line follower to take 90 degree turns in a rectangular grid

[shreyasjk]

hi,

i'm using a robot wit 2 wheels run by separate dc motors from a atmega16 via a H-bridge.
i'm using a 5 sensor array at the front to detect the line. how can i make an accurate 90deg turn on reaching an intersection??

 

[cr0sh]

You'll need encoders on each wheel; you can probably get by with a simple pulse encoder (a disk on the wheel with alternating black/white sections, and an IRLED/Phototransistor pair to detect light/dark changes facing the pattern, so as the wheel turns, the pulse output is read by the microcontroller). You might also want to check into quadrature encoders on the wheels, but it probably isn't necessary for your application. At any rate, as the wheels rotate, you monitor the pulses - so many pulses on the wheels will equal 90 degrees of turning. It won't be perfect (wheel slippage), but it will likely be close enough (maybe close enough for the error to be almost unmeasurable).

 

[FreeRideSkier]

I use a motor + encoder + controller combination from Robot Electronics: RD02. (Controlled by FlowStone DSP software via a COM port)

You can read the encoders and move one wheel in one direction and one in the other to make a very accurate 90 turn.

But surely wouldn't it be better to detect you have turned enough from the sensors instead? That way your bot could follow any line with no encoders?