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Wed, 01 Mar 2006
understanding the SRV-1 sensors
The current SRV-1 controller includes 2 primary sensors - the digital camera module, and an array of 4 infrared emitter/detector pairs. The digital camera was always a key portion of the design, both for internet-based telepresence as well as for image processing on the robot itself for object detection, object tracking, and autonomous navigation.
Beyond on-board image processing, we wanted to add some low-cost sensors to help the robot in deriving its orientation and position, and we experimented with a variety, including a digital compass and several ultrasonic ranging modules. We eventually abandoned these, as the compass was subject to many magnetic field disturbances when operating indoors (not the least of which were the robot motors), and the ultrasonic ranging was of limited value without a frame of reference for orientation. Also, the ultrasound modules were highly prone to false triggers when the robot was moving, and the ability to actually resolve specific objects was quite limited.
We decided to take a different path, focusing instead on developing firmware that would help the robot navigate primarily by visual cues, much the way a human navigates, but provide the possibility of an external reference frame using easily deployed infrared beacons. In the process of testing this concept, we realized that there would be several benefits from the addition of the infrared components, as one SRV-1 robot could itself act as a beacon, which would be useful for coordinating the movement of multiple other robots. Also, the SRV-1's could use infrared to communicate with each other at close range (albeit low data rate - 1000 baud at best), and the infrared components could operate as proximity sensors for collision avoidance. Though software still has to be developed to take full advantage of these possibilities, the addition of about $5 worth of components offers the potential for significant functionality.
Beyond this, we have provided connections from the ARM7 processor board for other external sensors, but for now, our main software development focus will be on taking maximum advantage of the vision and infrared sensors provided on this version of the SRV-1 controller.
Posted Wed, 01 Mar 2006 10:40 | HTML Link | see additional stories ...