[ntenenz]

While most can learn to ride a bicycle with minimal effort, it turns out the control of an idealized bicycle is actually quite complex and has a storied history. For a brief rundown (and insight into the complexity of the problem), scan through this presentation (pdf warning): http://www.control.lth.se/media/Staff/KarlJohanAstrom/Lectur...

[gtycomb]

"Feedback Systems, An Introduction for Scientists and Engineers" by the same author, Karl Johan Astrom (and Richard Murray) is a readable introduction on how the basic equations come together. Think of it as the innate "language of motion" that is wired in our brain that allows us to bike and walk so effortlessly. Thanks to Newton and friends for their discovery.

[fwdpropaganda]

Hey, you seem to know a bit about the subject. What is the reason for the name "feedback systems"? (I understand a name is just a name, but the fact that I don't understand why that name was picked suggests to me that I'm missing something.)

EDIT: From that book: The term feedback refers to a situation in which two (or more) dynamical systems are connected together such that each system influences the other and their dynamics are thus strongly coupled." So.... the whole system is governed by a system of coupled differencial equations...? This is so broad it's almost meaningless.

[HeyLaughingBoy]

A feedback control system, aka a "closed-loop" control system is one in which the actual output is sampled and compared to the desired output and the "controller" adjusts the system gain to reduce the error (difference between actual and desired outputs).

i.e., a portion of the output is "fed back" to the input to obtain that difference between actual and desired output.

Does that help?

[moorepants]

Newton and friends had nothing to do with discovery of feedback controls :)

[gtycomb]

Well, differential equations makes control theory. Write a system of differential equations, come up with an iterative scheme to solve it and there you begin to see the idea of feedback.

[moorepants]

Actually the control of the bicycle is surprisingly simple regarding how complex the vehicle dynamics are. A simple proportional feedback control based on a roll rate measurement can balance a bicycle, causing it to always steer into the fall.