CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

Intro

The main aim of this project was to "build a PID controller and tune the PID hyperparameters by applying the general processing flow as explained in the lessons," and to "test the solution on our simulator!" The simulator provides cross-track error (CTE), speed, and steering angle data via local websocket. The PID (proportional/integral/differential) controller must respond with steering and throttle commands to drive the car reliably around the simulator track.

Effect each of the P, I, D components had in the implementation

The P, or "proportional", component had the most directly observable effect on the car's behavior. It causes the car to steer proportional (and opposite) to the car's distance from the lane center (which is the CTE) - if the car is far to the right it steers hard to the left, if it's slightly to the left it steers slightly to the right.

The D, or "differential", component counteracts the P component's tendency to ring and overshoot the center line. A properly tuned D parameter will cause the car to approach the center line smoothly without ringing.

The I, or "integral", component counteracts a bias in the CTE which prevents the P-D controller from reaching the center line. This bias can take several forms, such as a steering drift (as in the Control unit lessons), but I believe that in this particular implementation the I component particularly serves to reduce the CTE around curves.

Video of final implementation with appopriate params of P, I, D components:

Video of I component removed:

Notice that the center line is not followed as closely around curves.

Video of D component removed:

It begins to ring back and forth across the center line until finally leaving the track.

How the final hyperparameters (P, I, D coefficients) were chosen

The controller was initially tuned with Ziegler–Nichols method (http://chem.engr.utc.edu/Student-files/x2008-Fa/435-Blue/1942-paper.pdf). It requires to set Kd & Ki to 0 and gradually increase Kp before the car runs with stable & consistent oscillations. But the controller with the resulted paramteres was able to drive car around the track with a lot of wobbling. Later the parameters were further tuned manually by trial-and-error process.

By applying the same process for different speeds, results were linearized in order to make parameters automatically tune with the car speed variation.

Dependencies

cmake >= 3.5
All OSes: click here for installation instructions
make >= 4.1(mac, linux), 3.81(Windows)
- Linux: make is installed by default on most Linux distros
- Mac: install Xcode command line tools to get make
- Windows: Click here for installation instructions
gcc/g++ >= 5.4
- Linux: gcc / g++ is installed by default on most Linux distros
- Mac: same deal as make - [install Xcode command line tools]((https://developer.apple.com/xcode/features/)
- Windows: recommend using MinGW
uWebSockets
- Run either ./install-mac.sh or ./install-ubuntu.sh.
- If you install from source, checkout to commit e94b6e1, i.e.
```
git clone https://github.com/uWebSockets/uWebSockets 
cd uWebSockets
git checkout e94b6e1
```
  Some function signatures have changed in v0.14.x. See this PR for more details.
Simulator. You can download these from the project intro page in the classroom.

There's an experimental patch for windows in this PR

Basic Build Instructions

Clone this repo.
Make a build directory: mkdir build && cd build
Compile: cmake .. && make
Run it: ./pid.

Tips for setting up your environment can be found here

Editor Settings

We've purposefully kept editor configuration files out of this repo in order to keep it as simple and environment agnostic as possible. However, we recommend using the following settings:

indent using spaces
set tab width to 2 spaces (keeps the matrices in source code aligned)

Code Style

Please (do your best to) stick to Google's C++ style guide.

Project Instructions and Rubric

Note: regardless of the changes you make, your project must be buildable using cmake and make!

More information is only accessible by people who are already enrolled in Term 2 of CarND. If you are enrolled, see the project page for instructions and the project rubric.

Hints!

You don't have to follow this directory structure, but if you do, your work will span all of the .cpp files here. Keep an eye out for TODOs.

Call for IDE Profiles Pull Requests

Help your fellow students!

We decided to create Makefiles with cmake to keep this project as platform agnostic as possible. Similarly, we omitted IDE profiles in order to we ensure that students don't feel pressured to use one IDE or another.

However! I'd love to help people get up and running with their IDEs of choice. If you've created a profile for an IDE that you think other students would appreciate, we'd love to have you add the requisite profile files and instructions to ide_profiles/. For example if you wanted to add a VS Code profile, you'd add:

/ide_profiles/vscode/.vscode
/ide_profiles/vscode/README.md

The README should explain what the profile does, how to take advantage of it, and how to install it.

Frankly, I've never been involved in a project with multiple IDE profiles before. I believe the best way to handle this would be to keep them out of the repo root to avoid clutter. My expectation is that most profiles will include instructions to copy files to a new location to get picked up by the IDE, but that's just a guess.

One last note here: regardless of the IDE used, every submitted project must still be compilable with cmake and make./

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vivekchand / CarND-PID-Control-Project