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Rookie

Joined: Sun Jul 20, 2014 10:14 pm
Posts: 11
I just have finished doing a simulation by Matlab environment for navigation a mobile robot from its initial point to goal point without collide with any obstacles dependent on the Artificial Potential Field algorithm , and it is done successfully.
Now , I would like to do that practically and I'm new to this "world" , I have built my robot with two motors and ultrasonic sensors , but the hardest part which I faced is which components should I have to get the current position (i.e. (x,y)) and the orientation (i.e. Azimuth) of mobile robot , so what is the simple approach and simple components for this task , please give me the simple solution because I am novice and I have no enough time, it is just one month and I should finish that . I would be very much appreciate any help.

thanks

Sun Jul 20, 2014 10:22 pm
Professor

Joined: Sat Aug 31, 2013 9:15 am
Posts: 256
For orientation, you can use a gyro sensor. It gives you the speed at which the robots turning, which you can multiply by time to determine how far it has turned. You can accumulate the turn amounts in a variable to keep track of orientation. Alternatively, you can use a compass sensor for orientation. For keeping track of X and Y, I don't know of any sensor that will help you with that. I think you'll have to track straight line distance using encoders, then use the orientation and some trigonometry to determine how far it is travelling in X, Y coordinates.

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Mon Jul 21, 2014 10:59 am
Rookie

Joined: Sun Jul 20, 2014 10:14 pm
Posts: 11
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

Wed Jul 23, 2014 1:48 am
Professor

Joined: Sat Aug 31, 2013 9:15 am
Posts: 256
I'm having trouble picturing this. Do you have one servo motor that moves your robot forwards and backwards and one that moves it side to side? Or is it a drivetrain with a left motor and a right motor?

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FTC Team 7468 Blue Chariots of Fire - Programmer (2013-2014)
FTC Team 7468 Blue Chariots of Fire - Mentor (2014-2015)
Check out our team website at http://bluechariotsoffire.com/.

Wed Jul 23, 2014 10:16 am
Rookie

Joined: Sun Jul 20, 2014 10:14 pm
Posts: 11
 BurningLights wrote:I'm having trouble picturing this. Do you have one servo motor that moves your robot forwards and backwards and one that moves it side to side? Or is it a drivetrain with a left motor and a right motor?

Dear BurningLights , many thanks to you .

Simply, I just want design a differential drive robot with two servo-motors (with encoders) , one per axis that could navigate from its initial point to goal point without collide with any obstacles dependent on the Artificial Potential Field algorithm , but I have faced two problems :

First , 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 .

Second , after I got the desired encoders with servo motor , how I could calculate or translate the pules the generated by encoder which mounted to motor to the corresponding position and orientation .

Many thanks

Thu Jul 24, 2014 5:27 pm
Professor

Joined: Sat Aug 31, 2013 9:15 am
Posts: 256
For your application, I would recommend incremental encoders. It's difficult to determine robot orientation based off of encoders, but I think there is a formula you can create that can roughly determine the number of degrees a robot turns based off of wheel rotations. I'm not sure how to create that formula, though. But, if you know the orientation, you can use the encoders to know how far the robot is travelling in a straight line, then you can use trigonometry to convert that into X, Y coordinates.

_________________
FTC Team 6100 Chariots of Fire - Programmer (2012-2013)
FTC Team 7468 Blue Chariots of Fire - Programmer (2013-2014)
FTC Team 7468 Blue Chariots of Fire - Mentor (2014-2015)
Check out our team website at http://bluechariotsoffire.com/.

Sat Jul 26, 2014 10:15 am
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