Author Topic: cant figure out about motors, sensors...trying to build a line follower  (Read 2752 times)

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Offline DippulTopic starter

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guys..this is my mechanical graduation project...which i m doing in a company....i have a 32 I/O allen bradely's PLC...now i have done the programming part...it's basically a line follower which has to operate in a given space over three machine table...carrying machine component from one table to another when and when needed...the robot is supposed to carry a total wt of 50kgs including it's own wt....and i hv decided to attach four motors for this purpose each having a torque carrying capacity of 4 Nm...so total 16 Nm torque will be available...and rpm is about 30...now first problem is when the robot is supposed to take a turn...the programming is such done that i can keep only two motors in operation...so required torque is around 16 Nm but available torque is 8 Nm...now i m skeptical about whether the robot will be able to make the turn..motor on one side rotate in forward direction and the other motor right adjacent to the former rotates in backward direction during the turn...we can't try and test we hv to be sure before making any purchases of the motors...or we can use two motors which give 8+8 Nm torque but then the rpm of the motors also increases..now how to reduce that rpm?
Second problem is that we are using 4 different color sensors...we have not decided upon the colors as yet...so my question is which different colors to use so that it can't be confused by the robot's sensors..and wht to look for when buying these color sensors...
Third problem is we hv to provide a human sensor to the robot....now for that i guess i hv to use a IR sensor...but how to make it trace a large sector area..let say 150 degrees...i guess we need an actuator or a cam follower assembly for that..but will this work?
And please if anyone has done a sort of thing like this please do share your views....i am completely new to robotics...i am just a mechanical student...all knowledge i hv gained is reading through these well written tutorial on this site...i need an urgent help as in a months time i m supposed to complete this project

Offline SixRingz

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Well Dippul, that was sure alot of questions all in once... I'm no admin here but next time you might want to create problem specific posts like: "I need help with calculating motor torque" or "Need wide angle human detector for robot".

Ok, on to your questions:
You have problems with getting enough torque if I'm understanding you right? You also have a problem with too much rpm? This sounds like the perfect combination for a gearbox! The gearbox will take your rpm and make it into torque instead. What you have to look at is the rpm/torque demands. How fast does your robot need to be and how strong?

For your human sensor there's probably hundreds of ways to go about it. What I found in my local dealer was the Parallax PIR sensor. Don't think that will work if you put it on a mobile robot though... But if the bot is to operate in a smaller space you could statically mount it to sense the whereabouts.

Grounding things properly means burying them in the backyard...

Offline shlodo

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About your motors, u should do tutorial on this site on calc torque and rpm. 50 kg is quite heavy so u want to get these calc right. and if ur running through a gearbox to slow it down u will multiply the torque. Also take the diametre of ur wheels into consid as they will affect ur speed and torqu at wheel.
circumference of wheels x rps will give u speed
diametre of wheels will affect ur toque as well

Offline Admin

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Every one of your questions can be answered here:




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