CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

Writeup

I followed the video of PID project Q&A session and give the main function three input arguments to represent the initial value of Kp, Ki and Kd. This helps me save a bunch of time tweaking the parameters by skipping the build process.

I started with [0.5,0,0.5] for PID gains, as suggested in the video, and observed the resulting behavior. Found that the vehicle oscillated too much when making the first turn. Since the P component controls how strong in proportion to the CTE we control the steering of our vehicle so I changed it to 0.1 but it didn't help that much. Realizing that the behavior of a P controller may never be good, I decided to manipulate the D gain and set this to 1.5 to see if it would improve things. The D component does a good job stopping strong oscillations by making the steering dependent also on the temporal derivative of the CTE. It helps the car successfully pass the first turn. However, the car started oscillating after the first turn and it made the second and third turn very dangerous.

Adding an I term makes the steering proportional to the sum of all CTEs. This helps to adjust to a bias our vehicle might have in regard to steering so I changed it a very small number since I believe the effect of bias is quite minor because the car drives very smooth at the beginning.

I finally pick [0.09 0.00001 1.2] as the parameters after tweaking them for some time. I know this is not perfect but I will try implementing Twiddle on the next commit.

Dependencies

cmake >= 3.5
All OSes: click here for installation instructions
make >= 4.1
- 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.

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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hellozeyu/CarND-PID-Control-Project