Paradroid

Index Photo: 
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Paradroid attains an unparalleled level of modularity and extendibility compared to competing vehicle
platforms. The mechanical design of Paradroid is based on a sturdy four-wheeled platform that can accommodate a
large variety of modules. This four wheel drive platform features two custom built omni-directional wheels to
maximize turning efficiency and minimize rolling resistance and vibrations. Sensors and processing power are
connected to the drive platform via detachable interfaces, allowing the robot to be easily configured for specialized
tasks. This approach maximizes the expandability of the platform. Each compartment is accessible simultaneously,
facilitating testing and debugging of various systems. Paradroid also includes independent shock absorbers on each
of its four wheels to allow for smoother operation and maximum traction on rough terrain. Powerful wheelchair
motors make Paradroid capable of maintaining 5 mph speed even on moderate inclines.
Paradroid also incorporates a number of power and embedded control innovations. Using an advanced
motor controller, the Roboteq AX3500, Paradroid can achieve extremely tight speed control and utilizes
regenerative braking to increase overall vehicle efficiency. The robust power system was custom made to efficiently
power (85% nominal) the various embedded systems in a small package. This makes Paradroid's power system
adaptable to platforms with different operational voltages from 8 to 30V. A power monitoring system dynamically
estimates current power capacity and remaining runtime during vehicle operation. While charging, the E-stop is
automatically engaged to allow safe testing of other components without danger of the vehicle moving. A
commercial off-the-shelf Atmel development board forms the core of the embedded system, allowing for a
substantial amount of processing to be done at the embedded level. This relieves the main computer of low level
tasks like dead reckoning and sensor interfacing. The embedded system also calculates the vehicle's global position
allowing the robot to be driven manually without any additional computing power on-board. An adaptive odometry
algorithm was implemented utilizing yaw rate and GPS sensors to give better global position accuracy without the
cost of a much more expensive differential GPS system.
Paradroid's sensors were chosen for versatility and cost effectiveness. A stereovision system provides a
complete solution for both depth perception and line detection. This option is more cost effective than a laser range
finder and camera combination. The stereo-vision camera retails at $1800, while a laser range finder and camera
combination would have cost approximately $5200. Also, the stereovision camera system makes Paradroid better
suited for stealth-based applications than a laser range finder because it is a passive sensor.
Paradroid is equipped with an entirely new software package based on the open source CARMEN
framework. The modularity of CARMEN allows the robot to be easily configured to incorporate data from a variety
of sensors. Furthermore, the CARMEN package comes equipped with many common drivers, which allowed the software team to focus on high level concepts rather than low level integration problems. Paradroid uses
Simultaneous Localization And Mapping (SLAM) algorithms to plan its course, a feat that the team has never
attempted before. It adds sensory data to an environmental map and then uses this information to find the optimal
path to the objective. Probability based localization algorithms correct for accumulated error in odometry data to
prevent this error from invalidating the map. 
The new software package also features a graphical user interface designed to be viewed over WiFi from
any secure computer. This allows for remote testing and calibration as well as multiple connected operators. The
GUI displays sensory data, system status, video streams and mapping information in real-time, allowing for truly
remote operation. Lastly, the robot is JAUS Level 2 compatible, meaning that communications are performed over a
standard military protocol. This adds to the modularity and reusability of the design and provides a means for
communication with other JAUS compatible devices such as remote operator controller units. Our software goes
beyond the requirements of IGVC's Level 3 JAUS Challenge by using tele-operation commands and implementing
controller authorization policies to prevent multiple nodes from sending conflicting commands.