# Changes

,  00:23, 11 December 2017
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If we switch gears into digital signal processing land, we realize that we can implement a linear system in discrete time using what's called a difference equation. This is just a simple equation of a linear combination of past inputs and outputs. The are magical things, and you can pick coefficients tons of different stuff.

If we switch gears into digital signal processing land, we realize that we can implement a linear system in discrete time using what's called a difference equation. This is just a simple equation of a linear combination of past inputs and outputs. The are magical things, and you can pick coefficients tons of different stuff.
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The difference equation used for spaghetti is called a [https://en.wikipedia.org/wiki/Digital_biquad_filter | biquad filter]. This forms a 2nd order difference equation, as it uses the last two inputs and outputs. With a biquad, we can place two poles and two zeros anywhere we want in the s-plane.
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The difference equation used for spaghetti is called a [https://en.wikipedia.org/wiki/Digital_biquad_filter biquad filter]. This forms a 2nd order difference equation, as it uses the last two inputs and outputs. With a biquad, we can place two poles and two zeros anywhere we want in the s-plane.

=== If you think controls are cool and wanna learn more ===

=== If you think controls are cool and wanna learn more ===
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