Friday, March 17, 2006

Evolving Telecommunications


NASA has a group that is working in Evolvable Hardware: Evolvable Systems Group.

The Evolvable Systems Group investigates computer algorithms that automate the design and optimization of complex engineering systems for current and future NASA missions. Our overall goal is to dramatically increase mission reliability and science return through development and application of adaptive and evolutionary algorithms.

There is an interesting and strategic application of Evolutionary Computation in Evolvable Hardware: Automated Antenna Design.

The spectrum of antenna designs for applications in communication, radar, and remote sensing systems is vast, and there is an increasing need for high-performance, customized antennas. Current methods of designing and optimizing antennas by hand are time and labor intensive, limit complexity, increase the time and cost expended, and require that antenna engineers have significant knowledge of the universe of antenna designs.

The use of evolutionary programming techniques to automate the design of antennas has recently garnered much attention. Considerable research has been focused on determining whether evolutionary techniques can be used to automatically design and optimize antennas so that they outperform those designed by expert antenna designers, and even whether evolutionary techniques can be used to design antennas in cases where humans are simply unable to.

The NASA Group used a Genetic Algorithm to help to generate the ST5 Antenna.

We devised a LOGO-like antenna constructing programming language where each node in the tree-structured representation is an antenna-construction command. An antenna is created by starting from the root of the tree and executing the commands at each node in the tree. In constructing an antenna, the current state (location and orientation) is maintained, and subsequent commands add wires or change the current state. We then used a genetic algorithm (GA) to evolve genotypes that specify the design for one arm, and built the complete antenna using four copies of the evolved arm.

The two antennas generated (ST5-3-10 and ST5-4W-03) have interesting features for space missions:

First, there is the potential of needing less power. Antenna ST5-3-10 achieves high gain (2-4dB) across a wider range of elevation angles. This allows a broader range of angles over which maximum data throughput can be achieved. Also, less power from the solar array and batteries may be required.

Second, the evolved antenna does not require a matching network nor a phasing circuit, removing two steps in design and fabrication of the antenna. A trivial transmission line may be used for the match on the flight antenna, but simulation results suggest that one is not required.

Third, the evolved antenna has more uniform coverage in that it has a uniform pattern with small ripples in the elevations of greatest interest (between 40 and 80 degrees). This allows for reliable performance as elevation angle relative to the ground changes.

Finally, the evolved antenna had a shorter design cycle. It was estimated that antenna ST5-3-10 took 3 person-months to design and fabricate the first prototype as compared to 5 person-months for the conventionally designed antenna.

Here you are the antennas generated through Evolutionary Computation:



A possible application of ST5 antennas.

Just for a comparison, note how different those two antennas are of more typical antenna models:

Até Mais!! (Until Later!!)



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