REQ: Robot line follower & obstacle avoider?

[shobits1]

I wanna build a robot aiming to follow a dark line in white & avoid obstacles in the why, I think I will use a PIC16F876 or PIC 16F877 (since it have ADC, and have two PWM output).

I have some idea how I will start (like using photo sensor, ultrasonic transceiver …), but I am way confused since it is my first time to work with stuff like this.

If you have any idea, book, or anything could help then please tell me  

Also I think to add extra feature then what I find in the Net, like a small keyboard, and LCD to configure the robot (speed, sensibilities of the sensors, the minimum range to be avoids ….)
If you have any idea to be used as an extra feature, I will appreciate your help

Thank you for your help in advance  

[maddoc]

For the price of an old design 16F877 you could get a cheaper 18f2525, much more program memory and ram, 40MHz clock and so on.
It could be a better starting candidate with lots of room to upgrade afterwards! Just my 2c.
This forum is full of information, search is your best friend!

[bliviudaniel]

I agree with maddoc. Use PIC18F. For example PIC18F4620 is pin to pin compatible with PIC16F877, but it has 64k of flash and 4k of RAM, 1k of EEPROM. (You can run easely a RTOS on him...if you will ever want to upgrade your robot.)

[Kabron]

http://elm-chan.org/works/ltc/report.html

[shobits1]

I am gratefull for your replays, and i want to make it more clear, my project is restricted to use only 16F877 or 16F876 (i think i will use a serial memory if the mcu memory not enough),

'Kabron':  thank's i already have a look to the project, but for my project i will use the ADC hocked to the photo sensors, and i will use to type of motors, a DC motor for forward-backword using PWM to control the speed, and the other is a stepped motor (more likely i will use the motor in my broken hard disk) to control the angel for direction the robots right-left, also i think i will use the 3310 mobile phone LCD for show and configure the robot

anywhy thanks for the help, (i'd like this thread to be more active)

when i complete my project i will post it the full project section

[bliviudaniel]

Why do you use the third motor? You don't need it!
You may control the direction only with 2 motors.
Search for "robot differential drive" in Google.

Some links, for example:
http://planning.cs.uiuc.edu/node659.html
http://groups.csail.mit.edu/drl/courses/cs54-2001s/diffdrive.html
http://ncart.scs.ryerson.ca/NCART/EDUCATOR/Diff_Drive_Veh.pdf
http://www.societyofrobots.com/programming_differentialdrive.shtml

And by the way, PIC16F877 should be enough to control the motors, read analog photo sensors and control LCD. PIC18F would have been far better, but you should handle well with PIC16F.

[shobits1]

thanks  'bliviudaniel', but i don't intend to use a three motors, i will use only two motors the first will be a DC motor for drive straight or reverse (using PWM to control the speed), and the second will be a stepper motor controling a front wheel to turn left or right.

I think using a stepper motor to control the direction will be more effecient than using two DC motor, if you have any experience please tell me.

[Roshan]

Hi All!

I have already made this project using 2 motors. I use PIC12F508. This is 8 pin mcu & where as i remember it uses approx. 100 program words. Then why are you using 8k program memory & 40 pin mcu.

Regards

Roshan

[shobits1]

expect from my project must made with 16F877, I wanted to do it with a lotsof options, so i will add a keyboard to configure the robot directly also i will add a LCD to show the configuration menu.
i will use the A2D converter to manipulate the IR sensors also i will add an ultrasonic tranciever to detect objects in the way and act, even i think to save what the track look like when the robot is movig and extract the informations to the pc using serial port.
i think the 16F877 is the most suitable for this (even i think i will front a problem with memory but it's the only choice for me).

[bliviudaniel]

I built 2 robots until now using differential drive. It's very easy to control the direction and no doubt more efficient. With differential drive it is even possible to spin(the robot can turn 90 degrees right/left without moving forward, back, right or left)! With the system you want to use, I think is impossible to turn 90 degrees without moving forward/back.
Look at the robot in the following movie:

http://www.youtube.com/watch?v=jalUweOh3wA

and see how it's turning right or left. It's using differential drive. And dispite it's a minisumo, I built it with line following capabilities.(I don't have a line/track circuit, so I have no movie with the robot in line following mode).

Tough, there is an disadvantage using differential drive. If the contact surface between wheel and floor/ground is to big, there will be a lot of friction when tunring right/left. I think that's a reason why it's not used in commercial vehicles.

[shobits1]

I  really like the capability of differential drive (easy to implemen & control)but i am not sure if it's work with robot of 30x20(LxW cm)mybe 1 to 3 kg of weight. any advice

[witsanukai]

Dear Friend
Why not used servo mortor
I think it's easy because include gear box
http://www.embeddedtronics.com/servo.html

[shobits1]

Dear Friend
Why not used servo mortor
I think it's easy because include gear box
http://www.embeddedtronics.com/servo.html

I live in algeria, and since it is a poor there is less of electronics component, i barely can find the pic16f877, i also will use motors from broken printer, the situation sucks here & i dont have much of choice.

sorry for my situation , but i will try to adapt any advice you gave me and work.

about the servo motor, since it is not possible to buy one than i think of making one with stepper motor (or something like servo motor ), or i will try the differential drive but i am not sure because i think the weight is too heavy and the  differential drive not suitable for cases like this.

[Elkeran]

You can find a lot of components like small DC servo motors (with incremental optical encoder), stepper motors, and infrared sensors and many more in old photocopier scarp

[bliviudaniel]

Hello again shobits1.

I may suggest you to find on google about "sumo robot". These are 20cm x 20cm and maximum 3kg robots. You should not be afraid that your robot is to large&heavy Almost all are built with differential drive. Unfortunately, I have never built such robot with such dimensions.
By the way, search on google about line follower contests and you will see that in the majority of contests, the circuit/track contains 90 degrees curves. For exemple here:

http://www.robotgames.net/robotgames/Event_Rules/2002_line_follower.htm

I think it's imposibile to complete these kind of circuits without have the possibility to turn 90 degrees... I think all line follower robots use differential drive.

I have another 2 small advices for you.
If you have possibility, search for some fast motors. The line follower contest are basically based on 2 rules:the robot should complete the circuit and the winner is the robot which is the fastest one.
In addition to printers, you can find good geared dc motors in video players or in casette players. Or you may try the mechanism which opens the cdrom if you have some cdroms for "hacking".

Bon chance!


Posted on: February 04, 2008, 09:22:05 09:22 - Automerged
Sorry if I insist with dc motors, but they are far easily to vontrol than steppers. But if you have steppers, use steppers.

[shobits1]

thanks again 'bliviudaniel',

i will go along with your advices seems pretty helpful