Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: mech223student on January 08, 2014, 01:04:29 AM

Title: Sensors to Travel Along Raised Platform
Post by: mech223student on January 08, 2014, 01:04:29 AM
Hello Society of Robots! I've come to what looks like your pretty awesome community for help on a mechanical engineering project. My name is Leo, I've just been assigned my first robotics project, and I'm a little overwhelmed. Having dealt in only mindstorms and basic arduino coding before, my experience is unfortunately lacking in robotics so far.

Our project requires an autonomous vehicle to travel along raised platform with gentle curves of unknown location and then turn around at the end and retrace it's steps, all without falling off. The platform is about 1 foot wide, and there's to be no "clamping along the sides"--the robot must be guided through sensors or other methods.

I've done a little research on sensors so far, but does any obvious solutions come to your more cultivated mind? Would it be better to use a bang-bang approach, correcting only when the robot approaches the edge, or a more proportional control system such as keeping the edges equidistant from the robot's centre? How might the robot distinguish the end of the track as opposed to the curves?

Thanks in advance for your help! Regards,

-Leo

Title: Re: Sensors to Travel Along Raised Platform
Post by: waltr on January 08, 2014, 08:24:55 AM
I think Line follower type sensors would work to detect the path edges and the end (put a sensor far enough out front to detect to end early enough to stop and turn around.

I think proportional direct control would be best but do start with a simple bang-bang. Search for proportional line followers for sensors and code ideas.
Title: Re: Sensors to Travel Along Raised Platform
Post by: bdeuell on January 08, 2014, 08:50:04 AM
One common way to differentiate between the sides of a path and the end is to use an array of sensors across the front of the robot. When all (or most) of them detect the edge you have likely reached the end; when only the left or right sensor detects the edge you are likely still traveling along the path. This works well for environments with narrow paths and gentle curves. A little testing/tweaking might be necessary to get the desired performance.
Title: Re: Sensors to Travel Along Raised Platform
Post by: jwatte on January 08, 2014, 11:21:55 AM
Get a 3pi robot, tune the IR sensors to recognize platform as "there," problem solved :-) http://www.pololu.com/product/1306 (http://www.pololu.com/product/1306)
Can do the same with a Zumo and a strip of IR sensors: http://www.pololu.com/product/961 (http://www.pololu.com/product/961) http://www.pololu.com/product/2506 (http://www.pololu.com/product/2506)
Or, if the platform is made of matte black material, use two ultrasonic distance sensors at the front two corners of the 'bot, on any rover-like bot (there are tons to choose from at $40 and up.) http://www.trossenrobotics.com/parallax-ping-ultrasonic-range-sensor.aspx (http://www.trossenrobotics.com/parallax-ping-ultrasonic-range-sensor.aspx)
Some of those components (or clones) can be had cheaper on places like ebay.com or dealextreme.com, if you are OK with that level of "support."

Title: Re: Sensors to Travel Along Raised Platform
Post by: mech223student on January 10, 2014, 02:06:46 AM
Thanks a ton for the replies everyone! Your ideas have inspired a lot of concept generation and research on our part. I'll return here with more specific questions as they come up :)

-Leora