| 522 | \begin_layout Subsubsection |
| 523 | Reduced order version |
| 524 | \end_layout |
| 525 | |
| 526 | \begin_layout Standard |
| 527 | Equations ( |
| 528 | \begin_inset CommandInset ref |
| 529 | LatexCommand ref |
| 530 | reference "eq:model" |
| 531 | |
| 532 | \end_inset |
| 533 | |
| 534 | ) ca be restructured by considering |
| 535 | \begin_inset Formula $i_{s\alpha}$ |
| 536 | \end_inset |
| 537 | |
| 538 | and |
| 539 | \begin_inset Formula $i_{s\beta}$ |
| 540 | \end_inset |
| 541 | |
| 542 | as external observations. |
| 543 | Then the state variables are |
| 544 | \begin_inset Formula $x_{t}=[\omega_{t},\vartheta_{t}]$ |
| 545 | \end_inset |
| 546 | |
| 547 | and as follows: |
| 548 | \begin_inset Formula \begin{align} |
| 549 | \om_{t+1} & =d\om_{t}+e\left(\isb{,t}\cos(\th_{t})-\isa{,t}\sin(\th_{t})\right),\label{eq:rord-state}\\ |
| 550 | \vartheta_{t+1} & =\vartheta_{t}+\omega_{t}\Dt.\nonumber \end{align} |
| 551 | |
| 552 | \end_inset |
| 553 | |
| 554 | and the onbservation equations are |
| 555 | \begin_inset Formula \begin{align} |
| 556 | \isa{,t+1} & =a\,\isa{,t}+b\omega_{t}\sin\vartheta_{t}+c\usa{,t},\nonumber \\ |
| 557 | \isb{,t+1} & =a\,\isb{,t}-b\omega_{t}\cos\vartheta_{t}+c\usb{,t},\label{eq:rord-obs}\end{align} |
| 558 | |
| 559 | \end_inset |
| 560 | |
| 561 | These equations are used by the EKF to update estimates of mean values. |
| 562 | The new matrices |
| 563 | \begin_inset Formula $A$ |
| 564 | \end_inset |
| 565 | |
| 566 | and |
| 567 | \begin_inset Formula $C$ |
| 568 | \end_inset |
| 569 | |
| 570 | are |
| 571 | \begin_inset Formula \[ |
| 572 | A=\left[\begin{array}{cc} |
| 573 | d & -e(\isb{}\sin\th+\isa{}\cos\th)\\ |
| 574 | \Dt & 1\end{array}\right],\quad C=\left[\begin{array}{cc} |
| 575 | b\sin\th & b\om\cos\th\\ |
| 576 | -b\cos\th & b\om\sin\th\end{array}\right].\] |
| 577 | |
| 578 | \end_inset |
| 579 | |
| 580 | |
| 581 | \end_layout |
| 582 | |