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segway style robots

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jailsellgren:
Hi,

I've recently joined the forum and am looking to build a balancing robot. A tall, lightweight, 2 wheeled balancing robot like the segway. Not very big either. Around 2-3 feet tall and a maybe 8 by 8 inch base(like the shadow below it)

So im going to ask for most of the parts for christmas. So from what i understand i need  ( please make reccomendations and comments, i am new to this and would just like to get all tha parts i need so i can then begin working on it after xmas)

Battery                        rc battery pack? how many volts and how much (mah?) or something
Gyro and Accelerometer          i read about something like this and a kalman filter, will i be able to achieve this, give me your best reccomendation

Wheels and body and other body parts                          where do i buy?
Motors                     dc brushless    i have no idea here so point me to some options  heres one i looked at but i have to build this thing  and i dont know that i would be able to program and use it correctly  http://www.geology.smu.edu/~dpa-www/robo/Encoder/pitt_html/encoders.html

Motor Controller?   if its brushless i guess i need one, what if its not brushless,  please help here
Microcontroller         a 10$ atmel?  i dont know it needs to run fast to be able to do the balancing algorithm many times a second so that it does not fall over     do i have to have another chip to do the balancing so as not to slow everything else down?

I need pretty much a good parts list and places to buy things. Any helps would be greatly appreciated
anything i forgot or that can point me in the right direction would be great

here is an example of what i want to build  http://balbots.com/


thank you so much in advance you guys rock

erik :D

Admin:
hi jailsellgren

i believe one or two other people on SoR is also interested in building a segway-like robot. search the forum for 'segway,' you might be able to help each other.

so i have never built one myself, but i might be able to help you along some . . . check the robot parts list page to find everything you need to buy. if you cant find what you want, let me know.

for battery, choose a NiMH type, rated between 6V and 8V. you will want at least 1000mAh, which will probably give your bot about 1 to 2 hours of continuous runtime. ~$15

as for sensors, we discussed sensors on this post
http://www.societyofrobots.com/robotforum/index.php?topic=241.0

so you will probably need two encoders (can be homemade for like $3/each), an accelerometer (~$20), and a gyro (~$40). I believe they now have gyro IC's for cheap, but I have never used one so cant really help you there . . . control programming will be a little hard for a beginner, just let us know when you have it built and we can help you with that.

chassis parts will cost you around ~$30, frame material and wheels. i recommend using HDPE. 1/8th" should be fine. its really cheap, just buy a lot of extra in case you mess up.

for motors (~$30 each), only use geared types. get one with a rating of about 6V. im not really sure what torque you might need . . . 1 pound-foot sounds decent. if you arent sure, always opt for higher torque than you think you need. !!! anyone know how to calculate torque for segway bots? its dynamic so its tricky . . .

for motor controller, you want a dual driver (handles two motors) that does at least 12V and at least 2A continuous. ~$70

microcontroller, depends on your experience. if you are a beginner, i recommend buying something pre-assembled and simple ~$40. or a development board ~$20 if you dont mind being occasionally frustrated and lost. in the long term the development board route will be better.

if you have more questions, feel free to ask.

jailsellgren:
Ok so, to the admin or any other well experienced ..roboticist..?

Here are 2 batteries, which should i pick if any
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1366
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=495

I decided for an encoder to use the sharp ir range finder since its pre assembled, i could make one but it would be hard to get it to always sit right.  if anyone could give me a link to the right one (link to a store) that i need it would be great, i found a couple versions of it.

For microcontroller, right now i have a boe-bot with a bs2 stamp that i have learned to program, what exact microcontroller would you reccomend for the job, point me to a couple of reccomendations with links.  I dont mind the complexity, thats what makes it fun.

I found some gyros and accelerometers, could you point me to some options around the prices you mentioned. I foun some pretty fancy stuff but it was way too expensive. (rotomotion.com) anyways this seems to be the most puzzling piece of the project to me so if anyone could tell me about this all and the "kalman filters" that would help a lot     i found a page with 1 acceleromter and gyro but i dont know what i need in conjunction with that and if these are even the right or accurate enough for my use
http://www.junun.org/MarkIII/Store.jsp
do i need a seperate processer to run and calculate these things

For base i will take your suggestion and use hdpe, but im bad at designign this, how do i mount these round dc motors to a sheet of plastic. Il let you tell me after you see my motor ideas.

For motors i suppose you meant that i dont need brushless so here are some things i found, tell me what you think.
what rpm and ratio of gear should i have, i got these picks from robot marketplace.com
http://www.robotmarketplace.com/marketplace_motorsmisc.html  On this page the ml 30 or the ml 50
theres also all the gearhead motors on this page
http://www.robotstore.com/store/Default.asp?catid=1565&page=1
out of all of these which would you reccomend

Heres a motor controller i found, suitable?
http://www.lynxmotion.com/Product.aspx?productID=92&CategoryID=10


I know your reply will take time and thought and i really really appreciate all the help you have and i hope will give me. Thanks
Jailsellgren  ;D

JonHylands:
I don't know about the rest of it, but the Sharp IR rangefinders are worthless as encoders. Check out this page:

http://www.robotshop.ca/home/products/robot-parts/sensors/encoder-disks/index.html

for some encoder ideas.

For accelerometers, check here:

http://www.sparkfun.com/commerce/categories.php?cPath=23_80

and for gyros, look here:

http://www.sparkfun.com/commerce/categories.php?cPath=23_85

The motor controller has to be matched to the motors...

- Jon

Admin:

--- Quote ---Here are 2 batteries, which should i pick if any
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1366
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=495
--- End quote ---

Althought it really depends on your motor current draw, Id say go with the 7.2V because both have the same price. Dont forget the charger!  :P


--- Quote ---what rpm and ratio of gear should i have
--- End quote ---

Use this tutorial to calculate rpm. You really dont need more than like 200rpm.
http://www.societyofrobots.com/mechanics_dynamics.shtml
Segway-like bots is a weird special case, so Im really not sure how to calculate torque for it . . . I guess just assume your robot is a long beam, with a weight at the end. Calculate the torque required to balance that weight:
http://www.societyofrobots.com/mechanics_statics.shtml
Its basically weight of robot * height of robot /2 = required maximum torque. The reason I divide by two is because you have two motors, so you only need half the torque. Yes, you will have to guestimate the robot weight and height . . . After you know this, you can decide on your motor.


--- Quote ---Heres a motor controller i found, suitable?
http://www.lynxmotion.com/Product.aspx?productID=92&CategoryID=10
--- End quote ---

Again, it really depends on your motors. Make sure the motors you choose have full load currents less than the maximum current rating of your driver. I think this driver will be fine, though.

Just one more thought, buy your components with the idea that one day you will scrap them for future robots you make.  :P

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