diff --git a/paper/paper.org b/paper/paper.org index 40ec259..2957695 100644 --- a/paper/paper.org +++ b/paper/paper.org @@ -289,14 +289,24 @@ In order for the fusion to be "robust", meaning no phase drop will be induced in The goal is to design two complementary filters $H_1(s)$ and $H_2(s)$ such that the super sensor noise uncertainty is kept reasonably small. -This problem can be dealt with an $\mathcal{H}_\infty$ synthesis problem by considering the following generalized plant: +To define what by "small" we mean, we use a weighting filter $W_u(s)$ such that the synthesis objective is: +\begin{equation} + \left| W_1(j\omega)H_1(j\omega) \right| + \left| W_2(j\omega)H_2(j\omega) \right| < \frac{1}{\left| W_u(j\omega) \right|}, \quad \forall \omega +\end{equation} + +This is actually almost equivalent (to within a factor $\sqrt{2}$) equivalent as to have: +\begin{equation} + \left\| \begin{matrix} W_u W_1 H_1 \\ W_u W_2 H_2 \end{matrix} \right\|_\infty < 1 +\end{equation} + +This problem can thus be dealt with an $\mathcal{H}_\infty$ synthesis problem by considering the following generalized plant (Figure ref:fig:h_infinity_robust_fusion): \begin{equation} \begin{pmatrix} z_1 \\ z_2 \\ v \end{pmatrix} = \underbrace{\begin{bmatrix} - W_1 & W_1 \\ - 0 & W_2 \\ - 1 & 0 + W_u W_1 & W_u W_1 \\ + 0 & W_u W_2 \\ + 1 & 0 \end{bmatrix}}_{P_{\mathcal{H}_\infty}} \begin{pmatrix} w \\ u \end{pmatrix} @@ -305,7 +315,7 @@ This problem can be dealt with an $\mathcal{H}_\infty$ synthesis problem by cons Applying the $\mathcal{H}_\infty$ synthesis on $P_{\mathcal{H}_\infty}$ will generate a filter $H_2(s)$ such that the $\mathcal{H}_\infty$ norm from $w$ to $(z_1,z_2)$ is minimized: #+NAME: eq:Hinf_norm \begin{equation} - \left\| \begin{matrix} z_1/w \\ z_2/w \end{matrix} \right\|_\infty = \left\| \begin{matrix} W_1 (1 - H_2) \\ W_2 H_2 \end{matrix} \right\|_\infty + \left\| \begin{matrix} z_1/w \\ z_2/w \end{matrix} \right\|_\infty = \left\| \begin{matrix} W_u W_1 (1 - H_2) \\ W_u W_2 H_2 \end{matrix} \right\|_\infty \end{equation} The $\mathcal{H}_\infty$ norm of Eq. eqref:eq:Hinf_norm is equals to $\sigma_n$ by defining $H_1(s)$ to be the complementary filter of $H_2(s)$: @@ -313,7 +323,6 @@ The $\mathcal{H}_\infty$ norm of Eq. eqref:eq:Hinf_norm is equals to $\sigma_n$ H_1(s) = 1 - H_2(s) \end{equation} - #+name: fig:h_infinity_robust_fusion #+caption: Generalized plant $P_{\mathcal{H}_\infty}$ used for the $\mathcal{H}_\infty$ synthesis of complementary filters #+attr_latex: :scale 1