# Help with servo-motors

I have built my robot with two servo-motors (with encoders) and ultrasonic sensors , the mobile robot should navigate from its initial point to goal point without collide with any obstacles dependent on the Artificial Potential Field algorithm , I want to find new xy coordinate point of moving robot , In this I am using two servo-motors, one per axis , it gave me pluses , from this what is the best way to find angle and coordinate xy of mobile robot from these pluses, even though there will be error and inaccurate result , it is ok for me .

I would be very much appreciate any help.

thanks

Hello.

It looks like you have another post asking very similar questions. The tutorial in the SourceForge link that Jim posted looks like it goes over dead reckoning and keeping track of x and y coordinates. Is there something more specific that you had questions about?

It sounds like you might be confused about how you can use the pulses (or “ticks”) from your encoder. You should be able to measure the number of ticks you get from moving your robot’s wheel some fixed distance. Then, you can use that information to find out the distance the wheel travels per tick of the encoder. By keeping track of the distance that each wheel has traveled, and knowing the distance between the wheels on your robot (often referred to as “track”), you should have enough information to keep track of your position and angle as detailed in the tutorial mentioned earlier.

-Brandon

[quote=“BrandonM”]Hello.

It looks like you have another post asking very similar questions. The tutorial in the SourceForge link that Jim posted looks like it goes over dead reckoning and keeping track of x and y coordinates. Is there something more specific that you had questions about?

It sounds like you might be confused about how you can use the pulses (or “ticks”) from your encoder. You should be able to measure the number of ticks you get from moving your robot’s wheel some fixed distance. Then, you can use that information to find out the distance the wheel travels per tick of the encoder. By keeping track of the distance that each wheel has traveled, and knowing the distance between the wheels on your robot (often referred to as “track”), you should have enough information to keep track of your position and angle as detailed in the tutorial mentioned earlier.

-Brandon[/quote]

Dear Mr. Brandon , many thanks to you .

now almost things came to be clear , but there is one thing need some clarification , which encoder should i got to calculate the position (coordinate x y) and orientation (angle ) of mobile robot ,because as you know there is many types of encoders (incremental , absolute ,…etc.) , I read about each one in the websites but I still confused which one will be the desired for my problem .

thanks

It sounds like either type of encoder you mentioned should be able to do what you want. You should be able to use incremental encoders to keep track of your x and y coordinates if you have some reference to go off of (such as assuming the robot starts at the origin or doing a calibration). It is up to you to determine what encoder would work best for your system.

-Brandon