2camjohn

Asking questions in the manner you are doing is disrepsectful and annoying.

What you are saying in essence is that you want people to spend their time helping you. But you cant even be bothered to phrase the question in a way most people on this forum would understand at first glance.



Regarding your original question: You say the school isnt much help. Perhaps that is because they want you to engage your brain and work it out for yourself.
But I guess thats takes too long, thats why you are getting the members of this forum to do your homework for you.

__________________
The first rule of mstechca club is do not talk about mstechca club.
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philba

Heh heh, reminds me when I was teaching college. My prof told me: "If you make them think they are thinking, they will love you but if you make them really think, they will hate you".

I bet the school wasn't much help because, instead of taking notes in the lectures, he was instant messaging with his "budz". Future fast-food professional, I think.

sicburger

Point taken.. Shall refrain from lazy typing.. Really do appreciate all the help and advice.. The school really doesn't knoe anything about the project.. All they did was give a brief intro to it and told was due in 3 months.. We did have basic electronics lessons but nothing on robots.. This is why im wrinting into this forum asking for help and advice.. I truely apologise if it was disrepsectful and annoying as 2camjohn had stated.. If its too much of a hassel then Ill go elsewhere.. really do appreciate all the help.. :P

2camjohn

sicburger,

Im sure no one wants you to go elsewhere.

I am still a newbie myself and I rely heavily on the help of people on this forum when I have problems with my own projects.



What you need to do is think more about the people who will be helping you. Make it easy for them to help you.

Try to ask specific questions and give as much information as you can.

Describe the experimentation and thought processes you have gone through so far. Show us that you have put alot of thought and effort into the problem already.

Show yourself to be capable and willing to learn.

Read your post at least once before you press submit.

You show appreciation by thanking people who have helped you, thats good manners. But doing your best to use proper English also comes under common courtesy for most members of this forum.

__________________
The first rule of mstechca club is do not talk about mstechca club.
http://www.electro-tech-online.com/s...induser&u=1245

sicburger

Im a mechanical engineering student in my school.The project is about building 2 robots that synchronises in movement and can move around confined places.. So far the group has been contemplating on which type of connection we should use to control the robots.. From infrared to ultrasonic.. our lecturer todl us to look up on designs first.. On how we want the machine to look.. So far we finished doing some free hand sketches on types of wheels.. Decided on omni wheels( i still dont get the 3 wheeled robot.. how is it able to go straight?).. Im gonna put it in PROe by the end of the week.. Gonna be designing the body next.. Ive just been told by my friends that a maze will be made.. 1 robot will be on a platform on top of it while the other will be in the maze itself.. So thats it for now.. Will update as time passes by.. Got school in the morning.. Please do forgive my arrogance n ignorance from previous posts.. Nite!

dknguyen

It goes straight because "technically" each wheel can roll in any direction (X-direction and Y direction). If you get two wheels to roll in such a direction that the movement in one axis cancels, and the movement in the other axis is the same, the robot will move straight in that direction. And since the third wheel can also roll in any direction, it won't interefere with that movement. (It makes it easier to think about if you just pick any one wheel to be the front and do nothing and have the other two wheels to control the movement.)

If the two robots are supposed to perfectly synchronize movement, it sounds like you are supposed to make it so that if one robot hits something, they both stop...that means the robots have to talk to each other...that makes things a bit more complicated (maybe).

Are the robots all autonomous or remote controlled? Because mirroring movements when they are both autonomous means that one robot is practically controlling the other robot (the only thing the slave robot does it tell the master whenever it hits something so they both stop). If they are mirroring movements based on a remote control then that means that they have to communicate with the remote control AND each other so that they both stop when they hit something...that makes things more complicated. How is it supposed to be exactly? Because making it so that they both stop when one hits something makes it more complicated than if they just blindly mirror each other's movements.

And are you sure you want to use omniwheels? You got two robots, and 3 fancy (expensive) wheels per robot with 3 motors per robot makes things pretty expensive...then again, maybe you are making the omni-wheels yourself since you are a MechE.

docel

Apology accepted. Let me rub it in some more..

Some years ago, the Chinese invaded India with their Cheap RC cars. Some thoughtful soul donated 20 of these to our school. The kids made short-work of these and in quick time, most of them conked out. The cars, I mean!
When asked, I agreed to repair, on condition: I get to work with them and the kids!

The result? CHAOS.

SYSTEM A
1 Master remote ( 27MHz TX), 5 Slave cars ( 27MHz RX )
The Slaves did everything together, by the Masters commands. This was quite interesting and a big hit with the Adults. The kids did'nt count, since they are always hooked, by default.
Imagine 5 cars of different shapes doing Fwd, Rev, FwdL, RevR etc.,.......Together in the concrete quadrangle!

System B

Obstacle sensors connected to a 27MHz TX buttons, 1 TX on each car.

Now , The cars did what the Master wanted + did what ANY ONE of the cars did too!!
All cars are going break-neck and suddenly veer to the right, or skid RevL or something like that, depending on the particular car what finds an obstacle...

This, was even more a hit.
....Except for some confusion regarding Master over-ride.

System C

After some other combos, the kids got bored of this, as usual. Some smart alec kid wanted assorted lights/ sound/ speech and the cars be camouflaged as demons, dance etc., and the whole troop echoed in cacophony.

I introduced them to F84s and Nigel. Then,

ALL HELL BROKE LOOSE !!!

sicburger

to all that has helped.. thank you..

JimB

One thing to be aware of, two robots are very unlikely to behave in exactly the same way (or mirror image) without the use of some kind of feedback control.

You may get near to it by using stepper motors for the drives and ensuring that both robots get the same number of pulses to the motors.

The problem comes from the fact that the parts are not absolutely identical. A bit more friction here, a slightly more powerfull motor there, the power supplies not identical, it just gets worse and worse.

JimB

__________________
Experience is directly proportional to the value of the equipment ruined.

docel

Right!
...Exactly why ALL HELL broke loose!!?
but then, who cares about precision in a toy?
Ordered 100 motors from Mabuchi. Had to resistance-equalise every pair for 'straightness" !!

philba

of course you could had added encoders to each wheel and used that to get equal revs...

docel

Yea, we do that for the path/Maze solvers where cost and complexity is'nt a factor. But for general line/ wall/ obstacle, a simple coil of solder will do! These never go straight, anyway :lol:
This also helps my students learn the hows and whats of resistance....