CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

`PID Class`

The PID controller is implemented by a PID Class, which needs to be specified the P, I, D coefficients:

Kp - proportional coefficient
Ki - integral coefficient
Kd - differential coefficient

I use the method CalculateSteering to calculates steer by given cte , i don't use the speed value.

  // initialize variables
   double steering, D_cte;
   cte_int = cte_int + cte;
   D_cte = cte - cte_old;
   cte_old = cte;
   // Calculate steering angle
   steering = Kp * cte + Ki * cte_int + Kd * D_cte;
   // return the steering angle
   return steering;

P, I, D Tuning

Those three parameters were tuned manually by trial and error based on the following principles.

Kp cannot be too high to avoid overshooting and oscillation.
Kd is to consider the rate of change of error, which slows down the proportional control but overcomes the overshooting and oscillation issues.
Ki is to consider the accumulated error to fix the systematic bias, which should be a small value.

Keeping those in mind, the three parameters are chosen after some trial and error:

double Kp_steer = -0.05;
double Ki_steer = 0.0;
double Kd_steer = -5.0;

By using the above parameters, the PID controller can drive the car and finish the track. Although the car still has some oscillations, but it does not run off the road.

the fellowing img is my turning pictuer

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./

How to write a README

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allamtb / CarND-PID-Control-Project