/sdc-term2-p4-pid-controller

Implements a PID controller in C++ to maneuver the vehicle around the simulators track. The simulator provides the cross track error (CTE) and the velocity (mph) in order to compute the appropriate steering angle.

Primary LanguageC++

Reflection

PID Terms

tau-p (aka Kp in the code base) is the steering equations Proportional term which describes how hard you want to steer back to the centre of the road (x-axis).

tau-i (aka Ki in the code base) is the steering equations Integral term which describes how much the wheels are out of alignment.

tau-d (aka Kd in the code base) is the steering equations Derivative term which describes how much smoothing is to be applied to the steering turn-back correction in order to place the car in the centre of the road (x-axis).

PID Cross Track Errors (CTE)

d_error is the Differential error which stores how much this error changed since our last CTE recording.

p_error is the Proportional error which stores how far we are off the centre of the road, which is where we want to track to.

i_error is the Integral error which is the cumulative sum of all of our CTEs.

Steering Equation

The steering value is calculated with this PID equation from Term2.Lesson16.Video11.

steer_value = (-pid.Kp * cte) - (pid.Kd * pid.d_error) - (pid.Ki * pid.i_error);

Manually Tuned Hyper Parameters

Through trial-and-error, I arrived at these values that successfully resulted in the car driving the simulated track.

double init_Kp = 0.3;
double init_Ki = 0.000228;
double init_Kd = 0.000255;

Result

  1. Jerky steering but car remains on the track.
  2. Quick to implement.
  3. Computationally inexpensive.

CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

Dependencies

Basic Build Instructions

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