Leader - Follower Robots

[Tweeter0830]

Hi, I'm thinking it would be cool to make several robots which could follow one mother robot. Maybe for some extra class I could dress them up as a hen and chics. I would like the follower robots to keep a set distance from the leading robot.

The only cheap way I could think of doing this is by placing an IR diode on the back of the leading robot and two IR receivers (at 45 deg with respect to lateral line) on the front of the follower. I could use the relative intensities of the two receivers to turn and use the averaged intensity to determine a rough estimate of range.

However, I would like this whole set up to work outside in sunny conditions. I know modulated IR is one way to get around the sun issue, but is there any way to use modulated IR and still retain analog measurements of intensity? The only receivers I've used are digital.

Any suggestions would be great. Also, if you guys can think of any better methods for this, that would be great too.

Here's something similar, but I'm thinking something smaller scale and cheaper.
http://www.societyofrobots.com/robotforum/index.php?topic=3618.0

[Joker94]

have you considered using ultrasonic sensors as i don't believe they are light sensitive

you are able to get them mounted and ready to use or if you want to try do it your self it may be cheaper

you can get just the sensors in 2 packs like this for $5.50

http://www.futurlec.com.au/Ultrasonic_Sensors.jsp

i  am not sure the costing of IR

i think that the vedio uses IR so it may be the best way to go

[Tweeter0830]

Cool, thanks. Those seem like good deals. What do you guys think about this set up? It might work. The two IR receivers tell the follower whether or not to turn. If only the left IR receiver is picking up the LED, then turn left. If both are picking it up, keep going straight while the ranger finder keeps a constant separation distance. This seems like it would work fairly well, but the way the two receivers are angled might mean really poor performance at long and short distances with a sweet spot in between. I could add a third IR receiver in the middle maybe?



Any thoughts on a better way to do this?

I want to keep the IR as a way for the robots to identify each other so they don't follow any random object.

[Joker94]

what you could do is build your electronics and build the robot get the sensors and test them and find the best angle. and once you have done that then you can fix them to the robot body

having a 3rd IR in the middle would be more accurate and easier to code but you could easily get away with just 2, it would just take more time coding and finding the right angle

if it was me i would go for 2 but if you want it to be really accuat go for three

it all depends on the amount of tim you are willing to spend to get the bot up and running well

[Soeren]

Hi,

[...] If both are picking it up, keep going straight while the ranger finder keeps a constant separation distance. [...] I could add a third IR receiver in the middle maybe?

Any thoughts on a better way to do this?

Coding for 3 sensors won't make anything easier! You'll need more code, more sensors (obviously) and you won't get a tiny bit extra precision.
You don't really need a range sensor either, just code (and angle/baffle) it so that if you can't see with both "eyes" no matter how you rotate, you're too close and should decrease speed or stop completely (while still scanning). As soon as the "mother" moves further away, you'll once again be able to "see" the IR with both sensors.