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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>page_230</title> <link rel="stylesheet" href="reset.css" type="text/css" media="all"> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> </head> <body> <table summary="top nav" border="0" width="100%"> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_229.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_230</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_231.html">next page ></a></td> </tr> <tr> <td id="ebook_page" align="left" colspan="3" style="background: #ffffff; padding: 20px;"> <table border="0" width="100%" cellpadding="0"><tr><td align="center"> <table border="0" cellpadding="2" cellspacing="0" width="100%"><tr><td align="left"></td> <td align="right"></td> </tr></table></td></tr><tr><td align="left"><p></p><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td align="right"><font face="Times New Roman, Times, Serif" size="2" color="#FF0000">Page 230</font></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">measurement is described by</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><img src="94ddcd1fe7dcb9ab01d66a3084f08a6f.gif" border="0" alt="0230-01.GIF" width="387" height="19" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><img src="84ecfeca8d3f66bf3f399cd7682301c8.gif" border="0" alt="0230-02.GIF" width="370" height="19" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><img src="c8d231740b08cb41622aef8b59d1882e.gif" border="0" alt="0230-03.GIF" width="371" height="61" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><img src="d5fdfb3ceae69409f1d109f2b6425d1c.gif" border="0" alt="0230-04.GIF" width="371" height="60" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">Based on Eq. (6.162), two approaches are possible for estimating the alignment error. In the first approach, </font><font face="Symbol" size="3"><i>d</i></font><font face="Times New Roman, Times, Serif" size="3">f could be used to drive a Kalman filter with state error dynamics as previously defined and measurement matrix</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><img src="dd1fe18d2a7201f373f9382bbc64d487.gif" border="0" alt="0230-05.GIF" width="330" height="18" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">where Z</font><font face="Times New Roman, Times, Serif" size="1"><sub>3</sub></font><font face="Times New Roman, Times, Serif" size="3"> is a three-dimensional zero vector and</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><img src="29c0b681f004f9e40832bc81091d4424.gif" border="0" alt="0230-06.GIF" width="113" height="60" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">From the system description and measurement matrix, it is clear that </font><font face="Symbol" size="3"><i>脦</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>d</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3"> is completely unobservable. In the case in which the system is nearly level, the <i>w</i>-axis accelerometer bias is completely observable. The accuracy with which the north and the east alignment errors can be estimated will depend on the accuracy of the east and the north accelerometers and the amount of platform motion due to disturbances. In theory, portions of the disturbance motion could be modeled through state-augmentation techniques. In practice, this is difficult. Therefore vibration and disturbances will limit the achievable accuracy. In an alternative approach, the first two components of </font><font face="Symbol" size="3"><i>d</i></font><font face="Times New Roman, Times, Serif" size="3">f could be passed through a simple low-pass filter with gain 1/g. The outputs are interpreted as <img src="1bdcd1229966e3e647911ca61fd96e9f.gif" border="0" alt="C0230-01.GIF" width="26" height="15" /> and <img src="02576bfeaf9895c3c578381f094d2d03.gif" border="0" alt="C0230-02.GIF" width="18" height="15" />, respectively. In either case, the estimates are used to adjust <img src="b0f2374ffecda6c473ed46ed9904eedb.gif" border="0" alt="C0230-03.GIF" width="34" height="24" /> until </font><font face="Symbol" size="3"><i>d</i></font><font face="Times New Roman, Times, Serif" size="3">f is zero. The accuracy of this approach will also be limited by instrumentation imperfections, vibration, and disturbances. At the conclusion of the process, the analytic version of the navigation frame is nominally in alignment with the actual navigation frame (i.e., leveling has been achieved). Again, as with the mechanized approach, leveling accuracy is directly proportional to the uncompensated accelerometer bias (1 m rad per 1-g bias).</font><font face="Times New Roman, Times, Serif" size="3" color="#FFFF00"></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table></td></tr></table><p><font size="0"></font></p>聽 </td> </tr> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_229.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_230</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_231.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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