Saturday, January 24, 2009

How do you stop an airplane ?

At the risk of a little over-simplification, airplanes are stopped with air brakes. An almost ridiculously simple mechanism, the simplicity of which is matched only by its effectiveness.

Essentially, an air brake consists of a flap that provides extra resistance to the oncoming air and this provides resistance which slows down the plane. The beauty of the thing is that the faster a plane is moving, the more resistance it offers and the better it works. Then, as the plane slows down the braking power automatically reduces also. The thing is self adaptive.

This kind of self-governing mechanism is pretty common in engineering. And it is a useful concept to think about in several areas.

Think about traffic. One could theoretically build a central control system that controls all cars and ensures that there are no collisions and that all cars get to their destinations. The system would be fiendishly complex and will need to be dynamic as traffic patterns change. Instead, a set of simple rules are defined: stay on the left (or right depending on where you are), stop on red, go on green., don’t drive above limit.

Then, intelligent agents (drivers) are placed in each car and largely left to make local level decisions autonomously about which route they want to take, what speed is appropriate and so on. And the result is rather phenomenal as thousands of cars navigate around busy cities without any overly complex central governance.

The point is that self regulation is better than central regulation, emergent systems can be as effective as planned systems, and self-adaptive controls can be very efficient and elegant.

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