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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_ix</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_vii.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_ix</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_x.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 ix</font></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="48"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="4">Preface</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">For the past several decades, <i>inertial navigation systems</i> (INSs) have been used for many navigational tasks. Early on, the majority of these systems were extremely expensive because, in part, of the cost of high-quality, well-characterized sensors and typically the need for a stabilized sensor platform. This high cost limited such systems primarily to military, scientific, and commercial aircraft applications. In addition, the use of stabilized platforms resulted in this class of INS having size and power requirements too large for many applications.</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">High-quality, individually selected and characterized sensors are required in certain navigation applications to meet the relatively high-accuracy requirements over long-duration mission (months for submarines) without external position aiding. Advances in material processing have made it possible to produce small, low-cost inertial sensors (solid state and micromechanical). Although these low-cost sensors cannot be expected to meet the accuracy and precision specifications for all navigation applications, they do, alternatively, enable a new generation of low-cost, commercial navigation applications, especially when aided by other sensors, such as a <i>Global Positioning System</i> (GPS) receiver, that allow on-line calibration and error estimation.</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">There are two primary INS implementation approaches. The first approach uses a stabilized platform mechanized as the vehicle moves to maintain sensor alignment with a predetermined reference frame. The second approach uses a strap-down platform rigidly attached to the vehicle reference frame. The stabilized-platform approach has two main advantages over that of strap-down systems. First, the inertial sensors are subjected only to small angular rates. In a high-accuracy system without external aiding, this is important for three reasons: (1) sensor nonlinearity may be excited by high dynamic loads; (2) lower sensor bandwidth results in an increased signal-to-noise ratio; and (3) lower sensor range allows increased sensor sensitivity. Second, the computational load of a stabilized-platform system is smaller than that of a strap-down system. The main benefits of the strap-down approach are the decrease in navigation system size, power, and cost because of the elimination of the stabilized platform and its actuators.</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_vii.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_ix</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_x.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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