Steven Reubenstone
· New YorkU.S.
Open

# Task 4 (in progress): Coding the sketch – We Need Help Here!

(CURRENT FOCUS HERE: Tuning the PID gain coefficients using MATLAB)

Contributions
Darpan Pudasaini

Great insight and knowledge on PID Controllers for DC Motors. Darpan explained some of the inner workings in the code in this thread.

Control Systems

Faiz Ur Rehman

Faiz successfully constructed the first set of signal tuning for our PID Control System for our car drone. He successfully showed knowledge of Control Systems and leveraged Fourier Transforms properly as well in his analysis. He was also able to show great knowledge of replicating real signal noise in system design by adding a Gaussian Noise signal to our control simulation.

Pedro Cunha

Genius contribution and insight by Pedro. He related my pid controlled “line stabilization car” to a shopping cart being pushed in a super market. That’s dead on!!! What a mind!

7 likes
Like
Pedro Cunha
Mechanical and Aeronautical Engineer
· Rio de JaneiroBrasil

Hello guys… This project is very cool!! I am more than happy to help!
I did not read all the comments yet, I am still familiarizing myself with the project so dont mind if I make some outdated observations! : )

1. I couldnt find if the thrusters are pushing or pulling the car… I mean, the propellers are the front or the back of the vehicle?
In my opinion the thrust must pull the vehicle… that is, the propellers must be the front of the car. This configuration will be inherently stable!

2. Darpan Pudasaini I dont know if I am missing something, but I think you switched the motors in your example.

Lets take a scenario here. Our car is moving in a straight line and then suddenly drifts towards right a little. The motorSpeed will now get a value of -10 (say). We have predifned values for leftMotorSpeed and rightMotorSpeed as 100 rpm (say) . In this case, the value of motorSpeed = -10 will change the roght and left values as :

RightMotorSpeed = 100 -10 = 90 rpm
LeftMotorSpeed = 100 - (-10) = 110 rpm

So, the car will now drift more towards left and hence keep the car in a straight line.

To move left, we need to increase the right motor and decrease the left motor in order to generate the torque to the left and vice-versa.
So, if the right drift results in a negative motorSpeed, we need to change the + and - signals in RightMotor and LeftMotor equation.

You are doing a very good job!!

1 like
Steven Reubenstone
· New YorkU.S.

Yes Pedro, this is the basic gist of the project. It is being completed specifically so we can all introduce ourselves to the concepts of signal filtering and PID Control, something I loved doing in M.E. school but have a desperate need to polish up on.

Regarding the fans…yes it is not the perfect design. Why is fans in front more stable?

Steven Reubenstone
· New YorkU.S.

Faiz Ur Rehman

any progress with filter? i’d like to get that out of the way so we can get into pid tuning

Pedro Cunha
Mechanical and Aeronautical Engineer
· Rio de JaneiroBrasil

Steven, I like to think this as when you are driving those shopping carts, trolleys in the supermarket. You see that if you start to walk forward, in a straight line, driving them in the usual way (pushing them), the slightest disturbance creates a deviation in the path that demands a fast and strong response (sometimes quite complex response… several actions) in order to correct the shopping cart path and put it back stable in the straight line forward movement.

Driving like this with only one hand shows how hard it is.
If you try the same path, but now you are in front of the cart, pulling it, you will notice that is much easier to maintain the straight line path. You see that, in this last situation, you are even able to drive the shopping cart pulling it with only one hand without big problems.

2 likes
Student