some problems

[ahmedragia21]

im trying to make a line follower robot , the sensors are constructed by compartors with the LDRs,they work well, but the robot moves very fast , it can detect the line , but it cant move at the turns , i attached the pic with the illustrations , also it seems that the sensor affected by ambient light should i cover it right ? , also i've a problem that the two motos arent equal in speed they are used motors so what can i do ?

now im using two Sensors , can just two work well for this purpose ?
truth table
0 0 move forward
1 0 rotate right
0 1 rotate left
1 1 move forward
thanks alot

 

[Marks256]

Just have the bot stop, then rotate to find the line again...

 

[ahmedragia21]

you mean at the condition 1 1 let the robot stops ? and then track the line ?
but can two sensors and at its high speed do it ? its speed is very hight approx 50cm/s ...
also the robot dosent move in straight line without the two sensors i think because there's a motor which runs faster than the other ,what's the solution ?

 

[dknguyen]

It's due to the motors running at uneven speeds, wheel misalignment and wheel slip. You can't really fix wheel slip even if you record the RPM of thw wheels with a quad encoder. Maybe a gyro or compass to keep track of long term heading but it may cost a bit more money than you want.

But it's a line follower...who care if it goes straight? It has a line to follow. Even if it could go straight, it will never be able to perfectly be in parallel with the line anyways.

 

[ahmedragia21]

Even if it could go straight, it will never be able to perfectly be in parallel with the line anyways.



but it doesnt follow the track at the crossing lines, at the crossing of the track i.e 1 1 of the two sensors,i let the robot to move forward , at this time the robot should track the line , it doesnt, it bends from the line away :S..


also is this a probelm of the LDR, i tried to change the LDR with a phototransistor but the circuit didnt work , no behaviour of the phototransitor :S

 

[Marks256]

What i mean is, let the robot track the line as long as it can. if it looses the line, then let the robot rotate to find it again... Maybe i am not understanding your question...

 

[ahmedragia21]

i'll try to let the motors using PWM , but i want the robot to move in straight lines without the line tracking sensors how can i manage that ?

 

[Nigel Goodwin]

You probably can't, in order to go straight it really needs to be following something. You could measure the number of turns of the wheels and keep them the same - but this still doesn't keep it dead straight.

 

[ahmedragia21]

the problem that we are using fast motors and used and we couldnt find motors for our needs ,and they move very fast that's why i found some problems when tracking the line at this speed ..
im using now 2 sensors , would increasing them to 4 or 5 make it track better and follow the crossed lines as the picture shows ?

 

[Marks256]

Why not buy some servos?

 

[ikalogic]

hello ahmad how are you..

i don't think it's a very good idea for your (or for you'r brother) to be discussing robon's ideas infront of the whole world,... other competitors like me can steal you'r idea .. but don't worry i am not stealing this one... lol

do you have an idea about date of the competition (april or july?)

 

[ahmedragia21]

Hi, it worked guys , thanks

ikalogic , i dunno really the appointment of the contest .

https://www.youtube.com/watch?v=TRE3nyajzcs
https://www.youtube.com/watch?v=0Ca1j7P9H98