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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_226</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_225.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_226</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_227.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 226</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"><img src="4c6c1c38aa385bd7f883d4f4f41741cd.gif" border="0" alt="0226-01.GIF" width="337" height="80" /></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 </font><font face="Symbol" size="3"><i>娄</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"> = -<i>g</i>. These single-channel error models are derived directly from Eq. (6.85), under the assumptions stated above. The position variables have been converted to meters by use of <i>n</i> = <i>R</i></font><font face="Symbol" size="3">l</font><font face="Times New Roman, Times, Serif" size="3"> and <i>e</i> = <i>R</i> cos(</font><font face="Symbol" size="3">l</font><font face="Times New Roman, Times, Serif" size="3">)</font><font face="Symbol" size="3">F</font><font face="Times New Roman, Times, Serif" size="3">, where (<i>n</i>, <i>e</i>) are the position error variables in meters corresponding to the geodetic position variables (</font><font face="Symbol" size="3">l</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Symbol" size="3">F</font><font face="Times New Roman, Times, Serif" size="3">) in radians. Any one set of four equations may be analyzed to study the single-channel error behavior or observability. The three sets of equations are <i>not</i> meant to be used together. Note the single-channel vertical error dynamics have characteristics (instability) distinct from those of the lateral error dynamics.</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">In the above equations, the terms (<i>a</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>N</sub></font><font face="Times New Roman, Times, Serif" size="3">, a</font><font face="Times New Roman, Times, Serif" size="1"><sub>E</sub></font><font face="Times New Roman, Times, Serif" size="3">, a</font><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">) and (<i>g</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>N</sub></font><font face="Times New Roman, Times, Serif" size="3">, g</font><font face="Times New Roman, Times, Serif" size="1"><sub>E</sub></font><font face="Times New Roman, Times, Serif" size="3">, g</font><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">) represent the accelerometer and the gyro measurement errors in navigation frame. For a mechanized system, these errors are identifiable with specific sensors. For a strap-down system, the geographic-frame errors are related to the individual sensor errors by the platform-to-navigation-frame transformation matrix, which would be an identity if the platform were level and north pointing.</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">Figure 6.12 shows a block diagram implementation of the north channel error equations, with </font><font face="Symbol" size="3"><i>娄</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>E</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3"> = 0. The upper loop (including </font><font face="Symbol" size="3">u</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>N</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> and </font><font face="Symbol" size="3">e</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>E</i></sub></font><font face="Times New Roman, Times, Serif" size="3">) is a Schuler loop. For short time periods, the lower loop may be neglected, resulting in a particularly simple error model that applies equally well to either the north or the east channel error dynamics. This error model is represented as</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="f0f1e15b4397ddef6010dcbd8b4e17f5.gif" border="0" alt="0226-02.GIF" width="360" 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">This equation has been used in previous examples.</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><table border="0" cellspacing="0" cellpadding="0" width="100%"><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 align="center"><font face="Times New Roman, Times, Serif" size="3"><img src="688947ea90a77361ff07d38bb1dd3912.gif" border="0" alt="0226-03.GIF" width="263" height="261" /></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" width="100%"><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 align="center"><font face="Times New Roman, Times, Serif" size="2">Figure聽6.12<br />Block聽diagram聽of聽simplified聽north聽channel聽error聽model.</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_225.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_226</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_227.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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