colonymech / docs / www / colonyscout / sensors.php @ f59acf11
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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 | <div id="sensor" style="display:none;"> |
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44 | |||
45 | <h2>Environment Mapping</h2> |
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46 | <p>Ultrasonic ranging sweeps 360 degrees around each Scout robot, providing up to 48
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47 | measurements per cycle. A compact stepper motor provides precise and rapid position control. The high resolution and |
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48 | fast scanning speed are appropriate for 2D mapping and navigation.</p>
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49 | <p>The Maxbotix® EZ™ line of sonar rangefinders was chosen for their proven accuracy and |
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50 | long term reliability<span class="super">2</span>. The EZ4 provides the narrowest sensing |
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51 | area of the EZ™ family, allowing higher precision maps to be produced, while still
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52 | providing wide coverage for obstacle detection.</p>
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53 | <div class="hr"></div> |
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54 | |||
55 | <h2>Cliff Detection</h2> |
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56 | <p>A trio of short range Sharp® IR rangefinders provide early warning of sharp drop-offs that |
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57 | could compromise the robot's mission.</p>
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58 | <div class="hr"></div> |
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59 | |||
60 | <h2>Odometry & Vehicle Dynamics</h2> |
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61 | <p>Vehicle position is tracked by quadrature encoders on each wheel resulting in 3mm linear accuracy
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62 | <span class="super">3</span>. A custom IMU (inertial measurement unit) consisting of a 3-axis accelerometer |
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63 | and pitch+yaw-rate gyroscope provide detail of the vehicle's motion in three dimensions. |
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64 | </p>
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65 | <div class="hr"></div> |
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66 | |||
67 | <h2>Complementary Sensing</h2> |
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68 | <p>The sonar rangefinders are optionally supplemented by short range LED reflectance sensors for close wall
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69 | following. Dual sensors on the front bumper provide resolved impact detection for escape manuevers or |
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70 | when manipulating objects. |
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71 | </p>
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72 | <div class="hr"></div> |
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73 | |||
74 | <div id="reference-box"> |
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75 | <ol>
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76 | <li>Comparison with commercially available robots valued at <$500 USD.</li> |
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77 | <li>PDF: <a href="http://www.maxbotix.com/uploads/Pendulum_Test_Results.pdf">Maxbotix® EZ4™ Sensor Testing</a></li> |
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78 | <li>48 clicks per revolution, 42mm diameter wheel. (42mm*pi)/48=2.7488mm</li> |
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79 | </ol>
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80 | </div>
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81 | |||
82 | </div><!--end 'sensor' collapse--> |
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83 | </div>
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84 | |||
85 | <div class="white-body text-box"> |
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86 | <a href="javascript:;" title="Click to Expand" onmousedown="toggleDiv('communication');"> |
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87 | <h1>Communications</h1><img src="images/btn_expand.png" /></a> |
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88 | <p><span class="description">Scout communicates over several protocols, providing a robust interface |
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89 | over long distances. Inter-robot communications and control commands are broadcast over a self organizing |
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90 | high bandwidth mesh network. The robots also broadcast over IR (infrared light) for localization. |
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91 | <br/><br/><a href="javascript:;" onmousedown="toggleDiv('communication');"><em>learn more >></em></a> |
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92 | </span></p> |
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93 | <div class="hr"></div> |
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94 | |||
95 | <div id="communication" style="display:none;"> |
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96 | |||
97 | <h2>Bearing and Orientation Module (BOM)</h2><br/> |
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98 | <img src="images/sensor_BOM.jpg" /> |
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99 | <p>The Scout BOM provides relative localization information between robots. Four IR transmitters
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100 | around the base broadcast the robot's identification code and the sensor position, allowing |
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101 | relative orientation to be determined. The hardware is specially designed to reject environmental |
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102 | interference such as noise from fluorescent lights and other source of stray IR. |
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103 | The high refresh rate and robust communication permits tighter precision formation control over |
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104 | distances up to 12 feet.</p>
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105 | <div class="hr"></div> |
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106 | |||
107 | <h2>Wireless Network</h2> |
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108 | <p>Inter-robot communications are handled over a 2.4GHz Zigbee® network using the IPv6 protocol. |
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109 | A transfer rate of up to 2Mbps can be achieved over a distance of nearly one mile line-of-sight |
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110 | <span class="super">1</span>. The system uses a true layer 3 mesh network, distributing data |
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111 | packets intelligently amongst the robots. The nature of the mesh network is dynamically |
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112 | robust, self healing after the loss of any communications node.</p>
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113 | <div class="hr"></div> |
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114 | |||
115 | <h2>Wifi Bridge</h2> |
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116 | <p>An optional network bridge can link the 802.15 Zigbee® radio to standard internet |
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117 | enabled devices (802.11b/g). When using this bridge each Scout can be accessed wirelessly over |
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118 | the internet.</p>
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119 | <div class="hr"></div> |
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120 | |||
121 | <div id="reference-box"> |
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122 | <ol>
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123 | <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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124 | </ol>
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125 | </div>
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126 | |||
127 | </div><!--end 'communication' collapse--> |
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128 | |||
129 | </div>
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130 | |||
131 | <div class="white-body text-box"> |
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132 | <div id="bottom-nav"> |
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133 | <ul id="pagenav"> |
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134 | <li class="previous"> |
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135 | <a href="<?php echo $nav[$nav_id['sens']-1]; ?></a></li> |
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136 | <li class="next"> |
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137 | <a href="<?php echo $nav[$nav_id['sens']+1]; ?></a></li> |
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138 | </ul>
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139 | </div>
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140 | </div>
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141 | |||
142 | <div class="white-bottom"></div> |
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143 | |||
144 | </div>
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145 | |||
146 | |||
147 | </div>
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148 | </div> <!--BODY!--> |
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149 | |||
150 | |||
151 | <?php include("footer.php"); ?> |
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152 | |||
153 | </div><!--GENERAL!--> |
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154 | |||
155 | </body></html> |
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156 | <?php
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157 | $buffer = ob_get_contents();
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158 | ob_end_flush(); |
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159 | $fp = fopen($cacheFile, "w"); fwrite($fp, $buffer); fclose($fp); |
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160 | ?> |