The first will be a modification of the above where the user can enter their latitude and longitude to get birds that are present in that locale. That way people can prepare for their birdwatching trips.

I will also try writing one which is a Bird Identification Quiz. It will be a multiple choice quiz. I can vary the difficulty by sampling from birds of the same genus, from the same family, or from the whole set of birds.

This is a fun way for me to become familiar with the computational technology. The google gadget is just an XML file. The tag <Module> identifies it as a Google Gadget.

The remaining XML has three parts:

1. <ModulePrefs>, which encodes the properties of the gadget.
2. <UserPref>, which encodes the user information.
3. <Content>, which encodes the content.

My gadget is pretty straightforward.  There are no User Preferences, so I just have the first and last sections. 

You can look at the xml code here.  You will see that the workhorse of the content section is a php file that emits an html file.  In this case the gadget simply holds a simple web page.

In the future, I will write more details about how all of this works.

Kevin Knuth
Albany NY

Posted under Biology, Birds, Coding, Gadgets, Inventions, Software

Some of the limitations of the LEGO NXT system are related to the fact that, without electronic multiplexers, one can only control three motors with the NXT brick.  This individual introduces a mechanical NXT multiplexer that uses two motors but provides 12 outputs! 

I have thought about linear designs of this sort, but a rotary design is much more practical. Very nice.

An elegant worm-gear multiplexer submitted to nxtasy.org by Guy Ziv provides another solution in the event that your two outputs do not need to change direction.

Kevin Knuth
Albany NY

Posted under Inventions, Lego, Robotics

I have just uploaded three videos of a LEGO NXT rover that uses the rocker-bogie suspension system employed by the current Mars rovers.  This design is based heavily on the design presented by Brian Bagnall in his book Maximum Lego NXT: Building Robots with Java Brains

I described the rocker-bogie suspension system in a previous post.  The idea originated with the bogie, which is a set of six wheels on a train designed in such a way to keep all the wheels on a curved track.  The innovation here is to add rockers allowing the wheels to move up and down independently.  This enables the rover to handle extremely rough terrain, and as I demonstrate, climb barriers higher than the wheels themselves.  A more detailed description can be found on BrickVista Tech-Notes.

The first demo was filmed in my brother’s backyard in Wisconsin where he had just put in a fence.  The terrain is relatively rough with bumps and dips with sizes on the order of the diameter of the rover’s wheels.

The second demo was filmed in my office in the Physics Department at the University at Albany.  Here the rover climbs a pile of some of my favorite books.  Several of the book heights are on the order of the diameter of the wheels themselves.  Watch how the rockers allow the wheels to climb independently.

The third demo was filmed in the access road just outside the Physics Department.  A small parking barrier, approximately the height of a curb, is the obstacle to be overcome.  The rover is able to climb the barrier, and the rocker-bogie suspension allows its wheels to hug the barrier as it rolls over.  The rover then heads off towards a small tree… perhaps in search of life. 

We improved on the design by increasing the torque on the tires (decreasing the speed) and by replacing the front drive shafts with a gear system.  Long LEGO axles tend to take a good deal of torsion and store this energy like a spring.  This leads to oscillatory motions in the wheels.  In addition, the coupling was too weak to enable our rover to climb the desired obstacles, and our gear system overcomes this.  Another way we found to overcome the torsion of long drive shafts is to construct a shaft out of small axles joined by axle connectors.

There are more improvements to be made.  One design flaw is that the front wheels are too powerful and sometimes lift the entire front end of the rover without allowing the rockers to rotate.  This is because the back wheels are also progressing a given rate of speed and for the rockers to rotate, these wheels would have to slow down.  A properly-placed differential should solve this problem.

In the meantime, this basic rover design is sufficiently robust for outdoor exploration.

Below are several books of potential interest.

Kevin Knuth
Albany NY

Posted under Exploration, Intelligent Systems, Inventions, Lego, NXT, Research, Robotics