root / docs / www / colonyscout / sensors.php @ 781890a0
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| 1 | f59acf11 | Dan Shope | <?php
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| 2 | $cacheFile="cache/sensors.html"; |
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| 3 | if (file_exists($cacheFile)) //we can read this cache file back reduce database load |
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| 4 | {
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| 5 | header("Content-Type: text/html"); |
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| 6 | readfile($cacheFile); |
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| 7 | exit;
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| 8 | } else {
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| 9 | ob_start(); //start buffering so we can cache for future accesses
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| 10 | } |
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| 11 | ?>
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| 12 | |||
| 13 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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| 14 | <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head> |
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| 15 | <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"/> |
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| 16 | <meta name="description" content="Scout fuses sonar with IR sensors to provide realtime feedback about the robots' environment."/> |
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| 17 | <meta name="keywords" content="sonar, ir, sharp, COTS, Scout, feedback, control system, maxbotix"/> |
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| 18 | |||
| 19 | <?php include("header.php"); ?> |
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| 20 | <title>Sensors | ColonyScout.com</title> |
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| 21 | |||
| 22 | </head>
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| 23 | <body bgcolor="#eeeeee"> |
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| 24 | |||
| 25 | <div id="general"> |
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| 26 | <?php include("nav.php"); ?> |
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| 27 | <div id="body"> |
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| 28 | <div id="body-boxes"> |
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| 29 | <div class="box-row"> |
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| 30 | <div class="white-top"></div> |
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| 31 | <div class="white-body text-box"> |
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| 32 | <a href="javascript:;" title="Click to Expand" onmousedown="toggleDiv('sensor');"> |
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| 33 | <h1>Sensor Fusion</h1><img src="images/btn_expand.png" /></a> |
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| 34 | <p class="description">The Scout sensor suite affords increased situational awareness over comparably |
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| 35 | priced platforms<span class="super">1</span>. Scout fuses long range sonar with short |
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| 36 | range IR sensors and LED reflectance sensors to provide realtime feedback about the robots' |
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| 37 | environment. Commercially available off-the-shelf components were used where possible, |
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| 38 | selected based on range, accuracy, and repeatability characteristics. |
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| 39 | <br/><br/><a href="javascript:;" onmousedown="toggleDiv('sensor');"><em>learn more >></em></a> |
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| 40 | </p>
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| 41 | <div class="hr"></div> |
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| 42 | |||
| 43 | 781890a0 | Dan Shope | <div id="sensor"> |
| 44 | f59acf11 | Dan Shope | |
| 45 | <h2>Environment Mapping</h2> |
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| 46 | 781890a0 | Dan Shope | <img src="/images/sensors_sonar.jpg" style="float:left;margin:0px 10px 10px 0px;"> |
| 47 | f59acf11 | Dan Shope | <p>Ultrasonic ranging sweeps 360 degrees around each Scout robot, providing up to 48
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| 48 | measurements per cycle. A compact stepper motor provides precise and rapid position control. The high resolution and |
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| 49 | fast scanning speed are appropriate for 2D mapping and navigation.</p>
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| 50 | <p>The Maxbotix® EZ™ line of sonar rangefinders was chosen for their proven accuracy and |
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| 51 | long term reliability<span class="super">2</span>. The EZ4 provides the narrowest sensing |
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| 52 | area of the EZ™ family, allowing higher precision maps to be produced, while still
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| 53 | providing wide coverage for obstacle detection.</p>
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| 54 | 781890a0 | Dan Shope | <div class="hr" style="clear:both;"></div> |
| 55 | f59acf11 | Dan Shope | |
| 56 | <h2>Cliff Detection</h2> |
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| 57 | 781890a0 | Dan Shope | <img src="/images/sensors_cliff.jpg" style="float:left;margin:0px 10px 10px 0px;"> |
| 58 | f59acf11 | Dan Shope | <p>A trio of short range Sharp® IR rangefinders provide early warning of sharp drop-offs that |
| 59 | could compromise the robot's mission.</p>
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| 60 | 781890a0 | Dan Shope | <div class="hr" style="clear:both;"></div> |
| 61 | f59acf11 | Dan Shope | |
| 62 | <h2>Odometry & Vehicle Dynamics</h2> |
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| 63 | 781890a0 | Dan Shope | <img src="/images/sensors_imu.jpg" style="float:left;margin:0px 10px 10px 0px;"> |
| 64 | f59acf11 | Dan Shope | <p>Vehicle position is tracked by quadrature encoders on each wheel resulting in 3mm linear accuracy
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| 65 | <span class="super">3</span>. A custom IMU (inertial measurement unit) consisting of a 3-axis accelerometer |
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| 66 | and pitch+yaw-rate gyroscope provide detail of the vehicle's motion in three dimensions. |
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| 67 | </p>
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| 68 | 781890a0 | Dan Shope | <div class="hr" style="clear:both;"></div> |
| 69 | f59acf11 | Dan Shope | |
| 70 | <h2>Complementary Sensing</h2> |
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| 71 | <p>The sonar rangefinders are optionally supplemented by short range LED reflectance sensors for close wall
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| 72 | 781890a0 | Dan Shope | following. A sensor on the front bumper provides resolved impact detection for escape manuevers or |
| 73 | f59acf11 | Dan Shope | when manipulating objects. |
| 74 | </p>
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| 75 | <div class="hr"></div> |
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| 76 | |||
| 77 | <div id="reference-box"> |
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| 78 | <ol>
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| 79 | <li>Comparison with commercially available robots valued at <$500 USD.</li> |
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| 80 | <li>PDF: <a href="http://www.maxbotix.com/uploads/Pendulum_Test_Results.pdf">Maxbotix® EZ4™ Sensor Testing</a></li> |
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| 81 | <li>48 clicks per revolution, 42mm diameter wheel. (42mm*pi)/48=2.7488mm</li> |
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| 82 | </ol>
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| 83 | </div>
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| 84 | |||
| 85 | </div><!--end 'sensor' collapse--> |
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| 86 | </div>
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| 87 | |||
| 88 | <div class="white-body text-box"> |
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| 89 | <a href="javascript:;" title="Click to Expand" onmousedown="toggleDiv('communication');"> |
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| 90 | <h1>Communications</h1><img src="images/btn_expand.png" /></a> |
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| 91 | <p><span class="description">Scout communicates over several protocols, providing a robust interface |
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| 92 | over long distances. Inter-robot communications and control commands are broadcast over a self organizing |
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| 93 | high bandwidth mesh network. The robots also broadcast over IR (infrared light) for localization. |
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| 94 | <br/><br/><a href="javascript:;" onmousedown="toggleDiv('communication');"><em>learn more >></em></a> |
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| 95 | </span></p> |
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| 96 | <div class="hr"></div> |
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| 97 | |||
| 98 | <div id="communication" style="display:none;"> |
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| 99 | |||
| 100 | <h2>Bearing and Orientation Module (BOM)</h2><br/> |
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| 101 | <img src="images/sensor_BOM.jpg" /> |
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| 102 | <p>The Scout BOM provides relative localization information between robots. Four IR transmitters
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| 103 | around the base broadcast the robot's identification code and the sensor position, allowing |
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| 104 | relative orientation to be determined. The hardware is specially designed to reject environmental |
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| 105 | interference such as noise from fluorescent lights and other source of stray IR. |
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| 106 | The high refresh rate and robust communication permits tighter precision formation control over |
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| 107 | distances up to 12 feet.</p>
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| 108 | <div class="hr"></div> |
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| 109 | |||
| 110 | <h2>Wireless Network</h2> |
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| 111 | <p>Inter-robot communications are handled over a 2.4GHz Zigbee® network using the IPv6 protocol. |
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| 112 | A transfer rate of up to 2Mbps can be achieved over a distance of nearly one mile line-of-sight |
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| 113 | <span class="super">1</span>. The system uses a true layer 3 mesh network, distributing data |
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| 114 | packets intelligently amongst the robots. The nature of the mesh network is dynamically |
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| 115 | robust, self healing after the loss of any communications node.</p>
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| 116 | <div class="hr"></div> |
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| 117 | |||
| 118 | <h2>Wifi Bridge</h2> |
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| 119 | <p>An optional network bridge can link the 802.15 Zigbee® radio to standard internet |
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| 120 | enabled devices (802.11b/g). When using this bridge each Scout can be accessed wirelessly over |
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| 121 | the internet.</p>
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| 122 | <div class="hr"></div> |
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| 123 | |||
| 124 | <div id="reference-box"> |
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| 125 | <ol>
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| 126 | <li>PDF: <a href="http://www.atmel.com/dyn/resources/prod_documents/doc8111.pdf">802.15.4 Zigbee Radio</a></li> |
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| 127 | </ol>
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| 128 | </div>
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| 129 | |||
| 130 | </div><!--end 'communication' collapse--> |
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| 131 | |||
| 132 | </div>
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| 133 | |||
| 134 | <div class="white-body text-box"> |
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| 135 | <div id="bottom-nav"> |
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| 136 | <ul id="pagenav"> |
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| 137 | <li class="previous"> |
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| 138 | <a href="<?php echo $nav[$nav_id['sens']-1]; ?></a></li> |
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| 139 | <li class="next"> |
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| 140 | <a href="<?php echo $nav[$nav_id['sens']+1]; ?></a></li> |
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| 141 | </ul>
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| 142 | </div>
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| 143 | </div>
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| 144 | |||
| 145 | <div class="white-bottom"></div> |
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| 146 | |||
| 147 | </div>
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| 148 | |||
| 149 | |||
| 150 | </div>
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| 151 | </div> <!--BODY!--> |
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| 152 | |||
| 153 | |||
| 154 | <?php include("footer.php"); ?> |
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| 155 | |||
| 156 | </div><!--GENERAL!--> |
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| 157 | |||
| 158 | </body></html> |
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| 159 | <?php
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| 160 | $buffer = ob_get_contents();
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| 161 | ob_end_flush(); |
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| 162 | $fp = fopen($cacheFile, "w"); fwrite($fp, $buffer); fclose($fp); |
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| 163 | ?> |