Genetic mangling of electric motors

Posted on July 9, 2009


As has been said before, we’ve taken an Intelligent Algorithm approach to our motor design framework.

We started by adding a Genetic Algorithm to the MotorFemmulator project code, and left it running on a 7 computer improvised cluster. It has yielded some results, namely the optimization of a motor from 44Nm (5kW) to 200Nm (23kW) at 90% efficiency, but the whole process of optimization is out of our control – we define the initial parameters (population size, mutation rate, reproduction rate) and then hope for the best. The best, in this case, we defined as 20 generations without improvement.

This takes a hell of a long time to produce results, is very wasteful of computer time, and does not guarantee a global optimal solution. So, also in the context of another course subject group work, we decided to add a Fuzzy Logic control over the Genetic Algorithm, so that we didn’t have to define those parameters and they would adjust on-the-fly to the current state of each generation. What looked like a neat idea quickly snowballed into a veritable Ph.D investigation… there are many more papers on the subject of fuzzy-genetic algorithms than the ones I care to read. 🙂

But eventually I found a couple of papers that promise to make it better for us. One shows how to control Mutation Rate and Crossover Rate via Fuzzy Logic to achieve a good balance between diversity (breadth of search) and convergence speed, and another one shows how to design the Genetic Algorithm with adaptive Population Size (which helps save computing cycles by eliminating the least interesting individuals, but also explodes the population size when stuck on a local maximum). This last one doesn’t have Fuzzy in it, but I’m sure I can turn one of those parameters into a Fuzzy-controlled feedback. 😉

Man, I need that vacation… but it’s still 2 weeks and 3 group works away…  😦

If it weren’t for the real benefit that we are seing as an outcome in this project (automated optimization of electric motors), I think I’d have given up by now.