root / docs / www / colonyscout / sensors.php @ 781890a0
History | View | Annotate | Download (7.25 KB)
1 |
<?php
|
---|---|
2 |
$cacheFile="cache/sensors.html"; |
3 |
if (file_exists($cacheFile)) //we can read this cache file back reduce database load |
4 |
{ |
5 |
header("Content-Type: text/html"); |
6 |
readfile($cacheFile); |
7 |
exit;
|
8 |
} else {
|
9 |
ob_start(); //start buffering so we can cache for future accesses
|
10 |
} |
11 |
?>
|
12 |
|
13 |
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
14 |
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head> |
15 |
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"/> |
16 |
<meta name="description" content="Scout fuses sonar with IR sensors to provide realtime feedback about the robots' environment."/> |
17 |
<meta name="keywords" content="sonar, ir, sharp, COTS, Scout, feedback, control system, maxbotix"/> |
18 |
|
19 |
<?php include("header.php"); ?> |
20 |
<title>Sensors | ColonyScout.com</title> |
21 |
|
22 |
</head>
|
23 |
<body bgcolor="#eeeeee"> |
24 |
|
25 |
<div id="general"> |
26 |
<?php include("nav.php"); ?> |
27 |
<div id="body"> |
28 |
<div id="body-boxes"> |
29 |
<div class="box-row"> |
30 |
<div class="white-top"></div> |
31 |
<div class="white-body text-box"> |
32 |
<a href="javascript:;" title="Click to Expand" onmousedown="toggleDiv('sensor');"> |
33 |
<h1>Sensor Fusion</h1><img src="images/btn_expand.png" /></a> |
34 |
<p class="description">The Scout sensor suite affords increased situational awareness over comparably |
35 |
priced platforms<span class="super">1</span>. Scout fuses long range sonar with short |
36 |
range IR sensors and LED reflectance sensors to provide realtime feedback about the robots' |
37 |
environment. Commercially available off-the-shelf components were used where possible, |
38 |
selected based on range, accuracy, and repeatability characteristics. |
39 |
<br/><br/><a href="javascript:;" onmousedown="toggleDiv('sensor');"><em>learn more >></em></a> |
40 |
</p>
|
41 |
<div class="hr"></div> |
42 |
|
43 |
<div id="sensor"> |
44 |
|
45 |
<h2>Environment Mapping</h2> |
46 |
<img src="/images/sensors_sonar.jpg" style="float:left;margin:0px 10px 10px 0px;"> |
47 |
<p>Ultrasonic ranging sweeps 360 degrees around each Scout robot, providing up to 48
|
48 |
measurements per cycle. A compact stepper motor provides precise and rapid position control. The high resolution and |
49 |
fast scanning speed are appropriate for 2D mapping and navigation.</p>
|
50 |
<p>The Maxbotix® EZ™ line of sonar rangefinders was chosen for their proven accuracy and |
51 |
long term reliability<span class="super">2</span>. The EZ4 provides the narrowest sensing |
52 |
area of the EZ™ family, allowing higher precision maps to be produced, while still
|
53 |
providing wide coverage for obstacle detection.</p>
|
54 |
<div class="hr" style="clear:both;"></div> |
55 |
|
56 |
<h2>Cliff Detection</h2> |
57 |
<img src="/images/sensors_cliff.jpg" style="float:left;margin:0px 10px 10px 0px;"> |
58 |
<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>
|
60 |
<div class="hr" style="clear:both;"></div> |
61 |
|
62 |
<h2>Odometry & Vehicle Dynamics</h2> |
63 |
<img src="/images/sensors_imu.jpg" style="float:left;margin:0px 10px 10px 0px;"> |
64 |
<p>Vehicle position is tracked by quadrature encoders on each wheel resulting in 3mm linear accuracy
|
65 |
<span class="super">3</span>. A custom IMU (inertial measurement unit) consisting of a 3-axis accelerometer |
66 |
and pitch+yaw-rate gyroscope provide detail of the vehicle's motion in three dimensions. |
67 |
</p>
|
68 |
<div class="hr" style="clear:both;"></div> |
69 |
|
70 |
<h2>Complementary Sensing</h2> |
71 |
<p>The sonar rangefinders are optionally supplemented by short range LED reflectance sensors for close wall
|
72 |
following. A sensor on the front bumper provides resolved impact detection for escape manuevers or |
73 |
when manipulating objects. |
74 |
</p>
|
75 |
<div class="hr"></div> |
76 |
|
77 |
<div id="reference-box"> |
78 |
<ol>
|
79 |
<li>Comparison with commercially available robots valued at <$500 USD.</li> |
80 |
<li>PDF: <a href="http://www.maxbotix.com/uploads/Pendulum_Test_Results.pdf">Maxbotix® EZ4™ Sensor Testing</a></li> |
81 |
<li>48 clicks per revolution, 42mm diameter wheel. (42mm*pi)/48=2.7488mm</li> |
82 |
</ol>
|
83 |
</div>
|
84 |
|
85 |
</div><!--end 'sensor' collapse--> |
86 |
</div>
|
87 |
|
88 |
<div class="white-body text-box"> |
89 |
<a href="javascript:;" title="Click to Expand" onmousedown="toggleDiv('communication');"> |
90 |
<h1>Communications</h1><img src="images/btn_expand.png" /></a> |
91 |
<p><span class="description">Scout communicates over several protocols, providing a robust interface |
92 |
over long distances. Inter-robot communications and control commands are broadcast over a self organizing |
93 |
high bandwidth mesh network. The robots also broadcast over IR (infrared light) for localization. |
94 |
<br/><br/><a href="javascript:;" onmousedown="toggleDiv('communication');"><em>learn more >></em></a> |
95 |
</span></p> |
96 |
<div class="hr"></div> |
97 |
|
98 |
<div id="communication" style="display:none;"> |
99 |
|
100 |
<h2>Bearing and Orientation Module (BOM)</h2><br/> |
101 |
<img src="images/sensor_BOM.jpg" /> |
102 |
<p>The Scout BOM provides relative localization information between robots. Four IR transmitters
|
103 |
around the base broadcast the robot's identification code and the sensor position, allowing |
104 |
relative orientation to be determined. The hardware is specially designed to reject environmental |
105 |
interference such as noise from fluorescent lights and other source of stray IR. |
106 |
The high refresh rate and robust communication permits tighter precision formation control over |
107 |
distances up to 12 feet.</p>
|
108 |
<div class="hr"></div> |
109 |
|
110 |
<h2>Wireless Network</h2> |
111 |
<p>Inter-robot communications are handled over a 2.4GHz Zigbee® network using the IPv6 protocol. |
112 |
A transfer rate of up to 2Mbps can be achieved over a distance of nearly one mile line-of-sight |
113 |
<span class="super">1</span>. The system uses a true layer 3 mesh network, distributing data |
114 |
packets intelligently amongst the robots. The nature of the mesh network is dynamically |
115 |
robust, self healing after the loss of any communications node.</p>
|
116 |
<div class="hr"></div> |
117 |
|
118 |
<h2>Wifi Bridge</h2> |
119 |
<p>An optional network bridge can link the 802.15 Zigbee® radio to standard internet |
120 |
enabled devices (802.11b/g). When using this bridge each Scout can be accessed wirelessly over |
121 |
the internet.</p>
|
122 |
<div class="hr"></div> |
123 |
|
124 |
<div id="reference-box"> |
125 |
<ol>
|
126 |
<li>PDF: <a href="http://www.atmel.com/dyn/resources/prod_documents/doc8111.pdf">802.15.4 Zigbee Radio</a></li> |
127 |
</ol>
|
128 |
</div>
|
129 |
|
130 |
</div><!--end 'communication' collapse--> |
131 |
|
132 |
</div>
|
133 |
|
134 |
<div class="white-body text-box"> |
135 |
<div id="bottom-nav"> |
136 |
<ul id="pagenav"> |
137 |
<li class="previous"> |
138 |
<a href="<?php echo $nav[$nav_id['sens']-1]; ?></a></li> |
139 |
<li class="next"> |
140 |
<a href="<?php echo $nav[$nav_id['sens']+1]; ?></a></li> |
141 |
</ul>
|
142 |
</div>
|
143 |
</div>
|
144 |
|
145 |
<div class="white-bottom"></div> |
146 |
|
147 |
</div>
|
148 |
|
149 |
|
150 |
</div>
|
151 |
</div> <!--BODY!--> |
152 |
|
153 |
|
154 |
<?php include("footer.php"); ?> |
155 |
|
156 |
</div><!--GENERAL!--> |
157 |
|
158 |
</body></html> |
159 |
<?php
|
160 |
$buffer = ob_get_contents();
|
161 |
ob_end_flush(); |
162 |
$fp = fopen($cacheFile, "w"); fwrite($fp, $buffer); fclose($fp); |
163 |
?>
|