Older blog entries for cschur (starting at number 79)

Hi all,

were working on a series of small table top robots now, to develop in sections the various levels of subsumption architecture, one level at a time. I am doing this piece meal, to eventually develop a superior home cleaning robot. First, we are tackling the impact level, with bumpers and a new design for a plate style bumper. First I am working on a one chip per servo driver, using a PIC12f629, an under a buck processor to take serial data from the main processor and control a single servo. Ill of corse share it with all of you when we get it perfected, and you can have both the schematic and software ready to burn for your own servo drivers.

Chris

10 Aug 2006 (updated 10 Aug 2006 at 15:19 UTC) »

HI all,

Ok, well were finally finished with the Geobot project, and I would like to present to you the Final Report:

www.schursastrophotography.com/robotics/geobotfinal.html

There can be no doubt that the technologies we have gained much experience in on this project will be a great foundation for future out door robotics projects for us in the comming days.

Chris

comets133@yahoo.com

Hi all,

We have made another significant milestone in the progress of the Geobot, the rock collecting robot. The arm, motorized scoop, and ground detect sensors are done. We connected the interface to the processor tonight, and were able to move the arm smoothly, turn on the motorized rock scoop, and yes even detect the ground with contact switches. Our next step is to actually program the Finite state machine that will do the actual rock aqusition, stow the arm, and return the sample to home! This is certainly the most sophisticated robotic arm we have constructed yet. On my main page, Ive posted a new shot a few minutes ago of the geobot with its scoop arm raised:

http://www.schursastrophotography.com/roboticsmain.html

Note the new "Schurs Artificial intelligence Scale" at the top of the page too...

Chris

comets133@yahoo.com

17 Jul 2006 (updated 17 Jul 2006 at 03:48 UTC) »

Hi all,

Now that we are back from Australia, we are making good progress once again on the Geobot. The motorized power rock scoop is coming together fairly well, and a quick test in the back yard shows that it really does collect small rocks very well. So here is where we are at right now, and a movie of the robot performing its eventual rock collecting mission (without arm yet) in a street test.

www.schursastrophotography.com/robotics/rockscoop1.html

Chris

11 Jul 2006 (updated 11 Jul 2006 at 18:28 UTC) »

Hi all,

Just got back from 2 weeks in Queensland Australia, diggin dinosaurs and doing some astronomy. Time to get back to the Geobot. I finally found a brush to use for my rock scoop. Its a ceramic core, with stiff nylon fibers used for a hair brush. I cut a 2 inch wide section out of it, and am currently mounting the motor to it. This will be lowered by the new arm we installed 2 weeks ago to the ground, and turned on when it touches the ground. A wire mesh cup will catch the spray of material that comes from the brush, including small rocks and pebbles.

So we have the new arm working fine, the robot is turning around at its destination which is 100 feet for now, and returns very nearly to where it started just fine. The brush collection assembly is the last part to put on, but its not so easy to make!

I keep asking myself where Im going to store this huge robot after we accomplish our goal of rock collection...

Write me,

Chris comets133@yahoo.com

Here is a progress report on the Geobot. The devantech compass is finally working, the unit we got simply would not calibrate for blood or money. We rotated it in the cal mode over and over, but the cal done lamp would not change. Finally, in desparation, we calibrated it using the old style previous rev software version method. It worked. Apparently, we got an unmarked chip, which was not the newest version.

Anyway, The robot now goes out a preset distance, rotates 180, and returns very near the start position. We are ready to add the arm now, that will collect the rock samples from the remote location and return with them.

So two problems we encountered this week are first, the tank base I used (Stuart M5) doesnt have the power to rotate in place on 3 inch deep grass. We stick to rocky flats for now. Second, the motors genrate a horrendous magnetic field from the magnets inside them, which cause up to 20 degree offsets at certain angles from the real bearing!

WEll, other than mount the darn compass on a six foot pole, Im going to try to keep missions on the NS - EW line for now, thats where the compass is calibrated to be dead on. Alternately, I can make some sort of look up table for each angle as to what angle really is 180 degrees so It turns around at its destination for the return trip.

The final goal of course will be to send the robot on a rocky gravely plain (common here in Arizona) out to 100 foot distance, collect surface specimens with a motorized scoop with a rotating brush on the end, and return them to the start point.

The project page for the Geobot is at:

http://www.schursastrophotography.com/robotics/geobot_mainpa ge.html

Write me if you have time! chris

comets133@yahoo.com

Hi all,

After three grueling weeks of testing, design and calibration, we have finished the first phase of compass integration into the Geobot. I have put an article together complete with photos, diagrams, schematics, and mpg movies with sound of our recent efforts. We are one step away from getting the robot to go to a destination and return to home autonomously. Here is our latest article:

http://www.schursastrophotography.com/robotics/compass1.html

Comments?

Chris comets133@yahoo.com

I got our compass working now on the Geobot. Its a bit tricky to deal with the numerical roll over from 359 to 1 degrees but I found a simple solution. Anyway, the robot takes a bearing upon turn on, and maintains it within about 2 degrees tolerance as it pounds its way across the rocks in our testing area. Its the damndest thing - I set the robot down, and it swerves around avoiding rocks and such, then turns toward the original bearing when its not hitting something! Very cool to watch.

I did run into one issue with the Devantech compass, it would not calibrate per instructions. I kept on rotating it and the done line never went high. I finall in desparation used the old cal proceedure with 4 points at 90d, and that worked. Id be intersted if anyone had a similar problem with thier compass?

Write me: comets133@yahoo.com

Chris

HI All,

Well, here it is as promised, the write up on shaping and final testing of our quadrate sonar array on the Geobot. I think we have learned more about sonar in the past few weeks than in my entire life:

http://www.schursastrophotography.com/robotics/sonarshld1.ht ml

Write me!

Chris comets133@yahoo.com

More on Outdoor Sonar....

We have spent many more hours this week on getting our quad sonar array to work outdoors. I have discovered a very useful fact about doing this, Id like to share. With a sonar mounted just above ground level, say six inches or so, you will be detecting the ground at some point a few feet away, and it will change rapidly in some cases from a foot to over four feet in a heartbeat.

We tried aiming the sonar upward about 25 degrees which pushed the ground detect point outward only slightly, but now it was picking up beams on the overhanging roof! So dont point your sonar upward.

This "ground effect" requires you to do one of two things to make the sonar useful for obstacle detection. First, you can always jack it up a foot or so off the ground. Then youll miss some pretty major obstacles, but your ground detect point will move out to past the detection limit of about 8 feet for the SR04 sonar.

Alternately, we can try to reshape the beam. Research into this on the web has shown mainly failed attempts, the general consensus is you CANT change it. Well, we found thats not entirely true!

You cant add like tubes or cones in front of the beam or over the emitter/detector because it just sees the tube and its signal overwhelms the detector. BUT you can modify the pattern by reflection. Here we put a smooth surface for the beam to deflect off of, exactly like a mirror. By intelligently putting a flat piece of lexan under the sonar xmitter, we can deflect the sound waves that would hit the ground up into the air. so now we are determinng the shape of that flat plate, and how big it should be. Im guess ing it will be D shaped, and about four to six inches radius.

More to come, working with a sensor system that literally sprays signal all over the place outdoors is quite the challenge!

Write me if you have any suggestions.

Chris

comets133@yahoo.com

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