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Feedback mechanism for straight line motion


We have to build a model to go dead straight, without changing directions. We are using 2 motors up front to power the vehicle, so the first thought hitting us to maintain straight line is to capture feedback from the motor rotations and make sure they are equal all the time.


Being a newbie to labview, I've looked up a few tutorials, lots of pages to get me started, we could definitely do with some real time help too. Still struggling to get a hang of which direction to take and start off building the VI. A quick pointing to something which could get us going would be greatly appreciated.



Thank you,


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Hi testtrack,


As I understand it you have a differential drive robot, with two wheels powered by electric motors and a coaster at the back, and you have encoders on the two front wheels.


If you have not already you will have to decide on a convention for controlling the speed of the wheels, I would recommend PWM (Pulse width modulation).


To help you further I would need to know the encoding scheme used by your encoders, and what hardware you are using to communicate with labVIEW.


Try taking a look at the DAQ assistant express VI, this has built in functions for receiving inputs and generating outputs and can be set to record encoder counts.


Here's a tutorial that should be of help to you


Please get back to me to let me know how you get on.


Joel G
Applications Engineer
National Instruments UK & Ireland
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