A.C.E.S. Autonomous Convoy Engagement System

[Vin]

This was my senior design project and first experience with this type of material. The follower car equipped with ACES (fancy way of saying IR sensors), follows the lead object/car without any communication between the two objects. There's a lot of improvements that could be made, but I don't think it's that bad for a first project. One of the group members made the song also. Let me know what you guys think, thanks.

[youtube]cKgOF5ZZJbU[/youtube]

[TrickyNekro]

Man that's very nice. Wish I had more info!!
Cheers!!

[airman00]

Ahhh I see how you got the cars to follow each other , very clever !

The leader car which is R/C has a piece of white material on the back of it. The follower car has two ( or maybe three IR sensors ( i can't see) which follows only white obstacles. Since IR can detect different shades this follower car will follow ONLY the leader car and not just any obstacle    ( unless the obstacle is white like the material  ) OK i'm not sure if you put in the shade detecting part , but you should probably add it in.

Nice job , I would like to see more documentation on this,


Also, this video demonstrates that Sharp IR sensors CAN work in indirect sunlight !

[JesseWelling]

The follower car has two ( or maybe three IR sensors ( i can't see) which follows only white obstacles. Since IR can detect different shades this follower car will follow ONLY the leader car and not just any obstacle    ( unless the obstacle is white like the material  ) OK i'm not sure if you put in the shade detecting part , but you should probably add it in.

Actually the sensor they used can't detect color, only distance. My guess is they had two control loops one for distance and one for steering. The steering control loop used the 3 distance sensors to measure the angle that the paper was at from it's frame of reference and turned the wheels accordingly (probably just a simple P loop or maybe PD judging from it's hunting motion), Then you do another loop (Probably PD) and have it close on the sensor that reads nearest to the object being followed.

What I want to know is how you worked around the minimum range of those sensors? IIRC it's a 20cm minimum, at which point the sensor is ambiguous. Was that a limiting factor on how close you could follow?

[TrickyNekro]

There is an old nice technique which uses only IR led and Ir demodulator.
Higher freq means shorter wave length and shorter distance of detect.
Lower freq means longer wave length and longer distances.
With some coding this actually enables the sensor to lock the object in one distance!!!
The freq varies from 36kHz to 40kHz!!!

Have fun!!!

[airman00]

The follower car has two ( or maybe three IR sensors ( i can't see) which follows only white obstacles. Since IR can detect different shades this follower car will follow ONLY the leader car and not just any obstacle    ( unless the obstacle is white like the material  ) OK i'm not sure if you put in the shade detecting part , but you should probably add it in.

Actually the sensor they used can't detect color, only distance. My guess is they had two control loops one for distance and one for steering. The steering control loop used the 3 distance sensors to measure the angle that the paper was at from it's frame of reference and turned the wheels accordingly (probably just a simple P loop or maybe PD judging from it's hunting motion), Then you do another loop (Probably PD) and have it close on the sensor that reads nearest to the object being followed.

What I want to know is how you worked around the minimum range of those sensors? IIRC it's a 20cm minimum, at which point the sensor is ambiguous. Was that a limiting factor on how close you could follow?

All IR sensors  can detect different shades

Meaning take a SHARP IR rangefinder point it at white surface 5 inches away and then at a black surface 5 inches away, and its different readings.

[Vin]

Actually color does not matter. I just happened to tape that white USPS cut box because we didn't paint the lead car and it's shell is transparent (which isn't too good for IR sensors). Plus it gives it a bit bigger detection region. You can see later in the video that it is following human beings, so it's not following a certain color.

The Sharp IR sensors (GP2Y0A02YK) actually have a pretty long range (from about 8" - 60") and only cost about $12.50 a piece. The two vehicles could have had a larger buffer region if wanted. I just had a threshold for the region in which acceleration/neutral/braking could take place. Since the sensor reading is ambiguous when the object is closer than 8", I know when to brake because logically, usually all 3 IR sensors (left, center, right) will detect an object in front of it when it's that close.

I tried to get really complicated with my code, but eventually found out that simplicity works best. I basically use only 1 loop get readings from the 3 sensors, apply digital smoothing to each to suppress the spikes. Now I basically have all the information I need to work with (distance from each sensor, and which sensor region has detected as object). I do my turning based on which IR sensors are triggered and within the threshold region. Then I use an autoscale function that performs linear interpolation on the sensor reading range to fit it into the range in which the ESC (electronic speed controller) can understand to control acceleration. The most challenging part was to figure out the timing specifications otherwise the ESC would lose signal and go haywire.

Let me know what you guys want to know or see. I made some nice looking diagrams containing the software flow chart and such. Thanks.

[airman00]

I want to see all of it ! 

Apply for an account here
http://www.societyofrobots.com/member_tutorials/node/27

and post it up in the members tutorials section!

[Admin]

Let me know what you guys think, thanks.

You gotta work on that stop-start speed control issue of the follow car

[TrickyNekro]

Let me know what you guys think, thanks.

You gotta work on that stop-start speed control issue of the follow car

Hep, Admin is right!!! You need to ramp the speed not smash the gas!!!
I thing it's called PID control (proportional–integral–derivative controller)
Have a look here:
http://en.wikipedia.org/wiki/PID_controller

[ed1380]

to add to what tricky said
http://www.societyofrobots.com/programming_PID.shtml

[Vin]

Let me know what you guys think, thanks.

You gotta work on that stop-start speed control issue of the follow car

Yeah, I just didn't have enough time to complete that part. The cars are moving about 1/4th of their capable speed so it is very sensitive and the speed range is small. The problem is that I am using linear interpolation to scale the sensor readings into the ESC's range of acceleration for that speed when the IR sensors range information is nonlinear (for example, if I have my hand 20 inches from the sensor and get a reading of 400, having my hand 40 inches from the sensor does not yield a sensor reading of 200). I will work on it when I get the chance. I wanted to eventually do multiple cars and have them capable of doing formations. Thanks.

[Admin]

I just put up this video of military robot convoys, and figured it might inspire you. I filmed that at a robot seminar I went to about a month ago at NIST.

[youtube]WhDdTomh2xg[/youtube]

[Spoil9]

He really didn't say much about how it was done, but I was impressed with what I saw.