Older blog entries for cschur (starting at number 58)

Hi All,

Ive just uploaded the first main page of our new GeoBot project, a larger heavy robot designed specifically for outdoor use. Its eventual goal will be to autonomously collect rock and soil samples and return them to a starting point or home base. Here is what I have so far:

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

Comments?

Chris comets133@yahoo.com

HI All,

I want to let you in on a secret - The LM298 motor driver from Solarbotics. This kit is available for a ridiculously low price of $17, and includes all parts, connectors, and PCB, and a very well written manual for assembly and testing. I got 4 of them last week, and the first one I have put together so far worked great. You cant even buy the parts yourself for that cheap. And If you havent noticed yet, the L298 is 3- 6amps and up to 30v motor H bridge driver thats the hottest thing for robotics. I use them extensively at work, and now with the solarbotics kits, everyone can use this fine part.

The Geobot project is in full roll now, Ive put the big 16F877a processor and L298 driver board together, and am ready to mount it on a top board for the motor base, a 3 foot long dual tank tread drive, that is allready finished.

More to come...

Chris comets133@yahoo.com

Hi All,

While were waiting for some of the parts to come in for the new GeoBot project, I was trying out a prototype 4 wheel skid drive system in the house last night. The concept sounds simple enough - two close wheels per side, and drive them like a tank. When going straight, the traction is awsome, and it will climb over anything. But try to turn on a carpet and your in for a surprise! It shakes, shimmys and is very jerky and uncontrolled. Fine for a smooth tile floor or maybe outside in the sand. But on a grippy carpeted surface or maybe in your lawn it makes a mess when it turns. Just like tank treads but worse, in that the wheels are trying to drag sideways while turning. I need to try some more outside tests before condemning it.

Chris

Hi All,

I am pleased to present to you the VacBot 1 final project report, detailing our results. If you ever plan on building a vacuume robot, read this it might save you some effort! The report is here:

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

Chris

Comments? comets133@yahoo.com

This was the first big test weekend for VacBot-1 up at our cabin in the pines in northern Arizona. It showed me it has still a bit of work to get it to work as planned. First, the robot has bumper only navigation. With only that, its going to get stuck fairly often in a household enviornment. It took me a year of hard work to get PAAMI to be able to run for days in our house without ever getting stuck or trapped. She had not only bumpers, but IR Prox, and sonar and a very advanced 5 layer subsumption architecture. Vacbot has bumpers only, but is an excellent proof of concept for finding out what works and what doesnt!

While I have some more hardware mods, and am in the process of adding the 3 state FSM, here is what I have learned so far:

- when moving from tile floor to carpet, the brush assembly must keep the same height from the surface so it doesnt bog down

- Batteries last a lot longer on tile, nearly 10x longer.

- Bumper only navigation while sufficient for a square competition type arena, is not reliable for a house hold with chairs, furniture, etc.

- a speed of less than 1 foot per sec is best for effectiveness.

- there is a LOT of cat hair its picking up in our carpet!

Write me with your comments:

comets133@yahoo.com

Chris

Hi All,

I think we have it now, we redesigned our Vacbot bumper again, and now it works very well. I think you will find it a design worth using for your own:

http://www.schursastrophotography.com/robotics/vacbot2.html

Thanks for looking!

Chris

comets133@yahoo.com

HI All,

Here is the latest update with lots of new photos of our VacBot project. Take note on our adjustable bumper design we are working on:

http://www.schursastrophotography.com/robotics/vacbot1h.html

The bot is now able to autonomously navigate in the house, but the small rollers just behind the brushes are catching on things occasionally. Left to do is to put on the rear bumper and finish up the FSM in the programming to make it clean in patterns for best results. The FSM will include a spiral state, where it makes the robot move in an increasingly large spiral pattern every five minutes or so until it hits something, then go random again. this should cover the most room in a minimum amount of time.

Chris

comets133@yahoo.com

Hi everyone,

Made more progress on VacBot 1 last night, after a week of shooting the stars, I am now back to robotics in the evening because of the full moon. The bumper on this thing is unlike anything Ive ever built before. Since I am only relying on bumpers for navigation, and not IR or Sonar, They have to be rugged, and dependable. I made a metal frame work, and it hangs with rubber pads on four posts. The idea is by adjusting the bumpers, or using different materials I can get any pressure I want to activate the reed switches. Ill post some imags of this interesting concept - the adjustable bumper - comming soon!

Chris

VacBot progress:

WEll, I decieded to rip out the belt drive, and replace it with motors and a set of nylon gears. I dont think Ill ever try another belt driven system for a robot again! The problem is slippage on the pulleys, causing no end to frustration with precise maneuvers. I have two 230rmp motors left over from the PAAMI project Im going to reduce down and it will give me a precision 1ft/sec travel rate.

I finished the new book "Biorobotics" I got from robot books.com, and have some new insights on insect navigation I can use on the GeoBot project we are starting up on. Did you know that the Calipterus desert and has 20K neurons in its tiny brain? Its eyes have facets of course, but each one has a 2 degree field. Pretty coarse, but thats good enough to navigate. You dont need a megapixel sensor for a robot after all!

Chris

comets133@yahoo.com

Hi All,

More on some progress with VacBot 1, here is a new shot and a movie clip of todays work on the robot. We got rid of the direct drive to the huge 6 inch wheels, and now are trying to use a set of belt and pulleys for a 5 to 1 gear reduction. I dont know what to use for a belt yet, but for now its rubberbands. I got the speed at the half a foot per second I was targeting, and added a back wheel for the sweep height adjust.

Here is the new shot, and the movie at the top of this page:

http://www.schursastrophotography.com/robotics/vacbot1.html

The motors can now be run full speed and have huge torque.

Chris

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