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hexagon
08-11-2010, 12:43 PM
Hi
I am building an all-terrain (sand, gravel, slopes, STAIRS) robot with a 6-wheeled design emulating Rocker-Bogie suspension. It has to carry a payload of 10kg throughout the arena of about 500m. I need to buy motors which can take this robot over the terrains mentioned. Clearly stair-climbing is the biggest challenge.
Please suggest the specifications of motors which can do this task. Presently I think a motor of torque 25kg-cm will do the trick. There is no much constraint in the speed of the vehicle.
Any suggestions regarding the motors and suitable drivers would be great! Also please suggest some shops from where I can procure very reliable motors along with encoders.

Regards,

vikas
08-11-2010, 02:08 PM
http://www.nex-robotics.com/products/motors-and-accessories/200-rpm-side-shaft-lm-series-dc-encoder-motor.html

They also sell compaitable encoder.

http://www.nex-robotics.com/products/motor-controllers/hercules-lite-36v-8amp-motor-driver.html

Motor controller ... About 8A capacity.

Such a project will be expensive , i hope u have a deep pocket.

hexagon
08-11-2010, 03:23 PM
Thanks for the reply. I will look into the links you have given. Hope the motors are very reliable and will not break while operating. Do mention if you have any first-hand feedback about these motors being used in high-torque-requiring systems like the one mentioned.
Funds are not a worry! :)

akshay66
08-11-2010, 05:52 PM
Hi all,
http://www.vegarobokit.com/product_descriptions.aspx?product_id=328&sub_category_name=RS%20Motors&category_id=41

You can buy these motors too.They are rated 45 rpm at 12v.The torque it around 15Kg.cm........These are quite powerful i am only suggesting you to buy these only if you run them at 24v. In that case you get awesome speed and tourque.i have used them for the same purpose but for a 4xWD.

http://www.vegarobokit.com/product_descriptions.aspx?product_id=49&sub_category_name=Tyres&category_id=46

Use them for wheels.Good quality & specially for ATR.

hexagon
08-11-2010, 06:07 PM
Thanks @akshay66.
The height of the stairs is 17cms. So we need bigger wheels than the one you suggested.
For stair climbing, what are the essential parameters to be kept in mind?
Regards,

akshay66
08-11-2010, 08:06 PM
hi all,
If the total height of the stairs is 17 cms then these are the best.Because the diameter of each wheel is 10 cm naturally the total length of robot will be greater than 30 cms. I'm sure the they will climb the stairs because they have great grip the pattern on the tyre is like of a pulse so they can easily get fixed with stair steps.I'm telling just try them once they will have no problem. My only concern is that what is the angle of stairs.This bot can at the max climb 35 deg.

One thing more you said something about 10kg load. Distribute the load on the robot evenly and try to put some extraa weight in front so that while climbing stairs and slopes your robot just does not fall back.Put counter weight if required .

Regards Akshay,

hexagon
08-11-2010, 08:59 PM
Hey
The stairs will be perpendicular to the ground like the normal stairs. So I think diameter of the wheel must be around 20cm or more.
Also the 10kg payload will be in the form of a cube of side 15cm. The motors must be able to carry the total weight of the chassis (20kg to be on the safe side including the payload) over the stairs.
Will a 20kg-cm motor do the task? Is there a possibility of the bot toppling?
Regards,

akshay66
08-11-2010, 09:29 PM
hi all,
I'm getting confused.No point talking like this first clear me about the dimensions of stairs.

The stairs are made up on several steps which are perpendicular to each other.What is the length of each step and the total length (sum of length of all steps) ??????

What is the length of bases(base here means the other part than steps, the part on which we keep our feet while climbing) .Now tell me what is the length in your case because it matters a lot.You'll get to know how steep the stairs are.If the length of bases is bigger than length of steps then we can easily do it but if its less then it'll have problems.

Don't worry about load 6 of such motors can easily carry 20 Kg.The bot will only topple if there is excess of weight on the front side and if you have excess in the bottom side then it might topple while coming down so balance it.I can only tell you some hints main is to be done by you.Try different possibilities.You can learn so much from such competitions if you do it from your heart.


Regards Akshay,

hexagon
08-11-2010, 11:17 PM
Hi
There will be 6 steps each of dimension :
Height: 17cms
Tread(base): 25cms

The robot has to climb up as well as down.
regards,

akshay66
08-12-2010, 10:33 AM
Hi all,
Thats too much................You'll have to change all the plans.

These motors wouldn't be able to do job.You won't get wheels with 20cm online you'll have to find them locally or get them fabricated.

I haven't used these motors but the specifications look attractive:
http://robokits.co.in/shop/index.php?main_page=product_info&cPath=2&products_id=276

These motors are fine no need to provide 24v.

You'll have to think about wheels.Try to get them fabricated.
You need to buy a compatible motor driver.These motors eat alot of current.

http://www.nex-robotics.com/products/motor-controllers.html


Regards Akshay,

allbits
08-12-2010, 02:51 PM
can you just post a link to the problem statement??

hexagon
08-12-2010, 09:25 PM
Thanks @akshay66.

hexagon
08-12-2010, 09:28 PM
@allbits:
http://www.drdo.res.in/scomp2010/index.html

akshay66
08-12-2010, 09:52 PM
No problem :)

You are taking part in this competition i also wanted but it not for school children.Best of luck & ask if any problems.The competition is big and tough.

hexagon
08-12-2010, 11:03 PM
we are trying our best :)

allbits
08-12-2010, 11:12 PM
is the link broken??

Coolpratheesh
08-13-2010, 10:52 AM
@ akshay.......Dude how many time have i told you ..... u never run a motor over its rated voltage u blow it.... like wat happened in ur competition last week....

akshay66
08-13-2010, 05:47 PM
hahahahahahahahahahahahahahahahahahahahahahaha :D :D :D :D what happened , i came 3rd :P
I know but sometime only for a short duration its alright.

adith
08-14-2010, 07:59 PM
Hi!
Friend you can find high torque motors of of 5,10,30,45,60,100,150,200,300,500,750,1000 RPM.......20kgcm torque for 200 rpm motors and also custom fabricated wheel of any dimension on order basis at Roland electronics in gujarati galli koti hyderabad ph:040-24762746,09849070411 cost of the motors high torque Rs750 only....and also all types of robotic spares customised..check it out...
enjoy i hope this infomation is usefull to pplzzzz...

akshay66
08-14-2010, 10:53 PM
Why don't you make a website ?????

vigyanabikshu
08-15-2010, 05:32 PM
Hi
I am building an all-terrain (sand, gravel, slopes, STAIRS) robot with a 6-wheeled design emulating Rocker-Bogie suspension. It has to carry a payload of 10kg throughout the arena of about 500m. I need to buy motors which can take this robot over the terrains mentioned. Clearly stair-climbing is the biggest challenge.
Please suggest the specifications of motors which can do this task. Presently I think a motor of torque 25kg-cm will do the trick. There is no much constraint in the speed of the vehicle.
Any suggestions regarding the motors and suitable drivers would be great! Also please suggest some shops from where I can procure very reliable motors along with encoders.

Regards,

Dear hexagon,
The best motor suited to your application is car wiper motor or power window motor and is available in automobile shop near you
They have a lot of torques. If they failed use a bus/truck wiper motor
To drive these type of motors, you need a motor driver board that can drive up to 30Amps
You can purchase it from some shops mentioned above but it will cost more than 1500 rupees.
You can make a driver board for just 75 rupees
For more details contact me

docel
08-16-2010, 12:08 AM
Hey!! Hold on- dont mis-guide the guy!!
Those are Worm-drive motors. Put them to move 30 kgs around and the worm gear will come off the shaft due to the momentum and the stop/start jerks.

vigyanabikshu
08-16-2010, 12:26 AM
A four wheel wireless robot works fine with these motors

stop/start jerks can be avoided by applying soft start and soft stop on PWM
worm gear will come off the shaft due to the momentum can be overcome by using a chain to drive wheels instead of direct wheel drive by motor

docel
08-16-2010, 12:32 AM
You cant do an independent soft Start and Stop PWM for 6 motors, without some real synchronisation.
Please read the OPs requirements first.

vigyanabikshu
08-16-2010, 12:46 AM
6 or more motors with independent soft Start and Stop can be done by using an I2C motor driver board to drive each motors
The I2C motor driver board consists of a low cost PIC(I used PIC16F676), an H-Bridge driver and a MOSFET H-Bridge
To drive a motor just send a command to the I2C motor driver board from the master PIC (Only needs 2 wires to drive all 6 or more motors)
See I2C motor driver board schematic that I build: http://www.roboticsindia.com/showthread.php/3564-drive-a-4-to-20-amps-dc-motor/page2?highlight=motor+driver

allbits
08-16-2010, 02:00 AM
A four wheel wireless robot works fine with these motors

stop/start jerks can be avoided by applying soft start and soft stop on PWM
worm gear will come off the shaft due to the momentum can be overcome by using a chain to drive wheels instead of direct wheel drive by motor

Sure, it does. You can make wired/wireless motors with these motors.
But the OP needs a 6 wheeled RB suspension. you add up the weight of 6 wiper motors, imagine the rise in total current required to move the bot, and the total weight of the bot.
These motors work well sometimes in robot wars. But I myself had a lot of bad experience with wiper motors when operated at high torques, mainly because of damage with the gears.
Also, small wiper motors these days comes with in built cam arrangement. Others, are pretty heavy - close to 2.5 Kg.

Yes, you can use the motors, but I would suggest you either modify the gear system, or modify the current plan of the robot, as you might need a heavy battery if you are running these motors.
The simply eat up current, and are pretty difficult to PWM. Trust me, you cannot PWM a Wiper like that. Not with the normal electronics.

The best bet I would suggest is a 15Kg servo modified for continuous rotation. Expensive, but best.

docel
08-16-2010, 03:36 AM
6 or more motors with independent soft Start and Stop can be done by using an I2C motor driver board to drive each motors
The I2C motor driver board consists of a low cost PIC(I used PIC16F676), an H-Bridge driver and a MOSFET H-Bridge
To drive a motor just send a command to the I2C motor driver board from the master PIC (Only needs 2 wires to drive all 6 or more motors)
See I2C motor driver board schematic that I build: http://www.roboticsindia.com/showthread.php/3564-drive-a-4-to-20-amps-dc-motor/page2?highlight=motor+driver

Have you tried this ?

akshay66
08-17-2010, 06:35 PM
Try what allbits reagrding servos.