Content in “line follower”

Picaxe code for line follower

fritsl — Sun, 13 Apr 2008 22:23:15 +0200

tHIS POST IS A MESS. iT IS EDITED SEVERAL TIMES AND MAKES NO MORE SENCE. i HAVE NO TIME TO DO MORE ABOUT IT: bOTTOM LINE IS THAT THERE IS ATTACHED A ZIP-FILE WITH ALL i EVER DID INlINE-SENSORING FOR pICAXE!

Chris the carpenter asked for picaxe code to line follower.

First you have to hook up the sensors to the analouge in. That is a chapter for itself, but in the end you will have a value for each sensor; 0-255

I have tried some different line-sonsors, once JIP and I was playing around with them.

Opposite what JIP believes in, I think that a man only needs 2 sensors to make it work.

Fur fun, I made the smallest routine I could. I cannot remember the correct syntax, but it goes something like this:

main:

readadc 0, b0
readadc 1,b1

pulsout 0, b0
pulsout 1, b1

goto main

It actually worked quite fine! The more white on one side, the more throttle. Only, motors only ran with 50% in average, which is not optimalk ;)

So I wrote some other code, and looking at it now, I cannot find head or tale in it, I must admit - but you asked for it, Chris, and here it is. Erh - here is some code, I made a thousand versions.

The line-follower on the picture & video does have 4 sensors, but that was just because I was testing what that line-sensoring-thing was all about, only 2 spaced just a little wider than the black line is used. Erh.. the code, I can see is using 4 .. Whatever - it is so goddamn easy to make that code, use mine as an example, my robot no longer exists ;)

As you can see, even if the robot is held in one side, it just insists on stauing on track, and there is no wobbeling on straight tracks - mision completed IMHO ;)

symbol tolerence = 25

main:

readadc 0, b0
readadc 1, b1
readadc 2, b2
readadc 3, b3

if b1 > b2 then gosub H
if b1 < b2 then gosub V

goto main

H:
b4 = b1-b2
if b4 > tolerence then
low 5: low 4
low 7: high 6
else
gosub L
end if
return

V:
b4 = b2-b1
if b4 > tolerence then
high 4: low 5
low 6: low 7
else
gosub L
end if
return

L:
high 4: low 5
low 7: high 6
return

Yeke! Google video does not like videos from my old phone, pretty slow framerate it makes out of it. So I also attach as a file, see below - you should download it before viewing - on my PC I get the movie in ascii if I just click

Bad robot!

jip — Wed, 09 Apr 2008 19:49:19 +0200

Today was the qualification round of DTU robocup. My robot did not do very well at all - it tied with 7 others for the last place - getting 0 points!

When testing the robot on the robocup track the first thing that was wrong was that the lighting was so bright, that the sensors were all fully saturated all the time and thus couldn't see the line. That problem was somewhat solved by adding a lot of cardboard and tape plus some clothing on top to keep the light out.

Next problem was with speed and torque. Since I had not been able to fit the 4:1 gear reduction, the motor had to be driven VERY slowly in order for the robot to stay on the line. This means it had very low torque and that resulted in the robot not being able to climb the ramp after port number two. Of course this was not a problem at the actual qualification round since the robot lost the line shortly after start in both of the runs.

I learned some lessons and hopefully I will try to use what I learned in the next robot for robocup in a years time.

I forgot to take pictures at the competition!

Maybe I will try to make the robot work better at home some time soon.

Now it must be time to do some chair challenging!

Robot Hansen

jip — Sun, 16 Mar 2008 16:54:46 +0100

Primary image

What does it do?

Line following for DTU Robocup

Out of pure frustration with the fact that my LEGO MINDSTORMS NXT based robot, that was supposed to participate in DTU robocup, turned out to be crap, I thought that I'd try to at least get a decent line follower ready for robocup. This robot is based on my R/C car - an HBX Bonzer Monster Truck XTI - and it will only be able to follow a black line and hopefully also be able to handle line branches.

To start with I was going to build a line sensor based on 8 infrared detectors for 36 KHz modulated infrared light. There were some problems with that so I decided to go for 4 regular infrared photodiodes instead. It is my plan that I will estimate robot position relative to the line by interpolating values between the 4 sensors to get a smooth steering - maybe I will use PD-regulation for this if I have the time.

For controlling the car I'm interfacing the LM-406FB speed controller that came with the car. It is controlled by sending standard servo signals to it, but it does some fancy interpretation of the sequence of signals so one has to be cautious or the car maybe not work the way one intended. For steering the car I'm just using the standard servo that is in the car.

I think maybe I need to get a gear reduction unit for the car, since it goes really fast and I think the robot will be impossible to control at high speed - it tends to skid around when going fast. I'm looking at a 4:1 gear reduction unit which can be bought through eBay.

Friday 28th of March, 2008

I have made the base for the line sensor by cutting a perforated board to a shape that will fit nicely onto the car and can be held in place by a couple af screws that already hold the front bumper in place (I think I might some longer screws though since they just barely hold the board):

Now I just to populate the board with some fancy components that will make the bloody thing work!

Cost to build

Embedded video

Finished project

Number

Time to build

Type

wheels

URL to more information

Weight

PICAXE Pete

jip — Fri, 08 Feb 2008 15:33:57 +0100

Primary image

What does it do?

Since this project is not finished yet the robot just sits there for now...

Most of the LEGO platform used for this robot was used in DTU RoboCup 2006.

PICAXE Pete is my first time using the PICAXE controller.

The robot has a homemade line sensor using light dependent resistors (LDRs) and a homemade PICAXE-board with an L293 driver chip as well (see picture).

It can either connect to a single 7,2 V pack og two of these in serial (for giving the motors more power).

Power to the chips and line sensor is regulated by an LM7805 voltage regulator with some bulk capacitors. Of course the PICAXE board also has a means of connecting the programmer cable to the board for programming the PICAXE chip.

I took the robot apart and took some pictures while putting it back together - just so you can see how it's made. I think the design is rather nice actually :-)

First of all there is the "engine block":

Then there is the "tail section":

These two are then put together:

(Disregard those grey 1x4 plates in the left side of the picture. They're a leftover from some strange idea I had. Next image shows some added axles for the active wheels (notice they run through the rotation sensors - they're the blue ones in case you wondered). There's also been added some things at the front for the line sensor:

Then finally the active wheels (from the Technics Super Car set) are added and the vehicle is finished:

A look from the rear:

This is kind of an expensive construction since it uses bricks from a MINDSTORMS 2.0 set, a Technics Super Car set and two separately purchased LEGO rotation sensors (they are NOT cheap!). Anyway I like this vehicle!

With line sensor, controller board and batteries the whole thing looks like this:

It's not really the prettiest robot in the world :-).

Cost to build

Embedded video

Finished project

Number

Time to build

Type

wheels

URL to more information

Weight

A thousand little creatures

fritsl — Thu, 07 Feb 2008 17:40:30 +0100

Primary image

What does it do?

I must have made a hundred modificated versions of easy and fast robots like this one.

They are really fast and easy to do - it is quite fun to do quick modifications, and make them battle, or do new tricks, test new sensors etc.

Cost to build

Embedded video

Finished project

Complete

Number

Time to build

Type

URL to more information

Weight

NXT Line Follower

jip — Tue, 05 Feb 2008 19:55:16 +0100

Primary image

What does it do?

Smoothly follows a black line

The robot measures line position with the 4 line sensors and feeds this to a PD-regulator which in turn produces the two motor outputs. This setup gives a smooth line following.

The cost of the robot is roughly the cost of a set of MINDSTORMS NXT + 3 additional NXT light sensors and the rechargeable battery.

The time to build includes several mutations of the basic design - time flies when you play with LEGO ;-). Of course some time was spent finding some usable values for the P and D constants for the PD-regulation.

I used the Bricxcc IDE for developing the controller program.

Cost to build

$650

Embedded video

Finished project

Number

Time to build

5 hours

Type

URL to more information

http://defiant.dk/movies/nxt-robot2.mov

Weight

722 grams