CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

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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.

Fellow students have put together a guide to Windows set-up for the project here if the environment you have set up for the Sensor Fusion projects does not work for this project. There's also an experimental patch for windows in this PR.

Basic Build Instructions

1. Clone this repo.
2. Make a build directory: mkdir build && cd build
3. Compile: cmake .. && make
4. 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./

How to write a README

A well written README file can enhance your project and portfolio. Develop your abilities to create professional README files by completing this free course.

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Write Up

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Describe the effect each of the P, I, D components had in your implementation.

The code changes have been made to two files: "PID.cpp" and "main.cpp". The implementation of "PID.cpp" was straigtforward based on what I have leared from lectures. The modifications to "main.cpp" included two PID controllers: pid_steering and pid_throttle. There are two code sections to control whether to enable pid_throttle or not: line 33-40. With tuned P, I, D coefficients, vehicle could finish one loop around the track with only pid_steering, and with pid_throttle enabled as well. A video file "PID_Control.mp4" has been uploaded to the project folder to demonstrate the test run of a full loop.

Based on my tuning experience, P coefficent controls how fast vehicle go back to the target state, D coefficient reduces the offset to the target state, and I coefficient corrects the accumulated skew in the system.

Describe how the final hyperparameters were chosen.

I've manually tuned the hyperparameters (i.e., P, I, D coefficients). Initially, I picked some values for P coefficient to tune while setting I and D coefficients to be zero. After the vehicle could run for some decent distances with some overshooting effects, I started tuning I coefficient, and found out that it was very sensitive and could not make vehicle stable. I had to tune D coefficient together with I coefficent to get stabalized runs. The final parameter values I obtained for Steering PID are:

  pid_steering.Init(0.12, 0.0005, 3.5);

Similarly, I've added the Throttle PID control, and performed similar manual tunings, with the following final parameter values:

  pid_throttle.Init(0.32, 0.0005, 6.5);