TreadBot

[dragons_fire]

Here are a couple pics of the robot im working on. I do this just for fun, and for the challenge of getting it all together and working the way i want it too...


the chassis is made from 1/8" polycarbonate and 3 layers of 6oz glass cloth. the wheels are turned from 3/4" aluminum. the battery pack is a 7.4V 730mAh li-poly RCplane battery.



A better pic of the chassis construction. you can also see the hall effect sensor and the magnet in the wheel. i think i will probably add 2-3 more magnets around the wheel for more resolution.




robot with mock-up of PCB. it uses a PIC18F6585 controller, Pololu Micro Dual Serial Motor Controller, Rogue Robotics uMMC Serial Data Storage Module with 1Gig Card, memsic 2 axis accelerometer and a Paralax Ping ultrasonic sensor.


Im still adding 4-8 IR detectors for base station detection, Lynx 433MHz data transmitter, temp and air pressure sensors (just for the fun of it).

so now I need a mission for it and i cant think of anything... the memory card is going to be for mapping data, so it can remember where its been, and easily get back to any of those places. It cant climb stairs and doesnt have enough clearance for outdoor use.

if anyone has any ideas or opinions, i would be glad to hear them...

Danny

[skimask]

Put a couple of IR LEDs on the cat blipping out a signal for the rover and have it follow the cat around ALL DAY!!! Then when the batteries run down, since it's got the house mapped, it can find it's way back to the charging station where it doesn't plug into anything...it 'hovers' over a charge transfer coil (magnetic recharging?)...waits until it's recharged. When it's recharged, it looks thru its map (all the while it's been chasing the cat, it marks where the cat has been the most), goes to the spot or area where the cat usually hangs out and then POUNCES on the cat!

[dragons_fire]

HAHA!!! thats a great idea... Exactly the kind of ideas im looking for... Only probelm is that i dont have a cat (and dont want one), and the dog sleeps on hte couch all day where this thing cant get too...

the mapping idea is just for the challenge of trying it, but im still debating my method of using the revolutions to tell how far its gone.. the room (the main floor of the house) has linoleum, hardwood and a couple rugs.. i can almost guarantee its going to slide trying to go from one to the other.. it looks like i may need to add a compass into it somehow, or add IR transmitters on different frequencies around the room, and have the robot detect them and figure out where it is...

im curious as to what other people think about what it can do, or how to figure out where it is...

[dragons_fire]

we also have the western canada robot games being held in my city, so i was thinking about making it for the minesweeper competition. its a great idea, but i dont think i could have it ready by the competition this year, and i dont want to build it just to wait until next year...

[skimask]

the mapping idea is just for the challenge of trying it, but im still debating my method of using the revolutions to tell how far its gone.. the room (the main floor of the house) has linoleum, hardwood and a couple rugs.. i can almost guarantee its going to slide trying to go from one to the other.. it looks like i may need to add a compass into it somehow, or add IR transmitters on different frequencies around the room, and have the robot detect them and figure out where it is...

im curious as to what other people think about what it can do, or how to figure out where it is...

Mapping - are you using stepper motors or regular 'just add volts and it spins' motors? Regular motors - good luck getting them to spin EXACTLY the same speed to go straight! Not saying it's impossible, but it'll be tough without good electronics. And what happens when the treads slip on the floor? The 'bot could think it's moving forward, when it's actually getting nowhere. Keep an eye on current draw could help with that. Motor draws X current, it's moving normally, motor draws 2X current, tracks are probably hanging up, motor draws .5X current, tracks are probably slipping like they're on ice.

Compass - magnetic compass 'could' work. How about an RF/IR link? A master RF TX sends out a pulse at X intervals, say 10 seconds. 1 second later, an IR LED on wall X1 pulses, 1 second later, an IR LED on wall X2 pulses, and so on and so on. The 'bot 'hears' the master pulse and starts looking for IR pulses. Depending on which IR sensor sees it and at what time, it can figure out which way it's pointing, limited accuracy of course.

[dragons_fire]

the motors are just regular brushed motors, they have a gear ratio of 298:1 which equals out to 71RPM and 30oz/in of torque. im using a serial dual motor controller, and with the hall sensors, i should be able to adjust the motors to get it to move straight forward...

my big issue, is that it will turn better on shiny hardwood, than it will on carpet, so if i tell it to turn 90*, it will turn 95* on wood, and 80* on carpet.. what i was thinking with the IR link, was to have 3 transmitters around the room, and then have 16 (or more) sensors around the top of the bot, and it could somewhat triangulate where it is by the angles to all 3 transmitters. it could do that maybe every 5 minutes, just to make sure its where its supposed to be...

[skimask]

the motors are just regular brushed motors, they have a gear ratio of 298:1 which equals out to 71RPM and 30oz/in of torque. im using a serial dual motor controller, and with the hall sensors, i should be able to adjust the motors to get it to move straight forward...

my big issue, is that it will turn better on shiny hardwood, than it will on carpet, so if i tell it to turn 90*, it will turn 95* on wood, and 80* on carpet.. what i was thinking with the IR link, was to have 3 transmitters around the room, and then have 16 (or more) sensors around the top of the bot, and it could somewhat triangulate where it is by the angles to all 3 transmitters. it could do that maybe every 5 minutes, just to make sure its where its supposed to be...

Motors - That kind of gear ratio sounds a bunch better than direct drive. Should be able to keep track of that fairly well.

Turning/mapping/whatever - too bad a guy couldn't 'easily' add a circuit like an optical mouse. Ya get 2 of those, one at the front in the middle, one at the back in the middle, you can do some math to figure out how far the 'bot actually turned.

This could turn out to be a lllooonnnggg thread...