w_smith@wookie.dec.com (Willie Smith, LTN Components Eng.) (05/14/88)
John Nagle (in a cross_posted_to_the_universe message) writes: > I'd like to hear about experience with various cameras and radio links > used with mobile robots. I'm interested in units suitable for a small, > high-speed vehicle in which the vision processing is offboard. I've been working on a teleoperated vehicle project since the beginning of the year, and while Phase I is somewhat low budget, I have made a little progress. It's based on an R/C model "Clod Buster" chassis (a 1/10 scale car crusher pickup truck) and uses a 7 channel proportional radio control, a Sony Watchcam, a TV Genii TV transmitter, and quite a few other bits and pieces and mods. > The Sony Watchcam is a low-cost alternative. Any experience here? While the CCD cameras may give better pictures, the Watchcam isn't bad. The resolution isn't the greatest, but I can navigate the vehicle without too much trouble, the size is just right, it's not too picky about power (5.1 to 15 volts at 6 watts max), and the price [$300] makes it affordable. It's small and light enough that I was able to make a pan/tilt mount for it from a couple of R/C servos. I found that the wide angle lens accessory really improved the view, so that's definately reccomended. > What about TV transmitters and receivers? I've seen a few TV Genie > units around, but not only are they weak, they're illegal. But they do > sbow that such a transmitter need not be large, and there are bands in > which one can obtain appropriate licences. I do need something > about that size, though, say 4x2x2 or smaller. Is there such a thing > as FM TV gear, to improve the noise immunity? Even with tuning [I know, tuning transmitters without a liscence is A Bad Thing, but the transmitter itself is illegal, so "in for a penny..." and all that], the TV Genii will only give a couple hundred feet range, and that's with a quarter wave antenna on a one-square-foot ground plane and the low-end Radio Shack UHF antenna on the receiver. A higher gain antenna would probably give more range, but then I'd need a rotor to keep it pointed at the vehicle. > Has anyone dealt with the problem of camera stabilization and vibration > isolation in a moving vehicle? The Steadicam gyro approach seems overkill. > Sorbothane shock mounting is easy enough to do, but is it enough to get > clear single frames? Has anyone tried using data from accelerometers > and rate gyros to stabilize an image electronically? I've slowed the vehicle way down with different motors and the smallest available pinion gears, so I can't speak of high-speed travel, but I wouldn't think you would have to worry about it. Leave room for extra camera suspension and try it without. Any kind of active suspension is going to be seriously non-trivial. > Has anyone tried sending data back from a robot in the audio carrier > of a TV signal or in the vertical retrace interval? If so, with what > hardware? I'm considering a couple of different ways for sending telemetry back from the vehicle. The easiest is to use the audio carrier of the TV Genii, but the sound seems to cut out a lot, so that might result in 'holes' in the data. The other option is another set of R/C transmitter and receiver to send the data back in the normal (pulse position encoded, sort of) R/C fashion. > Yes, I know it's a hard, ugly problem. No, the hard ugly problem is the computer interface and operator's console and HUD-analog (Amiga with genlock) and then learning to 'drive' this beast with a 3 second delay. For a low-cost vehicle (it's all lunch money so far with the exception of a donated Amiga) it works pretty well, though I'm already planning the Phase II vehicle, which will be muchly improved. I'm not too thrilled with the R/C industry in general, but it sure beats building my own or buying commercial subsystems. Phase II will probably use lawn-tractor tires, commercial gearmotors, a 'real' camera (pan/tilt/zoom/focus), a legal transmitter [I'd really appreciate any ideas on how to get liscenced for legal transmitters!], and possibly an on-board computer. Willie Smith w_smith@wookie.dec.com w_smith%wookie.dec.com@decwrl.dec.com {Usenet!Backbone}!decwrl!wookie.dec.com!w_smith