MJB@cup.portal.com (Martin J Brown-Jr) (03/13/89)
I need a system that measures distances for some homebrew robotics projects.
Though I don't have the specs on hand, as I recall, the Polaroid "system"
doesn't measure down to the 1/8th of an inch, and it has a "large" frontal
area to boot. I would like to be able to measure to an 1/8th of an inch
accuracy or greater, over a distance of 1/4" (or so) to 30 feet. Also, and
more importantly, to have it be a narrow beam (1/4"?) width spread at the
maximum distance. This is so that I will be able to get ranges at specific
spots, and to be able to "see" smaller than wall size objects. All of the
above measurements are rough, but hopefully, indicative of what I would
like to achieve. Lastly, is the price of such accuracy within the realm
of a homebrew project? $500-$1000?
Thanx!
- MJB -skohls@uceng.UC.EDU (steve kohls) (03/21/89)
In article <15792@cup.portal.com> MJB@cup.portal.com (Martin J Brown-Jr) writes: >I need a system that measures distances for some homebrew robotics projects. >I would like to be able to measure to an 1/8th of an inch >accuracy or greater, over a distance of 1/4" (or so) to 30 feet. Also, and >more importantly, to have it be a narrow beam (1/4"?) width spread at the >maximum distance. This is so that I will be able to get ranges at specific >spots, and to be able to "see" smaller than wall size objects. One way to achieve a smaller effective beam width is through a process known as "beam splitting". In order to effectively narrow the beam spread, multiple sonar transducers are used, and their beams are overlapped. Distance measurements are taken sequentially from each transducer and compared to one another. If the distances are all within a certain tolerance of each other, an object is presumed to be in the area where the beams overlap. I believe this is how the process works. I have read a number of papers on mobile robotics where beam splitting is used and the above is what I have gleaned from them. A good source of info is the _IEEE Journal of Robotics and Automation_ (pay special attention to the research being done at CMU). Another way to get the accuracy and beam width you want is to use narrow beam sonar transducers available from various manufacturers. (Can't recall where I saw these right now). Also, don't forget to correct for air temperature when making sonar measurements. I don't have the correction formula with me, but let me know if there is interest, and I will post it or mail it. I'm working on a mobile robot project of my own at home also. Currently I am designing the sensor head of the robot and I am working on a beam splitting arrangement using Polaroid transducers. I would like to see more discussion on robotics here, also feel free to E-mail me. Steve Steve Kohls skohls@uceng.UUCP