Use of k as discrete time index is confusing in Example 3.6

[Richard Murray]

Contributed by Jason Rolfe, Jan 2019: In Example 3.6, using k for both the discrete temporal index and the constants k_p and k_i seems unnecessarily confusing. Could you index the discrete time step by t or n or i, or is that non-standard?

[Richard Murray]

I agree this can be confusing, in particular the following equation:

x[k+1] = x[k] + h k_i e[k], u[k] = k_p e[k] + x[k]

I don’t like using t for discrete time, but we could use i? Or redefine the gains in the PI controller to be some other symbols.

[Richard Murray]

24 Jul 2019 phone call: try replacing $k$ with $j$ and see if that causes problems.

[Richard Murray]

Fixed in commit 4b44ff4.