Self-Driving Car Engineer Nanodegree Program

• 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

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

1. First, I used PID::Init() function to initialize the Kp, Ki, Kd coefficients.
2. Then, I calculated the error by PID::UpdateError function for each cte input.
3. Finally, I calculate the steering_angle by PID::GetSteerValue function and return to the simulator.

P: P coefficient controls the vehicle to drive to the road center. For examples, it controls the turning angle of the vehicle while the vehicle is turning. When P coefficient is large, it can be turning quickly in curved road, However, in the straight road, it leads the vehicle oscillates faster. D: In order to reduce the vehicle oscillates, D coefficient is introduced. D coefficient can be effectively reduce the vehicle oscillates. I: Besides, if the vehicle has systemcatic bias, we need use the I coefficient. I coefficient can be used to reduce impact of the vehicle systemcatic bias. But it also should not be too large, it will leads the vehicle oscillates too.

I have chosen the P, I, D coefficients by manual tuning. First, I used the classroom PID project params as beginning: 0.2, 0.004, 3.0. Then, I started the program, but I found the car is oscillates seriously. In the expriments, I find the P coefficients cannot be reduce, it will lead to the car cannot pass the curved road, so I decrease the I coefficient to 0.005. Finally, in order to make the car more stable, I increase the D coefficient to 5.0.