View Full Version : Selection of motors for differential motor system

12-29-2005, 10:40 AM
Hi, I hope you guys could help me with this problem: which type of motor is better for differential motor system. In fact, I need the robot to go in strictly straight lines.

Can stepper motors with odometry system work?

12-29-2005, 01:21 PM
if u want ur robo to move straight, then steppers would be the best option.
u can set equal no. of steps.. and they don miss steps usually.
they work really well....
however if u r using steppers, be sure tat the payload of the robo is less, becoz they don offer high torque.

12-29-2005, 02:04 PM
Hi guys, look ichigohnvn when you use steppers you simply do away with the hassels of optocouplers and shaft encoders. While for a dc motor , you need to have some kind of shaft encoder to ensure that you are getting the rpm you need.

If you can manage a nice accelerating and decelerating mechanism , then I think stepper motors are better. Just look for some other probs like wheels slipping which also cause speed mismatch.

And if managed intelligently, steppers do take high loads also.

12-29-2005, 02:05 PM
How about servo motors? We can make the two wheels rotating at the same speed with servo motors right?

12-29-2005, 02:46 PM
ya u can....
but as i said, steppers ll also behave nicely, don worry about tat.

as for the servos, they r costly and can dig a hole in the pocket.
steppers u can always get from comp. junks.

12-29-2005, 03:48 PM
Ok thank you guys!!!

Got it. :)

12-29-2005, 03:53 PM
ahh just one more thing, there's no problem to make a differential motor system with stepper motors right? :?

12-29-2005, 11:03 PM
no, there wont be any probs.
it is meant to reduce such problems only.
the smaller is the length of the robo, the better differential drive u can realise.
ideal would be to have two steppers and two wheels mounted on them and nothing else. u ll realise best differential drive then.

12-29-2005, 11:30 PM
Ok then...Could u guys tell me how to implement dead reckoning using stepper motor system?

12-30-2005, 12:42 AM
They are also the most efficient, load to power/performance.
It is quite simple to fabricate a differential system provided ypu have the above capacities.
ichigohnvn, what is your requirement?
All your posts sound high-tech that require a lot of practical hands-on shills and experience. Not to discourage you, but I think you should start on some base and then query about fine tuning them.
One cannot lay claim to something or anything unless it is one's own concept and idea.

Do something first and then ask for advise/help.
sorry guys- now, i am really shouting!

12-30-2005, 02:08 AM
hey docel,
relax..... take a chil pill.
but ichigohnvn, he's right....
i think its time tat u begin ur project and then see wat all probs u face...
believe me, u ll get jacked in small things at the first place...things which may seem quite obvious and simple now....
so dude, get going and begin ur project.

12-30-2005, 08:39 AM
finally someone opened their eyes to inherent spoon feeding...

Work first ask later..


12-30-2005, 08:48 AM

It's not that I dont want to start the project right now. But to be honest, I am at Singapore and it is quite hard to grasp those kinds of robot components. I have to buy them from other country indeed. So I hope you guys can understand me, I have to think careful and know exactly about the things before buying them. Partially because my fund is quite limited and partially I cannot just come and get the parts as you see all the things must be taken from other country.

And to docel, if you say that you build the robot just using your own idea and knowledge then think again. We cannot have any improvements by ourself unless we totally understand about the things. :?

I think I go for modified servo motor anyway. Thank you buddies. :wink:

12-30-2005, 06:06 PM
Dont get disheartened dude but yes your posts strechted a lot just discussing without you doing anything.

We all have money problems as we all are students doing robotics as a hobby, thats why I gave you solutions like stripping off computer scrap. Now dont tell me that you dont get computer scrap in Singapore, and is it costly there? Hmmmm....hard to believe.

So instead of buyin costly components for experimenting , use junk , and when you know what exactly you need then go and buy the new item.

I give you one example....... After discussing a lot in this forum if you make your mind to buy a servo motor and go in the market to buy one. What rating will you ask for? How will you decide whether it will work or not ? Can it drag the payload ? Whats the rpm you need ?

These queries we cant answer sitting on our desks.......this comes by experience. I have a very wierd style of testing torque of motors by hand , but believe me now I am able to make out that will this motor work for me or not !

So just use some junk and make your hands dirty , just play around a bit to know how they work. Then you yourself can decide whether you need a DC Motor, Servo Motor or just a simple stepper motor !

Cheer up now, and start the work !!!!! :D