xjtuyanshi / carnd-pid-control-project

CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

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Implementations

1. Rewrite python code from classroom to C++.:)
   • Init() initialize P, I, D parameters (PID.cpp line 14-25)
   • UpdateError(), based on PID error calculation formula, get error for each parameters(PID.cpp line 27-35)
   • GetSteerValue(), output steer values (PID.cpp line 46-58)
2. Manual PID parameters turning
   • Adjust values by modify P, all others to 0; then P,I; then PID.
   • it looks like P= .2, I = 1e-4, D = 3.0 let the car finish the full lap
3. Using Twiddle Algorithm to Tune PID Paramters
   • I imitated the python code algorithm and rewrite it in C++
   • Added a few conditions to make it better works in the simulation enviroment
   • if cte > 5 , which means the car is out of lane, should rerun simulation
   • if time steps (no of h messages) > 8000 ( about one lap), restart simulation for another iteration
   • However, it seems my implementation doesn't work well. first of all, it takes much longer time to run more iterations in simulator.
   • Besides, PID values are not moving in the right directions and stay at a range then do not change anymore.
   • Due to limited time, I am not be able to figure out the reason and will revisit this after finishing the final project.

Below is a short GIF shows the animation after using manual tuned PID parameters.

Below is a short GIF shows the animation after using twiddle for 14 iterations(Failed).

Reflections

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

1. P (proportional) tries to stter car to the center to minimize cte. However, it easily make the car overshot center of lane and could run out of lane.
2. I(Intergral) treis to reduce the bias of car control system (like steering drift) accumulated over time. In the simulator, it seems there is no bias.
3. D(Differential) helps reduce the effect of overshoot created by P, so the car's steering will not oscillate much when only P is added.

Project 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.

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